REŠENJE ZA UNAPREĐENJE SISTEMA ZEMLJOSPOJNOG PREKIDAČA

In the area of the former "Elektrovojvodina", in transformer station 110/20 kV, the ground switch circuit break system was installed as a forced solution until the old low-oil circuit breakers, which have far exceeded their service life, are replaced. This system "extinguished" any transient earth fault by short-term grounding of the phase affected by the fault, without the need to disconnect the feeder on which the fault occurred. After the replacement of worn-out switches with new ones, this system continued to work because extremely high success rate in resolving transient faults, and absence of interruptions at the low voltage level. The main problem of this system that we have faced during exploitation is the jamming of the pole in the first version of the ground switch or the loss of vacuum in circuit breaker chamber, in the newer version of the ground switch. When these events occur, the entire electrical supply system to which the ground switch is connected fails. Detection of its failure is extremely complex. Namely, the ground switch, apparently, works correctly: he is still trying to solve the ground fault he himself caused. This problem was solved by connecting the ground switch system to the MV bus via a feeder cell that was used only for that purpose. That cell was fully equipped with a switch, disconnectors, current measuring transformers and a protective device. The main disadvantage of this solution is, beside the questionable economic justification, taking the place of a one feeder. In this paper, we present the solution implemented in TS 110/20 kV Apatin. Namely, we used the existing automation device and the existing cell of the ground switch, in which we added a fourth pole in serial with three poles, between the poles and the ground. This pole is permanently switched on and remotely controlled, and which, in the event of a fault, is set to disconnect the poles and grounding, blocks the automation and sends an alarm to the dispatch center that the ground switch is faulty. In this way, we prevented the outage of the power supply of large amount of consumers, reduced the failure diagnostics time to zero and increased the reliability of the power supply of all consumers supplied from the given transformer area.