What is the generator IR value when generator is filled with stator water and hydrogen?

What is the generator IR value when generator is filled with stator water and hydrogen?  
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1 Answer

Answer :

Generator IR when filled with stator water and hydrogen is about 100 kΩ only. That is because most of the gases and liquids are self-restoring insulators. As we are measuring insulation with 1 kV or 5 kV megger, the ionic current or leakage current will be same and the IR value will be approximately same. As we are increasing the test voltage to higher value say to 100 kV the breakdown point will occur as in the graph and insulators will breakdown or puncture.

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Water and hydrogen are self-restoring insulators. First we are measuring insulation on 1 kV voltage i.e. 100 kΩ. As the field voltage and stator voltage raises the heat produced in the stator and rotor will increase the IR value of the machine in running condition. So ionic current region needs 1 kV/cm, saturation region moderate voltage (1 kV to 70 kV), and breakdown region is above 70 kV voltage.  

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