How to measure the breakpoint of photovoltaic wire and cable?

During the installation of photovoltaic systems, the most fearful thing for maintenance personnel is that they can't find where the broken point is when the wires and cables are interrupted. Today we're going to discuss what technical methods are available to detect cable breakpoints!

When a fault occurs in the internal medium of the cable, the exact position cannot be seen when the outer part of the cable is covered with insulation, including strong and weak currents. Usually, the idea of finding the breaking point is to check in sections.

For example, if there is a gap in the middle of a cable, you can measure from the two ends and three points in the middle, and take the middle point for measurement on which side is blocked, so that you can quickly find the location of the breakpoint by narrowing the scope of investigation.

So in general, what are the measurement methods to accurately measure the wire and cable breakpoints?

01. Multimeter detection method

The first is to connect one end of the unconnected whole cable to the live line of strong electricity, and leave the other end empty. Turn the multimeter to the AC2V gear, start from the cable connection end, hold the black pen tip while slowly moving the red pen along the insulation of the wire, the voltage value displayed on the display is about 0.445V. 

When the red test pen moves somewhere, the voltage displayed on the display suddenly drops to 0.0 volts, which is about one-tenth of the original voltage. The breakpoint is about 15cm forward from this position (the fire wire access end). 

02. Inductive electric pen detection method

An induction test pen is a device with an electronic screen that can detect voltage and continuity. First, exclude the power supply of the cable around the breakpoint cable, then connect the cable with the breakpoint to the live wire, hold the electric pen perpendicular to the wire, press and hold the "Induction Breakpoint Test" button to move forward slowly on the wire, and wait for the test pen to detect When the AC signal appears and disappears suddenly, it can be judged that the breakpoint is at the detection point, and the error does not exceed 10cm at most.

A word of caution: the cables around the breakpoint wires must not carry power. In addition, it should be reminded that this method is not a panacea, the effect of short cables is obvious, and the longer the cable, the worse the effect.

03. Use an audio detector

The audio detector is an instrument that uses single frequency or multiple frequency signals to test the continuity of the line to identify line faults. It can find the line directly under the condition of connecting any switch, router, PC terminal. When tracing the cable line, there is no need to strip the outer sheath of the line, which is simple and fast, and the position of the line breakpoint can be identified.

04. Cable fault tester

It is a comprehensive set of cable fault detection instruments. It can test the high-resistance flashover fault of the cable, the grounding of high and low resistance, short circuit and cable disconnection, poor contact and other faults. If equipped with an acoustic measuring method, the precise location of the fault point can be accurately determined. It is especially suitable for testing power cables and communication cables of various types and voltage levels.

05. Polyline detection method

Connect one end of the wire with the breakpoint to the black test lead of the multimeter and the other end to the red test lead. The multimeter is in the 200Ω resistance range. Bend back and forth where the wire is most likely to break (such as the point of frequent bends). If the multimeter shows that it is on and off, this is the breakpoint. If you still can't judge, you need to start bending from one end of the cable until you find the breakpoint. This method is suitable for shorter cables.

06. Acupuncture detection method

This method is a damage detection method. Insert a steel needle on the broken cable in sections, and use a multimeter to measure the continuity between the steel needle and the cable end to judge the breakpoint of the cable.

It is not recommended to use it under normal circumstances, because it will destroy the insulation layer, and it is easy to cause other problems in the later use of the cable, especially in an environment with high humidity. This method is to use the continuity of the cable to check the breakpoint of the cable.

07. Pulling wire detection method

This is also a damage detection method, which is generally not used in practice, but it is also a method listed together. Use a vise to pull the broken wire of the cable end. If the breakpoint is near the cable end, the insulation The skin is easily pulled off. This method is used for cables where the breakpoint is near the end of the cable.

To measure the breakpoints of wires and cables, you can refer to several methods introduced today. It is better to use instruments and equipment to improve work efficiency under conditions