ABB REB670 Series, Applications Manual

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Furthermore the other built-in protection elements can be used for other protection and
alarming purposes.
In the similar way rotor overload protection in accordance with ANSI standard can be achieved.
10.1.3.4 Open phase protection for transformer, lines or generators and circuit
breaker head flashover protection for generators
M13088-142 v3
Example will be given how to use one CVGAPC function to provide open phase protection. This
can be achieved by using one CVGAPC function by comparing the unbalance current with a pre-
set level. In order to make such a function more secure it is possible to restrain it by requiring
that at the same time the measured unbalance current must be bigger than 97% of the
maximum phase current. By doing this it will be insured that function can only pickup if one of
the phases is open circuited. Such an arrangement is easy to obtain in CVGAPC function by
enabling the current restraint feature. The following shall be done in order to insure proper
operation of the function:
1. Connect three-phase currents from the protected object to one CVGAPC instance (for
example, GF03)
2. Set
CurrentInput to value UnbalancePh
3. Set
EnRestrainCurr to On
4. Set
RestrCurrInput to MaxPh
5. Set
RestrCurrCoeff to value 0.97
6. Set base current value to the rated current of the protected object in primary amperes
7. Enable one overcurrent step (for example, OC1)
8. Select parameter CurveType_OC1 to value IEC Def. Time
9. Set parameter
StartCurr_OC1 to value 5%
10. Set parameter
tDef_OC1 to desired time delay (for example, 2.0s)
Proper operation of CVGAPC function made in this way can easily be verified by secondary
injection. All other settings can be left at the default values. However it shall be noted that set
values for restrain current and its coefficient will as well be applicable for OC2 step as soon as
it is enabled.
Furthermore the other built-in protection elements can be used for other protection and
alarming purposes. For example, in case of generator application by enabling OC2 step with
set pickup to 200% and time delay to 0.1s simple but effective protection against circuit
breaker head flashover protection is achieved.
10.1.3.5 Voltage restrained overcurrent protection for generator and step-up
transformer
M13088-158 v4
Example will be given how to use one CVGAPC function to provide voltage restrained
overcurrent protection for a generator. Let us assume that the time coordination study gives
the following required settings:
• Inverse Time Over Current TOC/IDMT curve: ANSI very inverse
• Pickup current of 185% of generator rated current at rated generator voltage
• Pickup current 25% of the original pickup current value for generator voltages below 25%
of rated voltage
This functionality can be achieved by using one CVGAPC function. The following shall be done
in order to ensure proper operation of the function:
1MRK 505 370-UEN D Section 10
Multipurpose protection
Busbar protection REB670 235
Application manual