GBSQSS recommendations for offshore transmission networks GBSQSS - - PowerPoint PPT Presentation

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GBSQSS recommendations for offshore transmission networks GBSQSS - - PowerPoint PPT Presentation

Sep 05, 2023 543 likes •742 views

GBSQSS recommendations for offshore transmission networks GBSQSS Sub Group OTEG 29 September 2006 1 Contents Background Methodology Scope of offshore transmission Cost benefit analysis Offshore transmission voltage

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GBSQSS recommendations for

  • ffshore transmission networks

GBSQSS Sub Group OTEG 29 September 2006

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Contents

Background Methodology Scope of offshore transmission Cost benefit analysis Offshore transmission voltage requirements Recommendations Further work

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Background

Ofgem scoping document published in April 2006 OTEG established GBSQSS sub-group of OTEG set up to review

existing GBSQSS and test relevance to offshore transmission networks

This presentation sets our GBSQSS sub-group

assessment of the GBSQSS and its recommendations

X meetings (man hours) X thousand studies

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Methodology

Consider GBSQSS and identify areas that require review Cost benefit analysis - in line with existing GBSQSS and

ER P2/6

Formulation of working assumptions Consideration of assets likely to have an impact on

  • utcome of cost benefit analysis

Creation of network models for assessment Population of network models with real data Carry out analysis and present back to sub-group at each

meeting

Test key input variables for the value at which the

conclusion changes

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Scope of offshore transmission

Onshore system (Transmission

  • r Distribution)

Offshore Transmission system Offshore Grid Entry Point (offshore platform) Shore Generator Onshore Grid Entry Point or User System Entry Point Generator Offshore TO Onshore TO /DNO

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Scope of offshore transmission

Low voltage assets High voltage assets Preferred option Windfarm Central high voltage

  • ffshore

platform Offshore platform transformer circuits Offshore transmission network

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Cost benefit analysis

Network models Single / shared AC connections Single / shared DC connections Windfarms considered Up to 1500MW Up to 100km from shoreline Sensitivity assessment of input parameters to test

robustness of recommendation

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Offshore transmission voltage requirements

Assessment of existing arrangements At onshore connection point of offshore transmission

network to onshore electricity network

At offshore connection point of generator to offshore

transmission network

Outline possible options Consideration of voltage limits at connection of

  • ffshore network to onshore network

Consideration of voltage limits at offshore platform Comparison of options and provide recommendations

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Shore Offshore substation Onshore substation New voltage limits set for offshore platform Generator has to meet Grid Code requirements. Offshore TO Offshore generator Onshore TO or DNO Onshore Grid

  • r User

System

A B

Offshore windfarm Existing onshore GB SQSS voltage requirements apply. Recommended that Grid Code, CC.6.3.2(b) CC.6.3.2(c) and CC.6.3.8(c) apply at

  • nshore/offshore interface:
  • Reactive power capability
  • Voltage control

Offshore SQSS recommendations

Offshore transmission voltage requirements

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Recommendation – Offshore platform

For a single wind farm connection

  • Platform capacity should be planned to accept the full output of

the windfarm with no equipment loadings exceeding their pre-fault rating.

  • For AC connections; for wind farms with an export capacity of

120MW or greater, following the outage (planned or unplanned) of a single offshore transmission transformer circuit, the reduction in transformer circuit capacity should not exceed 50% of the export capacity of the windfarm connected.

  • For DC connections; for outages (planned or unplanned) of a

single offshore platform DC converter module, the loss of power infeed shall not exceed 1000MW.

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Recommendation – Offshore platform

For a multiple windfarm connections

  • Transformer capacity should be planned to accept 90% of the

cumulative installed capacity of the windfarms connected, with no equipment loadings exceeding their pre-fault rating.

  • For AC connections; for wind farms with an export capacity of

120MW or greater, following the outage (planned or unplanned) of a single offshore transmission transformer circuit, the reduction in transformer circuit capacity should not exceed 50% of installed transformer capacity .

  • For DC connections; for outages (planned or unplanned) of a

single offshore platform DC converter module, the loss of power infeed shall not exceed 1000MW.

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Recommendation – AC platform

Single windfarm connection

Offshore transmission cable network

HV assets LV assets

100MW windfarm Single

  • ffshore

platform

Platform should be designed such that the High Voltage and Low Voltage terminals of the platform transformer circuits are interconnected to allow for full flexibility of use of all assets housed upon it. For wind farms with an export capacity of 120MW or greater, following the outage (planned

  • r unplanned) of a single
  • ffshore transmission

transformer circuit, the reduction in transformer circuit capacity should not exceed 50% of the export capacity of the windfarm connected.

1 x 100MW rated unit

Substation configurations for illustration only

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Recommendation – AC platform

HV assets LV assets

500MW windfarm

Single

  • ffshore

platform

Platform should be designed such that the High Voltage and Low Voltage terminals of the platform transformer circuits are interconnected to allow for full flexibility of use of all assets housed upon it.

2 x 250MW rated units

Substation configurations for illustration only

Offshore transmission cable network

Single windfarm connection

For wind farms with an export capacity of 120MW or greater, following the outage (planned

  • r unplanned) of a single
  • ffshore transmission

transformer circuit, the reduction in transformer circuit capacity should not exceed 50% of the export capacity of the windfarm connected.

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Recommendation – AC platform

Multiple windfarm connection

Shoreline Onshore grid entry point

50MW 50MW

Offshore transmission circuit

1 x 90MW rated units

Transmission transformer capacity should be planned to accept 90% of the cumulative installed capacity of the windfarms connected, with no equipment loadings exceeding their pre-fault rating. For windfarms with a cumulative installed capacity of above 120MW, following the

  • utage (planned or unplanned) of a single
  • ffshore transmission transformer circuit, the

reduction in transformer circuit capacity should not exceed 0.5 * X% of cumulative installed capacity of the windfarm/s connected.

Substation configurations for illustration only

Offshore transmission circuit

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Recommendation – AC platform

Multiple windfarm connection

Shoreline Onshore grid entry point

500MW 500MW

Offshore transmission circuit

2 x 450MW rated units

X=90% in this example

Offshore transmission circuit Transmission transformer capacity should be planned to accept X% of the cumulative installed capacity of the windfarms connected, with no equipment loadings exceeding their pre-fault rating. For windfarms with a cumulative installed capacity of above 120MW, following the outage (planned or unplanned) of a single offshore transmission transformer circuit, the reduction in transformer circuit capacity should not exceed 0.5 * X% of cumulative installed capacity of the windfarm/s connected.

Substation configurations for illustration only

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Recommendation – Network capacity

For a single windfarm connection Transmission cable circuit capacity should be planned

to accept the full output of the windfarm with no equipment loadings exceeding the pre-fault rating.

For multiple windfarm connections Transmission cable circuit capacity should be planned

to accept X% of the cumulative installed capacity of the windfarms connected to it, with no equipment loadings exceeding their pre-fault rating

Following the outage of a single offshore transmission cable

circuit, the reduction in cable circuit capacity should not exceed 1500MW i.e. can allow up to 1500MW to be connected to a single transmission cable circuit.

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Recommendation – Network capacity

Onshore grid 500MW Single 500MW circuit Offshore platform Following the outage of a single offshore transmission circuit, the reduction in circuit capacity should not exceed 1500MW i.e. can allow up to 1500MW to be connected to a single transmission circuit.

Single windfarm connection

The transmission circuit capacity should be planned to accept the full output of the windfarm with no equipment loadings exceeding the pre- fault rating

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Recommendation – Network capacity

Multiple windfarm connection

Shoreline Onshore grid entry point

500MW 500MW

Local offshore platform Master offshore platform Single 900MW rated circuit The circuit capacity should be planned to accept 90% output of the windfarms connected to it, with no equipment loadings exceeding their pre-fault rating. Following the outage of a single offshore transmission circuit, the reduction in circuit capacity should not exceed 1500MW i.e. can allow up to 1500MW to be connected to a single transmission circuit.

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Issues for OTEG consideration

DNO ‘sandwich’ Assessment of demand connected to offshore

transmission networks

The consideration of generating plant with a higher

annual capacity factor(e.g. offshore CCGT, tidal etc) should be considered

Access rights, compensation arrangements and

transmission charging require review