Experimental study of Tunnel and Anisotropic Magnetoresistive sensor for power system magnetic field measurement applications

This experimental investigation is focused to assess a Tunnel Magneto-Resistive (TMR) and Anisotropic Magneto-Resistive (AMR) sensor for power system magnetic field measurement applications as in current sensing, transmission line monitoring, detection and classification of Transient Magnetic Field (TMF) interference in substations. For measurement applications, AMR sensors have the limitations of low field range up to ±6 Gauss impractical for high magnetic field measurements, disorientation in sensitivity at exposure to field over ±20 Gauss recurrent in outdoor applications and high power consumption not appealing for portable devices. Thus, a complete testing system is established to identify if TMR sensors are a superior candidate for our application domain. For this, both of the sensors were exposed to uniform and transient magnetic field. Experimentation with identical conditioning circuitry confirms the superior performance of TMR sensor over AMR sensor in terms of twice the sensitivity, 200 times reduced power consumption and 5 times more field range. Additionally, in a TMF event, AMR sensor response depicts a time lag of 15 microseconds whereas TMR sensor only lags by 10 nanoseconds. Magnetic fields above field range of AMR sensor disorient the sensor until recalibrated; to cater for this a practical recalibration pulse blinds the sensor for 4 milliseconds once initiated.