Ring Main Unit

Future-proof due to SF6-free

Designed on the basis of specific customer enquiries for a complete replacement for gas-insulated switchgear systems, the new NATUS Type NES-F-RK ring cable switchgear system has been developed using airtight technology for operating voltages of up to 12 kV.

Potential applications for the system include secondary energy distribution, and the product is distinguished by its modern maintenance concept combined with extremely compact dimensions.

Outlets for cables, transformers and motors can be provided using a fully-featured, extendable circuit breaker switch, including transducer and protection device. A generously-dimensioned secondary control chamber offers features for the most sophisticated demands regarding customer-specific instrumentation & control engineering requirements.

NATUS benefits

  • In-house development and manufacture
  • Type-tested and arc-tested in accordance with IEC 62271-200 (EN 62271-200 / VDE 0671-200)
  • 12kV / 630A / 25kA;1s
  • Availability classification: LSC1
  • Arc resistance classification: IAC AFLR
  • Pressure release through individual absorber
  • Highly compact dimensions despite airtight design
    • Width: 1,200 mm
    • Field depth, not including doors: 800 mm
    • Field height with absorber: 2,000 mm
    • Field height with base frame & absorber: 2,400 mm
  • Installation of protective transformers with protective device possible
  • Very large low-voltage space for installation of secondary devices (I&C and safety) with customer-specific design
  • Cable connections possible by means of
    • plug-in system (e.g. Pfisterer Connex size 1)
    • Standard sealing end
  • Integrated cable testing system available, cable testing possible without removing the medium-voltage cable or opening the control panel
  • Typical applications for output (modular circuit breaker design)
    • Motor
    • Transformer
    • Cable

Design features and classification under standard IEC 62271-200

Busbar system  Single
Operational availability category LSC 1
Internal arc resistance classification IAC AFLR


12 kV


Rated Values



Rated voltage



Rated power-frequency withstand voltage

28 kV / 1 min


Rated lightning impulse withstand voltage



Rated short-time withstand current

25 kA / 1 s


Rated impulse current



Rated short circuit period



Protection class



Internal arc resistance classification

AFLR 25 kA / 1 s