A fungus-affected Palmiste tree which fell on a T&TEC 12-kilovolt line in Rousillac on February 16 knocked out Trinidad’s entire electricity system in 3.6 seconds, causing a 12-hour blackout.
This was indicated yesterday by Public Utilities Minister Marvin Gonzales in Parliament on the findings of the Cabinet-appointed expert committee on the investigation.
There was a failure of the entire electricity grid in Trinidad, from 12.52 pm lasting 12 and a half hours.
The team, chaired by retired UWI Professor of Electrical and Computer Engineering, Prof Chandrabhan Sharma, included former T&TEC chairman Keith Sirju and Acting Superintendent Allister Guevarro.
Their report was submitted to the Prime Minister April 5.
Gonzales said the report concluded the blackout had “laid bare the many shortcomings in disaster preparedness and restoration procedures.”
But the committee stated it did not find any evidence of sabotage as the trigger for the failure.
At the time of the incident, three independent power producers (IPP), Trinidad Generation Unlimited, PowerGen and Trinity Power Limited were supplying 1,130 megawatts of electricity to T&TEC for Trinidad customers.
The committee noted T&T’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.”
But Gonzales added, “According to the committee’s report, on Wednesday, February 16, a 21.64m tall fungal affected Palmiste tree fell in the vicinity of Grants Trace Extension Road and the NGC private Road in Rousillac.”
“The said the 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.”
The sequence of consequential events recorded by the Committee was as follows:
• The Palmiste tree eventually fell off the 12 KV line causing the line to sag, oscillate and upswing, and 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 (4) metres, which is more than two times the minimum stipulated by international standards.
• 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 de-energising 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 Trinidad Generation Unlimited (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 per cent loss of generating capacity.
• The sudden loss of 47 per cent 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 under-speed 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 added, “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 islandwide blackout, spanned about 3.6 seconds.
“Given the speed at which events unfolded, the Committee concluded there was no time for human intervention.”
