✨ Electricity Reliability Performance Measures
28 NOVEMBER 2011 NEW ZEALAND GAZETTE, No. 184 5355
The Electricity Information Disclosure Requirements
(For 12 months ending 30 June 2011, 2010, 2009, and 2008)
Part 6
Reliability Performance Measures to be Disclosed by Transpower^a^
(Disclosure Under Requirement 21)
| 2010/11 | 2009/10 | 2008/09 | 2007/08 | |
|---|---|---|---|---|
| 1. Total number of unplanned interruptions^b^ | 89 | 106 | 112 | 115 |
| Resulting from 60 loss of supply events in 2010/11 | ||||
| 2. Electricity customer interruptions in system minutes^c^ | 15.2 | 23.5 | 18.1 | 28.0 |
| Planned | 3.6 | 1.2 | 2.0 | 3.3 |
| Unplanned | 11.6 | 22.2 | 16.1 | 24.6 |
| 3. Underlying electricity customer interruptions in system minutes^c^ | ||||
| Underlying interruptions are those interruptions of one system minute or less duration | 4.0 | 5.3 | 5.9 | 6.8 |
| Planned | 1.1 | 1.2 | 0.9 | 2.1 |
| Unplanned | 2.9 | 4.0 | 4.9 | 4.7 |
| 4. Average supply reliability (%) | ||||
| Measured by the energy supplied divided by the sum of the energy supplied and not supplied | 99.9957 | 99.9932 | 99.9946 | 99.9919 |
| 5. Uneconomic generation due to planned and unplanned transmission system unavailability (%)^d^ | - | - | - | - |
| 6. Uneconomic generation due to HVDC system unavailability (%)^d^ | - | - | - | - |
| 7. Uneconomic generation due to unplanned transmission system unavailability (%)^d^ | - | - | - | - |
| 8. Planned interruption restoration performance (%) | 68.6 | 77.5 | 76.7 | 73.1 |
| 9. Unplanned interruption response (%) | 100.0 | 99.1 | 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. 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 2011, No 184
✨ LLM interpretation of page content
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Reliability Performance Measures to be Disclosed by Transpower
(continued from previous page)
🌾 Primary Industries & ResourcesReliability, Interruptions, Supply reliability, Uneconomic generation, Transmission system