State the necessity of reactive power compensation equipment. List out the devices used for reactive power compensation and give application of each device.
Necessity of reactive power compensation equipment :
i. Due to reduction in reactive power flow there is reduction in tr. Line current & reduction in line losses. So to improve the performance efficiency of system improves power transmission becomes more economical.
ii. Due to reduction in line losses heating of line reduces thereby ageing of insulation reduces & life of equipments, cable or line increases.
iii. Wear – tear of the switchgear equipment reduces due to reduction in operation.
iv. By local provision of reactive power KVA load on the line reduces and hence additional load can be connected or additional power can be transmitted without any additional generating equipment or resource. That means loading capacity of line/generator increases. So to main balance in Qs & Qr reactive power compensation is required
Or
Most of the power system components are to be operated with voltage profile of 15%. But during power transfer a voltage drop of less than 10% occurs which is due to flow of reactive power. Moreover reactive currents contribute for I2R losses in the system.
ii. Most of the loads absorb lagging Vars to supply the magnetizing current of equipment such as transformers, induction motors etc. At any moment the maximum Vars which can be transferred over the line are fixed by voltage profile.
iii. At peak loads the Vars demanded by the loads greatly exceeds Vars which can be transmitted over the lines. Flow of reactive power through the line causes voltage drop in the line and varies the voltage profile at important buses. Therefore additional equipment is necessary to generate lagging Vars at load centers to meet the reactive power requirements.
iv. At light loads the lagging Vars produced by the lines are much larger than required by load. This surplus lagging Vars must be absorbed by additional equipment to keep voltage profile within limits. If it is not done the system voltage at some of the buses is likely to become higher then nominal value.
Devices for reactive power compensation
1. Shunt compensation equipments - Shunt reactor , shunt capacitor& static var system
2. Series compensation equipments - Series reactors
3. Synchronous compensation equipments - Synchronous condenser