Electricity Asset Management Plan 2019-2029
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Vector Limited://
Figure 4-13 Age Profile for Capacitor Banks
Condition and Health It is clear from the condition and number of faults in our capacitor banks that they are steadily approaching end of life and more intensive and costly maintenance, and remedial works are needed to keep them in service. Strategy In terms of power factor there are presently two different requirements applied to different GXPs that supply Vector’s network: • For category A GXPs the Connection Code (Schedule 8 to DTA) specifies unity power factor. However, Vector has an agreement with Transpower on non-compliance with the connection code, subject to following condition: ‘Vector maintaining an aggregate Power Factor across all Point of Services in this category during Regional Coincident Peak Demand Periods of not less than 0.96 lagging or 0.97 leading’. • For category B GXPs the Common Quality Obligations (of the Connection Agreement) specifies that the power factor at any point of service in this category must not be less than 0.95 leading or lagging. Our Digsilent network modelling tool shows which capacitor banks need to be in service to maintain power factors and provide voltage support and this in turn informs our investment programme (detailed in Section 5). As informed by our model and monitoring of power factors at GXPs some ageing capacitor banks can and will be removed at end of life and used as a source of spares but others will need to be maintained and refurbished as required. Most notable are capacitor banks at zone substations being fed from the Penrose 110 kV GXP and Hobson 110 kV GXP. When both Albany 110 kV and Wairau 33 kV are importing reactive power from the grid the power factor goes low which means the capacitor banks at Wairau zone substation will need refurbishment to ensure their continued operation. Vector uses demand-side load management systems on its distribution network as a customer-centric service to reduce peak demand to limit transmission charges for customers or to help with network congestion. At all other times this load is offered into the wholesale electricity market as instantaneous reserve. Due to the separate legacy power board network philosophies at the time of installation, two signalling systems exist: ‘ripple injection’ over power lines in the Auckland network and in the Northern network, ripple injection and a ‘pilot wire’ system. Customers can sign up to a ‘controlled’ (lesser cost) tariff under either the ripple signal system or pilot cable system. Both these systems signal customer’s hot water cylinders to switch on or off, shifting Vector’s network demand peaks for up to three hours continuously within a 24- hour period. The signalling equipment also switches some streetlights on and off at dusk and dawn on behalf of Auckland Transport. 4.3.5 LOAD CONTROL Overview
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