The device uses an electric voltage regulator and an R-type transformer to form a high-voltage constant-current source, with push-button operation for voltage increase and decrease. It has a no-load voltage of 5600V and a short-circuit current of 100mA. It uses a high-sensitivity amplifier and a galvanometer to indicate balance, forming a balanced bridge with a proportional potentiometer, all at high potential. The measurement cable is a specially designed two-core high-voltage rubber cable, and a four-terminal resistance measurement method is used to eliminate errors introduced by lead resistance. The panel is maintained at low potential.
The cable sheath fault tester is particularly suitable for:
1. High-resistance breakdown points in cables after installation, especially linear high-resistance breakdown points that are difficult to burn down to low resistance, such as those at intermediate cable joints.
2. Flashover breakdown points, where the constant current source can maintain the arc after breakdown, a stable current flows through the bridge, and the bridge has sufficient sensitivity.
3. Low-resistance defects that have not yet broken down, such as insulation defects detected by a megohmmeter at low cable resistance but not breaking down under the operating voltage.
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