Sealed Stainless Steel Gas Tank for 20-24kV Distribution
The 20-24kV distribution level occupies a specific niche in the medium voltage landscape. It sits above the widely-deployed 10-12kV city distribution level and below the 35-40.5kV sub-transmission tier. That makes it the practical choice for three growing use cases: interconnection points for distributed generation plants (wind, PV, storage), city distribution networks migrating from 10kV to 20kV to improve loss and capacity, and rail electrification auxiliary distribution feeding the 25kV traction system. On this platform, all primary live parts are sealed inside a 3mm 304 stainless steel gas tank, so the RMU can be installed and forgotten — the tank interior is not accessible in service and does not need to be.
Compact RMU Footprint for Distribution Substations
The physical footprint is engineered for space-constrained installations typical at the 20-24kV level: distribution kiosks alongside DG plants, container substations at DG interconnection points, prefabricated substations sited at the edge of industrial parks, and building electrical rooms in mixed-use developments. The compact tank layout leaves room for cable termination access and door swing in installations that would not accommodate an air-insulated cabinet of equivalent rating. Modular C / F / V unit combinations mean the exact feeder mix required by the single-line diagram is delivered without oversized cabinet volume.
3mm 304 Stainless Steel Tank, Laser-Welded on TRUMPF Systems
The gas tank is built from 3mm 304 stainless steel plate and welded on 3D five-axis laser welding systems imported from TRUMPF (Germany). Laser welding produces a narrow uniform seam with much lower heat-affected zone distortion than conventional MIG or TIG welding, which translates directly into better long-term gas tightness. The finished tank has a smoother external appearance without post-grinding — a real detail on rooftop or public-facing installations where the switching station is visible.
Verified ≤0.01% Annual Gas Leakage — 30-Year Service Life
Every finished tank is leak-tested on a SEILER (Germany) automatic helium leak detection line. Helium mass spectrometry can detect leak paths several orders of magnitude smaller than pressure-decay methods, so the ≤0.01% per year annual leakage rating is a verified factory number, not an extrapolation. The tank normal service life is more than 30 years, meaning an RMU installed today at a wind or PV interconnection point should carry through the full generation asset's design life without gas top-up.
Fully-Insulated Solid Extension Busbar
Extension busbars use fully-insulated screened solid busbar construction. Every conductive surface is covered by a bonded insulation layer with an outer earthed screen, so the busbar surface can be safely handled during connection work and there is no exposed live metal even when a tank is open. This matters on distributed generation projects where the RMU sits inside a container substation and the operator is close to the equipment during commissioning and future extension work.
24kV, 1400A Load-Break Switch – Fuse Combination Transfer Current
The load-break switch – fuse combination unit at 24kV is rated at a transfer current of 1400A. Transfer current is the current level up to which the load-break switch can safely commutate the feeder onto the fuse element without arc restrike, so a high transfer current widens the range of feeder loads that can be protected through the fuse combination. At 24kV, a 1400A rating covers all practical distribution transformer ratings on a 20-24kV feeder — including the larger transformer sizes seen at industrial and DG interconnection substations.
AFLR 20kA / 0.5s Internal Arc with IP54 / IK10 Switching Station Protection
Internal arc classification is AFLR 20kA / 0.5s — accessibility on Front (A), Lateral (L) and Rear (R) verified for a 20kA arc fault sustained for 0.5 seconds. At the switching-station level (the complete installation including cabinet and mounting enclosure), protection reaches IP54 against dust and water ingress, with IK10 mechanical impact protection. This is the combination expected of a container substation at a DG interconnection point or a compact rooftop switching station exposed to weather and impact.
Applications: Distributed Generation, Urban Network Upgrade, Rail Auxiliary
Three application segments drive most demand for a 24kV RMU today. First, distributed generation interconnection: wind farms, PV plants and battery storage sites terminate the medium voltage collector system into an RMU at the plant boundary, and 24kV is a common collection-network voltage. Second, city distribution networks migrating from 10-12kV to 20kV, where existing feeders are re-insulated for higher voltage to raise capacity without laying new cable — the RMU is the switching device at each substation on the upgraded network. Third, rail electrification auxiliary distribution feeding station lighting, signalling, HVAC and depot loads from the 25kV traction supply through a step-down to 20-24kV. The compact sealed RMU suits all three because the installation environment is invariably confined and long-term maintenance access is limited.
