Over-Voltage Prevention Solutions for 220 kV Distribution Substation to Enhance Power System Stability: A Case Study in Vietnamese Power System

This paper proposes the solutions to prevent over-voltage for the 220 kV distribution substations with several different voltage levels. The motivation comes from the failures of surge arrester number 2 of phase B at the transformer number 2 (CS2BAT2) of the Vietnamese 220 kV Thainguyen substation due to the over-voltage. The main objective is to enhance the operating stability of a scattered connected power network between substations. The Vietnamese 220 kV Thainguyen substation has the complexity structure, operates on three voltage levels of 220/110/35/22 kV, and connects the Chinese 220 kV Malutang. During the operating period, the operating voltage at the 220 kV bus is equal to 1.15 p.u.. This high voltage will put the transformer into magnetic saturation, so that the CS2BAT2 has been faced with serious failures. This paper proposes the solutions for preventing over-voltage located CS2BAT2 to enhance the Thainguyen substation stability. These proposed solutions are developed from the operating ideas based on the flexibility in instantaneously changing the system configuration. The effectiveness of the proposed solutions are confirmed by the simulation results based on (i) using Electromagnetic Transients Program-Restructured Version (EMTP-RV) to calculate and re-analyze the practical event at 0 : 12 AM on June 17, 2015, (ii) comparing the obtained results between the use of EMTP-RV and the recorded relay, on those bases to continue making other necessary case. It was observed that the proposed solutions could apply to immediately solve the difficulties encountering in the Vietnamese 220 kV Thainguyen substation.