Table of Contents
How is switching voltage controlled?
The over voltages due to switching and power frequency may be controlled by a) Energization of transmission lines in one or more steps by inserting resistances and withdrawing them after- wards, b) Phase controlled closing of circuit breakers, c) Drainage of trapped charges before reclosing, d) Use of shunt reactors.
What are the types of over voltage?
Over voltage stressing a power system can be classified into two main types: 1-External overvoltage: generated by atmospheric disturbances of these disturbances, lightning is the most common and the most severe. 2. Internal overvoltages: generated by changes in the operating conditions of the network.
What is lightning over voltage?
Lightning overvoltages are fast-front transient voltages mainly caused by the impact of lightning return strokes to overhead lines. The lightning performance of an overhead line can be improved by shielding the line with shield wires installed at the top of towers or poles.
What are the causes of over voltage?
The main cause of these voltage surges in power system are due to lightning impulses and switching impulses of the system. But over voltage in the power system may also be caused by, insulation failure, arcing ground and resonance etc.
Why does over voltage occur?
Overvoltage occurs when the supply voltage rises above the rated voltage of the equipment or motor. Overvoltage can be caused by poor regulation of a power source from a utility company, oversized transformers, uneven or varying circuit loading, wiring errors, and electrical insulation or isolation failures.
How do you protect over voltage surges?
Lighning arrester or surge dividers.
- Earthing Screen. Earthing screen is generally used over electrical substation.
- Overhead Earth Wire. This method of over voltage protection is similar as earthing screen.
- Lightning Arrester.
What causes overvoltage?
Cause of overvoltage in power/electrical system External overvoltage happens due to lightning and atmospheric changes. Whereas internal overvoltage happens due to internal operation mood of the system. Internal overvoltages are dividing into power frequency overvoltage, operation overvoltage and resonances overvoltage.
How can you prevent overvoltage?
In order to protect the circuit from overvoltage conditions, Zener diodes are often the first option. A Zener diode follows the same diode theory, which blocks the current flow in the reverse direction.