Fault finding of power cables is generally divided into four steps: fault diagnosis, fault location, path detection, and fault location. Fault location methods mainly include: First, the bridge method, which mainly includes the traditional DC bridge method, voltage drop comparison method, and DC resistance method; and secondly, low-voltage pulse method, also known as radar method, is passed through the instrument at one end of the cable. A low-voltage pulse signal is input to the cable. When a fault point with a mismatched impedance is encountered, the pulse signal is reflected and returned to the measuring instrument. This method has the advantages of simple operation and high test accuracy. It is mainly used to test the breakage and low resistance faults, but it cannot test high resistance faults and flashover faults; the third is the pulse voltage method, which needs to apply DC high voltage to the faulty cable. Signal; four is the pulse current method, the need to apply DC high-voltage signal to the fault cable; five is the second pulse method.
The main reason for the failure of street lamp low voltage cable
1, external damage
Due to the irregularity and arbitrariness of road construction and other pipeline constructions, it is often the case that the street light cables are cut off or damaged. Moreover, most of the construction units do not notify the street lamp management department to re-bury them after digging out the street light cables. The resulting damage to the cable can cause complete damage to the cable after a period of operation.
2, long-term overload operation of the cable
Due to the lack of design, the lack of "double weight" of the cable size, unbalanced three-phase load, and arbitrarily increasing the load, the long-term overload operation of some cables leads to an increase in the temperature of the cable, especially in hot conditions. In summer, the temperature rise of the cable often leads to the weaker point of the cable and the first breakdown at the joint. In summer, the reason for the high rate of cable failure is just this.
3, poor quality of cable construction
Barbaric construction, illegally dragging the cable, can cause damage to the cable skin. After several months or even years, moisture infiltrate, and the degree of insulation is reduced, resulting in complete breakdown of the damaged part. In addition, cable joints are weak links in cable lines. During the process of making cable joints, if the joints are not tightly crimped, loosely packed, and poor heat shrinkage quality, etc., the insulation of the cable ends will be reduced, causing failures. happened.
Square Hopper Scale
Summary:
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Main uses:
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SHANDONG JINZHONG SCIENCE & TECHNOLOGY GROUP COMPANY LIMITED , https://www.chinagoldbell.com