‘The entire episode, from the triggering of the event by the fallen Palmiste tree on the 12KV distribution line to the shutdown of the entire grid resulting in an island-wide blackout, spanned about 3.6 seconds.’ – Marvin Gonzales
By Sue-Ann Wayow
A ROTTEN, fallen tree in South Trinidad was the reason Trinidad was plunged into darkness for almost 13 hours on February 16.
It would take just over three seconds from the tree falling on an electrical line to trigger the blackout which the Trinidad and Tobago Electricity Commission (T&TEC) scrambled to fix.
This is according to the report submitted by the Committee mandated to investigate the islandwide power outage in Trinidad. Tobago was not affected.
The findings of the report were read in Parliament on Friday by Public Utilities Minister Marvin Gonzales.
He thanked the committee for their “diligence, patriotism, and professionalism” in preparing the comprehensive report and assured citizens that the recommendations made would form part of a programme of work in the electricity sector in the short and medium-term.
On February 16, at approximately 12.52 pm there was a failure of the entire electricity grid in Trinidad, causing no electricity on the island for some 12 and a half hours, with initial restoration at 6. 50 pm and the final customers supply returning at 1.34 am the following day.
In response to the outage, a three-member committee was established by the Government to investigate, among other matters, the circumstances which gave rise to the failure of the electricity supply system, the process for restoring power supply, and the status of physical security of T&TEC’s facilities, and to make recommendations to avoid a recurrence of a nationwide power outage.
The committee headed by retired Professor of Electrical and Computer Engineering UWI Professor Chandrabhan Sharma included former chairman of T&TEC Keith Sirju and acting Superintendent of the Trinidad and Tobago Police Service (TTPS) Allister Guevarro.
The committee was given a period of one month from its date of appointment – by March 22 to report its findings and report to the Office of the Prime Minister and was allowed to co-opt any other expertise and resources that it required.
On April 5, the committee completed its investigations and submitted a report to Prime Minister Dr Keith Rowley.
It reported that, at the time of the incident, the three Independent Power Producers (IPPs) were supplying some 1,130 MW of electricity to T&TEC for distribution to its customers in Trinidad, from their four power stations:
- Trinidad Generation Unlimited (TGU) – La Brea at 537 MW (47.5%);
- PowerGen – Point Lisas at 472 Megawatt (MW);
- Penal at 50 MW (46.2%); and
- Trinity Power Limited – Point Lisas at 71 MW (6.3%).
Gonzales said, “The committee noted that the country’s electricity network is a robust one with reasonable redundancy and generally well-operated and that no electricity grid is without risk or immune to failure. The cause of the island-wide blackout according to the report of the committee, on Wednesday February 16, 2022, a 21.64 m tall fungal affected Palmiste tree fell in the vicinity of Grants Trace, Extension Road and the NGC private Road in Rousillac.”
He said, “The said tree fell onto a single-phase T&TEC 12 KV distribution line. At the time of the occurrence of this trigger incident, the country was under a High Wind Yellow Alert issued by the Meteorological Office. Madam Speaker, I wish to confirm that the Committee unequivocally stated that it did not find any evidence of sabotage as the trigger for the failure.”
According to the report submitted, first, the Palmiste tree eventually fell off the 12 KV line causing the line to sag, oscillate and upswing, and to come into contact with the 220KV line circuit, which transmits most of the power from the TGU generating facility to T&TEC.
The 12 KV line crosses orthogonally under the 220 KV transmission by a distance of over four metres, which is more than two times the minimum stipulated by international standards.
Secondly, the fault occasioned by the two lines accidentally coming into contact with each other caused the protection relays on the two circuits on the 220 KV transmission line to trip sequentially and become de-energised thereby isolating the TGU plant from the grid, the report stated.
Thirdly, the de-energizing of the 220 KV transmission line, created a large imbalance between available running generation supply (537 MW) and load (68.75 MW) resulting in a very rapid increase in generation speeds at the TGU plant, as the essentially unloaded turbines accelerated. The turbines immediately tripped on over speed protection, disconnecting all generators at TGU thereby resulting in a 47% loss of generating capacity.
Fourthly, the sudden loss of 47% of generating capacity on the grid was too fast for the system’s circuit breakers to shed load to match the available generation. In the circumstances, the other IPPs experienced underspeed and under-frequency conditions which exceeded their stability limits leading to a cascading outage and the collapse of the entire electricity grid, first at the Point Lisas plants and then at Penal.
Gonzales said, “Madam Speaker, the entire episode, from the triggering of the event by the fallen Palmiste tree on the 12KV distribution line to the shutdown of the entire grid resulting in an island-wide blackout, spanned about 3.6 seconds. Given the speed at which the events unfolded, the Committee concluded that there was no time for human intervention.”
Fifthly, in the sequence of events was that in the response, the report acknowledged that the safe and timely re-establishment of power on the island following a total shutdown as what occurred on the Wednesday, was a complex and critical task which required close coordination between T&TEC and the IPPs, and should be based on well documented and tested black start procedures.
Such re-starts must be done under the direction and supervision of T&TEC. The Report noted that three of the four power plants in Trinidad had black start capabilities on the day, and that within one hour of the outage, all three generation plants operated by TGU, and Power Gen, following their procedures, attempted starting their black start units.
However, there were multiple failed attempts occasioned by: the lack of preparedness among the agencies (IPPs and T&TEC) for such an eventuality, the unavailability of black start units, inadequate technical capacity for dealing with such a situation; and the absence of a documented power system restoration plan governing the sequencing procedure(s) to be followed after a total loss of power on the island.
Power was eventually restored at 6.50 pm to Penal and from there the rest of the power system was re-energized.
And according to the report, several of the problems encountered in restarting the plants were evident in 2013 when the system suffered a similar collapse.
Assessment of response and recommendations
Gonzales stated that the Committee identified several weaknesses in the management of the response.
These include:
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Ineffective communication with the public, with heavy reliance on the internet and social media which was negatively impacted by the blackout;
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The absence of the involvement of the Office of Disaster Preparedness and Management;
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The lack of a systematic approach in the restoration process which led to many unforced errors in the re-energisation process; and
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The Committee was also of the opinion that no single person took on the role of Incident Commander and had overall authority, as well as detailed knowledge of the restoration process.
“At the same time, the committee recognised the initiative of the Protective Services to trigger a commendable response in the circumstances,” Gonzales said.
He added, “The committee has made several recommendations to address the weaknesses identified, as well as, to improve the resilience of the electricity grid and to reduce the country’s vulnerabilities to the recurrence of such an incident.”
One of the key recommendations to improve security, reliability and efficiency of the transmission grid is the construction of another 220 KV circuit from the Union Sub-Station to the Gandhi Sub-Station and construction of this second line was already at an advanced stage with completion scheduled for the first quarter of Fiscal 2023, the minister stated.
“The need to ensure that this was not another lost opportunity for distilling valuable lessons of experience and building resilience into the system was underscored,” Gonzales said.
He said, “The IPPs and T&TEC staff did make unforced errors in the reenergization process. This can be easily remedied by ensuring that the operators are schooled in the understanding of the issues involved in a de-energized grid and the safe process to re-energize the grid.”
Key recommendations
The Committee in its report made the following recommendations:
1) Additional training of operational staff of the IPPs and T&TEC specific to the recovery of the grid from a total blackout;
2) Establishment of clear documented procedures related to the complete recovery of the grid from a total blackout;
3) Categorisation of the total blackout as a National Disaster thereby automatically fully engaging the ODPM in the process;
4) Establishment of the Manager System Control and Generation interface as the Incident Commander in future;
5) Construction of additional Transmission infrastructure to further strengthen the grid with priority on the completion of the second 220kV line as soon as possible; and
6) An annual independent power system resilience review and power system risk assessment should be performed to identify power system vulnerabilities that can lead to catastrophic power system failures. This should be reviewed by an independent technical standing committee;
Gonzales requested that the report be sent for further examination by the Committee on Public Administration and Appropriations of the Parliament.
