Proper timing of CVGAPC function made in this way can easily be verified bysecondary injection. All other settings can be left at the default values. If requireddelayed time reset for OC1 step can be set in order to insure proper function operationin case of repetitive overload conditions.Furthermore the other built-in protection elements can be used for other protection andalarming purposes.In the similar way rotor overload protection in accordance with ANSI standard can beachieved.10.1.3.4 Open phase protection for transformer, lines or generators and circuitbreaker head flashover protection for generators M13088-142 v3Example will be given how to use one CVGAPC function to provide open phaseprotection. This can be achieved by using one CVGAPC function by comparing theunbalance current with a pre-set level. In order to make such a function more secure itis possible to restrain it by requiring that at the same time the measured unbalancecurrent must be bigger than 97% of the maximum phase current. By doing this it willbe insured that function can only pickup if one of the phases is open circuited. Such anarrangement is easy to obtain in CVGAPC function by enabling the current restraintfeature. 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 UnbalancePh3. Set EnRestrainCurr to On4. Set RestrCurrInput to MaxPh5. Set RestrCurrCoeff to value 0.976. Set base current value to the rated current of the protected object in primaryamperes7. Enable one overcurrent step (for example, OC1)8. Select parameter CurveType_OC1 to value IEC Def. Time9. 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 bysecondary injection. All other settings can be left at the default values. However it shallbe noted that set values for restrain current and its coefficient will as well be applicablefor OC2 step as soon as it is enabled.Furthermore the other built-in protection elements can be used for other protection andalarming purposes. For example, in case of generator application by enabling OC2 stepwith set pickup to 200% and time delay to 0.1s simple but effective protection againstcircuit breaker head flashover protection is achieved.Section 10 1MRK 505 370-UUS AMultipurpose protection280 Busbar protection REB670 2.2 ANSIApplication manual
