Electricity Asset Management Plan 2019-2029
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Vector Limited://
TARGET With the level of investment described in Section 5, our network will meet the Security of Supply Standards described in Table 2-11.
CLAUSE
DEMAND
CATEGORY
STANDARD
1
Any
Single events incurring greater than 4 SAIDI minutes
>4 SAIDI minutes: investment evaluated using a risk-based approach <4 SAIDI minutes: assessment as below
2
Any
CBD substation and subtransmission
N-1: 100% demand (no interruption) N-2: 100% demand restored in 2 hours
3
Any
Zone substations (non-CBD)
N-1: 100% demand restored in 2.5 hours (urban), 4.5 hours (rural). This requirement to be met for 95% of the year for primarily residential substations and 98% of the year for primarily commercial substations in line with our probabilistic based network planning philosophy Demand restored to all but a single distribution substation in 2.0 hours. Remainder restored in repair time Primarily underground: demand restored to all but 800 kVA , 2.5 hours (urban). Remainder restored in repair time Primarily overhead: Demand restored to all but 2.5 MVA, within 2.5 hours (urban) and 4 hours rural. Remainder restored in repair time
4
Any
CBD distribution feeders, 11 kilovolt (kV) or 22 kV Distribution feeders (non-CBD), 11 kV or 22 kV
5
Any
6
Any
Distribution substations (11 kV/400 kVA)
Restored within repair time
7
Any
Distribution feeders (400 V)
Restored within repair time
8
Any
All subtransmission
Maximum of one month on reduced security
9
Any
Subtransmission and zone substations
Spatial separation of primary network assets sufficient to avoid common mode failure
Table 2-10 SoSS
2.5.2 SYSTEM AVERAGE INTERRUPTION DURATION INDEX (SAIDI) SERVICE LEVEL
DEFINITION The SAIDI index measures the average duration of outages per customer per RY, the value expressed in minutes. This is one of the key metrics used to assess the reliability of the network. It is calculated as the sum of the duration of all customer duration interruptions divided by the total number of customers served, where interruptions are for a period of 1 minute or longer. MEASUREMENT 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 = (𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑜𝑜𝑜𝑜 𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚) / (𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐) SAIDI only measures outages caused by an event on the High Voltage (HV) network and does not include the LV network. The SAIDI dataset is normalised using a process defined by the Commerce Commission in the DPP. This process reduces planned interruptions by 50% as it is considered that customers are less impacted by interruptions that are planned. It also limits unplanned SAIDI on days where a major event has occurred (e.g. storms) to prevent these extreme events distorting the overall SAIDI data. The following formula is used:
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 〗
_𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 = (0.5 𝑥𝑥 〖
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 〗
_𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 ) + 〖
𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 〗
_𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢𝑢
〖
Where:
〖 SAIDI 〗 _planned is the sum of daily planned SAIDI values in the assessment period; and
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