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NERC System Operator Exam Preparation (SOS/HSI) | Actual
Answers Latest Updated 2025 /202 6 (Graded A+)
Power equation - ✔✔P=IV; power (watts)=current (amps) x voltage (volts) Power equation three phase - ✔✔Power=Voltage (v) x Current (I) x 1.73 x Power Factor (PF) If operating reserve gradually decreases throughout the hour, it's because. - ✔✔Incorrect load forecast Operating reserves are made up of and. - ✔✔Regulating Reserves and Contingency Reserve What type of reserves are used for AGC? - ✔✔Regulating A BA's MSSC is usually its. - ✔✔Largest Generator Equation to determine speed in RPM of a Generator? - ✔✔7200/# of poles At what frequency will a generator trip on underfrequency? - ✔✔57.5 Hz Why do we have underfrequency tripping? - ✔✔Protect turbines from damage Why does frequency drop faster/is harder to correct, when we have a disturbance when we have increased wind generation? - ✔✔Less inertia/governor response to correct frequency Frequency above 60 Hz means. - ✔✔Overgenerating Frequency below 60 Hz means. - ✔✔Undergenerating
Questions and
Frequency decrease is usually caused by. - ✔✔Loss of generation A 1% drop in frequency results in. - ✔✔2% drop in total load; 3% drop in motor load Formula for ACE? - ✔✔NIa-NIs - 10B(Fa-Fs) Governor response is based on its characteristic. - ✔✔Droop 5% of 60 Hz= - ✔✔ 3 Hz; most Governor's have 5% droop characteristic Droop setting is the % required for a generator to run at capacity. - ✔✔Full What is the purpose of a governor deadband? - ✔✔Minimize wear on equipment What % for governor deadband? - ✔✔+/- .036 Hz An isochrynous generator setting has droop. - ✔✔0% When are isochryonous generators used? - ✔✔one unit, during islanding Is 10% droop or 5% droop more responsive? - ✔✔5% On a classic disturbance chart, what brings frequency from point c to d? - ✔✔Contingency Reserve On a classic disturbance chart, what causes a 'step' change? - ✔✔Fast-start generator What's the primary response to frequency drop? - ✔✔Governor response
BA has to recover its ACE back to ____f it was positive or zero before a disturbance. - ✔✔ 0 BA has to recover its ACE back to if it was negative before a disturbance. - ✔✔pre-disturbance value BAL- 003 says each BA shall implement settings. - ✔✔Frequency Bias If B=frequency response, ACE is--------- ✔✔unchanged If B is more negative than actual frequency response, ACE is and units on AGC will. - ✔✔negative; increase output If B is less negative than actual frequency response, ACE is and units on AGC will--------- ✔✔positive; hurt frequency BAL- 005 says BA has to scan ACE every -------- ✔✔six seconds BAs must notify RC if unable to calculate ACE for more than --------- ✔✔ 30 minutes helps maintain ACE by adjusting resources. - ✔✔AGC (Automatic Generation Control) AGC should always operate in what mode? - ✔✔Tie-Line Bias What AGC mode should be used when restoring an island? - ✔✔Flat frequency To fix a fast time error, Frequency should be set to ___. - ✔✔59. To fix a slow time error, Frequency should be set to. - ✔✔60.
Formula to calculate Inadvertent Interchange? - ✔✔NIa-Nis INT-006 says has to be assessed for reliability before implementation. - ✔✔Interchange Source or Sink BA must interchange if it does not expect to be capable of supporting the magnitude, ramping, or scheduling path. - ✔✔Deny Only and can approve Interchange Tags. - ✔✔BAs and TSPs When are Interchange transactions implemented? - ✔✔When entered into the ACE equation Who confirms Tags? - ✔✔Sink BA What part of ACE do Dynamic Schedules impact? - ✔✔NIs What part of ACE do Psuedo Ties impact? - ✔✔NIa Dynamic transfers are used for. - ✔✔JOGs (jointly owned generators) Indication of loss of load could be caused by error. - ✔✔Generator/Meter When you lose a block of load, NIa and ACE. - ✔✔increases; increases When you lose a generator, NIa and ACE. - ✔✔decreases; decreases Formula for system load? - ✔✔Total generation - Net actual interchange When a generator is lost outside of your BA, ACE and frequency. - ✔✔stays the same; drops
provide reactive power close to where it is needed. - ✔✔Shunt Capacitors absorb excess VARs. - ✔✔Shunt Reactors Generator is underexcited and leading when it is MVARs. - ✔✔Absorbing Generator is overexcited and lagging when it is MVARs. - ✔✔Delivering/adding During restoration, you want your generator to be leading or lagging? - ✔✔Leading Generator capability limit is based on limits. - ✔✔Thermal produce only reactive power (when generator is in condenser mode); Basically, a generator without a prime mover. - ✔✔Synchronous Condensers is a capacitor and a reactor combo that provides dynamic reactive resources. - ✔✔SVC (Static Var Compensator) What device moves MVARs by changing the ratio of windings? - ✔✔Under Load Tap Changer are not reactive resources; they effectively lengthen or shorten the transmission line. - ✔✔Series capacitors and Series reactors Where are shunt capacitors placed? - ✔✔Close to inductive load To get ahead of voltage, system operators should do what? - ✔✔Put capacitors into service prior to peak
Formula for MVAR output? - ✔✔MVAR output=MVAR rated x (Voltage Actual/Voltage Rated)² Shunt Reactors are located near. - ✔✔High voltage stations What is used to reduce voltage by absorbing MVARs? - ✔✔Shunt Reactors What is used to increase voltage by adding MVARs? - ✔✔Shunt Capacitors VAR: 002 says GOPs shall operate Generator in mode. - ✔✔AVR (Automatic Voltage Regulator) If a GOP can't operate in AVR mode, they must notify within. - ✔✔TOP; 30 minutes VAR: 001 says must maintain voltage and reactive control. - ✔✔TOP MVAR flow from to voltage. - ✔✔High to low Real power flows from to power angle. - ✔✔Higher to lower Phase Shifting Transformers (PSTs) allow us to change by changing the power angle. - ✔✔Real power flow Formula for Power Losses - ✔✔PL=I²R What happens to power losses when current doubles? - ✔✔Quadruples is when MVAR supplied = MVAR absorbed. - ✔✔SIL (Surge Impedence Loading) P-V curve is used to determine what? - ✔✔Point of system instability because of voltage collapse
What relay usually clears a line-to-ground fault? - ✔✔50 Instantaneous Overcurrent or 51 Timed Overcurrent What relay usually clears a line-to-line fault? - ✔✔ 21 Distance Relay A difference of current in and current out will initiate a relay. - ✔✔ 87 Differential PTs provide indication. - ✔✔voltage CTs provide indication. - ✔✔current Formula for Ohm's Law - ✔✔V=I x R (voltage (volts)=current (amps) x Resistance (Ohms) What relay senses a line's impedance by sensing current and voltage from CTs and PTs? - ✔✔ 21 - Distance Relay Zones of Protection for Distance Relay--What % for Zone 1, 2, 3? - ✔✔90%, 120%, 200% Sync-check relay automatically closes when phase angle is within. - ✔✔ 30 degrees What detects predetermined system conditions and takes automatic corrective actions to ensure reliability? - ✔✔RAS (Remedial Action Scheme) What can be done to prevent system protection failures? - ✔✔Redundancy, backup protection, overlapping zones, breaker failure protection Lightly loaded transmission lines are. - ✔✔Capacitive/supply MVAR Heavily loaded transmission lines are. - ✔✔Inductive/absorb MVAR
COM- 001 says System Operators must test their alternative communication capability how often? - ✔✔once per calendar month If alternative communications capability test is unsuccessful, how long to repair or replace? - ✔✔ 2 hours When there is a failure with primary communication that lasts 30+ minutes, must notify affected entities within. - ✔✔60 minutes COM- 002 says all Operating Instructions must. - ✔✔follow documented protocols How often must Comm Protocols be assessed? - ✔✔Once every 12 months A command by operating personnel for real time ops? - ✔✔Operating Instruction What is an RTU? - ✔✔Remote Terminal Unit; found in field substations; 2 - way communication device from control room to field Supervisory Control and Data Acquisition - ✔✔SCADA Inter-control Center Communication Protocol - ✔✔ICCP Reliability Coordinator Information System - ✔✔RCIS If you are the RC and ICCP goes down, what do you do? - ✔✔Implement Backup functionality plan Where do RCs post messages and share operating info occurring in real time? - ✔✔RCIS
SOL are determined by the most limit. - ✔✔Restrictive is an SOL that could cause instability, cascading, etc. - ✔✔IROL What is the maximum time an IROL can be violated? - ✔✔Tv (30 minutes max) Contingency Analysis tools include: - ✔✔State Estimator, CA, CM What tool simulates power flow for a set of contingencies? - ✔✔Contingency Analysis What tool is used by RCs to determine contribution to flowgate loading? - ✔✔Congestion Management What is the IDC (interchange distribution calculator) used for? - ✔✔Congestion Management One must comply with Operating Instructions unless. - ✔✔It would violate safety, equipment, or Regulatory/Statutory regulations Shift factor that tells % change in loading due to power transfer (interchange)? - ✔✔PTDF Shift factor that tells % a change in generator will impact a transmission facility. - ✔✔GSF What formula is used to determine relief on a line? - ✔✔Overload/Distribution Factor A positive GSF means generation. - ✔✔decrease A negative GSF means generation. - ✔✔increase
With 2 positive GSFs, always the generator with the lower shift factor and the generator with the higher shift factor. - ✔✔increase; decrease Who issues TLRs (Transmission Loading Relief)? - ✔✔RC RC has to perform real time assessment how often? - ✔✔every 30 minutes Who has to develop operating plans for emergencies? - ✔✔BA and TOP Who must coordinate actions during an emergency? - ✔✔RC Who must be notified by TOP in an emergency? - ✔✔RC, impacted TOPs and BAs Who deals with capacity and energy emergencies? - ✔✔BA In extreme cold weather, the RC would be concerned about. - ✔✔fuel shortages (natural gas) What level EEA? All available resources are in use. - ✔✔EEA 1 What level EEA? Load management procedures are in effect. - ✔✔EEA 2 What level EEA? Firm load interruption is immiment/in progress - ✔✔EEA 3 Who issues EEAs? - ✔✔RC How long do RCs have to notify other BAs and TOPs (as well as neighboring RCs) of an emergency request notification? - ✔✔30 minutes During EEA 2, the BA can still meet its requirements. - ✔✔Contingency Reserve
What are the three Rs of Emergency Response? - ✔✔Redispatch, Reconfigure, Reduce Generator that can start without system support? - ✔✔Blackstart, usually CT or hydro What are cranking paths? - ✔✔Paths used to start up other generating units during restoration First priority in restoration is to restore power where? - ✔✔Off-site nuclear/critical facilities What kind of lines make the best cranking paths? - ✔✔Shorter lines, overhead What is an increase in load magnitude when a feeder is re-energized following an outage period? - ✔✔Cold load pickup Instantaneous electric current drawn by a motor in the fractions of a second after a motor turns on? - ✔✔Motor in-rush current (10x normal) What are the primary causes of cold load pickup? - ✔✔Motor in-rush current and Load Diversity Anything with a thermostat or load cycles creates. - ✔✔Load diversity What are the two strategies for restoration? - ✔✔Open all breakers, Controlled Breaker Biggest disadvantage of opening all breakers during restoration? - ✔✔Limited battery resources could be depleted will be more erratic during restoration. - ✔✔Frequency (maintain 59.75- 61 Hz) Shed % of load in order to raise frequency by 1 Hz. - ✔✔ 6 - 10%
Load blocks should be restored in increments of % of total connected load. - ✔✔5% Who has to have Restoration Coordination plans? - ✔✔RCs EOP-005 says must have Restoration Plans. - ✔✔TOPs Who has to review the TOPs' Restoration plans? - ✔✔RC TOPs must verify their restoration plans every through simulation. - ✔✔ 5 years How often must Blackstart units be tested? - ✔✔every 3 years What is the voltage range during restoration? - ✔✔± 10% of nominal How often must TOPs evaluate their Restoration Plans? - ✔✔annually TOPs must provide field switching personnel with ___ system restoration training each year. - ✔✔ 2 hours EOP-006 says RCs must conduct restoration drills per year? - ✔✔ 2 RCs are responsible for during restoration. - ✔✔Coordination When does an RC's Restoration Coordination plan start and end? - ✔✔When blackstart units are used until all TOPs are interconnected and its RC area is connected to neighboring RC areas A 5% decrease in voltage results in % decrease in load. - ✔✔3%
