Analysis of Damages to Oil-Filled Condenser Isolated Current Transformers of the Donbass Power System

An analysis of the damages occurring in oil-filled high-voltage current transformers having condenser isolation is presented. One of the basic indicated reasons for defectiveness involves the unsatisfactory state of the substation grounding devices. Various ameliorative measures introduced in the Donbas power system ensured the practically complete elimination of emergency failures connected with the breakdown of main insulation in current transformers. These measures include: inspection and bringing the grounding devices up to the standard condition; the introduction of ubiquitous remote monitoring under the operating voltage; the application of a mobile testing unit equipped with a small 250 kV gas-insulated transformer for recording ionization curves.