1. NERC Published Lessons Learned Summary
June 07, 2016

2. NERC Lessons Learned Published in May and June 2016
Two (2) NERC Lessons Learned (LL) were published in the 2nd quarter of 2016
LL “Control Center Loss of SCADA Control and Monitoring Capability”
LL “Transmission Relaying – Relay Setting Issue”

3. Control Center Loss of SCADA Control and Monitoring Capability – Detail
Transmission Operators (TOPs) adding a new group-control command function to operate multiple breakers at once
Initial testing with five breakers was successful
While executing the group-control command for nearly 300 other breakers, SCADA generated “CTRL ISSUED” alarms with invalid key information that resulted in SCADA aborting unexpectedly and restarting
The restart failed again because the unacknowledged alarm was downloaded as part of the initialization process

4. Control Center Loss of SCADA Control and Monitoring Capability – Corrective Actions
The vendor delivered a patch to address both the generation of invalid keys due to not checking against the maximum and the ability of SCADA to check for and ignore invalid key data
Patch was installed and successfully verified on the test system and then loaded onto the production system and the EMS SCADA group-control command was exercised appropriately
Vendor issued a Technical Flash-PTF and posted the patch for all customers

5. Control Center Loss of SCADA Control and Monitoring Capability – Lessons
Although the test system cannot truly verify that controls are sent to the RTUs, testing can be performed to show that applications on the EMS system do not fail
Future testing of SCADA controls will provide any additional reviews deemed necessary to accommodate the scale of the required task
When implementing new functions, the scale of operations to be performed should be considered and not just the operation itself
Testing of new functions at the scale they will be used can preview potential issues

6. Transmission Relaying – Relay Setting Issue – Details
The 230 kV line protection relays are connected on the 115kV side of a 230/115kV autotransformer and the 230/115kV transformer is in the 230 kV line protection zone
The 115kV bus is a breaker and half arrangement which connects to three 115kV lines in addition to the autotransformer
The 230 kV line relay operated on instantaneous ground directional (forward) overcurrent for a reverse fault (outside of the relays intended zone of protection)
The relay misoperation resulted in the tripping of the two associated 115kV low side transformer breakers and the transfer tripping of the two remote terminal breakers of the 230kV line
The 230/115kV transformer was a source of ground current for the fault

7. Transmission Relaying – Relay Setting Issue – Details
The relay has a setting option to use the manufacturer’s algorithm which automatically calculates values to determine the direction of faults
It has been the entities’ practice to employ this automatic calculation for determining the direction of faults
The relay manufacturer was contacted and after studying the event, determined the reason the relay’s z0 (zero-sequence directional) element declared this fault forward (incorrectly)

8. Transmission Relaying – Relay Setting Issue – Corrective Actions
The entity worked with the relay manufacturer to ensure the relay settings were corrected for this and similar applications
Relevant settings basis templates were also revised
Settings changes were shared with Protection and Controls Engineering staff and provided to its Engineering Vendors
The relay manufacturer plans to clarify this relay setting approach in the future by including an additional setting option related to the directional elements
The relay manufacturer will be recommending the new settings to customers when they communicate with them verbally or electronically
The manufacturer has committed to including these recommendations in a technical papers whenever possible

9. Transmission Relaying – Relay Setting Issue – Lessons
Must understand the operation of manufacturer recommendations, automatic settings and algorithms before applying them
Refer to the Fundamentals and Improvements for Directional Relays technical paper for more details and guidance

10. Lessons Learned Survey Link
NERC’s goal with publishing lessons learned is to provide industry with technical and understandable information that assists them with maintaining the reliability of the bulk power system.
NERC requests that industry provide input on lessons learned by taking the short survey. A link is provided in the PDF version of each Lesson Learned.