I knew I was missing something important when as a mid-level electrical engineer, I used to wonder which voltage value I should be using in my calculations. Was it 110V, 115V, 117V, or 120V? Was it 208V, 220V, 230V, or 240V? Was it 120/240V, 240/120V, 120/208V, 208/120V, 277/480V, or 480/277V?
When it comes to the proper way to write system voltages, first you have to know which voltage you’re actually talking about.