NOJA Power

Technical Article

Published 03/2023

Three Project Examples for the GMK-1000

NOJA Power GMK-1000

Also known as the Compact GMK, the GMK-1000 is a ground mounted Recloser system with a 1.21m2 footprint. This compact arrangement allows the GMK-1000 to address a multitude of niche applications, from rail power supply to portable, trailer mounted generation connections.

GMK-1000 vs other NOJA Power GMKs

The GMK-1000 achieves a smaller footprint than its larger product line compatriots by removing the auxiliary supply transformer. This means the GMK-1000 needs its own low voltage supply to power the control system, but in substation environments and portable switchgear assemblies these are commonly available.

This design removes the internal bus-work and standalone transformers, allowing engineers to terminate directly onto the bushings of the GMK-1000 interrupter module.

GMK-1000 for Outdoor Substation Applications

A NOJA Power GMK-1000 in an outdoor substation
A NOJA Power GMK-1000 in an outdoor substation

Among the highest costs of substations is the land upon which they are constructed. In this application, NOJA Power’s compact GMK-1000 provides all protection and switching required on this underground distribution substation.

Unlike standard RMU’s, the GMK-1000 includes all protection and control relays in the base product, which are integrated and tested at the factory. This saves commissioning and engineering costs for the site, optimizing the reliability return for capital investment.

The GMK-1000 is equally at home in industrial connection settings, where factories and large facilities connect to the distribution grid at medium voltage. Beyond the standard protection and control capabilities, the integrated power quality monitoring features of the GMK-1000 can alert these operators to issues with power factor or harmonics. This allows engineers to conduct rectification works prior to costly equipment failure.

A NOJA Power GMK-1000 under installation in an industrial area
A NOJA Power GMK-1000 under installation in an industrial area

GMK-1000 for Railway connection

GMK-1000 for Railway connection

Space alongside rail corridors is often at a premium, and in this application, the NOJA Power GMK-1000 was used to connect the medium voltage supply to the rail electrification substation.

The GMK’s are mounted on a steel gantry above ground, providing clear access for operators to the equipment for testing and maintenance.

GMK-1000 for Indoor Substations

A NOJA Power GMK-1000 installed in an indoor substation
A NOJA Power GMK-1000 installed in an indoor substation

The compact footprint of the NOJA Power GMK-1000 can also permit indoor installations in confined spaces. The GMK-1000 uses solid dielectric insulation, rather than commonly used SF6 gas. Leaking SF6 in an indoor environment could cause a hazard for operators, but the GMK-1000’s gas-free design provides a mitigation for this issue.


“Our GMK1000 finds application in Mining, Industrial, Commercial, Railway and Emergency supply applications as a compact 15 or 27kV packaged circuit breaker solution,” says NOJA Power Group Managing Director Neil O’Sullivan.

The GMK-1000 provides a compact switchgear option for applications where a low voltage control supply is available. The full gamut of protection and control features of NOJA Power’s OSM with RC-10 system is included, providing significant cost savings over discrete systems. For more information, visit or contact your local NOJA Power Distributor.

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