LVAC Switchboards

Transpower’s transmission stations all require low voltage ac [LVAC] supplies to maintain the station and communication batteries in a charged state, and to provide auxiliary supplies for the operation and maintenance of the equipment.

In all grid exit point (GXP) substations there must be one local service supply derived from each power transformer, up to a maximum of three (3).

For switching stations, interconnecting stations without GXP transformers, and grid injection stations, there must be two independent sources of LVAC supplies, preferably sourced from within the station.

For transmission cable termination stations one 230 V single phase supply derived from the local network must be provided.

LVAC boards, with the exception of those at cable termination stations, must be expandable to three incoming supplies with automatic selection to maintain supplies following a supply source outage.

For physically large sites with loads in excess of 200 kVA and distances which imply larger than acceptable voltage drops at 400 V, additional LVAC switchboards conforming to the standard two x three phase sources design with an additional layer of 11 kV distribution inserted between the source and these LVAC boards.   The source in this case must be either 11 kV directly into a 9 or 11 panel switchboard or 33/11 kV transformers of 750 kVA or 1000 kVA as required.  The standard LVAC boards must be sited adjacent to the loads they are to supply.

LVAC Switchboard drawings:-

Standard Drawings 400V LVAC

Standard Drawings 400V LVAC Switchyard Lighting 

Standard Drawing 400V Distribution Panel