382 / 2022-03-15 18:21:11

Development of transient current sensor based on tunnel magneto resistance effect

transient current,tunnel magneto resistance effect

Purpose

With the development of smart grid, the current under various operating states in the power grid needs to be monitored in real time. In order to satisfy the measurement requirements of transient current, the sensor should be able to response the frequency from DC to MHz. The previous Rogowski coil or shunt were not suitable due to the frequency bandwidth limitation or installation mode, It is necessary to develop a non-invasive current sensor with wide frequency band, small volume and excellent stability.

Experimental

A transient current sensor for power system monitoring is designed based on the tunnel magneto resistance chip. The linear magnetic field range, temperature characteristics and frequency characteristics have been tested for the chip.

In order to improve the measurement accuracy of the current sensor, the sensor is designed as a closed-loop structure. A large capacity operational amplifier is selected to effectively expand the measurement bandwidth and increase the measurement sensitivity and the soft magnetic material with excellent characteristics is selected as the magnetic concentrating ring.

The influence of the inner diameter, outer diameter and thickness of the concentrator ring on the measurement error of the current sensor is simulated. The influence of the eccentricity of the central conductor of the current sensor on the measurement error is also simulated. The simulated results used for the design of the sensor parameters .

Compared with the standard shunt, the linearity of the sensor under DC and AC current is better than 0.5% within 500A. Under  (8/20)μs lightning impulse current, the linearity is better than 1%, and the time error of front time is less than 1.0%, the error of tail time is less than 0.5%.     

Conclusions

The designed current sensor based on tunnel magnetoresistance effect can meet the parameter requirements of accurate monitoring from DC current to transient current in power grid system. The designed temperature compensation module can ensure the parameter stability of the sensor in a wide temperature variation range, and can be widely used in power grid current monitoring.