In a modern power system, electrical energy from the generating station is delivered to the ultimate consumers through a network of transmission and distribution. For satisfactory operation of motors, lamps and other loads, it is desirable that consumers are supplied with substantially constant voltage. Too wide variations of voltage may cause erratic operation or even malfunctioning of consumers’ appliances. To safeguard the interest of the consumers, the government has enacted a law in this regard. The statutory limit of voltage variation is ± 6% of declared voltage at consumers’ terminals. The principal cause of voltage variation at consumer’s premises is the change in load on the supply system. When the load on the system increases, the voltage at the consumer’s terminals falls due to the increased voltage drop in (i) alternator synchronous impedance (ii) transmission line (iii) transformer impedance (iv) feeders and (v) distributors. The reverse would happen should the load on the system decrease. These voltage variations are undesirable and must be kept within the prescribed limits (i.e. ± 6% of the declared voltage). This is achieved by installing voltage regulating equipment at suitable places in the power system.

Learning Objectives:

• To understand importance of voltage control
  
• To know different methods and location of voltage control
  
• To familiarize with voltage control methods used at generation, transmission and distribution level
  

Lecture Contents:

• Importance of Voltage Control
  
• Location of Voltage Control Equipment
  
• Methods of Voltage Control 
• Excitation Control (i) Tirril Regulator and (ii) Brown-Boveri Regulator
  
• Tap-Changing Transformers
  
• Auto-Transformer Tap-changing
  
• Booster Transformer
  
• Induction Regulators
  
• Voltage Control by Synchronous Condenser