www.maritimeindustries.org
The Lightning Fast Airbag for your Low Voltage Switchboard – Aboard
Derek Bryans Eaton Electric Limited
Safety as a design criterion for seagoing vessels and shipping systems will be a major factor in determining the requirements of the shipbuilding process in future – from the design phase to approval, production, commissioning, supply and operation, including the logistics aspects up to service and maintenance. International efforts to draw up new ship‐ building regulations with a risk‐based approach as well as the European SAFEDOR
research project also indicate this trend. The potential hazards resulting from an arc fault in low‐voltage power distribution systems on ships are enormous. An arc fault protection system offers effective protection against this.
Protecting Crew & Systems Whilst Ensuring Service Continuity
A bolted short‐circuit on a switchboard designed in compliance with the regulations is required not to lead to any restriction in the ship’s operation after the leakage current is removed.
Without doubt, however, short circuits that occur together with arcs in switchboards and distribution systems have the most devastating consequences. Arc faults still occur in electrical power distribution systems despite all the precautionary measures taken, and are mainly caused by crew members when working on a low‐voltage power distribution system.
Function of arc fault protection systems
In the event of an arc fault, the air pressure and temperature reach their maximum values within 10‐15 ms so that the arc fault can very well be compared to an explosion. As the electrical characteristics depend on the conditions at hand, such as generator output or the length of the connection cables, only the duration of the arc fault is a controllable variable. The quenching device de‐energises the arc fault in only two milliseconds – long before any serious damage to persons or to the switchboard can occur.
The light emitted from the arc fault, as well as its short‐circuit current are detected by special sensors and transferred to the evaluation device. If both detection variables exceed certain specified threshold values at the same time, the evaluation unit triggers the quenching device. The device produces a three‐phase bolted short‐circuit as close as possible to the incoming supply and parallel to the fault location. The incoming circuit‐breaker also only isolates the section of the system that is affected. All unaffected areas are kept in operation. The flexibility of the Central Evaluation Unit fully meets the selectivity requirements in marine power supply systems. Once the causes of the fault have been rectified and the quenching device replaced, the switchboard is ready for service without any restriction.
Conclusion Low Voltage Distribution Board – ARC Flash on‐board a vessel 22
Prof. Dr. Ing. Wilfried Hensel, Maritime Consultant, summarises: “The arc fault protection system makes a substantial contribution to increased safety for power distribution systems on seagoing vessels. It covers both IMO requirements with regard to the protection of human life and the environment, as well as the
Society of Maritime Industries Annual Review 2018
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