SOPD Emergency Response & System Restoration Procedures 4 — Questions and Answers
Question 1: What does 'load shedding' accomplish during a generation deficiency emergency?
- It increases generator output by reducing system impedance
- It reduces system demand to balance generation and arrest frequency decline (Correct answer)
- It transfers load to neighboring control areas automatically
- It activates demand response programs for economic savings only
Correct answer: It reduces system demand to balance generation and arrest frequency decline
Load shedding reduces total system demand to match available generation, stabilizing frequency and preventing a complete system collapse.
Question 2: A 'sectionalizing' switch used during emergency restoration is operated to:
- Increase the short-circuit rating of the bus
- Isolate a faulted section and restore supply to unfaulted portions of the feeder (Correct answer)
- Trip a transmission line on over-current
- Lock out a breaker after a fault until relay engineers approve re-closing
Correct answer: Isolate a faulted section and restore supply to unfaulted portions of the feeder
Sectionalizing switches allow operators to isolate the faulted segment of a circuit and then re-energize the healthy sections from alternate supply points.
Question 3: NERC EOP-006 addresses:
- Frequency response obligations for Balancing Authorities
- Restoration coordination between Transmission Operators and Balancing Authorities (Correct answer)
- Protection system misoperation reporting requirements
- Reactive power planning for transmission systems
Correct answer: Restoration coordination between Transmission Operators and Balancing Authorities
EOP-006 defines the roles and coordination requirements between Transmission Operators and Balancing Authorities during system restoration activities.
Question 4: During high system stress, a Transmission Operator observes voltage collapse beginning in one area. The most effective short-term corrective action is:
- Open all inter-area tie lines to contain the collapse
- Rapidly increase reactive support (generators, SVCs, capacitors) in the affected area and reduce reactive-consuming load (Correct answer)
- Reduce generation output in the affected area to lower line loading
- Issue a conservative operations advisory and wait for market response
Correct answer: Rapidly increase reactive support (generators, SVCs, capacitors) in the affected area and reduce reactive-consuming load
Voltage collapse is driven by reactive power deficit; immediate injection of reactive support arrests the collapse before it propagates.
Question 5: A 'generation trip' event causing sudden loss of 1,200 MW will cause system frequency to:
- Rise sharply as remaining generators accelerate to fill the gap
- Drop immediately as the generation-load balance is upset (Correct answer)
- Remain stable if spinning reserves are adequate
- Oscillate between 59.8 Hz and 60.2 Hz before stabilizing
Correct answer: Drop immediately as the generation-load balance is upset
Loss of generation causes an immediate frequency drop as the remaining inertia decelerates trying to supply the unchanged load.
Question 6: Which document defines the specific cranking path and load pickup steps a Balancing Authority must follow during system restoration?
- Transmission Planning Study report
- System Restoration Plan (SRP) required by EOP-005 (Correct answer)
- Energy Management System (EMS) topology processor output
- Annual load forecast report
Correct answer: System Restoration Plan (SRP) required by EOP-005
NERC EOP-005 requires each Transmission Operator and Balancing Authority to maintain a documented System Restoration Plan detailing cranking paths, black start resources, and load pickup sequences.
Question 7: What is the primary hazard of energizing a long unloaded EHV transmission line during restoration?
- Excessive real power loss due to low current
- Ferranti effect causing receiving-end voltage to rise dangerously above sending-end voltage (Correct answer)
- Increased short-circuit current at the substation bus
- Automatic under-voltage load shedding at the remote end
Correct answer: Ferranti effect causing receiving-end voltage to rise dangerously above sending-end voltage
The Ferranti effect occurs on long lightly-loaded lines where the distributed capacitance charges from the source and can raise remote-end voltage significantly above the sending-end voltage.
SOPD Emergency Response & System Restoration Procedures 4
What does 'load shedding' accomplish during a generation deficiency emergency?