Why Does Transformer Secondary L2-G Read 0V While L1-G and L3-G Read 200V?

Hi.
During checking of our power supply, I have this reading which I am not sure if this is a problem or not. It is my first time to encounter this kind of supply. See below reading of transformer secondary output.
L1 - L2 = 200V                                        L1 - G = 200V
L2 - L3 = 200V                                       L2 - G = 0V
L1 - L3 = 200V                                        L3 - G = 200V
I am confused why the reading of L2 - G is 0V but the others are 200V. Also, I believe that if my L1 - G and L3 - G is 200V, the reading of L1 - L3 will be higher than 200V. Hope somebody here can answer my query. 



Thanks,
Edward

Edward, these readings do not make sense.I'm assuming thins is a 3-phase AC system (you don't specifically state this though you do mention a transformer)??In that case if Line-Neutral voltage is 200V you would assume that Line-Line would be200 * Sqrt 3 = 340VSo even if your L2-G was 200V I would question these readings.And if your L2 is ground and you have a 2-phase system (which is used in some places) then you'd expect L1-L3 to be 400V.Are you sure there is not something else going on here, maybe a meter that only reads max. 200v, or something?  There is no way I can make these readings make sense otherwise.....