Santo Domingo.-The total collapse of the National Interconnected Electrical System (SENI) on November 11, which caused a national blackouthad a specific origin: an incorrect manual maneuver during work to repair a detached insulator on a 138 kV line at the San Pedro de Macorís substation.
The official report delivered by the Coordinating Body (OC) establishes that the operational error caused a three-phase short circuit that immediately destabilized the network and activated cascade protections.
The brigade that intervened in the section was carrying out authorized corrective work, but the opening of the disconnector – under load – generated a severe failure that led to the tripping of lines and the sudden loss of generation in the Eastern zone. That initial outage removed about 575 megawatts from the system, more than the grid could support without losing stability.
As a result of the electric shock, the frequency dropped sharply and activated the Automatic Load Disconnection Scheme (EDAC)designed to defend the system in emergency cases. However, minutes later the frequency rose abruptly again before collapsing again, in a sequence that made any recovery impossible.
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The total blackout occurred just 110 seconds after the initial failure. The set of automatic trips in lines, plants and distribution circuits produced an irreversible chain that ended up completely turning off the SENI.
Technical revelations: protections that acted badly and unexpected shots
The report reveals incorrect actions in several key protections of the system. According to the OC’s analysis, multiple relays were triggered without the real conditions to do so, or they did so outside of their programmed times, aggravating the chain of events.
More serious cases include shootings on lines like Coastal–La Romana, Boca Chica–San Pedro, El Soco–Hato Mayor and San Pedro Bioenergy–SPMwhere some relays operated outside their protection zone.
The document also detected that in several fields the records were not synchronized with GPS, which made it impossible to accurately reconstruct the sequence of failures. This lack of synchronization compromises coordination between protections and makes post-event analysis difficult.
At the distribution level, the EDAC showed significant failures: some circuits opened when they did not correspond, while others did not act even though the frequency had fallen to levels that required immediate disconnection.
Cascade outage fueled by generation losses and coordination failures
The OC confirms that the unit trip Punta Catalina 2 and the disconnection of several solar and wind plants contributed decisively to the collapse.
More than a thousand megawatts of generation were out of service in the minutes following the initial failure, further compromising the system’s response capacity.
The thermal plants were also unable to adequately follow the automatic generation control commands, which reduced the SENI’s ability to correct frequency oscillations.
The combination of sudden losses, regulation failures and incorrect trips led to a widespread automatic disconnection that the system could not contain.
The restoration began with hydroelectric plants and internal combustion engines, followed by thermal plants ready to start. The progressive recovery allowed the entire SENI to be restored hours later.
Recommendations: urgent adjustments in protections, registration and operation
The report of the Coordinating Body contains 28 recommendations aimed at generators, distributors and the Dominican Electric Transmission Company, with emphasis on correcting critical vulnerabilities.
Priorities include reviewing and adjusting operating times of relays that acted inappropriately, correcting erroneous configurations, and ensuring GPS synchronization of all logs sent to the control center.
Another essential recommendation is to ensure that the circuits belonging to the EDAC are not opened during field work without replacing them with other equivalent ones, since this defense logic is vital to avoid major blackouts.
The agency also suggests incorporating battery energy storage systems to improve frequency regulation and facilitate autonomous starts in emergency situations, along with adjustments in protections that can disconnect multiple plants simultaneously in the event of severe failures.
