Brief
Mutual Energy Limited (MEL) operates the 500MW Moyle Interconnector, a High Voltage Direct Current (HVDC) link commissioned in 2001 that connects Northern Ireland and Scotland. This interconnector is critical infrastructure for Northern Ireland's electricity grid.
The Moyle Interconnector contains seventeen 275 kV circuit breakers across two converter stations. The original Siemens 3AQ2-EE circuit breakers, installed in 2001, are now approaching the end of their serviceable life and require replacement.
This procurement seeks suppliers to replace circuit breakers and potentially upgrade system performance. The initial scope includes four converter pole circuit breakers (two at each station), with possible future replacement of up to thirteen additional filter, transmission line and busbar coupler circuit breakers.
Key requirements include: design, engineering, manufacture, supply, installation, testing and commissioning; demonstration of compliance with electrical ratings and project-specific Transient Recovery Voltage (TRV) duties; controlled-switching and Point-on-Wave capability; factory inspection and testing; delivery and logistics; assessment of compatibility with existing infrastructure; civil, structural, electrical, protection and control modifications; and provision of training, spares, specialist tools and technical support.
The replacement addresses the age and condition of existing equipment while providing an opportunity to improve controlled energisation performance for converter transformers. Studies have identified enhanced TRV requirements due to low short-circuit ratio on the Scottish grid side, which the replacement solution must accommodate.
The initial four circuit breakers are scheduled for replacement during planned summer outages in 2028 and 2029. Final scope, technical solution and procurement structure will be informed by market engagement and subject to relevant approvals.
