Introducing the Dual Recloser GMK: A New Approach to MV Isolation

As medium-voltage networks become more complex with the integration of renewables, storage, and private infrastructure, traditional approaches often require multiple pieces of switchgear, such as circuit breakers, isolators, and protection systems—resulting in higher costs and more complex installation processes.

Leveraging proven GMK architectures to address these challenges, NOJA Power engineers have evolved the design and introduced a new solution: the Dual‑Recloser GMK.

This innovative architecture integrates two OSM Automatic Circuit Reclosers connected in series, providing enhanced dielectric performance within a compact, factory-built solution.

A Dual-Recloser Approach to Isolation

At the core of the Dual Recloser GMK design is the use of two vacuum circuit breakers connected in series. This configuration leverages the well-established double-break concept, where two vacuum interrupters provide enhanced dielectric performance compared to a single interruption point.

This double-break arrangement introduces two independent interruption points along the circuit, supporting improved isolation performance in medium-voltage applications.

Integrated Protection and Control

In addition to the physical configuration, each recloser is equipped with its own protection and control system:

• Dedicated current transformers (CTs) and Capacitive Voltage Transformer (CVTs) devices
• Independent RC-10 control relays
• Full protection functionality, including overcurrent, directional, and voltage-based protection

This architecture enables dual, fully independent protection systems operating within a single integrated enclosure. This also introduces an additional layer of protection redundancy for critical applications.

Verification Functions

The Dual Recloser GMK uses additional verification tools to confirm de-energisation:

• Integrated Voltage Detection System (VDS) on both line and load sides
• Measurement capabilities within the RC controllers

These features allow operators to confirm de-energisation prior to earthing operations, supporting safe and reliable maintenance procedures.

Simplifying Design for Medium Voltage System

The Dual Recloser GMK is designed to reduce the complexity typically associated with medium-voltage connections. By integrating switching, protection, and verification functions within a single enclosure, the solution can help minimise the need for additional switchgear such as separate circuit breakers or isolators.

Key benefits include:

• Reduced system footprint
• Relay protection redundancy
• Simplified design and engineering requirements
• Factory-assembled and tested solution
• Streamlined installation and commissioning

The Dual‑Recloser GMK is just one example of how the GMK platform continues to evolve to meet the demands of modern power networks.

Designed for applications where integration, reliability, and compact footprint are critical, the GMK is widely used across renewable connections, industrial supply, mining operations, transport electrification, and private networks.

As medium-voltage systems become more complex, the need for simpler and more integrated solutions continues to grow. The NOJA Power GMK range delivers this by combining protection, switching, and isolation within a single, factory-built platform—supporting safer, more efficient network design.