U.S. patent application number 12/091338 was filed with the patent office on 2009-11-26 for fault protection system and method for an electrical power distribution system.
This patent application is currently assigned to S & C Electric Co.. Invention is credited to Raymond P. O'Leary, Douglas M. Staszesky, Thomas J. Tobin.
Application Number | 20090290275 12/091338 |
Document ID | / |
Family ID | 37709399 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090290275 |
Kind Code |
A1 |
Staszesky; Douglas M. ; et
al. |
November 26, 2009 |
Fault Protection System and Method for an Electrical Power
Distribution System
Abstract
A fault protection system for an electrical power distribution
system and a method of configuring and operating a fault protection
system for an electrical power distribution system accepts device
fault protection parameters, such as the
time-current-characteristics (TCCs), of boundary devices, and
selects and sets fault protection parameters for one or more fault
protection devices, such as fault-interrupters, that thus
coordinate with the boundary devices. Fault protection parameter
selection for each fault protection device may occur automatically,
and each device may reconfigure its fault protection parameters
based upon changes in the electrical power distribution system, for
example, as the result of fault isolation and/or service
restoration.
Inventors: |
Staszesky; Douglas M.;
(Glenview, IL) ; O'Leary; Raymond P.; (Evanston,
IL) ; Tobin; Thomas J.; (Northbrook, IL) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP (S & C)
233 S. WACKER DRIVE, SUITE 6300, SEARS TOWER
CHICAGO
IL
60606-6357
US
|
Assignee: |
S & C Electric Co.
Chicago
IL
|
Family ID: |
37709399 |
Appl. No.: |
12/091338 |
Filed: |
October 3, 2006 |
PCT Filed: |
October 3, 2006 |
PCT NO: |
PCT/US06/38470 |
371 Date: |
October 29, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60731571 |
Oct 28, 2005 |
|
|
|
60732475 |
Nov 2, 2005 |
|
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Current U.S.
Class: |
361/63 |
Current CPC
Class: |
G01R 31/085 20130101;
H02H 3/006 20130101; H02H 7/263 20130101; H02H 7/261 20130101; H01H
83/20 20130101; H02H 3/08 20130101; H02H 7/30 20130101 |
Class at
Publication: |
361/63 |
International
Class: |
H02H 7/30 20060101
H02H007/30 |
Claims
1. A fault protection system, comprising: a distribution line, the
distribution line connecting a source via a first boundary
protection device to a load via a second boundary protection
device; a fault protection device segmenting the line between the
first boundary protection device and a second boundary protection
device; the fault protection device being operable to isolate the
source from a fault in the distribution line between the fault
protection device and the load; the fault protection device
including a controller, a memory coupled to the controller and a
fault isolation operator coupling a source side of the distribution
line to a load side of the distribution line, the fault isolation
operator being responsive to the controller; the controller being
operable to receive fault operating characteristic data relating to
the boundary protection devices and further being operable upon the
fault operating characteristic data to determine a fault operating
parameter for the fault protection device and to store the fault
operating parameter in the memory; such that, in operation the
fault isolation operator is operable responsive to the controller
to provide fault isolation in the distribution line based upon the
fault operating parameter.
2. The fault protection system of claim 1, wherein the fault
operating characteristic data comprises time-current-characteristic
(TCC) data.
3. The fault protection system of claim 2, wherein the
time-current-characteristic data is expressed as a function of
fault operating characteristic data of the boundary protection
device.
4. The fault protection system of claim 2, wherein the
time-current-characteristic data is expressed as a data set
defining a nominal response, minimum response, or maximum clear
time-current-characteristic of the boundary protection device.
5. The fault protection system of claim 1, the controller being
operable to determine a validity of the fault operating parameter
in relationship to the fault operating characteristic data of the
boundary devices.
6. The fault protection system of claim 1, comprising a second
fault protection device segmenting the distribution line between
the boundary protection devices; the controller being further
operable to receive fault operating characteristic data relating to
the second fault protection device.
7. The fault protection system of claim 6, each of the fault
protection device and the second fault protection device comprising
respective communication devices, the communication devices being
operable to communicate the fault operating characteristic data
from the second fault protection device to the first fault
protection device.
8. The fault protection device of claim 6, a second fault operating
parameter associated with the second fault protection device, the
first fault operating parameter and the second fault operating
parameter being determined to provide coordinated operation of the
fault protection device and the second fault protection device.
9. The fault protection device of claim 8, the fault protection
device being operable to communicate a message to the second fault
protection device upon operation of the fault protection device,
the second fault protection device being operable to modify the
second fault operating parameter responsive to the message such
that the second fault protection device remains coordinated with
the first fault protection device.
10. The fault protection device of claim 9, wherein the message is
a delay message and wherein in response to the delay message the
second fault protection device time shifts its
time-current-characteristic.
11. The fault protection device of claim 8, wherein the fault
protection device and the second fault protection device operate as
a coordinated team.
12. A method of providing coordinated fault protection for a
distribution line coupling a source to a load, a boundary
protection device being disposed on the distribution line between
the source and the load and a fault protection device being
disposed on the distribution line between the boundary protection
device and the load; the method comprising: receiving fault
operating characteristic data relating to the boundary protection
device; determining a load path from the source to the load, the
load path including the boundary protection device and the fault
protection device; determining a fault operating parameter for the
fault protection device based at least in part upon the fault
operating characteristic date of the boundary protection device;
and activating a fault operating characteristic within the fault
protection device based upon the determined fault operating
parameter.
13. The method of claim 12, the fault protection device comprising
a plurality of fault protection devices being disposed within the
load path, the method comprising: propagating fault operating
characteristic data for each of the plurality of fault protection
devices to each other of the plurality of fault protection devices;
generating a fault operating parameter for each of the plurality of
fault protection devices based upon the fault operating
characteristic data of the boundary device and the propagated fault
operating characteristic data of the plurality of fault protection
devices; and activating a fault operating characteristic within
each of the plurality of fault protection devices based upon the
determined fault operating parameter for the respective fault
protection device.
14. The method of claim 12, comprising: wherein the fault operating
parameter of each of the plurality of fault protection devices is
determined to provide coordinated operation of the plurality of
fault protection devices with respect to each other and the
boundary device.
15. The method of claim 12, comprising: determining a first fault
protection device has an invalid fault protection parameter;
setting the fault protection parameter of the first fault
protection device to be the same as the fault protection parameter
of a second fault protection device, the fault protection parameter
of the second fault protection device being determined to be
valid.
16. The method of claim 15; comprising: coordinating the fault
protection operation of the first fault protection device and the
second fault protection device.
17. The method of claim 16, wherein the coordinating comprises
sending a message from the first fault protection device to the
second fault protection device upon fault protection operation of
the first fault protection device, the message affecting
coordinated operation of the second fault protection device with
respect to the first fault protection device.
18. The method of claim 17, the message comprising a delay message;
the second fault protection device delaying its fault protection
characteristic responsive to the delay message.
19. The method of claim 17, the message comprising a delay message
propagated to each of the plurality of fault protection devices
from the first fault protection device to the boundary device.
20. The method of claim 17, the message comprising multiple delay
messages, the number of delay messages corresponding to a number of
fault protection devices sharing a fault protection
characteristic.
21. The method of claim 16, wherein coordinating comprises:
determining a prior operation of the first fault protection device
to a fault; and delaying operation of the second fault protection
device to the fault responsive to the operation of the first fault
protection device.
22. The method of claim 16, wherein coordinating comprises:
determining substantially simultaneous operation of the first fault
protection device and the second fault protection device to a
fault; and sequentially resetting the first fault protection device
and the second fault protection device to restore service.
23. The method of claim 22, wherein sequential resetting comprises
first resetting the closest to the source of the first fault
protection device and the second fault protection device.
24. The method of claim 22, wherein sequential resetting comprises
resetting one of the first fault protection device and the second
fault protection device, and testing by the other of the first
fault protection device and the second fault protection device a
persistence of the fault.
25. The method of claim 24, comprising modifying the fault
operating parameter and hence the fault operating characteristic of
the one of the first fault protection device and the second fault
protection device during the testing to temporarily prevent its
operation during the testing.
26. The method of claim 16, wherein coordinating comprises:
determining an operation of the first fault protection device to a
first fault type; determining a second fault type to exist at the
second fault protection device, and operating the second fault
protection device responsive to the second fault type; and
sequentially resetting the first fault protection device and the
second fault protection device to restore service.
27. In a fault protection system for an electrical power
distribution system, a method of configuring the fault protection
system comprising: obtaining an operating parameter of a
non-configurable device; determining a response characteristic of a
fault protection device within a current path from a source to a
load including the non-configurable device and the fault protection
device; determining a validity of the response characteristic;
setting the fault protection device to operate in accordance with
the response characteristic.
28. The method of claim 27, the non-configurable device comprising
one of a source boundary device and load boundary device.
29. The method of claim 27, wherein determining a response
characteristic comprises determining a time-current-characteristic
of the fault protection device relative to the operating parameter
of the non-configurable device.
30. The method of claim 29, wherein the time-current-characteristic
is based upon a minimal clearance between a maximum total clearing
time of a downstream device and a minimum pickup time of an
upstream device, the downstream device and the upstream device
being relative to the fault protection device.
31. The method of claim 27, a plurality of fault protection devices
being disposed in the current path, the method comprising providing
a unique operating characteristic for each of the plurality of
fault protection devices.
32. The method of claim 27, a plurality of fault protection devices
being disposed in the current path, the method comprising providing
a unique operating characteristic for a first portion of the fault
protection devices, providing a common operating characteristic to
a second portion of the fault protection devices, and providing
coordination of the operation for the second portion of the fault
protection devices.
33. The method of claim 27, wherein the common operating
characteristic comprises a maximum protection characteristic
selected from a group of characteristics determined for each fault
protection device of the second portion of fault protection
devices.
34. The method of claim 33, wherein the coordination comprises
sending a message from a first fault protection device of the
second portion to a second fault protection device of the second
portion upon fault protection operation of the first fault
protection device, the message affecting coordinated operation of
the second fault protection device with respect to the first fault
protection device.
35. The method of claim 34, the message comprising a delay message;
the second fault protection device delaying its fault protection
characteristic responsive to the delay message.
36. The method of claim 32, wherein coordination comprises:
determining a prior operation of a first fault protection device of
the second portion to a fault; and delaying operation of a second
fault protection device of the second portion to the fault
responsive to the operation of the first fault protection
device.
37. The method of claim 32, wherein coordination comprises:
determining substantially simultaneous operation of a first fault
protection device and a second fault protection device for the
second portion to a fault; and sequentially resetting the first
fault protection device and the second fault protection device to
restore service.
38. The method of claim 37, wherein sequential resetting comprises
first resetting the closest to the source of the first fault
protection device and the second fault protection device.
39. The method of claim 37, wherein sequential resetting comprises
resetting one of the first fault protection device and the second
fault protection device, and testing by the other of the first
fault protection device and the second fault protection device a
persistence of the fault.
40. The method of claim 39, comprising modifying the fault
operating parameter and hence the fault operating characteristic of
the one of the first fault protection device and the second fault
protection device during the testing to temporarily prevent its
operation during the testing.
40. The method of claim 32, wherein coordinating comprises:
determining an operation of a first fault protection device of the
second portion to a first fault type; determining a second fault
type to exist at a second fault protection device of the second
portion, and operating the second fault protection device
responsive to the second fault type; and sequentially resetting the
first fault protection device and the second fault protection
device to restore service.
41. The method of claim 27, wherein determining a response
characteristic comprises determining a response characteristic for
the fault protection device based upon each of plurality of
operating configurations of the fault protection device.
42. The method of claim 41, wherein setting the fault protection
device to operate in accordance with the response characteristic
comprises selecting a maximum response characteristic from each of
the response characteristics for the fault protection device
corresponding to the plurality of operating conditions.
43. The method of claim 42, wherein the plurality of operating
configurations comprise multiple load paths to a source.
44. The method of claim 42, wherein the plurality of operating
configurations comprise a load path to each of a plurality of
sources.
45. The method of claim 42, wherein the plurality of operating
configurations comprise multiple current ranges.
46. The method of claim 42, wherein the plurality of operating
configurations comprise multiple terminal connections to the fault
protection device.
Description
TECHNICAL FIELD
[0001] This patent relates to the control of an electric power
distribution system, and more specifically to the use of
intelligent autonomous nodes for isolating faulted sections of
distribution lines, reconfiguring, and restoring service to end
customers (circuit reconfiguration), and improving circuit
protection.
BACKGROUND
[0002] Power distribution systems typically include distribution
feeders (ranging from approximately 4 KV to 69 KV) originating in
power distribution substations and leading to the source of supply
for end customers of an electrical supply utility or agency.
Regulatory service provision requirements, cost and competitive
pressures create requirements for lower cost, modular, standardized
equipment, which can be installed, operated and maintained with
minimal labor and human supervision.
[0003] Failures of the distribution feeder (faults) occur due to
downed power lines, excavation of underground cable or other causes
and are typically detectable by sensing excess (short
circuit/overcurrent) current, and occasionally by detecting loss of
voltage. In distribution systems, it is sometimes the case that a
loss of voltage complaint by the customer is the means by which the
utility senses the outage in order to respond by dispatching a crew
to isolate the fault and reconfigure the distribution system. The
typical devices for isolating these faults are circuit breakers
located primarily in distribution substations and fuses located on
tap lines or at customer transformers. The substation breakers are
generally provided with reclosing relays that cause the breaker to
close several times after the breaker has detected an overcurrent
condition and tripped open. If during any of these "reclosures",
the fault becomes undetectable, service is restored and no extended
outage occurs. Particularly on overhead distribution lines,
temporary arcing due to wind, lightening, etc. causes many faults.
Thus, the majority of faults are cleared when the breaker opens and
service is restored on the automatic reclose. Alternatively, after
some number of reclosure attempts, if the overcurrent condition
continues to be present, the recloser goes into a "lockout" state
which prevents further attempts to clear the fault.
[0004] Although utility acceptance of more sophisticated automation
solutions to fault isolation and reconfiguration has been limited
but continues to increase, many methods have been developed and
marketed. The most primitive methods have typically involved
placing control equipment and switchgear at strategic points in the
power distribution grid and coordinating their operation entirely
with the use of circuit parameters sensed and operated on locally
and independently at each point. More sophisticated methods have
been developed for isolating/reconfiguring these circuits by
communicating information sensed locally at the strategic points to
a designated, higher level control entity(s). Utilizing
intelligent, distributed control methodologies, several methods
have been developed to isolate/reconfigure distribution circuits
without the need for the higher-level control entity(s). In systems
implementing these methods, information is sensed and processed
locally, acted on as much as possible locally, and then shared with
other cooperating devices to either direct or enhance their ability
to take action. Examples of these methods include versions of the
IntelliTEAM.RTM. product available from S & C Electric Company,
Chicago, Ill.
[0005] Systems, such as the IntelliTEAM.RTM. products and the
systems described in commonly assigned U.S. Pat. No. 6,697,240, the
disclosure of which is hereby expressly incorporated herein by
reference, provide methodologies and related system apparatus for
using and coordinating the use of information conveyed over
communications to dynamically modify the protection characteristics
of distribution devices (including but not limited to substation
breakers, reclosing substation breakers, and line reclosers). In
this way, overall protection and reconfigurability of the
distribution system or "team" is greatly enhanced. Devices within
the system recognize the existence of cooperating devices outside
of the team's domain of direct control, managing information from
these devices such that more intelligent local decision making and
inter-team coordination can be performed. This information may
include logical status indications, control requests, analog values
or other data.
[0006] Still, when restoration systems reconfigure distribution
feeders, for the purpose of fault isolation and/or load
restoration, the coordination between fault protection devices,
such as interrupters, used to segment the feeder, can be destroyed.
Thus, an automated method to reconfigure the protection settings to
maintained coordination is desired. Further, benefits may be
obtained where the fault protection devices are set so they
coordinate with other devices that may or may not be automatically
set, for example, boundary devices such as circuit breakers that
protect the distribution feeder and fuses that protect loads that
are tapped off the feeder.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 schematic diagram illustrating a portion of an
electrical power distribution system incorporating configurable
fault protection devices.
[0008] FIG. 2 is a block diagram of a fault protection device.
[0009] FIG. 3 is a plot illustrating time-current-characteristics
for devices of an electrical power distribution system that may be
used to configure fault protection devices.
[0010] FIG. 4 is a schematic diagram illustrating a portion of an
electrical power distribution system incorporating a series of
fault protection devices.
[0011] FIG. 5 is a plot illustrating time-current-characteristics
for a series devices of an electrical power distribution system
that may be used to configure fault protection devices.
[0012] FIG. 6 is a flow diagram illustrating a method of
configuring fault protection devices in an electrical power
distribution system in accordance with one of the herein described
embodiments.
DETAILED DESCRIPTION
[0013] A fault protection system for an electrical power
distribution system and a method of configuring and operating a
fault protection system for an electrical power distribution system
accepts device fault protection parameters, such as the
time-current-characteristics (TCC's), of boundary devices, and
selects and sets fault protection parameters for one or more fault
protection devices, such as fault-interrupters, that thus
coordinate with the boundary devices. Fault protection parameter
selection for each fault protection device may occur automatically,
and each device may reconfigure its fault protection parameters
based upon changes in the electrical power distribution system, for
example, as the result of fault isolation and/or service
restoration.
[0014] FIG. 1 shows a simplified view of a portion of an exemplary
electrical power distribution system that includes fault protection
devices that can be configured and controlled by one or more of the
herein described embodiments. The distribution system comprises a
plurality of sources of electrical power, one shown as source 102,
connected to a plurality of users or loads 104 (e.g., factories,
homes, etc.) through an electrical distribution line 106 such as
conventional electrical power lines.
[0015] Distribution line 106 has a plurality of fault protection
devices, devices 1, 2, 3 and 4 placed at predetermined points along
the line 106. The depiction of the number of sources, users, lines
and devices in FIG. 1 is arbitrary and there may be many different
configurations and virtually any number of each of these components
in any given distribution system. Also depicted are a number of
boundary protection devices including breaker 108 and fuses
110.
[0016] FIG. 2 illustrates an embodiment of a fault protection
device 200. A distribution line, such as line 106, passes through a
fault isolation operator, e.g., a fault interrupter 204, which can
open and close the distribution line 106 at this point to isolate a
fault in the line from the source. In other embodiments, the fault
isolation operator may be any suitable device or devices capable of
performing power sensing, control or conditioning functions such as
voltage regulation (voltage regulators), reactive power control
(switched capacitor banks), fault sensing, etc. in conjunction with
fault isolation. It will be appreciated that the device 200 may
also be of a type for controlling two (dual), three, or more
switches, with customer loads or alternate sources between the
fault interrupters. In this case, the distribution line or lines
106 would pass through two or more fault interrupters 204 which can
open and close independently under the control of the single device
200. In this context, device 200 is a single device from the
standpoint of communications, but is multiple devices from the
standpoint of the power system and the control and fault protection
algorithms. In this circumstance, the information flow is
unchanged, but the communication step is simply bypassed.
[0017] A controller 206 controls the fault interrupter 204. The
controller 206 includes a control computer or suitable processing
device 208, a display 202, and an associated memory 210. The memory
210 may store, among other data, the programming to control the
device 200, programming to determine configuration and performance
data, the configuration data for the device, and a database of
device records relating to other devices in the system.
[0018] Those skilled in the art will recognize that fault
interrupter 204 can have different operating capabilities which may
enhance or detract from its ability to participate in circuit
reconfiguration. For example, the lowest-cost switches may not be
capable of interrupting high currents, or may not be outfitted with
both voltage and current sensors. Those skilled in the art will
also recognize that the device 200 may be programmed not to
interrupt the distribution line under high interrupting currents
(sectionalizing switch control), or alternatively may be programmed
as a "circuit protective device" (recloser or breaker). When
programmed as a protective device, the switch is controlled in
accordance with operating parameters such as fault protection
parameters. For example, the switch, if normally closed, it may be
opened under overcurrent conditions (fault current) to prevent fire
or damage to the circuit or to customer equipment, and also for
safety concerns.
[0019] The control computer 208 is connected to an AC waveform
processor 212. The AC waveform processor 212 is connected through a
field interface connector 214 to the distribution line 106. This
allows the processor to measure various parameters of the
electricity on the distribution line 106 such as, voltage and
current, digitally convert them, and send them to the control
computer for processing, communications, or storage in memory.
[0020] The digital I/O interface 216 is connected to the control
computer 208, the fault interrupter 204 and the distribution line
106. The digital I/O interface 216 allows the controller 206 to
receive switch position sensing information and other inputs, and
to output control outputs to the switch.
[0021] The communications device 218 is connected to the control
computer 208 and allows it to communicate with other devices on the
system through suitable communications channels. The communications
device 218 can be connected to any communications network that is
conveniently available and has the desired characteristics. For
example, a Metricom Radio network may be used. An optional
communications device 220 may be included in the device 200. An
example of such a secondary communication option may be a SCADA
gateway. Power is supplied to the device 200 through a power
supply/battery backup 222. The battery can be charged from solar
power, an AC potential transformer, or from power supplied through
the voltage sensors.
[0022] Each of the devices 200 is connected to a suitable
communications channel (not depicted). Any type of communications
channel can be used. For example, the communications channel may be
telephone, radio, the Internet, or fiber optic cable.
[0023] The fault operating parameters of the devices 200 may be set
so that operation of each individual device 200 in accordance with
the fault operating parameters coordinates with the other devices
and boundary devices such as breakers that protect the distribution
feeder(s) and fuses that protect load(s) that are tapped off of the
feeder. That is, the fault operating characteristic of each of the
devices 200 is based upon one or more fault protection parameters
set within the device. The fault protection parameters may be
selected in relationship to the other devices in the system, and
particularly devices that do not have adjustable or settable fault
protection characteristics, so that operation of the fault
protection device coordinates with operation of the other devices
to better facilitate fault isolation and service restoration. For
example, the fault protection operating characteristics of the
device 200 may include a time-current-characteristic (TCC)
operating curve that is established at least in view of TCC curves
associated with boundary devices within the system and potentially
other fault protection devices within the systems.
[0024] FIG. 3 illustrates exemplary TCC curves that may be used to
establish the fault protection parameters and hence the fault
operating characteristics of the device 200. FIG. 3 illustrates a
TCC curve 300 for a substation breaker, such as breaker 108 shown
in FIG. 1. The curve 300 illustrates three different
characteristics of the breaker 108: the shortest response time for
the breaker at a given current (minimum pickup) 300c, the nominal
response time for the breaker at a given current (nominal pickup)
300a, and a maximum time to clear 300b, which takes into account
tolerances of the current sensors, control, the fault-interrupter,
and the load that may be tapped between the breaker and the
fault-interrupter and a desired margin. The curves 300a, 300b and
300c make up the complete TCC 300 for the breaker.
[0025] To coordinate with the breaker, a fault protection device
may have a TCC such as that illustrated by the TCC 302 depicted in
FIG. 3. The curve 302 illustrates the fault protection device
nominal pickup 302a, its minimum pickup 302b and its maximum time
to clear 302c. The maximum time to clear 302c may be selected to be
below the minimum pickup of upstream devices, such as the breaker,
and as shown in FIG. 3 the maximum time to clear 302c is set below
the minimum pickup 300a of the breaker. The band between the
minimum pickup 302a and the maximum time to clear 302c is a
function of the operating characteristics of the fault protections
devices, and may generally be made to be tighter than the upstream
device by providing accurate sensing, and an electronic control.
For example, fast operating fault interrupters narrow the band
between the maximum time to clear and the nominal/minimal response
curves.
[0026] In addition to coordination with upstream devices, the fault
protection device may be made to coordinate with downstream
devices, such as fuses. To coordinate with a downstream device, the
minimum pickup of the fault protection device should be longer than
the maximum clearing time of the downstream device. FIG. 3
illustrates a TCC curve 304 for a fuse device having a maximum
clearing characteristic illustrated by the curve 304a and a minimum
clearing characteristic illustrated by the curve 304b. As can be
seen from FIG. 3, the minimum pickup 302a of the fault protection
device is longer than the maximum clearing time 304a of the
downstream device, in this example, a fuse.
[0027] It is possible to specify the TCC of a fault protection
device as a function of the characteristics of the device and the
devices with which it will coordinate. Exemplary device
characteristics may include: curve type (e.g., inverse, very
inverse, U/C 1 through 5, etc.), time dial setting, minimum pickup
current and coordination requirements. The coordination requirement
may take the form of a coordination time interval (CTI) or device
tolerances such as relay tolerance, current transformer (CT)
tolerance and relay over-travel characteristics. Expressed as a
function, the TCC may be stated as:
t = TD [ k ( I / I pu - 1 ) .alpha. + c ] ; ( a ) ##EQU00001##
where TD is the time-dial setting; I.sub.pu, is the pickup current;
and the constants k, .alpha., and c are determined by the specified
relay curve.
[0028] The fault protection device TCC may assume the same shape
(i.e.; the constants, k, .alpha., and c are the same). However, the
pickup current and time-dial are reduced by a factor, to ensure
coordination and shifted in time (down), to account for the
clearing time of the device, margin, and any minimum or fixed
tolerance. Thus the fault protection device TCC may have the
form:
t = TD ' [ k ( I / I pu ' - 1 ) .alpha. + c ] - TS . ( b )
##EQU00002##
The constants k, .alpha., and c are the same as root TCC set forth
in equation (a). TD', I'.sub.pu, & TS depend on the factors set
forth in Table 1.
TABLE-US-00001 TABLE 1 Parameter Determining factors I'.sub.pu
relay/control current tolerance of the device and the upstream
device CT/sensor tolerance of the device and the upstream device
Load current effect TD' relay/control time tolerance of the device
and the upstream device TS fixed or minimum time error of the
device and the upstream device maximum device interrupting time
margin
[0029] Alternatively, a fault protection device TCC may be
specified as a set of data that define the nominal TCC curve. In
this case, the fault-interrupter TCC is expressed as a
corresponding data set from points of the breaker TCC modified by
multiplying by a current & time factor and additionally
subtracting a time-shift term. The factors and time-shift term may
be determined as set forth in Table 2.
TABLE-US-00002 TABLE 2 Constant Determining items Current
relay/control current tolerance of the device factor and the
upstream device CT/sensor tolerance of the device and the upstream
device Load current effect Time factor relay/control time tolerance
of the device and the upstream device Time term fixed or minimum
time error of the device and the upstream device maximum device
interrupting time margin
[0030] Once a fault protection device curve is generated, its
useability must be validated. With respect to load protection
coordination, the relevant range of current is defined by the
minimum operating current of the device and the maximum available
fault current. For all currents in the relevant range, if the
minimum operating time of the fault protection device is not
greater than the maximum clearing time of the load protection
device, the fault protection device TCC is invalid. Additionally,
with respect to inrush current withstand capability, if the minimum
operating time of the fault protection device at a specified
multiple of the minimum operating current is less than a time
value, the TCC is invalid. The time value may be based upon typical
time/current characteristics of inrush currents (e.g., 25 times
current for 0.01 seconds or 10 times current for 0.1 seconds). In
connection with the fault protection device 200, after determining
the device TCC, the controller may check the validity of the TCC
and provide a warning of mis-coordination or indication of proper
coordination by communicating a message via the communication
device 218 or providing a message in the display 202.
[0031] The method may be repeated to generate a TCC for each of
several series fault protection devices. FIG. 4 illustrates a
series of fault protection devices, e.g., fault interrupters,
406-410 segmenting a feeder line 400 coupled to a source 402 via a
source protection device, e.g., breaker 404. Loads, e.g., load 412
protected by fuse 414, may extend laterally from any of the
segments.
[0032] FIG. 5, illustrates fault protection characteristic curves,
i.e., the TCC of several of the fault protection devices disposed
between a source protection device and a load protection device. As
shown in FIG. 5, the TCC 504, 506 and 508 for a plurality of fault
protection devices is disposed between the breaker TCC 500 and the
fuse TCC 502. Provided any given fault protection device TCC
resides between the upstream device TCC and the downstream device
TCC, the fault protection device TCC is considered valid. At some
point, however, the generated TCC for a fault protection device
will no longer coordinate with the downstream fuses, and as
illustrated in FIG. 5, the TCC 508 includes a portion that overlaps
the fuse TCC 502. Under this circumstance, several supplemental
coordination methods may be utilized. This is described following
the discussion of a method 600 (FIG. 6) to generally coordinate
fault protection devices.
[0033] Given the system of fault protection devices 406-410, each
having suitable communication capability, such as that described
above in connection with the device 200, fault protection
characteristics for each device may be coordinated between the
fault protection devices and any boundary devices. FIG. 6
illustrates in flow chart form a method 600 of coordinating fault
protection devices. The method has application to systems with
multiple sources and loads. Each device preferably includes a
control program stored in its memory to allow it to operate to
automatically generate fault protection characteristics.
[0034] For the method 600, it is assumed the boundary devices,
e.g., breakers, fuses, and the like, do not have communication
capability and are unable to communicate to other devices in the
system their respective fault protection characteristics, such as
the their TCC's. Boundary fault protection characteristic
information is therefore loaded into the communication capable
fault protection devices. It may be sufficient to load the boundary
fault protection characteristic data to a single communication
capable fault protection device and the information propagated from
that device, or the information may be loaded to each individual
fault protection device. Moreover, non-communication capable
devices are not limited to boundaries. In such a case, the fault
protection characteristics of the non-communicating, non-boundary
fault protection device is also loaded and propagated. This process
is illustrated in FIG. 6 at blocks 604 and 606.
[0035] With the non-communicating fault protection device
information loaded, fault protection characteristic propagation to
all communication fault protection devices occurs each time a
communicating fault protection device is installed, the system is
reconfigured or a status of a fault protection device changes, 608.
Given a system configuration, all possible paths from sources to
loads are considered as a default, 610. Fewer than all possible
paths may be considered, and if certain paths are to be excluded,
such information may be retained within the fault protection
devices and/or communicated to the fault protection devices.
[0036] Each active, communicating fault protection device
propagates its own fault protection characteristics to each other
communicating fault protection device. Fault protection devices
with closed paths back to a source may be considered active. The
active status of a fault protection device may therefore change
based upon the opening or closing of another fault protection
device, thus creating or breaking a path to a source for that fault
protection device.
[0037] As noted above at 608-612 of the method 600, propagation of
fault protection characteristics occurs whenever a fault protection
device is installed in the system, the system is reconfigured or a
fault protection device changes it status. The propagation may
occur by having a fault protection device send its fault protection
characteristic information to the fault protection devices
connected to it. When a fault protection device receives a fault
protection characteristic it may generate a new fault protection
characteristic based upon the received information, 614 and propose
new fault protection parameters. Prior to proposing the new fault
protection parameters, however, it may check to ensure that further
propagation will not create a looped path, and during propagation
the fault protection device may add its name to the path back to
the source. Referring to FIG. 1, each fault protection parameter
may carry a designation 112 that identifies the fault protection
device, the directionality of the fault protection parameter, the
source name, the number of devices in the path back to the source
and the names of the devices in the path back to the source. After
generating the new fault protection parameter, it then propagates
the newly generated fault protection parameter to fault protection
devices connected to it. It will also propagate its own close or
open status.
[0038] All fault protection devices in a closed path to a source
are considered active and activate an appropriate fault protection
parameter, 616. A fault protection device may have multiple paths
to a source or to multiple sources. The fault protection device may
determine a fault protection parameter for each possible path and
for each possible direction of the path back to the source.
Moreover, the power distribution system may operate at multiple
current ranges and/or multiple sources may provide current in
different current ranges. The response characteristic of the fault
protection device may be current dependent, and thus, it may
further be possible to specify fault protection parameters based
upon a current range or multiple fault protection parameters for
multiple current ranges. Additionally, each fault protection device
may have multiple terminals. Separate fault protection parameters
may be established for each terminal of the fault protection
device. Thus, each fault protection device may have more than one
fault protection parameter associated with it based upon the number
of paths and direction of paths back to sources, the number of
connected terminals with paths back to sources and various possible
current ranges. In implementing any one of the possible fault
protection parameters, the fault protection device may implement
the most onerous or maximum protection fault protection parameter,
typically the fault protection characteristic providing the fastest
fault protection response time.
[0039] The process of automatically updating fault protection
device parameters repeats responsive to installation of new
devices, changes in the system configuration, a change in the
status of one or more fault protection devices, for example, as a
result of a fault protection device operating to isolate a fault or
to restore service, 610. In this manner, the operation of the fault
protection devices remain continuously coordinated.
[0040] The fault protection devices may include programming and
implement functionality to allow a predicted status to be
propagated just prior to the device changing to that status. For
example, if the device is open and is about to close, it may
propagate its closed status before closing thus causing a
system-wide coordination of the fault protection devices prior to
its actual closing. Furthermore, fault protection devices may
periodically propagate their status, again causing a system-wide
coordination update, thus correcting any errors.
[0041] FIG. 5 illustrates how fault protection characteristics,
i.e., TCC's of several fault protection devices may be precisely
fit between the corresponding TCC's of a source device and a load
device. However, the TCC 508 overlaps the load device TCC 504, and
thus does not provide the required coordination, and is invalid. In
this instance, the device associated with the TCC 508, e.g., with
respect to FIG. 4 the device 410, may check the next preceding
device, e.g, the device 409 associated with the curve 506. Because
the TCC 506 does coordinate, the TCC 506 may be adopted by the
device 410 in place of the TCC 508. While the device 410 is now
coordinated with the rest of the system, it is no longer
coordinated with the device 409. However, additional capability may
be provided to ensure coordination between the devices 409 and 410
using the same TCC 506.
[0042] An approach to provide coordination between fault protection
devices using the same or substantially similar TCC's is to use the
communication capability of the fault protection devices. In one
possible scheme, all fault protection devices that detect a fault
signal the next upstream fault protection device. Referring again
to FIG. 4, the devices 409 and 410 may share a TCC, e.g., TCC 506,
and both detect the fault 416. The device 410 may signal the device
409 to delay it fault protection operation, which has the affect of
shifting in time its TCC curve. Thus, coordination is provided
between the device 409 and the device 410 because the device 409
implements its fault protection operation only after the device 410
operates. With the devices 409 and 410 coordinated, the device 409
and 408 may no longer be coordinated as the TCC of the device 409
is time-shifted toward that of the device 408. Thus, the device 409
will signal the device 408 to delay, similarly shifting in time its
TCC. Generally, a device that receives a delay command signals the
next upstream device with a second delay command. In fact, first,
second and up to "N" delay commands, were "N" is the number of
devices sharing a TCC following a last unique TCC may be employed
to ensure coordination back to the source 402. As a result of the
first, second, and/or N delay commands, only the device 410
operates to isolate the fault. As will be appreciated, the
communication speed of the delay command must exceed the minimum
trip time for the fault protection device to ensure the delay
command(s) is received before the fault protection device trips.
Typical vacuum fault interrupters are capable of tripping, i.e.,
operating in a fault protection mode, within about 0.1 second, and
communication of the delay command may occur in less than about 100
milliseconds.
[0043] As appreciated from the foregoing discussion, fault
protection devices may be coordinated essentially by staggering the
fault protection characteristics of the devices in a path from a
source to a load such that the response time of the device closest
so the fault will clear the fault faster than the response of any
upstream device. Device coordination can be problematic as
additional fault protection devices are added in series between a
source and a load, but, as described above, the communication
capability of the fault protection devices themselves is
advantageously used to facilitate coordination between devices
where coordination of a series devices results in two or more
devices having the same fault protection characteristics. In an
alternative approach, two or more devices may be configured to
operate in tandem or as a team to provide the necessary
coordination and hence the desired fault protection response. Using
tandem or team operation allows series devices to provide the
intended fault isolation and still achieve coordination with
existing upstream circuit breakers or downstream fuses.
[0044] There are also occurrences on installed systems where series
devices might miscoordinate for a number of reasons such as
improper settings, tolerances on the fault relay, loss of
communication signals, etc. As noted above, this may be addressed
by having the fault protection devices periodically propagate their
status and fault protection characteristics resulting in the
automatic recoordination of the devices. The tandem or team
operation of devices can also be evoked in these situations to
improve overall system operation, again, by ensuring isolation of
only the faulted segment even when device miscoordination should
exist.
[0045] Referring again to FIG. 4, each section of the feeder 400
has its own fault protection device, i.e., fault protection devices
406-410. From each of these sections there may extend lateral loads
that are protected by fuses, such as the load 412 protected by the
fuse 414 extending from the section 418. Furthermore, as described
above, it may necessary that the fault protection devices 409 and
410 have the same fault response characteristics, e.g., to ensure
coordination with downstream load protection devices.
[0046] The following described method allows the inclusion of
multiple series fault protection devices with a predetermined and
known operating sequence to isolate a single faulted section. The
device 410 may be set to operate with the same fault protection
characteristics, e.g., the same TCC, as the device 409. Operating
and reclosing logic may be applied by the fault protection devices
409 and 410 to ensure that only the proper device opens for the
fault 416.
[0047] A fault in the section 418 between the device 409 and 410
would only be seen by the device 409 and it would appropriately
open. The device 410 would not respond since it did not see a
fault, e.g., an over current. Should the fault in the section 418
be a "temporary fault" that would be cleared by the initial
operation of the device 409, the device 409 could be set to reclose
to thereby reenergize both sections 418 and 420, providing the
minimum outage time for the fault scenario. No special logic needs
to be implemented in the devices 409 and 410 even though each may
have the same fault protection parameters.
[0048] The fault 416 in the section 420, as indicated in FIG. 4,
may be addressed by having the fault protection devices 409 and 410
implement response logic. Several scenarios are possible. Note that
even though both the fault protection devices 409 and 410 are set
to operate on the same fault protection parameters, there are
inherent tolerances in each of the devices such that for the same
fault current, either device may operate before the other one, or
both devices may operate essentially simultaneously. It is likely
not possible to eliminate these inherent differences in the devices
themselves, and the logic may be adapted to respond to these
various scenarios.
Example 1
[0049] The devices 409 and 410 detect the fault current, and the
device 410 trips and clears the fault current before the device 409
trips. This is the desired mode of operation, and no further logic
is needed. The device 409 would have knowledge of a downstream
fault cleared by another protective device but does not need to
take any further action.
Example 2
[0050] The devices 409 and 410 each sense the fault current and
essentially trip simultaneously to clear both sections 418 and 420.
Both devices 409 and 410 are set to reclose and test the circuit.
The device 410, however, saw an overcurrent and tripped the
interrupter, but also saw a loss of voltage due to tripping of the
device 409. The device 410 may be configured to not attempt to
reclose until voltage is restored on the source side. The device
409 would perform its reclosing operation and energize section 418,
which has not faulted and would restore voltage to the terminals of
the device 410. The device 410, upon detecting voltage, may then
reclose to test the circuit for a fault in the section 420. Service
is restored to the section 420 if the fault 416 is temporary, and
therefore, there is no fault detected when the device 410 recloses.
If, however, the fault 416 is persistent, the device 410 would
interrupt the fault and continue with its test/reclose sequence.
The device 409 does not operate during the test sequence for one of
the following two reasons. [0051] 1. When conducting the test
sequence, the device 410 may use a "pinging" type test, such as
described in the commonly assigned U.S. patent application Entitled
"Fault Interrupting and Closing Device" Ser. No. ______, filed Oct.
28, 2005, attorney docket number SC-5388 P1, the disclosure of
which is hereby expressly incorporated herein by reference. As only
a momentary pulse of current is used to test the line sections, the
device 409 would not "see" the test current; and therefore, would
not timeout on its fault protection parameters. In this fashion,
coordination would be achieved between the devices 409 and 410
while device 410 tests the segment 420. [0052] 2. If more
conventional reclosing is used where the device 410 reenergizes the
segment 420 to test with an extended fault current, the device 409
may be configured to shift to a slower fault protection parameter
set given the knowledge of tripping on a measured fault current and
successfully closing to restore service to the segment 418. The
slower fault protection parameter set provides the coordination
necessary between the devices 409 and 410. For example, if both
devices are set to a common TCC, the device 409 after clearing the
initial fault and reclosing successfully, would shift the TCC in
time a delay period equal to or greater than the reclose sequence
assigned to the device 410. In this way, the device 409 temporarily
delays its response in order to achieve coordination for faults in
the section 420.
Example 3
[0053] The device 409 clears the fault 416 before the device 410
trips. The device 410, however, will sense an overcurrent but prior
to reaching its trip settings, the device 410 will see a loss of
source voltage. Using this information, the device 410 may
automatically open and go into an operating mode as described in
Example 2 above. If necessary based upon the test procedure
implemented by the device 410, the device 409 would appropriately
adjust its time fault protection response or not.
[0054] Overall, two fault protection devices can be set to operate
as a team or in tandem to provide clearing of the appropriate
faulted section even when the responses must be set to the same or
nearly the same fault protection parameters in order to coordinate
properly with upstream and/or downstream devices. This same
operating scenario may be used in conditions where there is an
unintended miscoordination, for example, the fault protection
parameters on the device 409 are set incorrectly faster than those
of the device 410.
[0055] While the invention is described in terms of several
preferred embodiments of circuit or fault interrupting devices, it
will be appreciated that the invention is not limited to circuit
interrupting and disconnect devices. The inventive concepts may be
employed in connection with any number of devices including circuit
breakers, reclosers, and the like.
[0056] While the present disclosure is susceptible to various
modifications and alternative forms, certain embodiments are shown
by way of example in the drawings and the herein described
embodiments. It will be understood, however, that this disclosure
is not intended to limit the invention to the particular forms
described, but to the contrary, the invention is intended to cover
all modifications, alternatives, and equivalents defined by the
appended claims.
[0057] It should also be understood that, unless a term is
expressly defined in this patent using the sentence "As used
herein, the term `______` is hereby defined to mean . . . " or a
similar sentence, there is no intent to limit the meaning of that
term, either expressly or by implication, beyond its plain or
ordinary meaning, and such term should not be interpreted to be
limited in scope based on any statement made in any section of this
patent (other than the language of the claims). To the extent that
any term recited in the claims at the end of this patent is
referred to in this patent in a manner consistent with a single
meaning, that is done for sake of clarity only so as to not confuse
the reader, and it is not intended that such claim term by limited,
by implication or otherwise, to that single meaning. Unless a claim
element is defined by reciting the word "means" and a function
without the recital of any structure, it is not intended that the
scope of any claim element be interpreted based on the application
of 35 U.S.C. .sctn.112, sixth paragraph.
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