For buyers of 22kV SF6 GIS RMU Ring Main Unit Switchgear, the key considerations are not only switching performance, but also how quickly faults can be located, how safely operators can access the equipment, and how much maintenance is required throughout its service life. Usune addresses these requirements through high-voltage live indication, fault indicators, microcomputer protection and a pressure-sealed gas system.
The RMU can be equipped with fault indicators for phase-to-phase and phase-to-ground faults. Once a fault occurs, the indicator provides an alarm to help operating personnel identify the affected section and locate the fault point more efficiently.
For distribution networks connected to a monitoring center, fault information can also be transmitted to the monitoring server, allowing the control room to identify the fault area and specific position without relying entirely on manual inspection.
The high-voltage live indication device provides a visual reminder for checking whether the primary circuit is energized. It also supports phase verification to help operators confirm the electrical status before operation.
An electrical interlocking connection and associated magnetic lock can prevent the cable compartment door from being opened while the incoming cable remains energized, providing an additional layer of protection during maintenance.
The optional microcomputer protection, measurement and control device replaces traditional electromagnetic relay protection with digital monitoring technology. It can be used for lines, distribution transformers and other primary equipment.
The system can integrate current and voltage protection, measurement, alarm and control functions, supporting intelligent power management and communication with the customer's monitoring network.
| No. | Items | Unit | Load break switch unit | combination unit | Circuit breaker unit |
| 1 | Rated voltage | kV | 12/24 | 12/24 | 12/24 |
| 2 | Rated frequency | Hz | 50 | 50 | 50 |
| 3 | Rated current | A | 630 | 125 (depends on fuse current) | 630 |
| 4 | Rated insulation level‑1min Frequency withstand voltage‑Inter phase, ground | kV | 42/65 | 42/65 | 42/65 |
| Rated insulation level‑1min Frequency withstand voltage‑isolating distance | kV | 48/79 | 48/79 | 48/79 | |
| Rated insulation level‑1min Frequency withstand voltage‑Controlling and auxiliary circuit | kV | 2/2 | 2/2 | 2/2 | |
| Rated insulation level‑Lighting impulse withstand voltage‑Inter phase, ground | kV | 75/125 | 75/125 | 75/125 | |
| Rated insulation level‑Lighting impulse withstand voltage‑isolating distance | kV | 85/145 | 85/145 | 85/145 | |
| 5 | Rated short circuit withstand current | kA/s | 25/4 | —— | 25/4 |
| 6 | Rated peak withstand current | kA | 63 | —— | 63 |
| 7 | Rated short circuit making current | kA | 63 | Limited by HV fuse | 63 |
| 8 | Rated short circuit breaking current | kA | —— | Limited by HV fuse | 25/25 |
| 9 | Rated transmission current | A | —— | 1700/1400 | —— |
| 10 | Rated active load breaking current | A | 630 | —— | —— |
| 11 | Rated closed‑loop breaking current | A | 630 | —— | 630 |
| 12 | Mechanical life‑load break switch/CB | Times | 10000 | 10000 | 20000 |
| Mechanical life‑Isolation/ground switch | Times | 5000 | 5000 | 5000 | |
| 13 | Circuit resistance | μΩ | ≤150 | —— | ≤150 |
| 14 | Rated charging pressure（20℃ gauge pressure） | MPa | 0.04 | 0.04 | 0.04 |
| 15 | Gas annual relative leakage rate | % | 0.05 | 0.05 | 0.05 |
| 16 | IP protection degree‑Cabinet | IP4X | IP4X | IP4X | |
| IP protection degree‑Gas tank | IP67 | IP67 | IP67 |
When a short circuit occurs between phases or between a phase and ground, the fault indicator provides an alarm indication. Maintenance personnel can use the signal to identify the affected feeder and narrow down the fault location.
For projects requiring centralized monitoring, fault information can be transmitted to the monitoring center. The monitoring computer can display the corresponding fault section and location, helping maintenance teams reduce fault-search time and restore power more efficiently.
The primary components of the SF6 cabinet are designed as a sealed system and generally do not require routine maintenance during the specified service life under normal operating conditions.
The gas tank is manufactured from stainless steel, providing long-term corrosion resistance. The mechanical operating components are positioned outside the gas tank, making inspection, operation and component replacement more convenient when service is required.
For installations exposed to extreme dust, sand or pollution, periodic inspection of mechanical rotating parts and lubrication conditions is recommended.
The USRM6 series uses a pressure-sealed gas system and does not require special gas inspection under normal operating conditions.
Before operation, the pressure gauge should be checked. Under normal conditions, the pressure indicator should remain within the green operating area. The reference pressure is 0.14 MPa, with the gas pressure maintained above 0.135 MPa at 20°C under the specified sealing conditions.
The expected annual gas leakage rate is less than 0.1%, supporting long-term gas sealing performance.
The 22kv Sf6 Gis Rmu Ring Main Unit Switchgear is developed with reference to IEC 298 requirements, with a designed service life of more than 30 years under normal operating conditions.
The airtight switch design helps maintain gas sealing throughout the expected service period, reducing the need for frequent gas-related maintenance and helping customers control long-term operating costs.
| Key Consideration | Usune 22kV SF6 GIS RMU | Conventional RMU |
| Insulation | SF6 gas insulated | Depends on equipment design |
| Fault Detection | Optional local and remote fault indication | Often relies more on manual inspection |
| Monitoring | Digital protection and communication available | May require separate monitoring equipment |
| Safety | Live indication and electrical/magnetic interlocking | Depends on configuration |
| Maintenance | Sealed primary system with low maintenance requirements | Maintenance requirements vary |
| Gas Tank | Stainless steel sealed tank | Depends on construction |
| Service Life | Designed for more than 30 years under normal conditions | Depends on product design and maintenance |
Usune 22kv Sf6 Gis Rmu Ring Main Unit Switchgear is suitable for industrial distribution networks where multiple feeders need reliable switching and fast fault location. Fault indicators and digital protection devices can help maintenance teams identify abnormal sections more efficiently.
The RMU can be configured with microcomputer protection and measurement functions for distribution transformers, providing current and voltage monitoring, alarm and protection functions within the medium-voltage network.
For customers developing intelligent power distribution systems, the RMU can connect protection, measurement, fault indication and communication functions to a central monitoring system, supporting remote fault identification and more efficient network management.
A customer used the Usune 22kv Sf6 Gis Rmu Ring Main Unit Switchgear for an industrial ring network with multiple incoming and outgoing feeders. During commissioning, the customer focused on whether operators could quickly identify the affected feeder when a phase-to-phase or phase-to-ground fault occurred. The integrated fault indicator provided local alarm information, helping maintenance personnel narrow down the fault section before carrying out on-site inspection.
For a transformer distribution application, the customer selected the RMU with a microcomputer protection and control device. The system provided digital current and voltage monitoring together with protection and alarm functions. The customer found this configuration more convenient for monitoring transformer operating conditions than relying only on conventional relay protection.
A customer requiring centralized distribution monitoring connected the RMU's fault indication and digital protection functions to the monitoring center. When a fault signal was generated, the monitoring screen could identify the corresponding fault section, allowing the operating team to determine where field inspection was required and improve troubleshooting efficiency.
For customers operating the RMU under normal service conditions, the sealed SF6 gas tank reduces the need for routine internal maintenance. Customers also value the external mechanical operating components because they can be inspected or replaced more conveniently when maintenance is required.
Zhejiang Usune Electric Co.,Ltd. has established management systems according to ISO 9001 Quality Management System, ISO 14001 Environmental Management System and ISO 45001 Occupational Health and Safety Management System.
To meet different international market requirements, Usune medium-voltage switchgear products have undergone relevant IEC and GB standard type tests, with applicable products obtaining CE certification. These systems support consistent manufacturing quality, product testing and technical compliance for medium-voltage power distribution projects.
Yes. The RMU can be equipped with fault indicators capable of detecting phase-to-phase and phase-to-ground faults and providing local alarm indications.
Yes. When equipped with the corresponding communication and monitoring system, fault information can be transmitted to a monitoring center, where the affected section and fault position can be displayed.
Under normal operating conditions, the pressure-sealed system does not require special routine gas inspection. The pressure gauge should be checked before operation and should remain within the green area under normal conditions.
The USRM6 series is designed for a service life of more than 30 years under normal operating conditions, with an expected annual gas leakage rate of less than 0.1%.
Usune combines SF6 sealed insulation, fault indication, live-part indication, safety interlocking, digital protection and low-maintenance operation in one medium-voltage RMU solution, making it suitable for modern ring network and intelligent distribution applications.
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No. 298, Wei 17th Road, Yueqing Economic Development Zone, Yueqing, Wenzhou City, Zhejiang Province, China
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