Sharing of closed fault location methods
Qilda's QLD-301Time Domain Reflectometer（TDR）, with 6 waveforms on the same screen, can simply and accurately determine the location of the fault point, making it easier to find the location of the hidden fault point. QLD8000 Underground Cable Route Tracer color screen compass, both live and dead cable paths can be queried, and the one key sounding function can measure the depth of 20m at most.
Sharing of closed fault location methods
What is a closed fault?
Closed fault refers to that at a certain position of the cable (especially in the middle or terminal head), the insulation layer of the cable is damaged due to some reasons (such as cable manufacturing defects, improper laying methods, environmental factors, etc.), but the outer sheath is not damaged, forming a relatively closed fault point. What
Will a closed fault affect the test?
During the closed cable fault test, the outer sheath at the fault point is not damaged, and the sound signal cannot be well transmitted to the ground during high voltage discharge; At the same time, the leakage current can not be leaked to the fault type on the ground. Therefore, special methods are needed to detect and locate such faults.
How to test this type of fault?
This kind of fault requires high accuracy of distance meter and path meter. Because most of these fault points cannot be directly and accurately located. Therefore, the indirect method is often used, which requires that the ranging error of the rangefinder should be as small as possible, the direction should be determined by the Pathfinder, and the cable fault location should be found by the sliding rule (refer to the measurement results of the rangefinder). In the pre positioned fault distance area, after excavation, the probe is pasted on the cable body, and the direction and distance of the fault point are determined by the acoustic magnetic time difference.
Enclosed cable fault test site (I)
Location: a community in the South Third Ring Road of Xi'an;
Cable type: 380V cross-linked cable fault location;
Cable burying method: 1.2m directly buried in the ground;
Fault type: closed fault (phase to phase flashover fault);
Instruments used:QLD-301Time Domain Reflectometer（TDR）,QLD-M50 Cable Fault Surge Generator,QLD-D30 Cable Fault Pinpoint Locator,QLD8000 Underground Cable Route Tracer.
Test process sharing:
（1） Understand the site conditions
Qilda's on-site technical engineer, MI Gong, arrived at the community with cable fault testing equipment. The cable in the community is a 380V cross-linked cable, which has been buried for more than 10 years. During the construction of green belt reconstruction in the community, the specific location of the cable is not clear, and the buried depth is basically about 1 meter.
（2）Determine the nature of the fault
The insulation resistance ABCN between phases of the faulty cable measured by 2500V electronic insulation resistance tester is 0.2m Ω, 0.2m Ω, 0.1M Ω and 0.5m Ω respectively, which can be used to judge the inter phase flashover fault of the cable.
（3）Test cable fault distance
The total length of the cable was 411.479 meters measured by the low-voltage pulse method of QLD-301Time Domain Reflectometer（TDR）, and the fault distance was 106.425 meters measured by the high-voltage charge flash method in conjunction with the QLD-M50 Cable Fault Surge Generator.
（4）Cable path finding and accurate fault location
Use QLD8000 Underground Cable Route Tracer to find the mark at 106m of the cable path, click one button to conduct sounding, and the buried depth of the cable is 1.2m. The acoustic magnetic mode of QLD-D30 Cable Fault Pinpoint Locator is used to accurately locate near the fault point. The sound is low during impulse discharge, and the technician cannot clearly mark the location of the cable fault point. Then excavate within the range of sound signal.
（5） Excavation, identification and repair
After the excavation of the fault point was confirmed, it was found that there were 5 cables here, and the surfaces of all cables were intact, so the fault cable could not be confirmed; At this time, use the QLD-S40 live cable identifier to identify the five cables, find the faulty cable after identification, and use the QLD-D30 cable fault locator to stick it on the surface of the faulty cable, accurately locate the fault point, and cut and repair it at the fault point.
Test summary
The site is directly buried cable, and the buried depth is about 1m. Under normal circumstances, the discharge sound at the fault point will be obvious. At that time, when using high voltage for impulse discharge, the sound was very small, and the location of the fault point was not clear. The technicians were experienced. They quickly judged that the fault point was a closed fault, and immediately decided to use unconventional methods to test. According to the fault distance tested by the Pathfinder, the approximate location was determined by the delay combination of the Pathfinder, excavation first, and then positioning. Repair again.
Qilda's QLD-301Time Domain Reflectometer（TDR）, with 6 waveforms on the same screen, can simply and accurately determine the location of the fault point, making it easier to find the location of the hidden fault point. QLD8000 Underground Cable Route Tracer color screen compass, both live and dead cable paths can be queried, and the one key sounding function can measure the depth of 20m at most.
Shaanxi Qilida Electronic Technology Co., Ltd. has been adhering to the concept of manufacturing high-quality pipe network (cable) fault tester, making the cable fault test simpler, more efficient and more accurate! To provide better service for customers at home and abroad, if you buy pipe network (cable) detection equipment, you can find Qilda.
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Shaanxi Qilida Electronic Technology Co.,Ltd