위험전압 측정시스템의 설계 및 제작

Abstract

The ground system sets the reference potential in an electric circuit or protects devices by suppressing ground potential rise, dissipating fault current to earth. Currently, the performance of ground system is mainly evaluated as the ground resistance in low frequency region around 100[Hz]. However the ground resistance does not consider the ground potential rise, measurement of the ground resistivity, the ground impedance, and the risk voltage like the touch- and the step-voltage is necessary to evaluate the performance of ground system.

This thesis, therefore, dealt with the design and fabrication of a risk voltage measurement system (RVMS) which analyzes all the parameters above. The RVMS consists of a power source, a data acquisition module (DAQ), a signal processor, and a display. The power source can supply 300[Vrms] and 1.4[A] maximum in ranges from 40[Hz] to 1[kHz]. The DAQ module having resolution of 400 [kS/s] and 16 bit is equipped with 6 ports for voltage and a port for current. Also, a noise elimination algorithm of digital band-pass filter is applied to minimize a measurement error caused by external current flowing earth.

The performance of the RVMS is evaluated by measurement of the ground resistivity, the ground impedance and the risk voltage according to the IEEE standard 80 and 81 in a ground electrode with a 10[m] counterpoise. The result showed that the RVMS analyzes the ground resistivity and the ground impedance, and the risk voltage with error below 2[%] and 5[%], respectively.