LAHORE: The electricity transmission system which split into North and South due to tripping on Wednesday at 9:28 a.m resulting in electricity supply failure to Punjab and KPK areas was restored at 5:30 pm ( almost 8 hours) with major power generation plants gradually increasing their input in the national grid.
According to the initial report the 500 kV transmission line Guddu 747-Raheem Yar Khan tripped at 09:28:11 Hrs and at the same time 500 kV Guddu-DG Khan transmission line also tripped. As a result, the load increased on 500 kV Guddu-Muzaffargarh transmission line from 733 MW/ 72 MVAR to 1559 MW/ 717 MVAR as recorded at 500 kV Muzaffargarh end. This line also tripped at 09:28:14 Hrs.
This tripping resulted in under frequency on system from 50.18 Hz to 48.755 Hz within 5 seconds. Resultantly under frequency schemes came in action and frequency again improved from 48.755 Hz to 49.43 Hz at 09:28:38 Hrs. Meanwhile some other power stations also tripped perhaps due to frequency fluctuation/ jerk and cascade tripping started in the northern part from Guddu to Peshawar.