Explosion Prevention and Fire Protection of transformer: An analysis of 3 Decades of indian experience

This paper reports the salient performance and the effect of the combination of influencing sensing logics on the protection of transformers against explosion and subsequent fire. It is an analysis of nearly three decades of field experience of over 12000 nitrogen gas based ‘transformer explosion prevention & fire protection system ’connected to the medium and high voltage power transformers in the range of 11 kV to 765 kV and in the power range of 750 KVA to bank of 1500 MVA. Though this experience covers worldwide, more emphasis is placed on the Indian installations. Over 100 successful operations of the protection systems have been so far reported covering low to medium to high fault energy levels and documented by the utilities. The paper is based on the field experience of the twin combo-sensing principles of most proven protection of transformer i.e. electrical differential relay protection combined with the rapid pressure sensing techniques as the most reliable sensing systems which serve as the backbone of an efficient explosion prevention system. Reference has been made to the reasons leading to the successful operation of the protection system which have been analysed and documented by various utilities. Some of the typical failures have been indicated in the paper. The principle of operation of the Nitrogen Gas based Transformer Explosion Prevention and Fire Protection System (referred hereinafter as the ‘Protection System') is by now wellknown and for that reason, is not described in the paper in detail.