U.S. patent application number 17/170073 was filed with the patent office on 2021-06-03 for redundant power module and discharge circuit for improved substation device availability.
This patent application is currently assigned to Schweitzer Engineering Laboratories, Inc.. The applicant listed for this patent is Schweitzer Engineering Laboratories, Inc.. Invention is credited to David J. Casebolt, Krishnanjan Gubba Ravikumar, Bruce A. Hall, Sean D. Robertson, Edmund O. Schweitzer, III, Austin Edward Wade, David E. Whitehead.
Application Number | 20210167590 17/170073 |
Document ID | / |
Family ID | 1000005448032 |
Filed Date | 2021-06-03 |
United States Patent
Application |
20210167590 |
Kind Code |
A1 |
Schweitzer, III; Edmund O. ;
et al. |
June 3, 2021 |
REDUNDANT POWER MODULE AND DISCHARGE CIRCUIT FOR IMPROVED
SUBSTATION DEVICE AVAILABILITY
Abstract
Disclosed herein are systems for maintaining protection of
electric power delivery systems in the event of a control power
failure or other anomaly. A reliable power module conditions
electric power from multiple independent sources and provides
electrical operational power to electric power delivery system
protective loads. The reliable power module includes an energy
storage device for providing operational power even upon loss of
all control power sources. The energy storage may be sufficient to
ride through expected losses such as a time to start up backup
generation. The energy storage may be sufficient to power a trip
coil. Thus, electric power system protection is maintained even
upon loss of control power. A discharge circuit is provided to
allow an operator to de-energize an energy storage device.
Inventors: |
Schweitzer, III; Edmund O.;
(Pullman, WA) ; Whitehead; David E.; (Pullman,
WA) ; Casebolt; David J.; (Moscow, ID) ; Gubba
Ravikumar; Krishnanjan; (Pullman, WA) ; Robertson;
Sean D.; (Moscow, ID) ; Wade; Austin Edward;
(Moscow, ID) ; Hall; Bruce A.; (Pullman,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schweitzer Engineering Laboratories, Inc. |
Pullman |
WA |
US |
|
|
Assignee: |
Schweitzer Engineering
Laboratories, Inc.
Pullman
WA
|
Family ID: |
1000005448032 |
Appl. No.: |
17/170073 |
Filed: |
February 8, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16796567 |
Feb 20, 2020 |
10951057 |
|
|
17170073 |
|
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|
62914501 |
Oct 13, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02H 1/06 20130101; H02J
9/068 20200101; H02J 7/345 20130101 |
International
Class: |
H02H 1/06 20060101
H02H001/06; H02J 7/34 20060101 H02J007/34; H02J 9/06 20060101
H02J009/06 |
Claims
1. A redundant power module, comprising: a plurality of power
inputs to receive electrical energy; an energy storage capacitor to
store electrical energy received from the plurality of power
inputs; an output in electrical communication with the plurality of
power inputs and the energy storage capacitor and to provide an
unregulated voltage using: electrical energy from any of the
plurality of power inputs when electrical energy is available from
any of the plurality of power inputs, and the energy storage
capacitor when the plurality of power inputs are unavailable; and a
discharge circuit to discharge electrical energy stored in the
energy storage capacitor, comprising: a discharge selector to
electrically couple the energy storage capacitor to the plurality
of power inputs and an output in a first position and to
electrically couple the energy storage capacitor to a discharge
component in a second position; wherein the discharge circuit is
configured to discharge the electrical energy stored in the energy
storage capacitor when the discharge selector is in the second
position.
2. The redundant power module of claim 1, wherein the output
remains electrically coupled to the plurality of power inputs when
the discharge selector is in the second position.
3. The redundant power module of claim 1, wherein the energy
storage capacitor is electrically isolated from the output when the
discharge selector is in the second position.
4. The redundant power module of claim 1, wherein the discharge
selector comprises a jumper.
5. The redundant power module of claim 1, further comprising a
first diode disposed between the plurality of power inputs and the
energy storage capacitor, wherein the first diode is configured to
prevent back-feed of electric current from the output to the
plurality of power inputs.
6. The redundant power module of claim 5, further comprising a
first resistor disposed between the plurality of power inputs and
the energy storage capacitor, wherein the resistor is configured to
reduce an inrush current to the energy storage capacitor.
7. The redundant power module of claim 5, further comprising a
second diode disposed between the plurality of power inputs and the
output, wherein the second diode is configured to prevent back-feed
of electric current from the output to the plurality of power
inputs.
8. The redundant power module of claim 7, further comprising a
third diode disposed between the output and the energy storage
capacitor, wherein the third diode is configured to prevent
back-feed of electric current from the output to the energy storage
capacitor.
9. The redundant power module of claim 8, wherein the first diode
and the third diode provide a redundant path for electric current
around the second diode when the second diode fails.
10. The redundant power module of claim 7, further comprising: a
first set of connectors disposed on a first side of the second
diode; and a second set of connectors disposed on a second side of
the second diode; wherein the first set of connectors and the
second set of connectors are configured to enable a test to
determine whether the second diode has failed.
11. The redundant power module of claim 1, further comprising a
visual indicator to show a charging status of the energy storage
capacitor.
12. The redundant power module of claim 1, further comprising a
first terminal, a second terminal, and a third terminal, wherein
the discharge selector is configured to electrically couple the
first terminal and the second terminal in the first position and is
configured to electrically couple the second terminal and the third
terminal in the second position.
13. The redundant power module of claim 1, further comprising a
second resistor disposed between the energy storage capacitor and
the output to limit flow of electrical current to the output.
14. A method of providing electrical power to a device using a
redundant power module, the method comprising: receiving electrical
energy, using the redundant power module, from a plurality of power
inputs; storing electrical energy received from the plurality of
power inputs in an energy storage capacitor; providing an
unregulated voltage at an output of the redundant power module, the
output in electrical communication with the plurality of power
inputs and the energy storage capacitor using: electrical energy
from any of the plurality of power inputs when electrical energy is
available from any of the plurality of power inputs, and an energy
storage capacitor when the plurality of power inputs are
unavailable; moving a discharge selector from a first position in
which the energy storage capacitor is coupled to the plurality of
power inputs and the output to a second position in which the
energy storage capacitor is coupled to a discharge circuit; and
discharging electrical energy stored in the energy storage
capacitor using the discharge circuit.
15. The method of claim 14, wherein a first diode is disposed
between the plurality of power inputs and the energy storage
capacitor to prevent back-feed of electric current from the output
to the plurality of power inputs.
16. The method of claim 15, wherein a resistor is disposed between
the plurality of power inputs and the energy storage capacitor to
reduce an inrush current to the energy storage capacitor.
17. The method of claim 15, wherein a second diode is disposed
between the plurality of power inputs and the output to prevent
back-feed of electric current from the output to the plurality of
power inputs.
18. The method of claim 17, wherein a third diode is disposed
between the output and the energy storage capacitor to prevent
back-feed of electric current from the output to the energy storage
capacitor.
19. The method of claim 18, wherein the first diode and the third
diode provide a redundant path for electric current around the
second diode when the second diode fails.
20. The method of claim 17, further comprising: providing a first
set of connectors disposed on a first side of the second diode;
providing a second set of connectors disposed on a second side of
the second diode; and performing a test to determine whether the
second diode has failed.
Description
RELATED APPLICATION
[0001] This application claims priority from and benefit of U.S.
Provisional Application Ser. No. 62/914,501, filed on 13 Oct. 2019,
entitled "Reliable Power Module for Primary Protection Devices"
which is hereby incorporated by reference in its entirety for all
purposes, and claims priority from and benefit of U.S. Utility
application Ser. No. 16/796,567, filed on 20 Feb. 2020, entitled
"Reliable Power Module for Improved Substation Device
Availability," which is hereby incorporated by reference in its
entirety for all purposes.
TECHNICAL FIELD
[0002] This disclosure relates to maintaining electric power
delivery system protection even during control power failures. More
particularly, this disclosure relates to a reliable power module
for providing operational power to protection devices and other
critical equipment of an electric power system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Non-limiting and non-exhaustive embodiments of the
disclosure are described, including various embodiments of the
disclosure with reference to the figures, in which:
[0004] FIG. 1 illustrates a simplified one-line diagram of an
electric power delivery system for providing electric power to
loads including a system for protection and automation.
[0005] FIG. 2 illustrates a simplified block diagram of an
intelligent electronic device (IED) used for electric power system
protection.
[0006] FIG. 3 illustrates a simplified block diagram of a reliable
power module and various inputs and outputs in accordance with
several embodiments.
[0007] FIG. 4 illustrates a simplified block diagram of a reliable
power module providing operational power to various devices in
parallel.
[0008] FIG. 5 illustrates a simplified block diagram of a reliable
power module providing tripping current to a trip coil.
[0009] FIG. 6 illustrates a logical diagram for tripping a breaker
in the event of a loss of all power sources to a reliable power
module.
[0010] FIG. 7 illustrates a simplified block diagram of a pair of
reliable power modules providing operational power in parallel.
[0011] FIG. 8 illustrates a simplified block diagram of active
circuitry for power conversion.
[0012] FIG. 9 illustrates a circuit diagram of a redundant power
module charge and discharge circuit consistent with embodiments of
the present disclosure.
[0013] FIG. 10 illustrates a circuit diagram of another redundant
power module charge and discharge circuit consistent with
embodiments of the present disclosure.
[0014] FIG. 11 illustrates a representation of a front panel and a
back panel of a redundant power module consistent with embodiments
of the present disclosure.
[0015] FIG. 12 illustrates a flow chart of a method of using a
reliable power module consistent with embodiments of the present
disclosure.
[0016] FIG. 13 illustrates a plot over time of an output voltage of
a redundant power module when providing energy to power a trip
event and when all input power sources are lost consistent with
embodiments of the present disclosure.
DETAILED DESCRIPTION
[0017] Electric power delivery systems are widely used to generate,
transmit, and distribute electric power to loads, and serve as an
important part of the critical infrastructure. Power systems and
components are often monitored and protected by intelligent
electronic devices (IEDs) and systems of IEDs that obtain electric
power system information from the equipment and provide protective
actions, monitor, and automate the power system. Several IEDs may
be in communication to facilitate sharing of information for
station-wide, area-wide, or even system-wide protection.
[0018] Due to the critical nature of electric power systems, it is
very important that electric power systems maintain protection of
the equipment even when operational power (also known as control
power or station auxiliary power) to the IEDs is unavailable. In
many ways, operational power may be a single point of failure.
Operational power can be interrupted or lost completely because of
direct-current (DC) faults, battery charger failures, testing, and
maintenance incidents. Any interruption, even as short as 100 ms
can cause protective devices to restart. Restarts cause a loss of
availability of protection. Accordingly, what is needed are systems
and devices to provide reliable operational power to protective
devices. Disclosed herein are embodiments of a reliable power
module to maintain power supply to primary protection relays even
when operational power may be interrupted, lost, or otherwise
unavailable.
[0019] The embodiments of the disclosure will be best understood by
reference to the drawings, wherein like parts are designated by
like numerals throughout. It will be readily understood that the
components of the disclosed embodiments, as generally described and
illustrated in the figures herein, could be arranged and designed
in a wide variety of different configurations. Thus, the following
detailed description of the embodiments of the systems and methods
of the disclosure is not intended to limit the scope of the
disclosure, as claimed, but is merely representative of possible
embodiments of the disclosure. In addition, the steps of a method
do not necessarily need to be executed in any specific order, or
even sequentially, nor need the steps be executed only once, unless
otherwise specified. In some cases, well-known features, structures
or operations are not shown or described in detail. Furthermore,
the described features, structures, or operations may be combined
in any suitable manner in one or more embodiments. It will also be
readily understood that the components of the embodiments as
generally described and illustrated in the figures herein could be
arranged and designed in a wide variety of different
configurations.
[0020] FIG. 1 illustrates a simplified one-line diagram of an
electric power delivery system. It should be noted that the system
may include multiple phases and additional equipment and
complexity. Also illustrated is a system of IEDs that obtain
electric power system information from electric power system
equipment, and effect control actions on the electric power system
to provide protection and automation to the electric power delivery
system. The power system includes various equipment such as a bus
102 (illustrated as a transmission bus) providing electric power to
a second bus 104 (illustrated as a distribution bus) via a
transformer 106 for stepping down the power from a high
(transmission) voltage to a lower (distribution) voltage. Various
feeders extend from the second bus 104 for delivering electric
power to distributed loads. Circuit breakers 122, 124, 182, 184,
186, 188 may be used to selectively connect and disconnect portions
of the power system for various purposes such as reconfiguration,
protection in the event of a fault, or the like.
[0021] A bus protection relay 140 may be an IED configured to
determine operating conditions on a zone that includes the second
bus 104 and provide signals to effect a protection operation upon
determination of an adverse condition. IED 140 may obtain current
and/or voltage signals related to electric power entering and
leaving the bus 104 from various equipment such as instrument
transformers. IED 140 may be configured to provide differential
protection, overvoltage protection, and various other protection
for the zone including the bus 104.
[0022] Feeder protection relay may be an IED 150 that obtains bus
current and/or voltage signals from various instrument transformers
in electrical communication with the feeders. IED 150 may provide
overcurrent, directional, distance, overfrequency, underfrequency,
and other protection to the feeders.
[0023] Transformer relay may be an IED 120 configured to provide
protection to the transformer 106. IED 120 may obtain current
signals from both sides of the transformer 106 from CTs 112 and
116. IED 120 may further provide information to IED 140. IED 120
may be configured to provide differential protection, overcurrent
protection, over frequency protection, underfrequency protection,
and other various protection for the transformer 106.
[0024] IEDs 120, 140, 150 may be in communication either directly
or indirectly with various circuit breakers 122, 124, 182, 184,
186, 188. The circuit breakers may be configurable between open and
closed positions, and may open upon command from the IEDs.
Accordingly, the IEDs 120, 140, 150 may be configured to provide
protection to the electric power delivery system by commanding the
appropriate circuit breaker to open upon detection of an abnormal
operating condition on the electric power system. Open commands may
be given directly or indirectly. Open signals may be provided by
closing a contact to provide the electrical power to the circuit
breaker to open.
[0025] In various embodiments, the IEDs may be in communication
with a monitoring, automation, or other supervisory system or
device 190, such as a SCADA system.
[0026] FIG. 2 illustrates a simplified block diagram of an IED 200
such as the transformer relay 120, bus protection relay 140, or
feeder protection relay 150. The IED 200 receives power system
information such as currents and/or voltages from the power system.
As illustrated, the IED 200 obtains analog current and voltage
signals from CTs and PTs. In other embodiments, IED 200 may receive
digitized analog signals from MUs. IED 200 may include sampling
circuitry 210 including current input 202 and voltage input 214.
Such inputs 202, 214 may include various transformers, filters, and
other hardware to condition the analog signals for sampling and
digitizing by one or more analog-to-digital converters A/D 218. The
digitized analog signals 222 may be provided to a processor
224.
[0027] IED 200 may include various inputs and interfaces such as a
time input 212 to obtain a common time signal from a common time
source. The common time signal may be used in various protection
and monitoring functions. A communications interface 216 may be
provided to facilitate communications with SCADA, other IEDs, MUs,
or the like. A monitored equipment interface 208 may be in
communication with monitored equipment such as circuit breakers,
transformers, capacitor banks, voltage regulators, reclosers, MUs,
or the like to send command signals to the equipment and/or receive
status information from the equipment. A computer readable storage
medium 230 may be a repository of computer instructions for
execution on the processor 224. Although illustrated as a separate
component, the storage medium 230 may be packaged with the
processor 224. In various other embodiments, the processor may be
embodied as a dedicated processing device such as a
field-programmable gate array (FPGA) operating various protection
instructions. Various components may be in communication via a
communications bus 242.
[0028] The computer-readable storage medium 230 may include
instructions for execution of various operations of the IED. For
example, a module of communications instructions 232 may be
executed by the processor such that the IED 200 performs
communication functions with other devices. The communications
instructions 232 may include instructions for formatting
communications, receiving communications, addresses for
communicating, settings related to compliance with various
communication protocols such as, for example, DNP, DNP3, IEC 61850
communications standards, and the like. Signal processing
instructions 240 may include instructions for processing current,
voltage, and other signals for use by other protection and
monitoring functions. For example, signal processing 240 may
include various digital filters, resampling, and the like.
Protection actions instructions 252 may include instructions for
performing various protection functions such as overcurrent,
differential, directional, distance, undervoltage, voltage
regulation, bus protection, overfrequency, underfrequency,
traveling wave, and other protection operations.
[0029] IED 200 may include several components that require electric
power to operate. Typical IEDs include an internal power supply
that receives electric power from a source, and condition the power
for use by components of the IED. The power source may be a
substation battery (DC), utility power, or the like. In the event
that the power supply to the IED is disrupted, the IED may cease to
operate, thus leaving the electric power system vulnerable and
without protection. Furthermore, even if the disruption is
momentary, the IEDs that experienced the disruption would typically
require time to start up before they are ready to protect the power
system. Accordingly, what is needed is an improved power module to
provide operational power to IEDs in a more reliable manner. What
is further needed is a power module to provide operational power to
IEDs even during a disruption in order to ride through the
disruption.
[0030] What is presented herein is a redundant power module 280 in
electrical communication with one or more IEDs 200 to condition and
provide reliable electric power thereto. The redundant power module
280 disclosed herein is further configured to provide a source of
temporary electric power even in the event of electric power
disruption. Accordingly, the embodiments disclosed herein include
power modules that receive electric power from multiple sources and
condition the electric power for use by IEDs. Furthermore, several
embodiments herein include energy storage to provide uninterrupted
electric power to IEDs even when all power sources to the power
module are disrupted.
[0031] FIG. 3 illustrates a redundant power module 280 for
providing operational power to the various IEDs. The redundant
power module 280 provides a simple novel way to increase the
reliability of power supply to critical substation equipment such
as protective relays as described above, and other devices that use
electric power such as, for example, automation controllers, SCADA
equipment, communication devices, and the like. The redundant power
module 280 includes various inputs 304, 306, 308, 310 for receiving
multiple sources of electric power. For example, a first input 304
may be configured to receive DC power from a DC power source 372
such as a substation battery or the like. The redundant power
module 280 may include multiple AC inputs 306, 308, 310 each
configured to receive AC power from AC power sources 374, 376, and
378. The AC inputs may be independent. The redundant power module
280 may be configured to condition and deliver power when any one
or more sources provide sufficient electric power to the redundant
power module 280.
[0032] To produce a highly reliable and available conditioned DC
output 348, the redundant power module 280 may include circuitry
for conditioning electric power, and may include elements for
storing electric power. Each input 304-310 includes a protective
element such as a fuse 312, 314, 316, 318 designed to cut off power
from a particular source in the event that a current level of that
power source exceeds a safe operating margin. In general, the power
obtained over inputs 304-310 is passed through conditioning
circuitry that may include a rectification system to produce the DC
output. Power from the DC source 372 may pass through the passive
conditioning circuitry that includes a full-wave bridge rectifier
326 to ensure proper polarity. Thus, the conditioning circuitry for
the DC source 372 provides direct current conditioned power 362 for
powering the protective loads 352, 354, 356, 358.
[0033] Power from the AC sources 374, 376, 378 must be conditioned
by conditioning circuitry to provide the direct current conditioned
power 362. The conditioning circuitry may include transformation
and rectification to produce the desired DC power on output 348.
Power from each AC source 374, 376, 378 may pass through
transformers 320, 322, 324 to transform the source current or
voltage to an expected level and provide isolation. Power from the
transformers 320, 322, 324 may be rectified using rectifier
circuits 328, 330, and 332. Rectifier circuits may include any
circuitry useful for rectifying an AC power source into DC power
supply. Rectifier circuits 328, 330, 332 may be implemented as
simple diodes, providing half-wave rectified DC power. Rectifier
circuits 328, 330, 332 may include diode bridges to provide full
wave rectified DC power. Rectifier circuits 328, 330, 332 may
include additional circuitry to smooth and otherwise condition the
DC output from each source to be within expected margins.
[0034] Although the rectifier circuitry illustrated in FIG. 3
represents passive circuitry, the redundant power module may
include active circuitry for converting the input source power into
the expected output power for consuming devices. FIG. 8 (discussed
hereafter) discloses active circuitry for power conversion.
[0035] In various embodiments AC sources 374, 376, and 378 may be
three-phase sources with each source from a separate phase. In such
embodiments, the rectifier circuitry 328, 330, 332 may include a
three-phase diode bridge for three-phase full-wave rectification of
the three-phase input power.
[0036] In various embodiments, one or more of the AC sources 374,
376, and/or 378 may include electric power provided parasitically
from the electric power delivery system. For example, a current
transformer in electrical communication with a phase conductor of
an AC electric power system may be used as an AC power source for
the redundant power module 280. The AC sources may obtain power
using substation potential transformers, station auxiliary
transformers, backup generators, or any combination.
[0037] The rectified power from each of the sources are then passed
through diode 342, and output protection fuse 346. The diode 342
may protect against reverse biasing the output, thus providing
additional safety. The DC output 348 is then provided to various
consuming devices such as, for example, IED 352, IED 354,
communication device 356 and controller 358. Although certain
consuming devices are illustrated, any device that may consume DC
power may benefit from the output 348. In various embodiments, the
redundant power module 280 may output power for tripping circuit
breakers, with the output 348 in electrical communication with a
trip circuit. As such, power for tripping circuit breakers may be
available even when control power is otherwise disrupted.
[0038] The redundant power module 280 may include one or more
energy storage devices 334 such as capacitors for storage of
electric energy and delivery of the stored electric energy to the
output 348 in the event that all of the power sources 372-378 to
the redundant power module 280 are disrupted. The energy storage
device 334 may be configured to store sufficient electric energy to
ride through expected disruptions.
[0039] In one embodiment, the energy storage device 334 is a
capacitive element such as a capacitor or capacitor bank. The
capacitive element may be configured to store around 1500
watt-seconds nominal of energy. The capacitive element may store
sufficient power to support a 25-watt load for 60 seconds. The
capacitive element may be rated at around 1/8 farad (F). The energy
storage device 334 may further include a discharge switch 340 in
electrical communication with a terminal of the energy storage
device 334 for selectively discharging electric power stored in the
energy storage device 334 through resistor 338. The discharge
switch 340 may be considered as a safety mechanism due to the large
amount of energy that may be stored in the energy storage device
334.
[0040] FIG. 4 illustrates a simplified block diagram of one system
that includes a reliable power module 280 for providing operational
power to devices. The reliable power module 280 receives electric
power from multiple control power sources including three AC power
sources 374, 376, 378, and a DC power source 372. The reliable
power module 280 includes a DC output with a positive pole 442 and
a negative pole 444. The DC output may be protected by one or more
fuses. Multiple devices 352, 354, 356, 358 may be connected in
parallel from the single DC output (poles 442, 444).
[0041] In the illustrated embodiment, the reliable power module 280
continues to provide operational power to each of the devices
unless all of the AC and DC power sources are lost. Even in the
event that all AC and DC power sources are lost, the reliable power
module 280 continues to provide operational power to the devices
until the energy storage is expired.
[0042] One important function of protective relays is to signal
circuit breakers to trip in accordance with the operational logic
of the protective relay. Tripping the breaker is necessary to
remove electric power from the affected portion of the electric
power delivery system. However, tripping a breaker requires
operational power. In the event that operational power is lost, the
ability of protective devices to trip a breaker may also be lost.
Accordingly, the reliable power module 280 of various embodiments
described herein may be used to provide operational power to
protective devices and to provide operational power to trip coils
in order to trip a circuit breaker. It should be noted that the
reliable power module in accordance with several embodiments herein
is capable of storing around 1500 watt-seconds nominal of electric
power. Trip coils typically require less than around 60
watt-seconds to operate. Accordingly, the reliable power module may
be used to provide electric power to protective devices and to
operate trip coils even in the event that all power sources to the
reliable power module are lost.
[0043] FIG. 5 illustrates a simplified block diagram of a reliable
power module 280 for providing electric power to a protection
device 550 and a trip coil 556 in parallel. The protection device
550 may include a power supply 552 in electrical communication with
the positive and negative poles 442, 444 of the DC output, and
configured to provide electric power to the various modules of the
protection device 550. One pole (illustrated is the positive pole
442) may be in electrical communication with the trip contact 554
of the protection device 550. The trip contact may be in electrical
communication with the trip coil 556, which is also in electrical
communication with the other pole (illustrated is the negative pole
444), such that upon closing of the trip contact 554 by the
protection device 550 the trip coil 556 is energized, causing the
circuit breaker (not illustrated) to trip open to remove electric
power from a portion of the electric power delivery system.
[0044] Accordingly, the reliable power module 280 provides
operational power to the protection relay and trip coil in
parallel. Even in the event of disruption of all power sources 372,
374, 376, 378, operational power continues to be provided to the
protection relay 550 and trip coil 556 such that protection to the
electric power system is maintained.
[0045] In various embodiments, it may be desirable to simply trip
all breakers in the event that protection is lost. That is, a
system may be designed such that in the event that all sources of
operational power are lost, circuit breakers are automatically
tripped so that the electric power delivery system does not remain
operational when unprotected.
[0046] FIG. 6 illustrates a logic diagram useful for such action.
In accordance with several embodiments herein, the reliable power
module 280 may include alarm contact outputs 602, 604, 606, 608.
The alarm contact outputs 602-608 may each be in communication with
the individual power sources 372, 374, 376, 378. The alarm contact
outputs 602-608 may be configured to assert upon loss of the
related power source. That is, output 602 asserts upon loss of AC
power source 378; output 604 asserts upon loss of AC power source
376; output 606 asserts upon loss of AC power source 374; and,
output 608 asserts upon loss of DC power source 372.
[0047] The outputs 602-608 may be in communication with a
protection device 550 capable of signaling one or more circuit
breakers to trip. Each of the outputs 602-608 may signal an AND
gate 610. Upon assertion of each of the output signals 602-608,
indicating interruption of all of the power sources 372-378, the
AND gate asserts to timer 612. The timer 612 may pickup after a
predetermined delay time. The delay time may be set long enough to
provide security over temporary interruptions. The delay time may
be set according to the time that the reliable power module 280 is
capable of providing operational power in the event of loss of all
power sources. Upon satisfaction of the pickup time, the timer 612
asserts to the trip contact 614. Upon assertion of the trip contact
in response to the assertion from timer 612, current is allowed to
flow to the trip coil(s) to trip one or more breakers. The power to
the trip coil may be provided by the reliable power module 280 or
another reliable power module, or other available power source.
[0048] In various systems, multiple reliable power modules may be
used to increase availability of operational power and amount of
ride through time. In various systems, there may be more power
sources available than power inputs to a single reliable power
module. In various embodiments, it may be desired to increase the
amount of energy available during an interruption to the power
sources. In such systems, multiple reliable power modules may be
used to take advantage of the various power sources and/or to
provide additional operational energy in the event that the power
sources are lost.
[0049] FIG. 7 illustrates one embodiment of reliable power modules
in parallel to provide reliable operational power. The illustrated
system includes a first reliable power module 280 and a second
reliable power module 780. The reliable power modules may operate
in accordance with the several embodiments described herein. the
reliable power modules 280, 780 may receive power from multiple AC
and/or DC power sources 372, 374, 376, 378, 772, 774, 776, 778.
Although separate AC and DC power sources are illustrated, it
should be noted that any of the power sources may be common to both
of the reliable power modules 280, 780. For example, AC power
sources 378 and 778 may be the same power source such as a utility
AC power source at a substation. In various other embodiments, all
of the power sources 372-378 and 772-778 may be different power
sources, and may or may not be independent of each other. For
example, AC power of one phase may be a different control power
input than the AC power of another phase of the same three-phase
power system.
[0050] The DC power outputs of the reliable power modules 280, 780
may be configured in parallel to provide electric power to various
devices. For example, the positive DC outputs 442, 742 may be in
electrical communication to provide a positive DC node 792; and the
negative DC outputs 444, 744 may be in electrical communication to
provide a common negative DC node 794. The positive and negative
nodes 792, 794 may be used to provide the operational power to the
loads. The loads may be configured in parallel such as is
illustrated in FIG. 4 from the common positive and negative DC
nodes.
[0051] FIG. 8 illustrates a reliable power module 880 that includes
active circuitry for conditioning input power for delivery to the
consuming devices. As with various embodiments described above, the
reliable power module 880 may include various power inputs such as
852, 854, 856, 858, which may be in electrical contact with various
electric power sources. The power sources may be AC power sources
or DC power sources. The reliable power module 880 may be
configured to condition the input AC and/or DC power to DC power
within acceptable parameters.
[0052] In the illustrated embodiment, one power source may be in
electrical connection with input 852. The power source may be an AC
or a DC power source. The power source is filtered by, for example,
an input electrical magnetic interference (EMI) filter 810. The
filter 810 may be conditioned to decrease the amount of EMI that
results from active or switched-mode power conditioning. The output
of the filter 810 may be rectified to DC by rectifier 812. Electric
power from the rectifier at a first voltage may be conditioned
using a switching converter 802 to provide an output DC power
within predetermined voltage and power ratings. The switching
converter 802 may be any switching converter such as, for example,
buck, boost, buck-boost, SEPIC, flyback, forward, or combinations
thereof.
[0053] The illustrated switching converter 802 includes a boost
pre-converter and a flyback converter at the power stage. The boost
pre-converter includes a diode in parallel with a series inductor
and diode, combined with a controlled switch (such as a
metal-oxide-semiconductor field-effect transistor (MOSFET)
controlled by a mode controller 814, as illustrated. The flyback
converter portion may include a controlled switch (such as a MOSFET
controlled by a mode controller 816). A transformer 818 may be used
for isolation and for converting the voltage to the acceptable
output level. Another controlled switch 820 may be used along with
a capacitor and rectifier circuits 326 to condition the output
power and protect against reverse biasing. The output of the
switching converter 802 may be combined (in OR fashion) with
outputs of additional power conditioning circuitry such that
conditioned power from any of the connected power source may
provide output operational power from the reliable power module
880.
[0054] Further inputs 854, 856, 858 may be in electrical connection
with one or more additional power supplies. The power supplies may
be AC and/or DC. Each of the inputs 854, 856, 858 may provide the
power to conditioning circuitry 804, 806, 808. In various
embodiments, each of the power conditioning circuitry 804, 806, 808
include active converters such as the switching converter 802. In
various other embodiments, one or more of the power conditioning
circuitry 804, 806, 808 are active converters such as the switching
converter 802, and the remaining power condition circuitry include
passive components such as is illustrated and described in
conjunction with FIG. 3. In various embodiments, the power
conditioning circuitry in communication with DC power inputs
include active circuitry such as the switching circuitry 802, and
the power conditioning circuitry in communication with AC power
inputs include passive circuitry such as is illustrated and
described in conjunction with FIG. 3. Filters and rectifiers (such
as filter 810 and rectifier 812) may also be included with
conditioning circuitry on one or more of the power inputs 852, 854,
856, 858 for AC and/or DC power sources.
[0055] FIG. 9 illustrates a circuit diagram of redundant power
module charge and discharge circuit 900 consistent with embodiments
of the present disclosure. The energy in capacitor 918 should be
discharged before a user works on any devices electrically
connected to the terminals of circuit 900. Electrical energy in the
form of direct current may be provided by a positive rail 926 and a
negative rail 928. Diode 908, which separates an input of the
positive rail 926 from an output, provides back-feed protection
from the output to the input. Diode 908 may also avoid a
reverse-polarity connection from transferring power from the output
to the input. During normal operation, electrical power flows from
the input through inductor 902 and diode 908 to the output terminal
and a load (not shown).
[0056] During normal operation, a jumper 916 may connect terminal
920 to terminal 922, and power flows from the input through diode
904 and charges capacitor 918. Diode 904 prevents energy stored in
capacitor 918 from back-feeding to the input terminal. Resistor 912
connected in series with diode 904 limits inrush current to
capacitor 918. Limiting inrush current may protect the input
sources and internal components. With jumper 916 positioned between
terminals 920 and 922, capacitor 918 charges to the input voltage
level.
[0057] If the input power source fails, the energy storage
capacitor 918 provides energy to the output terminals through
resistor 914 and diode 906. Resistor 914 limits discharge current
to prevent damage to circuit 900 and a connected load. Diode 906
prevents back-feed from output terminals to capacitor 918.
[0058] Energy stored in capacitor 918 should be completely
discharged before operators take any action in connection with
circuit 900. Capacitor 918 may be discharged by connecting jumper
916 to terminals 922 and 924. The resulting open circuit between
terminals 920 and 922 isolates capacitor 918 from the positive rail
926, allowing capacitor 918 to be taken out of service without
affecting the operation of a load. Further, the resulting
connection between terminals 922 and 924 allows energy stored in
capacitor 918 to discharge through resistor 910. Resistor 910 may
be sized to quickly discharge capacitor 918 without generating
excessive heating that could result in damage.
[0059] In the illustrated embodiment, terminal 922 can only be
connected to terminal 920 or 924 using jumper 916. This arrangement
prevents capacitor 918 from being simultaneously charged and
discharged, which could cause damage to capacitor 918, resistor
910, and/or 912 due to overheating. Various embodiments may use a
manual jumper, toggle switch, or other devices to ensure that
capacitor 918 cannot be simultaneously charged and discharged. In
some embodiments, jumper 916 may comprise a "U" shape that allows
an operator to grasp and move jumper 916 between terminals 920,
922, and 924. A portion of the jumper 916 that a user may contact
may be electrically insulated while providing a conductive path
between terminals.
[0060] A light-emitting diode (LED) 932 provides a visual
indication of whether capacitor 918 is charged or discharged
regardless of the position of jumper 916. When capacitor 918 is
charged, current may flow through resistor 930 and LED 932. The LED
932 may be positioned so that it is visible to operators of
equipment connected to circuit 900. Other types of indicators of
the charge status of capacitor 918 may be used in various
embodiments.
[0061] The configuration of diodes 904, 906, and 908 provides a
redundant path if diode 908 fails. In the event that diode 908
fails open, electrical energy may bypass the failure by flowing
through diode 904, resistor 912, resistor 914, and diode 906. A
failure of diode 908 may be identified by comparing measurements of
the voltage at the input and output of positive rail 926. In normal
operation, the output voltage will differ from the input voltage by
a voltage drop across diode 908. If diode 908 fails and creates an
open circuit, the output voltage would be reduced by a larger
voltage drop across diodes 904 and 906, along with the voltage drop
across resistors 912 and 914.
[0062] Components of circuit 900 may be selected to provide power
for a specified length of time. The amount of time that circuit 900
can power a load depends on the input voltage, the power draw of
the load, and the minimum voltage required by the load. In some
embodiments, components of circuit 900 may be selected to power a
6-watt load for 3.5 minutes, a 25-watt load for 50 seconds, and a
100-watt load for 12 seconds. In one specific embodiment, capacitor
918 may have a value of approximately 1/8 Farad and be capable of
storing 1300 watt-seconds of nominal energy.
[0063] FIG. 10 illustrates a circuit diagram of redundant power
module charge and discharge circuit 1000 consistent with
embodiments of the present disclosure. Electrical energy in the
form of direct current may be provided by a positive rail 1026 and
a negative rail 1028. Diode 1008 separates an input of the positive
rail 1026 from an output and provides back-feed protection from the
output to the input. During normal operation, electrical power
flows from the input, through diode 1008, and to the output
terminal and a load (not shown).
[0064] During normal operation, a jumper 1016 may connect terminal
1020 to terminal 2021 and allow power to flow from the input
terminal through diode 1004 and charge capacitor 1018. Diode 1004
blocks energy stored in capacitor 1018 from back-feeding to the
input. Resistor 1012 is connected in series with diode 1004 and may
limit inrush current to capacitor 1018. With jumper 1016 positioned
between terminals 1020 and 1021, the capacitor 1018 charges to the
input voltage level.
[0065] If the input power source fails, the energy storage
capacitor 1018 provides energy to the output through resistor 1014
and diode 1006. Resistor 1014 limits discharge current to prevent
damage to circuit 1000 and a connected load. Diode 1006 prevents
back-feed from output terminals to capacitor 1018.
[0066] Energy stored in capacitor 1018 should be completely
discharged before operators take any action in connection with
circuit 1000 or any load connected to circuit 1000. The energy
stored in capacitor 1018 may be discharged by connecting jumper
1016 to terminals 1022 and 1023. The resulting connection between
terminals 1022 and 1023 allows energy stored in capacitor 1018 to
discharge through resistor 1010. Resistor 1010 may be sized to
quickly discharge capacitor 1018 without generating excessive
heating that could result in damage.
[0067] FIG. 11 illustrates a representation of a front panel 1102
and a back panel 1104 of a redundant power module 1100 consistent
with embodiments of the present disclosure. Redundant power module
1100 combines up to three AC sources and one DC source to provide
power during power disturbances. Redundant power module 1100 may be
used to keep protection, automation, and/or supervisory systems
operational during power interruptions, substation battery
servicing, or other events. Common sources to combine include a DC
battery, substation service, an alternate substation service, a
backup generator, and instrument transformers. In the event of a
disturbance on one source, the other sources continue to provide
uninterrupted control power. Redundant power module 1100 may
provide many advantages of a redundant battery-powered system at a
lower cost.
[0068] Redundant power module 1100 may also be used to power
breaker trip applications. In one embodiment, redundant power
module 1100 may provide 100 watts of continuous power and 30 Amps
of momentary surge current to trip breakers. Energy storage may be
up to 1,300 watt-seconds. Most trip coils require less than 60
watt-seconds to operate, and as such, redundant power module 1100
can energize trip coils and power a protective relay long enough to
store event records after a total loss of control power. Multiple
redundant power modules may be used in parallel to provide
additional energy storage, and/or to increase the number of power
sources that can be connected.
[0069] The front panel 1102 illustrates the status of a DC source
and three AC sources with LEDs 1104, 1106, 1108, and 1110. The LEDs
1104, 1106, 1108, and 1110 may provide a visual indicator of the
status of each power source. LEDs 1104, 1106, 1108, and 1110 may be
active (i.e., emitting light) when a corresponding source is
providing power to redundant power module 1100. Further, LED 1118
may provide an indicator of a DC output, and may emit light when
power is provided by one of the sources or to indicate a charged
energy storage capacitor.
[0070] The rear panel 1104 includes connections for three AC
sources and a DC source, along with a DC output that may be
connected to devices powered by redundant power module 1100. A
plurality of connectors 1106, 1108, 1110, and 1112 may allow an
operator to measure electrical parameters associated with redundant
power module 1100. As described above, a voltage provided by a DC
source using connector 1106 may be compared to a voltage of
connector 1110 to determine whether an internal diode, such as
diode 908 in FIG. 9 has failed. If the internal diode has failed,
the input and output voltage will show a larger voltage drop than
would be expected if an internal diode is operational. Further, a
measurement of the electrical resistance between connector 1106 and
connector 1110 may provide an indication of whether the internal
diode is operational.
[0071] The rear panel 1104 may provide a visual indication, using
LED 1114, of whether an energy storage capacitor is charged. A
jumper 1116 may be used to discharge the energy storage capacitor.
The energy storage capacitor may be discharged before an operator
performs service or other types of work associated with redundant
power module 1100. As such, the visual indication may improve
operator safety. Jumper 1116 may be moved from the "NORMAL"
position illustrated in FIG. 11 to the position labeled
"DISCHARGE." In the DISCHARGE position, jumper 1116 may connect the
energy storage capacitor to a discharge resistor.
[0072] FIG. 12 illustrates a flow chart of a method 1200 of using a
redundant power module consistent with embodiments of the present
disclosure. At 1202, a redundant power module may receive
electrical energy from a plurality of power inputs. In various
embodiments, the power sources may comprise a current transformer,
a potential transformer, a station auxiliary transformer, a backup
generator, a battery backup system, or any combination thereof.
[0073] At 1204, electrical energy received from the plurality of
power inputs may be stored in an energy storage capacitor. The
systems illustrated in FIG. 3, FIG. 8, FIG. 9, and FIG. 10,
illustrate various configurations consistent with the present
disclosure. One of skill in the art will recognize that a wide
variety of other configurations may also be utilized.
[0074] At 1206, a redundant power module may provide a regulated or
an unregulated voltage at an output of the redundant power module.
The output may be powered by the plurality of power inputs when one
or more of the inputs is active. When power from the plurality of
power inputs is not available, power may be provided by the energy
storage capacitor. As energy in the energy storage capacitor is
depleted, the voltage of the output may decrease. A load powered by
the redundant power module may continue to operate until the output
no longer provides a sufficient voltage. For example, protective
relays may require a minimum voltage or drop-out voltage to
operate. Once the output falls below the drop-out voltage, the
relay may stop operating.
[0075] At 1208, a discharge selector may be moved from a first
position to a second position. In the first position, the discharge
selector may electrically couple the energy storage capacitor to
the plurality of power inputs and the output. In the second
position, the discharge selector may electrically couple the energy
storage capacitor to a discharge component. Jumper 1116 illustrated
in FIG. 11 is one example of a discharge selector consistent with
embodiments of the present disclosure.
[0076] At 1210, electrical energy stored in the energy storage
capacitor may be discharged using the discharge circuit. The
discharge circuit may be used to dissipate the energy stored in the
energy storage capacitor before an operator performs maintenance or
work on a redundant power module and/or a load connected to a
redundant power module. Dissipating the stored energy ensures that
the operator is not exposed to electric shock.
[0077] FIG. 13 illustrates a plot 1300 over time of an output
voltage of a redundant power module when providing energy to power
a trip event and when all input power sources are lost consistent
with embodiments of the present disclosure. The initial voltage,
V.sub.initial, is the output voltage of the redundant power module
after all sources are lost at time t=0. As illustrated, the output
voltage decays as power is drawn from an energy storage
capacitor.
[0078] FIG. 13 also illustrates various voltages that may be used
to calculate a ride through time for a given load. In one
hypothetical example, the load may be a trip coil. The time ti is
the maximum time following a loss of power before issuing a trip
command to ensure a successful trip operation. The minimum working
voltage of the trip coil, V.sub.f, is 60 volts, the operate time
for the breaker, T, is 100 ms, and a total load, P.sub.load,
including a relay that controls the coil of 25 watts, and an
initial voltage is 132 volts. A minimum voltage of a relay issuing
the trip command must be less than the minimum operating voltage of
the trip coil to ensure that the relay does not turn off before
successfully issuing the command. Eq. 1 may be used to calculate a
resistance, R.
R = 1.1 + V f 2 R coil V f 2 + P load R coil Eq . 1
##EQU00001##
Eq. 2 and Eq. 3 may be used to calculate a voltage at the time the
trip coil begins to operate, V.sub.t, and the resulting voltage
drop, V'.sub.t, respectively
V t ' = V f e T 0.126 R Eq . 2 V t = V t ' + 1.1 V t ' R coil Eq .
3 ##EQU00002##
Eq. 4 may be used to calculate the time,
t 1 = 0.126 ( V initial 2 - V t 2 ) 2 P load Eq . 4
##EQU00003##
The calculated value of the maximum ride through time may be
derated for component tolerance and a desired safety margin. Using
the values stated above, the value of R is 10.5.OMEGA., V'.sub.t is
64.7 volts, V.sub.t is 71.8 V, and time ti is 30.9 seconds. If a
derating factor of 0.7 is used, the redundant power module may
provide enough energy to trip the connected coil and operate the
relay for up to 21 seconds after the loss of all sources.
[0079] In accordance with the various embodiments described herein,
the reliable power modules may be used to provide operational power
to one or more loads such as protection devices, communication
devices, computers, trip coils, and the like. The operational power
may be provided even in the event of loss of all power sources for
a ride-through time. The operational power may be provided in order
to allow for disconnection of certain power sources. For example,
when maintenance needs to be performed on a DC power source, the AC
power sources continue to provide power to the reliable power
module (which continues to provide operational power to the loads),
allowing the DC power source to be removed during the maintenance.
AC power sources may parasitically obtain power from the electric
power delivery system. Each AC power source may be a different
phase of a three-phase electric power delivery system. Thus, all AC
power is only lost in the event of a three-phase fault on the
electric power delivery system. The ride-through energy of the
reliable power module(s) may be sufficient for a backup generator
to start up and energize inputs to the reliable power module(s).
Electric power output from a backup generator may be an input to
one or more reliable power modules.
[0080] Various modifications and changes may be made to the various
embodiments herein. For example, various embodiments of the
reliable power modules described herein may include more or fewer
or different power source inputs. A reliable power module may
include multiple DC inputs and/or multiple AC inputs. In another
example, the output of the reliable power modules may be rated at a
level different from what is described above. For example, the
output may be a 48V DC output. In other embodiments, the output may
be a 125V DC output. The output may be capable of, for example, 100
watts of continuous power while any power source is available to
the reliable power module, and during use of the energy storage of
the reliable power module.
[0081] The reliable power modules in accordance herewith solve
important electric power system problems. The reliable power
modules may improve the reliability of various systems such as a
system for control and protection of an electric power delivery
system. This is accomplished by feeding a DC output bus of the
reliable power module with four different sources such as, for
example, one DC and three AC sources. This allows multiple sources
to fail and the output bus of the reliable power module to still be
energized. In the event of loss of all input sources, the reliable
power module includes an energy storage device such as a capacitor
or capacitor bank that can power devices for seconds to minutes
depending on starting voltage and drop-out voltage. This device is
designed to be maintenance-free and may alarm when it fails, or
when a source is lost.
[0082] While specific embodiments and applications of the
disclosure have been illustrated and described, it is to be
understood that the disclosure is not limited to the precise
configurations and components disclosed herein. Accordingly, many
changes may be made to the details of the above-described
embodiments without departing from the underlying principles of
this disclosure. The scope of the present invention should,
therefore, be determined only by the following claims.
* * * * *