Comparative Synthesis Insulator Detection

    Synthetic insulators in our growing amount of failure is also increasing. According to incomplete statistics, as of 1998, in addition to lightning, bird damage and other external damage caused by synthetic insulator flashover outside, Guangdong, east, north and other regions are also many accidents (15 cases interface breakdown and 4 on the mandrel crisp off, 23 cases Flashover). Production processes and quality issues or silicone rubber relatively rapid aging also often makes the operation of the synthetic insulator failure. It is required to detect the operation of the synthesis charged insulator to find defects in advance, in time to prevent defects develop into an accident.

    At present, the detection of composite insulator live abroad is very active, mainly detection technology uses observation, ultraviolet imaging, infrared imaging method, the electric field method. These methods can achieve charged detection composite insulator, but each has limitations, choose one or more to adapt to circumstances, to facilitate the promotion of open synthesis method is tested regularly to monitor insulator prerequisites. Through laboratory and field running analysis comparing the advantages and disadvantages of several methods.

    1, observation

    This method is the most commonly used, the operator with binoculars in the tower can be detected, the main test of common surface defects (including insulated sheds erosion, roughening, flashover, cracking, corrosion of the outer layer has grooves and traces , cracked, broken, mandrel exposed, etc.). But generally smaller defect sizes, we need to see from a certain angle, only surface observation is not reliable enough, thus requiring a plethora of testing. And within an insulation fault often no abnormal appearance, relying on observation difficult to find. In addition, the operation for many years insulators prone to failure, and serious pollution of its surface area, almost turned black, so that the surface defects more difficult to find.

    At the beginning of filthy black cover no abnormal red silicone rubber, then washed with water to filthy red when exposed silicone rubber see a small hole. This hole was hidden for a long period of discharge charring channel formation.

    Visible defects may be due to the viewing angle is not ideal or filthy cover which can not be found. Inner insulation defects more likely because there is no obvious physical features are missing. Therefore, although very simple observation, but very reliable.

    2, ultraviolet imaging

    This method is used to detect small insulator that can cause serious erosion of the outer layer but stable surface partial discharge. PD by observing ultraviolet light emitted can be found in some of the defects. Past ultraviolet imager for night operation need to avoid the sun's ultraviolet rays. Israel is currently producing a UV imager avoid the sun's ultraviolet spectrum, which can be used during the day. Its camera lens with auto focus and other features, and also double imaged using visible and ultraviolet light, very easy to align the ground insulator pictures. A day in the laboratory a synthetic insulator surface defect occurs PD observed with the instrument screen, PD parts obvious shine.

    But not all defects have occurred PD. Some defects will occur only after the partial discharge moisture. Field operations, if the wires and equalizing ring corona, UV emitted may, after reflection of the lens, resulting in a lot of flashes of bright spots, to identify certain difficulties. Such instruments are expensive.

    3, infrared imaging

    This method is used to wire, connectors, casing and other heating detection and synthetic insulators abnormal local heating detection. The vast majority of insulating material damage caused by the electric field and temperature. Partial discharge, dielectric loss leakage current flows through the insulation material loss or resistance when the insulator can cause local temperature rise. Infrared observations issued by the local hot spots can be found in some of the defects. Currently available on the market weight of numerous infrared camera, the volume, operation similar to ordinary home video camera, easy to carry and operate, even on the insulator can carry up close pictures of the tower. Past effect similar instruments subject to sunlight during the day and can not be used. Now the high-end equipment can be used during the day, and the sensitivity of <1 ℃, the highest temperature value is automatically displayed.

    4, the electric field method

    This method is based on the longitudinal profile of synthetic insulators to determine the shape of the electric field within the dielectric breakdown of the insulator. When the insulator contain bugs, electric field here is more or less there will be some mutation. By observing the distortion of local electric field can be found in some of the defects. In general, within the insulation defects in appearance it is difficult to find, but the most dangerous. Now that the synthetic insulator seal bad or poor performance jacket, make moisture into the interior, causing charring passage occurs to produce the mandrel and sheath interface or mandrel PD. The charring channels only separated mandrel and jacket, and gradually develop along the mandrel so that the total length of the insulation is reduced. These discharges sometimes severe corrosion mandrels, mandrel causing fracture. At present, foreign insulators have been a few cases of synthetic insulation failure occurs, there have been some domestic problems.

    Insulation defects within continuity is bound to affect the electric field distribution around the insulator (including insulator along the mandrel longitudinal direction of the electric field and the radial electric field along the direction of the cross-sectional radius). Comparison of the measured and therefore the longitudinal electric field insulator and good insulators, identify abnormal distortion field position, that is to find, into the insulation defect location. North China Electric Power University and other units using this principle to develop a "DL-I-type synthetic Insulator detector. For the use of the longitudinal electric field distribution curve obtained by the instrument Figure l insulator electric field distribution curve is smooth good insulator. Insulators 11th 12 Just one look at the big umbrella hole, after stripping the outer cover, found a dozen cm long black charring channel on the mandrel. 4th umbrella at the appearance of a crack was found after ripping mandrel powder, yellow seen the test results are accurate and reliable.

    Electric field method using electric fields to detect insulators, can directly reflect the insulation condition of the insulator, and therefore less affected by interference. It detects only live above the detector along the insulator surface to slide again, to where the data is stored in the instrument. The data transfer is completed and then to detect computer or handheld computer, and displayed in the form of curves or data. The instrument is simple, straightforward, inexpensive, subject to registration and can not detect some of lever operation does not affect the field of external insulation defects such as sheds breakage. This method can be combined with observation.

    5. Conclusions

    Observation, ultraviolet imaging, infrared imaging method and the electric field method can detect synthetic charged insulator, but different main scope: observation method is suitable for external insulation defects; ultraviolet imaging method is suitable to produce partial discharge defects; infrared imaging method applicable to produce localized heating of the defect; electric field method is suitable for the defect in the insulation continuity.

    Inexpensive DL-1-type synthetic Insulator Detector costs are based on the principle of electric field detection method, direct detection, simple, accurate and reliable, more suitable for the country to promote the use.