Exclusive: A blow-by-blow account of Monday’s blackout

g natIonal transMIssIon and despatch coMpany has proVIded a suMMary oF What happened on MornIng oF 23rd January leadIng to a natIonal blackout proffit report

AhmAd AhmAdANi & AsAd ullAh KAmrAN on Monday, a catastrophic failure in the national grid caused the worst electrical outage in months across the country, crippling life and spotlighting the country’s ageing energy infrastructure. profit has obtained a report of the national transmissions and despatch company detailing how the blackout played out. the report, published on the 24th January explains the blackout. the company has conceded that the system protection mechanism in place did not prevent the cascade impact of tripping, which plunged the entire country into darkness on January 23. authorities began restoring electricity to millions of people late on the same night while an investigation was launched to determine the reasons for the outage. the blackout lasted more than 12 hours in the majority of the regions, while in some areas it lasted even longer.

The basics

When you turn on an appliance, such as your kettle or laptop charger, it is powered by alternating current. this indicates that the electricity alternates between positive and negative voltage. this back-and-forth motion, or “oscillation,” is referred to as electrical frequency. grid frequency, measured in hertz (hz), is a technical term that refers to the number of times the alternation cycle occurs every second. currently, 50 hz is the most prevalent frequency used in the bulk of the world’s power systems, including pakistan’s. because the equipment in your house, factory, or office is designed to run at 50 hz within a narrow tolerance, maintaining the frequency of our power supply is critical. this is the reason why everyone turns their appliances off when there’s a fluctuation in the voltage or frequency of electricity. If this isn’t done there’s a possibility of equipment and appliances being damaged. the issue is that frequency can be difficult to control; if the exact amount of electricity needed is not matched by generation, the frequency of the electricity on the grid can be affected. the report reads that, “system frequency [had] gone up to 50.75 hertz (hz) and severe hunting was observed… that caused load and voltage variation on transmission lines. as a result… transmission lines tripped which resulted in isolation of [the] north and south system followed by blocking of [the] hVdc (high Voltage direct current) system”. according to the initial statements by the minister of energy khurram datagir and the ministry, the system experienced a “loss of frequency that caused a major breakdown”. this seems to be inconsistent with the report of ntdc that categorically states that the frequency had gone up. n an interview, the minister of energy khurram dastagir explained what happened. “In winter, the demand for electricity reduces nationwide, hence, as an economic measure, we temporarily close down our power generation systems at night.” but when the power plants were restarted on the morning of January 23, “frequency variation and voltage fluctuation,” were discovered in southern pakistan, “somewhere between dadu and Jamshoro,” he said. consequently, this led to the “power generating units to shut down one by one.” this is wholly inconsistent with what the report of the ntdc states, fundamentally if there is more demand for electricity than supply, for example, frequency will reduce. When there is an excess of supply, frequency rises. now if we were to go by this understanding then the system tripped because there was an excess supply of electricity, and the claims of the minister that a “loss” of frequency caused the system to trip are incorrect. the report also breaks down the scale of the blackout, right prior to the incident the total generation stood at 11,356 megawatts(MW) and a frequency of 50.31 hz. at the time of the incident 23rd January at exactly 7:34 am the frequency spiked to 50.57 hz. this caused a chain reaction in which large 500 kv supply power cables tripped. the thing to point out here is the fact the frequency was operating on a higher level prior to the spike on the morning of the black out. this should’ve initially served as a warning to the regulators that supply exceeded the demand causing a rise in the frequency.

What happened?