ABB RET670 Applications Manual page 556

Section 3
IED application
550
or Reverse). Its behavior during low-level polarizing voltage is settable (Non-
Directional,Block,Memory)
• Voltage restrained/controlled feature is available in order to modify the pick-
up level of the overcurrent stage(s) in proportion to the magnitude of the
measured voltage
• Current restrained feature is available in order to only allow operation of the
overcurrent stage(s) if the measured current quantity is bigger than the set
percentage of the current restrain quantity.
2. Two undercurrent steps with the following built-in features:
• Definite time delay for both steps
3. Two overvoltage steps with the following built-in features
• Definite time delay or Inverse Time Overcurrent TOC/IDMT delay for both
steps
4. Two undervoltage steps with the following built-in features
• Definite time delay or Inverse Time Overcurrent TOC/IDMT delay for both
steps
All these four protection elements within one general protection function works
independently from each other and they can be individually enabled or disabled.
However it shall be once more noted that all these four protection elements measure
one selected current quantity and one selected voltage quantity (see table
table 143). It is possible to simultaneously use all four-protection elements and their
individual stages. Sometimes in order to obtain desired application functionality it is
necessary to provide interaction between two or more protection elements/stages
within one CVGAPC function by appropriate IED configuration (for example, dead
machine protection for generators).
Current and voltage selection for CVGAPC function
CVGAPC function is always connected to three-phase current and three-phase voltage
input in the configuration tool, but it will always measure only the single current and
the single voltage quantity selected by the end user in the setting tool (selected current
quantity and selected voltage quantity).
The user can select, by a setting parameter CurrentInput, to measure one of the
following current quantities shown in table 142.
Table 142: Available selection for current quantity within CVGAPC function
Set value for parameter
"CurrentInput"
PhaseA
1
2 PhaseB
PhaseC
3
Table continues on next page
Comment
CVGAPC function will measure the phase A current phasor
CVGAPC function will measure the phase B current phasor
CVGAPC function will measure the phase C current phasor
1MRK504116-UUS C
142 and
Application manual