Company Name: Henan Xinchaoda Cable Co., Ltd.
Contact: Manager Guo
Address: Xibaishui Village, Xitao Town, Wuzhi County
Marketing Center: 1812, Building B, Building 3, Shenglong Plaza, Zhengdong New District, Zhengzhou
Indirect short circuit or broken wire faults can be measured and judged indirectly with a multimeter. Use a megohmmeter to measure the insulation resistance between the core wires or the insulation resistance between the core wire and the ground. The type of the fault can be determined according to its resistance value. After the type of obstacle is determined, finding the faulty point is not an easy task. Based on the author's experience, the above introduces several methods to find the faulty point.
1.How to find the faulty point of the cable
(1) Sound measurement method: The so-called sound measurement method is to stop the search based on the sound of the faulty cable discharge. This method is relatively ineffective for the high-voltage cable core wire to the flashover discharge of the insulation layer. The equipment used in this method is a DC withstand voltage tester. In the faulty place, the cable core wire discharges the sound of "nourishment and nourishment" to the insulation layer. For the laying of the cable, you can indirectly find it by hearing. If it is a buried cable, you must first determine and indicate the direction of the cable. At very low levels, stop searching with audio reduction devices such as deaf hearing aids or medical stethoscopes. When searching, hold the pickup close to the air and move it along the cable gradually. When you hear "Zi, Zi" the discharge sound is extremely loud, this is the fault point. When using this method, we must pay attention to safety, and special personnel should be set up at the end of the experimental equipment and the cable.
(2) Bridge method: The bridge method is to use a two-arm bridge to measure the DC resistance of the cable core wire, and then accurately measure the actual cable length, and calculate the fault point according to the inverse proportional relationship between the cable length and the resistance. In this method, the fault of the indirect short circuit between the cable core wires or the contact resistance of the short-circuit point is less than 1Ω, and the error is usually not greater than 3m. For the fault of the fault point, the contact resistance is greater than 1Ω, and the resistance can be reduced to 1Ω by increasing the voltage. Hereafter, follow this method to measure.
The measurement steps are as follows:
① Connect the battery E on the core wires of phase b and c first, and then lay an analog wire S equal to the length of the faulty cable in the air. The wire should be bare copper or bare aluminum. The cross section should be equal. There are two connectors.
② Ground the negative pole of the microvoltmeter, and connect the positive pole to a longer flexible lead. The other end of the lead should be able to make sufficient contact when sliding on the comparable lead.
③ Close the knife switch K, slide the end of the flexible wire on the analog wire, and the position when the microvolt meter indicates zero is the position of the faulty point of the cable.