Northern Grid frequency statistics for Tuesday afternoon suggest that the grid frequency from noon to 1pm hovered close to 50 hertz (Hz) as against the admissible frequency of 49.5 hertz. The grid crash occurred at 1.10pm, when the frequency was 50.19 Hz.
Statistics from the Haryana state load despatch centre indicate that there was no overdrawal of energy between noon and 1pm by the state. The grid frequency was 50.27 Hz at noon, 49.99 Hz at 12.15pm, 50.23 Hz at 12.30pm, 49.92 Hz at 12.45pm and 50.19 Hz at 1pm.
"No caution message or message intimating violation of the grid code was issued by the Northern Regional Load Despatch Centre (NRLDC)," said a power official.
Power utilities officials said overdrawal was a frequent occurrence, but the NRLDC had a system in place to check and maintain safety of the grid.
"The cause of the July 30 and 31 grid crash is not overdrawal. On July 30, when the grid collapsed (2.35am), the frequency was 50.46 Hz at 2.32am. This has been recorded in the flash report of the Power System Operation Corporation (POSOCO)," said a top power official.
CERC issues summons to five states
The Central Electricity Regulatory Commission (CERC), on a petition filed by the NRLDC, has issued notices to five states for failing to comply with provisions of the grid code regarding maintenance of the required grid frequency.
The CERC has ordered officers of power utilities of Punjab, Haryana, UP, Uttarakhand and J&K to appear before the commission on August 14. The NRLDC had sought directions to the northern region constituents to curb power overdrawal from the grid and maintenance of safety and security of the grid.
It had quoted caution messages issued to the constituent states in terms of the Indian Electricity Grid Code (IGEC).
For instance, between June 1 and 30, a caution message in line with clause 6.4.7 of the IGEC – called A type messages - were issued to Haryana on 114 occasions, Punjab (98 times), UP(110 times), Uttarakhand (58) and J&K (40). Similarly, messages intimating violation of clause 5.4.2 of IGEC – called B type messages - were issued to Haryana (125 times), Punjab (96), UP (195), Uttarakhand (69) and J&K (60).
As per clause 6.4.7 of IGEC, the state load despatch centres (SLDC) or distribution licencee will have to restrict the net drawal of the state from the grid to within the drawal schedules, whenever the system frequency is below 49.7 Hz.
The distribution licencee/SLDC has to ensure that their automatic demand management scheme does not allow overdrawal when the frequency is 49.5 Hz or below. If the automatic demand management scheme has not yet been commissioned, then action has to be taken as per manual demand management scheme to ensure zero overdrawal when frequency is 49.5 Hz or below.
Meanwhile, the CERC said, "In our order dated July 10, we had directed that it would be the personal responsibility of the officers in overall charge of the state utilities/state load dispatch centres to ensure compliance of our direction (on not overdrawing electricity)."
"Since the situation has not improved despite our directions, we direct the officers in charge of the state utilities/state load dispatch centres of UP, Haryana, Punjab, Uttarakhand and J&K to appear before the commission on August 14," the CERC said in the July 30 order.