Purpose/Aim
With the proposal of the concept of smart grid, the comprehensive monitoring of power grid information has become a hot topic. Power grid information includes voltage, current, temperature and other information of transmission lines. According to these information, the operation status of power grid can be monitored and fault early warning can be realized. Among them, current monitoring of transmission line is an important way to judge the condition of the line. At present, the traditional current measurement method usually uses the current transformer with large volume, which has not been widely arranged in all parts of the power grid. Other current measurement methods also have problems so that they can not be widely used. Therefore, a sensor device based on TMR which is able to measure wide range current is proposed in this paper.
Experimental/Modeling methods
In this paper, the equations of current and magnetic field are calculated. It is obtained that the magnetic field generated by the current is linear with the current, with the amplification of the magnetic ring. Besides, the output voltage of TMR sensor is linear with the magnetic field. Based on the result, two measurement schemes are proposed for different ranges of current. Two current measurement methods are designed and fabricated to measure power frequency current and transient current respectively.
Results/discussion
The performance of the two sensors are tested under laboratory conditions. The sensor can measure the power frequency current of 0 - 500A with good linearity, and the sensor can also timely and effectively reflect the transient current waveform of lightning current, and the amplitude has good linearity.
Conclusions
The current sensor based on TMR designed in this paper can measure a wide range of power frequency current and can measure a lightning current with high frequency and large value. It provides a reference for the full information monitoring of smart grid.
 

smart grid,Monitoring,TMR