Shock to the system - JPS prelim report highlights series of triggers for June 5 all-island blackout

A preliminary report from the Jamaica Public Service (JPS) has revealed that its Hunts Bay-Rockfort line failed to isolate lightning-induced faults during adverse weather conditions last week, triggering a disastrous all-island blackout from Friday into Saturday.

The 38-page report, released yesterday, said the island had 635.9 megawatts (MW) of electricity, while the actual demand from customers was 544.3 MW, leaving a comfortable safety margin, or spinning reserve, of 91.6 MW.

However, it said although the grid was functioning normally, heavy rain, lightning and lingering Sahara dust had already caused several temporary power trips in the hours leading up to the main failure on June 5 at 9:02 p.m.

In addition to that, it said some transmission lines were still out of service from past damage caused by Hurricane Melissa in October last year.

Further, lightning is believed to have caused two separate electrical faults on critical power lines and infrastructure at the Rockfort substation and the Hunts Bay-to-Rockfort transmission line.

A third fault immediately followed on the Hunts Bay-to-Port Authority line, the report said.

Physical checks later revealed a damaged insulator, a broken wire conductor, and evidence of electrical arcing.

That was compounded by JPS’s safety systems failure known as protective relays.

Protective relays are critical electrical devices designed to detect abnormal grid conditions, such as overcurrents, faults, or voltage drops, and instantly trigger circuit breakers to isolate the affected section.

The report said the safety system at the Hunts Bay corridor “delayed or failed” to respond properly. This allowed the electrical problem to last too long and spread across the entire network.

A generator at the Jamaica Private Power Company plant tripped first, followed quickly by units at Hunts Bay, west Kingston, and other plants across Jamaica.

The sudden loss of massive amounts of electricity created a severe imbalance, the report said.

Automatic emergency backup plans (underfrequency load-shedding) tried to drop blocks of customers to save the grid, but the power generation dropped too fast for the system to recover, causing a total system collapse.

“The resulting rapid loss of generation created a severe generation-load imbalance, triggering all five automatic underfrequency load-shedding stages, zero through four. Despite the operation of these schemes, the magnitude and speed of generation loss exceeded the system’s ability to stabilise,” the report said.

It said this led to continued generator trips at Excelerate Energy, South Jamaica Power Company, Roaring River, Bogue, and Rio Bueno, and a complete shutdown of the interconnected system, resulting in an all-island outage.

Following the shutdown, the report said the power company activated its Incident Command structure and commenced restoration using a controlled black-start and system build-up approach, initially isolating the affected Corporate Area assets.

This meant that the light and power company restarted the grid from scratch using the step-by-step method. Instead of turning the whole island on at once, JPS said it built separate power “islands”.

Power reportedly returned to western Jamaica at 10:01 p.m., approximately one hour after the islandwide blackout.

JPS said central Jamaica had power at 10:18 p.m.

However, at 11:54 p.m., the report said while engineers were performing a delicate balancing act to match power supply with usage, the central and Corporate Area power networks crashed again, causing a brief delay, though the western network remained safely powered.

The report said the company regained momentum, and by 3:14 a.m., its experts successfully linked the western and eastern power networks together, making the grid highly stable.

From there, power was restored, and the islandwide grid was back to normal by 6:34 a.m. on June 6, 2026.

“The preliminary findings indicate that the grid shutdown was initiated by the loss of multiple transmission lines at a time when there was heavy rain and lightning. Additionally, initial investigations suggest a possible misoperation of the primary protection scheme associated with the Hunts Bay-Rockfort 69kV line. It is noted that this particular scheme operated correctly multiple times in the adverse weather conditions prior to the event,” the preliminary report said.

“These factors collectively contributed to prolonged fault conditions, cascading generator trips, and ultimately system-wide instability and shutdown. Despite the event and our initial investigations, there are no immediate concerns for grid stability following this event and the operational measures taken,” it added.

The company said it is replacing damaged insulators and broken wires found after the severe weather. It also said it took the problematic Hunts Bay-Rockfort power line temporarily out of service to comprehensively inspect its safety equipment and fix the delayed response problem.

Added to that, it said it is running a deep data analysis to pinpoint the exact root cause of the safety mechanism delay and is preparing a final formal report for the Office of Utilities Regulation.

Meanwhile, Energy Minister Daryl Vaz told Parliament on Wednesday that the Government is addressing major shortcomings in the current JPS licence, including high costs, poor resilience, slow renewable integration, and a lack of competition.

To reform the sector and prevent a continued monopoly, Vaz said a two-track approach has been adopted: first, negotiating a new licence aligned with national energy goals; and second, preparing alternative ownership arrangements if negotiations fail.

He said a multi-sector Electricity Licence Negotiation Team is guiding ongoing discussions and that a Green Paper is on track for a July completion, ensuring future terms prioritise clear performance standards and consumer protection.

He condemned the recurring system failure as “unacceptable”.

“While the report outlines the sequence of events that led to the system shutdown, I must emphasise that the root cause of the outage has not yet been conclusively determined. Investigations and technical analyses remain ongoing to establish, with certainty, the factors that triggered the collapse of the national grid,” said Vaz.

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kimone.francis@gleanerjm.com