RMU (Ring Main Unit)
About us
We’re ALSTON , a broad energy trading company with a proud history.
Alston RM units are designed to supply reliable energy and protect electrical equipment in secondary distribution networks up to 36 kV.RMA units are the best solution for indoor/outdoor distribution substations
Potential applications for the system include secondary energy distribution, and the product is distinguished by its modern maintenance concept combined with extremely compact dimensions.
Ring Main Unit , type SFA-RM , 12 kV
Technical Specifications:
- Gas insulated Ring Main Units
- Rated voltage = 12 KV
- Normal current = 630 A
- Short circuit withstand current: up to 21 kA.
- Short circuit duration: 3 sec
- Power frequency Withstand voltage = 38 kV r.m.s
- Lightning Impulse withstand voltage Up = 95 kV peak
- Internal arc classification: A (FLR)
- Degree of protection: IP41 for indoor / IP54 for outdoor


Ring Main Unit , type SFA-RM , 17.5 kV
Technical Specifications:
- Gas insulated Ring Main Units
- Rated voltage = 17.5 KV
- Normal current = 630 A
- Short circuit withstand current: up to 21 kA
- Short circuit duration: 3 sec
- Power frequency Withstand voltage = 38 kV r.m.s
- Lightning Impulse withstand voltage Up = 95 kV peak
- Internal arc classification: A (FLR)
- Degree of protection: IP41 for indoor / IP54 for outdoor
Ring Main Unit , type SFA-RM , 36 kV
Technical Specifications:
- Gas insulated Ring Main Units
- Rated voltage = 36 KV
- Normal current = 630 A
- Short circuit withstand current: up to 25 kA.
- Short circuit duration: 1 sec.
- Power frequency Withstand voltage (common value) = 70 kV r.m.s
- Power frequency Withstand voltage (across the isolating distance) = 80 kV r.m.s
- Lightning Impulse withstand voltage (common value) = 170 kV peak
- Lightning Impulse withstand voltage (across the isolating distance) = 200 kV peak
- Internal arc classification: A (FLR)
- Degree of protection: IP54 (indoor & outdoor applications)


SFA-RM Smart Ring Main Units
Technical Specifications:
- Gas insulated Self-power RMU
- Rated voltage = up to 36 KV
- Normal current = 630 A
- Short circuit withstand current: up to 25 kA.
- Short circuit duration: 1 or 3 sec
- Loss of service continuity category (LSC) LSC2A-PM
- Internal arc classification: A (FLR)
- Degree of protection: IP41 for indoor / IP54 for outdoor
- Relative Humidity : 100%
- 3G/4G Communication, VPN Security “IPsec”
- Accurate Measurements for voltage and current in all switching elements