6. 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 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 bysecondary injection. All other settings can be left at the default values. However itshall be noted that set values for restrain current and its coefficient will as well beapplicable for OC2 step as soon as it is enabled.Furthermore the other built-in protection elements can be used for other protectionand alarming purposes. For example, in case of generator application by enablingOC2 step with set pickup to 200% and time delay to 0.1s simple but effectiveprotection against circuit breaker head flashover protection is achieved.6.1.3.5 Voltage restrained overcurrent protection for generator and step-uptransformer M13088-158 v4Example will be given how to use one CVGAPC function to provide voltagerestrained overcurrent protection for a generator. Let us assume that the timecoordination 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 voltagesbelow 25% of rated voltageThis functionality can be achieved by using one CVGAPC function. The followingshall be done in order to ensure proper operation of the function:1. Connect three-phase generator currents and voltages to one CVGAPC instance(for example, GF05)2. Set CurrentInput to value MaxPh3. Set VoltageInput to value MinPh-Ph (it is assumed that minimum phase-to-phase voltage shall be used for restraining. Alternatively, positive sequencevoltage can be used for restraining by selecting PosSeq for this settingparameter)4. Set base current value to the rated generator current primary amperes5. Set base voltage value to the rated generator phase-to-phase voltage in kV6. Enable one overcurrent step (for example, OC1)7. Select CurveType_OC1 to value ANSI Very inv8. If required set minimum operating time for this curve by using parametertMin_OC1 (default value 0.05s)9. Set StartCurr_OC1 to value 185%10. Set VCntrlMode_OC1 to On11. Set VDepMode_OC1 to SlopeSection 6 1MRK 511 423-UEN AMultipurpose protection86 Bay control REC650 2.2 IECApplication manual
