Number of MV/LV transformers

From Electrical Installation Guide

For every MV/LV substation, the definition of the number of MV/LV transformers takes into account the following criteria:

  • Total power supplied by the substation
  • Standardization of the rated power to reduce the number of spare transformers
  • Limit of the rated power. It is recommended to set this limit at 1250 kVA in order to facilitate the handling and the replacement of the transformers
  • Scalability of the installation
  • Need to separate the loads having a high level of sensitivity to the electrical perturbations
  • Need to dedicate a transformer to the load generating a high level of perturbation such as voltage dips, harmonics, flicker
  • Need for partial or total redundancy. When required, two transformers each sized for the full load and equipped with an automatic change-over are installed
  • Loads requiring a dedicated neutral system. IT for example to ensure the continuity of operation in case of phase to earth fault