ECN Forum Forums General Topics of the Trade General Discussion Area Transformer Secondary

And again I will say that the secondary of the transformer itself does not require protection if the primary protection is sized at 125% or less of the rated primary current. There is no question that protection of the secondary conductors is required, except in the two special cases you cited. My issue is only with the choice of words, as the end result is the same...there will be an OCPD on the secondary side of the transformer, but it is often only for the protection of the secondary conductors and not for the protection of the secondary winding. Article 450 only applies to the transformer itself. Article 240 only applies to the protection of the conductors and not to the protection of the transformer. Even your quote from the handbook states "transformer secondary conductors must be protected by the use of over-current devices".