Shore Connection Box
A shore connection box isolates the ship's electrical network from its own generators and ties it instead to a shore supply, so engines can be shut down completely while alongside instead of idling to hold hotel load.
Read more — Shore Connection Box explained ▾
What makes this type
The shore connection box is the interface point where a vessel's electrical distribution system can be switched from its own generators to a shore-side power supply, commonly called cold ironing. Unlike a simple socket, it contains the switching, protection and interlocking needed to guarantee that ship and shore sources are never connected together at the same time. Where the category as a whole covers generation, this specific unit is about the handover: making sure the changeover happens without a blackout and without back-feeding shore cables that were never designed to carry ship-generated current.
Main components
Connector assembly
The physical plug and socket, built to a recognised marine shore connection standard so that different ports and different ships can mate with the same hardware. On larger vessels this is a high-voltage connector rated for several thousand volts; on coastal and harbour craft it is often a low-voltage industrial connector.
Changeover switchgear
A mechanically or electrically interlocked switch that only permits shore power to close once the ship's generator breakers are open, and vice versa. This is the safety core of the box.
Protection relays
Over/under voltage, over/under frequency and earth fault protection, because shore supply quality varies far more than a ship's own generators.
Frequency and voltage matching
Where shore frequency does not match the ship's own (50 Hz shore supply feeding a 60 Hz vessel, or the reverse), a frequency converter sits between the box and the ship's switchboard. Voltage transformers cover the gap where shore voltage does not match ship voltage directly.
Earthing and bonding link
A dedicated earth conductor that bonds ship and shore hull potential before power is connected, preventing stray current corrosion and step-touch hazards on deck.
Selection / sizing
- Load to be carried while alongside (hotel load, reefer plugs, cargo pumps if applicable) sets the current rating.
- Shore supply voltage and frequency available at the intended ports of call.
- Connector standard expected by the terminal or berth.
- Cable length and whether a motorised cable reel is needed for cable management.
- Space and weight for the frequency converter, which is often the largest single item in the installation.
Regulations / Class
The high-voltage shore connection interface is standardised jointly by IEC, ISO and IEEE under IEC/ISO/IEEE 80005-1, covering connector geometry, interlocking sequence and safety earthing. MARPOL Annex VI does not mandate cold ironing directly but is the regulatory driver behind port and flag state incentives to fit it, since running generators alongside is a source of the emissions the annex targets. Where a class society issues a cold ironing notation, it will require type testing of the interlock logic and periodic survey of the connector and protection settings.
Typical faults
| Fault | Cause | Consequence |
|---|---|---|
| Interlock bypassed or defeated | Crew disables interlock to speed up connection | Risk of paralleling ship and shore sources out of phase, tripping both networks |
| Connector pitting | Repeated hot mating, salt spray, poor cleaning | Rising contact resistance, local heating, eventual burn-through |
| Earth link connected after power | Wrong sequence during connection | Hull potential difference during make-up, corrosion and shock risk |
| Frequency converter fault | Overload or cooling fan failure | Loss of shore power, forced return to generators |
What to look for in a supplier
- Certified compliance with IEC/ISO/IEEE 80005-1 rather than a proprietary connector design.
- Documented interlock logic that can be tested and verified during commissioning, not a black box.
- Track record supplying the specific port infrastructure the vessel actually trades to.
- Service support for the frequency converter, which is the component most likely to need specialist repair.
Never treat the interlock as optional even under time pressure at the berth. A wrong-sequence connection can trip switchboards on both the ship and the shore grid, and the yard or terminal will remember which vessel did it.
Typical Manufacturers
3 manufacturers · 3 models
ABB
1- Proven ABB reliability with long service life in harsh marine environments
- Integrated fault detection, earth‑leakage monitoring and remote diagnostics
- Modular design allows scalable current/voltage ratings to match vessel size
- Complies with IEC 60309 and IEC 60945 marine electrical standards out of the box
- Compact footprint simplifies installation in limited dockside space
- Higher capital cost compared with generic, non‑marine‑rated connectors
- Installation requires qualified ABB‑approved electricians and specific cable infrastructure
- Limited to the current/voltage ratings offered in the product line – may need multiple units for very large ships
- Spare parts inventory is vendor‑specific, potentially increasing lead times
ABB Marine (Finland/Switzerland)
1- OPS LV
- OPS MV
- Connection interface issues
- Transformer overload
- Frequency converter failure
- Integrated transformer + frequency converter in one compact unit simplifies installation
- Modular LV and MV versions allow matching the power rating of a wide range of ships
- High conversion efficiency (typically >95%) reduces losses and emissions
- Built‑in monitoring, diagnostics and remote service via ABB Marine Suite
- Designed to meet IEC/ISO shore‑power standards for safety and interoperability
- Significant upfront capital cost compared with basic static connectors
- Requires compatible ship‑side power electronics (e.g., ABB SPM or equivalent)
- Installation demands dedicated shore infrastructure and possible grid upgrades
- Maximum rating (≈10 MW) may be insufficient for the largest cruise ships or LNG carriers
- Transformer overload risk if vessel demand exceeds system rating without proper load management
Cavotec (Switzerland/Sweden)
1- SC 440V
- SC 6.6kV
- SC 11kV
- Connection plug/socket wear from repeated mating
- Cable insulation damage from handling
- Interlocking mechanism failure
- Shore-side frequency converter issues (50↔60 Hz)
- Earth fault from wet connection
- Three voltage families (440 V, 6.6 kV, 11 kV) cover most ship power requirements
- Built‑in frequency converter enables seamless 50 Hz ↔ 60 Hz compatibility
- Compact passive design with no moving parts reduces routine maintenance
- Integrated cable handling and interlock system simplifies safe mating/demating
- IEC/IEEE 80005‑1 compliance ensures interoperability across ports and vessels
- Only AC supply; ships requiring DC cold ironing need additional equipment
- Requires a compatible ship‑side inlet and matching voltage rating
- Interlocking mechanism can wear with frequent use, leading to occasional failures
- Higher‑voltage (6.6 kV/11 kV) units have larger footprint and heavier civil works
- Initial capital cost is higher than basic plug‑type connectors