ECONOMYNEXT – An expert committee that probed a 2020 cascading failure of Sri Lanka’s power grid has made 11 recommendations in an interim report.
The committee found that there was no operations manual on risk management relating to repairs and maintenance after an accidental short circuit by a power superintendent during routine maintenance of the high tension transmission system led to a blackout.
The blackout was compounded by repeated failures while trying to restore power, involving failures relating to hydro plants in Victoria and Kotmale reservoirs as well as mismatches in load, which the system control was apparently not able to see.
The unanticipated drop in demand could have come from solar power or inaccurate assessment of the load in the distribution network at that particular time which the system control directly measure.
“The committee recommends investigating better means of using past daily loading records of the feeders to predict more accurate load demands,” the report said.
“This would drastically reduce the time to bring the complete transmission network back to normal operation.”
The committee also recommended that the 2018 long term power generation plan be implemented which had the correct blend of technologies for future requirements and system stability.
“The committee strongly recommends implementing the 2018-2037 CEB Long Term Generation Expansion Plan, as given in the plan, which clearly specifies the correct blend of technologies for the future requirements of the Sri Lankan power system to improve the system stability and
reliability,” the report said.
It also recommended the building of 70 to 100 MW gas turbines which is a ‘black start’.
The report was not signed by Damitha Kumarasinghe, the Director General of the Public Utilities Commission of Sri Lanka.
He was also not present at the release of the report to the media.
Key recommendations and conclusions of the report are reproduced below:
Interim Report of the Committee on the incident of the Nationwide Electricity Supply Interruption on 17th Aug 2020 21
Recommendations for remedial measures that need to be taken by the CEB to prevent such
incidents in the future. :
1. The committee strongly recommends a standard compliant, systematic, foolproof, safe
procedures and maintenance protocols to be instated in CEB during operation and maintenance.
The implementation of these procedures will have to be continuously monitored and supervised
by adequately qualified, professionally trained, knowledgeable, experienced, and skilled
personnel. The committee would like to propose a performance evaluating annual appraisal
system which will help to improve the above attributes of the CEB staff.
2. The committee understands that there is no Operations & Maintenance related risk management
mechanism in place. Therefore it is recommended to establish a risk management mechanism in
order to determine the proper mix of preventive measures, mitigation levels, shift or retention of
risks and consequent level of robustness of Operations & Maintenance protocols that would.
indicate the positive impact on the overall system.
3. The committee strongly recommends to implement the 2018-2037 CEB Long Term Generation
Expansion Plan, as given in the plan, which clearly specifies the correct blend of technologies for
the future requirements of the Sri Lankan power system to improve the system stability and
4. The committee recommends to review the existing protection strategy for frequency instability.
5. The committee recommends to study the protection arrangement in detail in the Fast Cut Back
operation to see whether there can be an alternative protection arrangement which could be
derived not solely from df/dt limit but df/dt limit together with some other parameters.
6. Cost of unserved energy will have phenomenal economic impact to the country. Apart from its
direct impact, power interruptions of current nature will create adverse impacts to the investment
climate of the country.
7. The committee recommends to investigate better means of using past daily loading records of
the feeders to predict more accurate load demands. This would drastically reduce the time to
bring the complete transmission network back to normal operation.
8. The committee recommends to study the governors in the Kothmale Power Station and see if the
damping can be improved in the frequency control loop.
9. The committee recommends that staff involved in the control centres of the power plants used
to bring back the transmission network as well as the system control centre of CEB, gets more
professional training to become experts in their duties and to be proficient to follow and execute
the restoration manual to the best.
10. The committee recommends to install and commission 70 to 100 MW gas turbines with the
following capabilities: frequency control, black start, operating at sufficient leading and lagging
power factors, stability at small loads such as 1 MW, line charging for capacitive loads, compliance
with Sri Lankan grid code.
11. The committee recommends to use the existing dynamic transmission system model to perform
dynamic response analysis on the reported case.
1. The key reason for the nationwide power interruption on the 17″ August 2020 is due to the 3
Phase to Ground busbar fault due to incorrect operation of the Bus Bar 2 isolator of the Bus
Coupler Bay by the Electrical Superintendent — in Charge at the Kerawalapitiya Grid Substation
busbar 2 at 12:30:27.172 Hrs.
2. Kerawalapitiya Grid substation tripping was due to not following the correct maintenance
procedure by the relevant officials including the Electrical Superintendent. The committee also
observed that there is no written maintenance protocol for this maintenance job inline with the
current best practiced maintenance protocols.
3. The committee is on the view that due to the Kerawalapitiya Grid substation tripping, the
system frequency has increased beyond the current setting of the rate of frequency tripping
relay of the Lak Vijaya Power Station. As a result, the generator-transformer circuits breakers of
all three units of the LVPS which made LVPS unavailable to the grid, subsequently the system
failed in cascade.
4. The restoration of the Transmission network took 6 hours and 16 minutes, due to faults in the
units, generation — dispatch mismatches during black start and system frequency oscillations
during energizing the 220 kV and 132 kV systems.
5. CEBs recent failure to avoid a country-wide blackout and the longer duration taken to restore
power to Colombo City in particular, indicates significant lapses in implementation of critical
measures outlined in the previous Expert Committee Reports.