Technical Audit of Sarfaraznagar 220kV Grid Station

Commissioned in 1995, the station has a total transformation capacity of 480MVA and feeds the industrial area on Multan road and the rapidly developing residential area in the suburbs of southern Lahore. The station is equipped with three 160MVA-220/132kV autotransformers, one 40MVA-132/11kV, and one 26MVA-132/11kV power transformers, all owned and maintained by the National Transmission and Despatch Company (NTDC). The grid station is linked to New Kot Lakhpat (NKLP) 220kV Grid Station and Yousafwala 500kV Grid Station through 220kV transmission circuits, which is an important link between southern and northern parts of Punjab. A new Okara 220kV Grid Station is under commissioning and will be linked via the two 220kV Sarfaraznagar-Yousafwala circuits. The grid station's switchyard is equipped with a one-and-a-half breaker scheme for the 220kV switchyard and a double bus single breaker scheme for the 132kV switchyard. A technical audit of the grid station was conducted by the USAID Energy Policy Program from January 8, 2014, to January 17, 2014. The audit team, comprising transmission and protection experts, identified several key findings and recommendations for improvement. The audit revealed that the 220/132kV transformers are loaded above the prescribed limits per NEPRA grid code clause OC 4.9.5, supported by IEC (International Electrotechnical Commission) standards. This excessive loading reduces the expected useful life of the transformers in proportion to the amount and duration of overload. The audit also identified several maintenance-related issues, including the pending major maintenance of six 220kV and nine 132kV circuit breakers due to unavailability of spare parts. Additionally, the audit found that several tests required for grid system operation and maintenance, such as leakage current monitor (LCM) tests of lightning arresters and capacitance and dissipation factor (C&DF) tests of current transformers (CTs), potential transformers (PTs), and capacitor voltage transformers (CVTs, are not being performed. Furthermore, the audit revealed that two sets of 220V DC batteries are in critical condition and require immediate replacement. The audit also identified several protection-related issues, including the absence of tele-protection (carrier-aided) tripping facility on almost all 220kV lines and the inoperative sequence event recorder (SER) and disturbance fault recorders for the 220kV system. Based on the findings, the audit team made several recommendations for improvement, including conducting proper load flow studies to ensure that the 220/132kV transformers are not overloaded, arranging spare parts for twelve 220kV and twelve 132kV circuit breakers, and performing LCM tests of lightning arresters and C&DF tests of CTs, PTs, and CVTs. The audit team also recommended replacing old electromechanical over-excitation relays with latest numerical relays, installing tie line stub protection, synchro-check relays, and distance to fault locators on all 220kV transmission circuits, and making the SCADA system functional.