@hamje32 - I learned current transformer basics back in college, but I had never actually seen them in operation. I did visit a substation once but we only saw the electrical relays. The relays are used to detect fault conditions, from what the engineer who worked there told me,
I think transformers are used to detect those spikes in electricity, like you said, before they set the relay off. That’s what I remember anyway.
I do agree that being able to measure electricity without sticking your finger in the socket, so to speak, is very useful.