TRANSFORMER SECONDARY GROUNDING
Hello everyone. I will be working with a 10KVA transformer that will step down 460V to 230V. I understand per NEC 450 that if I size my OCPD at 125% of the rated primary current (which is 20A for this transformer), then I do not need to fuse the secondary. What risks do I take by not fusing the secondary? Do the fuses have to be at the transformer or can the by at the service disconnect?
Also, I am used to working with smaller control transformers (1...2..3KVA) where we ground one of the secondary phases. This 10KVA transformer has 120/240 available on the secondary, but I will only use the 240V. Do I still need to ground one of the secondary phases? I understand that the secondary is electrically isolated from the primary, and that any ground faults on the secondary will need the grounded secondary phase....I am just not sure if I need to always have a secondary phase grounded, or only for lower secondary voltages.
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