Lighting Transformer

Does it need to be, according to local codes? If so, earth it. If not, why worry?

I understand secondary of Lightiing trafo is always earthed. May be in some old systems unearthed system were used, but not popular now. on protection point of view earthed system is better.

If the transformers is an "Isolation Transformer" conforming to IEC 61558 then earthing or grounding the secondary is prohibited.

Greg Lynch

In industrial systems we (Canada) used to have an option for ungrounded systems IF there was adequate ground fault detection and alarm. This allowed a system to go to ground, alarm, and provide a period of time for repairs without taking the whole system down. This is the extreme case in limited special circumstances now, and it is now code to ground the systems, for increased safety reasons. First fault to ground blows the fuses and the system goes down. In damp locations and convenience locations ground fault protection is also required now, as in bathrooms and kitchens.The option for ground fault detection still occurs with 3 phase industrial systems where there may be high impedance or ungrounded systems, but the recommendation is to solidly ground the Y neutral or an artificial neutral for Delta systems.

The push to ground everything is based on the premise that it is safer for the average person. There will always be circumstances where the ungrounded systems will be used.

Another problem with ungrounded systems is a 3 phase system that becomes corner grounded causes the other 2 phases to now operate at a higher potential with respect to earth and cause higher insulation stress and a greater risk to people working on the system.