An Equipotential Sensor For Voltage Measuring And Research On The Application Of Voltage Protection In Metallic Shell Surfaces

In recent years,people have higher requirements on the reliability of power supply and the safety of electricity consumption with more and more electrical appliances coming into people’s lives The accident caused by the leakage of the equipment shell not only occurs in the daily life of the residents but also exists in the low voltage distribution network of factory.The damage to the electrical equipment or personal electric shock casualties are often caused by the dangerous voltage produced by the electrical equipment shell,metal base and other parts.There are many kinds of leakage protection device;however,the traditional leakage protection device couldn’t operate under some circumstances although the electrical equipment uses the protection grounded or protection to zero.In order to improve the safety of household electrical appliances and the safety of low-voltage electrical equipment operators,a new leakage measurement principle is proposed on the principle of equal potential measurement and a new voltage measurement sensor is designed and used in the design of a new type of voltage leakage protection device to prevent a series of electric shock accident effectively.The main work of this paper mainly includes these aspects:(1)The linear relationship between the source and the electric field is introduced.The specific structure of an equipotential sensor is proposed on the basis of analyzing the voltage measurement principle of electric field coupling mode and the transfer function of the sensor is developed.A new measuring method of metal casing leakage is proposed based on the equipotential sensor.The theoretical work provides a preparation for the design of the protection device.(2)The equipotential sensor is modeled and simulated by COMSOL which is an electromagnetic field finite element calculation software and the specific parameters of the sensor are determined.The electric field distribution inside the sensor is analyzed to ensure the insulation capacity.The measuring principle of the equipotential sensor is verified and the equipotential sensor is made for the following test.(3)Aiming at the signal of the output voltage,the signal processing circuit is established.The alarm and relay action circuit is designed based on MSP430 MCU due to the needs of Leakage protection.The software debugging of system is compiled.The measurement,analysis and processing of the sensor output signal is realized and the design of voltage leakage protection device based on equipotential sensor is completed.(4)The test platform is set up for steady-state performance test and transient switching performance of the sensor and the results prove that the equipotential sensor has good performance of steady state response.The performance of the leakage protection device is tested and the reliability of the protection device is verified which could act less than 10 milliseconds and the relay would operate.