Light fixture earthing wires
Over here in the Netherlands we have the same problem.
Simply connect the Neutral and switch wire to the armature and if no earth wire is available leave the one from the armature disconnected.

Most probably you have earth fault detection breakers in the switchboard. 

That is the case if you find a small button on the breaker.
Most probably you can find also the remark of 0,03A or 30 mA.

In such cases the breaker trips if there is a defect resulting in more than 30 mA difference in current from the line to the neutral.