What is the purpose of interposing CT?

The main fuction of an interposing CT is to balance the current supplied to the relay or others where threre would otherwise be an imbalance due to the ratios of the main CTs. Interposing CTs are equipment with a ratio that can be selected by the user to achieve the balance required.

What is a current transformer commonly used for?

Current transformers are used for protection, measurement and control in high-voltage electrical substations and the electrical grid. Current transformers may be installed inside switchgear or in apparatus bushings, but very often free-standing outdoor current transformers are used.

What is the use of neutral current transformer?

A Neutral Current Transformer encircles the neutral conductor (or is placed in-line on a bus); required on circuit breakers with Ground Fault Protection when applied on a grounded system.

What is an interposing transformer?

The Interposing Current Transformers, ICTs ,are used to Balance, match or isolate the current supply for the equipment connected to it. ICTs are installed between Main CT and Equipment whose current supply has to be matched.

What is an interposing voltage transformer?

It is commonly used to supply instruments such as voltmeters, voltage coils on wattmeters, protective relays, and the like. It finds uses for stepping up very low voltages for ease of measurement and stepping down very high voltages to low levels for safety in measurement.

What is the difference between voltage and current transformer?

One of the major difference between them is that the current transformer converts the high value of current into low value whereas the potential or voltage transformer converts the high value of voltages into low voltage.

What is ref and SEF protection?

It is backup protection for restricted earth fault (REF) relay. It operates the CB when REF is failed to trip the circuit, Heavy earth fault outside of the REF protective Zone, and all other earth faults. Simply we can say, it is standby protection for all other earth faults.

What is a current transformer?

The Current Transformer ( C.T. ), is a type of “instrument transformer” that is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary.

How does a CT transformer work?

Current transformers can reduce or “step-down” current levels from thousands of amperes down to a standard output of a known ratio to either 5 Amps or 1 Amp for normal operation. Thus, small and accurate instruments and control devices can be used with CT’s because they are insulated away from any high-voltage power lines.

What are the different metering applications of current transformers?

There are a variety of metering applications and uses for current transformers such as with Wattmeter’s, power factor meters, watt-hour meters, protective relays, or as trip coils in magnetic circuit breakers, or MCB’s.

What is the function of the primary winding in a transformer?

Function. The primary ‘winding’ may be a permanent part of the current transformer, i.e. a heavy copper bar to carry current through the core. Window-type current transformers are also common, which can have circuit cables run through the middle of an opening in the core to provide a single-turn primary winding.