Abstract
As for the direct-current (DC) power systems, the DC leakage current sensor is indispensable for positioning insulation faults. And in this paper, a quasi-digital flux gate sensor was designed based on duty ratio model, and the mathematical model between the excitation voltage period and the measured current which exceeded the measurement range was built by analyzing the working principles of the duty-ratio model digital sensor. In this way, the measurement range of the original sensor could be expanded to 1.5 times of its original. Meanwhile, without changing the hardware, the solution provided in this paper also solved the measurement failure problem of part of sensors when the any overcurrent situations happen in the system, such as overload or short-circuit. Besides, the sensor designed in this paper could achieve Level-0.1 measurement accuracy within range, and reach Level-2 over-range measurement accuracy, satisfying the demands of DC power supply system on leakage current measurement.
Highlights
The DC system has become the tendency of power system development
As a matter of fact, the insulation fault positioning of the DC system depends on the DC leakage current sensor
The results show that, under the precondition of no hardware change, the duty ratio model sensor could improve the measurement range of the sensor by measuring excitation voltage period
Summary
The DC system has become the tendency of power system development. The direct current has been taken as the main power distribution form in fields of electric vehicles, ships, microgrids, and new energy sources [1]–[4]. According to the principles of the such sensors based on duty-ratio model, and combining with specific design for the sensor core, excitation coil and external circuit, it was made to be able to measure small leakage current in this paper, which is convenient for insulation measurement. The results show that, under the precondition of no hardware change, the duty ratio model sensor could improve the measurement range of the sensor by measuring excitation voltage period. This provides a solution for using this type of sensors to carry out over-range measurement, such as overload and short-circuit current, etc
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