Xhhg521A Digital Cable Fault Sheath Prelocator for Underground Cable Fault Distance Measure

Introduction
The cable outer sheath fault tester XHHG521A is designed based on the MURRAY bridge principle and can be used to locate the breakdown points of various wires and cables and the defect points that have no breakdown but low insulation resistance values.

The device utilizes an electric voltage regulator in combination with an R-type transformer to create a high-voltage constant current source. The voltage can be adjusted upward or downward via button operation. It features a no-load voltage of 7,500V and a short - circuit current of 100mA. A high - sensitivity amplifier and galvanometer are employed to indicate balance. Together with a proportional potentiometer, it constitutes a balanced bridge, and the entire setup is situated at a high potential. The measurement cable is a specially designed two - core high - voltage rubber cable. The four - terminal resistance measurement method is applied to eliminate errors resulting from lead resistance. The entire panel remains at a low potential. One - touch operation allows for entering the cable length and automatically calculating the fault distance. The high - voltage source and bridge are integrated into a portable protective box. Thus, the device boasts high voltage, light weight, easy operation and safe use.

High voltage bridges are particularly suitable for
1. The high-resistance breakdown point of the cable after laying, especially the linear high-resistance breakdown point that is difficult to burn into low resistance, such as the linear high-resistance breakdown of the cable intermediate joint.
2. Flashover type breakdown point. After breakdown, the constant current source can maintain the arc, a stable current flows through the bridge, and the bridge has sufficient sensitivity.
3. Defects that have not yet broken down but have low resistance, such as insulation defects found with a megohmmeter that have low cable resistance but do not break down under the operating voltage.