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NERC BI - System Operations Questions and Answers Graded A+
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NERC BI - System Operations
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NERC BI - System OperationsDisturbance - answerAny perturbation to the electric system or the unexpected change
in ACE that is caused by the sudden loss of generation or interruption of load
Interconnection reliability operating limit ( IROL) - answer The value (such as MW,
MVar, Amperes, Frequency or Volts) derived from, or a subset of the System Operating
Limits, which if exceeded, could expose a widespread area of the Bulk Electric System
to instability, uncontrolled separation(s) or cascading outages.
Interconnection reliability operating limit – answer A System Operating Limit that, if
violated, could lead to instability, uncontrolled separation, or Cascading outages4 that
adversely impact the reliability of the Bulk Electric System.
Impedance - answer The AC version of resistance to power flow, it includes inductive
and capacitive reactance ( note when lines run in parallel it lowers the path of
impedance)
Phase Angle - answer
Power Angle - answer
Voltage - answeran electromotive force or potential difference expressed in volts.
System Operating limit - answerThe value (such as MW, MVar, Amperes, Frequency or
Volts) that satisfies the most limiting of the prescribed operating criteria for a specified
system configuration to ensure operation within acceptable reliability criteria. System
Operating Limits are based upon certain operating criteria. These include, but are not
limited to:
Facility Ratings (Applicable pre- and post-Contingency equipment or facility ratings)
Transient Stability Ratings (Applicable pre- and post-Contingency Stability Limits)
Voltage Stability Ratings (Applicable pre- and post-Contingency Voltage Stability)
System Voltage Limits (Applicable pre- and post-Contingency Voltage Limits)
What is the maximum power angle degree in the power transfer equation? Greater than
this will cause system instability. - answer90 Degrees
What three elements make up impedance in an alternating current power system -
answerCapacitance inductance and resistance
Which elements make up power - answercurrent impedance and voltage
, Steady state stability - answerwhen the system parameters monitored by the reliability
coordinators, transmission operators and balancing authorities such as voltages,
frequency and power flows may be changing but the changes are small and occur
gradually
Transient stability - answerTransient stability describes the ability of the power system
where a sudden large change takes place within the system without violating system
operating limits. This could be the loss of a major generator or a severe system fault
Generators as the source of real and reactive power are the stabilizing force in the
power system
Power angle across a section of the system is ... - answer20 degrees
What happens if a transmission line outage occurs - answerMW flows increase on the
existing transmission lines still in service
As Amps increase MVAR losses as a result of existing inductive reactance -
answerIncreases
Transient instability - answerpower angle greater than 90 degrees from power transfer,
when a disturbance causes power angle greater than 90 degrees or when heavy power
transfers to one or more transmission segments such as a loss in generation
Reliability coordinator, transmission operator and balancing authority can manage
outages effectively by - answer- Coordinate and adhere to voltage schedules to
minimize reactive power flow and to minimize system transfers that require additional
VAR reserves
- Verify generator, synchronous condenser, SVC or other voltage control equipment
voltage regulators are on automatic for dynamic reactive power supply to support
voltage
- Optimize the use of load tap change (LTC) transformers, capacitor banks and reactor
(inductor) banks are due to the time lag involved in controlling these devices
Real power MW will flow on the transmission system as a result of power angle
differences. What direction will real power flow? - answerHigher power angle to lower
power angle
True or False - System stability is when there are few changes in the power system and
in the event of a disturbance the system will successfully absorb the impact and
continue within its system operating limits - answerTrue
System operators monitor real time power system data. They must be prepared and
take action to ensure equipment is operated within? - answerSystem Operating limits
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