Open Phase Protection For Transformer, Lines Or Generators And Circuit Breaker Head Flashover Protection For Generators - ABB REB670 Applications Manual

Section 10
Multipurpose protection
10.1.3.4
268
Proper timing of CVGAPC function made in this way can easily be verified by secondary
injection. All other settings can be left at the default values. If required delayed time reset
for OC1 step can be set in order to insure proper function operation in case of repetitive
overload conditions.
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.
Open phase protection for transformer, lines or generators and circuit
breaker head flashover protection for generators
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 PickupCurr_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.
1MRK 505 337-UUS -
Application manual