remedial action schemes (ras) - washington state … action schemes (ras) presented by brant heap...
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Remedial Action Schemes (RAS)Remedial Action Schemes (RAS)
Presented by
Brant HeapSalt River Project
Hands-On Relay School
March 19th, 2014
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OverviewOverview
What is a RAS
Why are RASs Needed?
RAS Classifications and Types
Composite of a RAS Scheme
RAS Design
RAS Testing
RAS Scheme Review
RAS Examples
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What is a RAS?What is a RAS?
Synonymous Acronyms
RAS – Remedial Action Scheme (WECC)
SPS – Special Protection Scheme (NERC, others)
SIPS – System Integrity Protection Scheme (IEEE)
Automatic protection system designed to detect abnormal
predetermined system conditions and takes a predefined
action to prevent a system problem
Take corrective actions other than and/or in addition to the
isolation of faulted components to maintain system
reliability
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What a RAS is not?What a RAS is not?
Fault conditions that must be isolated with standard
relaying schemes
Underfrequency or Undervoltage Load Shedding
Out of Step Relaying that is not an integral part of a RAS.
Sub-synchronous resonance (SSR) protection schemes.
Auto reclosing schemes
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RAS or Other Alternative?RAS or Other Alternative?
Responds to low probability events in the system
Increases path capacity without building more
power lines
A $1m RAS in place of a $50-$200m transmission line
Operating transfer capability on a path could quadruple
with a RAS
Helps balance load and generation after a loss of
one or the other
Increases overall system reliability
Meet project schedules
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What is a RAS SummaryWhat is a RAS Summary
RAS schemes are implemented to solve single and credible multi-
contingency problems not protected by standard equipment
protection.
Major applications of RAS include:
Increasing power transfer
Add reactive support
Limit scale of cascading outages
RAS schemes address specific pre-determined problems such as:
Equipment overloads, Low voltages, Unstable generation , and unstable
load.
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RAS CLASSIFICATIONS
AND
TYPES
RAS CLASSIFICATIONS
AND
TYPES
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Wide Area Protection Scheme (WAPS)
Local Area Protection Scheme (LAPS)
Safety Net (SN)
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Wide Area Protection Scheme:
WAPS
Wide Area Protection Scheme:
WAPS
Wide Area Protection Scheme (WAPS): A Remedial Action
Scheme whose failure to operate WOULD result in any of the
following:
Violations of TPL – 001-WECC-RBP-2 System Performance RBP
Maximum load loss ≥ 300 MW
Maximum generation loss ≥ 1000 MW
Wide Area RASs require higher reliability requirements and a more
thorough review from WECC RASRS subcommittee as compared to
Local Area and Safety Nets
Meets WECC’s performance requirements.
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Local Area Protection Scheme:
LAPS
Local Area Protection Scheme:
LAPS
Local Area Protection Scheme (LAPS): A Remedial Action Scheme
whose failure to operate would NOT result in any of the following:
Violations of TPL – 001-WECC-RBP-2 System Performance RBP
Maximum load loss ≥ 300 MW
Maximum generation loss ≥ 1000 MW
LAPS scheme will be reviewed by the RASRS for classification only.
Meets owner’s performance requirements with owner’s system.
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Safety Net: SNSafety Net: SN
Safety Net: A Remedial Action Scheme designed to remediate TPL-
004-0 (System Performance Following Extreme Events Resulting in
the Loss of Two or More Bulk System Elements (Category D)), or
other extreme events.
Remediation of extreme events is not required by NERC or WECC.
An optional, extreme event remediation scheme is a RAS and classified as a
Safety Net
A scheme used to provide a defense against extensive cascading or complete
system collapse.
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WECC Remedial Action Scheme
type definitions.
WECC Remedial Action Scheme
type definitions.
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Event-based
Directly detect outages and/or fault events and initiate actions.
Parameter-based
Measure variables for which a significant change confirms the
occurrence of a critical event.
Response-based
Monitor system response during disturbances and react to actual
system conditions.
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Types of RASTypes of RAS
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Local RAS ExampleLocal RAS Example
A RAS trips 400 MW of generation to relieve a thermal line
overload following a single contingency.
• The WECC TPL RBP doesn’t mention thermal overloads,
so this criterion does not apply here,
• The maximum load loss is less than 300 MW, and
• The maximum generation loss is less than 1000 MW.
This scheme is a LAPS because it remediates a single
contingency (no SN), WECC TPL RBP doesn’t apply, and
generation and load loss levels are below those trigger levels
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Local RAS ExampleLocal RAS Example
Wilder
Landon
Walnut Grove
Ingalls
500kV
500kV
500kV
345kV
Unit 1 online
Unit 2 online
Bypass Series Caps
500kV
With series capacitors installed on the Landon-Walnut Grove line, there is a concern of SSR problems on the generators if radial. Local RAS scheme in place to bypass series capacitors if generating while radial.
Is this event or
parameter based?
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Wide Area RAS ExampleWide Area RAS Example
OREGON
COI
California/Oregon
Inter-tie (Path 66)
Palo Verde
Nuclear Generating
Station
Phoenix
ARIZONA
CALIFORNIA
•Loss of 2 units at Palo Verde while running above
2550MW would cause instability to the Calif/Oregon
Inter-tie (COI)
•Required load shed of at least 120MW to mitigate
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QuestionQuestion
Studies show that the failure of the A RAS would result in the loss of
300MW of load and 900MW of generation. The studies also show there
are no Violations of TPL – 001-WECC-RBP-2 System Performance RBP.
Is this RAS a LAPS or WAPS?
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COMPOSITE OF A RASCOMPOSITE OF A RAS
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Composite of a RAS SchemeComposite of a RAS Scheme
Problem to Mitigate
The issue that needs to be reduced or eliminated.
Arming Condition
Permissive for RAS to operate.
Trigger Condition
Causes the scheme to operate if armed.
Operate
What the Scheme does to mitigate the problem.
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Problem to mitigate Arming Condition
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Problem to MitigateProblem to Mitigate
RAS are generally designed to mitigate three types of power
system problems and time scales:
• Thermal (minutes)
• Voltage Stability (seconds to minutes)
• Transient Stability (cycles to seconds)
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Problem to MitigateProblem to Mitigate
Thermal Overload (Fast: seconds or minutes)
Result from excessive currents flowing through transmission
circuits caused by heavy loads
Can cause overheating, line sags, and loss of conductor
strength
These RAS schemes can take sec/min rather than a few cycles
Examples of mitigation include backing generation or load
shedding
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When a line loaded above it’s Surge
Impedance Level (SIL), it acts like a
shunt reactor absorbing Mvars. This
pulls the voltage down and puts the
system at risk of a voltage collapse.
The reactance causes voltage problems
before resistance heating causes thermal
problems.
Examples of mitigation include shunt
cap insertion or gen drop
Problem to MitigateProblem to Mitigate
Voltage Instability (faster: cycles or seconds)
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Transient Instability (fastest: 8-30 cycles)
Disturbance which does not allow a generator to deliver its
power into the network. (i.e. sudden line outages)
Power then absorbed by generator resulting in sudden
acceleration of the rotor and eventually cause damage of the
generator
Examples of mitigation include fast gen drop or use of
braking resistor
Problem to MitigateProblem to Mitigate
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The permissive for a RAS to operate. We typically arm a
RAS based on changes in critical system conditions.
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Arming ConditionArming Condition
Line out of Service
Generation Output
Line Loading
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Trigger ConditionTrigger Condition
The trigger condition is what initiates the Operation actions.
Like the Arming condition, the Trigger condition is often a
change in or loss of a critical system.
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Loss of GenerationLoss of Line
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OperateOperate
What actions the Scheme takes to mitigate or prevent the
problem.
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Cap Insertion
SWT
BKR
Cap Bypass
Load Shed
Gen Drop
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RAS Composite OverviewRAS Composite Overview
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RAS
Problem
Thermal
Voltage
Transient
Arming
Line Loading
Gen Output
Line OOS
Trigger
Line Loss
Generation Generation Loss
Operate
Cap Insert
Cap Bypass
Gen Drop
Load Shed
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Local RAS ExampleLocal RAS Example
Wilder
Landon
Walnut Grove
Ingalls
500kV
500kV
500kV
345kV
Unit 1 online
Unit 2 online
Bypass Series Caps
500kV
Problem to Mitigate: SSR concerns when generating radial with series compensation in service.
Arming Condition: Series Compensation in service.
Trigger Condition: Loss of Landon- Ingalls line OR los of Wilder-Landon line.
Operate Condition:Bypass series compensation.
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RAS Example 1RAS Example 1
Desert Basin 230kV
Casa Grande 230kV
Saguaro 230kV
Santa Rosa 230kV
Casa Grande – Saguaro 230kV line
Initially out of service (IOS)
To Tatmomli
To Knox
To TesttrakCasa Grande 69kV
Santa Rosa 69kV
Fault occurs on DBG-
Santa Rosa 230kV line
The only outlet for DBG
generation is 100MVA Casa
Grande 230/69kV transformer
Problem to Mitigate
•Voltage dip at DB 230kV bus
and neighboring busses
•Casa Grande 230/69kV
transformer overload
Thermal & Voltage Instability
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RAS Example 1RAS Example 1
GR
OS
S D
BG
OU
TP
UT
TH
RE
SH
OL
D (
MW
)
TERMINAL VOLTAGE (kV)
585
630 630
550558
567575
583
543535
525
465
510503
517
630627620
613607
600
590
576570
535
465
485
505
525
545
565
585
605
625
645
0.975 0.98 0.985 0.99 0.995 1 1.005 1.01 1.015 1.02 1.025 1.03 1.035 1.04 1.045 1.05
RAS Armed CT1 trip CT1&CT2 trip
1.042
583
18 18.3618.2718.1818.09 18.6318.5418.45 18.8118.72 18.917.64 17.73 17.82 17.9117.55
NOT ARMED
REGION 1CT1 or CT2 ARMED TO TRIP
REGION 2CT1 and CT2 ARMED TO TRIP
Arming Condition
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ARMED SIGNALTO SEL321 RELAY
DCS
TOTAL MWSIGNAL
TERMINALVOLTAGESIGNAL
PLC
GENERATING INOPERATING REGION
RAS Example 1RAS Example 1
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Santa Rosa Line
RAS Example 1RAS Example 1
ARMED SIGNALFROM PLC
SEL321 Relay
LOCKOUT
OUTPUT
CT1
CT1GEN BKR
CT2
CT2GEN BKR
SELECTOR SWITCHCT2
CT1
&
CT2
CT1
&
CT2
CT1
Trigger Condition
•Fault on the Santa Rosa Line
Operate – Method of Mitigation
•Gen Drop
Trigger & Operate
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Average Time Elapsed fromSanta Rosa Line Fault to Generator Breaker Trip:
RAS A = 5.8 cyclesRAS B = 6.0 cycles
Indicates Timing Test Verified
T = 01.5 62.5
Time in Cycles
Timing Test Results
RAS Example 1RAS Example 1
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DESIGN COMPONENTSDESIGN COMPONENTS
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Design Components OverviewDesign Components OverviewLogic
Logic diagrams, timing diagrams, flow charts, etc.
RAS Controllers
Relays, PLCs, DCS
Detection and Initiating Devices
Sensing
CTs/PTs, Transducers
Input/Outputs
Breaker status, trip coils, control outputs, etc.
Communications
High reliability
High availability
Appropriate timing
Monitoring and Alarms
Equipment self diagnostics, telecom., RAS actions, etc.
Redundancy, Redundancy, Redundancy!
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LogicLogic
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Detailed logic documentation is KEY to a successful RAS design and implementation.
Logic documentation comes in many forms such as, flow charts, written descriptions,
equations, timing tables, and logic diagrams.
Scheme logic will direct the design, aid in reviews, assist operating personnel, and provide
support for testing and troubleshooting the scheme.
Logic can become very complex and should be designed to maximize reliability, minimize
complexity, allow safe scheme testing, and allow for easy modifications.
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Logic Chart: Arming AlgorithmsLogic Chart: Arming Algorithms
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Logic Diagram ExamplesLogic Diagram Examples
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ARMED
LOSS OF LINE 1
RAS Armed
LOSS OF LINE 2
LOSS OF LINE 3
UNIT TRIP LOGIC
TRIP TEST
RAS IN TEST
10cy
4ms
Timer 14
pu = 4ms
do = 10cy
Test Logic
LLL
LLL
LLL
TRIP PB
IN TEST
Communication Failure
Trip/Operate Logic
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RAS ControllersRAS Controllers
Microprocessor Relay
40Distributed Control System (DCS)
Programmable Logic Controller
(PLC)
RAS controllers come in many different forms
Things to consider when selecting a RAS controllerComplexity of scheme logic and processing requirements
Reliability
Availability
Functionality
Maintainability
Familiarity with maintenance personnel
Expandability
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Detection and Initiating DevicesDetection and Initiating Devices
Detection and initiating devices are the link between the field
and RAS controller. Some provide real time system
conditions for accurate logic processing while others securely
perform actions when requested.
• Some of their purpose are to provide, line open status,
generation output, line loading, and etc.
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Detection and Initiating Devices
Sensing Equipment
Detection and Initiating Devices
Sensing Equipment
Transducers
42
Current Transformers (CTs) Potential Transformers
(PTs,CCVTs)
• Voltage• Current• Power• Frequency
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Detection and Initiating Devices
Inputs and Outputs
Detection and Initiating Devices
Inputs and Outputs
43
Disconnect StatusControl Inputs
• Breaker status• Disconnect status• Breaker trip bus monitoring
• Manual arming• Local/remote disabling
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Detection and Initiating DevicesDetection and Initiating Devices
Detection and initiating devices need to be secure and
reliable.
Several devices are often needed in combination to provide
accurate and secure indication.
A good example of this is ‘line open detection’. To
determine the correct status of a line we may need inputs
form several devices:
Breaker status
Disconnect status
Undercurrent detection
Breaker trip bus monitor
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Detection and Initiating Devices
Loss of Line Examples
Detection and Initiating Devices
Loss of Line Examples
45
BKR1 BKR2 BKR3 BKR4
Protected Line
Line Loss Logic (LLL): Breaker Status
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Detection and Initiating Devices
Loss of Line Examples
Detection and Initiating Devices
Loss of Line Examples
46
BKR1 BKR2 BKR3 BKR4
Protected Line
Line Loss Logic (LLL): Trip Coil Energized
Often used to increase speed of RAS operation.
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CommunicationsCommunications
47
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CommunicationsCommunications
48
RAS are highly dependent on high-speed telecommunications.
Communication channels must meet at least the same criteria as other relaying
protection communication channels.
The scheme logic must be designed so that loss of the channel, noise, or other channel
failure will not result in a false operation of the scheme.
All channel equipment must be monitored and alarmed to the dispatch center so that
timely diagnostic and repair action shall be take place upon failure.
Leased telephone circuits or pilot wire circuits on power system structures will most
likely lead to unreliable operations. Such channels shall only be used when no other
communications media are available. Automatic channel testing and continuous
monitoring are required if telephone leased lines are used.
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CommunicationsCommunications
49
RAS scheme communications must have high Reliability, Availability, adequate
Redundancy, and appropriate Timing.
Reliability: the assurance that the system operates correctly. It will respond when
intended and restrain when not intended (…Dependability and Security)
Availability: how often is the system functioning at or above its required performance
level.
Redundancy: this helps improve the availability as well as allow for maintenance.
Communication system Timing: how long it takes for the communication system to
receive the packet from the device, transmit the packet across the network, and transfer
the packet back to the device. (…note that the complete End-to-End timing must also
consider the relay detection time, encoding time, device operation time, etc.)
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CommunicationsCommunications
50
End-to-End Delay
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CommunicationsCommunications
51Typical RAS Functions with Availability References
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Monitoring and AlarmsMonitoring and Alarms
52
Minimum Monitoring Should Include
Arming status
Initiating device operation
Telecommunications
Tripping device operation
Status of operation or test switches
Equipment self-diagnostics and annunciation
Indication when a manually armed scheme should be armed or may be disarmed.
The monitoring of a RAS scheme is crucial.
All critical alarms and indication shall have adequate time stamping and be
made available to system operators.
RAS failures typically require system operators to adjust the transmission
system. This often requires the reduction of flow on major paths and
backing of generation.
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Redundancy, Redundancy, Red…Redundancy, Redundancy, Red…
53
RAS redundancy requirements are similar to
the requirements for other protection
systems.
Redundancy is intended to allow removing
one scheme following a failure or for
maintenance while keeping full scheme
capability in service with a separate scheme.
Redundancy requirements cover all aspects
of the scheme design including:
Detection, arming, power supplies,
telecommunications facilities and equipment,
logic controllers (when applicable), and RAS
trip/close circuits.
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54
Design Components ReviewDesign Components ReviewLogic
Logic diagrams, timing diagrams, flow charts, etc.
RAS Controllers
Relays, PLCs, DCS
Detection and Initiating Devices
Sensing
CTs/PTs, Transducers
Input/Outputs
Breaker status, trip coils, control outputs, etc.
Communications
High reliability
High availability
Appropriate timing
Monitoring and Alarms
Equipment self diagnostics, telecom., RAS actions, etc.
Redundancy, Redundancy, Redundancy!
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RAS Controller SchematicRAS Controller Schematic
55
BKRStatuses
Control
InputsRemote/Local
Trip Coil Monitors
MonitoringRemote/Local
Local Control
Switch.Normal, Disable, &
Test
Relay Contact Chart
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Panel Layout ExamplePanel Layout Example
RAS A
RAS B
Disable
Switches
56
LOCKOUTS
SELECTORSWITCHES
TESTSWITCHES
FT-19CUTOFF BLADES
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Panel Layout ExamplePanel Layout Example
RAS A Currents
& Potentials
RAS A Currents
& Potentials
RAS B DCRAS B DC
RAS B Control,
Alarms, Status
RAS B Control,
Alarms, Status
RAS B Currents
& Potentials
RAS B Currents
& Potentials
All cables redundant
Power supply fusing
redundant
RAS A wiring on
one side of panel,
RAS B wiring on the
other
RAS A DCRAS A DC
RAS A Control,
Alarms, Status
RAS A Control,
Alarms, Status
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Panel Layout ExamplePanel Layout Example
RAS ARAS A
RAS BRAS B
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Panel Layout ExamplePanel Layout Example
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Three-lineThree-lineThree-lineThree-line
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Commissioning and Maintenance
Testing
Commissioning and Maintenance
Testing
Acceptance Checks
Verify the functionality of the relay inputs/outputs
Scheme Checks
Verify the wiring and all new physical connections to
controllers/relays
Verify operation of lockouts when trip outputs are initiated
Logic Testing
Verify operation of relay settings and logic of each relay
End-to-end Testing
Verify data transfer between relays
Initiate trigger condition and verify operation
Verify timing requirements are satisfied.
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62
RAS Scheme WECC ReviewRAS Scheme WECC Review
Remedial Action Scheme Reliability
Subcommittee (RASRS)
Originally a task force in 1985
In 2005, task force was designated a subcommittee
reporting to WECC
Committee consists of knowledgeable representatives
from several region utilities with backgrounds in
communication, automation, planning, operations, and
relaying.
Reviews the RAS designs to ensure reliability and no
single points of failure that would result in Bulk
Electric System performance outside of WECC
performance limits
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63
RAS Scheme WECC ReviewRAS Scheme WECC Review
When is RAS Review Required?
Prior to initial installation and commissioning.
Before significant modifications.
Removal of the scheme from service.
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More RAS Scheme ExamplesMore RAS Scheme Examples
64
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RAS Example 2RAS Example 2
System Changes
Addition of new generating unit at Longhorn
Potential Conditions
Overload of path 4
Post-transient voltage stability
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66
Fredette
BuckeyeCougar
Jayhawk
345kV 500kV
Unit 1
Unit 2
Problem to Mitigate: Thermal overload on Path 4 and voltage
stability problems on neighboring busses
Arming Condition: Load on Buckeye-Jayhawk line exceeds
800MW
Trigger Condition: Loss of Buckeye-Jayhawk Line
Operate Condition:•Insert shunt cap within 10 cycles
•Trip Buckeye Unit 1 within 60 cycles
Longhorn
345kV500kV
Shunt Cap
Irving Substation
Thermal & Voltage Instability
RAS Example 2RAS Example 2
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Reclosing SummaryReclosing Summary
Avoid tripping generation at Buckeye if fault is momentary
Reclosing added on Buckeye-Jayhawk lineBU932, BU935
JH932, JH935
Reclosing can be enabled/disabled locally or remotely
Reclosing is in-service if…Reclosing is enabled
RAS is armed
Breaker is initially closed
5 minutes has elapsed since last reclose
Jayhawk will reclose first 35cy after fault inception
Buckeye will reclose 55cy after fault inception only if reclose was successful at Jayhawk
Reclose only has 1 shot per fault
RAS Example 2RAS Example 2
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68
Reclosing OperationReclosing Operation
Jayhawk
Unit 1
JH932
Buckeye
JH935 BU935 BU932
Initial Conditions:•Reclosing enabled on JH932 and BU932•RAS is Armed•79RB In-service = RAS Armed and Reclosing Enabled
79RB Enabled 79RB Enabled
79RB In-service 79RB In-service
Operation Scenario 1 (momentary fault):1. Fault occurs on BU-JH line2. All breakers associated with line open3. After 35 cycles from initial fault, JH932 recloses successfully4. After 55 cycles from initial fault, BU932 recloses successfully5. Unit 1 at Buckeye is not tripped (High speed caps still insert)6. RAS remains armed
RASArmed
RAS Example 2RAS Example 2
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69
Reclosing Operation (cont’d)Reclosing Operation (cont’d)
Jayhawk
Unit 1
JH932
Buckeye
JH935 BU935 BU932
Initial Conditions:•Reclosing enabled on JH932 and BU932•RAS is Armed•79RB In-service = RAS Armed and Reclosing Enabled
79RB Enabled 79RB Enabled
79RB In-service 79RB In-service
Operation Scenario 2 (sustained fault):1. Fault occurs on BU-JH line2. All breakers associated with line open3. After 35 cycles from initial fault, JH932 recloses into fault4. JH932 trips5. BU932 never attempts to reclose6. After 55 cycles from initial fault, Unit 1 at Buckeye is tripped 7. RAS disarms
RASArmed
RAS Example 2RAS Example 2
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RAS Example 2RAS Example 2
Shunt Cap Overview
230kV Shunt caps at 2 sites may be used.
Breakers are used for high speed insertion
Shunt cap at IR is used for RAS exclusively.
Shunt cap at CRABB is normally used for voltage control
but can be switched to be used for RAS under certain
circumstances. Cap must be configured by Operations for
high speed insertion for use in RAS.
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RAS Example 2RAS Example 2
Irving
SWT
BKR IR658
IR655
Crabb
SWT
BKR CRB618
CRB615
• Crabb cap bank is typically used for operational voltage control but may be configured for use in RAS.
Shunt Cap Normal
Operation
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RAS Example 2RAS Example 2
Irving
SWT
BKR IR658
IR655
Crabb
CRB618
CRB615SWT
BKR
Operation Scenario (Irving is “Not Available”):1. Operations receive IR Cap Bank Not Available alarm2. Operations make Crabb available for high speed by opening CRB618 and closing CRB6153. Dispatch personnel to Irving to troubleshoot problem4. Once alarm at Irving is clear, switch back to normal
SWT
BKR
IR Cap
Bank
Not Avail
Shunt Cap at KI or
IR “Not Available”
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73Example RAS Communication Network
RAS Example 2RAS Example 2
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MAIN N60
RAS1
MAIN N60RAS2
MAIN N60RAS3
MAIN N60MISC
C70 ARAS2
C70 BRAS1,2
C70 CRAS1,2
C70 DRAS1,2
ETHERNET
LAN
N60 ARAS1,2,3
N60 BRAS3
N60 CRAS2
N60 ERAS1,2
N60 GRAS3
G.703
N60 FRAS1,2,3
N60 DRAS2,3
RAS Example 2RAS Example 2
Example RAS Simplified Communication Network
• Bandwidth to meet time constraints
• Low data error
• High availability
• Relays can exchange data with any other
relay in its network or ring
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RAS Example 2RAS Example 2
Relay Fail – Relay is failed or communication has failed and relay will not function as designed
Relay technician should be dispatched to diagnose problem
Communication technician may need to be involved as well
Diminished RAS – RAS is still operational, but is one condition away from being non-operational
Direct Ring break causes this alarm and System Protection should be contacted to find location of break
RAS Disabled – RAS is disabled either locally or by SUPY
RAS in Test – RAS system has been placed in “test” at site and is non-operational
RAS Armed – RAS system is armed and will operate under the required trigger conditions
RAS Operated – At least one component of the RAS has operated successfully
Dispatcher should follow recovery procedure
Alarm/Status Summary & Response
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Utility C
76
+
1 2
Fredette
BuckeyeCougar
Jayhawk
345kV 500kV
Longhorn
345kV
500kV
Shunt Cap
Irving
RAS Example 2: Big PictureRAS Example 2: Big Picture
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77
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• A new 600MW unit was installed at Phoenix Generating Station (PGS).• Due to the added generation, series capacitors were installed on the
transmission system to increase the path operating capabilities. • New studies were performed modeling the additional generation and line
capacities. The studies identified several system configurations that would
result in transient instability violations and possible damage to the PGS units.• The Phoenix RAS was designed to mitigate the adverse effects of the added
generation and line capacities in lieu of building an additional 300 mile line.
79
Mesa500kV
Unit 1
Gilbert500kV
Unit 2
Scottsdale500kV
Unit 3
Phoenix
PhoenixGenerating
Station
600MW
600MW
600MW
New Series Capacitors
New 600MW Unit
RAS Example 3
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ARM
Problem to Mitigate: Transient angle instability at Phoenix will cause
Phoenix Generating Station to go out-of-step and trip off line.
Arming Condition 1: Series capacitors bypassed on Mesa/Phoenix line
and Gilbert/Phoenix line and PGS >= 1050MW.
Trigger Condition 1: Loss of Phoenix/Scottsdale line
Operate Condition 1:•Trip Unit 3 within 15 cycles
80
Mesa500kV
Unit 1
Gilbert500kV
Unit 2
Scottsdale500kV
Unit 3
Phoenix
PhoenixGenerating
Station
600MW
600MW
600MW
ARM
TriggerOperate
RAS Example 3-1
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ARM
Problem to Mitigate: Transient angle instability at Phoenix will cause
Phoenix Generating Station to go out-of-step and trip off line.
Arming Condition 2: Series capacitors bypassed on Scottsdale/Phoenix
line and Gilbert/Phoenix line and PGS >= 1050MW.
Trigger Condition 2: Loss of Mesa/Scottsdale line
Operate Condition 2:•Trip Unit 1 within 15 cycles
81
Mesa500kV
Unit 1
Gilbert500kV
Unit 2
Scottsdale500kV
Unit 3
Phoenix
PhoenixGenerating
Station
600MW
600MW
600MW
ARM
Trigger
Operate
RAS Example 3-2
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Problem to Mitigate: Transient angle instability at Phoenix will cause
Phoenix Generating Station to go out-of-step and trip off line.
Arming Condition 3: Mesa/Phoenix line IOS and PGS >= 800MW.
Trigger Condition 3: Loss of Phoenix/Scottsdale line or loss of
Phoenix/Gilbert Line
Operate Condition 3:•Trip 2 units off within 20 cycles.
82
Mesa500kV
Unit 1
Gilbert500kV
Unit 2
Scottsdale500kV
Unit 3
Phoenix
PhoenixGenerating
Station
600MW
600MW
600MW
RAS Example 3-3
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• The Phoenix RAS is dynamic and automatically selects and trips units based on which
line goes out of service.
• At times, Operations wants the ability to select which units trip offline.
• Under certain circumstances this is ok but must be done with caution to avoid tripping to
black plant
83
Mesa500kV
Unit 1
Gilbert500kV
Unit 2
Scottsdale500kV
Unit 3
Phoenix
PhoenixGenerating
Station
600MW
600MW
600MW
PHX11 PHX12 PHX13
PHX21 PHX22 PHX23
PHX31 PHX32 PHX33
PHX41 PHX42 PHX43
Lets consider our previous example of RAS-3 but this time we will have PHX12 out on maintenance and Unit 2 manually selected to trip
RAS Example 3-4
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Exercise: University LAPSExercise: University LAPS
WSU
ORE USC
ASU
University Generating Station
230kV
230kV 230kV 230kV
230kV
12 Units 50 MW each
Total = 600 MW
More than 4 units are online
The only outlet is
through USC’s 69kV
system.
Fault occurs on the
WSU/ASU line and
WSU/ORE line
…or a fault occurs on the
WSU/ASU line and ORE/USC line
All but 4 units trip offline within
15cycles.
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Without University LAPS installed.
With University LAPS Installed
Study Results
Exercise: University LAPS
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Exercise: University LAPSExercise: University LAPS
What is the problem to mitigate?Voltage dip at ASU 230kV bus and neighboring busses
Thermal overloads on neighboring 69kV lines out of USC
What is the arming condition?More than 4 generators on line
What is the Tripping condition?Loss of ASU/WSU line and loss of either WSU/ORE or ORE/USC line
What are the operating actions?
Trip all but 4 generators off line with 15cycles.
86
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Exercise: University LAPSExercise: University LAPS
87
UNIT TRIP LOGIC
10cy
4ms
ARMEDLLL
ASU/WSU
LLL
WSU/ORE
LLL
ORE/USC
Using the Trigger conditions create the Operate logic (unit trip logic) using the information
shown below.
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Exercise: University LAPSExercise: University LAPS
88
WSU ORE USC ASU
WSU11
WSU10 ORE10 ORE20 USC20USC10
ASU21
ASU20ASU10
LINE 1 LINE 2
LINE 3
LINE 1 LINE 2
Now that we have the Operate logic, lets create the Line Loss Logic and Arming Logic.
Use only 52b status and Trip Coil Monitor.
WSU20
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Exercise: University LAPSExercise: University LAPS
89
WSU ORE USC ASU
WSU11
WSU10 ORE10 ORE20 USC20USC10
ASU21
ASU20ASU10
LINE 1 LINE 2
LINE 3
LINE 3
Now that we have the Operate logic, lets create the Line Loss Logic and Arming Logic.
Use only 52b status and Trip Coil Monitor.LOSS OF LINE
10cy
Timer 2
pu = 0cy
do = 10cy
0cy
10cy
Timer 3
pu = 0cy
do = 10cy
0cy
10cy
Timer 4
pu = 0cy
do = 10cy
0cy
10cy
Timer 5
pu = 0cy
do = 10cy
0cy
WSU20
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90
QUESTIONSQUESTIONS
Is my lanyard
connected?