We have a 480V 3-phase connection for a borehole pump, and we need to get a temporary 240V connection for lighting, no more than a few hundred watts.
We are in South Africa which operates at 240V, and when measuring each phase on the 3-phase line we get 480V RMS.
To get 240V, we measured one of the phases and neutral, which gives exactly 240V RMS as we want, however this goes against my research online that it should be 277V RMS.
Is it safe to use this? Is this normal, or are the phases at a different angle perhaps? All three phases give 240V in reference to neutral.
The three phase line has the following colours, the same as the UK:
Edit: To clarify, I'm 100% certain that any connection between the three phases is always 480V and at least one connection between a phase and neutral is 240V, I'll do some more testing with the other phases to see if they also give 240V when measured against neutral.
Edit 2: The supply turned out to be a High Leg Delta type, as mentioned in the answer, and I am getting 240V successfully, working great.