Electricity Asset Management Plan 2019-2029
94
Vector Limited://
Figure 4-8 Age profile for 33 kV and 22 kV subtransmission cables by type
Condition and health Our experience and monitoring of condition shows that in terms of underground subtransmission networks, ageing 33 kV and 22 kV PILC cables are currently the worst performing in Vector’s subtransmission network. Failures on this type of cable are such that continuous repair and piecemeal replacement are not economical anymore. We are also seeing more failures on some 33 kV oil filled cables. Strategy Vector maintains its fleet of 33 and 22 kV subtransmission feeders, some of which are approaching forecast end of life, to provide service for as long as possible into the future without increasing the risk profile of this asset to an unacceptable level. Our experience and monitoring of the condition of 33 kV and 22 kV oil filled cable have shown that with proper and regular maintenance, and continuous condition monitoring, as per Vector’s maintenance standard ESM301, the life of this asset can be extended well into the future and in some instances beyond its forecast end of life. The cyclic inspections of oil-filled cables are supplemented by real time monitoring of oil-pressure using SCADA, complete with operational alarms, to alert the Electricity Operations Centre (EOC) of low oil-pressure. Our replacement programme focuses on the PILC cables but a number of oil-filled cables are also forecast to be replaced in the 10-year AMP period. Our solid insulated XLPE subtransmission cables are performing well, and although some circuits have been in service since the 1970s, there is no need to replace any of this type of cable. Vector still operates a gas-filled subtransmission cable between Kingsland zone substation and Ponsonby zone substation and its condition warrants replacement that is scheduled for completion in FY20.
Our CBARM model for this fleet is being developed and is scheduled for completion in FY19, and will further enhance our capability to plan replacement based on asset health, criticality and risk.
4.2.3 SUBTRANSMISSION 110 KV OVERHEAD LINES Overview
Vector has three 110 kV overhead subtransmission lines that run between Transpower Albany and Wairau zone substation. Two circuits exist on single poles through the Albany, Unsworth Height and Glenfield areas to Wairau zone substation. A third circuit exists through Greenhithe and Glenfield to Wairau. The three lines supply three 110 kV/33 kV transformers
Made with FlippingBook - professional solution for displaying marketing and sales documents online