What Are the Principles and Advantages of High Voltage Bridge Method

What is a high voltage bridge? Designed based on the principle of Murray bridge, it is applicable to the location of breakdown points (low resistance, high resistance and flashover breakdown) of various wires and cables after laying and points without breakdown but with low insulation resistance: for example, the insulation defect points with low cable resistance but without breakdown under operating voltage are found with a megger. Of course, it can also be used to locate the defect points of various cables in the cable factory. There are two methods of cable fault location in rough measurement: electric bridge method and wave reflection method. At present, wave reflection locator is more popular. Its disadvantages are: the field wiring of some instruments is complex and there is a positioning blind area. When the waveform is not typical, the positioning personnel are required to master the instrument and be experienced to distinguish the pulse waveform. There are several cable faults that are difficult to find by wave reflection method: for example, insulation defect points of high-voltage cable sheath, steel tape armored low-pressure cable, PVC cable, no reflected wave, unable to locate. Short cable, unable to locate. Some high breakdown points cannot be broken down under impulse voltage and are difficult to locate. The high-voltage bridge cable fault tester contains a high-frequency, high-voltage and constant current source, which solves the interference problem of the power supply to the high-sensitivity amplification of the bridge. The power supply and the bridge are integrated. The measuring cable is a special high-voltage cable, which adopts the resistance measurement principle of four terminal method, with high positioning accuracy. The bridge is placed on the high voltage side and the operating button is safely grounded. The limitation of the bridge method for high resistance positioning is solved, and the characteristics of no blind area, accuracy and convenience of the bridge method can be brought into play. Murray principle in high voltage bridge: Murray in Chinese means Wheatstone, Wheatstone bridge (also known as single arm bridge). The universal Wheatstone bridge resistors R1, R2, R3 and R4 are called the four arms of the bridge. G is the galvanometer to check whether there is current in the branch where it is located. When G has no current, it is called that the bridge is balanced. When balancing, the resistance values of the four arms meet a simple relationship, which can be used to measure the resistance. When G has no current, it is said that the bridge reaches balance. When balancing, the resistance values of the four arms meet a simple relationship. Using this relationship, the resistance of Murray bridge can be measured. Advantages: 1. Murray bridge balancing method has no test blind area, which is used to judge the short cable and the breakdown point near the cable end. 2. Murray bridge method only requires the uniformity of cable phase resistance. Cables with poor traveling wave transmission characteristics, such as PVC low-voltage cables with large dielectric loss, can effectively judge the short cable and the breakdown point near the end by combining the current source with Murray bridge technology, so that steel tape armored low-pressure cables and PVC cables can have positioning and no blind area search.

What Are the Principles and Advantages of High Voltage Bridge Method 1

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