IEC 61892-1 pdf download – Mobile and fixed offshore units — Electrical installations — Part 1: General requirements and conditions

IEC 61892-1 pdf download – Mobile and fixed offshore units — Electrical installations — Part 1: General requirements and conditions
4.3Applicability of the standards to a.c. and d.c.
Except where a specific statement is made to the contrary, the lEC 61892 series is equallyapplicable to equipment in all installations whether permanent，temporary，transportable orhand-held,for a.c. installations up to and including 35 o0o v and d.c. installations up to andincluding 1 500 v.
4.4Acceptance of substitutes or alternatives
Where in these standards any special type of equipment，construction，or arrangement isspecified, the use of any other equipment, construction or arrangement is admissible, providedit is not less effective and reliable.
4.5Provision for maximum load
All conductors,switchgear and accessories shall be of such size as to be capable of carrying,without their respective ratings being exceeded,the current which can normally flow throughthem. They shall be capable of carrying anticipated overloads and transient currents,forexample the starting currents of motors, without damage or reaching abnormal temperatures.
4.6Additions and alterations
An addition or alteration, temporary or permanent,shall not be made to an existing installationuntil it has been ascertained that the ratings and the condition of existing accessories,conductors, switchgear,etc. affected, are adequate for the new situation,
Special attention is drawn to those factors affecting the existing system design such as current-carrying capacity,short-circuit level，voltage drop， harmonics,，stability and proper discri-mination of the protective devices.
4.7 Environmental conditions4.7.1General
Electrical equipment shall operate satisfactorily under various environmental conditions.Environmental conditions are characterised by a number of variables:
one set including mainly climatic conditions,biological conditions，conditions dependentupon chemically and mechanically active substances and mechanical conditions;
another set dependent mainly upon locations in unit，operational patterns and transientconditions.
For guidance only,annex A gives a list of a limited number of environmental conditions inconjunction with some selected locations, operational patterns and transient conditions whichare considered to be generally representative.
4.7.2Design parameters
Design parameters based on environmental conditions applicable to certain types of equipmentmay be determined according to location. Where no data is available the following tables giverecommended values.
4.7.2.1emperature
ln other parts of lEC 61892,where no “high air temperature” has been specified as a designparameter for equipment, a value of 45 C shall apply.
Where equipment is designed to operate with temperatures higher or lower than those stated,permissible temperature rises may be reduced or increased accordingly.
4.8Materials
In general, all electrical equipment shall be constructed of durable,flame-retardant，moisture-resistant materials，which are not subject to deterioration in the atmosphere and at thetemperatures to which they are likely to be exposed.
4.9Power supply system characteristics
4.9.1General
Unless otherwise stated in other parts of this standard,equipment shall function when suppliedfrom general distribution systems with due regard to voltage and frequency variations,harmonic distortion and conducted disturbances. The characteristics of general distributionsystems are given in the following subclauses.
NOTE 1 Where the power supply is obtained from the shore， due regard should be paid to the effect that thequality of the supply, if different from that specified in this clause,may have on the performance of equipment.
NOTE 2 For systems where semiconductors are connected having a total rating which is a significant portion ofthe total system rating, it may be feasible to suppress the harmonics. Consideration should be given to takingappropriate measures to attenuate these effects of the distribution system so that safe operation is assured. Careshould be taken in selecting consumers supplied from an electric power supply system with a higher harmoniccontent than specified in this clause.
NOTE 3 Electrical equipment which requires a higher quality power supply may need additional provisions to bemade locally. Where additional equipment is fitted to achieve this higher quality power supply it may be required tobe duplicated and segregated to the same degree as the electrical equipment it supplies.
NOTE 4 Special attention should be paid to the installation of electrical equipment which may influence the qualityof power supply on a local basis or react with any harmonics present on the general distribution system.
NOTE 5 Variable frequencylvoltage systems may be admissible provided safe operation of the system is assuredand equipment is suitably rated for the expected variations.