In the field of electrical engineering, the term 'transient voltage' is very well known. You must know about transient voltage while you taking care of your electrical circuits, costly electrical machines, electronic devices, etc. Transient voltage may be very dangerous and can affect badly if protection is not taken against it. But before that, you must know its sources and causes.

## What is Transient Voltage?

Transient voltage is an unwanted temporary very high voltage that suddenly occurs in an electrical circuit or power line. Voltage surge or surge voltage differs from over-voltage, voltage swells, voltage fluctuations, and voltage dip. Actually, these all are differing depends upon the magnitude and time duration. Voltage transient has the highest magnitude and very short time duration. That means in an electrical circuit or power line if the voltage rises to a very high level in a very short time duration then it can be called the voltage transient. Voltage transient is very similar to voltage spike because in both cases, voltage increases very high just the difference is voltage transient has a short time duration than voltage spike.

## Sources of Transient Voltage

Natural Lightning is the most common source of surge voltage. It raises the voltage to a very high level than other sources.

The natural capacitance effect in the transmission line is also a source of surge voltage. The capacitance effect in the transmission line stores the electrical energy and suddenly it releases the electrical through the power lines. Due to that voltage suddenly raises which is known as the transient voltage.

Other sources of transient voltage are faulty contactors, tripped circuit breakers, Power Factor Correction Equipment, and reactive elements of electrical or electronic circuits.

Electromagnetic Pulses (EMP) and Electrostatic Discharge or ESD are also natural sources of surge voltage.

## Causes of Transient Voltage

Already we have known the natural sources of transient voltage from which transient voltage occurs naturally. Now we will know what are the common accidental causes due to which surge voltage occurs in the circuit.

The common causes or activities for the occurrence of surge voltage are frequent switching, the sudden disconnect of load from the power supply, improper operation of electrical motors with varying loads, improper operation and handling of capacitor banks, improper handling, and operation of reactive devices.

Load Shedding, grid switching, fault clearing, or re-energizing after a power outage can generate transient voltages.

So by handling and operating the reactive devices properly, we can solve the 80 percent problem of the surge voltage. But to prevent the circuit and devices from natural sources we have to take the protection system.

## Effects of Transient Voltage

The transient voltage causes to flow of a very high current in electrical and electronic circuits.
High current flow in any circuit can damage the conductors, burn the coil, and cause to spark, and fire. So transient voltage is very dangerous for your circuits as well as electrical and electronic devices.

Transient voltage can cause data loss or corruption in electronic storage devices, such as hard drives and solid-state drives. In critical systems or data centers, this can lead to significant financial or operational consequences.

Electronic components are mostly affected by transient voltage. Because they are designed to operate with a very low current and voltage. So rising in voltage can damage the conductive path of the electronic component, and damage the internal circuit. Electronic ICs are facing these issues. Electronic components are mostly affected due to surge voltage caused by ESD. That's why electronic manufacturing companies are used the ESD protection system.

## Transient Voltage Protection

The different ways for the transient voltage protection are,
• Limiting the voltage amplitude
• Limiting the current
• Shorten the transient time duration
• Bypassing the excess current

So there are different types of transient voltage protective devices are available which work in any one principle from the above.

Series Reactor(made of inductors) is a transient voltage protective device that works on the principle of current limiting. When transient voltage occurs, it limits the excess current.

A shunt Reactor(made of capacitors) is also a transient voltage protective that works on the principle of current bypassing. So when transient voltage occurs, it bypasses the excess current to the ground.

Diode, thyristor, and varistor are used for the protection of electronic circuits and components from the surge voltage.