Instrument transformer- type, application and functions.

Instrument Transformers is used to collect voltage and current data lowering the value by a certain ratio that can be used by relay, PLC etc. This ensures safety and cost effective automation and control system.

Protection or metering devices have to receive data on electrical values (current or voltage) from the equipment to be protected.For technical, economic and safety reasons, this data cannot be obtained directly on the equipment’s MV power supply to small powered Relay, PLC or electronic devices; we have to use intermediary sensors like Instrument Transformers.

Instrument transformers types:

Current transformers

Current transformers Connected on the MV network primary circuit, they supply a reduced current value to the secondary circuit,  proportional to the network current on which they are installed.

Current transformer is of two types-CT: current transformer; LPCT (Low Power Current Transformer): electronic current transformers.

Voltage transformers

Voltage transformers Connected to the MV network primary, they supply the secondary circuit with a reduced voltage value, proportional to the network voltage on which they are installed.

Function of instrument transformer:

The function of instrument transformer is as follows- 1.Reducing the size of value to be measured providing galvanic separation; 2.Supplying the power needed to process the data, or even for the protection device to work.

Instrument transformer being an analogue device can be attached with the following network systems-1.Analogue devices, directly using the supplied signal, 2.Digital processing units with a microprocessor, after analogue/digital conversion of the input signal (e.g.: PLC – programmable Logic Controller).

instrument transformer
Example of instrument transformer application protection and metering application

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