Electricidad de Caracas is finalizing installation of a fifth gas turbine unit at the OAM power plant in Venezuela. The project is one which began several years ago to enable the utility to meet peak demand while modernising its plant in preparation for a reforming market.

Electricidad de Caracas (EdC) is a private utility founded more than 100 years ago. With an installed thermal plant capacity of 2.3 GW, EdC is the main private generator. It is also the largest private distributor supplying most of Caracas’ power requirements, and has stakes in three small distribution companies. Notably, EdC also set up the first IPP project in Venezuela to supply power to two of the country’s largest refineries.


The OAM plant is on a small site high up on a mountain
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More recently, the utility has done a lot of work in preparing for forthcoming changes in the market. In an attempt to follow the same route as neighbouring countries like Colombia, Venezuela, after years of delays, finally announced a new electricity law in September last year. Part of EdC’s work has been focussed on increasing the efficiency of its installed plant. One plant which has undergone extensive work is the OAM project.

The OAM project name comes from one of the original founders of the company, Oscar Augusto Machado. The power plant is an old plant commissioned in 1969. It was initially a 70 MW plant, but between 1969 and 1978, its capacity was increased to 204 MW through the addition of a mixture of combustion turbines.

These additions included five 20 MW units supplied by Brown Boveri (later to become ABB and now ABB Alstom Power), two 22 MW units from Hitachi and one 60 MW aeroderivative unit from Worthington International. These units all ran on natural gas with fuel oil No. 2 kept as a backup.

Revamping OAM

In 1992, the utility took the decision to revamp the plant to improve the plant’s efficiency in order to ensure a reliable supply to Caracas. At the beginning of the project, EdC was also having problems evacuating the power from the OAM plant due to transmission grid constraints – the 69 kV grid could only handle the output of the old power plant. The project therefore also involved improving the transmission capabilities of the grid.

EdC decided to replace seven of its 20 MW units with four 100 MW turbines.

Initially, EdC put out an international bid on three of the combustion turbines. Siemens Westinghouse won the bid in what was the first phase of installing three 105 MW W501D-5 combustion turbines.

About a year after this first phase, a fourth 100 MW unit was purchased. This was also a 501D5 unit with an output of 105 MW under ISO conditions. This brought the capacity of the plant to 420 MW.

These four units continued to operate at the power plant alongside the aeroderivative unit (kept just for blackstart) until recently. In October 1998, Siemens Westinghouse received an order to replace this old blackstart unit with another new 501D. The new foundations have now been set to receive the new unit. The generator is on its way to the site and the turbine will arrive within the next couple of months.

The job is expected to be completed before the end of this year. This will bring the total capacity of the plant to just over 500 MW.

All this expansion work was carried out without taking the plant off line – a task which called for careful project management. Describing the expansion, Jesus Esteban of Siemens Westinghouse said: “The biggest challenge in building the plant was transportation. The gas turbines had to transported to the peak of the mountain and more than 90 bridges had to be reinforced. The size of the site was also a challenge and the engineers had very little space to work in.”

Operation

The plant operates in simple cycle mode and due to a lack of water and the size of the site, there are no plans to convert it to combined cycle.

EdC has other large thermal power plants which provide much of its baseload capacity. The OAM power plant is generally used as a backup and at times of peak demand. For example, during dry season the plant is fully operational with all of its units running.

However, the amount of units that are run largely depends on the availability of hydropower. There are large hydro dams in the south eastern part of Venezuela which produce about 10 000 MW. If the water level is high, EdC has certain agreements with the government whereby EdC shuts down its thermal units.

So while the OAM plant is part of the overall production system, EdC does not operate the plant if the cost of producing hydropower is low i.e. in the rainy season. Esteban commented: “Two weeks ago the plant was operating in standby mode with one unit kept as a backup in case something happens to another plant.” Accordingly the plant is designed to have the ability to startup rapidly.

Prior to installation of the fifth W510D-5, the plant was controlled by the Westinghouse WDPF control system. However, these were not Y2K ready. Part of the negotiations therefore called for the replacement of these control systems with the Westpac control system. The installation of the new control system was finished in June last year. The plant can now be operated by just 29 staff.

Exporting power

The new law covers a number of issues, one of which is the extension of services to isolated areas. The government, which has the responsibility for planning power sector activities, will formulate the National Electricity Service Plan. This plan will cover sector policies, forecast future power demand, estimate new generation capacity requirements, the portfolio of investment projects and transmission expansion requirements.

EdC has enough capacity installed to supply power to greater Venezuela and also to export to other areas of Venezuela. With the new electricity bill coming into effect, EDC is planning to put new capacity in place to allow it to be a leading exporter of electricity.

The company has already started the ball rolling and plans to put out an international bid at the end of April/May for new efficient combined cycle power plants.