Method of measuring cable breakpoint by capacitance method-Henan Sanheng Cable Co.,Ltd

Method of measuring cable breakpoint by capacitance method

Jun 14,2018

When the cable is covered with a metal armored layer such as a copper tape or a steel tape, the induction method cannot be detected. At this time, the method of capacitance is used; it is applicable to all cables; when the capacitance method is used, the principle of the capacitance test is first understood. When the capacitor is tested, The AC/pulse signal is used in the test loop, that is to measure the AC partial voltage or to charge and discharge the capacitor body (two metal electrodes insulated from each other), and to test the accumulated electric quantity on the capacitor body and convert it into a capacitance reading.

Capacitor method to measure the break point of cable

Method of measuring cable breakpoint by capacitance method

Do you know how to measure cable breakpoints by capacitance?

The capacitance method may affect the accuracy due to the inductance of the cable wound into a loop and the insulating cores are wound together, the resistance of the non-good conductor (such as a steel strip), and the stray capacitance between the electrical conductors; The inductance is very small and can be counted; the resistance has little effect on the measuring capacitance, but the difference between the conductor and the steel strip and the connection of the capacitance is not significant, but it can be ignored; however, the stray capacitance has a greater influence and a test is done. : The capacitance between the intact core and the strip is 117nF, and the other cores are connected to the steel strip, the measurement result is still 117nF, and there is 72nF between the two cores.

Capacitor method to measure the break point of cable

For the convenience of explanation, it is assumed that the cable is a 2-core steel tape armor, in which 1 core has a breakpoint cable; the specific method is as follows:

1. Hang all insulated core conductors and armored layers at both ends of the cable.

2. Measure the capacitance values of the insulation core and the core insulation core to the steel strip (or the third core intact insulation core) at both ends and record the values; at this time, the corresponding ends of the intact insulation core are measured. Capacitance values should be very close; the sum of the capacitances at the ends of the same breakage core should be slightly larger than the intact insulation core capacitances at the same position, indicating that there is only one breakpoint, or multiple breakpoints, but the distance is very close; if both ends of the same breakage core If the capacitance value is less than the intact insulating core capacitance value at the same position, there are at least two breakpoints.

Note: Theoretically, if there is only one breakpoint or multiple breakpoints but very close, the sum of the capacitance values at both ends should be greater than the capacitance value of the intact insulating core in the same position, and how many will vary from cable to cable, see later theoretical analysis.

3. Comparing the capacitance values of the broken core insulation core with the intact insulation core, and obtaining the lengths of the two ends respectively, the length and the actual length may be different, and the next step will be corrected; but if the two cores are not armored, the cable cannot be used. Make corrections.

4. If the sum of the calculated lengths is greater than the actual length, the multi-out length value is negative, if it is less than the actual length, it is positive; and then the value of the capacitance value of the core insulation core is used to distribute the difference, and the length of the long section is modified. , Short paragraph to correct short section, then get the actual position of the breakpoint.

Henan Sanheng Cable Co., Ltd , founded in 2000, It is one of the top wire and cable manufacturers in China's wire and cable industry for nearly 20 years. the company has more than 5 production lines.

The production cable can be divided into more than 50 varieties and subdivided into 1000 specifications.All products have passed national certification, such as China compulsory certification, bv certification, Nigerian SONCAP certificate, China national industrial certification, etc. China national industrial production license, etc.It also has the ability to produce products that meet international standards, such as iec, ce, rohs, etc.
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