The generation of wire and cable fault test is caused by the laying and application of cable. The accurate positioning of cable fault test varies with the laying method of cable, and the difficulty coefficient of accurate positioning is gradually increasing. Among them, the accurate positioning and search of cable bridge, tunnel construction and ditch open matching method are relatively simple, while the accuracy and search coefficient of direct buried method is relatively difficult. When the common fault characteristics are simple, the special cable fault test accurate positioning machine equipment can be accurately positioned within tens of minutes, and when the common fault is unique, it usually takes 4-5 days or even longer to carry out the accurate positioning of common faults.

Some methods for accurate location of cable fault test

In the use of radar echo method to carry out accurate positioning of cable fault test, sometimes according to the migration of common fault phase, wiring method, usually complex common faults will be changed into simple common faults, quickly clear the common fault location, and obtain time for the maintenance of the spot route, which is of great practical significance for the application unit of the power supply system.

Low-voltage wire and cable are generally multi-core cable lines, and after common faults occur in continuous application after laying, they generally show two-core and multi-core two-color or relative short-circuit faults. Sometimes, when the common fault wave pattern collected by a certain core is not idealized, it can be considered to transform the wiring to other common fault cores to carry out common fault wave pattern inspection, which usually has unexpected practical effects, and the wave pattern collected and tested will become more and more typical and standard, so that the specific address of the cable fault test point can be quickly defined.

Long-term cable customers found in the entire process of accurate measurement on the spot, small cross-section copper core buried wire and cable (35mm2 and the following) and aluminum core cable common faults, it is likely that at the same time with short circuit fault and disconnect common faults, on-site inspection, According to the different common fault characteristics of each common fault core, the common fault of short circuit fault is transformed into the common fault of disconnecting the accurate measurement, which is usually half the result with twice the effort.

For the medium voltage directly buried wire and cable with extruded armored cable lining, most of the common faults are caused by external mechanical equipment damage, and the lining layer is likely to have been damaged at the same time when the insulated cable core produces common faults. When the common faults of the cable insulation layer are more unique, it is difficult to collect the wave pattern using a professional cable fault tester. Consideration can be given to the use of acoustic measurement to immediately increase the high voltage pulse in the middle of the strip and copper shielding layer of the cable line, usually quickly specified.

In the field of accurate measurement of the whole process, in the use of acoustic measurement method to carry out the common fault designation of cable lines, the high voltage wire and ground wire in the bad phase and metal material shielding or sheathed cable in the middle, because the grounding resistance of the two shows a low resistance gold property connection, the sound is not large, can not use cameras to monitor the designation, the actual effect is not ideal. According to the specific listening side on the spot several times, it was found that the distance between the charge and discharge ball gap was moderately increased, and at the same time, the high voltage and wire connector were changed to the middle of the two phases that produced common faults, usually the charge and discharge sound would increase, and the common fault point was quickly defined.

A quick and accurate way to locate cable fault test points

The method of accurate positioning of the wire and cable fault test point, in which the total length of the common fault cable is already known data information, its characteristics depend on the following process: remove the load on the common fault cable, separate the two sides of the wire core, And suspended in the air, with the above common fault cable at one end of the part as the detection point; The digital display insulation layer insulation tester is used to accurately measure the separation between each core and the indirect resistance between each core and the shielded strip steel, and then identify the common fault core, that is, the core of the common fault. Then accurately measure the resistance between common fault cores and the resistance between each common fault core and the shielded strip. Is the resistance measured less than or equal to 1? kΩ, select the cable fault test accurate positioning bridge circuit and wave reflection surface cable fault test detector to accurately measure any common fault core to clarify the cable length value between the common fault point and the detection point, and then identify the common fault point location; If the distance between the common fault points measured by the two devices exceeds the output accuracy distance, then the detection result of the wave reflector cable fault detection instrument is used as the standard, and if the distance is less than or equal to the output accuracy distance, the category in the middle of the common fault points measured by the two devices is defined as the category of common fault points. If the measured resistance is more than 1kΩ, the wave reflector cable fault test detector is used to accurately measure any common fault core to clarify the cable length value between the common fault point and the detection point, and then identify the common fault point location, and the common fault point location is the center point, the output accuracy interval is half longitude, and the common fault point category is clear; The measured resistance measurement size is different, the use of wave reflector cable fault test detector accurately measure any common fault lithium cell to clear the common fault point and the detection point between the cable length value, and then clear the common fault point location, and for this common fault point location is the center point, the output accuracy spacing is half longitude, clear the common fault point category; The above output accuracy spacing is 5m; c) Use the cable fault test to accurately locate the switching power supply at the detection point to increase the single pulse operating voltage between the common fault core or between the common fault core and the strip; In the scope of common fault points identified in process b), find the exact parts of common fault points according to sound discrimination or apply the cable fault test designator. In the scope of common fault points identified in process b), search the exact parts of cable fault test points by using the acoustic-magnetic synchronous walking method.

Search method of cable fault test point:

1. Low voltage monopulse method (commonly known as monopulse method)

When a monopulse electromagnetic wave is input to the line, the monopulse is transmitted along the way at the rate V. When the Lx distance of the line meets the common fault point, it is returned by the reflector to the input end, and the round-trip time is T, and V is the rapid propagation of electromagnetic wave in the line, which is related to the main parameters of the line. For each kind of line, it is a value. It can be obtained according to calculation and evaluation of DFDL-S cable fault test detector. The transmitting monopulse of the monopulse source and the reflecting surface wave of the common fault point of the route are displayed on a display screen, and the time T can be measured by the clock signal given by the instrument.

The low inductive load grounding device and short circuit fault of the cable line are common faults and disconnecting common faults, and the punching method can easily measure the common fault spacing. However, for the common failure of high inductive load, because of the high characteristic impedance under the low-voltage monopulse effect, the reflective surface wave is not significant or even no reflective surface. In this case, it is necessary to add a certain DC high voltage power supply or impact high voltage to charge and discharge it, and use short circuit fault arc to produce an instant short circuit fault resulting in electromagnetic wave reflection surface.

2. Dc high voltage power short circuit fault method (commonly known as direct flash method)

When the common fault resistor is very high, before the smooth resistor safety channel is generated, a gradually rising AC voltage can be applied to the cable under test. After a certain operating voltage value, the common fault point is preferably penetrated, resulting in a short circuit fault. The working voltage added by the short circuit fault arc pair is used to generate a short circuit fault reflector, and the reflector radar echo is generated by a high resistance source at the key end. In this way, the operating voltage will reflect the surface several times between the input end and the common fault point until the kinetic energy has disappeared.

3. Impact high voltage short circuit fault method (commonly known as flash method)

When the common fault resistor is reduced, the stable resistor safety channel is generated, and the DC high-voltage power supply cannot be added due to the volume limitation of the machine equipment, it is necessary to change to the impact operating voltage detection. The DC high-voltage power supply charges the cable battery through the sphere gap until it penetrates, and still uses the short-circuit fault arc generated by it to cause the short-circuit fault reflection surface. An inductor L should be accurately measured at the wire and cable input end to load radar echoes. Its basic principle route is shown in Figure 4, the electromagnetic wave is short-circuited fault reflector at the common fault point, and L-reflector at the input end, during which several reflectors will be generated. Due to the self-inductance phenomenon of the inductor L, the guide reflector is gradually displayed because of the choke effect of L, and the short-circuit fault reflector is displayed after a certain period of time with the increase of current flow. The whole route is composed of capacitor C and inductor L to form a complete L-C charging and discharging process. Therefore, the whole wave process displayed at the input end of the line is a cosine curve approaching the attenuation coefficient with rapid monopulse multiple reflector waves. The spacing of common faults can be obtained from the spacing of reflective surface waves.

Qingdao Tianxing Cable Co., Ltd. focuses on the production of customized wire and cable manufacturers, main: fire wire and cable, power cable, control cable and other products, exported to more than 40 countries and regions around the world, the annual production capacity of 1 billion yuan. 6000 square meters of storage, standing hundreds of millions of inventory, order demand for rapid distribution and delivery, large prices more favorable. Hotline: 16678668098