Balancing, Interchange, ACE, AGC, Frequency etc Flashcards
ACE Equation
ACE = (NIa - NIs) - 10B(Fa - Fs) - Ime
NIa
Net Interchange Actual
Sum of all tie line values
NIs
Net Interchange Scheduled
Sum of all interchange schedules
sign convention for flow in / out of BA
Flow out of BA is positive (think positive = generating)
Flow into BA is negative (think negative = consuming)
B Frequency Bias (what is it)
represents areas natural response to frequency changes (intertia, droop etc)
B units
MW / 0.1 Hz
B minimum values
at least 1% of annual peak load
1% of peak generation output for areas with no load
B sign
ALWAYS NEGATIVE
Fa
Frequency Actual
Fs
Frequency scheduled - 60 Hz unless in time error correction, +/- 0.02 Hz
Ime
Interchange meter error - used for inadvertent interchange
If you can’t calculate ACE for 30 min?
Contact RC
What happens to f, ACE, and interchange if internal generation is lost?
frequency drops
ACE drops
tie line flows into area increase
What happens to f, ACE, and interchange if external generation is lost?
frequency drops,
ACE unchanged
tie line flows out of area increase (offset by frequency part of equation to keep ACE at zero).
What happens to f, and ACE, if internal load is lost?
f increases
ACE increases
flows into area decrease
What happens to f, and ACE, if external load is lost?
f increases
ACE unchanged
flow out of area decreases (offset by frequency bias portion
How does motor load change with a 1% drop in frequency?
~ 2 % load.
What happens if frequency bias is set more negative than actual frequency response?
The AGC response of the area is greater for a given frequency change
What happens if frequency bias is set less negative than actual frequency response?
The AGC response of the area is smaller for a given frequency change.
AGC mode: flat frequency control
Uses only frequency portion. When tie-line data unavailable; islanded situations
AGC mode: flat tie-line control
uses only tie-line data. When frequency data is not available. Restoration situations
AGC mode: tie-line bias
uses whole ACE equation. This is standard
What is the ACE data scan rate?
every 6 seconds
IROL correction time
<= 30 min
ISN (interrogational security network)
every 10 min
Who can issue EEA’s?
RC. Requested by BA, LSE, RSG
EEA Level 1
All avail resources in service; concern with serving load
EEA Level 2
Can’t OR anticipate lack of ability to meet demand. Identified as Energy Deficient Entity. Update RC hourly
EEA Level 3
Interruption of firm load imminent - update RC hourly
Time Error Correction - who is the time monitor
Has to be an RC. Only 1 per interconnection
Time Error Correction - minimum running time
at least 1 hour
Time Error Correction - start times
on the hour or half hour
Generator Droop
standard 5% droop
with +/- 0.36 Hz deadband
5% change in frequency ( 3 Hz) = full MW rating of generator change
What percentage of BA’s must request a time error correction cancellation ?
30%
Describe the conditions when
frequency is high
ACE is ( - )
generation exceeds load (external)
in BA, sinking more generation than scheduled but this is helping frequency
Describe the conditions when
frequency is low
ACE is ( - )
load exceeds generation (external and/or internal)
in BA, also “consuming” more generation than expected so this is exacerbating the problem)
Describe the conditions when
frequency is high
ACE is ( + )
generation exceeds load (external)
in BA, sourcing more generation than scheduled so this is exacerbating the problem
Describe the conditions when
frequency is low
ACE is ( + )
load exceeds generation (external)
in BA, sourcing more generation than scheduled but this is helping frequency
Describe BAAL requirement
clock minute average of ACE must not exceed BA’s BAAL limit for more than 30 consecutive minutes
Describe CPS1 requirement
It compares the clock minute avg of ACE with the clock minute average of the frequency deviation.
It must stay within a designated limit for each interconnection.
Essentially, it allows your ACE to be positive when frequency is low and negative when frequency is high but not the other conditions.
How is CPS1 calculated, timing wise?
Values each clock minute are averaged over the past rolling 1 year.
What is the minimum CPS1 compliance?
100%
Describe CPS2
Every 10-min average of ACE is compared with a value representative of the control area’s size in MW.
It keeps BA’s from grossly under or overgenerating and burdening neighbors with excess flow even when they are helping interconnection frequency.
THIS WAS REPLACED BY THE 30-min BAAL requirement.
Describe DCS (Disturbance Control Standard)
After a reportable balancing contingency event,
a BA (or RSG) must return ACE to pre-disturbance value OR zero w/in 15 min
What is the min. DCS compliance rate?
100%
How is a reportable disturbance (for DCS) defined?
when a balancing contingency event (occuring w/in 1 min of sudden ACE decline) is 100% or less than MSSC, and greater than either the interconnection minimum or 80% of MSSC - whichever is less
What are the interconnection minimums for a reportable disturbance?
WECC - 500 MW
ERCOT - 800 MW
EAST - 900 MW
QUEB - 500 MW
Describe the timelines following a reportable balancing contingency.
event - 15 min: contingency event recovery period. contingency reserves are used to recover ACE.
the next 90 min (after recovery period is up): BA or RSG must restore contingency reserves.
Define interchange transaction
An agreement to transfer energy from a seller to buyer that crosses one or more BA areas.
Define interchange schedule.
an agreed-upon interchange transaction:
- size (MW)
- start & end time
- begin/end ramp times & ramp rates, ramp type
required for delivery & receipt of power b/t source BA and sink BA.
Describe the different states of an interchange transaction (3):
Arranged: Request for Interchange (RFI) has been submitted.
Confirmed: No parties have denied and all req’d parties have approved the arranged interchange.
Implemented: BAs have entered the confirmed interchange into their ACE equation.
What do adjacent BA’s have to agree on as far as interchange?
Composite Confirmed Interchange (combination of all confirmed interchange) must be agreed upon with adjacent BA’s that it is:
- Identical in magnitude
- Opposite in sign
(at agreed upon intervals)
Who submits a request for interchange?
PSE (Purchasing - selling entity)
Which entities receive info about an arranged interchange?
All BA’s and TSPs on the scheduling path. They must then evaluate the transaction’s impact to reliability.
Who is responsible for confirming that all entities have approved an interchange transaction, and changing to confirmed status? Then what do they do?
Sink BA. Then they communicate the confirmed status to all BA’s and TSPs, and RCs. Also all PSEs.
Simplest equation for interchange integration (for curtailed interchange transactions)
scheduled MWhs/60min * minutes ran.
ex.
20 min - 300, 20 min - 300, 20 min - 0
300/60 * 40 = 200
Define Total Transfer Capability (TTC)
Total amount of power that can be moved from one area to another via all transmission lines.
Define Transmission Reliability Margin (TRM
safety factor to account for uncertainty in system conditions and operating flexibility as conditions change.
Define Capacity Benefits Marging (CBM)
Capacity reserved for LSE’s whose loads are located on that transmission system, to be used only in times of emergency / generation deficiency.
Definte Available Transfer Capability (ATC)
The amount of transfer capability remaining in the transmission network for further commercial activity over and above already committed uses.
ATC = TTC - TRM - CBM
Which part of the ACE equation is a psuedo-tie included in?
NIa (net interchange actual)
Treated in the same manner as a tie line.
Which part of the ACE equation is a dynamic transfer included in?
NIs (net interchange scheduled)
Treated in the same manner as an interchange schedule.
What entity is responsible for submitting a RFI for a dynamic transfer?
PSE
When does a PSE need to ensure that confirmed interchange including a dynamic transfer is updated for future hours?
- if > 250 MW, if it deviates +/- 10% or more
- if <250 MW, if it deviates +/- 25 MWh or more
- if the RC or TOp determines the deviation to be a reliability concern and notifies the PSE.
When an RC modifies an existing interchange or directs a new one, how long does the BA have to submit a modification or new RFI? Which BA is responsible?
60 min
Sink BA
What are the two types of inadvertent interchange accounts ?
On-peak and off-peak
What is unilateral payback (inadvertent interchange) ?
Occurs automatically in control scheme, controlling to a non-zero ACE within your CPS limit (limited by L10 value)
What is bilateral payback (inadvertent interchange) ?
Scheduled between 2 BA’s with inadvertent accounts in opposite directions. Entered into Meter Error component of ACE or interchange schedule.
When do interchange disputes that are not resolved need to be reported by?
The 15th calendar day of the following month.
What are the two types of inadvertent interchange?
Primary - unintentional (human error, meter error, gen not following AGC, gen/load changes in BA)
Secondary - “good”, frequency support, governor response.
Explain the difference between IFRO, FRO, and FRM.
IFRO is the frequency response obligation for the entire interconnection.
FRO is a BA’s or FRSG’s share of the interconnection IFRO. (calculated based on annual load and gen)
FRM is the actual measured frequency response taken from actual events in a BA. (Median of all frequency response observations). It needs to me equal to or more negative than the BA’s FRO.
