Setting Guidelines; Equipment Protection, Such As For Motors And Generators; Disconnected Equipment Detection; Power Supply Quality - ABB REQ650 Applications Manual

Section 7
Voltage protection
7.1.3
7.1.3.1
7.1.3.2
7.1.3.3
7.1.3.4
7.1.3.5
156
UV2PTUV prevents sensitive equipment from running under conditions that could
cause their overheating and thus shorten their life time expectancy. In many cases, it
is a useful function in circuits for local or remote automation processes in the power
system.

Setting guidelines

All the voltage conditions in the system where UV2PTUV performs its functions
should be considered. The same also applies to the associated equipment, its voltage
and time characteristic.
There is a very wide application area where general undervoltage functions are used.
All voltage related settings are made as a percentage of the global settings base voltage
UBase, which normally is set to the primary rated voltage level (phase-to-phase) of the
power system or the high voltage equipment under consideration.
The setting for UV2PTUV is normally not critical, since there must be enough time
available for the main protection to clear short circuits and earth faults.
Some applications and related setting guidelines for the voltage level are described in
the following sections.

Equipment protection, such as for motors and generators

The setting must be below the lowest occurring "normal" voltage and above the lowest
acceptable voltage for the equipment.

Disconnected equipment detection

The setting must be below the lowest occurring "normal" voltage and above the
highest occurring voltage, caused by inductive or capacitive coupling, when the
equipment is disconnected.

Power supply quality

The setting must be below the lowest occurring "normal" voltage and above the lowest
acceptable voltage, due to regulation, good practice or other agreements.

Voltage instability mitigation

This setting is very much dependent on the power system characteristics, and
thorough studies have to be made to find the suitable levels.

Backup protection for power system faults

The setting must be below the lowest occurring "normal" voltage and above the
highest occurring voltage during the fault conditions under consideration.
1MRK 505 291-UEN A
Application manual