Protective Wall: Arc Cube Installation

During a routine start-up of a 309 MW generator, in a power station, the new 5.46MVA excitation transformer supplying the excitation system for this generator suffered considerable damage due to a polyphase short circuit on the high voltage (HV) side. At the time of the incident, the generator was not yet connected to the grid, more precisely, the generator circuit breaker was open. An investigation and analysis, involving experts, was conducted to establish the root cause and sequence of the incident. The first step was to ensure the security of the personnel, and to establish a restricted boundary around the other 7 new excitation transformers found in this power station. The second step was installing an arc protective blanket structure around these transformers to reduce the size of the boundaries. The methodology on the calculations for the boundary and arc protective blanket system will be explained.