What is the Difference Between Sensitive Earth Fault & Rotor Earth Fault

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Dear friend:

I reviewed the manual before sending my question and it talking about the explanation of each function but didn't explain the difference between them and when can I use neither of them.

If you Google each of these there are plenty of explanations available. You can work out what the difference is by learning what each is and where they are applicable.

Of course I did as you said before asking my question.

This is the drawing for Rotor earth fault protection

and this is the drawing for sensitive earth fault when using as rotor earth fault

Now as you see the first scheme depends on measuring the voltage and current by the device 7UM62 to calculate the rotor earth resistance.

But the second scheme just measure the current only.

When can I use neither of them? and what is the difference between them ? is one of them more sensitive than another?

Rotor earth fault requires PT and CT to protect rotor from overpotential and overcurrent. This protects windings and insulation. Refer to NEC 2011 for additional information regarding wire ampacity.

Earth fault requires CT only to monitor overcurrent condition.

Which is more sensitive? The Earth fault should be of greater sensitivity to protect the equipment to shut it down.

The Rotor earth fault protection is designed specifically to protect the rotor.

However, I would contact the manufacturer and ask them about the quality of the CT's and their specification sheets and also specs for the PT.

CT specifications for protecting equipment vs. metering differ and also the applications change and CT's change given the type of voltage that is being monitored.

You took a good step in reading the manual. Go that extra mile and talk with their tech support and ask your questions there as well.