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7/31/2019 Ops ForumConstraint Management August 02
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Const ra int Managem ent
Adrian Lewis
Operations and Trading
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AgendaK What is a Transmission Constraint
K How we manage constraints
K Thermal Constraint - Example
K Summary
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What is a Transm iss ion Const ra in t (i i )
K Thermal Constraints
- Relate to thermal capacity oftransmission assets.
- Failure to manage may result in
damage to transmission assets- Failure to manage may result in
infringement of clearance.
- In extreme situations could lead tocascade tripping (Aukland!).
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What is a Transm iss ion Const ra in t (i i i )
K Voltage Constraints
- Reactive Power Related
- Generally Localised
- Insufficient MVAr reserves may
result in unacceptable voltagedeviations and in extreme situationsvoltage collapse.
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What is a Transm iss ion Const ra in t (iv )
K Stability Constraints
Two Types:
Transient - post fault - keepinggenerators in synchronism
Dynamic - steady state oscillationbetween generators
- Caused by weak links to high
generation export groups.
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How w e m anage c ons t ra in ts (i )K Co-ordinate outages (OC2 data)
K Transmission options
- Modify substation running arrangements
- Rating Enhancements (MORE, CTM, HotWire)
K Change demand pattern:Balancing Services Contracts
K Change generation pattern:
BOAs, Schedule 7, BS Contracts
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How w e m anage c ons t ra in ts (i i )K Flexible working:
Live Line
Extended working hours
By-pass arrangements
Defer Outage
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Therm al Const ra in t - Ex am ple
Exporting Group
Importing Group
1 2 3 4 5 6Circuit Pre Fault Post Fault 10 Minute Continuous
Flow/MVA Flow/MVA Rating/MVA Rating/MVA
1 900 0 2800 2600
2 900 0 2800 2600
3 700 2000 1900 17004 0 0 0 0
5 350 600 1500 1200
6 350 600 1500 1200
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Therm al Const ra in t - Ex am pleK Credible fault results in unacceptable
Loading of Circuit 3
K If sufficient post fault actionsavailable need to restrict overload to10 minute rating + further action in 10
minutes to reduce to continuous rating
K If no post fault actions need to restrictoverload to continuous rating
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Opt ions Avai lab leK Can we re-configure the system to reduce
overload
K Defer Outage - can the work be accommodated atsome other time
K Can we reduce the outage duration
K Can we enhance the circuit rating
K Can we reduce generation/increase demand inexporting group or increase generation/reducedemand in the importing group
- What are the forecast costs- What is the duration
- BM vs BS
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Ex am ple Cont inued
Exporting Group
Importing Group
1 2 3 4 5 6Circuit Pre Fault Post Fault 10 Minute Continuous
Flow/MVA Flow/MVA Rating/MVA Rating/MVA
1 900 0 2800 2600
2 900 0 2800 2600
3 700 2000 2000 1800
4 0 0 0 0
5 350 600 1500 1200
6 350 600 1500 1200
MORE installed on
Circuit 3 - 10 minute and
continuous ratings
increase by 100 MW
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Ex am ple Cont inued
Circuit Pre Fault Post Fault 10 Minute Continuous
Flow/MVA Flow/MVA Rating/MVA Rating/MVA
1 900 0 2800 2600
2 900 0 2800 2600
3 700 1400 2000 1800
4 0 0 0 0
5 350 900 1500 1200
6 350 900 1500 1200
~~
~
~
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Ex am ple Cont inued
Qu. What if no transmission options and BM
costs expensive?
An. Find an Alternative (e.g. Contract with
demand/generation non)
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Ex am ple Cont inuedCircuit Pre Fault Post Fault 10 Minute Continuous
Flow/MVA Flow/MVA Rating/MVA Rating/MVA
1 900 0 2800 2600
2 900 0 2800 2600
3 700 1800 2000 1800
4 0 0 0 0
5 350 600 1500 1200
6 350 600 1500 1200
~x
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SummaryK Transmission constraints can be
complex
K We have many options available tomanage them
K Alternatives to BM Units are availableand have been successfully used
K We will investigate all options to
minimise costs