Design of Low Voltage Reticulation Systems

Power linesThis information summarises Northpower's approach to supplies for common low voltage reticulation and includes technical details on electricity metering.

The information is intended to provide a basis for Northpower personnel quoting for developers. It may also be sent to developers directly to provide information on the options available. Note that the information is applicable to connections within the Northpower network area. Personnel designing for other network areas must obtain the design parameters applicable to those networks.

Urban Residential - Standard Design

Urban constructionUnderground reticulation shall be designed so that two phases are available at the boundary of each lot, including those serviced by spur cables along access ways and rights-of-way. In general, reticulation will be three phase with one fuse per lot at the pillar services, plus allowance for a second fuse to be fitted only when required. In underground areas, construction plans shall show the phase allocated for the first connection and the phase for the second if required.

The load shall be balanced across the three phases by connecting service lines to sequential phases. The Developer may request the reticulation to be designed to a higher capacity. The service to a "standard" dwelling will generally be single phase except where there is a long service line and an additional phase is required to reduce the voltage drop. Large dwellings (load in terms of electrical load) will generally be two phases. When individual consumers request greater capacity, diversity of the original design LV network can be considered. The LV cut out is generally 60/63A unless otherwise specified.

Urban Commercial - Light Industrial

Underground reticulation shall be designed so that three phases are available at the boundary of each lot. Generally the minimum capacity of 60A, without diversity. Provision for additional capacity is recommended (e.g. spare ducts).

Urban Commercial - Heavy Industrial

Shall be designed to developer's or consumer's specific requirements.

Rural Residential

Urban Power supplyIn the case of multiple lots supplied from one transformer, three phases should be available to each lot. The service will generally be two or three phase, as required to ensure the voltage drop is within regulatory limits and load balance on the transformer. In the case of a single lot or dwelling, the supply available will be three phase if a three phase transformer is provided and the service should also be three phase to ensure the transformer load is balanced. If a single phase 460v transformer is provided, the supply available will generally be two phase. The service will generally be two phase, but single phase can be accommodated by paralleling the output of the two secondary windings of the transformer. The LV cut out is generally 30/32A, 60/63 A depending on the situation.

Rural Industrial

Commercial power installationGenerally the supply will be three phase for most situations, e.g. dairy shed, large pumps etc. Extra light industrial installations can be two, or single phase if required. "Extra light" generally refers to small pumps, and implement sheds with minimum electrical load. The LV cut out will be sized to suit the situation.

For further information including metering diagrams, please visit our website or call us on (09) 430 1803.