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 equipment makes use of an electric voltage regulator along with an R - type transformer to set up a high - voltage constant current source. The voltage can be raised or lowered through button operation. The no - load voltage reaches 7,500V, and the short - circuit current is 100mA. For balance indication, a high - sensitivity amplifier and galvanometer are used. Combined with a proportional potentiometer, it forms a balanced bridge, which is positioned at a high potential. The measurement cable is a specially designed two - core high - voltage rubber cable. The four - terminal resistance measurement method helps avoid errors due to lead resistance. The entire panel is maintained at a low potential. One - touch operation allows the entry of cable length and the automatic calculation of the fault distance. The high - voltage source and bridge are integrated in a portable protective box. Therefore, the device has high voltage, is lightweight, easy to operate and safe to 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.