HYDROELECTRIC POWER PLANTS CONTROL SUPERVISION TYPES BASIC INFORMATION

After the location and mode of control is defined, the manner in which the plant is supervised or staffed should be recognized. Though this aspect is not commonly addressed in industry recognized labels for plant control, the equipment selection and its degree of automation is related to the plant supervision.

The greater the degree of sophistication in the controls, the greater the distance between the equipment being controlled and the control location.

As the main point of control moves from the equipment to an off-site locale, the need for staffing/supervision at the lower levels of control diminishes. Supervision can, therefore, be described relative to the plant as either attended or unattended.

Attended

- The plant is staffed 24 hours a day. The operator is available to perform control actions either locally or at a centralized area.

Unattended

- The plant is not staffed for the full 24 hours a day. An operator may be present for a single shift or make a routine visit to the project. With the exception of small hydro, the policy throughout the industry is to have some form of supervision or monitoring at a given plant. If the plant’s on-site control is defined as unattended, then it is implied that the supervision/monitoring is performed off-site.

Unattended operation is represented by two predominant examples:

1) Off-Site Supervisory Control

- Here, control of the remote plant exists for all essential operations and a full complement of indications for the remote plant are brought to the off-site control location. Occasional visits by operation and maintenance people are made to ensure plant security.

2) Off-Site Monitored Control

- All of the controls for the plant are local. A minimum representation of plant indication is brought to an off-site location where full attendance exists. The capability exists at the off-site location to dispatch an operator to the plant if conditions warrant. Routine maintenance visitations can also be made to the plant.

The practice is to describe a control system by location and then mode. It can then be modified by defining the type of supervision. Since the staffing of a plant varies within the industry, it is difficult to define this aspect generically.

All combinations of location and mode are legitimate and more than one combination can exist at a plant. For example, a multiple unit plant can have local manual controls at the unit auxiliaries and the unit switchboard.

It can have a control room that would have both centralized manual and centralized automatic controls. It may even have equipment at the plant that would allow the capability of off-site automatic controls.

To complete the scenario, the plant may be unattended except for routine maintenance visits. A hierarchy of control can, therefore, be developed, going from those controls closest to the equipment and the least complex to the controls located off-site and the most sophisticated. Starting from the lowest (most basic) echelon in the hierarchy and working to the highest (most sophisticated), we find

1) Local manual

2) Local automatic

3) Centralized manual

4) Centralized automatic

5) Off-site manual

6) Off-site automatic

It should be kept in mind that the above combinations can further be modified/described by appending either attended or unattended to them.

WIND POWER ELECTRIC ENERGY BASIC INFORMATION

The wind is a free, clean, and inexhaustible energy source. It has served humankind well for many centuries by propelling ships and driving wind turbines to grind grain and pump water. Denmark was the first country to use wind for generation of electricity.

The Danes were using a 23-m diameter wind turbine in 1890 to generate electricity. By 1910, several hundred units with capacities of 5 to 25 kW were in operation in Denmark (Johnson, 1985). By about 1925, commercial wind-electric plants using two and three-bladed propellers appeared on the American market.

The most common brands were Wincharger (200 to 1200 W) and Jacobs (1.5 to 3 kW). These were used on farms to charge storage batteries which were then used to operate radios, lights, and small appliances with voltage ratings of 12, 32, or 110 volts.

A good selection of 32-VDC appliances was developed by the industry to meet this demand. In addition to home wind-electric generation, a number of utilities around the world have built larger wind turbines to supply power to their customers. The largest wind turbine built before the late 1970s was a 1250-kW machine built on Grandpa’s Knob, near Rutland, Vermont, in 1941.

This turbine, called the Smith-Putnam machine, had a tower that was 34 m high and a rotor 53 m in diameter. The rotor turned an ac synchronous generator that produced 1250 kW of electrical power at wind speeds above 13 m/s.

After World War II, we entered the era of cheap oil imported from the Middle East. Interest in wind energy died and companies making small turbines folded. The oil embargo of 1973 served as a wakeup call, and oil-importing nations around the world started looking at wind again. The two most important countries in wind power development since then have been the U.S. and Denmark (Brower et al., 1993).

The U.S. immediately started to develop utility-scale turbines. It was understood that large turbines had the potential for producing cheaper electricity than smaller turbines, so that was a reasonable decision. The strategy of getting large turbines in place was poorly chosen, however. The Department of Energy decided that only large aerospace companies had the manufacturing and engineering capability to build utility-scale turbines.

This meant that small companies with good ideas would not have the revenue stream necessary for survival. The problem with the aerospace firms was that they had no desire to manufacture utility-scale wind turbines.

They gladly took the government’s money to build test turbines, but when the money ran out, they were looking for other research projects. The government funded a number of test turbines, from the 100 kW MOD-0 to the 2500 kW MOD-2. These ran for brief periods of time, a few years at most. Once it was obvious that a particular design would never be cost competitive, the turbine was quickly salvaged.

Denmark, on the other hand, established a plan whereby a landowner could buy a turbine and sell the electricity to the local utility at a price where there was at least some hope of making money. The early turbines were larger than what a farmer would need for himself, but not what we would consider utility scale.

This provided a revenue stream for small companies. They could try new ideas and learn from their mistakes. Many people jumped into this new market. In 1986, there were 25 wind turbine manufacturers in Denmark. The Danish market gave them a base from which they could also sell to other countries.

It was said that Denmark led the world in exports of two products: wind turbines and butter cookies There has been consolidation in the Danish industry since 1986, but some of the companies have grown large. Vestas, for example, has more installed wind turbine capacity worldwide than any other manufacturer.

Prices have dropped substantially since 1973, as performance has improved. It is now commonplace for wind power plants (collections of utility-scale turbines) to be able to sell electricity for under four cents per kilowatt hour. Total installed worldwide capacity at the start of 1999 was almost 10,000 MW, according to the trade magazine Wind Power Monthly (1999).