The National Grid Corporation of the Philippines (NGCP) sought holistic solutions and efficient coordination in the power supply chain to prevent the massive outage that hit Western Visayas on April 27 to 29, 2023.
The grid operator clarified that many factors came into play concerning the grid alerts and incidents that were widely publicized in the recent days.
The system disturbance and the widespread outages in Panay Island between April 27 and 29, and the red alert raised in the Luzon grid resulted from a confluence of events that support its call for better and proper power system planning across all 3 members of the energy supply chain: generation, transmission and distribution.
NGCP further explained that while there were grid incidents monitored in both the Luzon Red Alert on 08 May, as well as the Panay Island outages, these incidents by themselves, ought not to have caused the effects seen.
“In the case of Panay Island, NGCP’s protection systems, which were communicated and coordinated with its grid connected customers from both the generation and distribution sides, functioned as intended,” the company explained.
“As we explained to Congress yesterday, only the consumers connected to the line that tripped should have been disengaged from the grid. It was unfortunate that a power plant disengaged from the transmission system unexpectedly,” explained the company.
“This response from the generating unit is both unexpected and undesirable. The resulting undervoltage and underfrequency was severe and unrecoverable, and was the direct cause of the tripping of other power plants connected to the system, and ultimately, the Panay sub-grid collapse,” NGCP said.
The subsequent trippings that occurred on April28 and 29, 2023 were a direct result of the avoidable events of 27 April 2023.
With regard to the Luzon red alert on May 8 “it should have ended similarly, as there was an unexpected and undesired response from a generating plant which tipped the balance of supply and demand.”
TIMELINE
Details of loss of power in Panay April 27-29 based on information gathered from NGCP’s systems and field personnel, was traced to a fault that occurred along the Bacolod-Silay 69-kiloVolt (kV) line at 1:50PM April 27. This line is maintained and operated in part by Central Negros Electric Cooperative, Inc. (CENECO) and NGCP.
As a first response, NGCP conducted a line patrol of segment of the line, and assessed protection settings.
As previously announced to the public, they found no fault along the segment and protection systems functioned properly with the clearing of the fault at Bacolod Substation at 450ms, within the standards set by the Philippine Grid Code. This setting is coordinated with all grid connected customers on the supply and the distribution side. This means that clearing at 450ms should not cause any grid connected customers to trip.
Subsequently, Palm Concepcion Power Corporation (PCPC) in Iloilo province, with estimated generation load of 135MW, tripped 1.3 seconds after fault clearing. This response from the generating unit is both unexpected and undesirable. The resulting undervoltage and underfrequency was severe and unrecoverable, and was the direct cause of the tripping of other power plants connected to the system, and ultimately, the Panay sub-grid collapse.
There were contributing factors that made it difficult for Panay sub-grid to immediately recover after April 27 including:
- Unplanned outages and deration of other plants (outside of Grid Operating and Maintenance Program approved by the Department of Energy) – On April 27, 695MW was unavailable to the Visayas Grid due to unplanned maintenance shutdowns. Had there been sufficient generating sources on that day, the Panay sub-grid would have recovered from the undesired tripping of PCPC since there would have been sufficient voltage support coming from other functioning power plants within the Visayas system.
- Insufficient non-variable energy sources and unique configuration of the Negros-Panay sub-grid – When the Panay sub-grid collapsed, the configuration of the system leading to Panay made the latter dependent on variable energy sources in Negros. The variability of these sources made them unreliable in providing voltage support to Panay. Again, had there been sufficient non-variable sources available to the Panay sub-grid, the island would have sooner recovered from the events of April 27, 2023.
- Delay in the completion of the Cebu-Negros-Panay 230kV Backbone Project – had this project been completed on time, the line could have provided a more efficient delivery system to transport power to support the Panay sub-grid recovery by more efficiently delivering the needed voltage support from other plants in the Visayas Grid.
ASSURANCE
In a letter to Iloilo City Mayor Jerry Treñas, NGCP President and CEO Anthony L. Almeda said that “what happened to Panay last April 27 to 29 is both unfortunate and unacceptable, and everything must be done to prevent this from happening again.”
“As grid operator and from a transmission point of view, NGCP assures the City of Iloilo that we will exert all efforts and implement all necessary transmission solutions to prevent this from happening again. With respect to the other sectors comprising the energy supply chain, we ask that they do the same,” Almeda stressed.
“We ask for the cooperation of all members of the energy sector in making available, in a timely manner, all our respective records, settings, and protection systems so that we may find lasting solutions and provide you and your constituents with immediate and accurate information.
We ask for your continued support in the pursuit of our mandate. We remain committed to addressing all energy industry concerns, insofar as transmission is concerned, and continue to pledge our cooperation and devotion to finding holistic and long-term solutions,” said Almeda.
Moving forward, NGCP emphasizes the need for the following:
- Keep all transmission and distribution lines free from any obstruction which may affect the reliable flow of power in the transmission system.
- Review generator settings to ensure coordination with the transmission system by submitting their respective unit protection and control settings. Generators should ensure and demonstrate that these settings will not cause the degradation of the power grid to which they are connected.
- Improve generation planning to avoid heavy loading of lines and ensure sufficient generation per island, with a well-balanced mix of fuels and technology.
- Effective use of emerging technologies such as energy storage systems, among
others.
- Accelerate grid reinforcement projects with the support of national and local government and the public.
- Immediate, open, and transparent information exchange among all players in the energy supply chain.
- Review of the Philippine Grid Code to cater to variable renewable energy sources.
“In the case of Panay Island, NGCP’s protection systems, which were communicated and coordinated with its grid connected customers from both the generation and distribution sides, functioned as intended,” the company stated.
NGCP noted that prior to the occurrence of the faults, unplanned outages of plants and the deration of other plants contributed to the situation. These unplanned outages are outside of the Grid Operating and Maintenance Program planned well ahead and coordinated by NGCP with the power plants and approved by the Department of Energy.
On its part, NGCP commits to complete several large transmission projects within the next few months to help strengthen the transmission system and better support the power system.
“We continue to advocate for a holistic approach to power planning. Development in all sectors involved in the power industry must be coordinated, with due attention given to each. We support the Department of Energy in all its efforts, and we are confident of its continued support to all sectors,” the company said.
NGCP assured the public and its stakeholders that it is exerting all efforts to implement all necessary solutions to prevent any similar grid incident.
