Primary Interest Groups
Generator Owners (GOs)
Generator Operators (GOPs)
Transmission Operators (TOPs)
Transmission Owners (TOs)
Problem Statement
During a recent event, problems were encountered regarding redundant relays associated with a remedial action scheme (RAS), where two redundant RAS input/output (I/O) devices failed due to a firmware
RAM/ROM processor error. The device failure alarms went undetected because of an error on the wiring diagram that prevented the positive dc from being connected properly, thus disabling the signaling of the
I/O device’s alarm status. While the schematic (or elementary diagram) correctly showed the proper I/O device alarm circuit design and connections, the wiring diagram of the RAS panel did not match the schematic.
Details
During the event investigation, the commissioning records showed that the RAS alarms had been checked between the local station and the remote operation center. However, the process used to test the alarms during the initial commissioning could not be determined. It is assumed that the alarms were simulated using remote confirmation, but were not checked using a proper method.
Corrective Actions

The wiring design error was corrected on the prints, and the alarm positive DC was rewired to match the correct connection shown on the schematic.


Alarms were operationally checked and proven on relays after rewiring.

The field technical support organization conducted a webinar for all field relay technicians. The webinar covered and reinforced all aspects of print review, alarm verification, and checkout processes. Emphasis was placed upon the importance of verifying and comparing prints, proving circuit operations, and verifying alarm points for the entire circuit back to existing circuit connections, including all AC and DC controls. In order to detect alarm design errors, future commissioning documents will require a signoff for each individual alarm.
Lessons Learned
 Detailed checkout and commissioning processes must be in place to catch wiring errors or print discrepancies. These processes must be periodically reinforced in technical meetings or retraining sessions.
 Alarm simulation should include all terminal connections and interconnected wiring.
 Status indications and alarms should be verified by actuating device outputs (preferably by creating the initiating condition) while monitoring for expected status indication and alarms both at the local station and the remote operation center. If unable to fully simulate the alarm condition, initiating the device output is necessary to ensure there are no output wiring polarity issues.

Design processes should include peer review.

Expansion, modification, or both of good utility practices must be continually undertaken with a strong emphasis on human performance.

Installation and commissioning processes need to be constantly reviewed and reinforced, and checks and tests continually identified and addressed.
Lesson Learned – Detailed Installation and Commissioning Testing to Identify Wiring or Design Errors 2

 Standardized RAS checkout procedures are a must. Specific requirements should be included in RAS checkout procedures to ensure consistent alarm checkout, utilizing formal individual alarm signoffs at both the local station and the remote operation center via SCADA.
 This is an excellent example of why relay health status alarms should be properly connected to provide remote alarm indications.
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Source of Lesson Learned:
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SERC Reliability Corporation
Lesson Learned #:
Date Published:
20150401
April 21, 2015
Category: Relaying and Protection Systems
This document is designed to convey lessons learned from NERC’s various activities. It is not intended to establish new requirements under NERC’s
Reliability Standards or to modify the requirements in any existing Reliability Standards. Compliance will continue to be determined based on language in the NERC Reliability Standards as they may be amended from time to time. Implementation of this lesson learned is not a substitute for compliance with requirements in NERC’s Reliability Standards.
Lesson Learned – Detailed Installation and Commissioning Testing to Identify Wiring or Design Errors 3