✨ Electricity Reliability Statistics
28 NOVEMBER 2008 NEW ZEALAND GAZETTE, No. 186 4911
The Electricity Information Disclosure Requirements
(For 12 months ending 30 June 2008, 2007, 2006, 2005)
Part 6
Reliability Performance Measures to be Disclosed by Transpowera
(Disclosure Under Requirement 21)
| 2007/08 | 2006/07 | 2005/06 | 2004/05 | |
|---|---|---|---|---|
| 1. Total number of unplanned interruptionsb | ||||
| Resulting from 71 loss of supply incidents in 2007/08 | 115 | 104 | 148 | 67 |
| 2. Electricity customer interruptions in system minutesc | ||||
| Planned | 3.3 | 3.3 | 2.8 | 3.4 |
| Unplanned | 24.6d | 8.4 | 38.0 | 3.3 |
| 3. Underlying electricity customer interruptions in system minutesc | ||||
| Underlying interruptions are those interruptions of 1 system minute or less duration | ||||
| Planned | 6.8 | 6.4 | 8.8 | 5.7 |
| Unplanned | 2.1 | 2.2 | 1.5 | 3.4 |
| 4.7 | 4.1 | 7.2 | 2.3 | |
| 4. Average supply reliability (%) | ||||
| Measured by the energy supplied divided by the sum of the energy supplied and not supplied | 99.9919 | 99.9965 | 99.9879 | 99.9981 |
| 5. Uneconomic generation due to planned and unplanned transmission system unavailability (%)e | - | - | - | - |
| 6. Uneconomic generation due to HVDC system unavailability (%)e | - | - | - | - |
| 7. Uneconomic generation due to unplanned transmission system unavailability (%)e | - | - | - | - |
| 8. Planned interruption restoration performance (%) | 73.1 | 73.1 | 72.2 | 71.9 |
| 9. Unplanned interruption response (%) | 100.0 | 99.0 | 100.0 | 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.
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.
b. Where two supply voltages, or two customers, at the same station are both interrupted this is counted as two interruptions.
c. Any minor differences between the total and the sum of planned and unplanned are due to rounding.
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. Transpower considers that approximately 15.7 system minutes out of the total of 24.6 system minutes of unplanned interruptions is not totally attributable to Transpower. This arises from two major incidents during which industrial customers did not have the flexibility in their systems to be able to transfer load to alternative feeders.
e. 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 2008, No 186
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Electricity Information Disclosure Requirements for 2008, 2007, 2006, 2005
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🏭 Trade, Customs & IndustryElectricity, Information Disclosure, Reliability Performance, Transmission System, Transpower