Pre test
________% of load shed will increase Frequency 1 Hz in an Island
6-10%
A system wide voltage reduction greater than _____ must be reported to NERC within 24 hours.
3%
A 5% decrease in Voltage results in a
3% decrease in load
Contingency Reserve Restoration Period
90 minutes following the 15 minute Contingency Event Recovery Period
Attaining Balancing Authority
A BA bringing generation or load into its effective control boundaries through dynamic transfers from the Native Balancing Authority
A Native BA is?
A BA from which a portion of its physical interconnected generation and/or load is transferred from its effective control boundaries to the Attaining BA through a dynamic transfer.
A substation & all the transmission lines into the substation suddenly indicate de-energized on SCADA. The CBs at the substation indicate closed, but the remote line breakers indicate open. What would be the most probable cause for this activity?
A CB failed to trip, initiating a breaker-failure relay operation
A common utility substation battery guideline is to have enough battery capacity to handle a (an) __________ outage of AC power to the substation battery chargers & still be able to serve
8-12 hour
What has more capacitance, an underground cable or an overhead line?
An underground cable
Regulating Reserve
An amount of reserve responsive to AGC, which is sufficient to provide normal regulating margin.
The thing that makes a generator dynamic is?
An auto voltage regulator
Motor loads are most impact by
Frequency
The primary source of reactive power comes from?
Generators
Operating Reserve
Is referring to all the different reserves as a whole
Droop Dead-band (and its normal range)
Is the amount of frequency change a governor must see before it starts to respond. +(-).036
Transmission Operators are implementing their system restoration plan after a major system disturbance. They are ready to energize a blacked-out area, what should the system operator do first?
Isolate the load
Impedance
It is the combined effect of resistance, inductive reactance, and capacitive reactance in an AC circuit.
Reserves in order (Starting with Load)
Load > Regulating reserves > Contingency reserves (spinning) > Reserve sufficient to meet DCS > non spinning contingency reserve
A Reportable Balancing Contingency Event (or DCS event) is...
Loss of GENERATION occurring within a one-minute interval of an initial sudden decline in ACE that results in a loss of MW output equal to or greater than 80% of the MSSC.
A portion of a Reliability Coordinator Area is experiencing low voltage and there are no generation redispatch options available. What action should the Reliability Coordinator take first?
Lower transfers across area to unload transmission lines
MVAR output = ?
MVAR output = MVAR rated x (Voltage actual/Voltage rated)^2
MVA = ?
MVA^2 = MW^2 + MVAR^2
Generators produce what type of power
MW and MVAR Real and reactive power
MSSC
Most Severe Single Contingency Loss of largest generator in the interconnection
Secondary Inadvertent Interchange
Non-scheduled energy transfer. It can accumulate due to factors such as frequency support, regulation, and governor response. good!
# of poles in a generator or speed in RPM equation
Np = 7200 N = RPM P = # of poles
What is the primary and secondary frequency response?
Primary is the Automatic Governor Response Secondary is the AGC
PSE
Purchasing‐Selling Entity
A transmission line is scheduled out for maintenance. Power Flow studies indicate another transmission line will overload as a result. The Transmission Operator must?
Reschedule the transmission line maintenance
Power losses happened due to?
Resistance
A 300 MW rated generator is currently operating at 150MW with a 5% droop setting. If frequency drops to 59.80 Hz, what is the response of this generator?
Step 1. Find that 5% of 60 Hz = 3 Hz Step 2. Generator MW divided by droop setting in Hz(300 MW/ 3 Hz) or (100 MW/ 1 Hz) Step 3. Use the above ratio (100MW / 1Hz) and multiply by the frequency drop of 0.2 Hz Answer: 20 MW
Static VAR Compensators (SVC)
Supplies and Absorbs VARS. Adjusts automatically. Is dynamic
Shunt capacitors
Supply Static MVARS close to the load
If AGC isn't working properly...
Take it off auto control and investigate
Constant (Flat) frequency control
considers only the frequency portion of the ACE. This control can be used if the BA area is isolated from all other BA areas and/or the status of the Tie-lines is uncertain.
What exempts generators from having its AVR in service?
exempted by the Transmission Operator or when the generator is in startup, shutdown, or testing mode.
MVAR flow from...
high voltage magnitude to low voltage magnitude
MWs flow from...
higher power angle to lower power angle
In the ACE equation, a Pseudo‐tie is...
included in NI ACTUAL in the same manner as a Tie‐Line.
In the ACE equation, a Dynamic Schedule is...
included in NI SCHEDULE in the same manner as an Interchange Schedule.
Series Reactors
increase impedance of the line, reduce fault current.
Contingency Reserve
is additional capacity to be used during abnormal system conditions (for DCS events)
Under Frequency Load Shedding (UFLS)
is to stabilize the imbalance between generation and load that has been created by a system disturbance. How does UFLS accomplished this? by shedding load prior to generation tripping
Shunt reactors are used for what component?
long high-voltage transmission lines
Series Capacitors
reduce a line's inductive reactance by effectively "electrically" shortening the line and reducing the reactive power losses. Raises the SIL Increases voltage, lowers current
Shunt capacitors output is dependent on?
system voltage output decreases as system voltage decreases.
Tie-line bias control
the BA utilizes the entire ACE equation. Is used for normal operations
Surge Impedance Loading (SIL) is the point where...
the active power flowing on the power line requires 0 VAR from the rest of the system to support its voltage.
If another event occurs within the 15-minute contingency period, what ACE must you recover?
the required ACE recovery is reduced by the MW loss amount of the subsequent event
In inductive loads, the ____ wave is ahead of the ______ wave.
the voltage wave is ahead of the current wave.
A(n) __________ tool is a software tool that uses tag data & distribution factors to assist the RCs with congestion management.
wide area reliability
If a capacitor is placed in an AC circuit, it will....
will cancel some portion of whatever inductive effects are present and raise voltage.
What units do not have a governor response?
wind and solar
Capacitance oppose changes in ________
Voltage
Resistive loads are most impacted by...
Voltage
DCS compliance %? DCS recovery time?
100% compliance 15 minute recovery
Cold-load pick-up can involve current flows of up to what maximum level?
10x normal
Inductive loads examples
1) Motors 2) Transformers 3) Heavily-loaded transmission lines
A Responsible Entity must deploy Contingency Reserve to respond to all DCS Events, but is not subject to compliance with the 15‐minute recovery requirement if...
1) The Balancing Authority is experiencing a Reliability Coordinator declared Energy Emergency Alert 2) The Responsible Entity experiences multiple Contingencies classified as a single event (within 60 seconds of each other) and the combined MW loss exceeds the Most Severe Single Contingency
What are the AGC modes?
1) Tie-line bias control 2) Constant (flat) interchange control 3) Constant (Flat) frequency control
A BA and adjacent BA must ensure a common source for? (3)
1) Tie‐Line 2) Pseudo Tie 3) Dynamic Schedules
the PSE updates tags for a confirmed interchange greater than 250 MW if it deviates by? If equal to or lesser than 250 MW?
10% 25MW
Contingency Event Recovery Period
15 minutes
Interconnected System, 1% drop in frequency results in...
2% drop in load (motor)
If a BA is unable to calculate their ACE for more than _______ it must notify its RC.
30 minutes
In restoration, connect ___% of the total synchronized generation of load at one time.
5%
BAAL (ACE Limit) time limit to get back in bound?
< 30 minutes
Power loss =
= I^2 x R
What amount of manual load shed is reportable?
> 100 MW
Reportable loss of load
>300 MW
CPS compliance?
>=100%
What value must ACE be returned to following a disturbance?
ACE must be returned to 0 or to its previous negative number it was before the disturbance, within the 15-minute period. If it was positive prior to the event, it must be returned to 0.
Governor response vs AGC
AGC pulses generator units up or down based on a specific BA's ACE number. (when they are at fault) Governor Response happens in all BA areas on the interconnection when the interconnection frequency drops or raises (For those at fault and those not)
How do you calculate Available Transfer Capability (ATC)?
ATC = TTC - Transmission Reliability Margin - Capacity Benefits Margin CBM = transfer preserved for times of emergency generation deficiencies. It is used by the Load‐Serving Entity and Reserve Sharing Group (RSG) only. TRM = accounts for the inherent uncertainty in system conditions and the need for operating flexibility to ensure reliable system operation as system conditions change
ATC = ?
ATC = Total Transfer Capability - Reserve Margins
Shunt Reactors
Absorb reactive power
Synchronous Condensers
Absorbs and supplies reactive power Is powered by MW from the grid
Frequency and voltage magnitude on each side of the breaker and the power angle across the breaker must be within proper limits when synchronizing transmission systems that have separated or islanded. If not within proper limits, the system operator should take which action?
Adjust area generation levels
Transmission Service Provider performs what function?
Administers tariff
Which performance measure provides the best indication that a Balancing Authority maintains enough Operating Reserve?
CPS2
Increasing AC frequency has what effect on capacitive and inductive reactance?
Capacitive reactance decreases with increasing AC frequency. Inductive reactance increases with increasing AC frequency.
Constant (flat) interchange control
Considers only the Interchange actual and scheduled part of the ACE. It may be used if the frequency signal is unavailable. AGC responds only to interchange deviations.
Inductance oppose a change in....
Current
In capacitive loads, the ____ wave is ahead of the ______ wave.
Current wave is ahead of Voltage wave
Bottom Line Rule
Each BA of Reserve Sharing group is required to carry Contingency Reserve equal to or greater than the Most Severe Single Contingency
How often should a BA scan their ACE?
Every 6 seconds
Most loads on the system are?
Inductive
In a parallel circuit, power will flow on the path of?
Least impedance
Capacitive load example
Lightly loaded T-lines
Power =
P = V x I Power = Voltage x Current
Power Factor
PF = MW/MVA
What would you expect to experience during a Geo-Magnetic disturbance?
Significant low frequency induced currents enter the system through the grounded transformer neutrals, causing system overloads and harmful system wide harmonics
Which entity develops and implements the Operating Plan to mitigate Capacity or Energy Emergencies including notification process?
The BA
Primary Inadvertent Interchange
Unintentional transfers of energy. It can be a sign of problems within a BA resulting from human, scheduling, or meter errors. BAD
Voltage = ?
V = I x Z Voltage = Current x Impedance
The primary cause of Low Voltage is?
VAR Losses associated with heavy power transfers
A storm blows A phase and B phase conductors of a 138 kV transmission line together, creating a phase to phase fault. The magnitude of the current and voltage changed instantly causing the line distance relays at each end of the line to operate. How did the current and voltage on that line change providing the input for the relay to indicate a fault on the line?
Voltage decreased and the current increased
Impedance formula
Z^2 = R^2 + (XL - XC)^2 XL: inductive reactance XC: capacitive reactance
Frequency Response Obligation (FRO) is calculate how? Reviewed how often?
a BA's percentage of the annual generation and load in the interconnection to which it belongs. Reviewed Annually
A(n) ______ generator is delivering VARs to the system.
overexcited
