ISLAMABAD: The National Electric Power Regulatory Authority (NEPRA) has unfolded a 34-page inquiry report about a countrywide power breakdown on January 23, 2023, holding six entities mainly responsible for the blackout.
The authority held the National Transmission and Despatch Company (NTDC), National Power Control Center (NPCC), GENCO-III, Guddu Thermal Power Station, and Port Qasim Electric Power Company (PQEPC) responsible for the breakdown.
NEPRA also accounted K-Electric (KE) as responsible for the failure to remain in island mode due to the tripping of Bin Qasim Power station—III.
The report said the wind generation curtailment lifted at 07:30hrs., and as a result about 500 megawatts generation injected in the system, which caused overloading of transmission lines as well as low voltage under steady state conditions in view of long AC corridor of about 1100KM, from Thar in South to Haveli Bahadur Shah in North with the insufficient generation, as the Guddu 747 Plant was under forced shutdown. It reduced the transmission line capacity in light of Surge Impedance Level (SIL).
Consequently, apart from rising trend in system frequency due to increase in wind generation, the oscillations on the system also started. At the same time the generation in the Northern region was reduced by shutdown of one unit and ramping down the generation of another unit of Ghazi Brotha at about 07:32:22.187hrs. That action aggravated the situation as the system was already weak and under stress due to high AC flow and low voltage/less VAR compensation in the middle, according to the report.
The delay in the restoration of the NTDC system was mainly due to failed attempts of black start facilities at WAPDA hydel stations and KAPCO. Other factors included a delay in synchronisation of various power plants and the non-availability of the SCADA (supervisory control and data acquisition) system in NPCC. The KE system was also delayed due to repeated failed attempts on black start.
The report mentioned that nine attempts were initiated from Tarbela to energize the system with different combinations of transmission lines and different area loads, but all attempts failed and the island could not expand and could not synchronise with Mangla.
The attempts were also made from the Warsak and Mangla hydropower plants, but no success was achieved. The back start facilities at all power plants were found highly questionable except the black start capability of the UCH-I power complex. The black start facility at the UCH-1 power plant was availed to energize the system.
The lack of SCADA and remote operations has a significant impact on the restoration process of the power system. SCADA is an essential tool that allows the system operator to monitor all system parameters which helps the system operator in expediting the action. Equally important is the sequence of events, especially related to equipment, of the complete network, which presently are not
available, and can be recorded at NPCC only through SCADA, according to the report.
Earlier, an 18-page inquiry report of the four-member committee headed by State Minister Musadik Masood Malik had already been submitted to PM Shehbaz Sharif. However, the regulator’s report tabulated 15 sequences of events that took place during the occurrence of blackouts and 18 remedial measures to avert future blackouts.
NEPRA had constituted 6 member inquiry committee comprising Imran Kazi, senior advisor, M&E, NEPRA convener, Nadir Ali Khoso, market expert member, Ghulam Abbas Memon, market expert member, Syed Safeer Hussain, market expert member, Manu Ram market expert co-opt member, and Syed Aqib Ali Shah, deputy director, M&E, NEPRA secretary.