I'm an electrical engineering student and I'm currently in In-Plant training in Electricity Company of my country. Recently I visited an electrical grid. I got to know about Earthing transformer. I asked an engineer about how the current flows to the ground in a delta connection as it's not grounded and to flow current there must be a return path to the source. But she didn't give me a satisfying answer, she said there will be current flowing and said that current flows from high potential to low potential (zero potential earth). However I had doubts since that time because unlike in star connection (grounded), there is no path for return current in delta system (with ground I meant).
I know that an earthing transformer creates a virtual ground to current flow in delta system to the virtual ground, so they can measure earth faults for tripping. But it is not clear to me how current flows to the ground if there's no earthing transformer.
I saw in some post saying that this is due to inductive coupling. I'm talking about a 33kV delta system. Since current flows through a closed system, why is this possible?
I'm talking about ungrounded delta system, no neutral, no leg is connected to ground and no earthing transformer. Fully isolated Delta connection. So I want to know how and why current flows to the ground in an earth-fault/1-phase touch earth in a delta-system. In theory it must be zero as there's no return path to the source?