Types of reactive power compensation



Types of reactive power compensation Reactive power level of motors, generators and a plant network as a whole is characterized by the consumer power factor. It is defined as the ratio of the active power consumption to the total power has been actually taken from the network. The closer the value to one, the smaller the share of the reactive power taken from the network. For example, the induction motor coefficient is about 0.7, the coefficient of electric arc furnaces and welding transformers is about 0.4, the coefficient of machine tools and machinery does not exceed 0.5. Thus, full utilization of network capacity is possible only if reactive component of the power is compensated. It should be observed that generally it is not recommended to entirely compensate reactive power (up to cos phi equals 1), as this may lead to overcompensation due to variable active load power and other random factors. They usually try to achieve a value of 0.9. The reactive power can be compensated by synchronous compensators, synchronous motors or capacitor banks. Capacitor banks have recently been widely used for reactive power compensation. They have a number of advantages over other devices for reactive power compensation. Reactive power compensation can be an individual, i.e. local, and centralized, i.e. general. In the first case one or more cosine capacitors are connected in parallel with the load. In the second case a number of capacitors are connected to the main switchboard. Individual compensation is the easiest and most inexpensive way to compensate reactive power. The number of capacitors or capacitor banks corresponds to the number of loads. Each capacitor is located directly at the respective load (e.g. near the engine). Such compensation is suitable only for constant loads (e.g., one or more induction motors with constant speed of the shaft rotation), i.e. where the reactive power of each load changes only slightly over time and to compensate it no change in the rated value of the connected capacitor banks is required. Therefore, due to the constant level of reactive power load and the corresponding reactive power of the compensators individual compensation is also called uncontrolled. Centralized compensation is a reactive power compensation carried out by an adjustable installation for reactive power compensation connected to the main switchboard. It is used in systems where there are a lot of consumers with a large spread of power factor during the …


Post time: Jan-08-2018
WhatsApp Online Chat !