In modern power systems, the reliable operation of oil-immersed transformers, reactors, and other high-voltage electrical equipment is directly linked to the safety and stability of the grid. Vacuum Oil Injection (VOI), as a critical process in both the manufacturing and maintenance of such equipment, is gaining increasing industry recognition. This article provides an in-depth analysis of the principles, advantages, application scenarios of vacuum oil injection, and—most importantly—its vital role in enhancing insulation performance.
What Is Vacuum Oil Injection?
Vacuum Oil Injection is a specialized process that involves filling electrical equipment with purified insulating oil under a high-vacuum environment. Typically performed after the equipment has undergone thorough drying, this technique aims to completely remove residual air and moisture from within the device. By doing so, it ensures that the insulating oil fully penetrates and saturates windings, cores, and all insulating structures—maximizing dielectric strength and thermal dissipation capabilities.
Core Advantages of Vacuum Oil Injection
Efficient Deaeration and Dehydration:
Under vacuum conditions, trapped gases and trace moisture inside the equipment are effectively evacuated, preventing bubble formation or moisture-induced partial discharges and potential dielectric breakdown.
Enhanced Insulation Performance:
Injecting oil in an oxygen-free, moisture-free environment allows it to uniformly fill every void, significantly improving overall insulation strength and extending equipment service life.
Prevention of Oxidation and Contamination:
The fully enclosed vacuum system prevents contact between the insulating oil and ambient air, minimizing oxidation and maintaining oil purity—thereby reducing long-term maintenance costs.
Compliance with International Standards:
Standards such as IEC 60076 and GB/T 1094 explicitly recommend or require vacuum oil injection for large oil-filled equipment to guarantee factory-level quality and reliability.
Application Scenarios for Vacuum Oil Injection Equipment
Final oil-filling stage for new oil-immersed power transformers before delivery
Re-filling during major overhauls and re-commissioning of substation main transformers
On-site maintenance of oil-filled equipment such as high-voltage reactors and instrument transformers
Critical applications in offshore wind farms, rail transit systems, and other sectors demanding ultra-high reliability
Our Vacuum Oil Injection Solution
As a high-tech enterprise specializing in power equipment manufacturing and intelligent operation & maintenance services, we deploy fully automated Vacuum Oil Injection systems.
Our integrated solution features:
High-precision vacuum units
Multi-stage oil filtration systems
Real-time monitoring modules
Key performance indicators include:
Vacuum level ≤ 100 Pa
Intelligent oil temperature control (40–70°C)
Moisture content in oil ≤ 10 ppm
Full-process data logging and traceability
Our engineering team strictly adheres to IEC and national standards, offering end-to-end services—from customized solution design and on-site execution to final acceptance testing—to ensure every piece of equipment achieves optimal insulation integrity.