ACB / MCCB / VCB — Selection, Settings & Failure Modes
Why “a breaker is a breaker” is an ETO career-ending belief Introduction — protective devices are life-safety devices Breakers are often discussed as reliability equipment (“stops nuisance trips”, “keeps power on”). That is only half their job. On ships, breakers are also: A breaker that trips too easily is annoying. A breaker that trips too […]
Busbars, Segregation & Internal Arc Behaviour
Why a switchboard is a pressure vessel in disguise Introduction — the switchboard is the ship’s electrical “engine room” On a modern vessel, the main LV switchboard and MCCs are not just distribution hardware. They are the primary fault-energy containment system for the ship. When something goes wrong, your switchboard either (a) contains the event […]
AC vs DC Systems
Why DC quietly causes the most persistent faults onboard Introduction — DC doesn’t trip the way AC does DC systems are often described as “simple” because there is no frequency or phase. In practice, DC is harder to interrupt, harder to detect faults in, and easier to misunderstand. On ships, DC systems power: When DC […]
230 / 400 / 440 V Shipboard Distribution Systems
Why “low voltage” is the most dangerous phrase onboard Introduction — LV hurts more people than HV Most electrical injuries at sea occur on low-voltage systems, not HV. The reasons are simple: On ships, 440 V can deliver enormous fault current due to low impedance and close-coupled generators. Treating LV casually is how routine jobs […]
HV Interlocking Logic & Racking Operations
Why interlocks prevent fatal mistakes — until people defeat them Introduction — interlocks exist because people make predictable errors HV interlocks are not optional safety extras. They exist because history showed that humans will: Interlocks turn unsafe intent into mechanical impossibility — unless someone disables them. What interlocks are designed to prevent A properly designed […]
Marine HV Switchgear
Marine HV Switchgear — Construction, Compartments & Failure Modes Introduction — HV switchgear is designed to be boring Marine HV switchgear is engineered to sit untouched for years, operating flawlessly in the background. When it does require attention, it is usually during maintenance, configuration changes, or abnormal conditions — exactly when human interaction increases risk. […]
Testing for Dead, Induced Voltage & Capacitive Charge
Why “isolated” is meaningless until you prove zero energy Introduction — the most dangerous voltage is the one you don’t expect Electrical fatalities at sea often share a common phrase in investigation reports: “The circuit was believed to be dead.” Belief has no electrical value.Only measured absence of energy matters. What “test-before-touch” really means Testing […]
High-Voltage Permits, Interlocks & Earthing Procedures
Why HV systems forgive nothing — and why procedure is the control Introduction — HV doesn’t fail often, but when it does it ends careers High-voltage systems (typically 3.3–11 kV AC onboard) are designed to be robust and rarely operated. That reliability creates a dangerous illusion: because HV equipment “never causes trouble,” crews assume it […]
Arc-Flash Boundaries, PPE & Live-Work Reality
Why “it’s only 440 V” keeps injuring ETOs Introduction — voltage doesn’t cause arc flash, energy does Arc-flash injuries are not caused by high voltage.They are caused by high fault current and slow clearing times. Ships combine: This makes even LV systems extremely dangerous. What arc-flash actually is An arc fault: In a ship’s switchboard […]
Short-Circuit Levels & Fault Energy on Ships
Why the same spanner mistake ashore becomes an explosion at sea Introduction — fault energy is what kills and burns, not voltage Most people fear voltage because it’s easy to picture. But in switchboards, the severity of an event is driven by available fault current and fault clearing time — the energy that turns copper […]