Reduction of high-frequency transient overvoltages in power stations with generator circuit-breakers

Today the use of generator circuit-breakers installed between a generator and the associated step-up transformer is widespread because this offers many advantages with respect to the unit connection (i.e. an arrangement without a generator circuit-breaker) such as simplified operational procedures and better protection of power station equipment against the fault effects. The insertion of a switching device in the connection between generator and step-up transformer exerts an influence on the type and magnitude of overvoltages that will occur. Thereby special consideration has to be given to the possibility of overvoltages being generated by the generator circuit-breaker itself during switching operations and by its sole presence while being in the open state. Those overvoltages are associated to electromagnetic fields which might interfere with surrounding equipment. The present paper specifically investigates the possible generation of those overvoltages. In order to make a thorough analysis the impact of capacitors installed at the terminals of the generator circuit-breakers is investigated.