Power cable length measurement method based on dispersion phenomena

The partial discharge fault detection and location with the method of oscillating wave detection system has been widely applied on medium voltage cable. However, due to inaccurate data of power cable length, the propagation velocity of travelling wave along power cable just is an experience value resulting in the great error of fault location. Based on the dispersion characteristics of signal propagation in power cable, a measurement method for cable length was proposed. First, the low/high frequency velocity was determined according the physical properties of the insulation and semiconducting layer material. Then, the sine wave signal with known propagation velocity was injected into the test power cable and the propagation time was recorded by the GPS timing equipment. At last, the specific length of test power cable was determined based on the experiment results at two different frequencies. The experimental results show that length value error of power cable resulting in the system error is less than 10m.