General advantages of thermopiles are their stability, low ohmic value ( which implies little pickup of electromagnetic disturbances ), good signal-noise ratio and the fact that zero input gives zero output.
2.
The CT sends a signal current to an external sensing circuit ( the protection system ) which then sends a signal to the relevant circuit breaker to open and disconnect the supply or isolate the generator ( or transformer ) from the fault . The ohmic value of the resistor is calculated as a function of the permissible fault current and the system voltage to earth.
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