Satish Kumar said:

when using stranded wires, appropriate terminals ought to be used, or, Class 5 or Class 6 conductors are to be terminated in terminals suitable only for Class 1 (solid) and/or Class 2 (stranded) they should be suitable prepared, for example with a ferrule. (See Regulation Group 526.9.)

This depends on terminal type.

to CENELEC standards:

• Terminals that have no marking can be assumed to be suitable for all classes of conductor, although you might want to use ferrules for class 5 and class 6 stranded conductors if they are to be regularly disconnected and reconnected, or where installation and maintenance activities would be slowed down drastically by having to re-strip to reconnect (for example industrial control panels, alarm systems, etc.)
• Terminals marked 'r' are suitable for rigid conductors (class 1 and class 2 only). Class 5 and Class 6 stranded conductors may be terminated if crimp ferrules can be used (although manufacturer's instructions should be followed for screwless terminals).
• Terminals marked 'sol' are suitable for class 1 (solid) conductors only. If manufacturers instructions permit, class 2, 5 and 6 conductors might be connected using crimp ferrules.
• Terminals marked 'f' may only be used for class 5 and class 6 stranded (flexible and extra-flexible respectively) conductors. Ferrules should not be used for Class 5 and Class 6 stranded conductors in terminals marked 'f'

Thanking you very much Graham for the reply. Grateful to clarify on the definition of heavy duty, Ordinary duty, Light duty cables based on BS EN 50565-01.

Really appreciated your answer regarding the type of application these cables are in.

Thanks & Regards,

Satish Kumar

Thanks Graham for above explanation.

Satish Kumar said:

Really appreciated your answer regarding the type of application these cables are in.

No problem - for once, this is pretty much paraphrased from the standard itself, which provides the real-world examples for these categories.