My humble opinion on daily maintenance of transformers-News-Henan Weichi Electrical Equipment Co., Ltd.

My humble opinion on daily maintenance of transformers

Time：2025-06-19　Click：553

Abstract: Transformers are one of the common electrical equipment in the distribution network and are also the ones that come into frequent contact in grassroots management. As a grassroots manager, whether the transformers operate normally not only affects the safety of the power grid but also impacts the image of the power enterprise in the eyes of users. The Xiugu Power Supply Station where I work is responsible for supplying power to more than 22,000 households within the county. However, since its restructuring more than 10 years ago, there has not been a single transformer burnout accident, which not only saves money for the power supply enterprise but also provides a satisfactory answer to ensuring continuous power supply for users. Next, I will talk about my experience in transformer maintenance.

1. Strengthen daily patrols, maintenance, and regular testing

According to the division of responsibilities among the management personnel in the substation area, in addition to regularly conducting transformer patrols, I also require the management personnel to strengthen daily patrols and assign specific responsibilities to specific personnel. The key inspection contents include:

(1) Inspect the appearance. The main inspection is whether there is oil leakage, smoking of parts, or discharge phenomena on the exterior of the transformer. The transformer may leak oil due to poor welding of the transformer casing or inadequate rubber gasket. If the oil level is too low, insulation protection will be lost, leading to discharge between conductive parts or between conductive parts and the casing. In severe cases, the transformer may be burned. Therefore, faults should be eliminated and oil replenished in a timely manner to ensure that the oil level remains at 1/4 to 3/4 of the oil level indicator. For loose parts, poor contact, or even discharge phenomena, the transformer drop-out fuse should be disconnected in a timely manner to eliminate hidden dangers.

(2) Listen to the sound. A transformer operating normally will emit a uniform and subtle buzzing sound. When the transformer experiences faults of different nature, the sound will change. At this time, measures should be taken according to the on-site situation to identify the cause of the fault.

(3) Inspect the oil stains on the distribution transformer and the dust on the high and low voltage bushings, promptly clean and wipe away the oil stains and dust to prevent pollution flashover discharge during humid or rainy weather, which could cause inter-bushing short circuits, high voltage fuses to melt, and the distribution transformer to fail to operate normally. I require the inspection personnel to clean at least once every two months.

(4) Observe the oil color and regularly check the oil temperature. Especially under conditions of significant load variations, large temperature differences, and adverse weather, increase the frequency of inspections. The top oil temperature during the operation of oil-immersed distribution transformers should not exceed 95℃. To prevent accelerated deterioration of the windings and oil, the temperature rise of the top oil should not frequently exceed 45℃.

(5) Conduct a megger test on the insulation resistance of the distribution transformer, check whether the leads are secure, and pay special attention to whether the contact at the low-voltage outlet connection is good and whether the temperature is abnormal.

(6) Strengthen the measurement of electricity load. During peak usage periods, intensify the load measurement of each distribution transformer, and increase the frequency of measurements when necessary. Timely adjust distribution transformers with unbalanced three-phase current to prevent the neutral line current from being too large and burning out the leads, causing damage to user equipment and the distribution transformer itself. For distribution transformers with a connection group of Yyn0, the three-phase load should be balanced as much as possible. Power supply should not be provided solely through one or two phases, and the neutral line current should not exceed 25% of the rated current on the low-voltage side. Efforts should be made to ensure that the distribution transformer operates without overload or unbalanced load.

(7) Regularly inspect and replace primary and secondary fuses. It is strictly prohibited to use aluminum wires as substitutes for fuses. As we all know, primary fuses protect the system, while secondary fuses protect the transformer. The selection of fuses must be compatible with the transformer capacity.

2. Prevent external force damage:

(1) Reasonably select the installation location of the distribution transformer, which should be as close to the load center as possible, with the power supply radius controlled within 0.5km. At the same time, try to avoid installing it in areas prone to lightning strikes or low-lying waterlogged areas. Due to its location in the county town, there are many transformers along the road intersections. In order to reduce accidents caused by cars hitting poles and towers, anti-collision strip signs are pasted on all poles and towers along the roadside.

(2) Try to avoid installing low-voltage metering boxes on distribution transformers as much as possible. Due to long-term operation, the glass of the metering box may be damaged or the low-voltage terminal of the distribution transformer may be damaged and cannot be replaced in a timely manner, resulting in damage to the distribution transformer caused by rainwater or other factors. Over 95% of our public distribution transformers are equipped with JP cabinets, which provide excellent protection for the safe operation of the transformers.

(3) Unauthorized adjustment of the tap switch is prohibited to prevent phase-to-phase short circuits caused by improper adjustment of the tap switch, which could potentially burn out the distribution transformer.

(4) Install insulating covers at the high and low voltage ends of distribution transformers to prevent damage from natural disasters and external objects. In residential areas with narrow roads and forest areas frequented by animals, install high and low voltage insulating covers to prevent objects falling from the wiring terminals of distribution transformers, which could cause a low voltage short circuit and burn out the transformer.

(5) Regularly inspect the power lines and clear the pathways along the lines to prevent accidents where tree branches touch the conductors, causing low-voltage short circuits and damaging distribution transformers.

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Ways to enhance the short-circuit resistance of transformers in power systems

1. Fault analysis of transformers in power systemsA transformer is a device that utilizes the principle of electromagnetic induction to change current. It is widely used in the electric power system. Experiments and investigations have confirmed that faults caused by short circuits in transformers have been seriously affecting the safety and stability of power transmission. Therefore, in order to reduce the probability of faults in the electric power system, it is necessary to conduct a focused analysis and research on the short-circuit capability of transformers. The following provides a specific analysis of the causes leading to short-circuit accidents in transformers:(1) Defects in the structural design of the transformerThe weakness in the short-circuit resistance of transformers is largely attributed to defects in their structural design. Currently, transformer manufacturers in China use static theory to calculate the mechanical forces on transformers. According to static theory, for copper-conductor transformers, the calculated conductor stress should be less than 1600kg/cm2. However, in actual use, the internal dynamics of transformers are complex and variable. Common theoretical values cannot intuitively reflect the actual operating conditions of transformers, making it difficult to meet the requirements for short-circuit resistance. Analyzing the currently common transformer models, low-loss transformers remain the mainstream products. However, there is no consensus among manufacturers on how to achieve low loss in transformers. Additionally, in the design of low-voltage leads for large-capacity transformers, if the fulcrum of the lead is not adequately considered, resulting in a cantilever beam formation, a phase-to-phase short-circuit fault may occur when subjected to the impact of short-circuit current.(II) Poor material qualityThe insulation pressing plate and laminated wood board of the transformer, if not meeting the standard requirements in terms of processing quality and mechanical strength, can also lead to frequent short-circuit failures. Some transformer manufacturers, in order to minimize the loss of winding eddy current, processing difficulties, and production and operation costs, often use thinner wires or ordinary and cheap transposed conductors instead of semi-rigid conductors with stronger mechanical properties during the design process. Although these ordinary and cheap materials can help enterprises reduce production and operation costs, they are unable to meet the anti-short-circuit capability of transformer windings due to the limitations of their material properties. Furthermore, due to the uneven level of domestic manufacturers and the significant gap between their production processes and some advanced foreign technologies, the density of insulation boards is insufficient, which can easily lead to natural shrinkage phenomena and trigger transformer short-circuit failures.(III) There are serious structural issuesSerious structural issues in transformers can also lead to short-circuit faults. Since transformers undergo a series of transportation, lifting, and disassembly processes from manufacturing to deployment, they are inevitably subjected to some impacts. If the internal structure of the transformer is not sturdy, impacts can cause structural issues such as winding displacement and insulation damage, which pose significant safety hazards for future operation.(IV) Issues of transformers operating in a 220kV environmentFor 220kv high-capacity transformers, the connection status of the inner coil is also an important determinant of short-circuit faults. Although the tapping of the inner coil can provide many conveniences for the operation of high-capacity transformers, if the tapping design is not reasonable enough, it can lead to local electric field disorder in the tapping leads, resulting in partial discharge of the transformer.(V) Problems in technology and equipmentIf the manufacturing process and equipment of the transformer cannot effectively ensure the tight winding, pressing, and sheathing of the coil, it will also result in a decrease in short-circuit resistance, thereby causing faults. Moreover, if the insulating pads of the transformer are not sealed or the sealing work is not done properly, the electrodynamic force generated during a short circuit may damage the wire insulation and cause it to break down.When winding the transformer coil, if the tension of the wire is insufficient or due to limitations in technology and equipment, the coil may be wound loosely, leading to a suspended state. This reduces the transformer's resistance to short circuits. If the coil ends are not bound tightly and securely, it can also easily cause short-circuit faults in the transformer. If the gap between the wound coils is too large, resulting in insufficient internal support of the coil, it can cause deformation or collapse of the winding coil, posing significant safety hazards for future operation. Additionally, if the clamping force of the transformer core is insufficient, and effective measurements and appropriate adjustments to the pressure are not made after the core is stacked, it can lead to loose clamping of the core, which is prone to displacement during transportation and collision, causing uneven internal stress in the transformer and resulting in serious consequences.II. Ways to enhance the short-circuit resistance of transformersDue to the crucial role of transformers in the power system, it is imperative to conduct in-depth research on their quality and performance. This article delves into the common causes of transformer short-circuit faults and proposes targeted technical methods to enhance the short-circuit resistance of transformers. The following provides a detailed analysis:(1) Mechanical force calculation and product structure design for improved transformersThe physical structure of a transformer determines its operational performance. Therefore, it is necessary to optimize and improve the mechanical force calculation and product structure design of the transformer, so that the mechanical force distribution of its internal wires can better meet practical requirements and enhance its short-circuit resistance. When designing the structural design of the transformer, a pressure sensor calibrator installed between the pressure plate and the clamping piece can be used to measure the impact force on the winding structure inside the transformer, providing a reliable guarantee for the structural design of the transformer.(II) Short-circuit test of transformerBy conducting short-circuit tests on transformers and analyzing relevant data parameters, a solid foundation is laid for improving the product structure of transformers and enhancing their resistance to short circuits. It is worth noting in this process that conducting short-circuit tests is not only to ensure that the manufacturer's products are qualified, but more importantly, to apply safe and reliable technology to actual production, avoiding the situation where some manufacturers only test and reinforce transformers without promoting technology in actual production.In summary, with the continuous advancement of science and technology, the continuous improvement of power system operation quality, and the widespread operation of ultra-high voltage power transmission and transformation methods, the short-circuit resistance of transformers and the huge losses caused by short circuits have become an important issue that transformer manufacturers and operation units face and urgently need to address. In order to effectively enhance the short-circuit resistance of power system transformers, in addition to requiring manufacturers to make *** improvements in mechanical force calculation and product structural design, attention should also be paid to potential quality hazards in process operations. These issues require high attention from transformer manufacturers and operation units, so as to *** enhance the safety and stability of power system operation.In summary, as the transformation of the power grid progresses, it is imperative to enhance the short-circuit resistance of transformers in the power system to meet development needs. Improving the short-circuit resistance of transformers in the power system not only effectively enhances the safety of mining area power grid operations but also reduces the time required for fault handling, maximizes loss reduction, and prevents accidents, ensuring the safe and stable operation of the power system.

2025-06-19