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NERC EXAM, TEST, PRACTICE EXAM AND STUDY GUIDE LATEST ACTUAL EXAM
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NERC EXAM, TEST, PRACTICE EXAM AND STUDY GUIDELATEST ACTUAL EXAM
Of the following, which control system would be affected by a difference in Net
Actual Interchange and Net Scheduled Interchange?
a. Automatic Voltage Regulator
b. Reactive Control
c. Automatic Generation Control
d. Turbine Governor Control - ANSWER: c. Automatic Generation Control
Feedback: BAL-005, Automatic Generation Control (AGC) Equipment automatically
adjusts generation in a Balancing Authority Area from a central location to maintain
the Balancing Authority's interchange schedule plus Frequency Bias. AGC is a process
designed and used to adjust a Balancing Authority Areas' Demand and resources to
help maintain the Reporting ACE in that of a Balancing Authority Area within the
bounds required by applicable NERC Reliability Standards. Governors arrest
frequency deviations, but Automatic Generation Control (AGC) maintains generation
to a schedule. It does this by pulsing the generator governors to either increase or
decrease megawatt as needed.
How is the Frequency Response Obligation (FRO) of a Frequency Response Sharing
Group determined?
a. By averaging the members' FRO's.
b. By adding the individual FRO's of each member.
c. By taking the median Frequency Response Measure of the previous year.
d. By adding the member's Frequency Response Measures of the previous year. -
ANSWER: b. By adding the individual FRO's of each member.
Feedback:
NERC allows Balancing Authorities to form Frequency Response Sharing Groups
(FRSGs) with other Balancing Authorities to jointly meet their FROs. These FRSGs
determine their joint FRO by adding up the member's individual FROs.
NERC Standard BAL-001 states that a Balancing Authority's clock-minute average of
Reporting ACE reading must not exceed its Balancing Authority ACE Limit (BAAL) for
more than __________.
a. 30 consecutive clock-minutes
b. 30 clock minutes per hour
c. 15 consecutive clock-minutes
d. 90% of 10-minute periods in a month - ANSWER: a. 30 consecutive clock-minutes
Feedback: BAL-001, Real Power Balancing Control Performance
,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 B (frequency bias) setting of the ACE equation
c. Changing the governor speed droop from 5% to 4%
d. Offset its Net Interchange Schedule(MW) by an amount equal to the computed
bias contribution during a 0.02 Hz Frequency Deviation - ANSWER: d. Offset its Net
Interchange Schedule(MW) by an amount equal to the computed bias contribution
during a 0.02 Hz Frequency Deviation
Feedback: 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 cannot 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
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?
a. 25 MWs in
b. 25 MWs out
c. 6 MWs out
d. 6 MWs in - ANSWER: a. 25 MWs in
Feedback: Inadvertent calculation is after the hour and the difference between Net
Interchange Actual and Net Interchange Scheduled.Inadvertent for hour 1: (-230 ) - (-
250) = +20Inadvertent for hour 2: (-275) - (-250) = -25Inadvertent for hour 3: (-250) -
(-250) = 0Inadvertent for hour 4: (-270) - (-250) = -20Net for the period = - 25
Balancing Authority A is currently reading a system frequency of 59.98 Hz. Its Net
Actual Interchange is +100 MW and its Net Scheduled Interchange is +100 MW. If
Balancing Authority A's frequency bias setting is 100 MW/0.1 HZ, what is ACE?
a. -20
b. 0
c. 20
d. 2 - ANSWER: a. -20
, Feedback: ACE = (100 - 100) - [-1000 (59.98 - 60.00)]ACE = 0 - (-1000) (-.02)ACE = 0 -
20ACE = -20
A Balancing Authority has a normal generation capacity of approximately 9400 MW
and its most severe single contingency is an 800 MW coal-fired steam unit. At 1430,
with an ACE value of 20 MW, a 600-MW generator trips off-line as the result of a
generator differential. This resulted in a large negative ACE for the Balancing
Authority. What value must the ACE return to and in what time frame to avoid a DCS
violation?
a. This does not constitute a reportable disturbance.
b. Must return ACE to 0 MW in 10 minutes.
c. Must return ACE to 20 MW in 15 minutes.
d. Must return ACE to 0 MW in 15 minutes. - ANSWER: a. This does not constitute a
reportable disturbance.
Feedback: The DCS criteria applies to a sudden loss of generation that exceeds 80%
of the Balancing Authorities most severe single contingency, or in this case 80% of
800 MWs which is 640 MWs. Since only 600 MWs were lost, the DCS criteria does
not apply. However, the BA should return ACE as quickly as possible.BAL-002
At 0420 hours, Interconnection frequency is 60.035 Hz. Balancing Authority A's ACE =
-50 MW. The BA's Frequency Bias is 50 MW/0.1 Hz. At 0450 hours, Frequency is
60.01 Hz and ACE = -5 MW. Frequency was high the whole hour and Balancing
Authority A's inadvertent for the hour was -55 MW. From the given information,
which of the following statements can be confirmed as true?
a. The Balancing Authority experienced a disturbance during the period
b. The Balancing Authority did not violate BAAL during the period
c. The Balancing Authority's Inadvertent is outside of range
d. The Balancing Authority violated CPS1 - ANSWER: b. The Balancing Authority did
not violate BAAL during the period
Feedback: BAL-001 Real Power Balancing Control Performance defines Control
Performance Standard and Balancing Authority ACE Limit (BAAL) equations. Those
equations can be summarized by stating that when Frequency is above 60.00 Hz and
a BA's ACE is slightly negative it is good performance as well as when Frequency is
below 60.00 Hz then a positive ACE would help support frequency. High Frequency
indicates an over generation in the Interconnection.In looking at the 30 minute
period, the only statement that can be confirmed is that the BA did not violate the
BAAL. The two data points given had a negative ACE when frequency was high.
When frequency is high, there is no ACE low limit, so we know the limit is not being
exceeded during those times. To violate the BAAL requirement the BAAL limit must
be exceeded for 30 consecutive minutes, so we know that could not be the case
based on the given data points.
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