Ops ForumConstraint Management August 02

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


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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Circuit Pre Fault Post Fault 10 Minute Continuous


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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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


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

Documents

Ops ForumConstraint Management August 02