✨ Electricity Reliability Statistics
The Electricity Information Disclosure Requirements
(For 12 months ending 30 June 2009, 2008, 2007, 2006)
Part 6
Reliability Performance Measures to be Disclosed by Transpower
(Disclosure Under Requirement 21)
| 2008/09 | 2007/08 | 2006/07 | 2005/06 | |
|---|---|---|---|---|
| 1. Total number of unplanned interruptions | ||||
| Resulting from 64 loss of supply incidents in 2008/09 | 112 | 115 | 104 | 148 |
| 2. Electricity customer interruptions in system minutes | ||||
| Planned | 2.0 | 3.3 | 3.3 | 2.8 |
| Unplanned | 16.1 | 24.6 | 8.4 | 38.0 |
| 3. Underlying electricity customer interruptions in system minutes | ||||
| Underlying interruptions are those interruptions of one system minute or less duration | ||||
| Planned | 0.9 | 2.1 | 2.2 | 1.5 |
| Unplanned | 4.9 | 4.7 | 4.1 | 7.2 |
| 4. Average supply reliability (%) | ||||
| Measured by the energy supplied divided by the sum of the energy supplied and not supplied | 99.9946 | 99.9919 | 99.9965 | 99.9879 |
| 5. Uneconomic generation due to planned and unplanned transmission system unavailability (%) | - | - | - | - |
| 6. Uneconomic generation due to HVDC system unavailability (%) | - | - | - | - |
| 7. Uneconomic generation due to unplanned transmission system unavailability (%) | - | - | - | - |
| 8. Planned interruption restoration performance (%) | 76.7 | 73.1 | 73.1 | 72.2 |
| 9. Unplanned interruption response (%) | 100.0 | 100.0 | 99.0 | 100.0 |
Notes
a. 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.
b. The reliability performance measures given in Part 6 do not include the performance of the 34kV or circuit leased to other parties because Transpower does not collect operational data for these assets.
c. Where two supply voltages, or two customers, at the same station are both interrupted this is counted as two interruptions.
c. System minutes of interruptions do not include energy made up by backfeed from another point of supply or by embedded generation within a customer's network.
d. 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.
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NZ Gazette 2009, No 172
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Transpower New Zealand Limited Lines Business Annual Depreciated Historic Cost Reconciliation Report
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🏗️ Infrastructure & Public WorksElectricity, Transmission, Statistics, Efficiency, System Performance