What Is The Purpose Of A Power Transformer?

A: Overheating is one of the most common faults of power transformers, mainly caused by the following factors: long-term overloading operation (exceeding the rated capacity, leading to excessive winding copper loss); poor cooling system performance (such as blockage of cooling oil circuit, failure of cooling fans or oil pumps); insulation deterioration (increasing dielectric loss and generating heat); poor contact of tap changers (causing local resistance increase and heat generation); and core defects (such as core multipoint grounding, leading to eddy current loss increase). Excessive temperature will accelerate insulation aging and even cause insulation breakdown, seriously affecting transformer life and operation safety.

A: The global mainstream power transformer standards are mainly formulated by the International Electrotechnical Commission (IEC) and the Institute of Electrical and Electronics Engineers (IEEE)/American National Standards Institute (ANSI). The IEC 60076 series is the global benchmark, covering general requirements (IEC 60076-1), temperature rise limits (IEC 60076-2), insulation levels (IEC 60076-3), short-circuit withstand capacity (IEC 60076-5) and other core contents. IEEE C57 series is widely used in North America, including general specifications (IEEE C57.12.00) and DGA fault diagnosis guidelines (IEEE C57.104). In addition, China’s GB 20052 and the European Union’s Ecodesign Directive are important regional standards focusing on energy efficiency and environmental protection requirements.

A: The correct selection of transformer capacity needs to be based on the actual electrical load and its development trend, following the principle of “matching load and avoiding excessive or insufficient capacity”. First, calculate the total calculated load (considering the load coefficient of various electrical equipment and simultaneous operation rate). On this basis, reserve 10%-20% of the margin to cope with future load growth. If the capacity is too large, it will lead to long-term light-load operation, increase no-load loss, reduce power factor, and cause economic waste; if the capacity is too small, the transformer will operate overloaded for a long time, resulting in overheating, accelerating insulation aging, and even damaging equipment. For scenarios with large load fluctuations, it is recommended to configure multiple transformers for parallel operation to improve operational efficiency.

A: The intelligent development of power transformers is mainly reflected in three aspects: first, full-dimensional state monitoring, which embeds sensors for online monitoring of winding temperature, partial discharge, core grounding current, oil quality and other parameters; second, digital integration, which supports IEC 61850 and other digital communication protocols, realizing remote monitoring, data uploading and cloud analysis; third, predictive maintenance, which uses AI and machine learning algorithms to analyze monitoring data, predict potential faults and remaining life, and convert from “planned maintenance” to “predictive maintenance”. In addition, the application of digital twin technology (building virtual models to simulate operation status) is also an important development direction, which can optimize design and operation strategies.

A: Common winding faults include insulation breakdown, short circuit (turn-to-turn, inter-winding, winding-to-ground), and open circuit. The main causes are manufacturing defects (such as uneven winding), mechanical stress (from transportation, installation or short-circuit impact), insulation aging (caused by long-term high temperature), and moisture ingress. Preventive measures include: strictly controlling the manufacturing and installation quality to ensure winding tightness and insulation integrity; avoiding excessive short-circuit current impact (configuring appropriate protective devices); regularly testing insulation performance (such as insulation resistance, dielectric loss test); and maintaining a dry and clean operating environment to prevent moisture and pollution.

A: The core difference between the two lies in whether the voltage can be adjusted under load. On-load tap-changers can adjust the turns ratio and output voltage without cutting off the load, which is suitable for scenarios where the grid voltage fluctuates frequently and the load requires stable voltage (such as high-voltage transmission and distribution networks). Its structure is complex, with a voltage regulation mechanism and arc-extinguishing device, and the cost is high. Off-load tap-changers can only adjust the tap position when the transformer is de-energized and unloaded, which is suitable for scenarios with stable grid voltage and little load change (such as small distribution transformers). It has a simple structure, low cost, and high reliability, but the voltage regulation is not flexible.

A: Daily maintenance of power transformers focuses on “inspection, monitoring and regular testing”: daily visual inspection includes checking the oil level (whether it is within the normal range), oil color (whether it is transparent and free of impurities), leakage, and the operation status of cooling devices (fans, oil pumps); regular monitoring of operating parameters such as load current, winding temperature and ambient temperature; periodic testing includes DGA of insulating oil, insulation resistance test, winding DC resistance test, and tap-changer contact resistance test. In addition, it is necessary to keep the transformer body and the surrounding environment clean and ensure that the ventilation and heat dissipation are unobstructed. For outdoor transformers, attention should also be paid to preventing moisture, dust, and animal damage.

A:   The core of power transformers uses laminated silicon steel sheets mainly to reduce two types of losses: eddy current loss and hysteresis loss. Silicon steel has high magnetic permeability and low hysteresis loss, which can improve the efficiency of electromagnetic induction. Laminating the silicon steel sheets (with insulating paint coated between the sheets) can cut off the closed loop of eddy current (induced current generated in the core under the action of an alternating magnetic field), thereby significantly reducing eddy current loss. The thickness of the laminated sheets (usually 0.27-0.35mm) is also optimized to balance magnetic permeability and loss. For high-efficiency transformers, high-performance oriented silicon steel sheets (such as Hi-B silicon steel) are often used to further reduce losses.

A:   The service life of power transformers (usually designed for 20-30 years) is mainly affected by insulation aging, which is determined by multiple factors: operating temperature (the most critical factor, every 6-8°C increase in temperature will halve the insulation life); moisture and pollution (moisture will reduce insulation resistance, and pollution will cause surface discharge); electrical stress (overvoltage, harmonic impact will damage insulation); mechanical stress (short-circuit impact, vibration during operation); and the quality of maintenance (regular oil treatment, fault handling in time can extend service life). To prolong the service life, it is necessary to control the operating temperature within the limit, maintain good insulation status, and avoid excessive electrical and mechanical impacts.

A:  The treatment of transformer oil leakage should follow the principle of “finding the source first, then handling it according to the severity”. First, locate the leakage point (common positions include oil tank welds, flange connections, bushing roots, and tap-changer interfaces) through visual inspection, oil level monitoring and other methods. For minor leakage (such as seepage), measures such as tightening bolts, replacing sealing gaskets (using high-temperature and oil-resistant rubber gaskets) or applying sealants can be taken; for major leakage (such as oil dripping or spraying), the transformer should be de-energized and unloaded immediately, and then maintenance measures such as welding (for oil tank weld leakage) or replacing faulty components (such as damaged bushings) should be taken. During the treatment process, attention should be paid to collecting leaked oil to avoid environmental pollution, and after the treatment, the oil level and insulation performance should be tested to ensure safe operation.