1. Commissioning: Best Practices and Possible Traps
Douglas Kirby P. E., LDWP
Dan Shield P. Eng., AESO
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Commissioning Errors
Commissioning Protective Relay Systems is one of the most complex tasks to be done on the Power System.
There are many reasons why mistakes are made.
These mistakes can lead to misoperations, including customer outages and circuit interruptions.
If we follow the Best Practices in this presentation, the severity and frequency of misoperations will be reduced or eliminated.
A white paper will be produced by the WECC RWG regarding these best practices in 2019.
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Why?
Why should we care about this?
We are all here to improve the reliability of the power grid.
Efforts are underway to effect a nationwide misoperation rate of 8 percent by 2020.
The WECC Misoperation Workshop and Reduction Strategy are Western Interconnection efforts to contribute to the reduction.
Another way to work toward this goal is to reduce commissioning errors.
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Where does this apply?
Good news!
Best Practices for Commissioning Protection Systems are applicable to Generation, Transmission, and Distribution circuits.
So no matter how big or small your Power System is…
THIS PRESENTATION IS FOR YOU!
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Prerequisites
Some of the foundational things you will need to be successful:
Well-trained workforce – This is very important. It can be comprised of internal or contractor personnel, but you need to have trained and qualified personnel for commissioning.
Good documentation
Good/Consistent design standards
Good/Consistent setting practices
Good/Consistent electrical schematics and drawings
Good work processes and procedures
A desire to constantly improve
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6. Why are these ‘Best Practices’?
With 60 years of experience between them, the authors of this presentation have identified the activities that could lead to a reduction in errors during the commissioning process.
Matching these activities to misoperations reported across the WECC region in the last three years highlights what to focus on.
Each Best Practice is analyzed to identify which will yield the most ‘bang for the buck’.
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Order Significance?
The Best Practices are listed in the order by which they would appear in a normal project.
There is some variation from company to company in this sequence, but generally this is the pattern that most utilities will follow.
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Best Practice #1
Best Practice
Related Misoperation
Verify intended protection schematic is consistent with company design standards.
Confirm that actual wiring matches design standard. Resolve differences. Deviations = RISK!
Relay applied design was not correct for application
Relay operated as designed, but test personnel not familiar with intended design
Settings did not match wiring
Pending settings were not implemented
Not adequately protected during commissioning.
Not configured as designed and intended.
How often?
13% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #2
Best Practice
Related Misoperation
Point-to-point wiring verification of all protection system wiring. Check against intended design. Initial verification at relay panel shop or site before installation.
If this is an upgrade to an existing installation, utilize methods to identify wiring that will be involved in isolation and removal. Color code prints to identify circuits to remove, and retain as well as new circuits.
CT wiring was rolled
Labels were not present for blocking switches of pressure relay, resulted in pressure relay trip during maintenance work on reactor.
How often?
9% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #3
Best Practice
Related Misoperation
Load production relay settings and test to make sure desired setting is installed. For first-time installation of new 'Standard' settings, perform extensive detailed testing and evaluation.
Relay Technician put incorrect settings on relay.
Design Engineer issued incorrect settings.
How often?
13% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #4
Best Practice
Related Misoperation
Verify all CT/PT ratios against setting sheets and document that they are properly set.
Check CT circuit for proper grounding. Single point of grounding is preferred to prevent ground loops.
Use current as a secondary method to check that all CT wiring has been verified. (E.g., push from the CT for each phase to neutral to verify that the neutral leg of the circuit has not been accidentally left open.)
CT was wired with wrong polarity.
CT was wired with wrong ratio.
CT's were incorrectly grounded
Open neutral wire
Secondary wiring for CT polarization circuit was miswired.
How often?
16% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #5
Best Practice
Related Misoperation
Do secondary tests on CT’s to verify expected performance and establish a baseline.
CT shorted, miswired (delta-wye, wye-delta), open circuited, etc
How often?
22% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #6
Best Practice
Related Misoperation
PT’s need to be tested when they are new using established PT testing procedures by your company. If existing or when initial testing is complete, the load test will be used to validate PT phasing and polarity against a known source such as an adjacent circuit.
Loss of voltage unexpectedly due to crews in station resulted in loss of directionality and resultant trip.
Loss of voltage due to missing fuses in circuit taken out during previous outage resulted in misoperation.
Removal of CVT wiring due to non-standard company procedure resulted in misoperation.
How often?
4% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #7
Best Practice
Related Misoperation
Verify all telecommunication equipment is operational and programmed as desired.
Verify maximum latency times and failover times.
For systems with Telecommunications-aided protection schemes or locations that are critical to the system, it is advisable to generate dynamic test routines using state simulated events based on relay system fault parameters. Satellite synchronized test equipment is necessary for testing at remote facilities.
Failed to verify comm channel is configured to match the circuit configuration.
Failed to verify comm channel is in proper configuration (cutoff switch normal, etc.)
Protection element coordination issue between relay and communication equipment.
How often?
6% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #8
Best Practice
Related Misoperation
Trip check each relay for all phases and verify each expected output. Use schematic drawing as a reference to make sure all inputs/outputs are operating correctly.
Perform load test with system load to verify overall relay performance. Verify CT/PT ratios via the protection relay once energized.
Test switches left open (CT/PT)
Circuit restored with damaged/broken wires in CT/PT circuits
Circuit restored with failed equipment in trip circuit.
Relay setpoint and status of relay tap setting not verified.
CT connections changed during outage and no load test was done to verify that the proper polarity was achieved.
How often?
16% of “As-left Personnel Errors” from WECC Active misoperations
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Best Practice #9, 10, and 11
BP #9
Check all SCADA alarms to System Operator or monitored location for that alarm/trip condition.
BP #10
Evaluate load test results against expected values. Flag any discrepancies and follow up.
BP #11
Submit complete test result package to Supervisor or O&M team for use as baseline information for future testing and PRC-005 compliance.
All three of these did not result in misop during our sample period, but could result in misop for future or during maintenance cycle.
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What’s Next
Hopefully you can take some of these Best Practices back with you and compare them to what you are currently doing.
Pay special attention to the top three.
Did you already see the trends and have you identified the top three?
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18. Have any of your own to share?
If you have a practice that works for you and you want to share it, send it to the WECC Relay Work Group (RWG)
The submittals will be evaluated for possible inclusion into a future white paper by the WECC RWG on this topic.
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Questions
Dan Shield, Director Transmission Engineering; AESO
Douglas Kirby, Asst. Mng. Substation Operations; LADWP
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Conclusions
Commissioning modern Protective Relays comes down to…
Settings and Scheme selection. Getting the right scheme and setting for the application.
CT and PT connections – You have to have the right CT/PT connections or the protection will not work correctly.
Trip Testing and Load Testing. A critical final step to make sure that nothing was overlooked during commissioning.
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21. Top Three Best Practices for Commissioning
22% - Secondary tests on CT's to verify expected performance and establish a baseline.
16% - Verify all CT/PT ratios against setting sheets and document that they are properly set.
Check CT circuit for proper grounding. Single point of grounding is preferred to prevent ground loops.
Use current as a secondary method to check that all CT wiring has been verified. E.g. push from the CT for each phase to neutral to verify that the neutral leg of the circuit has not been accidentally left open.
16% - Trip check each relay for all phases and verify each expected output. Use schematic drawing as a reference to make sure all inputs/outputs are operating correctly.
Perform load test with system load to verify overall relay performance. Verify CT/PT ratios via the protection relay once energized.
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