Abnormal temperature rise of glass insulators is an important sign of internal defects or external faults (such as corona, local arc, internal moisture, deterioration of connection parts, etc.) during operation, which may lead to a decrease in insulation performance or even breakdown. Therefore, timely and accurate detection is crucial. The following are several main detection methods for abnormal temperature rise of glass insulators:
1、 Core detection principle
The temperature distribution of a normally operating insulator string should be relatively uniform and not significantly different from the ambient temperature rise. When there is an abnormal temperature rise (usually manifested as a "thermal imaging" anomaly or a point with a significantly higher temperature than the adjacent area), it indicates that there is an abnormal increase in power loss at that location.
2、 Main detection techniques and methods
1. Infrared thermal imaging detection (currently the most mainstream and efficient method)
This is a trustworthy merchant technology for non-contact, long-distance, and large-scale screening of abnormal temperature rise.
Working principle: Use an infrared thermal imager to capture the infrared radiation on the surface of insulator strings and convert it into a visual temperature distribution map (thermal image).
Abnormal features:
Localized overheating: A significant high temperature point or hot zone appears locally on the steel cap, steel foot, or glass component of a certain insulator. Possible reasons: Internal interface degradation, excessive contact resistance of metal connectors (such as rusting of locking pins, poor ball and socket fit), severe local contamination leading to concentrated leakage current.
Abnormal overall temperature difference: The temperature distribution of the entire string of insulators is significantly different from that of adjacent normal strings, or there is a significant difference in temperature from the environment.
Advantages: Safe, effective, power free detection, intuitive imaging, and the ability to detect early hidden defects.
Key points:
The testing should be conducted on clear, rainless, low wind speed nights or cloudy days to avoid interference from sunlight reflection and uneven heat dissipation.
It is necessary to set an appropriate emissivity and consider the effects of environmental temperature, humidity, and measurement distance.
The experience requirements for the testing personnel are high, and they need to be able to accurately identify abnormal thermal imaging patterns.
2. UV imaging detection
Used to detect discharge activity accompanied by temperature rise, it is an important supplement to infrared detection.
Working principle: Capture the ultraviolet signals generated by corona discharge and surface arc, and convert them into visible light images overlaid on visible light videos.
Abnormal features: Dense ultraviolet light spots or streamers are observed on the surface of insulators or at the connection of metal fittings, indicating the presence of strong partial discharge. This discharge generates heat, which is highly correlated with the temperature rise point.
Advantages: It can directly "see" the discharge phenomenon, accurately locate the discharge point, and is particularly suitable for detecting surface pollution discharge, metal tool corona, etc.
Limitations: It usually needs to be carried out in weak ambient light (such as at night), and the detection ability of weak discharges is greatly affected by distance.
3. Live detection (contact or close range)
Leakage current detection: Use a clamp ammeter or a one-to-one sensor to measure the grounding leakage current of the insulator string. Abnormal temperature rise is often accompanied by an increase in leakage current or the appearance of pulse current. But this method is greatly affected by the environment and is usually used for trend analysis or important monitoring.
Electric field distribution measurement: Use an electric field measuring instrument to measure the axial electric field distribution along the insulator string. Insulators with defects (such as zero value insulators) will change the voltage they share, resulting in distortion points on the electric field distribution curve, which are often accompanied by abnormal temperature rise.
Drone mounted detection: Combining the above-mentioned non-contact technologies (infrared, ultraviolet), using drone mounted detection equipment for optimized inspection, especially suitable for sections with complex terrain and difficult to reach manually, is the mainstream direction of future intelligent operation and maintenance.
4. Traditional manual inspection (auxiliary means)
Visual inspection: Although it is not possible to directly "see" the temperature rise, signs related to the temperature rise can be observed, such as:
Glass component self explosion: This is the most extreme "fault display" method for glass insulators. The self explosion itself may be the result of long-term internal defects leading to uncontrolled temperature rise, and it is also a prompt for subsequent inspection of adjacent insulators for abnormalities.
Corrosion and burn marks on metal parts: Overheated burn points, discoloration, or severe corrosion on metal fittings are visual evidence of abnormal temperature rise that has occurred or is currently occurring.
Abnormal sound: Close to auscultation, severe discharge may be accompanied by a "hissing" or popping sound.
3、 Testing process and judgment suggestions
Regular general testing: Use infrared thermal imaging cameras to conduct periodic surveys of power lines and establish baseline thermal imaging records for insulator strings.
Abnormal discovery: By comparing historical data with adjacent normal strings, identify insulators with excessively high temperature values, large temperature differences, or abnormal thermal imaging patterns.
Comprehensive analysis:
Combined with UV detection: Conduct UV review on suspicious points detected by infrared to confirm the presence of active discharge.
Combining environment and load: Analyze whether anomalies are related to recent weather (fog, rain, dew), pollution events, or load changes.
Identifying fault type: Based on the thermal imaging location (steel cap, steel foot, middle of glass body), preliminarily determine whether it is a connection fault, internal fault, or surface contamination fault.
Classification processing:
General abnormality: Strengthen monitoring and prioritize it in the next inspection.
Serious abnormality: Further confirmation by combining other detection methods (such as live detection of electric field distribution).
Critical defects (such as rapid temperature rise accompanied by strong discharge) should be reported immediately, and a power outage replacement plan should be planned.
