Main Purpose of Using Neutral Grounding Resistor

Neutral Grounding Resistor(NGR)



The main purpose of using Neutral Grounding Resistor(NGR) in the Power system is to limit the high current which flowing due to Line to Earth fault.

In the substation, the Neutral point of the secondary winding of the Transformer is connected to the earth through a Resistor. This resistor is called Neutral Grounding Resistor. In generating station the neutral point of the Alternator also connected to the earth.

We already discussed why we need Earthing and Grounding, What is the Difference between Earthing and Grounding. You can read can read that article. Today we are going to know why we need the Neutral Grounding Resistor.



The main purpose of Neutral grounding Resistor:



Neutral grounding Resistor, alternator, neutral grounding


As you see in the above figure, the neutral point of the alternator is connected to the ground. Now if by chance Line to Earth fault occurs then a huge amount of current will flow. According to the above figure, a huge amount of current will flow through the 'B' phase and Earth. This huge amount of current will damage the winding of the Alternator. That is why we connect the neutral point to the earth through a resistor which limits the high current during fault and protects the alternator from damage.



Neutral Grounding Resistor, purpose of NGR, transformer grounding


Again you can see in the above figure, the neutral point of the secondary winding of the transformer is connected to earth through a resistor. Here also the same reason for using Neutral Grounding Resistor as previous. Here the resistor protects the Transformer from damage.




Other importance of Neutral Grounding Resistor:



(1) The current flowing through the Neutral Grounding Resistor can be monitored and measured. This can be used to operate the Earth Fault Relay. Earth fault Realy will trip the circuit when the earth fault occurs.



(2) The Neutral Grounding Resistor provides the protection against Transient Overvoltage.


(3) It helps to connect other protective equipment(like Relay) which cannot operate with high current, so to reduces the current, this resistor is also used.





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Main Purpose of Using Neutral Grounding Resistor Main Purpose of Using Neutral Grounding Resistor Reviewed by ETechnoG on 11:25 Rating: 5
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