2008-01-03 - CFE, Mexico’s power utility, expects that blackouts caused by earthquake damage in the coastal resort of Manzanillo will become a thing of a past after installing compact switching equipment from ABB at one of its biggest power stations.
By
ABB Communications
The decision to invest in switchgear enclosed in a gas-filled metal casing came after a powerful tremor in January 2003 toppled outdoor equipment, sending razor-sharp fragments of porcelain insulation flying across the compound. The remnants can still be seen there today.
Nobody was hurt, but the 1,700 megawatt (MW) power plant, which supplies about 6 percent of the country’s electricity, was shut for six weeks. An even more costly stoppage lasting 14 weeks occurred in 1995, when the switchgear was devastated in a similar quake. Switchgear is a key component of substations, where electric voltage is switched and regulated.
Manzanillo, on the Pacific coast, is at the juncture of three tectonic plates. Steel brackets and girders provide additional support in the event of an earthquake.|
“This new installation is built to withstand earthquakes so it will have paid for itself as soon as the next strong tremor comes,” said Jesus Martinez Villareal, CFE’s head of power transmission in western Mexico. “Its contribution to the reliability of electricity supplies is a key benefit of gas-insulated switchgear but there are other key advantages.”
Two power plants operate at Manzanillo and one of them still uses air-insulated switchgear. Martinez said the advantages of gas-insulated equipment at the site are such that the remaining outdoor switchgear will be replaced, possibly as soon as 2008. The additional benefits include:
- Safety: Corrosion from the salt in the sea air and pollution from the oil-fired power plants next to the substation increase the risk of flashovers. To remove the salt and particles, the air-insulated switchgear must be washed daily, a dangerous operation as power at 400 kilovolts (kV) continues to flow through the installation. In an earthquake, falling equipment and breaking porcelain pose additional risks.
- Reduced maintenance: Gas-insulated switchgear is virtually maintenance free. Only the gas pressure needs to be monitored regularly by reading gauges fitted to the equipment. Meanwhile, six people are needed to clean the air-insulated switchgear every day.
- More compact: the gas-insulated switchgear at Manzanillo occupies just 20 percent of the space previously used by the air-insulated equipment. The new switchgear frees up so much land that CFE will be able to build an additional six generators at the plant once the remaining outdoor switchgear has gone, more than doubling capacity to 3,500 MW.
Removing the remaining air-insulated switchgear will free up so much land that CFE will be able to add six new generators and more than double capacity to 3,500 MW.|
Proximity to the sea, which provides the plant with cooling water and easy access to deliveries of oil, are advantages that outweigh the risks of the location’s seismic activity. Manzanillo sits on the Pacific coast, near the juncture of three tectonic plates.
ABB’s gas-insulated switchgear is not only designed and tested for earthquake resistance, it has also proven itself in the field. An installation at a CFE plant in Petacalco was undamaged after a quake in 2003 measuring 7.6 on the Richter scale. The tremors that damaged the air-insulated switchgear in Manzanillo reached 7.6 and 8.1 on the scale.
“Gas-insulated switchgear is very compact and has a much lower center of gravity than air-insulated switchgear. That means it is less likely to topple when the earth shakes,” said Mauricio Gonzalez, an engineer for ABB’s Power Systems division in Mexico.
Best layout
Financial and technical criteria determined CFE’s decision to award the contract to ABB, Martinez said. ABB proposed the best layout, providing flexible and simple control as well as accessibility should repairs or maintenance be needed, he added.
The installation includes Latin America’s first 400 kV air-to-cable bushing, where electricity from an overhead power line leaving the plant is fed into a cable that runs underground to the gas-insulated switchgear.
At the other end, a gas-to-air bushing links the gas- and air-insulated switchgear so that power can flow freely to where demand is highest. ABB was responsible for the design, manufacture and erection of the installation.
The Manzanillo facility is equipped with 10 bays of gas-insulated switchgear, each one being able to switch on or off a high-voltage power line. ABB has supplied more than 3,000 bays of gas-insulated switchgear worldwide since 1967.