As core equipment in power systems, cylindrical transformers are widely used in key scenarios such as new energy grid connection, urban power grid expansion, and industrial load power supply, leveraging advantages including low loss, low noise, and strong short-circuit resistance. The stability of their operating status is directly related to the safe and economic operation of power systems. This article systematically sorts out the common fault types of cylindrical transformers, proposes targeted preventive measures, and introduces the current mainstream advanced diagnostic technologies to provide technical reference for equipment operation and maintenance.
I. Common Fault Types
Combined with the structural characteristics of cylindrical transformers (such as integrated windings and new insulating materials) and actual operating conditions, their common faults are mainly concentrated in core components such as windings, insulation, cooling systems, and accessories, specifically as follows:
(I) Winding Faults
Windings are the core components of cylindrical transformers for electrical energy conversion. Common faults include winding deformation, inter-turn short circuits, and winding overheating. Among them, winding deformation is mostly caused by impacts during transportation and electrodynamic forces generated by short-circuit faults, manifested as axial or radial displacement of windings and coil deformation; inter-turn short circuits may be triggered by insulation aging, winding process defects, overvoltage impacts, etc., leading to a sudden increase in local coil current and subsequent overheating damage; winding overheating is mainly caused by long-term overload operation, poor heat dissipation, or excessive contact resistance. Long-term overheating will accelerate insulation aging and shorten the service life of the equipment.
(II) Insulation Faults
Cylindrical transformers mostly adopt new insulating materials, but their insulation systems still face problems such as aging, moisture absorption, and partial discharge. Insulation aging is closely related to operating temperature and ambient humidity. Long-term high-temperature environments will cause the performance of insulating materials to degrade, and even cracking and carbonization; insulation moisture absorption is mostly caused by moisture intrusion due to poor sealing, resulting in a decrease in insulation resistance and triggering leakage or breakdown faults; partial discharge is an important precursor to insulation degradation, mostly occurring in weak parts such as winding ends and insulation joints. Long-term partial discharge will gradually erode insulating materials, eventually leading to insulation failure.
(III) Cooling System Faults
The normal operation of the cooling system is crucial to ensuring the stable work of cylindrical transformers. Common faults include cooling fan failures, oil pump failures, and radiator blockages. Cooling fan or oil pump failures will cause poor circulation of cooling medium, reduced heat dissipation efficiency, and thus an increase in transformer oil temperature; radiator blockages are mostly caused by the accumulation of environmental dust and oil stains, which also affect heat dissipation effects and trigger equipment overheating alarms.
(IV) Accessory Faults
Transformer accessory faults mainly include bushing faults, tap changer faults, gas relay faults, etc. Bushing faults are manifested as contamination, cracking on the bushing surface, or internal insulation damage, which may trigger flashover discharge; tap changer faults are mostly caused by poor contact and mechanical jamming, which will result in voltage regulation failure or local overheating; gas relay faults may cause protective maloperation or refusal to operate due to internal oil ingress and contact adhesion, failing to respond to internal faults in a timely manner.
II. Preventive Measures
In response to the above common faults, it is necessary to formulate preventive measures from the whole life cycle links such as design and manufacturing, transportation and installation, and daily operation and maintenance to build a comprehensive fault prevention and control system:
(I) Optimize Design and Manufacturing Processes
In the design stage, winding materials, insulating materials, and cooling methods should be reasonably selected according to operating conditions, the mechanical strength design of the winding structure should be strengthened to improve short-circuit resistance; during the manufacturing process, strictly control the winding precision and insulation wrapping quality, strengthen the control of sealing processes to prevent moisture and impurities from entering; rigorous performance tests should be completed before leaving the factory to ensure that all indicators of the equipment meet the standard requirements.
(II) Standardize Transportation and Installation Processes
Adopt special shockproof packaging during transportation, control the transportation speed and jolt amplitude to avoid winding deformation; conduct a comprehensive inspection of the equipment before installation, clean the contamination on the accessory surface, and verify the foundation flatness and installation dimensions; strictly perform wiring and sealing processes in accordance with operating procedures during installation to ensure that accessories such as tap changers and bushings are firmly installed and in good contact; conduct insulation tests, no-load tests, etc., after installation to verify the installation quality.
(III) Strengthen Daily Operation and Maintenance Management
Establish a normalized inspection mechanism, regularly check the operating status of the transformer such as oil temperature, oil level, sound, and odor, and timely clean the dust and oil stains on the radiator surface; regularly carry out insulation resistance testing and oil quality analysis (such as testing indicators such as moisture, dielectric loss, and breakdown voltage) to grasp the status of the insulation system; reasonably control the load operation to avoid winding overheating caused by long-term overload operation; strengthen protective measures for harsh environments (such as high temperature, high humidity, and high dust), such as installing dust covers and dehumidification equipment.
(IV) Improve Protection and Early Warning Mechanisms
Configure complete relay protection devices, such as gas protection, longitudinal differential protection, and overcurrent protection, to ensure that the power supply can be cut off in a timely manner when a fault occurs and reduce fault losses; install online monitoring equipment to real-time monitor key indicators such as oil temperature, oil level, and partial discharge, set early warning thresholds, and realize early warning of fault precursors.
III. Advanced Diagnostic Technologies
With the upgrading of power operation and maintenance technology, traditional offline diagnostic methods can no longer meet the refined operation and maintenance needs of cylindrical transformers. A number of advanced online diagnostic and intelligent analysis technologies have been gradually applied to realize early fault detection, accurate positioning, and status evaluation:
(I) Online Partial Discharge Monitoring Technology
This technology collects ultrasonic signals and ultra-high frequency electromagnetic signals generated by partial discharge inside the transformer in real time by installing equipment such as ultrasonic sensors and ultra-high frequency sensors, and combines signal processing algorithms (such as wavelet analysis and neural networks) to denoise, identify, and locate the signals, so as to judge the intensity, location, and development trend of partial discharge. Compared with traditional offline detection, its advantage lies in realizing 24-hour uninterrupted monitoring, timely capturing early signals of insulation degradation, and providing accurate basis for insulation fault prevention.
(II) Online Monitoring Technology for Dissolved Gases in Oil
Internal transformer faults (such as winding overheating, insulation aging, and partial discharge) will cause the decomposition of insulating oil to generate characteristic gases (such as methane, ethane, ethylene, acetylene, etc.). This technology collects the composition and content of dissolved gases in oil in real time through online monitoring devices, and judges the fault type and severity in combination with diagnostic standards such as the "Three-Ratio Method". For example, a sudden increase in acetylene content usually indicates an arc discharge fault, and an increase in ethylene content may correspond to winding overheating. This technology can realize early fault warning and avoid further expansion of faults.
(III) Online Winding Deformation Diagnosis Technology
The online winding deformation diagnosis technology based on Frequency Response Analysis (FRA) monitors the frequency response characteristics of the winding by injecting excitation signals of specific frequencies into the winding. When the winding is deformed, its equivalent circuit parameters (inductance, capacitance) will change, leading to the deviation of the frequency response curve. By comparing the frequency response curves of the equipment in normal state and operating state, it is possible to accurately judge whether the winding is deformed and the degree of deformation. This technology does not require power outage, can realize normalized monitoring of winding status, and makes up for the deficiency that traditional offline detection requires power outage.
(IV) Infrared Thermal Imaging Diagnostic Technology
Infrared thermal imagers are used to detect the temperature of key parts of cylindrical transformers such as windings, bushings, and tap changers, and the temperature distribution of the equipment is intuitively presented through thermal images. When the equipment has faults such as poor contact, winding overheating, and insulation aging, abnormal high-temperature areas will appear in the corresponding parts. This technology has the advantages of non-contact, visualization, and fast detection speed, and can be used for rapid fault screening in daily inspections to timely find thermal defects of the equipment.
IV. Conclusion
Fault prevention and precise diagnosis of cylindrical transformers are key links to ensure the safe and stable operation of power systems. By mastering common fault types, implementing full-life-cycle preventive measures, and applying advanced diagnostic technologies, the level of equipment operation and maintenance can be effectively improved, the fault occurrence rate can be reduced, and the service life of the equipment can be extended. In the future, with the continuous integration of intelligent and digital technologies, the diagnosis and operation and maintenance of cylindrical transformers will develop in a more precise, efficient, and intelligent direction, providing a more solid guarantee for building a new power system.
