Low Voltage TDR Cable Fault Locator with Rough Fault Distance Detection

Regarding waveforms

1. Standard waveform for open circuit fault

Analysis: At time t1, the pulse waveform generated by the flash detector is positive (but can also be negative); at time t2, the reflected pulse waveform from the intermediate joint in the cable (reflected waves from joints are generally of the same polarity, but this depends on the joint structure); at time t3, the reflected pulse waveform from an open-circuit fault is positive and of the same polarity (the polarity of the fault waveform is the same as the polarity of the pulse wave generated by the instrument); at time t4, the secondary reflected pulse waveform from the open-circuit fault. Due to pulse attenuation, the secondary reflected wave at time t4 has a smaller amplitude than the primary reflected wave at time t3. The distance S from the fault point to the measuring end is... In actual operation, by moving the cursor, the instrument will automatically display and calculate the distance to the fault point.

2. Standard waveform for low impedance fault

Analysis: At time t1, the pulse waveform generated by the flash detector is positive (or negative); at time t2, the reflected waveform from the intermediate joint in the cable is shown; at time t3, the reflected waveform from the low-resistance fault point is negative, representing a reflection with opposite polarity (opposite to the pulse waveform generated by the instrument); at time t4, the reflected waveform from the cable terminal is shown. The distance from the fault point to the measuring end is also considered.