The terms overvoltage means that the voltage value has increase in the power system than the expected or design value. Every power system has its own voltage value that the system will run by this. But if it exceeds, than it will destroy since the semiconductor will exceed their ratings.

So, overvoltage is a problem in a power system as well as diesel generator. We will let you know about why overvoltage problem arises in diesel generator and how to prevent this problem. Hope this will help you a lot. To know about generator or for choose generator visit

Causes of overvoltage in diesel generator

There are plenty reason of overvoltage in generator. They are,

  • If the generator engine speed is unstable that means too high, then the voltage increase significantly.
  • If working load is exceed than the generator efficiency, and then the voltage will be unstable.
  • Sometimes voltage regulator components become hampered. On that occasions, voltage increases.
  • In diesel generator, fuel circulation could be unstable, which is another reason for voltage unstable.
  • If core gap are too large in shunt reactor of diesel generator, then overvoltage arises.
  • Because of pressure regulation, voltage increases. However, pressure regulation happens due to short circuit of magnetic rheostat.
  • Moreover, sudden loss of load is another reason of overvoltage.

These reasons are also for same as gas generator.

Cause of overvoltage in power/electrical system

Basically, there are two types of overvoltage which is external and internal overvoltage. 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.

Insulation failure: insulation failure is a common reason of overvoltage. Insulation failure happens when problem arises in grounding of the conductor. That means, if there is no insulation between the ground and the earth, and then insulation failure happens. Because one end of the conductor have to grounded so that the current can go downward.

Resonances: if inductive resistance and capacitive resistance are equal in a power system, then resonances occurs and resonance is a good reason for overvoltage. The system capacitor and electrical induction loop forms resonant loop which occurs high overvoltage and it has strong impact and long duration. 

Power system surges: overvoltage happens also for poor regulations of power source in an uneven way. This will damage the electronic component seriously.

Lightning: there are so many internal issues which is the reason of overvoltage.However, lightning is an external cause of overvoltage. Lightning causes the highest magnitude surges of overvoltage and it did serious harm for the system. So, every power system should be protected by voltage protector.

Arching ground: in three phase power system, if there is Sporadic Arc when line to ground conducting, then arching ground occurs. So, the changes of current load and voltage produce short live oscillations or overvoltage which leads to serious problem like breakdown of the system or the equipment which is connected to the system.

So, this is all about the cause of overvoltage of diesel generator as well as power system. I hope you will find this article helpful. Here is some related article how to connect generator to house without transfer switch.