Impact of Current Limiting Reactors Operated Together With a Fast Parallel Breaker on Substation Equipment

Traditionally Short Circuit (SC) control in HV substations is done by means of proper SC design in a grid. Nevertheless, due to growing power demand, additional generating units are connecting to the grid and also the grid configuration is changing over time. All these changes in the grid are increasing the SC levels and at some points the design levels may be exceeded. Ways to cope with rising fault levels can be splitting buses, increase SC capability of substation equipment or implement series reactors [3], [8]. The paper will specifically discuss about series reactors used together with a fast parallel breaker. Traditional SC Limiting Reactors are acting fully linear and are therefore not changing the typical SC-peak to symmetrical SC ratio of around 2.6. Due to the nonlinear impedance behavior of a SC Limiting Reactor together with a fast parallel breaker the ratio between peak SC and symmetrical SC current will significantly change. This is having a major impact on the forces inside of the equipment which connected in series with the concerned transmission line.