EAS Lessons Learned Summary Lessons Learned Published in June 2014

June 2014 Lessons Learned Three NERC lessons learned (LL) were published in June 2014 LL20140601 - Generation Relaying - Underfrequency Protection Coordination LL20140602 - Generation Relaying - Overexcitation LL20140603 - Verify That Actions Called for in Operating Guides Can Be Implemented Within Required Time Frames LL20140604 - Loss of SCADA Due to Memory Resources Being Fully Utilized

Generation Relaying - Overexcitation New microprocessor relay added to generator’s protection system. Included Volts/HZ function to protect for overexcitation Engineer duplicated existing Volts/HZ setting in new relay Existing Volts/HZ relay was a definite time characteristic and the new relay Volts/HZ element was an inverse time characteristic **Settings needed to be different During testing the unit tripped on Volts/HZ before the units overexcitation limiter actuated and below actual capability of unit LL: Do not assume new elements can be set with the same settings as the existing relays LL: When setting overexcitation elements, trip function needs to be coordinated with units excitation limiter

Generation Relaying – Auxiliary Equipment Underfrequency Protection Coordination Unit auxiliary (aux) equipment protection contained underfrequency tripping This underfrequency protection tripped the aux equipment during a system disturbance The aux equipment tripping resulted in the generator tripping (due to loss of boiler / turbine) It was determined that the aux equipment underfrequency protection was not needed and was disabled LL: Critical plant aux equipment protection should be reviewed to ensure it does not unnecessarily cause a generator trip during system disturbances

Included the TOP turning off auto reclosing on circuit breaker Verify Actions in Operating Guides Can Be Implemented Within Required Time Frames Operating Guides contained time requirements that did not consider the ability of Operating Personnel to complete task Required that actions be taken within 30 minutes to protect local generation Included the TOP turning off auto reclosing on circuit breaker Required dispatching personnel to the substation TOP was informed TO personnel would take longer than 30 minutes to reach the substation LL: Review procedures to verify documented actions can be accomplished within the specified time LL: When developing operating plans (etc.), must consider real- time requirements and involve all stakeholders or parties that have actions in the plans

Loss of SCADA Due to Memory Resources Being Fully Utilized Loss of EMS due to memory resources (MR) on primary server being overworked by SSH sessions from another SCADA host SSH session repeatedly initiated commands Discrepancy in EMS file host-naming convention caused the MR to exceed maximum capacity Some protocols used in communication front-end processors did not support the Network Address Translation used in failover Host names on the host file were corrected and tested. Configuration settings modified - front-end processor at backup used in the event the primary fails LL: SCADA host resources to include monitoring and alarming of crucial events and server resources for SA Secure Shell (SSH) memory resources (MR)

Links to Lessons Learned Link to Lessons Learned Directions to Lessons Learned: Go to www.NERC.com > “Program Areas & Departments” tab > “Reliability Risk Management” (left side menu) > “Event Analysis” (left side menu) > “Lessons Learned” (left side menu) 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.

Questions For more information please email: Nerc.LessonsLearned@nerc.net