NFPA 70 Article 240 Describes Overcurrent Protection
Article 240.4 states that conductors shall be protected against overcurrent in accordance with their ampacities.
There are several exceptions to this rule.
One is article 240.4 (F) for Transformer Secondary Conductors ? There are two exceptions listed in this article:
1. Where the transformers primary and secondary are both connected delta-delta.
2. Single-phase two wire primary and two wire secondary
Article 240.21 (C) Specifically describes Exceptions to Transformer Secondary Protection.
240.21(C) (4) Allows no protection of a transformer secondary conductors if they are located outside.
SPECIFIC APPLICATION
? 1500 kVA Transformer located outdoors. Primary voltage 25 kV, Secondary Voltage 480
? Transformer is Delta-Connected primary, and WYE-Connected Secondary
? There is Primary protection
? Secondary conductors are approximately 75 feet long, and terminate in a set of fuses rated for their ampacity. (All located outdoors, adequately protected, and accessible.)
Question ?
Are we in violation of the code by not having protection of the secondary conductors between the transformer and the fuses?
Article 240.4 (F) suggests that they are required
Article 240.21 (C) (4) suggests that it is not required
Article 240.4 states that conductors shall be protected against overcurrent in accordance with their ampacities.
There are several exceptions to this rule.
One is article 240.4 (F) for Transformer Secondary Conductors ? There are two exceptions listed in this article:
1. Where the transformers primary and secondary are both connected delta-delta.
2. Single-phase two wire primary and two wire secondary
Article 240.21 (C) Specifically describes Exceptions to Transformer Secondary Protection.
240.21(C) (4) Allows no protection of a transformer secondary conductors if they are located outside.
SPECIFIC APPLICATION
? 1500 kVA Transformer located outdoors. Primary voltage 25 kV, Secondary Voltage 480
? Transformer is Delta-Connected primary, and WYE-Connected Secondary
? There is Primary protection
? Secondary conductors are approximately 75 feet long, and terminate in a set of fuses rated for their ampacity. (All located outdoors, adequately protected, and accessible.)
Question ?
Are we in violation of the code by not having protection of the secondary conductors between the transformer and the fuses?
Article 240.4 (F) suggests that they are required
Article 240.21 (C) (4) suggests that it is not required