Between where and where are you seeing line voltage, and at what impedance - the whole point is that it can 'float' however a dead short to earth anywhere is bad. if this is a 3 phase system I can well believe that the centre of the triangle will be near zero, so the line to earth voltage will seem close to line, due to all 3 line to ground capacitances being equal and having more or less equal voltages being the equilibrium condition/
Between where and where are you seeing line voltage, and at what impedance - the whole point is that it can 'float' however a dead short to earth anywhere is bad. if this is a 3 phase system I can well believe that the centre of the triangle will be near zero, so the line to earth voltage will seem close to line, due to all 3 line to ground capacitances being equal and having more or less equal voltages being the equilibrium condition/
How many phases have you got, and what voltages do you see on each of them ?
In the simple view, just measuring voltage draws no current, so no voltage drop even if loop impedance is infinite. A real volt meter is tens of megohms, but the real earth loop impedance is a bit uncertain but could easily be a few hundred k ohms, so ~ 2 orders of magnitude lower than your volt meter.
But add an impedance between 1 line and ground, that is a lot lower than that loop impedance combined with the reactance of the capacitance of the wiring (you can estimate that - how much wire have you got on each phase ? - allow 50-100pF per metre for small diameter stuff.) and if the system is IT, the loaded phase voltage to ground will drop away, and the others will rise to compensate and the loads wont notice as the line to line voltage is unaffected.
