Views: 0 Author: Zhejiang Shengxian Electric Power Technology Co., Ltd. Publish Time: 2026-04-15 Origin: Site
The 10kV SF6 Ring Main Unit (RMU) is a key piece of equipment for keeping distribution lines running steadily. This guide will walk you through the most common types of failures, what causes them, and practical maintenance and installation tips — all in plain English. Our goal is to help you reduce equipment failure rates and improve power supply reliability.
Keywords: SF6 Ring Main Unit, operation & maintenance, insulation failure, fault prevention
With the rapid growth of power distribution networks, SF6 ring main units have become increasingly popular. They are compact, flexible to install, and widely used.
However, over years of operation, problems can appear — caused by environmental conditions, installation quality, or simply aging components. Understanding the early signs of common faults and knowing what to do about them is essential for keeping the power on and avoiding costly outages.
This is one of the more frustrating problems. It usually happens on older equipment that has been running for many years.
Cause:
Mostly mechanical aging. For example:
Aging coils inside lose their force, making opening and closing difficult
Metal parts become slightly deformed and stick
Control circuit contacts rust and lose connection
Consequence:
The switch fails to open or close when needed. This creates a serious safety risk.
Internal discharge or short circuits inside the unit are often related to the environment and installation details.
Cause:
Moisture and condensation: Lack of moisture protection inside the cabinet causes humidity to build up, reducing insulation performance.
Insufficient clearance: Too little insulation gap during installation, or a lightning surge that creates a momentary high voltage.
Consequence:
Phase-to-phase short circuits and equipment damage.
Cause:
When installing a three-core cable, it has to be twisted to match the phases. This creates internal torque (twisting force). Over time, this force pulls on the bushing and causes cracks at the root of the bushing. Those cracks can then lead to high-voltage short circuits.
In addition, poor workmanship when making the cable termination is another common cause of breakdown.
Cause:
When extending or connecting busbars, if the dimensions are slightly off, installers sometimes use excessive force to make it fit. This squeezes and deforms the insulation layer of the connector. That creates a spot where the electric field concentrates, and after long-term operation, insulation breakdown becomes likely.
Cause:
Ring main units rely on SF6 gas for insulation. During cable installation, the weight and twisting force of the cable put constant stress on the cabinet bushings. If the bushing is not strong enough or was installed incorrectly, the seal loosens, and gas leaks out slowly.
Consequence:
Loss of insulation capability. The equipment may fail completely or even cause an operational accident.
Here are practical steps you can take to address the problems above:
Do not wait until something breaks. Regularly test the mechanical characteristics of circuit breakers and load switches. Check coil resistance and operating voltage. Identify and replace degrading components early.
Moisture and dust control:
Make sure cable trenches are well sealed. Install dehumidification devices inside the cabinet if needed to reduce condensation.
Maintain clearance:
During installation or retrofits, confirm that insulation distances between conductors meet standard requirements.
If space allows, choose a ring main unit with raised outlet bushings. This gives you more room to adjust three-core cables, releases cable torque, reduces stress on the bushing root, and lowers the risk of cracking.
Do not force the installation.
If dimensions do not match and installation is difficult, stop and contact technical support. Never use brute force to hammer or squeeze connectors into place — that damages the insulation.
We recommend selecting units with SF6 density relays or low-pressure interlock functions. If gas pressure drops, the system will automatically alarm or lock out operations — preventing accidents caused by gas leaks.
During cable installation, choose shorter bushings when possible to reduce leverage torque. After installation, perform a leak test.
3. Product Design That Addresses Industry Pain Points
After understanding the common faults above, you can see that equipment design details have a direct impact on long-term reliability.
At Zhejiang Shengxian Electric Technology Co., Ltd. , our 10kV SF6 ring main units are designed with real operating conditions in mind. Here are the key features:
Design Aspect | Our Approach |
|---|---|
Mechanical reliability | Circuit breakers and operating mechanisms are selected and tested for long-term stability. Factory mechanical characteristic tests ensure reliable opening and closing. |
Insulation & protection | The cabinet uses aluzinc steel construction with condensation prevention in mind. Internal live parts follow insulation coordination principles. Clearance and creepage distances meet industry standards. |
Cable connection structure | Raised cable outlet bushings provide more adjustment space for three-core cable installation. This helps reduce stress on the bushing root from cable torque. |
Busbar connection | Extension connectors use silicone rubber material with fully insulated and shielded properties. Factory dimensional inspection reduces the chance of forced assembly on site. |
Gas sealing | The gas tank welding process and seal selection follow industry standards. SF6 gas density monitoring or low-pressure interlock devices are available as options for real-time pressure status. |
The reliability of a ring main unit depends not only on factory quality but also on proper installation and regular maintenance.
Pay attention to the key details we have covered here. Choose equipment that has been designed with real-world conditions in mind. That combination will help extend equipment life and keep your distribution network running safely.
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