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Why neatural ground resistor using in 33kv transformer?
The function of a neutral earth resistor is to limit any fault current resulting from fault between a line conductor and earth.
How does cable sizing calculation gets affected by earth leakage protection?
Ground / earth protection will not impact cable sizing.
What is an Unrestricted Earth Fault?
I'm guessing this is in reference to a restricted earth fault, and you want to know what the opposite is? Restricted earth fault protection is designed to operate for earth faults within a specific zone. Unrestricted protection will operate for faults "anywhere", as long as the pickup can be satisfied. For example, REF (restricted earth fault) transformer protection looks for a small amount of neutral current, and if this exists, and the relay identifies this current as being within the zone of protection, the relay will trip. If it were unrestricted, the small amount of neutral current alone would be enough to cause a trip.
What is difference between neutral grounding reactor and neutral grounding resistor?
They both reduce earth fault levels by inserting impedance in the return path. A reactor is used when the earth fault level wanted is greater than about 25% of the phase fault current. This limit is due to over voltages experienced in arcing faults, the higher the reactor impedance the higher the potential overvoltage. With resistors lower fault levels are possible, but as the resistor has to dissipate all energy it will generally be more expensive and larger than a reactor.
What current does the input required to give an output on Lm741?
It depends on the shunt feedback resistor on the op-amp, for example with a 10k feedback resistor connecting the output to the inverting input, 1 mA input current gives 10 volts signal output. The input terminal stays near zero voltage because of the high open-loop gain of the op-amp, so the inverting input is termed a 'virtual earth'.
