New Zealand Gazette – 2006 – No. 149

Page 4328

✨ Electricity Reliability Statistics



4328

NEW ZEALAND GAZETTE, No. 149

24 NOVEMBER 2006

The Electricity Information Disclosure Requirements 2004

(For 12 months ending 30 June 2006, 2005, 2004, 2003)

Part 6

Reliability Performance Measures to be Disclosed by Transpower

(Disclosure Under Requirement 21)

  1. Total number of unplanned interruptions
    Resulting from 80 loss of supply incidents in 2005/06*
    | 2005/06 | 2004/05 | 2003/04 | 2002/03 |
    |--------|--------|--------|--------|
    | 148 | 6 | 5 | 72 |

  2. Electricity customer interruptions in system minutes**
    | | 2005/06 | 2004/05 | 2003/04 | 2002/03 |
    |---------------|--------|--------|--------|--------|
    | Planned | 2.8 | 3.1 | 1 | 3.6 |
    | Unplanned | 40.8 | 6 | 5 | 4.2 |

  3. Underlying electricity customer interruptions in system minutes *
    Underlying interruptions are those interruptions of 1 system minute or less duration*
    | | 2005/06 | 2004/05 | 2003/04 | 2002/03 |
    |---------------|--------|--------|--------|--------|
    | Planned | 8.8 | 5.7 | 5.3 | 6.3 |
    | Unplanned | 1.5 | 1.4 | 1.3 | 3.6 |

  4. Average supply reliability
    Measured by the energy supplied divided by the sum of the energy supplied and not supplied
    %
    | 2005/06 |
    |-----------|
    | 99.9879 |

  5. Uneconomic generation due to planned and unplanned transmission system unavailability %
    Uneconomic generation relates to the amount of electricity generated from any source other than the most economic source.

  6. Uneconomic generation due to HVDC system unavailability %

  7. Uneconomic generation due to unplanned transmission system unavailability %

  8. Planned interruption restoration performance
    %
    | 2005/06 |
    |--------|
    | 72.2 |

  9. Unplanned interruption response
    %
    | 2005/06 |
    |--------|
    | 100.0 |

The information compiled using estimated information includes Part 6 sections 2, 3 and 4. The methodology used to calculate the estimated information is documented and available from Transpower upon request.

Uneconomic generation (Part 6 sections 5, 6 and 7) is not relevant in the market environment because scheduling is now based on offered price, not economic cost. In the market, 'offers to generate' are made after taking constraints into account and it is not possible to predict what a generator would have offered if the constraint was not present. As a result data is not available to allow a calculation and a null entry has been returned.

The reliability performance measures given in Part 6 do not include the performance of the 34km of circuit leased to other parties because Transpower does not collect operational data for these assets.

  • Where two supply voltages, or two customers, at the same station are both interrupted this is counted as two interruptions.

** Any minor differences between the total and the sum of planned and unplanned are due to rounding. System minutes of interruptions are not counted if energy is made up by backfeed from another point of supply or by embedded generation within a customer’s network.



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Online Sources for this page:

VUW Te Waharoa — PDF NZ Gazette 2006, No 149


Gazette.govt.nz — PDF NZ Gazette 2006, No 149




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