Friday, May 20, 2011

【 Weak current College 】 infrared thermal imaging in electrical equipment fault detection 】

Power equipment failure there are many and varied, but most are associated with fever. From infrared diagnostic perspective, usually divided into external and internal failure. We all know, power system operation, the current import experience because the current effect produces resistance loss in power transmission of the entire circuit on the myriad of connectors, connector or contact. Ideally, the transmission circuit in various connectors, connector or contact contact resistance is lower than some of the resistance connected to the conductor, connection parts for wear fever no faster than the adjacent conductor of heat, but once some connectors, connector or contact caused by poor connection, increasing contact resistance, the site will have more resistance losses and higher temperature rise, resulting in overheating. This class is typically a external failures.
External fault characteristics: high temperature, easy-to-local infrared camera found, if not timely processing, deteriorating fast, easy form accident, causing the loss. External failure accounts for a greater proportion of fault.
The so-called high-voltage electrical equipment, internal failure, mainly refer to the enclosed in the solid insulation material and device shell internal electrical circuit failures and insulation deterioration caused by a variety of failures. Because such a failure in the electrical equipment, and therefore reflect internal device appearance of temperature rise is very small, usually only a few K. Detection of such failures to detect devices require a higher sensitivity.
Internal failure characteristics: the proportion of small, temperature fault, damage, and on the infrared detection equipment requirements.
According to the relevant unit offered long-term measured data and a large number of cases of comprehensive statistics, external heat power equipment accounted for equipment defect defect general overall average of 90% ~ 93%, internal heat defect only7% to 10%.
In the electric power industry, very early on the thermal imager for device security overhaul, through its electrical equipment and wiring for detection of defects, such as transformers, bushings, circuit breaker, switch, transformer, electrical capacitors, lightning, power cable, straps, cables, switchgear, low-voltage electrical insulator strings, as well as current, voltage caused by heat or other thermal effect of equipment of secondary circuit, this timely detection, treatment, prevention of major accidents can play a very crucial and effective role.
The so-called thermal electric devices, commonly referred to by some means of detection, because of its intrinsic or extrinsic reasons caused by the phenomenon of fever.
According to the causes of defects, we are usually categorized into 3 types: one is the long-term exposure to air, due to the influence of temperature and humidity, or surface dirt and bad, or due to external effects arising from the injury, making part of conductive cross-sectional area to reduce the fever. If the connector, bolts, washers not pressed; long running corrosion oxidation; the atmosphere of active gas, dust, corrosion; components caused by bad installation materials, processing technology is not good cause conductor damage; mechanical vibration and other causes of conductor actual section lower; load current instability or exceeded.
The other type is due to electrical failure, such as inner itself internally connected parts is bad cause excessive resistance; insulating materials aging, cracking, peeling; internal component gets wet, pieces loss increment; cooling medium pipeline block, and so on.
For those who can directly observed equipment and pieces, infrared camera will be able to find all the connection points of vulnerability. For those who were unable to due to be screened directly see section, you can pass under its heat to the outside parts of the analysed thus concluded. Due to the ever-changing field of reality, even if you pass the thermal imager is a piece of a hot picture, if you want to make an accurate judgement, may be affected by many factors. As the current temperature, air flow, load, and so on. We can according to different characteristics, as related to analysis, to determine if:
In order to guarantee secure and efficient operation of electricity production, electricity equipment state maintenance set higher requirements. As a condition-based maintenance depends on the State of a running device detection and online monitoring tools, electric power equipment running status detection and monitoring the production of the electrical safety has always played an important role. Infrared imaging technology as a new technology, electric power equipment running detection has incomparable advantages. Infrared imaging is a device of the hot state distribution on devices running good or not for diagnosis, it has not stopped, non contact, distance, speed, visually on the equipment of hot for Imaging. Because device of thermography is a device running hot and temperature distribution in a true depiction, and power equipment in operation of heat distribution is normal or not in good enough condition to determine the device or one of the important characteristics, thus. Using infrared imaging technology can device thermography of analysis to diagnose the status of the device and its hidden defects.
Using infrared imaging technology to carry out the following electrical equipment condition monitoring and fault diagnosis.
● High-voltage electrical equipment operating status detection and internal and external Center Troubleshooting:
● Various conductive connectors, connector, wiring, corrosion and oxidation of pile head connected defects;
• Various types of high-voltage switches Center contact bad defects;
• Isolated knife, knife and touch tablet, as well as rotating CAP and ball head with undesirable defects;
● Various CT once outside the Centre in the Centre and connected defects, ontology and oil insulation defects as well as within the Center core, coil exception bad heat sink;
● Various PT insulation bad defects, lack of oil, as well as within the Center core, coil exception bad overheating faults;
● Various capacitors overheating, coupling capacitor oil insulation bad and the lack of oil (low oil level) defect;
● Various shortcomings in the center of moisture surge arresters, Center component aging or defects caused by nonlinear characteristics;
● Various insulators surface defects, polluted insulators detection, detection of vases; deteriorating
● The generator running detection, brushes and rings for contact status detection, overheating detection in the Centre;
● Power transformer box abnormal overheating overheating, Eddy current, high and low pressure casing on both ends of the connection, as well as the poor lack of oil oil casing (low oil level) defects;
• All types of motor bearing bad, and the in vivo Center abnormal overheating

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