Application of protection systems, stipulated by the standards, in installations comprising a UPS, requires a number of precautions for the following reasons:

The UPS plays two roles

-  A load for the upstream system
-  A power source for downstream system

When the battery is not installed in a cabinet, an insulation fault on [...]

Types of static UPSs are defined by standard IEC 62040.
The standard distinguishes three operating modes:

Passive standby (also called off-line) Line interactive Double conversion (also called on-line)

These definitions concern UPS operation with respect to the power source including the distribution system upstream of the UPS.
Standard IEC 62040 defines the following [...]

The disturbances presented above may affect:

Safety of human life Safety of property The economic viability of a company or production process

Disturbances must therefore be eliminated.
A number of technical solutions contribute to this goal, with varying degrees of effectiveness. These solutions may be compared on the basis of two criteria:

Availability of [...]

Parallel-connection of the generator set irrespective of the application type – Safety source, Replacement source or Production source – requires finer management of connection, i.e. additional monitoring functions.

Parallel operation

As generator sets generate energy in parallel on the same load, they must be synchronised properly (voltage, frequency) and load distribution must [...]

Priority circuit protection

Choice of breaking capacity

This must be systematically checked with the characteristics of the main source (MV/LV transformer).

Setting of the Short Time Delay (STD) tripping current

Subdistribution boards

The ratings of the protection devices for the subdistribution and final distribution circuits are always lower than the generator rated current. Consequently, except [...]