U.S. patent application number 11/335397 was filed with the patent office on 2006-12-21 for sensor apparatus.
Invention is credited to Peter C. Cowan, Colin N. Gunn, Martin A. Hancock, Stewart J. Harding, Marc A. Ricci.
Application Number | 20060284647 11/335397 |
Document ID | / |
Family ID | 36572426 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060284647 |
Kind Code |
A1 |
Gunn; Colin N. ; et
al. |
December 21, 2006 |
Sensor apparatus
Abstract
A sensor apparatus for measuring power parameters on a power
conductor, such as a high voltage transmission line may include a
corona structure, an electronics assembly and a conductor mountable
device. The corona structure may define an outer boundary
surrounding the electronics assembly and the conductor mountable
device. The corona structure may shield the electronic assembly and
conductor mountable device from a corona produceable with the power
conductor. The conductor mountable device may be a power parameter
measurement device, such as a current sensor assembly. The current
sensor assembly may be a split-core design that includes multiple
transformer cores. The electronics assembly and the conductor
mountable device may powered from a line voltage suppliable on the
power conductor. Data may be wirelessly transmitted and received
with the sensor apparatus.
Inventors: |
Gunn; Colin N.; (Victoria,
CA) ; Harding; Stewart J.; (Victoria, CA) ;
Ricci; Marc A.; (Victoria, CA) ; Cowan; Peter C.;
(Victoria, CA) ; Hancock; Martin A.; (Victoria,
CA) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE/PML;INDIANAPOLIS OFFICE
1 INDIANA SQ
SUITE 1600
INDIANAPOLIS
IN
46204-2033
US
|
Family ID: |
36572426 |
Appl. No.: |
11/335397 |
Filed: |
January 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60645317 |
Jan 19, 2005 |
|
|
|
Current U.S.
Class: |
324/126 |
Current CPC
Class: |
G01R 15/183 20130101;
G01R 1/18 20130101; G01R 15/186 20130101; G01R 1/22 20130101 |
Class at
Publication: |
324/771 |
International
Class: |
G01R 31/36 20060101
G01R031/36 |
Claims
1. A sensor apparatus that is mountable on a power conductor, the
sensor apparatus comprising: a conductor mountable device; a corona
structure that is electrically conductive and formed to define an
outer boundary surrounding said conductor mountable measurement
device, said corona structure also formed to define an inner volume
that accommodates said conductor mountable device, wherein a
portion of a power conductor is disposable in said inner volume; a
guide brace structure coupled with said corona structure, said
guide brace structure operative to maintain said corona structure
in a predetermined position relative to said conductor mountable
device; and a power supply coupled between said power conductor and
said corona structure, wherein said power supply is operative to
develop power to power said conductor mounted device as a function
of a difference in potential between said power conductor and said
corona structure.
2. The sensor apparatus of claim 1, wherein the conductor mountable
device is a power parameter measurement device.
3. The sensor apparatus of claim 1, wherein said difference in
potential is based on a free body capacitance of said corona
structure that is chargeable and dischargeable with a line voltage
suppliable on said power conductor.
4. The sensor apparatus of claim 1, wherein said corona structure
and said guide brace structure form a continuous open framework of
members configured to define apertures therebetween.
5. The sensor apparatus of claim 1, wherein said guide brace
structure is operative to guide said conductor mountable device
into a predetermined position to surround at least a part of said
portion of said power conductor disposable within said inner
volume.
6. The sensor apparatus of claim 1, wherein said corona frame
structure comprises: a first corona frame structure disposed in a
first plane; and a second corona frame structure disposed in a
second plane; wherein said first plane and said second plane are
positionable on opposed sides of said conductor mountable
device.
7. The sensor apparatus of claim 1, further comprising a coupling
device coupled with said guide brace structure, wherein said
coupling device is constructed of conductive material and is
operative to be selectively coupled with said portion of said power
conductor.
8. The sensor apparatus of claim 7, wherein said coupling device is
a clamp that is operative to be opened and closed remotely from a
distance away from said clamp.
9. The sensor apparatus of claim 1, wherein said guide brace
structure is configured to be maneuverable with a hot stick into
contact with a power conductor.
10. The sensor apparatus of claim 1, further comprising an
electronic assembly operative with said conductor mountable device,
wherein said guide brace structure is formed to be fixedly coupled
with said electronic assembly such that said electronic assembly is
disposed in said inner volume.
11. The sensor apparatus of claim 1, wherein said guide brace
structure includes a conductor guide portion that is formed to
guide a power conductor placeable in contact with said conductor
guide portion into a predetermined alignment with said conductor
mountable device.
12. The sensor apparatus of claim 1, wherein said corona structure
comprises a tubular frame.
13. The sensor apparatus of claim 6, wherein said first corona
frame structure, said second corona frame structure, and said guide
brace structure are formed to provide a corona discharge capability
that is unaffected by a size or shape of devices included within
said inner volume.
14. The sensor apparatus of claim 1, wherein said corona structure,
said conductor mountable device, said guide brace structure and
said power supply are operative with a power conductor that is a
high voltage power line operative in a voltage range from about 38
kV to about 765 kV.
15. The sensor apparatus of claim 6, wherein said first corona
frame structure and said second corona frame structure are each
formed in a closed curve.
16. The sensor apparatus of claim 1, wherein said corona structure
includes one or more members shaped to form a surface radius of
curvature with corona shielding effects.
17. A sensor apparatus that is mountable on a power conductor, the
sensor apparatus comprising: an open corona frame that is
positionable with respect to a power conductor so that said open
corona frame is operative to define a volume of space where an
electric field potential of a line voltage applicable to said power
conductor is reduced to non-ionizing levels; an insulator coupled
with said corona frame, wherein said insulator electrically
isolates at least a portion of said corona frame from said line
voltage; and a power transforming apparatus operative to receive a
primary voltage that is developed between said line voltage and
said open corona frame and generate a secondary voltage that is
less than said primary voltage, said secondary voltage suppliable
to said sensor apparatus.
18. The sensor apparatus of claim 17, further comprising a coupling
mechanism that is operative remotely to couple said open corona
frame to said power conductor.
19. The sensor apparatus of claim 17, wherein said primary voltage
is developed from a difference in a potential of said line voltage
and a effective body capacitance charge of said open corona
frame.
20. The sensor apparatus of claim 17, further comprising a power
parameter measurement device disposed in said volume of space,
wherein said power transforming apparatus is operative to supply
said secondary voltage to said power parameter measurement
device.
21. The sensor apparatus of claim 17, further comprising a power
parameter measurement device disposed in said volume of space,
wherein said power transforming apparatus is operative to provide
one of an AC or DC supply voltage that is suppliable to power said
power parameter measurement device.
22. The sensor apparatus of claim 17, wherein said open corona
frame is constructed of electrically non conductive material
covered with a conductive coating.
23. The sensor apparatus of claim 17, wherein said open corona
frame is formed with a plurality of non-continuous members, at
least some of said non-continuous members having gaps
therebetween.
24. The sensor apparatus of claim 17, wherein said open corona
frame comprises a guide brace structure operative to align said
power conductor within said volume of space.
25. A sensor apparatus that is mountable on a power conductor, said
sensor apparatus comprising: a first frame member longitudinally
extending in a predetermined shape to form a first closed curve; a
plurality of guide braces each having a first end and a second end,
wherein said first end of said guide braces are coupled to said
first frame member; and a second frame member coupled to said
second end of said guide braces, wherein said second frame member
longitudinally extends in a predetermined shape to form a second
closed curve that is fixedly held in a position spaced away from
said first frame member by said guide braces; wherein said
plurality of guide braces are operative to guide said power
conductor into a predetermined alignment with said sensor
apparatus.
26. The sensor apparatus of claim 25, wherein said first frame
member lies in a first plane and said second frame member lies in a
second plane that is substantially parallel with said first
plane.
27. The sensor apparatus of claim 25, wherein each of said first
frame member and said second frame member are further formed to
define a respective inner volume.
28. The sensor apparatus of claim 25, wherein said first frame
member and said second frame member each comprise a tubular
member.
29. A sensor apparatus mountable on a power conductor, the sensor
apparatus comprising: a current sensor assembly operative to sense
current in a power conductor; and an electronics assembly coupled
with said current sensor assembly; wherein said current sensor
assembly comprises a housing with a plurality of transformer cores
and a carrier disposed therein, wherein said carrier is operative
to support said transformer cores in at least one dimension, and is
operative to be moveable with respect to said housing; and wherein
said electronics assembly comprises communication means for
communicating with external devices and a power supply operative to
supply power to said current sensor assembly, said power derivable
from a voltage and a current suppliable on said power
conductor.
30. The sensor apparatus of claim 29, further comprising an open
corona shield structure coupled to said electronics assembly and
said current sensor assembly, wherein said open corona shield
structure is cooperatively operative with said power supply to
power said current sensor assembly and said electronics assembly as
a function of a voltage and a current suppliable on said power
conductor.
31. The sensor apparatus of claim 29, wherein said electronics
assembly is at least partially enclosed in a weatherproof and
electro-magnetically shielded electronics housing.
32. The sensor apparatus of claim 31, wherein said housing
comprises a multi-contact electrical connector, said multi-contact
electrical connector operative to couple said current sensor
assembly with at least one of said electronic devices.
33. The sensor apparatus of claim 31, wherein said housing further
comprising a radio frequency antenna operative to provide a low
voltage standing wave ratio interface and further operative to be
interfaced to externally located telemetry and a global positioning
system antenna operative to be interfaced with a satellite.
34. The sensor apparatus of claim 31, further comprising a
telemetry antenna mounted on said weatherproof and
electro-magnetically shielded electronics housing.
35. The sensor apparatus of claim 29, wherein said sensor apparatus
is configured to be coupled with a hot stick and is mountable on
said power conductor with said hot stick.
36. The sensor apparatus of claim 29, wherein said communication
means comprises an antenna.
37. The sensor apparatus of claim 36, wherein said antenna
comprises a satellite antenna operative to at least one of transmit
data or receive at least one of time and geographic position data,
or combinations thereof.
38. The sensor apparatus of claim 37, wherein said electronics
assembly includes a global positioning system coupled to said
satellite antenna.
39. The sensor apparatus of claim 29, wherein said communication
means comprises a shielded and weatherproof cable connected between
said electronics assembly and said current sensor assembly.
40. The sensor apparatus of claim 29, wherein said communication
means is operative to enable wireless communication between said
electronics assembly and said current sensor assembly.
41. The sensor apparatus of claim 29, wherein said communication
means is operative to enable communication between said current
sensor assembly and a ground based processor that is external to
said sensor apparatus.
42. The sensor apparatus of claim 29, wherein said communication
means is operative to enable radio frequency communication.
43. The sensor apparatus of claim 29, wherein said electronics
assembly further comprises a processor and a memory.
44. The sensor apparatus of claim 29, further comprising a corona
frame structure coupled with said electronics assembly and said
current sensor assembly wherein said corona frame structure is at
least one electrically conductive member that defines an outer
boundary of said sensor apparatus, and defines an inner volume
formed to accommodate said current sensor assembly, said
electronics assembly and a portion of said power conductor.
45. The sensor apparatus of claim 29, further comprising a brace
structure coupled with said electronics assembly, said current
sensor assembly, and a corona frame structure, said brace structure
coupled with and operative to maintain said corona frame structure
in a predetermined position relative to said electronics assembly
and said current sensor assembly to provide shielding from a corona
dischargeable as a function of power on said power conductor.
46. The sensor apparatus of claim 45, wherein said brace structure
is operative to guide said current sensor assembly into a
predetermined position to surround at least a portion of said power
conductor.
47. The sensor apparatus of claim 29, wherein said power supply
comprises a transformer that includes a primary winding and a
secondary winding, wherein said power conductor is electrically
coupled with said primary winding, and said secondary winding is
operative to supply power to said current sensor assembly and said
electronics assembly.
48. The sensor apparatus of claim 29, further comprising a brace
structure, wherein said electronics assembly is coupled with one of
said brace structure and said current sensor assembly.
49. The sensor apparatus of claim 45, wherein said corona frame
structure, said brace structure, and said electronics assembly are
arranged to be self aligning in a determined position with respect
to said power conductor.
Description
[0001] This application claims the benefit pursuant to 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application Ser. No.
60/645,317 filed on Jan. 19, 2005, which is herein incorporated by
reference in its entirety.
BACKGROUND
[0002] Instrument transformers for installation on high voltage
transmission lines, which may include those transformers used for
protective relay and metering, are large and expensive. This is
especially true for instrument transformers designed for
applications involving high transmission line voltages. It is also
very costly to replace instrument transformers due to the necessity
to power down the transmission line during the replacement. One
type of instrument transformers are referred to as current
transformers (CTs). CTs may be used to measure a flow of
current.
[0003] Current transformer reclassification is the process of
taking an existing current transformer (CT) and recalibrating it,
using calibration constants. The calibration constants may be used
to modify the current measurements performed by the CT to improve
the accuracy of the measured current sensor
[0004] A current transformer reclassification ("sensor") apparatus
may be used to aid in the reclassification of an existing installed
CT. In addition, a sensor apparatus may be used to verify end to
end system accuracy of CT measurement points in a substation,
switchyard, or other location. A sensor apparatus can also be
utilized to verify the accuracy and/or operability of new equipment
coupled with a transmission line. Currently, meters and instrument
transformers are calibrated independently in a lab before being
installed as a complete system in the field. However, once
installed in the field there is no simple or cost effective way to
verify the entire system's accuracy.
SUMMARY
[0005] The invention relates to a system, apparatus and method for
measuring power parameters on a power line. More particularly, the
disclosed embodiments relate to a mechanical design and a system
operable to be installed and monitor power parameters on a power
line, such as a high voltage power line. The system may also
include mechanisms to enable compensation for inaccuracies in the
output of instrument transformers. The disclosed embodiments
include a sensor apparatus that is accurate, self contained, easy
to install, and easy to use.
[0006] The disclosed sensor apparatus may include a corona frame
and a conductor mountable device. The corona frame may be an open
structure that provides an outer envelope and an inner volume in
which corona discharge may be minimized. The conductor mounted
device may be a power parameter measurement device that is a
current sensor assembly. The current sensor assembly may be a split
core design that includes a housing that can contain operating
logic and electronic devices, such as a power supply and
compensation circuitry. The current sensor assembly may also
include a mechanism to transition a first housing assembly and a
second housing assembly that form the housing between an open
position and a closed position.
[0007] The current sensor assembly may also include a carrier. The
carrier may be disposed in the housing and contain a plurality of
current transformer cores. In a split core design, the discrete
portions of the carrier may be included in both the first housing
assembly and the second housing assembly, and contain discrete
portions of the current transformer cores. The carrier, current
transformer cores and corresponding current transformer windings
may form a winding assembly. Discrete portions of the winding
assembly may be included in each of the first and second housing
assemblies. The carrier and winding assembly may be moveable within
the respective housing assemblies to enable contiguous alignment of
the discrete core portions when the current sensor assembly is
placed a closed position.
[0008] The sensor apparatus may also include a global positioning
system (GPS) and/or time-syncing capabilities to allow end to end
accuracy verification of the instrument transformers in a power
system. In addition, the sensor apparatus may include an antenna(s)
providing telemetry data and/or receiving GPS timing/position data
to enable communication with, and use of, the installed sensor
apparatus. The sensor apparatus may also include one or more
coupling devices. The coupling devices may be insulated from the
corona frame of the sensor apparatus. Further, the sensor apparatus
may include environmental protective features to extend the service
life of the sensor apparatus. The sensor apparatus may also include
a post installation auto-positioning feature using weight
distribution, and an installation guide frame, all of which may
provide for easier installation and the ability to install the
sensor apparatus on a live power line without having to first
interrupt and/or de-energize the line.
[0009] Some embodiments of the sensor apparatus may feature an open
corona frame or open corona structure. The open corona frame may
allow for modularity in the design, by allowing the addition of
components without requiring that those additional components
feature a smooth exterior or larger bend radius as is typically
required by corona discharge reduction practices. The open frame
also enables RF communication with the sensor apparatus and enables
capacitive body electric field powering of the sensor apparatus
rather than powering the sensor apparatus directly from the
magnetic field of a power line or from an energy storage device
such as a battery. The open corona frame may include one or more
members that are formed as closed curves to minimize weight and
wind resistance when the sensor apparatus is operational.
[0010] Other systems, methods, features and advantages of the
invention will be, or will become, apparent to one with skill in
the art upon examination of the following figures and detailed
description. It is intended that all such additional systems,
methods, features and advantages be included within this
description, be within the scope of the invention, and be protected
by the following claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention can be better understood with reference to the
following drawings and description. The components in the figures
are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention.
[0012] FIG. 1 illustrates one embodiment of a sensor apparatus
installed on a power conductor.
[0013] FIG. 2 illustrates a perspective view of the power conductor
and an embodiment of the sensor apparatus of FIG. 1.
[0014] FIG. 3 illustrates a side view of the power conductor and
the sensor apparatus of FIG. 2.
[0015] FIG. 4 illustrates the power conductor and a back view of
the sensor apparatus of FIG. 2.
[0016] FIG. 5 illustrates the power conductor and a bottom view of
the sensor apparatus of FIG. 2.
[0017] FIG. 6 illustrates a power conductor and a perspective view
of another embodiment of the sensor apparatus of FIG. 1.
[0018] FIG. 7 illustrates a power conductor and a perspective view
of yet another embodiment of the sensor apparatus of FIG. 1.
[0019] FIG. 8 illustrates a hot stick and an embodiment of a
current sensor assembly that can be included in the current
apparatus of FIGS. 1-7. The current sensor assembly is depicted in
an open position.
[0020] FIG. 9 illustrates a hot stick and an embodiment of the
current sensor assembly of FIG. 8 in a closed position.
[0021] FIG. 10 illustrates an embodiment of the current sensor
assembly of FIG. 8 in a closed position with the hot stick fully
clamped.
[0022] FIG. 11 illustrates an embodiment of the current sensor
assembly of FIG. 8 with a portion of the housings removed.
[0023] FIG. 12 illustrates an embodiment of the current sensor
assembly of FIG. 8 with a portion of the current sensor assembly
removed.
[0024] FIG. 13 is a side view of an embodiment of the current
sensor assembly of FIG. 8.
[0025] FIG. 14 illustrates a partial cross-section of an embodiment
of the current sensor assembly of FIG. 13.
[0026] FIG. 15 illustrates a partial cross-section of another
embodiment of the current sensor assembly of FIG. 13.
DETAILED DESCRIPTION
[0027] FIG. 1 illustrates a sensor apparatus 300, or sensor
structure installed on a power conductor 119. The power conductor
119 may be a high voltage transmission line or any other form of
power supply line or power supply mechanism capable of conducting a
line voltage and a line current. In one application, the sensor
apparatus 300 may be designed for high voltage (HV) substation
installation, such as with voltage levels from 38 kV to 765 kV. In
other applications, the sensor apparatus 300 may be designed for
any other voltage level and/or any other installation location.
Example installation locations include transmission lines,
conductors, generator terminals, switchgear, motor terminals, a
bus, a bus duct, a bus tube, a switch yard, and/or any other
location where power flows through a power conductor 119. It will
be appreciated that particular performance characteristics of the
sensor apparatus 300 may be implemented dependent upon the
particular application in which the sensor apparatus 300 is to be
deployed.
[0028] During installation, the sensor apparatus 300 may be placed
onto the power conductor 119 while the power conductor 119 is
"live," using one or more hot sticks 118. The hot sticks 118 may be
any form of longitudinally extending non-conducting rod having a
proximate end configured to be handled by a user, and a distal end
configured to interface with a device, such as the sensor apparatus
300. The hot sticks 118 may permit the manual installation of the
sensor apparatus 300 while a user of the hot stick 118 may be
positioned remote from the sensor apparatus 300. Thus a user
performing such an installation may be spaced away not only from
the sensor apparatus 300, but also from line voltage and line
current that may be present on the power conductor 119.
Accordingly, the sensor 300 may be installed without deactivation
of the voltage and current flow through the power conductor
119.
[0029] FIG. 2 is a perspective view of an example of an example
sensor apparatus 300. The sensor apparatus 300 may be coupled with
the power conductor 119 with one or more coupling devices 103, such
as a clamp, or any other fastener mechanism that maintains the
sensor 300 in a desired position with respect to the power
conductor 119. In addition, the sensor apparatus 300 may include a
conductor mountable device that couples to the power conductor 119.
The conductor mountable device may be a measurement device, such as
a current sensor assembly, capable of measuring power parameters.
Because the sensor apparatus 300 may be manually lifted onto the
power conductor 119 it may be advantageous for the sensor apparatus
300 to be as light as possible.
[0030] During operation, the sensor apparatus 300 may be located in
an outdoor environment and may be subjected to a wide range of
weather conditions. Thus, the sensor apparatus 300 may be designed
to be protected from weather, temperature, water, corrosion,
oxidation, sunlight and/or any other elements, such as through the
use of sealed connectors, weather tight enclosures, corrosion
resistant materials, and/or any other methods or devices for
environmental protection.
[0031] The sensor apparatus 300 may contain a corona structure 100
formed to reduce the effects of corona discharge. Corona discharges
may form when the intensity of an electric field produced in the
vicinity of a power conductor 119 by a line voltage and line
current thereon exceeds the breakdown strength of air. During such
corona discharges, localized ionization of the air occurs. Radio
interference may be caused and material properties may degrade
where corona discharge occurs. Corona discharge is elevated by
sharp edges on conducting areas of an apparatus where the electric
field gradient is sufficiently high. To reduce corona discharge,
the corner radii of objects employed in high voltage applications
are often smoothed. In addition, objects with sharp edges may be
effectively shielded from corona discharge by surrounding them at
least partially by objects having large radiuses of curvature (for
example corona rings) that may be operated at a potential similar
to the line voltage.
[0032] The sensor apparatus 300 and associated electronics may be
powered indirectly from an electric field generated by the power
conductor 119 utilizing a free body capacitance of the corona
structure 100. The free body capacitance of the corona structure
100 may be charged and discharged as a function of a sinusoidal
waveform of the line voltage. The physical size of the corona
structure 100 may vary since an inverse relationship may exist
between the size of the corona structure 100 and the power
generation for the sensor apparatus 300. For example the electric
field provided by a power conductor 119 carrying a 138 kV
line-to-line voltage may result in the generation of about 3.5
watts of power with a configuration of the sensor apparatus 300.
The same configuration of the sensor apparatus 300, however, may
generate about 7.0 watts of power in a power conductor 119 carrying
a 230 kV line-line voltage. Thus with a fixed power requirement
such as 3.5 watts, as the power conductor 119 line-to-line voltage
measurement increases, the relative size of the corona structure
100 may be decreased.
[0033] There also may be a direct relationship between a magnitude
of voltage on the power conductor 119 and a radius of the corona
structure 100 to enable a desirably reduced corona discharge.
Accordingly, based on these relationships with decreased voltage on
the power conductor 119, there comes a point where the electric
field may no longer meet the power needs of the sensor apparatus
300. An alternate power source, such as a battery, may also be used
to power the sensor apparatus 300. In this situation, the sensor
apparatus 300 might be used without the corona structure 100.
Likewise, as the voltage on the power conductor 119 increases the
corona structure 100 can be reduced in size, but the size reduction
may be limited by the size of radii required. In an alternate
embodiment, the corona structure 100 may be modularly constructed
to adjust the size of corona shield provided by the corona
structure to suit the specific line voltage of the power conductor
119.
[0034] Referring now to FIGS. 2 through 5, in one embodiment the
sensor apparatus 300 comprises the corona structure 100, guide
braces 101, insulators 102, coupling devices 103, an electronics
assembly 110 and a current sensor assembly 120. In other examples,
the electronics assembly 110 may be incorporated into and form a
part of the current sensor assembly 120.
[0035] The corona structure 100 may be a frame that is operable to
serve a plurality of functions. First the corona structure 100 may
be a corona shield that distributes the electric field to minimize
the formation of corona on the overall assembly. In other words,
the electric field potential of a line voltage present on a power
conductor 119 may be reduced to non-ionizing levels within the
corona structure 100. The electric field may be distributed by
presenting a large conductive radius of curvature and shielding the
smaller radius of curvature devices included within an envelop
defined by the corona structure 100. In this embodiment the corona
structure 100 may include one more frame members extending in a
predetermined shape with large radius corners to distribute the
electric field. Second the corona structure 100 may provide enough
free body capacitance to power the sensor apparatus 300. Third the
corona structure 100 may provide locations to mount various
sub-assemblies and components included in the sensor apparatus
300.
[0036] The corona structure 100, or corona shield structure, or
corona frame, may be a one or more continuous open framework
structures formed from one or more members of a conductive
material. Where there are multiple member components,
non-continuous member components may be coupled together to form a
continuous corona structure 100. The continuous corona structure
100 may be an open framework of members that longitudinally extend
to define apertures therebetween. Alternatively, some of the
non-continuous members may be formed with gaps such that the corona
structure is not continuous, but is instead formed in segments with
gaps of a determined length between the segments.
[0037] The one or more members may also be formed as one or more
closed curves, or closed plane curves. As used herein a "closed
curve" is defined as any material or structure formed with one or
more members, no endpoints, and which encloses an area. A "closed
plane curve" is defined as any material or structure formed with
one or more members that resides in a single plane with no
endpoints and which encloses an area.
[0038] In one example, the corona material may be formed as one or
more elongated, hollow, tubular, light weight, weather proof,
conductive members. For example, the corona material may be
aircraft tubing formed with aluminum or some other suitable tubing
formed with conductive material. In other examples, the corona
structure 100 may be formed with one or more members that are solid
materials, and/or materials in any other cross-sectional shapes,
that can be formed as a plane curve, and/or a closed plane curve.
In addition, the corona structure may allow for ease of
installation, provide electrical conductivity and have the ability
to withstand adverse environmental situations. Alternatively the
corona structure 100 may be formed with one or more materials that
are non-conductive materials covered with a conductive coating.
[0039] The corona structure 100 may include one or more corona
frame structures. In the illustrated embodiments the corona
structure 100 comprises two corona frame structures formed with
tubular frames. Each of the corona frame structures may be closed
plane curves that are formed as toroids. In other examples, other
shapes and quantities of corona frame structures are possible. For
example, the corona structure 100 may be a single continuous corona
frame structure formed as a helical coil, a plurality of corona
frame structures forming segments that are spaced away from each
other, or a single closed curve corona frame structure.
[0040] In FIGS. 2-5, the corona frame structures reside in separate
planes on opposite sides of the sensor apparatus 300. In addition,
the corona frame structures may be positioned to be substantially
parallel with respect to each other. In other examples, the corona
frame structures may reside in planes that are non-parallel, or
that may form intersecting planes. In still another example, the
sensor apparatus 300 may include a single corona frame structure,
or three or more corona frame structures.
[0041] During operation, the illustrated corona frame structures
may be positioned on opposite sides of the power conductor 119 to
create an outer boundary of the sensor apparatus 300 that surrounds
a portion of the power conductor 119. In addition, an inner volume
may be present within an envelop formed between the corona frame
structures and the power conductor 119. Within the inner volume,
the electric field may be lowered so creation of corona by any
objects with sharp edges is minimized. Other shaped corona frame
structures, such as a circle, an ellipse, etc. may also be used for
the corona structure 100 so long as the conductive radius of
curvature(s) included in the shape are capable of distributing the
electric field to the desired degree. Further, the members that
comprise the corona structure 100 may be fashioned using multiple
members or forms that emulate a larger radius of curvature. In this
way, the same large radius of curvature of the corona structure 100
is not required for objects that reside inside the volume defined
by the corona frame structure(s) of the corona structure 100.
[0042] The corona structure 100 may be connected with guide braces
101 that form a guide brace structure. The guide braces 101 may be
formed of a lightweight, low density solid or hollow material with
sufficient rigidity to perform the functionality described. In the
illustrated embodiment, the guide braces are tubular structures. In
other examples, other cross-sectional geometries and/or multiple
cross-sectional geometries may be used. Each of the guide braces
101 may be continuous members, or struts, that extend radially
outward and are coupled with one or more of the corona frame
structures.
[0043] The guide braces 101 in combination with corona structure
100 may form a continuous open framework of interconnected members.
The interconnected members may be coupled to define a plurality of
apertures, air spaces, or cells within the sensor apparatus 300. In
addition, the interconnected members may longitudinally extend a
predetermined length that is substantially larger than a
cross-sectional area of the interconnected members. In the
illustrated example, the guide braces 101 are struts with each end
connected with a different one of the corona frame members. A
mid-section of each of the guide braces 101 is formed to extend to
a central region of the sensor apparatus 300 and be coupled with
the mounting plate 104.
[0044] The guide braces 101 may also be formed in a guide brace
structure. The guide base structure may maintain the corona
structure 100 in a determined position with respect to a power
conductor 119 when the sensor apparatus 300 is installed. The guide
braces 101 may also provide support and/or coupling locations for
the coupling devices 103, the electronics assembly 110 and the
current sensor assembly 120. In addition, the guide braces 101 may
include a conductor guide portion that is formed to assist in
guiding the power conductor 119 when a power conductor 119 comes
into contact with the conductor guide portion of the guide
braces.
[0045] During installation of the sensor apparatus 300, the
conductor guide portion may be utilized to help channel the power
conductor 119 towards the coupling devices 103 and the current
sensor assembly 120. Accordingly, the conductor guide portion of
the guide braces may reposition the sensor apparatus 300 with
respect to the power conductor 119 so that the coupling devices 103
and the current sensor assembly 120 are moved into a desired
predetermined alignment with respect to the power conductor
119.
[0046] As seen in FIGS. 3 and 4, a mounting plate 104 may be
coupled with the guide braces 101. The mounting plate 104 may
provide a mounting position for the insulating blocks 102. In
addition, the mounting plate 104 may substantially eliminate
independent movement of the guide braces 101, and fixedly maintain
the position of the guide braces 101 with respect to each other. In
other examples, the guide braces 101 may be fixedly maintained in
position by welding, fasteners, or any other rigid coupling
mechanism. A mounting bar 105 may also provide a location to mount
both the current sensor assembly 120 and the electronics assembly
110. In one embodiment, the current sensor assembly 120 is mounted
directly above the electronics assembly 110, which allows for
proper weight distribution of the sensor apparatus 300 after
installation and allows for self leveling in a desired position
when the sensor apparatus 300 is installed on a power conductor
119.
[0047] After installation, the current sensor assembly 120 may be
concentric with the power conductor 119. The electronics assembly
110 may be mounted on a lower portion of the sensor apparatus 300
such that the center of gravity of the sensor apparatus 300 may be
below the power conductor 119. The electronics assembly 110 may be
positioned to be at a determined angle below the current sensor
assembly 120 to improve environmental resistance by enabling water
to run off the electronics assembly 110 without collecting
thereon.
[0048] Referring back to FIG. 2, each of the insulating blocks 102
may include an engagement mechanism 108 that is electrically
isolated from the coupling device 103. In FIG. 2, the example
engagement mechanisms 108 are threaded members. Each of the
engagement mechanisms 108 may be selectively engaged with a hot
stick 118. The hot sticks 118, once engaged with the engagement
mechanisms 108, may be used to mount the complete sensor apparatus
300 to a power conductor 119. The insulating blocks 102 may also
connect the coupling devices 103 to the corona structure 100, while
maintaining electrical isolation therebetween. Thus, the coupling
device 103 may be at the voltage level of the power conductor 119,
while the insulating blocks 102 may maintain the remainder of the
sensor apparatus 300 at a lower potential.
[0049] As described later, the ability to maintain a portion of the
sensor apparatus 300 at a lower potential enables the sensor
apparatus to generate power as a function of the line voltage
present on the power conductor 119 and an effective body
capacitance of the corona structure 100. The effective body
capacitance of an object, such as the corona structure 100, is a
combination of a free body capacitance of the object, the effect of
the body with respect to earth, and the effect of the body with
respect to other objects. Free body capacitance generally refers to
the capacitance of an object in free space.
[0050] The coupling devices 103 may be used to maintain the
positional relationship between the sensor structure 300 and a
power conductor 119. The coupling devices 103 may be formed of a
conductive material that electrically couples one side of a primary
winding of a power supply included in the sensor structure 300 to
the power conductor 119, while maintaining electrical isolation
from the rest of the structure through the insulating blocks 102.
The coupling devices 103 may be remotely opened and closed from a
distance using a hot stick 118 during installation or removal of
the sensor apparatus 300 from a power conductor 119. In one
embodiment the coupling devices 103 are opened and closed using the
engagement mechanism 108, such as a threaded member or an I-bolt.
Other forms of engagement mechanisms and mechanical closing means
may also be used, such as a ratchet, spring loaded clamps and/or
any other mechanism to maneuver the coupling devices 103 between an
opened and a closed position.
[0051] Referring to FIGS. 6 and 7, in another example embodiment of
the sensor apparatus 300, insulating blocks 106 may be located
between the ends of the guide braces 101 and the corona structures
100. With this placement, the insulating blocks 106 may maintain
electrical isolation between the corona structures 100 and the
coupling devices 103. Both the coupling devices 103 and a portion
of the sensor apparatus 300 that includes the electronic assembly
110 and the current sensor assembly 120, may be at the same
potential as the power conductor 119. The mounting plates 104 may
be fixedly coupled to the coupling devices 103 such that they form
integral units.
[0052] As further illustrated in FIGS. 6 and 7 the mounting plates
104 may be removeably coupled to mounting bars 107 that are also
coupled to mounting bracket 109. Mounting bracket 109 can be used
to couple the corona structure 100 to the current sensor assembly
120. Alternatively, or in addition, mounting brackets 122 may be
used to connect the electronics assembly 110 to the current sensor
assembly 120.
[0053] In the example embodiment of FIGS. 6 and 7, mounting plates
104 may be coupled with one or more coupling devices 103. As
illustrated, a single coupling device 103, such as a voltage clamp,
can be used and connected to a first one of the mounting plates 104
on one side of the sensor apparatus 300. An insulating block pad
121 may be coupled with a second one of the mounting plates 104
such that the insulating block pad 121 may provide an insulating
and mechanical barrier between the power conductor 119 and the
second one of the mounting plates 104. A lug 123, such as a hot
stick connection bracket may be attached to the second one of the
mounting brackets 104 to enable balanced support of the sensor
apparatus 300 while the sensor apparatus 300 is installed on the
power conductor 119. Where two coupling devices 103, such as
voltage clamps, are used, insulation may be disposed between at
least one coupling device 103 and the remainder of the sensor
apparatus 300 to prevent line current from flowing through the
sensor apparatus 300 rather than the power conductor 119, which
could affect current measurement accuracy.
[0054] Referring now to FIGS. 2-7, the electronics assembly 110
comprises an electronics carriage 111, a sealed connector 112, a
first antenna 113, a second antenna 114, a cover 115, a current
sensor line 116 and a power supply line 117. In the illustrated
example, the electronics carriage 111 may form a housing or pan
having an interior area (not shown). The electronics carriage 111
of one example may be positioned at the top of the electronics
assembly 110. Alternatively, the electronics carriage 111 may form
the side, bottom, top, or any combination, or portions thereof of
the electronic assembly 110, or may be installed within a housing
of the electronics assembly 110.
[0055] Access to an interior area of the electronics carriage 111
for maintenance, etc. may be via the cover 115. The cover 115 may
be a removable wall section formed to enclose an opening in the
electronics carriage 111, or the housing. The interior area of the
electronics carriage 111 may provide a mounting area to mount a
plurality of electronic devices, such as a conductor mountable
device, a processor, memory, analog-to-digital converters, filters,
the power supply and any other electronic devices used to provide
the functionality described herein. In addition, electronic devices
such as communication and/or signal processing devices associated
with the sealed connector 112, the first antenna 113, the second
antenna 114, the current sensor line 116, the power supply line
117, and/or any other input output related electronic devices may
be included in the interior area. The electronic carriage 111 also
may enable coupling of the electronics assembly 110 with the corona
structure 100 through mounting bar 105.
[0056] The sealed connector 112 may provide an electrical
connection to couple with and communicate with internal device
electronics without removing the cover 115. For example, a
computer, such as a laptop, a personal data assistant (PDA), a
specialized terminal, etc., may be coupled with the sealed
connector 112 to download and upload data, perform diagnostics,
debug, upgrade, etc. The sealed connector 112 may be any form of
multi-contact electrical connector that is surface mountable on the
electronics assembly 110. The sealed connector 112 may also provide
an environmental seal between the internal electronic devices
located inside the electronics assembly 110, the multi-electrical
contacts and external environmental conditions, such as moisture.
The sealed connector 112 may also enable a powered connection to
the electronics assembly 110 so the sensor apparatus 300 can be
powered prior to installation on a power conductor 119.
[0057] The first antenna 113 may enable the sensor apparatus 300 to
communicate and receive time and/or position data, or send/receive
data depending upon the application, via an external communication
device, such as a satellite. For example, the first antenna 113 may
include a global positioning system ("GPS") antenna for receiving
GPS data from a GPS satellite. The first antenna 113 includes a
proximate end and a distal end. The proximate end may be mounted to
the electronics assembly 110. The distal end of the first antenna
113 may longitudinal extend away from the electronics assembly 110
a predetermined distance. The distal end of the first antenna 113
may be positioned to minimize exposure of the first antenna 113 to
corona discharge. For example, the distal end of the first antenna
113 may be substantially centered with regard to one or more of the
corona frame structures included in the corona frame 100. In
addition, the first antenna 113 may be positioned to allow a
communication path to one or more satellites. In other examples,
where the communication path is unaffected by the position of the
first antenna 113 and/or the first antenna 113 is impervious to
corona discharge, the first antenna may be located elsewhere.
[0058] The second antenna 114 may be a radio frequency or radio
antenna designed to wirelessly communicate data such as telemetry
data to a device external to the sensor apparatus 300. The second
antenna 114 may also be mounted on a surface of the electronics
assembly 110. The second antenna 114 may be used to communicate to
a ground based station. In one example, the second antenna 114 may
be a planar type antenna. While other types of radio antennas may
be used, such as a whip antenna, the use of the planar type antenna
is advantageous because it is low profile, which minimizes wind
resistance and corona formation. The radio antenna 114 may be
advantageously position on a surface, such as a bottom surface, of
the electronics assemble to enable an efficient radiation pattern,
and thus more effective usage when the sensor apparatus 300
installed on an elevated power conductor 119. In other examples,
one antenna may perform the functionality of both the first antenna
113 and the second antenna 114.
[0059] The processor may be any computing device capable of
execution of instructions to perform logic. The memory may be any
form of data storage device accessible by the processor and/or any
other device. The memory may store instructions executable by the
processor. In addition, the memory may store installation specific
data, measurement data, power parameter data and/or any other data
related to the functionality and operation of the sensor apparatus
300. Thus, data provided with the current sensor assembly 120 may
be accrued over a period of time in the memory and then
periodically transmitted in a batch to an external device, such as
a ground based station. In addition, measured and/or determined
data may be stored as a backup in the memory in case data
transmission is impeded, delayed or some other failure occurs. The
data stored in memory may also enable downloading of any current
sensor assembly 120 data measurements after removal of the sensor
apparatus 300 from the power conductor 119. Further, data storage
in memory can be used to omit the need for the second antenna 114,
as the measurement data may be retrieved at a later time, instead
of communicating the data real-time or at determined intervals with
RF communications to a device external to the sensor apparatus 300
during operation on a power conductor 119.
[0060] The current sensor assembly 120 may be coupled with the
electronics assembly 110 via the current sensor line 116. In one
example, the current sensor line 116 is a shielded, flexible
multi-conductor cable that is sealed at both the current sensor
assembly 120 and the electronics assembly 110 with a weatherproof
connector, such as a cable gland. In other examples, any form other
form of cable and/or connector may be used. In one embodiment, the
data to be transmitted between the current sensor assembly 120 and
the electronics assembly 110 may be transmitted wirelessly, such as
with Bluetooth communications, and the current sensor line 116 may
be omitted.
[0061] The power supply line 117 may be coupled between one of the
coupling devices 103 and the electronics assembly 10. In one
example, the power supply line is a flexible high voltage cable
that connects one side of a primary winding included in the power
supply included in the electronics enclosure 110 to the power
conductor 119 thru the coupling device 103. The power supply line
117 can be sealed with weather proof connectors, such as cable
glands, at either or both ends. In addition, or alternatively, the
power supply line 117 may be coupled with the coupling device 103
with a fastener, such as a bolt.
[0062] FIGS. 8 through 15 illustrate example embodiments of the
current sensor assembly 120. The current sensor assembly 120 may
repeatably and accurately hold and guide a winding assembly, from
an open position, shown in FIG. 8, to a closed position shown in
FIG. 9. The current sensor assembly 120 may include a split-core
current transformer (CT). In the split-core CT, the winding
assembly may be split into a first winding assembly 205 and second
winding assembly 206 (FIG. 8) that enable installation of the
current sensor assembly 120 to be positioned to surround a portion
of a power conductor 119 without needing to break, or open, a
continuous power conductor 119. This advantageously allows
installation on live power conductors 119 without requiring that
power be removed from the power conductor 119.
[0063] While closed, the current sensor assembly 120 may also
provide protection of the winding assembly from environmental
elements, such as moisture and dirt. In addition, the current
sensor assembly 120 may include an electrically conductive
enclosure that provides an electromagnetic shield for the winding
assembly. The current sensor assembly 120 may also include
electronic devices related to collection and processing of measured
power parameters. Example electronic devices include compensation
circuitry, a power supply circuit, amplifiers, signal converters,
filters, a communication module, etc. that are related to
calibration, measurement and processing of power parameters. In
addition, the electronic devices may include memory that can store
calibration constants, CT specific information such as an accuracy
class, ratios, site information and/or any other data related to
the current sensor assembly 120. The electronic devices may be
accessed via access covers 165 and 175.
[0064] In one embodiment, the current sensor assembly 120 includes
body portions that are a first half of a housing 130 and a second
half of a housing 135. The first half of a housing 130 and the
second half of a housing 135 may be formed of a rigid material,
such as metal. The halves of the housing 130 and 135 may fit
together and be fixedly held with fasteners 132, to form a first
housing assembly 134 and a second housing assembly 136. The first
and second housing assemblies 134 and 136 may each be configured to
surround a portion of a power conductor and have the respective
first and second winding assemblies 205 and 206 disposed
therein.
[0065] In addition, each of the first and second housing assemblies
134 and 136 may include an outer covering. The outer covering may
be a separately attached material, or may be an integrally formed
part of the first and second housing assemblies 134 and 136. The
outer covering may be constructed of an electrically conductive
material to provide electromagnetic shielding. In addition, the
outer covering may include environmental shielding properties. The
environmental shielding properties may provide a liquid and dust
tight enclosure.
[0066] As best illustrated in FIG. 8, each of the first and second
housing assemblies 134 and 136 also include a first inner mating
surface 207 and a second inner mating surface 208. The first and
second inner mating surfaces 207 and 208 on each of the first and
second housing assemblies 134 and 136 are separated away from each
other when the current sensor assembly 120 is in the open position,
and are adjacently aligned when the current sensor assembly 120 is
in the closed position.
[0067] The combined halves of the housings 130, 135 also form an
interleaved rotating hinge, about a pin 180 and interlocking teeth
140, 145. The interleaved rotating hinge provides a pivot point to
enable the first and second housing assemblies 134 and 136 to be
transitioned between the open position and the closed position. The
interlocking teeth 140, 145 may extend away from the first inner
mating surfaces 207 included on the first and second housing
assemblies 134 and 136. The extended interlocking teeth 140, 145
may provide mechanical protection to the exposed surface(s) of the
winding assemblies 205 and 206. Mechanical protection may be
provided while the current sensor assembly 120 is in the open
position and is being guided over a power conductor 119 (FIG. 2) to
position the power conductor to be aligned substantially concentric
with the current sensor assembly 120. If the power conductor is
inadvertently moved into contact with the teeth 140 and 145, the
teeth 140 and 145 may prevent damage, such as a scratch or dent on
exposed contact surfaces of the winding assemblies 205 and 206.
Such damage to the winding assemblies 205 and 206 may potentially
render the current sensor assembly 120 inaccurate or inoperable. In
addition, the teeth 140 and 145 may also enable the centering of
the power conductor 119 concentrically with the current sensor
assembly 120.
[0068] A shield 150 may be attached to at least one of each of the
first and second housing assemblies 134 and 136 adjacent to the
second inner mating surfaces 208. The shield 150 may prevent a
power conductor from getting pinched between the second mating
surfaces 208 when the first and second housing assemblies 134 and
136 transitioned to the closed position. In addition, similar to
the teeth 140 and 145, the shield 150 may provide protection to the
contact surfaces of the winding assemblies 205 and 206 and enable a
power conductor 119 to be concentrically aligned with the current
sensor assembly 120. Gaskets may be provided on one or both of the
first and second inner mating surfaces 207, 208. When the current
sensor assembly 120 is in the closed position, the gaskets may be
compressed by the first and second inner mating surfaces 207, 208
to provide a water and dust tight seal for the current sensor
assembly 120.
[0069] An insulator 160 may be coupled with the first and second
housing assemblies 134 and 136 to prevent the conductor from
touching any exposed metal surface of the current sensor assembly
120. An electrical isolation, on the order of a few kilovolts, may
be produced between the power conductor and the corona frame 100
(FIG. 2) in order for the power supply of the sensor apparatus 150
to provide current at a secondary winding of the power supply. The
insulator 160 may maintain this voltage isolation. In the
alternative embodiment illustrated in FIGS. 6 and 7, the power
supply may be configured such that electrical isolation between the
current sensor assembly 120 and the power conductor 119 may not be
required. Accordingly, in this embodiment the insulator 160 may be
omitted.
[0070] In the illustrated embodiment of the current sensor assembly
120, the mechanism for opening and closing the current sensor
assembly 120 may be designed to be operated remotely with a hot
stick 118. The hot stick 118 may include an opening and closing jaw
that can be selectively coupled with a lever 194 included on the
current sensor assembly 120. The opening and closing jaw of the hot
stick 118 may be selectively coupled with the lever 194 to actuate
the current sensor assembly 120 between the open and closed
positions.
[0071] In the embodiment illustrated in FIGS. 8-10, the lever 194
is depicted as a threaded member 200. In this embodiment, the
opening and closing jaw of the hot stick 118 may be passed through
an eye ring included on the rotatable and threaded member 200. In
FIGS. 8 and 9, the example hot stick 118 is depicted in a partially
clamped position, and in FIG. 10, the example hot stick 118 is
depicted in a fully clamped position. The example threaded member
200 passes through a first member on the second housing assembly
136 such as through a keyed block 190 and through a threaded keyed
surface 191.
[0072] During operation, when the threaded member 200 is rotated
with the hot stick 118, the portion of threaded member 200 above
the keyed block 190 becomes longer or shorter, depending on the
direction of rotation. The threaded member 200 also passes through
a second member on the first housing assembly 134, such as through
an unkeyed block 185 and through a plain clearance hole (not
shown). The plain clearance hole enables the threaded member 200 to
rotate freely within the unkeyed block 185. However, a clip ring
198 and nuts 192 may constrain the threaded member 200 within the
unkeyed block in an axial direction of the threaded member 200.
Alternatively, the clip ring 198 and nuts 192 may be replaced with
a slotted nut and cotter pin, or any other mechanical mechanism to
constrain the axial travel of the threaded member 200.
[0073] When the threaded member 200 is rotated, axial displacement
along the threaded member 200 is created between the keyed block
190 and the unkeyed block 185. This movement is transferred to the
first housing assembly 134 through bolts 195, forcing the second
housing assembly 136 to rotate about a pin 180 thereby producing
the opening and closing action of the current sensor assembly 120.
In one example, the keyed surface 191 of keyed block 190 may be
formed to fit into a keyed section 126 of an example hot stick 118
when the hot stick 118 mechanism is fully clamped, as illustrated
in FIG. 10. This may provide additional stability between the hot
stick 118 and the current sensor assembly 120 while it is being
installed over a power conductor 119.
[0074] In alternative embodiments, other systems and/or mechanisms
may be used to actuate the current sensor assembly 120 between the
open and closed positions. For example, the latch might be operated
by other mechanisms, such as a self-actuated hinge that is remotely
operated and/or self powered. In addition, the first and second
housing assemblies 134 and 136 of the current sensor assembly 120
may be selectively coupled through any of a variety of mechanisms
that allow the current sensor assembly 120 to be opened, aligned
with a power conductor, and closed. For example, the first and
second housing assemblies 134 and 136 may be joined around a power
conductor by the use of magnets, bolts, linkages, a sliding screw,
a ball joint, or any other mechanism of joining the first and
second housings 134 and 136 in a repeatable manner.
[0075] FIG. 11 depicts the current sensor assembly 120 with one of
the halves of the housings 135, 130 removed. The electronic devices
included in the current sensor assembly 120 may be mounted into the
first and second housing assemblies 134 and 136 behind access
covers 165, 175. The wiring for the current sensor assembly 120 may
exit via a hole formed in access cover 165 and a strain relief 170.
The strain relief may be located on the current sensor assembly 120
in a position that provides unobstructed operation of the lever 194
for opening and closing the current sensor assembly 120.
Compensation circuitry 210 for the CT cores 240, 245 may be
included in the first and/or second housing assemblies 134 and 136,
such as mounted to the access cover 165. In one embodiment, during
operation, the compensation circuitry 210 may operate to actively
compensate a ratio and a phase of the current sensor assembly 120.
Accordingly the current sensor assembly 120 may operate with a very
low ratio and phase error with respect to the measured line current
signal of the power conductor.
[0076] In one embodiment, a determined voltage, such as 12 volts DC
may be supplied to the current sensor assembly 120 via the current
sensor line 116 (FIG. 4). The determined voltage may be supplied
from the power supply included in the electronics assembly 110. The
compensation circuitry 210 may be powered with the determined
voltage. Alternatively, or in addition, a power supply circuit 215
for the compensation circuitry 210 may be optionally provided in
the current sensor assembly, such as mounted on access cover 175.
The power supply circuit 215 may enable the current sensor assembly
120 to be powered separately, such as with a battery or other power
source. Wiring between the power supply circuit 215 and the
compensation circuit 201 may be routed in a slot 220 formed in each
of the first and second housing assemblies 134 and 136.
[0077] The examples of the current sensor assembly 120 depicted in
FIGS. 8-15 may also be used separately from the sensor apparatus
300. Use separate from the sensor apparatus 300 may be enabled by
the option to include the power supply circuitry 215, behind access
cover 175. In an alternative or additional embodiment the power
supply 215 may be accessible with a hot stick 118, and may be
removed or installed while the sensor apparatus 300 is installed.
For example the current sensor assembly 120 may be powered using a
power source, such as a battery, and the battery may be installed
or removed from the current sensor assembly 120 using a hot stock
118. Thus, a user may modify the power source, such as increase the
available power, or replace the battery, if required while the
current sensor assembly 120 remains installed on a power
conductor.
[0078] As illustrated in FIGS. 8 and 11, the current sensor
assembly 120 also includes the first and second winding assemblies
205 and 206. The first and second winding assemblies 205 and 206
each comprise a main CT core 240, a compensation CT core 245, a
carrier 235, pins 250, 255, a main winding 225 and a compensation
winding 292. In the illustrated split-core design, the main CT core
240 and the compensation CT core 245 may each include a plurality
of discrete core portions. Thus a first discrete core portion of
each of the main CT core 240 and the compensation CT core 245 may
be included in the first housing assembly 134 in the first winding
assembly 205 and a second discrete core portion of each of the main
CT core 240 and the compensation CT core 245 may be included in the
second housing assembly 136 in the second winding assembly 206. In
the illustrated example, each of the core portions may be formed in
a semi-circle within a respective one of the first housing assembly
134 and the second housing assembly 136.
[0079] The carrier 235, which may also be referred to as an H-core,
may be included in each of the first and second winding assemblies
205 and 206. The carrier 235 may support in at least one dimension
the main CT core 240 and the compensation CT core 245. In addition,
the carrier 235 may fixedly hold in place the main CT core 240 and
the compensation CT core 245. The carrier 235 may be formed with
any rigid material, such as plastic, carbon fiber, steel, aluminum,
etc. The carrier 235 may also be formed as a single unitary member
of single piece construction. Alternatively, the carrier 235 may
comprise a plurality of discrete members that are coupled to form
the carrier 235. The main CT core 240 and the compensation CT core
245 may be maintained in contact with the carrier 235 with the aid
of a bonding agent, such as an adhesive material (for example
epoxy), a mechanical fastener, friction fit or any other form of
holding mechanism. Alternatively, a holding mechanism external to
the carrier 235 may support and/or hold the main CT core 240 and
the compensation CT core 245 in contiguous contact with the carrier
235.
[0080] In another example, the carrier 235 may be formed with a
semi-rigid, or flexible material that allows flexible accommodation
of the CT cores 240 and 245. Accordingly, machining and winding
tolerances of the CT cores 240 and 245 and the windings 225 and 292
may be larger while still being flexibly accommodated in the
carrier 235. Following installation of the CT cores 240 and 245 and
the windings 225 and 292 in the carrier 235, the bonding agent may
be used to not only maintain contact but also to provide rigidity
to the carrier 235. In addition, or alternatively, installation of
the CT cores 240 and 245 and the windings 225 in the carrier 235
may provide desirable rigidity to the carrier 235.
[0081] Similar to the CT cores 240 and 245, the carrier 235 may
also be divided into a plurality of carriers 235 disposed in each
of the first housing assembly 134 and the second housing assembly
136. Each of the carriers 235 may be disposed in the first and
second winding assemblies 205 and 206 to support the core portions
of the main CT core 240 and the compensation CT core 245.
[0082] Each of the discrete portions of the main CT core 240 and
the compensation CT core 245 may include contact surfaces 238 as
best illustrated in FIGS. 11 and 12. The main CT core 240 and the
compensation CT core 245 may be held in contiguous contact with the
carrier 235 so that the contact surfaces 238 of the core portions
in the first housing assembly 134 are substantially co-planar and
may be accurately mated, or contiguously aligned, with opposing
contact surfaces 238 on opposing core portions included in the
second housing assembly 136 when the first and second housing
assemblies 134 and 136 are moved from the open position (FIG. 8) to
the closed position (FIG. 9). Thus, the carrier 235 may initially
achieve and substantially maintain alignment of the core portions
of main CT core 240 and the compensation CT core 245 so that the
contact surfaces 238 are maintained contiguous when the current
sensor assembly 120 is in the closed position.
[0083] The compensation core 245 may be wound with a compensation
winding 292 before being placed in the carrier 235. The
compensation core 245 and compensation winding 292 may
cooperatively operate to measure a current that is used to
compensate for the current measurement of the main CT core 240 and
the main CT winding 225. The compensation winding 292 may be
coupled with the compensation circuitry 210 to effectively reduce
the phase and ratio measurement error of a line current
measurement.
[0084] The main CT core 240 may be wound with the main CT winding
225. The main CT core 240 and the main CT winding 225 may
cooperatively operate to measure an AC current present in a power
conductor when the core sections of the main CT core are aligned to
surround a portion of the power conductor. The main CT winding 225
may be wound on the main CT core 240 in a plurality of sections. In
one example, each of the first and second housing assemblies 134
and 136 may include a core portion of the main CT core 240 wound
with two sections of the main CT winding 225. Each section of the
main CT winding 225 may also be wound around at least a portion of
the carrier 235, the compensation core 245 and the compensation
winding 292 included in the respective first and second housing
assemblies 134 and 136.
[0085] Each carrier 235, and each of the first and second winding
assemblies 205 and 206, may be moveable, or slidable, within the
respective first and second housing assemblies 134 and, 136. The
carriers 235 may be moveable with respect to the respective housing
assembly 234 and 236 on pins 250, 255 in slots 260, 265 (FIG. 10).
The slots 260 and 265 may be formed in the halves of the housing
assemblies 130 and 135. Accordingly, the carriers 235, and each of
the first and second winding assemblies 205 and 206, may be
moveable in at least one dimension relative to the respective
housing assemblies 134 and 136, and restrained from movement
relative to the respective housing assemblies 134 and 136 in at
least one other dimension. As use herein, the term "dimension"
refers to any direction, route or course in three-dimensional
space. The respective pins 250, 255 may be fixedly coupled with the
carrier 235, and extend outwardly from the carrier 235 to engage
the respective slots 260, 265. In other examples, fewer or greater
numbers of pins and slots may be included in the current sensor
assembly 120.
[0086] An elastic component, in this embodiment a spring 230, may
be disposed between the first and second housing assemblies 134 and
136 and a respective one of the first and second winding assemblies
205 and 206 moveably positioned therein. The spring 230 may
maintain pressure on the respective first or second winding
assembly 205 or 206 and/or the carrier 235 to maintain the carrier
235 in a forward biased position within the slots 260 and 265 to
enable optimal contact with/between the contact surfaces 238 and
alignment thereof.
[0087] When the current sensor assembly 120 is closed, the contact
surfaces 238 of the CT cores 240, 245 may contact each other, with
any misalignment, such as a manufacturing tolerance, being
compensated for by movement of the carriers 235, and each of the
first and second winding assemblies 205 and 206, sliding in the
slots 260, 265. The pins 255, 250 may be of different
cross-sectional area, to allow controlled or limited linear and/or
rotational motion, such as a rocking action or a rotation of the
carriers 235, and each of the first and second winding assemblies
205 and 206, with respect to the housings 134 and 136, as the
current sensor assembly 120 is closed. The controlled rocking
action and/or rotation may prevent the moving carriers 235 from
jamming in the slots 260, 265. Alternatively or in addition, the
movement and rotation of the carriers 235, and each of the first
and second winding assemblies 205 and 206, with respect to the
first and second housings 134 and 136 may be enabled by a variety
of other mechanisms, such as adjoining low friction surfaces,
flexible linkages, and/or ball bearings. In another example
embodiment, the carrier 235, and/or each of the first and second
winding assemblies 205 and 206, may be disposed in a compound or
substance having elastomeric properties and be desirably moveable
with respect to the first and second housings 134 and 136.
[0088] When the current sensor assembly 120 is fully closed, one or
more springs 230 may maintain a closing force on the contact
surfaces 238 of the CT cores 240, 245. Thus, the split core CT's
may operate properly, with the core portions of the cores 240, 245
maintained in positive contact with opposed compression forces
supplied by the springs 230. The moveable design of carrier 235,
and each of the first and second winding assemblies 205 and 206,
allows for accurate and automated realignment of the contact
surfaces 238 to minimize machining and manufacturing tolerances and
misalignments, thus decreasing the cost of assembly and
manufacturing of the current sensor assembly 120.
[0089] Alternatively, or additionally, the spring 230 may be
replaced with other any other mechanism that may exert a force on
the carriers 235, and each of the first and second winding
assemblies 205 and 206, to push the contact surfaces 238 towards
each other, such as an elastomeric block or bumper between the
housing assembly 134 or 136 and the carrier 235, rubber bands,
o'rings or any other form(s) of spring elements capable of exerting
force.
[0090] In another embodiment a moveable carrier 235, and
corresponding winding assembly, may be present in only one housing
assembly 134 or 136, and the cores and windings in the mating
housing assembly 134 or 136 may be fixed in place. The movement of
the carrier 235 and the corresponding winding assembly within the
only one housing assembly 134 or 136 may be such that the contact
surfaces 238 of the cores accurately align when the first and
second housing assemblies 134 and 136 are brought together in the
closed position.
[0091] FIG. 12 shows the current sensor assembly 120 with the
insulators 160 removed to expose a first inner surface 270 of the
first half of the housing assembly 130 included in the first
housing assembly 134, and a second inner surface 275 of the first
half of the housing assembly 134 included in the second housing
assembly 136. As best illustrated in FIG. 14, these inner surfaces
270, 275 may almost come into contact with each other, when the
first and second halves of the housing assembly 130 and 135 are
coupled to form the first and second housing assemblies 134 and
136.
[0092] The inner surfaces 270, 275 may be separated by a gap 290 of
a predetermined distance that is defined by the substantially
paralleled facing portions of the inner surfaces 270, 275. The gap
290 may provide electrical isolation of the inner surfaces 270,
275. The gap 290 between the inner surfaces 270, 275 may be a
predetermined distance that disables electrically conductive
contact between the surfaces 270, 275 within the center of the
current sensor assembly 120. Such contact could effectively
represent a shorted winding turn to the current sensor assembly 120
that may affect measurement. The gap 290 may thus eliminates a
conductive path that completely encircles the current sensor
assembly 120 and thus ensure a shorted condition is avoided and
current is measured properly.
[0093] The gap 290 between the inner surfaces 270, 275 may create a
small electrical capacitance. The electrical capacitance may
operate as a filter by providing what is effectively a shorted
transformer turn. Thus, the electrical capacitance generated with
the gap 290 may essentially short out any high frequency currents
flowing on the power conductor. Accordingly, such high frequency
currents may appear at reduced magnitude on the output of the
current sensor assembly 120. The overall effect of the gap 290 may
be to minimize or eliminate high frequency noise from propagation
into the current sensor assembly 120, while desirably allowing the
current sensor assembly 120 to properly measure low frequency (such
as 50 Hz or 60 Hz) AC currents present in a power conductor.
[0094] FIG. 14 also depicts the main and compensation CT cores 240
and 245 as being maintained substantially in parallel and at least
partially disposed within a respective first channel 296 and a
second channel 298 formed adjacently within the carrier 235. Within
the first and second channels 296 and 298, the main and
compensation CT cores 240 and 245 may be separated by a common wall
294 of the carrier 280. The first channel 296 is formed to
accommodate a cross-section of the main CT core 240. The second
channel 298 is formed to accommodate a cross-section of the
compensation CT core 245 and the compensation winding 292 that has
been positioned to surround at least a part of the compensation CT
core 245. A bonding agent 295 may also be disposed in the first and
second channels 296 and 298. The bonding agent 295 may be in
contact with the surface of the CT cores 240 and 245. In addition,
or alternatively, the bonding agent 295 may be in contact with a
surface of the compensation winding 292. In the illustrated
example, the main CT winding 225 is wound to surround the
compensation CT core 245, the compensation winding 292, the main CT
core 240 and the carrier 235.
[0095] As best illustrated in FIGS. 11 and 12, the main and
compensation CT cores 240 and 245 are disposed in the respective
first and second channels 296 and 298 to extend beyond an end of
the first and second channels 296 and 298 by a determined distance.
The main and compensation CT cores 240 and 245 extend beyond the
end of the carrier 235 so that the carrier 235 will not interfere
with alignment and electrical contact between the contact surfaces
238 when the current sensor assembly 120 is in the closed
position.
[0096] FIG. 15 shows a cross-section of another example of the
current sensor assembly illustrated in FIG. 13. In this example
embodiment, a carrier 280 with a single channel configuration is
depicted. In the single channel configuration of the carrier 280,
both the main and the compensation CT cores 240 and 245, and both
the main and compensation CT windings 225 and 292 are enclosed in a
single channel of the carrier 280. The single channel configuration
is formed with three enclosing walls to include an aperture 282
longitudinally extending along the carrier 280. All of the main and
the compensation CT cores 240 and 245, and the main and
compensation CT windings 225 and 292 may be inserted within the
channel through the aperture 282. In the illustrated example, the
main CT core 240 is positioned closer to the aperture 282 than the
compensation CT core 245. In other examples, any other orientation
of the main and the compensation CT cores 240 and 245, and the main
and compensation CT windings 225 and 292 may be implemented.
[0097] In this example, the main and the compensation CT cores 240
and 245 and the main and compensation CT windings 225 and 292 are
maintained substantially in parallel by the carrier 280. Also, in
this embodiment a bonding agent 295 may contact and at least
partially enclose the cores and windings within the carrier 235.
However, in other examples holding mechanisms and/or tolerances and
materials for the carrier and cores and windings may make the
bonding agent 295 unnecessary. Also, in this example, the main CT
winding 225 is wound to surround the compensation CT core 245, the
compensation winding 292, and the main CT core 240, but is disposed
within the carrier 280. Further, the first half of the housing
assemble 130 and the second half of the housing assembly 135 may be
combined to form one of the first housing assembly 134 or the
second housing assembly 136. The first housing assembly 134 or the
second housing assembly 136 may also include the gap 290, as
previously discussed. As in the previously described examples, the
carrier 280 and the winding assembly may be moveably disposed in
the housing.
[0098] In example operation, the sensor apparatus 300 of one
embodiment may be installed by lineman using hot sticks 118, such
as a shotgun hot stick. The hot sticks 118 may be secured to the
insulating blocks 102 and coupling devices 103, while the sensor
apparatus 300 is lying on its side, such as on the ground. Once the
hot sticks 118 are secured, the sensor apparatus 300 may be
manually lifted vertically by starting at the device 300 and
walking the sensor apparatus 300 to a vertical position so that it
is up in the air at the end of the hot sticks 118. Once the sensor
apparatus 300 is vertical, the sensor apparatus 300 may be further
vertically lifted to an elevated power conductor 119 so that the
power conductor 119 come into contact with the guide brace 101. The
sensor apparatus 300 could be further vertically lifted using the
guide brace 101 to guide the power conductor 119 into the throat of
the current sensor assembly 120 and coupling devices 103.
[0099] When the power conductor 119 is positioned in the coupling
devices 103, a hot stick 118 may be released from the insulating
block 102 and used to tighten the coupling device 103 onto the
power conductor 119 using the engagement mechanism 108 (see FIG.
3). After the first of two coupling devices 103 are secured, the
procedure could be repeated with another hotstick to fully secure
the device 300 to the power conductor 119. The final step could be
to use one of the hot sticks 118 to couple the current sensor
assembly 120 to the power conductor 119 by connecting the hot stick
118 to the threaded member 200 of the current sensor assembly 120
and turning it until the current sensor assembly 120 is fully
closed. Alternatively, yet another hot stick 118 may be coupled to
the threaded member 200 of the current sensor assembly 120 at the
beginning of the procedure, to assist by steadying the sensor
apparatus 300 during lifting, and to then close the current sensor
assembly 120 when appropriate. In still other alternatives, or in
addition, the sensor apparatus 300 may be mounted on the conductor
by other remote means. For example the sensor apparatus 300 may be
adapted to be mounted by cables or a long insulating pole, such as
a hot stick, from a helicopter, crane, bucket truck, by an
installer that is attached to the power conductor, and/or by any
other remote means.
[0100] After installation, the sensor apparatus 300 of one
embodiment may be indirectly powered using the electric field from
the power conductor 119. In this example embodiment, the sensor
assembly 300 may include the power supply. The power supply may
include an ultra-high efficiency transformer (not shown). The
ultra-high efficiency transformer may have a high voltage primary
winding that is electrically connected between the power conductor
119 (via coupling device 103) and the corona structure 100. The
transformer may also include a secondary winding. The effective
body capacitance of the corona structure 100 may allow an AC
current to flow.
[0101] The AC current may flow as the free body capacitance charges
and discharges in response to the sinusoidal waveform of the line
voltage on the power conductor 119. As a result of the AC current
flow, a difference in potential between the power conductor 119 and
the corona structure 100 may occur. The AC current may magnetize
the transformer core via the primary winding and allow a primary
voltage of the transformer to build up on the primary winding. An
electronic clamping circuit may limit the primary voltage buildup
to a predetermined voltage, such as approximately 3 kV.
Accordingly, the power supply may develop power to supply devices
included in the sensor apparatus 300, as well as supply power to a
power connection that may be used to power devices external to the
sensor apparatus 300.
[0102] An output voltage and current from a secondary winding of
the transformer may be stepped down, rectified (or not rectified)
and used to power the electronic devices in the electronics
assembly 110 and the current sensor assembly 120. The output
voltage of the secondary winding may be rectified by a voltage
rectifier, such as a full bridge rectifier. For example, a voltage
on the current sensor line 116 that may be used to power the
current sensor assembly 120 may be stepped down by the transformer
and rectified, to generate a determined DC voltage, such as stepped
down from approximately 3 KVAC to about 12 VDC. An example power
supply with a primary winding coupled between a power conductor and
a corona frame is further described in pending U.S. patent
application Ser. No. 10/877,742, entitled "Method and Apparatus for
Instrument Transformer Reclassification", filed on Jun. 25, 2004,
and PCT Patent Application Serial No. PCT/US2004/23645, entitled
"Body Capacitance Electric Body Capacitance Electric Field Powered
Device for High Voltage Lines," filed on Jul. 22, 2004, both of
which are herein incorporated by reference.
[0103] Herein, the phrase "coupled with" or "coupled to" is defined
to mean directly connected to or indirectly connected through one
or more intermediate components. Such intermediate components may
include hardware and/or software based components. Further, to
clarify the use in the pending claims and to hereby provide notice
to the public, the phrases "at least one of <A>, <B>, .
. . and <N>" or "at least one of <A>, <B>, . . .
<N> or combinations thereof" are defined by the Applicant in
the broadest sense, superseding any other implied definitions
herebefore or hereinafter unless expressly asserted by the
Applicant to the contrary, to mean one or more elements selected
from the group comprising A, B, . . . and N, that is to say, any
combination of one or more elements A, B, . . . or N including any
one element alone or in combination with one or more of the other
elements which may include, in combination, additional elements not
listed.
[0104] The previously described embodiments of the sensor apparatus
300 describe a mechanical design and a system to install and
monitor power parameters on a power conductor 119 such as a high
voltage transmission line. The sensor apparatus 300 may also
include mechanisms for compensating for inaccuracies in the output
of instrument transformers included in a power system. The sensor
apparatus 300 may further include a corona frame structure to
provide protection from corona discharge and a conductor mountable
device that may be used to measure a power parameter such as
current.
[0105] In one example, the sensor apparatus 300 includes a current
sensor assembly 120 that is accurate, self contained, easier to
install and easier to use. The sensor apparatus 300 may also
include GPS and/or time-syncing capabilities to improve measurement
accuracy. In addition, the current sensor assembly 120 may include
a housing that can contain operating logic and electronics, such as
the power supply and compensation circuitry. The current sensor
assembly 120 may also include a split-core current transformer
design that includes a pivot mechanism and a carrier moveably
disposed in each of a first housing assembly 134 and a second
housing assembly 136 that form the housing. The carrier may include
discrete portions of the main CT core 240 and the compensation CT
core 245, and be moveable with respect to the housing assemblies
134 and 136 to allow contact surfaces 238 included on the discrete
cores to be contiguously aligned when the housing is in the closed
position.
[0106] The sensor apparatus 300 may also include a post
installation auto-positioning system that uses weight distribution
to position the sensor apparatus 300 with respect to a power
conductor 119. In addition, the sensor apparatus 300 may include an
installation guidance system. The auto-positioning system and the
installation guidance system may provide for easier installation,
and the ability to install the sensor apparatus 300 on a live power
conductor without having to first interrupt and/or de-energize the
power conductor.
[0107] Radio frequency antenna(s) may provide communication of
telemetry data, GPS timing/position data or both to enable ease of
communication with, and use of, the installed sensor apparatus 300.
Shieldable and weatherproof coupling mechanisms that are insulated
from the corona structure of the sensor apparatus 300 as well as
other environmental protective features may also be provided. The
sensor apparatus 300 may also have an open frame design. The open
frame design may allow for modularity in the sensor apparatus, i.e.
allow for the addition of additional components without requiring
that those additional components feature a smooth or identical
radius as may be required by a corona structure. The open frame
design may also enable radio frequency communication with minimized
interference, and provide a strong lightweight functional structure
that minimizes detrimental effects due to high wind, rain and/or
other environmental related conditions. The sensor apparatus 300
may also use capacitive power rather than powering the sensor
apparatus 300 directly from the magnetic field of the power line,
or power the sensor apparatus 300 from a battery.
[0108] It is therefore intended that the foregoing detailed
description be regarded as illustrative rather than limiting, and
that it be understood that it is the following claims, including
all equivalents, that are intended to define the spirit and scope
of this invention.
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