Instrument transformers: a) How is an instrument transformer characterised? Give an example for each category.

Instrument transformers: a) How is an instrument transformer characterised? Give an example for each category. b) What has to be done to avoid that the power is transferred? c) Why is it concerning the currents necessary to measure high overcurrents, but not concerning the voltages necessary to measure high overvoltages?Instrument transformers: a) How is an instrument transformer characterised? Give an example for each category.It mainly used for power isolation and reduce the cable size easy handling .say example PT %26amp; CT.. potential transformer used for getting refference voltage for protection relays 11,000/100Volts or(23KV/100V) any high voltage to 100vAC.same way current transformer 1000Amps/1Amps or any current to 1 amps or 5 amps occording to the instrument requirement.this transformer are designed with proper care with proper insulation to handle the high voltage .onlu low voltage is taken for Instrument %26amp; relays in measurement cubicle.those transformers are fixed in High voltage breakers no access when it is in service.those trransformer cores are specially desinged handle the particular current.same principle small instrument transformers are designed for transient recorder energy measurement, earth fault relays , over current relays,various protection relays used in power generation to transmission.I have given little idea only .Further requirement pm me .