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.