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Redclyffe New Interconnecting Transformer

Overview

What we're doing

Two 220/110 kV interconnecting transformers at Redclyffe supply the majority of the Hawke’s Bay load (except load at Whirinaki and Whakatu which is supplied from the 220 kV system).  The transformers provide:

• a nominal installed capacity of 160 MVA; and
• n-1 capacity of 114/120 MVA (summer/winter)

An outage of either interconnecting transformer can overload the remaining transformer during periods of either:

• high load and low regional generation; or
• low load and high regional generation

The extent of overloading is influenced by the level of Waikaremoana hydro generation made up of stations at Tuai, Piripaua and Kaitawa.

With no generation output from Waikaremoana, the peak load is forecast to exceed the transformers’ n-1 winter capacity by approximately 35 MW in 2008, increasing to approximately 53 MW in 2018 (see Table 14 5).

Table 14 5: Redclyffe 220/110 kV Transformer Overload Forecast

Why we're doing it

This overload is presently managed operationally by transferring load (within the local lines network) from the 110 kV transmission network to the 220 kV transmission network and by constraining-on generation at Waikaremoana.

Transpower is investigating a number of options to address this issue including a new interconnection transformer at Redclyffe.

The project’s estimated cost will depend on the option chosen, with an indicative commissioning date of 2009/10.

Project Status

This is a proposed investment project awaiting Electricity Commission approval.

• Project Reference:
  RDF-POW_TFR-DEV-02
• Region:
  Hawkes Bay
• Status:
  Proposed
• Cost Bracket:
  A "Up to $5 million"
• Timing:
  2008