Because of the high impedance of test transformer

test voltage increase may occur in test duty 3 of bus-charging currents switching by disconnector

and a voltage increase limit of 10% is required by related standards. In order to meet the above test requirement

the reasons of voltage increase in test duty 3 are analysed

and both shunt capacitor test circuit and shunt inductor test circuit are studied by EMTP-ATP simulation in this paper. The simulation results show that: by selecting an appropriate shunt capacitor value and working on two suitable points on both sides of power frequency series resonance point before and after the connection of the load capacitor

shunt capacitor test circuit can meet the requirement of standards

but with a higher output current of test transformer. Take the advantage of the infinite impedance of power frequency parallel resonance occurring between shunt inductor and load capacitor

shunt inductor test circuit can limit voltage increasing

but close synchronism must be satisfied.