The basic principles of power low voltage pulse reflection method
is in the manufacturer of the cable fault tester, cable fault tester is widely used in power cable fault detection. Explain the cable fault tester by below small make up to the working principle of the low voltage pulse reflection method.
power low voltage pulse reflection method, is also called the ground penetrating radar method. It is based on the transmission line theory, the cable is giving people a pulse voltage being measured, when transmitted pulse road encounter failure point on the cable, cable terminal or intermediate head, due to the change of the impedance at that point, and to test the movement of the reflection pulse, using the instrument to record in pulse time T, the transmitted pulse and reflection is transmitted pulse in a back and forth between the test and fault point.
scope of application: low voltage pulse method is used to measure the low resistance of cable, short circuit and single-line breakdown, can also be used to measure the length of the cable, wave speed, can also be used to distinguish between the middle of the cable head, tee joint, and terminal first.
low voltage pulse reflection method is only applicable to low resistance and short circuit or ground breaking linear fault test. For high impedance fault, due to the fault point of equivalent impedance is almost equal to the characteristic impedance of the cable, cause the fault point impedance mutation is not obvious, the reflection coefficient approximate to zero, the reflected pulse is quite weak. Low voltage pulse reflection method, therefore, cannot be effectively test high impedance fault, then need to adopt the following dc high voltage flashover method or shock high voltage flashover method for testing.
on the market at present technology is relatively mature SCM type cable fault tester, using low pressure pulse width of 0. 2 mu s / 2 mu s two gears, were used to measure the short and long cable.