What is transient in a power system?

The transients are disturbances that would affect the power quality and it would be harmful to the equipment in a power system. The electrical transients would only take place for a few milliseconds, it can be described as a temporary surge. This fault would only last for few milliseconds but it would be enough to transfer a huge amount of power to the power system.

We can protect the power system from transient faults by isolating the faulty part in the power system so it won’t affect the other active part of the power system. In an electrical system, the transients would be generated according to the system configuration, type of source, line length, and terminations. The transient fault is a type of fault that won’t be present if the power is disconnected. In an electrical transmission system, there could be a lot of transient faults like the contact of the transmission lines with the tree, transient faults are also caused by lightning and it would also be created if two live conductors are in contact. We can say that a power system has transient stability only if it is able to recover its operational characteristics after a disturbance.   

How to improve the transient stability?

  • Fault clearing must be done quickly
  • Voltage should be controlled
  • The impedance of the transmission system must be taken care off
  • HVDC transmission links must be controlled
  • Protective devices must be properly used

What are the factors that affect transient stability?

  • Generator WR2 X rpm2 so if this quantity is greater then the acceleration factor is less
  • The fault duration is dependent upon how fast the circuit breaker acts and also the other protective devices
  • The loading of the generator before the fault would determine the internal voltage and also the change in output
  • The phase angle among the various internal voltages of the generator is determined by the system loading

What is the effect of the transient in a power system?

The transients in a power system are a fault in the power system and these faults could create changes in the system quantities. There would be changes in the system quantities such as over current, under-voltage or overvoltage power, power factor, frequency, impedance, temperature, and pressure variations. So these faults can be caused due to the transient faults and it would affect the equipment in a power system and thus the power transmission would be affected by this.  

What are the types of power system transients?

Electromagnetic transients

This type of transient is formed because of the magnetic field and electric field interaction in a power system. This type of transient would appear as a transmission wave on transmission lines, cables, bus sections, etc. This type of transients could be caused due to lightning and line switching. These transients could pay the way for over-voltages, over-currents, and abnormal waveforms. 

Electromechanical transients

As the name indicates these types of transients are formed by the interaction of the electrical energy and mechanical energy in the power system. Power oscillation is a major example of an electromechanical transient.

Impulsive transients

The impulsive transient can be described as a quick change of voltage or current, we can determine the impulsive transients by their rise and decay time. These transients should be reduced very fast by using the proper devices, and they shouldn’t be allowed to propagate far from their sources. The impulsive transients are mostly created by lightning.

Oscillatory transients

This type of transient is caused due to the energization of the capacitor banks, the frequency of the oscillation is dependent upon the capacitance of the capacitor banks and also on the short circuit impedance of the circuit that feeds the capacitor bank. The oscillatory transients are divided according to the frequency content, time duration, and also voltage magnitude.

Low-frequency oscillatory transients

This type of transient is created in the utility sub-transmission and distribution system. So in this, the primary frequency component will be less than 5khz and it also has a duration from 0.3-50ms.

Medium frequency oscillatory transients

This type of transient has a primary frequency component between 5khz and 500khz and it has a duration of 20 microseconds.

High-frequency oscillatory transient

The duration of these transients is only for a few microseconds and their frequency will be more than 500khz.


post-graduate in Electronics & communication.

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