Development of an on-line impedance meter to measure the impedance of a distribution line

In order to tackle the problem of harmonic elements in a distribution line system, it is important that we are able to measure the impedance of the distribution line in a simple way. In addition, it is desirable that we make the measurement without service interruption. The line impedance could be measured by a technique derived from fundamental measurement theory, in which only passive elements such as inductors or resistors are used. However, as the voltage and/or current being measured increases, the size of inductor or resistor would also need to be increased, so it would be very difficult for such a measurement system to be implemented. Under such circumstances, a novel measurement method for determining line impedance using an inverter circuit is proposed in this paper. In the case where we are determining the resistance, the result that we obtain also includes the circuit loss, so this needs to be measured in advance and subtracted from the result. In the case where we are determining the inductance, the line inductance can be measured relatively accurately.