nerc ba test questions with complete
solutions41
What is the purpose in accounting for Inadvertent Interchange among the Balancing
Authorities? - ANSWERS-To ensure that Balancing Authorities do not excessively depend on
other Balancing Authority Areas for meeting their demand or Interchange obligations.
In your Interconnection, a generator tripped that was large enough to reduce the frequency
from 60.00 Hz to 59.94 Hz. Your Balancing Authority's Frequency Bias is 200 MW/0.1 Hz. How
many MW would your system initially contribute to frequency support? - ANSWERS-120 MW -
[10*B*(Fa - Fs)]. If Frequency drops to 59.94 Hz then -(10 * -200 MW/0.1 Hz) * (59.94 Hz - 60.00
Hz) = -(- 2000 MW/Hz * -0.060 Hz) = -120 MW. To return ACE to zero, your Balancing Authority
A Balancing Authority has a Net Interchange Schedule of -250 MWs from 1200 to 1600 on a
summer day. The Net Interchange Actual for those same hours respectively were -230 MW, -275
MW, -250 MW and -270 MW. What was the Balancing Authority's Inadvertent Interchange for
the 4 hour period? - ANSWERS-Inadvertent for hour 1: (-230 ) - (-250) = +20
Inadvertent for hour 2: (-275) - (-250) = -25
Inadvertent for hour 3: (-250) - (-250) = 0
Inadvertent for hour 4: (-270) - (-250) = -20
Net for the period = - 25
A 700 MW generator in Balancing Authority A's area trips off line. Which control system on the
remaining generators would respond to the drop in system frequency resulting from the loss of
generation? - ANSWERS-Generator governor control systemsFrequency Response (Equipment)
is the ability of a system or elements of the system to react or respond to a change in system
frequency. (System) The sum of the change in demand, plus the change in generation, divided
by the change in frequency, expressed in megawatts per 0.1 Hertz (MW/0.1 Hz). The loss of
generation in an Interconnection results in a corresponding decrease in frequency. The first
control systems to respond to a frequency are generator governor control systems. Declining
,frequency will cause the governor controls to open valves to increase input to the prime mover,
increasing the torque angle and megawatt output of the generator.
The initial response to a frequency deviation is due to which of the following?
1.Load/frequency response
2.AGC
3.Governor action
4.Interchange schedules - ANSWERS-1 and 3
Load increases or decreases according to the increase or decrease in frequency. For every 1%
change in frequency, load will change approximately ______% in the same direction. -
ANSWERS-Load on the power system changes with frequency. For every 1% change in
frequency, load will change approximately 2% in the same direction. This load change is
primarily from induction motor load and not from resistive loads. -
NERC Frequency Response Characteristic Survey Training Document
NERC Standard BAL-003
A Balancing Authority can reduce its Inadvertent Interchange accumulation by unilateral
payback, but is limited in the amount by its ___________. - ANSWERS-Balancing Authority ACE
Limit (BAAL) Unilateral payback means that the Balancing Authority adjust their generation to
either over generate if the inadvertent is negative, or under generate if the inadvertent is
positive. Either way it has to be to a non-zero ACE and the amount is still under the guide lines
of the CPS compliance factors. This means that the payback is limited by the Balancing
Authorities ACE Limit or BAAL. For example, if the BA was paying back inadvertent unilaterally
and the BA's ACE ended up exceeding its BAAL due to a change in frequency (BAAL is based on
frequency), it would have to return its ACE to within BAAL within 30 minutes
If the frequency bias setting is set to a less negative value than the frequency response of a
Balancing Authority and a frequency increase is caused by a sudden loss of load in an external
,balancing area, what will the result be? - ANSWERS-The ACE will be a negative value and AGC
will increase generation
If a Balancing Authority needs to offset the scheduled frequency by 0.02 Hz, due to an
Interconnection wide time error correction, what adjustment can the Balancing Authority make
to participate Interconnection wide time error correction if unable to change scheduled
frequency?
A.Change the AGC mode
B.Changing the governor speed droop from 5% to 4%
Changing the B (frequency bias) setting of the ACE equation
Offset its net Interchange Schedule in megawatts by an amount equal to the computed bias
contribution during a 0.02 Hz Frequency Deviation - ANSWERS-Offset its net Interchange
Schedule in megawatts by an amount equal to the computed bias contribution during a 0.02 Hz
Frequency Deviation
Time Error Correction is when the Interconnection schedules frequency, normally 60.00 Hz to
59.98 Hz or 60.02 Hz in order to adjust clocks that may be either fast or slow due to the
frequency fluctuations of the power system. If the Balancing Authority can not change
scheduled frequency which would produce -10B(+/-0.02) value, they shall offset its Net
Interchange Schedule by an amount equal to 20% of it Frequency Bias [10B(0.02)]. NERC
Standard BAL-004 and Time Monitoring Reference Document, 2016
How is the Frequency Response Obligation (FRO) of a Frequency Response Sharing Group
determined? - ANSWERS-By adding the individual FRO's of each member.
A Balancing Authority was only 95% compliant with the DCS criteria for the first quarter of the
year. What action must the Balancing Authority take? - ANSWERS-Must carry additional
contingency reserve for 3 months starting May 1.
Inadvertent Interchange accumulations paid back by controlling to a target of non-zero ACE and
limited by the Balancing Authority's BAAL is known as, ___________. - ANSWERS-unilateral
payback
, Where should the synchronization of islands occur?
Remote Locations
Outside of BA
Control Room
Predefined locations - ANSWERS-Predefined locations When a restoration plan is first
developed, the plan's developers must determine where synchronizing equipment is located
within the power system and whether the equipment is at the correct locations. The most likely
place for restoration is at a substation equipped with the sync scope.
Why are high transmission system voltages a problem during system restoration? - ANSWERS-
Because of the excessive MVAR supply from energizing transmission lines.
Re-synchronization with the Interconnection should only be attempted at a - ANSWERS-
Substation with a synchroscope
If a Transmission Operator or Balancing Authority is unable to restore Real and Reactive Power
Balance, and corrective action or emergency assistance is not adequate, they shall: - ANSWERS-
Implement manual load shedding
A Balancing Authority is assessing its system by reviewing the frequency at locations in its area
and notices a frequency reading at one location varies significantly from the other locations.
What might the Balancing Authority conclude? - ANSWERS-An island condition has occurred
If multiple line trips resulting in parallel lines overloading and voltage to decrease, the system
operator should first consider which mitigating actions?
!1.Open the line breakers to the overloaded lines.
2.Shed load to reduce the powerflow on the overloaded lines
3.Re-dispatch or bring on additional generation
solutions41
What is the purpose in accounting for Inadvertent Interchange among the Balancing
Authorities? - ANSWERS-To ensure that Balancing Authorities do not excessively depend on
other Balancing Authority Areas for meeting their demand or Interchange obligations.
In your Interconnection, a generator tripped that was large enough to reduce the frequency
from 60.00 Hz to 59.94 Hz. Your Balancing Authority's Frequency Bias is 200 MW/0.1 Hz. How
many MW would your system initially contribute to frequency support? - ANSWERS-120 MW -
[10*B*(Fa - Fs)]. If Frequency drops to 59.94 Hz then -(10 * -200 MW/0.1 Hz) * (59.94 Hz - 60.00
Hz) = -(- 2000 MW/Hz * -0.060 Hz) = -120 MW. To return ACE to zero, your Balancing Authority
A Balancing Authority has a Net Interchange Schedule of -250 MWs from 1200 to 1600 on a
summer day. The Net Interchange Actual for those same hours respectively were -230 MW, -275
MW, -250 MW and -270 MW. What was the Balancing Authority's Inadvertent Interchange for
the 4 hour period? - ANSWERS-Inadvertent for hour 1: (-230 ) - (-250) = +20
Inadvertent for hour 2: (-275) - (-250) = -25
Inadvertent for hour 3: (-250) - (-250) = 0
Inadvertent for hour 4: (-270) - (-250) = -20
Net for the period = - 25
A 700 MW generator in Balancing Authority A's area trips off line. Which control system on the
remaining generators would respond to the drop in system frequency resulting from the loss of
generation? - ANSWERS-Generator governor control systemsFrequency Response (Equipment)
is the ability of a system or elements of the system to react or respond to a change in system
frequency. (System) The sum of the change in demand, plus the change in generation, divided
by the change in frequency, expressed in megawatts per 0.1 Hertz (MW/0.1 Hz). The loss of
generation in an Interconnection results in a corresponding decrease in frequency. The first
control systems to respond to a frequency are generator governor control systems. Declining
,frequency will cause the governor controls to open valves to increase input to the prime mover,
increasing the torque angle and megawatt output of the generator.
The initial response to a frequency deviation is due to which of the following?
1.Load/frequency response
2.AGC
3.Governor action
4.Interchange schedules - ANSWERS-1 and 3
Load increases or decreases according to the increase or decrease in frequency. For every 1%
change in frequency, load will change approximately ______% in the same direction. -
ANSWERS-Load on the power system changes with frequency. For every 1% change in
frequency, load will change approximately 2% in the same direction. This load change is
primarily from induction motor load and not from resistive loads. -
NERC Frequency Response Characteristic Survey Training Document
NERC Standard BAL-003
A Balancing Authority can reduce its Inadvertent Interchange accumulation by unilateral
payback, but is limited in the amount by its ___________. - ANSWERS-Balancing Authority ACE
Limit (BAAL) Unilateral payback means that the Balancing Authority adjust their generation to
either over generate if the inadvertent is negative, or under generate if the inadvertent is
positive. Either way it has to be to a non-zero ACE and the amount is still under the guide lines
of the CPS compliance factors. This means that the payback is limited by the Balancing
Authorities ACE Limit or BAAL. For example, if the BA was paying back inadvertent unilaterally
and the BA's ACE ended up exceeding its BAAL due to a change in frequency (BAAL is based on
frequency), it would have to return its ACE to within BAAL within 30 minutes
If the frequency bias setting is set to a less negative value than the frequency response of a
Balancing Authority and a frequency increase is caused by a sudden loss of load in an external
,balancing area, what will the result be? - ANSWERS-The ACE will be a negative value and AGC
will increase generation
If a Balancing Authority needs to offset the scheduled frequency by 0.02 Hz, due to an
Interconnection wide time error correction, what adjustment can the Balancing Authority make
to participate Interconnection wide time error correction if unable to change scheduled
frequency?
A.Change the AGC mode
B.Changing the governor speed droop from 5% to 4%
Changing the B (frequency bias) setting of the ACE equation
Offset its net Interchange Schedule in megawatts by an amount equal to the computed bias
contribution during a 0.02 Hz Frequency Deviation - ANSWERS-Offset its net Interchange
Schedule in megawatts by an amount equal to the computed bias contribution during a 0.02 Hz
Frequency Deviation
Time Error Correction is when the Interconnection schedules frequency, normally 60.00 Hz to
59.98 Hz or 60.02 Hz in order to adjust clocks that may be either fast or slow due to the
frequency fluctuations of the power system. If the Balancing Authority can not change
scheduled frequency which would produce -10B(+/-0.02) value, they shall offset its Net
Interchange Schedule by an amount equal to 20% of it Frequency Bias [10B(0.02)]. NERC
Standard BAL-004 and Time Monitoring Reference Document, 2016
How is the Frequency Response Obligation (FRO) of a Frequency Response Sharing Group
determined? - ANSWERS-By adding the individual FRO's of each member.
A Balancing Authority was only 95% compliant with the DCS criteria for the first quarter of the
year. What action must the Balancing Authority take? - ANSWERS-Must carry additional
contingency reserve for 3 months starting May 1.
Inadvertent Interchange accumulations paid back by controlling to a target of non-zero ACE and
limited by the Balancing Authority's BAAL is known as, ___________. - ANSWERS-unilateral
payback
, Where should the synchronization of islands occur?
Remote Locations
Outside of BA
Control Room
Predefined locations - ANSWERS-Predefined locations When a restoration plan is first
developed, the plan's developers must determine where synchronizing equipment is located
within the power system and whether the equipment is at the correct locations. The most likely
place for restoration is at a substation equipped with the sync scope.
Why are high transmission system voltages a problem during system restoration? - ANSWERS-
Because of the excessive MVAR supply from energizing transmission lines.
Re-synchronization with the Interconnection should only be attempted at a - ANSWERS-
Substation with a synchroscope
If a Transmission Operator or Balancing Authority is unable to restore Real and Reactive Power
Balance, and corrective action or emergency assistance is not adequate, they shall: - ANSWERS-
Implement manual load shedding
A Balancing Authority is assessing its system by reviewing the frequency at locations in its area
and notices a frequency reading at one location varies significantly from the other locations.
What might the Balancing Authority conclude? - ANSWERS-An island condition has occurred
If multiple line trips resulting in parallel lines overloading and voltage to decrease, the system
operator should first consider which mitigating actions?
!1.Open the line breakers to the overloaded lines.
2.Shed load to reduce the powerflow on the overloaded lines
3.Re-dispatch or bring on additional generation
