Power System Operations Flashcards
7 cards from real SOPD practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Power System Operations flashcards as text
During a system restoration after a blackout, why must operators be careful about 'cold load pickup'?
Answer: De-energized loads lose diversity and simultaneously draw maximum demand when restored, causing overloads
Cold load pickup occurs because thermostatically controlled loads all start simultaneously after a prolonged outage, producing current levels far above normal.
What is the role of the 'black start' unit in power system restoration?
Answer: A generator capable of starting and supplying initial energization without an external power source
Black start units (hydro, gas turbines, or diesel units) can start independently and energize the grid from scratch after a total blackout.
What is 'transient stability' in power system operations?
Answer: The ability of the system to maintain synchronism following a large sudden disturbance
Transient stability refers to whether synchronous generators remain in synchronism with each other following severe disturbances such as faults.
A dispatcher receives a SCADA alarm showing a breaker is in 'split position.' What does this status most likely indicate?
Answer: The breaker mechanism has failed and neither the open nor closed state is confirmed
A split or undefined position alarm indicates a discrepancy between the breaker's open and closed contacts, suggesting a partial or failed operation.
What is the purpose of a 'transfer trip' scheme in transmission line protection?
Answer: To send a communication signal to trip the remote end breaker when a local relay detects a fault
Transfer trip uses a communication channel (fiber, PLC, or radio) to command the remote breaker to open when the local end detects a line fault, enabling high-speed clearing.
An operator notices that a 345 kV bus voltage has risen to 105% of nominal during light load conditions at night. What is the most likely cause?
Answer: Ferranti effect and capacitive charging of lightly loaded long transmission lines
The Ferranti effect causes receiving-end voltage to rise above sending-end voltage on lightly loaded or open-circuited long lines due to line charging capacitance.
Under NERC standards, what is the maximum allowable time for a balancing authority to return ACE to zero after a disturbance under CPS2?
Answer: 10 minutes
CPS2 requires that the 10-minute average of ACE be within a defined bound (L10), effectively requiring recovery within a 10-minute window.