Top Five Causes of Over Voltage in Power System

by Starlight Generator dieselgeneratortech

The so-called overvoltage refers to the abnormal voltage rise of the power system exceeding the working voltage under certain conditions, which is an electromagnetic interference phenomenon in the power system. The insulation of electrical equipment is tolerant to the working voltage for a long time, and must also withstand a certain range of overvoltage, so as to ensure the safe and reliable operation of the power system.

There are two types of overvoltage, external overvoltage and internal overvoltage. The external overvoltage is also called lightning overvoltage and atmospheric overvoltage. Caused by the discharge of thunderclouds in the atmosphere to the ground. The internal overvoltage is an overvoltage caused by a change in the internal operation mode of the power system, and is divided into a power frequency overvoltage, an operation overvoltage, and a resonant overvoltage.

The following are the top five causes of over voltage.

Power system surges. Due to poor regulation of the power source or power utility company, voltage fluctuations either over or under may occur. This may cause serious damage especially to electronic orcomputer controlled equipment. In this case, special attention should be given to these equipment to ensure safe usage. Relay devices, AVRs, auto-transformer type regulators may be used.

Insulation Failure. The most common form of insulation failure is when there is grounding of the conductor. Failure takes place when there is no insulation between the line and the earth. So, the part of the conductor that is grounded to the earth allows the current to flow downward.

Arcing Ground. This happens when there is presence of a sporadic arc in line-to-ground fault belonging to three-phase system. Here, short-live oscillations are produced in the system due to some changes in the voltage and the current load. This phenomenon may lead to serious problems like breakdown of the insulation and may harm equipment connected to the power system.

Resonance. This one occurs when the value of the inductive resistance in the power system becomes equal with the value of capacitive resistance.

External causes. Although many cases of over-voltage result from the internal causes as listed above, studies show that the highest surges are still contributed by some external causes. Lightning is one good example, which has already been cited as responsible for high magnitude of surges, leading to very serious failures. This is because an external factor such as lightning is capable of increasing the voltage by many times higher that the normal value. This is the reason why power systems and appliances should be protected with voltage protectors.