Classification alert: Harmonic distortion for ship electrical distribution systems, including harmonic filters.
20 October 2017
Applicability: Ships where harmonic filters are installed within the electrical power system.
In order to detect deterioration in the harmonic filters at an early stage, a new requirement has been introduced by IACS (UR E24) to monitor and record the harmonic distortion levels occurring within the ship’s electrical power system. Early detection of any deterioration of harmonic filter components would minimise the risk of catastrophic failure occurring that could be dangerous both for persons (fatalities and injuries) and for the ship (blackout, fire or explosion). Therefore, it is essential to carry out regular harmonic distortion measurements, to detect an incipient failure and allow corrective actions to be taken.
For vessels where harmonic filters are fitted, the harmonic distortion level is to be measured annually under seagoing conditions and after any modification to the electrical distribution system or associated consumers.
Vessels contracted for construction on or after 1 July 2017 are to be equipped with means to continuously monitor the level of harmonic distortion.
Vessels contracted for construction before 1 July 2017 that are not equipped with facilities to continuously monitor the level of harmonic distortion may use temporarily installed measurement equipment. This equipment, used under seagoing conditions by suitably qualified and trained personnel, is to be able to monitor the harmonic distortion on the main bus bars when the greatest amount of distortion is occurring.
The records of harmonic distortion measurements are to be made available to the attending surveyor at each periodical survey.
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