ISLAMABAD: The National Electric Power Regulatory Authority (Nepra) has exonerated the Water and Power Development Authority (Wapda) of any fault in the delayed restoration of the national power system following the countrywide blackout on January 23, 2023.
According to Nepra’s report, the total power system collapse occurred on January 23, 2023, at 07:34:43:800 hours, plunging the entire country into darkness. Full restoration was achieved on January 24, 2023, after almost 20 hours. As the sector regulator, Nepra took immediate notice of the incident and constituted an Inquiry Committee (IC) to investigate.
During the inquiry, the committee visited powerhouses, grid stations, sites, offices, and reviewed relevant documents.
Country hit by major power outage
The IC noted that the black-start facility at Tarbela Power Station was activated, and generating Unit No. 3 was synchronized at 08:10 hours. Power supply to several grid stations in the Islamabad Electric Supply Company (IESCO) area—particularly Islamabad and Rawalpindi—was restored gradually. However, NPCC reported that Tarbela’s generating units remained unstable, resulting in wide frequency swings between 45 and 55 Hz and causing tripping of generators at 09:10 hours.
The inquiry found that nine similar startup attempts were made from Tarbela using different combinations of transmission lines and area loads, but all failed. The island could neither expand nor synchronize with Mangla. According to NPCC, the AGL diesel generator sets also failed to synchronize due to the instability caused by Tarbela’s fluctuating units. Tarbela management maintained that the variations in load created stress that triggered frequency fluctuations, ultimately leading to machine tripping.
The committee also observed that Mangla Power Station had been instructed to perform a black start; however, it could not initiate operations due to the unavailability of water discharge permission from IRSA (zero cusecs indent). Once clearance was granted, Mangla synchronized Unit No. 1 at the 132 kV Busbar and restored its auxiliary supply via the 132 kV Mirpur circuit at 10:10 hours.
In its explanation to Nepra, Wapda stated that Tarbela’s black-start facility was used promptly, with Unit 3 synchronized at 08:10 hours—37 minutes after the collapse—and Unit 2 at 08:52 hours. Warsak Units 6, 3, and 4 were synchronized at 08:13, 08:17, and 08:18 hours respectively, in line with NPCC instructions. Wapda said that after energizing the 220 kV Burhan circuits at 09:10 hours, Tarbela units experienced strong frequency fluctuations (45–55 Hz).
Subsequent restoration attempts failed due to significant load variations causing abnormal frequency swings. Units tripped on ROCOF protection while operating in island mode.
Copyright Business Recorder, 2025
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