The needs and requirements of traditional power systems

This chapter introduces the needs and requirements of traditional power systems

This chapter introduces the needs and requirements of traditional power systems.
In the traditional power system, relatively few centralized power plants provide power to a large number of consumption points through the transmission and distribution system. The transmission and distribution system uses several voltage levels of lines and equipment to affect the production of electric energy. Economic transport from land to consumption area. The following are some of the needs and requirements of traditional power systems.


⑴ Geographical diffusion of consumption points
The points of consumption are scattered across a large geographic area. Power users are sometimes very close, but they are usually scattered. Large-scale urban utility systems may have to deliver power to 200,000 different locations spread over 5,000 square miles (Figure ). The power system must set up a line to each user to establish a line network that connects all power users in a wide area.

The maximum value of a city in the winter of 2011 is 3442MW
The maximum value of a city in the winter of 2011 is 3442MW,The shaded part indicates the relative load density, and the lines indicate main roads and highways.

Figure This map shows a city where the highest demand is close to 3,500 MW. The entire city is powered by only 8 power stations. The job of the power transmission and distribution system is to transmit power from these 8 power stations to 385,000 energy demand points in the entire region.


⑵Low voltage (supply voltage) power demand
What has been needed until now has been low-voltage (supply voltage) electricity. The ready-to-use requirement for power transmission means that the power must have a stable voltage, that is, a relatively low voltage. More than 90% of the electricity consumed in most power systems is provided by the lowest power supply voltage — 100V (line-to-ground) in Japan, 120V or 240V (line-to-ground) in the United States, and 250V (line-to-ground) in the United Kingdom and Europe land). Most household appliances and commercial equipment are designed based on this voltage. Excessive voltage is impractical, uneconomical or unsafe in building wiring.


⑶ Real-time power transmission
Electricity must be delivered to appliances and equipment at the moment of consumption. One reality that power system designers have to face is that electricity cannot be stored efficiently or economically. Electricity must be “used immediately” and delivered to all points of consumption at the moment of use. This situation changed in the early 21st century. One can discuss whether modern batteries and energy storage technologies are “efficient and economical.” In some cases, a positive commercial container can be made for use as an energy storage unit, but in more cases, it is currently impossible to make a container. This is one of the reasons why the distributed power system concept works well and is sufficient as a viable alternative to more traditional designs, while other concepts are not.


⑷Reliability
The reliability of the service must be significant. Generally, the annual power outage time does not exceed 2h (availability 99.98%) as a reasonable proportion of power supply. Many power companies strive to limit the outage time of ordinary users to no more than 1 hour per year.


⑸Economy
Although the power system accumulatively spends billions of dollars, it provides thousands of kilowatt-hours of electricity to millions of users every year. The unit cost of electricity delivered in a reliable and ready-to-use form is quite economical in many parts of the world: this is the main reason why electricity is widely used.


⑹Safety
Security is an important factor. Electrical equipment can cause harm to power users, innocent bystanders, especially those who operate and maintain the equipment.


⑺Ease of use
Ease of use of electric energy was regarded as a major market factor by the pioneers of electric power companies in the 19th and early 20th centuries. This means that users do not need to participate in any form of management and operation of the power system. They only need to decide to use electrical energy and pay for it, without having to do anything else. Once “blind simplicity” is established, the electricity used by ordinary private house owners and businesses will become an important factor, which is often ignored after popularization. In the early 21st century, this has again become a major consideration for intelligent distributed power systems: no matter what advantages they provide, private house owners or small businessmen cannot be required to participate in the operation, otherwise it will complicate the simple use process. This proved to be an important factor and will be discussed later.


⑻Fairness and price subsidies
Issues of fairness and price subsidies often indicate policies at all levels of government and enterprises, as well as democratic views on the use of electricity. It makes the economy prosper and the quality of life improves, so system design, operation and price policy must provide basic access for everyone, which is the minimum requirement. These considerations often form conditions and restrictions to a large extent, under these conditions and restrictions, utilities and users must operate in the same way.


⑼ Environmental and aesthetic issues
Environmental and aesthetic issues occasionally dominate the local decision-making of power system construction and often become part of government policy. The establishment of any system has “side effects”, and the power system is no exception. Electricity production also has emissions or environmental issues. Transmission and distribution equipment is unattractive and takes up space in most cases. Everyone wants to enjoy the benefits of electricity, and does not want to suffer from the pollution and other side effects of electricity production caused by large-scale transmission and distribution systems, or aesthetic and “social adaptation” issues, but sometimes it is difficult to achieve a balance. Distributed power systems cannot eliminate these concerns, but they have different characteristics and interactions, so they can use unique features to adapt to specific situations. These features make distributed power systems one more solution to local balance needs.
The above are the needs and requirements of the traditional power systems, which may be one of the reasons driving its popularity in the future.

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