Transformer insulating oil is a critical medium responsible for internal insulation isolation and heat dissipation cooling. It must strictly comply with national standard requirements for insulation strength and thermal conductivity. During on-site installation, commissioning and daily maintenance of oil-immersed transformers, pressure filtration technology is widely adopted to remove moisture, particulate impurities and residual pollutants from insulating oil, achieving oil purification and drying treatment to ensure stable insulation performance of the transformer.
1. Standard Pressure Filtration Operation Process
The pressure filtration method is the conventional and core process for on-site purification of transformer insulating oil, mainly used for overall dehumidification, drying and impurity removal of new oil or operating oil. The standardized operation steps and parameter specifications are as follows:
1.1 Operation Sequence of Valves and Equipment
Start the filtration procedure by opening Valve 8 and Valve 11, then activate the oil pump. After stable equipment operation, open Valve 6 and Valve 7 to formally start pressure oil filtration. For shutdown operation, follow the reverse sequence: firstly close Valve 6 and Valve 7, stop the oil pump after the pipeline pressure stabilizes, and finally close Valve 8 and Valve 11 to complete the whole filtration process.
1.2 Operating Pressure Monitoring and Filter Replacement Standard
During normal filtration operation, the system working pressure should be stably maintained within the standard range of 3×10 Pa to 4×10 Pa. When the filter paper or filter screen is blocked by long-term intercepted impurities and oil sludge, the pipeline operating pressure will gradually rise. Once the system pressure reaches 6×10 Pa, the equipment must be stopped immediately for filter paper replacement and pipeline cleaning to avoid reduced filtration efficiency and abnormal equipment load caused by blockage.
1.3 Preprocessing Standard for Filter Paper
To ensure filtration accuracy and avoid secondary moisture pollution, the filter paper must be pre-dried before use. Place the filter paper in a constant-temperature oven at 80℃–90℃ for continuous drying for 24 hours, and store the dried filter paper in a sealed and clean container for standby use, preventing moisture absorption from the air.
1.4 Regular Maintenance and Circulating Filtration Standards
The internal filter screen of the oil filter shall be disassembled and cleaned regularly every 10 to 15 hours of operation to ensure unobstructed oil circulation. At the initial stage of oil filtration (within the first 3–5 minutes), the filtered oil shall be returned to the dirty oil tank through Valve 10 for secondary circulating filtration to eliminate residual fine impurities. The residual oil accumulated inside the filter equipment shall be returned to the dirty oil system through Valve 9 for repeated purification. The whole process adopts multiple circulating refining and drying modes until the insulating oil quality fully meets the acceptance standards.
2. Transformer Live Oil Filtration Specification (On-Line Oil Purification)
Live oil filtration refers to the on-line purification operation performed while the transformer is in operation, which can realize oil purification without power outage. Affected by operating voltage and electric field environment, strict technical specifications and safety protection standards must be followed during construction.
2.1 Voltage Restriction and Defect Prevention Mechanism
Live oil filtration is prohibited when the operating voltage exceeds 10V. During the filtration process, the flowing oil will generate tiny bubbles. Under high-voltage electric field conditions, free bubbles are prone to ionization and discharge, which will reduce the insulation strength of insulating oil and induce internal partial discharge faults. During the entire live filtration process, it is necessary to regularly exhaust the gas accumulated in the transformer gas relay to eliminate hidden dangers of gas discharge.
2.2 Safety Protection and Construction Requirements
All oil filter equipment and connecting oil pipelines must be reliably and effectively grounded to prevent static electricity accumulation and electric shock risks. The construction personnel must be professionally trained, equipped with complete insulating protective equipment, and the whole operation process must be supervised by special personnel to ensure standardized and safe construction.
2.3 Live Filtration Pipeline Connection and Circulation Process
Connect the pressure oil filter equipment to the diagonal interfaces of Valve 4 and Valve 5. The system extracts oil through Valve 4 and returns the purified oil to the transformer oil tank through Valve 5 to form a closed circulating purification loop. After repeated circulating filtration, the moisture content, cleanliness and insulation parameters of the insulating oil will gradually reach the standard operating requirements, realizing on-line maintenance and performance upgrading of transformer oil.
About us
Since its founding in 2018, Zhejiang Lvma Electric Co., Ltd. has built upon 17 years of deep industry roots. As an ISO 9001:2015-certified company, we manufacture intelligent switchgear systems and premium oil-immersed and dry-type distribution transformers, serving clients across Europe, the Middle East, South America, Southeast Asia, and Africa.
With more than 40 patents, our R&D capabilities drive the transition from conventional manufacturing to intelligent, green energy systems. Digital operations and continuous condition monitoring ensure our products meet the highest benchmarks for safety and dependability.