Equipment Protection, Such As For Motors, Generators Reactors And Transformers - ABB REG670 Applications Manual

Section 10
Voltage protection
10.2.3.1
10.2.3.2
10.2.3.3
10.2.3.4
10.2.3.5
408
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.
Operation: Off/On.
UBase (given in GlobalBaseSel): Base voltage phase to phase in primary kV. This
voltage is used as reference for voltage setting. OV2PTOV measures selectively
phase-to-earth voltages, or phase-to-phase voltage chosen by the setting ConnType.
The function will operate if the voltage gets lower than the set percentage of UBase.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
Application manual