Simulation model for assessing transient performance of capacitive voltage transformers

In determining the correct operation of relays of a protection scheme, proper representation of instrument transformers and their behavior in conditions where there can be transient is very critical. This paper presents a simulation model for assessing the transient performance of capacitive voltage transformers (CVTs). In order to test the validity of the developed model, four CVT operational conditions are considered using field data collected from one of the Nigerian electric utility 330/132/33 kV substations. The model simulation results revealed various configuration performance responses that could affect relay protection schemes to different degrees. As expected, the CVT responses showed that faults initiated at zero voltage crossing, which is the worst transient condition, produced transient voltage magnitude up to 40% of the nominal voltage while faults initiated at the crest produced minimum transient voltage magnitude. It is shown that the model developed for the selected instrument transformer yielded satisfactory results