On 30 May 2014, in evening hours, Northern Grid experienced a heavy demand crash from 4:00 pm to 7:00 pm due to rain, dust/thunder storm in Northern India. The demand started reducing at around 4:40 pm and was minimal at around 5:15 pm. The huge demand reduction resulted in a widespread high voltage throughout the system. The system frequency also touched a high of 50.65 Hz at 5:05 pm.
During this period 68 AC transmission lines along with one HVDC Bi-pole tripped. This incident led to load crash of about 8,000 mW in Northern Region, including 3,500 mW in Delhi. At around 1640hrs, the Northern Region demand started declining steadily at a rate of approximately 200 mW/min and reached to 32,780 mW at 1715hrs, around 8,000 mW less than that of the previous day Demand of same time. Delhi, UP, Haryana & Uttarakhand being the major State Control Areas in which this abrupt demand reduction was observed.
This demand reduction also resulted in high frequency and high voltage in the system.
As per IMD , continuous thunder and lightning, spell of heavy rain associated with wind (having speed more than 75KMPH) affected most part of the Northern States.
Based on the weather forecast received and NOWCAST of IMD around 4pm, all the constituents were alerted about the likelihood of the storm in Northern region.
Alert SMS were issued to all concerned States’ Load Despatch centres for backing down of generation in order to control high frequency operation besides containing over-voltages. The backing down of generation at Inter-State Generating stations (ISGS)/Regional Entity generators was carried out. Thus, backing down of the order of around 2,700 mW was achieved in Northern region. Generation was also reduced throughout the country to meet the exigencies.
All the constituents & generating stations cooperated to combat the situation real-time.
Out of 68 lines tripped during the incident, 49 lines have already been restored, including the HVDC line.
Supply has been restored gradually in all the states.
In Delhi, the restoration of lines was taken up on war footing level and top most priority was accorded for restoring power to emergency services such as Hospitals, Delhi Metro, water treatment plants and NDMC area. Presently, about 3,800 mW load is being met and the load restriction is only about 200 mW in Pappankala, Gopalpur & Rohini areas.
Two 765 kV and one 400kV lines where there has been extensive damage to towers are being restored by POWERGRID by 10 June, 2014. However, non-availability of these lines is not affecting the power supply to the states, as alternate paths are available.
Minister of State for Power (independent charge) Piyush Goyal reviewed the situation in the meeting held at 11 AM today which was attended by the Power Secretary & senior officers of ministry of power, chief secretary and senior officers of Government of NCT of Delhi, DTL, DISCOMs of Delhi, CEA, POWERGRID and POSOCO.
Officers of Delhi sought assistance from POWERGRID for ERS for early restoration of the following 220kV lines, which are affecting the power supply. Ministry of Power has assured all the possible help to Delhi in early restoration of the lines and directed the POWERGRID to extend all cooperation in this regard.
The minister also appreciated the efforts of all the officials of Ministry of Power, Load Despatch centres and Utilities, including Delhi, for timely action in combating the unexpected situation caused by the thunderstorm. He also suggested that a comprehensive plan be drawn up to meet such exigencies in future including procurement of more number of ERS sets which should be maintained by all the states and central utilities to reduce the outage time and ameliorate the suffering of the people.
It was also advised to chief secretary, Government of NCT of Delhi, to disseminate information to public via press releases, website and social media about the outages and likely time of interruptions to reduce the inconvenience to the public.