‘Auto shutdown’ of RLNG-based plants behind prolonged blackout

Report of Power Division says they parked themselves in 'island mode'

LAHORE: The recent power breakdown witnessed by the country last month proved damaging to the national transmission system. The Power Division discovered auto shutdown of the recently commissioned RLNG-based power plants as one of the reasons behind the prolonged blackout.

According to a report of the Power Division on the system breakdown of May 16, 2018, the recently installed RLNG-based power plants suddenly stopped power generation, when the transmission system was mid-way in recovery, following a fault in Guddu plant.

Instead of providing electricity generation at that crucial stage of recovery, the RLNG-based plants disconnected from the national grid and parked themselves to 'island mode'.



"Amid running of national grid on the edge due to high demand, a partial system breakdown was initiated by failure of shunt reactor at Guddu plant yard and system was split in north-south," said the report.

"Due to operations of under frequency relays in northern part, system got stabilised but then went into blackout due to early outage of recently commissioned RLNG power plants [Haveli Bahadur Shah and Bhikki power plants] in the centre region," the report added.

An official of the National Transmission and Despatch Company (NTDC) confirmed that RLNG-based power plants closed their operation. He added that the management of these plants has been asked to recalibrate auto-shutting system in order to avoid such situation.



Another official of the Power Division said that RLNG-based power projects have been set up keeping in view their ability to produce power with much reliability and ease. Similarly, he added, these state-of-the-art plants are readily available on short notice to inject power into national grid on very short notice.

However, it seems that the management of RLNG-based power plants are not paying any heed to demands to recalibrate auto shutdown features in a bid to cope with system fluctuations without stopping power generation.

A senior official associated with RLNG-based power plants said, on the condition of anonymity, that recalibration of RLNG plants is not an issue and the findings are incorrect. "All plants have protection built in and when the grid frequency fluctuates they are designed to automatically disconnect from the grid and go into island mode," he added.



This is not the case with Haveli Bahadur Shah power plant; other plants in the system also observe the same pattern. "The management of these plants will continue the same practice in the future to protect the plants and will not change, rather, the NTDC needs to fix their system issues otherwise this may continue in the future too," he added.

Besides overloaded electricity transmission and distribution system, varying power generation and unbalanced power input from the north has provoked power supply system during another breakdown recorded on May 21, 2018. This massive failure of power network started after outage of major 500/220kV auto-transformers at Rawat Grid Station.



This even followed by cascaded tripping as per protection schemes, saving sensitive power system equipment from damaging. The tripping occurred when Tarbela and Mangla hydel generation was low at that time and Nandipur power plant was on shutdown due to maintenance, which led to overloading of Rawat and resultant tripping.  After these incidents, the Power Division has increased the scrutiny at all key installations to control the overloading and any further possibility of major power failures.

Published in The Express Tribune, July 1^st, 2018.

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