EAS Lessons Learned Summary Lessons Learned Published in June
2014 Slide 2 RELIABILITY | ACCOUNTABILITY2 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 June 2014 Lessons Learned Slide 3
RELIABILITY | ACCOUNTABILITY3 New microprocessor relay added to
generators 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 - Overexcitation Slide 4 RELIABILITY |
ACCOUNTABILITY4 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 Slide 5 RELIABILITY | ACCOUNTABILITY5
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 Slide 6 RELIABILITY | ACCOUNTABILITY6 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 Slide 7 RELIABILITY | ACCOUNTABILITY7
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)www.NERC.com NERCs 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. Slide 8 RELIABILITY |
ACCOUNTABILITY8 For more information please email:
[email protected] Questions
