Technical Audit of Daharki 220kV Grid Station

Commissioned on June 24, 2009, the station has a total transformation capacity of 410MVA and feeds a major portion of Sadiqabad and its surrounding areas. It is an important grid due to its direct linkage to three power generating stations, including Engro Power Plant (217MW), Foundation Power Plant (175MW), and JDW Power House (26MW). The technical audit of the Daharki 220kV Grid Station was conducted by the USAID Energy Policy Program in January 2015. The audit team, comprising transmission and protection experts, visited the station from December 2, 2014, to December 5, 2014. The findings of the audit are presented in the report, which highlights several areas of concern that require immediate attention. The audit report identifies several issues related to the loading condition of transformers, tap changer operation, and metering system. The loading condition of both 220/132kV transformers is normal, but exceeding the 80% loading limit can reduce the expected useful life of transformers. The tap changer for transformer T-1 is operated manually, whereas remote operation is an international standard. Additionally, no dedicated current transformers (CTs) and potential transformers (PTs) are installed for the secure metering system (SMS). The report also highlights issues related to isolator and circuit breaker operation. Four 220kV and seven 132kV isolators are operated manually, and two 220kV isolators are operated locally in the switchyard. Moreover, one 132kV circuit breaker is operated locally, and major maintenance of four 220kV and four 132kV circuit breakers will become due in the near future. The audit report also identifies several issues related to protection and control systems. Tele-protection and direct transfer trip (DTT) on the 220kV system are inoperative, and sequential event recorders, fault recorders, and voltage/power recorders are not installed at the grid station. The absence of HV connection, LV connection, and rough balance differential relays on transformers T-1, cross trip scheme on both 220/132kV transformers, and thermal overload protection relays on 220/132kV transformers are also highlighted. The report provides recommendations for addressing the identified issues. These include installing dedicated CTs and PTs for the secure metering system, performing regular tests for dissolved gas analysis and detailed oil testing of transformers, leakage current measurement (LCM) test of lightning arrestors, and capacitance & dissipation factor (C&DF) test of CTs, PTs, and capacitor voltage transformers (CVTs). Additionally, remote operation of tap changer, circuit breaker, and isolator should be made functional, and spare parts should be procured for major maintenance of circuit breakers. The implementation of these recommendations is crucial to ensure the reliable operation of the Daharki 220kV Grid Station and to prevent potential power outages and equipment damage.