Open Phase Protection For Transformer, Lines Or Generators And Circuit Breaker Head Flashover Protection For Generators - ABB RELION RET670 Applications Manual

Section 12
Multipurpose protection
12.1.3.4
656
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 504 163-UUS A
Transformer protection RET670 2.2 ANSI
Application manual
M13088-142 v3