Shore Power / Cold Ironing

2 February 2026 3 min read Electrical, Latest Articles

Why Plugging In Is One of the Highest-Risk Electrical Operations on a Ship

Introduction — shore power looks simple until it isn’t

Cold ironing is often presented as a clean, environmentally friendly upgrade: shut down generators, connect shore power, reduce emissions. In practice, shore connection is one of the most technically complex and failure-prone power transfers a ship performs.

Unlike generator paralleling:

the shore grid does not forgive mistakes,
fault levels are enormous,
frequency/voltage assumptions differ,
and errors happen at the exact moment crew are physically close to live equipment.

What shore power actually involves (beyond the socket)

A proper shore connection must manage:

voltage level compatibility (6.6 kV / 11 kV / 400–440 V)
frequency matching (50 vs 60 Hz)
earthing philosophy differences (TN vs ship IT)
phase sequence verification
interlocks preventing back-feeding
load transfer without blackout or surge

This is not a “plug and play” operation — it is a controlled system handover.

🔧 Regulatory anchors (explicit)

IEC/IEEE 80005 (High Voltage Shore Connection – HVSC)

Defines:

design of shore connection systems
interlocking requirements
earthing and bonding arrangements
connection/disconnection sequences

Compliance is mandatory where HV shore power is fitted.

SOLAS Chapter II-1, Regulation 45

“Electrical installations shall be arranged so as to minimize the risk of fire and electric shock.”

Shore connections fall squarely under this requirement.

Class Rules (IACS E11 aligned)

Class expects:

certified shore connection equipment
documented operating procedures
crew training and drills
interlocks tested and functional

PSC inspections now routinely check shore power readiness, not just availability.

Why shore power failures are dangerous

Typical hazards include:

back-feeding the shore grid from ship generators
earthing faults due to mismatched grounding systems
uncontrolled inrush currents during transfer
incorrect phase sequence causing motor reversal
human proximity to high fault energy during connection

Unlike onboard systems, shore faults escalate instantly.

🔻 Real-World Case: Port of Los Angeles — Shore Power Back-Feed Incident

At the Port of Los Angeles, a container vessel experienced a serious electrical incident during shore power connection when:

shore breaker closed before ship isolation was confirmed
interlocks were bypassed to “save time”
ship and shore systems momentarily paralleled unintentionally

Result:

severe arcing at the shore connection
damage to connectors
port operations halted
vessel delayed and inspected

No injuries occurred — largely due to distance — but the potential fault energy exceeded onboard generator capability by orders of magnitude.

Earthing — the silent killer in shore connections

Ships often operate IT systems. Shore grids are usually TN-S or TN-C-S.

Without proper isolation:

fault currents take unintended paths
hull becomes part of the return circuit
shock risk increases dramatically
corrosion accelerates

IEC/IEEE 80005 requires dedicated earthing transformers or isolation arrangements to prevent this.

Professional ETO mindset

Before connecting shore power, a competent ETO asks:

What is the shore fault level?
Is phase sequence verified independently?
Is the ship fully isolated from generation?
Are interlocks active or bypassed?
Where is the crew standing when breakers close?

Cold ironing reduces emissions — but increases electrical risk if mishandled.

Knowledge to Carry Forward

Shore power is not auxiliary power. It is an external grid with massive fault energy and zero tolerance for error.

Every shore connection must be treated as:

a high-risk switching operation,
a human-exposed task,
and a system-level power transfer.

If interlocks stop you — listen to them.