Automatic disconnection under AS/NZS 3000 and the impact on supply utilities

Abstract

While electricity distributor works are exempt from compliance with AS/NZS 3000 under most circumstances, all of the electrical installations connected to the network do have to comply.AS/NZS 3000 requires automatic disconnection under both overcurrent and earth fault conditions. Compliance with automatic disconnection under earth fault conditions is often measured by earth fault loop impedance, but this is only part of the picture.In any fault current analysis there needs to be some confidence in the impedance of the upstream network. The designers, contractors and inspectors are using assumptions to assess their compliance in a self regulated industry, and some of these assumptions may not be valid.This paper discusses the confidence limits and the impact on contractors and installers complying with AS/NZS 3000.