DC Toleranace Electronic Current Sensor For Utility Power Metering

Power Metering System Seminar Report

Current sensor is a device which detects the current produce a signal proportional to it. The current sensor in current transformer is made of low permeability material for dc tolerance result in an unacceptably high magnetizing current and consequent gain and phase errors at all except very high frequencies.A su ciently high dc current in the primary winding may therefore saturate the core material since no cancelling magnetomotive force (mmf) can be supplied by the secondary winding. The transformer consists a uxchange sense winding and feedforward of the voltage developed across the secondary winding and burden resistances.

The increasing size and complexity of modern power systems have added more demands on the level required for the control, monitoring and protection of the system. Multi-function electronic meters are also replacing electromechanical induction types for high-accuracy, high voltage metering of bulk electrical energy.

These electronic meters and relays are very accurate, very sensitive and fast in their response. For intelligent metering and load management accurate voltage and current measurement is important. In the development of a current sensor for intelligent metering and load management should have following characteristics to be met:

1. High accuracy over wide dynamic range

2. Low cost

3. Reliability

4. Low power consumption

5. Low drift in output signal with time and temperature

6. High dc tolerance

7. Low sensitivity to currents in adjacent conductors

The high delity current sensors are used for utility power metering. The sensor are used on current transformers with low permeability core material for high dc tolerance. The transformer is having a  ux-change sense winding and feed forward of the voltage developed across the secondary winding and burden resistances, minimizes the error when dc current superimposed onto the current under measurement.

Seminar Report Consists of

>Rogowski coil 

>Closed loop variant hall e ect sensor

>Equivalent circuit of current transformer

>Op-amp circuitry across CT secondary terminal

>Compensating voltage in series with the CT secondary winding

>Ampli ed voltage applied in series to secondary winding

>Block diagram for the circuit 

>Combined Feed forward of Voltage across Secondary Series Resistance and Feedback from the Flux-Change Sense Winding

>Schematic diagram of experimental circuit showing main components

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