Cable Sheath Fault Locator Murray Bridge Tester 5600V No-Load Voltage 100mA Short-Circuit Current | XHHG521B

The XZH TEST XHHG521B cable sheath fault locator is designed based on the principle of the MURRAY bridge. It is used to locate the breakdown points of various wires and cables after laying, and the defect points with no breakdown but low insulation resistance. It can also be used to locate the defective points of various cables in the cable factory.

Equipped with a high-voltage constant current source built from an electric voltage regulator and an R-type transformer, the instrument applies a four-terminal resistance measurement method to eliminate lead resistance errors. The panel stays at low potential while the measuring circuit is at high potential, ensuring safe operation. With a one-key operation interface and a built-in display, the fault distance is automatically calculated once the cable length is entered.

The cable fault locating bridge method works as follows: the fault phase and the non-fault phase of the cable under test are short-circuited at the far end; the two arms of the bridge are connected to the fault phase and the non-fault phase respectively; by adjusting the variable resistor on one arm until the bridge is balanced, the fault distance is calculated from the ratio reading P and the known cable length: L1 = P% × L. The bridge method is simple, and its accuracy meets on-site engineering test requirements, making two-phase short-circuit fault testing particularly convenient. The MURRAY bridge is the classic method for breakdown point location, and the XHHG521B is especially suitable for the following fault conditions:

A typical test follows these steps: first, confirm the breakdown state of the cable and record the insulation resistance or breakdown residual voltage of each core with a multimeter or megohmmeter; second, record the cable length, model and cross-section, and short-circuit the far-end terminals of the faulty cable and the auxiliary cable with a guardian on site; third, connect the instrument ground terminal reliably to the site grounding body, connect the red clip to the faulty phase core and the black clip to the auxiliary cable core; fourth, raise the voltage until the current exceeds 20mA, keep it stable to form a stable arc or conductive zone, and adjust the balance knob until the galvanometer points to zero; finally, read the balance ratio P, input the cable length, and the instrument automatically calculates the fault distance. A reversed-connection check can be made by swapping the measuring clips to obtain another reading P2, and the two readings should satisfy P1+P2=100.

This instrument provides cable engineers with a reliable, comprehensive solution for cable sheath and insulation fault location, helping minimize outage time and excavation cost through accurate bridge-based fault distance measurement without blind zones. The instrument is suitable for both indoor and outdoor use, and at least two operators are required on site for safe high-voltage testing.