Methodology to Prevent Voltage Collapse During On Load Tap Changing Transformer Operation Under Network Contingencies

The operation of On Load Tap Changing Transformer (OLTC) in a normal state can maintain the desired voltage but can also increase the risk of a voltage collapse under certain operating conditions like network contingencies such as outage of a transmission line. Hence, OLTC operation can be both a boon and a curse in voltage control based on the operating condition of the power system. This paper is investigated the effect of the tap changes in the voltage instability process under network contingencies. For this sake, instability may be obtained as a consequence of a network contingency. This paper also discusses the reverse action that the secondary voltage of a transformer is pulled down when the tap position of OLTC is raised to increase the secondary voltage under network contingencies. The performance of the reversal OLTC with the placement of the FACTS device Static VAR Compensator (SVC) at the critical load bus is also investigated. The proposed methodology has been effectively tested on an EHV 24 bus equivalent southern region of an Indian power system network.