CANE POINTS: Manual Load Dropping and other Causes of Brownouts

Last week, Negros Power was at the receiving end of consumer complaints when the National Grid Corporation of the Philippines (NGCP) implemented Manual Load Dropping (MLD) among electric cooperatives (EC) and distribution utilities (DU) in the Visayas Grid.

For most consumers, the EC or the DU is the face of the power industry, because it is with the EC/DU that they interact – from applying for electric service connection, receiving the monthly bill and paying for the electric bill. This belief leads some consumers to blame the EC/DU whenever there are power interruptions or brownouts.

In reality, the EC/DU is not the only player in the power industry. The power industry is composed of the generating companies (GenCos), the transmission company (NGCP), the retail distributors (ECs & DUs), the Wholesale Electricity Spot Market (WESM) and the indispensable government.

The GenCos produce power either from traditional sources, such as coal, bunker, diesel and gas, or from renewable sources, such as solar, wind, hydro and geothermal. The NGCP serves as the highway through which power passes from the power plants of the GenCos to the ECs/DUs, who then deliver this power to the individual consumer’s residence or place of business.

The WESM is the marketplace where ECs and DUs make spot purchases of power, particularly during peak demand hours, when the demand or power requirements of their respective consumers exceed the contracted power capacity of the EC or DU.

As to the government, it does what government usually does in every aspect of the people’s daily life – that is, collect money from the people thru taxes on the consumer’s monthly electric bill. To appear useful, government sometimes issues rules and regulations for other industry players to follow.

This multi-player set-up dictates that each player has to function properly so that electric power can flow smoothly and continuously from the power plant to the consumer’s house or business. If one of the players underperforms, then power supply is affected.

The ECs and DUs have their fair share of power interruptions, mainly due to poor line maintenance and force majeure. In the case of Negros Power, it has committed to invest more than PhP2 billion over five years since August 2024 to upgrade and modernize its power distribution infrastructure.

From upgrading of substations, replacement of bare wires with insulated wires, upsizing of distribution transformers to the installation of fault detection and protective equipment, Negros Power implemented what it committed, resulting to the reduction in less than two years of both the frequency and the duration of DU-related power interruptions.

Of course, there are also natural calamities, such as typhoons which struck Negros last year and the earthquakes in Cebu and more recently in Mindanao, which cause power interruptions. There’s nothing an EC or DU, or even the almighty government, can do about these calamities, except to work like hell towards immediate power restoration.

Power interruptions can also be traced to problems in the transmission system operated by NGCP. When NGCP’s transmission towers are damaged by a wayward truck or tractor in the farms where these towers are often located, the lines will trip and power will be cut off. Such will also happen when large kites get entangled in the transmission lines.

When some portions of the transmission system experience trouble, the power is rerouted to other unaffected portions of the system. However, only a definite volume of power can be carried by the system, such that not 100% of the required power may be rerouted, leading to insufficient power to some areas of the grid.

Sometimes, the NGCP also conducts line maintenance, vegetation clearing and replacement of protective equipment and other power transmission devices. Since it is almost suicidal to perform this live wire maintenance, power has to be cut off to allow NGCP personnel to work safely. Often, it is the EC/DU which gets blamed for these power interruption, although the EC/DU has nothing to do about the cause of the brownout.

Another source of power interruption is from the GenCo side.

If one Genco suffers an operational breakdown, then the amount of power it can produce is affected. Depending on the nature of the breakdown, the ailing power plant can either produce no power at all, or it can function at a lower capacity and produce only limited power (not 100 % of its capacity). This reduction in power supply affects the grid. If several GenCos simultaneously breakdown, it can cause widespread forced power interruptions.

This is exactly what happened last week, when the NGCP implemented Manual Load Dropping in the Visayas Grid. With numerous power plants undergoing forced outage and many more power plants running below 100% capacity, there simply was not enough power to supply the demand. Thus, NGCP implemented scheduled rotational forced power interruptions among the ECs and DUs in Negros, Panay, Cebu and Bohol Islands.

The next time there is a power interruption, investigate first what its direct cause is. Understanding the roles of the different players in the power industry is much better than simply cursing a single entity.

Discernment is much more civilized than blind anger.* (BB)