Dec. 3 blackout: Committee recommends police probe
A committee that investigated the total blackout on December 3 has recommended a formal investigation by law enforcement agencies and independent IT experts after the Ceylon Electricity Board (CEB) offered no “definitive proof ” to support its explanation for the failure’s root cause.
The committee also examined the blackout that took place November 29, 2021, because of similarities between the two.
The seven-member committee “has not found sufficient grounds to completely eliminate the allegation that the incidents on December 03 and November 29, 2021, could have been pre-planned, or caused by deliberate action…”, its final report, presented on Monday to the Power Ministry Secretary, said.
This is because the material presented to the committee by relevant branches of the CEB “could not explain some key events such as the erroneous operation of end-fault protection and wrong configuration of line protection relay of the Kotmale-Biyagama 220 kV transmission line”.
The total collapse of December 3 was triggered by circuit 1 of the KotmaleBiyagama 220 kV transmission wire tripping a full 22.33 seconds even after the fault in circuit 2 (which was the initial glitch) had stabilised within 288 milliseconds and the system returned to normal.
Written and oral explanations by CEB officials pointed to the possible cause in both cases as being “an earth fault in a single phase”. But they could not offer “definitive proof ”.
Data logs showed that the initial fault event causing high neutral current on phase B on circuit 2 lasted only 288 milliseconds, after which the neutral current returned to zero. At that point, the defective line had been disconnected from both ends and the fault isolated. The remaining line (circuit 1) then carried the full load as expected.
But circuit 1 tripped 22.33 seconds after the initial fault. “So the key question becomes what caused the protection system to issue this trip signal after 22.33 seconds from the initial fault when the neutral current had already normalized,” said a power systems engineer, who did not wish to be named.
The committee has not accepted CEB’s explanation that this unexpected trip signal was issued because of a faulty wiring of the protection relay.
“The single-line fault may have been a natural cause,” the committee states. “Further, the unintended operation of endfault protection of busbar protection at Biyagama may have been the result of faulty wiring that existed for many years, as may have been the wrong configuration of the line protection relay of circuit 1.”
“However, before arriving at this conclusion definitively, the committee needs to eliminate the possibility of human intervention of deliberate action in any one of the three events— earth fault on phase B of circuit 2, alleged faulty wiring of busbar protection system of Biyagama GS, and wrong configuration of line protection relay (main 1) of circuit 1 of the Kotmale-Biyagama 220 kV Transmission line,” it holds.
“We recommend a formal investigation by the law enforcement authorities assisted by independent IT experts to determine whether or not any human intervention has taken place,” it urges.
In the case of the November 29 blackout, the committee found that the same erroneous trip signal had been responsible for many parts of the country losing power several hours. It contends that, had CEB engineers, had investigated this earlier partial failure and taken corrective action immediately, the blackout that happened four days later could have been avoided.
The December 3 power outage caused serious damage to Unit 3 of the Lakvijaya coal power plant (LVPP). It was off-grid for seven days owing to the “system disturbance” and was switched off again on December 21 to fix a generator seal oil leak.
The committee also questions why it took so long to restore auxiliary power to Lakvijaya after the total blackout of December 3 which caused an uncontrolled complete shutdown of all three units.
Lags also took place at other locations. The committee calls for an internal CEB investigation to find the “exact causes of delays in the restoration at each point identified and rectify them immediately”.
“Call explanations from everyone who held responsibilities at installations where those delays occurred and take necessary actions if the investigations reveal that the staff had not performed adequately to ensure safe and fast restoration of the system,” it states.