An independent inquiry committee has found serious violations of safety and security protocols and severe deficiencies in the country’s power system operations starting from generation facilities both in public and private sector to the entire transmission network including the K-Electric (KE) that resulted in a prolonged power breakdown early last month.
The 24-page inquiry report “Total Power System Collapse on January 9, 2021” of the three-member independent inquiry committee appointed by the National Electric Power Regulatory Authority (Nepra) also observed that “black start operations at most of the power plants were non-existent or non-functional which should have restored the power supply quite quickly in the country”.
The committee comprising Nepra Director General Nadir Ali Khoso and former senior officials of National Transmission & Despatch Company (NTDC) Khalid Mahmood and Manu Ram also deplored that ‘recommendations of inquiry reports of past power breakdowns were not or partially implemented, otherwise the magnitude of collapse could have been averted’.
The report said seven officials of the Guddu Power Plant were rightly suspended as the breakdown was triggered at its switchyard for lack of safety protocols, but held that the management was also responsible for lack of supervision. The report also blamed NTDC, KE and majority of the public and private sector power plant operators for poor performance.
Serious safety, security violations in KE, power plants highlighted
The report said the fault was caused by gross negligence of Guddu Power Plant staff who operated the 220kV circuit breaker without opening the earth switch of the 220kV isolator and that too without the permission of National Power Control Center (NPCC). Unfortunately, not only the breaker failed to trip but the breaker’s frequency scheme also did not operate.
As a result, cascade tripping occurred due to bolted fault which divided the power system in South and North zones.
Generation, load gap
Consequently, there was sufficient unbalance between the generation and the load. In the South zone including KE, there was more generation as compared to load, which at first experienced tripping due to over voltage or over speed or over frequency and consequently on under frequency. The power system of North zone tripped on under frequency condition where the generation was too less against the load.
It said the System Operator (NTDC) together with the power plants took around 20 hours and KE took about 22 hours for complete restoration of the power supply in their respective jurisdictions. The restoration was much higher and lapses were observed on the part of power plants which despite prior notice by NPCC failed to restart and synchronize their all units with the system in specified time.
It said the was the obligation of System Operators of both NTDC and KE to establish contingency plans and SOPs for system recovery following the total and/or partial shutdown but no such document was produced to the inquiry committee. “Hence, NTDC, KE together with concerned power plants are responsible for delay in complete restoration of power system”.
The review of the previous reports revealed that the recommendations had either been partially complied with or still in progress or pending.
Some technical deficiencies also included no interlocking arrangement among the isolators and circuit breakers, symbols of earth switches installed with isolators neither shown in single line diagram nor marked on mimic diagram in the control room and there were no proper preventive maintenance of switchyard equipment. This can cause a major mishap.
The report said no periodical testing of relays and other switchyard equipment were done, testing of equipment was inadequate, switchyard equipment were in poor condition and no routine check of control and protection schemes were done. On top of that, unawareness of even implementation of settings was noted.
There was no centralised event recorder available with NPCC, so the sequence of tripping of transmission lines and machines in the power system could not be ascertained precisely. Also, the distance relays in the system had operated randomly which was undesirable.
The report said most of the power plants were without black start facility except Tarbela, Mangla, Warsak and Uch Power.
