GMP 10 kVA Manual Del Usario página 81

Separate bypass:
if the separate bypass option is present, protective devices must be present on both the main power supply line and the bypass
line.
Note: the neutral of the input line and that of the bypass are commoned inside the equipment, so they must refer to the same
potential. If the two power supplies were different, an isolation transformer would have to be used on one of the inputs.
UPS without any variation in neutral condition and with separate bypass input
connected to independent power supply line
UPS with separate bypass input on independent power supply line
and with galvanic isolation at input
UPS with separate bypass input connected to independent power supply line
and with galvanic isolation at output