U.S. patent application number 14/621811 was filed with the patent office on 2015-06-11 for on-line time domain reflectometer system.
This patent application is currently assigned to UTILX CORPORATION. The applicant listed for this patent is UTILX Corporation. Invention is credited to Nelson Hall, William R. Stagi.
Application Number | 20150160283 14/621811 |
Document ID | / |
Family ID | 43429771 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150160283 |
Kind Code |
A1 |
Hall; Nelson ; et
al. |
June 11, 2015 |
ON-LINE TIME DOMAIN REFLECTOMETER SYSTEM
Abstract
A number of TDR systems and testing methods are provided that
improve the quality and accuracy of information collected when
propagating a signal along a length of cable in order to pinpoint
specific anomalies. One or more of the TDR systems includes, for
example, a computing device, a pulse generator, and at least one
capacitive test sensor. The at least one capacitive test sensor
transmits/receives pulses to/from a power system component, such as
an insulated power cable, in a capacitive manner.
Inventors: |
Hall; Nelson; (Kent, WA)
; Stagi; William R.; (Burien, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UTILX Corporation |
Kent |
WA |
US |
|
|
Assignee: |
UTILX CORPORATION
Kent
WA
|
Family ID: |
43429771 |
Appl. No.: |
14/621811 |
Filed: |
February 13, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12820886 |
Jun 22, 2010 |
8988099 |
|
|
14621811 |
|
|
|
|
61219289 |
Jun 22, 2009 |
|
|
|
Current U.S.
Class: |
324/533 |
Current CPC
Class: |
G01R 31/11 20130101 |
International
Class: |
G01R 31/11 20060101
G01R031/11 |
Claims
1. A method of testing a power system component for anomalies,
comprising: capacitively coupling one or more test sensors to an
on-line insulated medium voltage power transmission cable;
generating a test pulse via a pulse generator having an output
impedance greater than 500 ohms; transmitting the test pulse to at
least one test sensor of the one or more test sensors; capacitively
transmitting the test pulse from the at least one test sensor of
the one or more test sensors onto the medium voltage insulated
power cable so that the test pulse travels along the medium voltage
insulated power cable; and capacitively receiving a reflected pulse
by one test sensor of the one or more test sensors from the medium
voltage insulated power cable, the reflected pulse resulting from
the test pulse interfacing with an anomaly along the medium voltage
insulated power cable.
2. The method of claim 1, further comprising: displaying the
reflected pulse on a display in a time domain.
3. The method of claim 1, further comprising: amplifying the
received reflected pulse with an amplifier having an input
impedance of greater than 500 ohms.
4. The method of claim 1, wherein said generating a test pulse via
a pulse generator having an output impedance greater than 500 ohms
includes generating a test pulse via a pulse generator having an
output impedance greater than 1000 ohms.
5. The method of claim 1, wherein said capacitively coupling one or
more test sensors includes capacitively coupling a first test
sensor to the on-line insulated medium voltage power transmission
cable for receiving the test pulse from the pulse generator and
capacitively transmitting the test pulse to the insulated medium
voltage power transmission cable and capacitively coupling a second
test sensor to the on-line insulated medium voltage power
transmission cable for capacitively receiving the reflected
pulse.
6. The method of claim 1, wherein said capacitively coupling one or
more test sensors to an on-line insulated medium voltage power
transmission cable includes capacitively coupling one or more test
sensors to an on-line insulated medium voltage power transmission
cable carrying at least medium voltage power.
7. A method of testing a power system component for anomalies,
comprising: connecting, in electrical communication, a pulse
transmission line with a test sensor housed in a medium voltage
power cable termination elbow; generating a test pulse and
transmitting the test pulse to the test sensor via the pulse
transmission line; capacitively transmitting the test pulse from
the test sensor onto a medium voltage power cable coupled to the
medium voltage power cable termination elbow so that the test pulse
travels along the medium voltage power cable; and capacitively
receiving a reflected pulse by the test sensor from the medium
voltage power cable, the reflected pulse resulting from the test
pulse interfacing with an anomaly along the medium voltage power
cable or an electronic component connected to the medium voltage
power cable.
8. A time domain reflectometry system, comprising: an on-line
dielectrically insulated medium voltage power transmission cable
configured to carry medium voltage power; a transmit circuit
including a pulse generator configured to generate a pulse, the
transmit circuit configured to capacitively impart the pulse onto
the medium voltage power transmission cable; and a receive circuit
configured to capacitively receive a reflected pulse from the
medium voltage power transmission cable.
9. The time domain reflectometry system of claim 8, wherein the
on-line dielectrically insulated medium voltage power transmission
cable is an underground on-line dielectrically insulated medium
voltage power transmission cable.
10. The time domain reflectometry system of claim 8, wherein the
drive circuit and the receive circuit are configured to have an
impedance of greater than 500 ohms.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/820,886, filed Jun. 22, 2010, which claims
the benefit of U.S. Provisional Application No. 61/219,289, filed
Jun. 22, 2009, all the disclosures of which are hereby incorporated
by reference.
BACKGROUND
[0002] Transmission cables are intended to operate safely and
effectively over lifespans exceeding twenty years. However, because
of anomalies in the transmission cable due to manufacturing
defects, installation errors, localized imperfections, such as
insulation breakdown, transmission cables often suffer premature
breakdown. Should this occur during a critical period the
repercussions in terms of financial losses and customer
inconveniences can be quite severe. Therefore, with the
ever-increasing number of transmission cables being utilized
throughout the world, it is desirable that anomalies such as
faults, discharges, cable damage, and splices of transmission
cables be located without the necessity of physical tracing and
inspection.
[0003] A Time Domain Reflectometer (TDR) is one apparatus that can
be used to analyze a cable for anomalies, and more specifically, to
analyze the cable for changes in cable impedance in order to locate
such anomalies. A typical TDR transmits a pulse of electrical
energy onto a cable that includes two conductors separated by a
dielectric material. When the pulse encounters a change in the
impedance of the cable, part of the pulse's energy is reflected
back toward the TDR. The amplitude and polarity of this reflection
is proportional to the change in impedance. Such reflections are
usually displayed in graphical form on the screen of a typical TDR
whereby a technician can interpret the results and locate specific
cable anomalies. In particular, the time of propagation of the
pulse as well as the pulse shape can be used to identify and locate
the anomaly along the transmission cable.
SUMMARY
[0004] This summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This summary is not intended to identify
key features of the claimed subject matter, nor is it intended to
be used as an aid in determining the scope of the claimed subject
matter.
[0005] In accordance with an embodiment of the present disclosure,
a method is provided for testing a power system component for
anomalies. The method comprises capacitively coupling one or more
test sensors to an on-line insulated medium voltage power
transmission cable, generating a test pulse via a pulse generator
having an output impedance greater than 500 ohms, transmitting the
test pulse to at least one test sensor of the one or more test
sensors, capacitively transmitting the test pulse from the at least
one test sensor of the one or more test sensors onto the medium
voltage insulated power cable so that the test pulse travels along
the medium voltage insulated power cable, and capacitively
receiving a reflected pulse by one test sensor of the one or more
test sensors from the medium voltage insulated power cable. The
reflected pulse is one embodiment results from the test pulse
interfacing with an anomaly along the medium voltage insulated
power cable.
[0006] In accordance with another embodiment of the present
disclosure, a method is provided for testing a power system
component for anomalies. The method includes connecting, in
electrical communication, a pulse transmission line with a test
sensor housed in a medium voltage power cable termination elbow,
generating a test pulse and transmitting the test pulse to the test
sensor via the pulse transmission line, capacitively transmitting
the test pulse from the test sensor onto a medium voltage power
cable coupled to the medium voltage power cable termination elbow
so that the test pulse travels along the medium voltage power
cable, and capacitively receiving a reflected pulse by the test
sensor from the medium voltage power cable. The reflected pulse is
one embodiment results from the test pulse interfacing with an
anomaly along the medium voltage power cable or an electronic
component connected to the medium voltage power cable.
[0007] In accordance with another embodiment of the present
disclosure, a time domain reflectometry system is provided. The
system includes an on-line dielectrically insulated medium voltage
power transmission cable configured to carry medium voltage power
and a transmit circuit including a pulse generator configured to
generate a pulse. The transmit circuit is one embodiment is
configured to capacitively impart the pulse onto the medium voltage
power transmission cable. The system also includes a receive
circuit configured to capacitively receive a reflected pulse from
the medium voltage power transmission cable.
DESCRIPTION OF THE DRAWINGS
[0008] The foregoing aspects and many of the attendant advantages
of this disclosure will become more readily appreciated by
reference to the following detailed description, when taken in
conjunction with the accompanying drawings, wherein:
[0009] FIG. 1 is a schematic diagram of one embodiment of a TDR
system formed in accordance with aspects of the present
disclosure;
[0010] FIG. 2 is a block diagram of one embodiment of a computing
device employed by the TDR system of FIG. 1;
[0011] FIG. 3 is a schematic diagram of another embodiment of a TDR
system formed in accordance with aspects of the present
disclosure;
[0012] FIG. 4 is a schematic diagram of another embodiment of a TDR
system formed in accordance with aspects of the present disclosure;
and
[0013] FIG. 5 is a schematic diagram of another embodiment of a TDR
system formed in accordance with aspects of the present disclosure;
and
[0014] FIG. 6 is a schematic diagram of another embodiment of a TDR
system formed in accordance with aspects of the present
disclosure.
DETAILED DESCRIPTION
[0015] The detailed description set forth below in connection with
the appended drawings where like numerals reference like elements
is intended as a description of various embodiments of the
disclosed subject matter and is not intended to represent the only
embodiments. Each embodiment described in this disclosure is
provided merely as an example or illustration and should not be
construed as preferred or advantageous over other embodiments. The
illustrative examples provided herein are not intended to be
exhaustive or to limit the disclosure to the precise forms
disclosed. Similarly, any steps described herein may be
interchangeable with other steps, or combinations of steps, in
order to achieve the same or substantially similar result.
[0016] The following discussion proceeds with reference to examples
of transmission cable testing devices and methods. More
particularly, embodiments of the present disclosure are directed to
systems and methods that utilize Time Domain Reflectometers (TDRs)
for testing, and potentially analyzing, insulated transmission
cables, such a medium and low voltage power transmission cables,
twisted cable pairs, coaxial cable, etc., power equipment, such as
switchgears, transformers, electric motors, etc., and the like As
will be explained in more detail below, some embodiments of the
present disclosure provide a TDR system that tests an "on-line" or
"energized" power transmission cable by imposing a pulse of energy
onto the power cable and sensing the potential reflection signals
in a capacitive manner. In this way, technicians do not need to
take the power cable off line nor do they need access to the power
cable's central conductor.
[0017] As described herein, a Time Domain Reflectometer (TDR)
transmits a pulse of electrical energy onto a transmission cable,
such as a power transmission cable, that includes two conductors, a
power carrying conductor, and a neutral conductor, separated by a
dielectric material. When the electrical pulse encounters an
impedance change along the cable's length, part of the pulse's
energy is reflected back toward the TDR. By measuring, for example,
the amplitude and polarity of the reflected wave, the
proportionality of the impedance change can be determined.
Additionally, by measuring the time of propagation of the pulse,
the location of the impedance change can also be determined.
Typical anomalies that will cause an impedance change include but
are not limited to a change in the cable medium, splices, faults,
neutral corrosion, water damage to the insulation and/or shield,
and damage to the cable (e.g., broken conductors, shorted
conductors, smashed cables, cuts, etc.)
[0018] In the following description, numerous specific details are
set forth in order to provide a thorough understanding of exemplary
embodiments of the present disclosure. It will be apparent to one
skilled in the art, however, that many embodiments of the present
disclosure may be practiced without some or all of the specific
details. In some instances, well-known process steps have not been
described in detail in order not to unnecessarily obscure various
aspects of the present disclosure. Further, it will be appreciated
that embodiments of the present disclosure may employ any
combination of features described herein.
[0019] In accordance with several embodiments of the present
disclosure, a number of TDR systems are provided that improve the
quality and accuracy of information collected when propagating a
signal along a length of transmission cable in order to pinpoint
specific anomalies. Turning now to FIG. 1, there is shown a
schematic diagram of a conventional transmission cable, such as a
power cable C. As best shown in FIG. 1, the power cable C is being
tested by one embodiment of a TDR testing system, generally
designated 20, formed in accordance with aspects of the present
disclosure. In some embodiments, the TDR testing system may be
utilized to test "energized" or "on-line" power cables C. As used
herein, the term "energized" or "on-line" means that power is
presently being transmitted along the power cable C.
[0020] Still referring to FIG. 1, the system 20 comprises a
computing unit 24, a pulse generator 28, and a pulse
transmit/receive sensor 32. In use, the pulse generator 28, upon
instructions generated by the computing unit 24, generates a pulse
of energy that is transmitted over the power cable C via the
transmit/receive sensor 32. If the pulse encounters an anomaly as
it propagates down the power cable C, a reflection signal is
produced and transmitted back toward the transmit/receive sensor
32, where the signal is sensed by the transmit/receive sensor 32
and transmitted to the computing unit 24 to be processed and
displayed. In one embodiment, the signals received by the computing
unit 24 may be analyzed to determine the location of the anomaly,
the type of the anomaly, etc.
[0021] Referring to FIGS. 1 and 2, the components of the system 20
will now be described in more detail. As briefly described above,
the sensor 32 transmits a pulse of energy generated by the pulse
generator 28, and then senses any reflections of the transmitted
pulse. The sensor 32 may be a portable sensor for in-field data
acquisition and/or testing or fixed in place at a termination
location, such as a termination elbow. In one embodiment, the
sensor 32 is a portable, capacitive probe, such as a U-shaped
metallic (e.g., copper, etc.) probe. In use, the capacitive probe
is capacitively coupled to the power cable C, at a position, for
example, where the power cable is terminated. In embodiments that
are testing underground power cables, the capacitive probe is
capacitively coupled to the power cable C at a location where the
power cable is exposed (e.g., above ground, unearthed, etc.). Once
coupled to the power cable, the probe is capable of imposing a
pulse onto the power cable to be tested and sensing the reflection
signals due to anomalies and transmitting these signals to the
computing unit 24 for displaying, processing, and/or storage,
etc.
[0022] Referring now to FIG. 2, there is shown a block diagram of
one embodiment of the computing unit 24 suitable for use with the
system 20. The computing unit 24 comprises a processor 44, a memory
48, a display 52, and an I/O device 56 suitably interconnected via
one or more buses 60. The memory 48 may include read only memory
(ROM), random access memory (RAM), and storage memory. Examples of
ROM include a programmable ROM (PROM), an erasable programmable ROM
(EPROM), and an electrically erasable PROM (EEPROM). Examples of
storage memory include flash memory, a hard disk drive, a magnetic
disk drive for reading from or writing to a removable magnetic
disk, and an optical disk drive for reading from or writing to a
digital versatile disc (DVD), a compact disc rewriteable (CD-RW),
etc. The storage memory and their associated computer-readable
media provide non-volatile storage of computer readable
instructions, data structures, program modules, and data received
from the sensor 32. As used herein, the term processor is not
limited to integrated circuits referred to in the art as a
computer, but broadly refers to a microcontroller, a microcomputer,
a microprocessor, a programmable logic controller, an application
specific integrated circuit, and other programmable circuits, among
others.
[0023] A number of program modules may be stored in storage memory,
including one or more application programs 66, and program data.
One application program generates a control signal to be
transmitted to the pulse generator 28 to instruct the pulse
generator 28 to generate a pulse of energy. In one embodiment, the
control signal could be simply a trigger signal. This application
or a separate application may keep track of the time between the
generation of the pulse and the reception of any reflection
signals, sometimes referred to as the time of propagation, and may
calculate the velocity of propagation, if desired.
[0024] A technician may enter commands and information into the
computing device 24 through input devices (not shown) such as a
keyboard, joystick, potentiometers, switches, etc, which
communicate with I/O device 56. The I/O device 56 also communicates
with the sensor 32 for receiving signals therefrom. In one
embodiment, the computing unit 24, the pulse generator 28, and
optional input device, are housed in a unitary handheld TDR device
70, as shown in FIG. 1. The TDR device 70 is appropriately
connected to the neutral conductor of the power cable C.
[0025] In use, when the one or more applications are implemented,
either manually by input from a technician or automatically via
instructions by the processor 44 (e.g., time based instructions) a
pulse is generated at the pulse generator 28 and propagated down
the power cable C via the sensor 32. The sensor 32 is then able to
detect any reflection which occurs due to a change in impedance on
the power cable C. As the wave reflections are detected, the one or
more applications receive pulse information from the sensor 32 and
assimilate the information to be displayed in a graphical
representation on the display 52 in the time domain. The technician
of the system 20 is then able to interpret information from the
graphical representation of the anomalies detected on the power
cable C.
[0026] Turning now to FIG. 3, there is shown another embodiment of
a TDR testing system, generally designated 120, formed in
accordance with aspects of the present disclosure. The system 120
is substantially similar to the system 20 except for the
differences that will now be explained. As best shown in FIG. 3,
instead of the pulse generator 28 being integral with the TDR
device 70, along with the computing device 24, the pulse generator
28 may be a separate component, which is electrically coupled to
computing device 24 to receive controls signals therefrom. In one
embodiment, the pulse generator 28 is a current source pulse
generator and is electrically coupled to the transmit/receive
sensor 32 so as to provide the pulse generator 28 with a high
output impedance. In one embodiment, the output impedance of the
pulse generator 28 is greater than 500 ohms. In another embodiment,
the output impedance of the pulse generator 28 is greater than 1000
ohms.
[0027] Turning now to FIG. 4, there is shown another embodiment of
a TDR testing system, generally designated 220, formed in
accordance with aspects of the present disclosure. The system 220
is substantially similar to the system 120 except for the
differences that will now be explained. As best shown in FIG. 4,
the system 220 includes separate capacitively coupled transmit and
receive sensors 32A and 32B. The transmit sensor 32A is connected
in electrical communication with the pulse generator 28 for
transmitting a pulse of energy along the power cable C. The receive
sensor 32B is connected in electrical communication with the
computing device 24. In one embodiment, the pulse generator 28 is a
voltage source pulse generator and is electrically coupled to the
transmit sensor 32A so as to provide the pulse generator 28 with a
low output impedance.
[0028] Turning now to FIG. 5, there is shown another embodiment of
a TDR testing system, generally designated 320, formed in
accordance with aspects of the present disclosure. The system 320
is substantially similar to the system 220 except for the
differences that will now be explained. As best shown in FIG. 5, an
amplifier 378 is electrically connected between the capacitive
receive sensor 32B and the computing device 24. In one embodiment,
the amplifier 378 has a high input impedance. In one embodiment,
the input impedance is more than 500 ohms. This reduces the signal
loss through the sensor's capacitive connection resulting in an
improved received signal to noise ratio. In another embodiment, the
signal transmission line between the amplifier 378 and the receive
sensor 32B is less than or equal to about 2 inches. This eliminates
any transmission line effects between the sensor 32B and the
display which would corrupt the shape of the received signal. A
termination matching resistor 380, such as a 50.OMEGA. resistor,
may also be employed to drive the 50.OMEGA. transmission line
connected to the display's 50.OMEGA. input impedance. This
maintains the signal integrity by eliminating signal
reflections.
[0029] Turning now to FIG. 6, there is shown another embodiment of
a TDR testing system, generally designated 420, formed in
accordance with aspects of the present disclosure. The system 420
is substantially similar to the system 20 except for the
differences that will now be explained. As shown in FIG. 1, the
sensor 32 of the TDR system 20 is capacitively coupled to a power
cable C to be tested. In contrast to FIG. 1, the sensor 432 of the
TDR system 420 shown in FIG. 6 is capacitively coupled to the power
cable C at a termination elbow T. In that regard, the sensor 432 is
formed integrally with the housing of the termination elbow T and
positioned so as to be capacitively coupled to the power cable C
when the power cable is connected to the termination elbow. In one
embodiment, the sensor 432 is part of a capacitive port on the
termination elbow T.
[0030] The principles, representative embodiments, and modes of
operation of the present disclosure have been described in the
foregoing description. However, aspects of the present disclosure
which are intended to be protected are not to be construed as
limited to the particular embodiments disclosed. Further, the
embodiments described herein are to be regarded as illustrative
rather than restrictive. It will be appreciated that variations and
changes may be made by others, and equivalents employed, without
departing from the spirit of the present disclosure. Accordingly,
it is expressly intended that all such variations, changes, and
equivalents fall within the spirit and scope of the present
disclosure, as claimed.
* * * * *