Case study: Implementation of Dynamic Rating for Transformers in a distribution network

In 2012, Unison Networks Limited implemented Dynamic Power Transformer Rating (DPTR) on most of the power transformers in its distribution networks. The implementation involved 50 medium power transformers across three different regions in New Zealand - Hawkes Bay, Taupo and Rotorua. The DPTR scheme utilised an in-house developed algorithm that has been designed based on the IEC60076-7 Loading Guide for Oil Immersed Power Transformer Standard. Every three minutes, the algorithm samples real time data from various sensors installed in the networks and calculates the maximum loading that each individual transformer can safely carry. This paper will discuss the outputs from the algorithm and the benefits achieved from the implementation.