Equipment Protection, Such As For Motors, Generators Reactors And Transformers - ABB REC670 Applications Manual

Section 9
Voltage protection
9.2.3.1
9.2.3.2
9.2.3.3
9.2.3.4
9.2.3.5
232
which is normally set to the nominal voltage level (phase-to-phase) of the power
system or the high voltage equipment under consideration.
The time delay for the OV2PTOV can sometimes be critical and related to the size
of the overvoltage - a power system or a high voltage component can withstand
smaller overvoltages for some time, but in case of large overvoltages the related
equipment should be disconnected more rapidly.
Some applications and related setting guidelines for the voltage level are given
below:
The hysteresis is for overvoltage functions very important to prevent that a
transient voltage over set level is not "sealed-in" due to a high hysteresis. Typical
values should be ≤ 0.5%.
Equipment protection, such as for motors, generators, reactors and
transformers
High voltage will cause overexcitation of the core and deteriorate the winding
insulation. The setting has to be well above the highest occurring "normal" voltage
and well below the highest acceptable voltage for the equipment.
Equipment protection, capacitors
High voltage will deteriorate the dielectricum and the insulation. The setting has to
be well above the highest occurring "normal" voltage and well below the highest
acceptable voltage for the capacitor.
Power supply quality
The setting has to be well above the highest occurring "normal" voltage and below
the highest acceptable voltage, due to regulation, good practice or other
agreements.
High impedance earthed systems
In high impedance earthed systems, earth-faults cause a voltage increase in the
non-faulty phases. Two step overvoltage protection (OV2PTOV) is used to detect
such faults. The setting must be above the highest occurring "normal" voltage and
below the lowest occurring voltage during faults. A metallic single-phase earth-
fault causes the non-faulted phase voltages to increase a factor of √3.
The following settings can be done for the two step overvoltage
protection
ConnType: Sets whether the measurement shall be phase-to-earth fundamental
value, phase-to-phase fundamental value, phase-to-earth RMS value or phase-to-
phase RMS value.
1MRK 511 401-UEN A
M13852-10 v3
M13852-13 v1
M13852-16 v1
M13852-19 v6
M13852-22 v10
Bay control REC670 2.2 IEC
Application manual