1. set k equal to the IEC or ANSI standard generator capability value2. set parameter A_OC1 equal to the value 1/x23. set parameter C_OC1 equal to the value 1/x24. set parameters B_OC1 = 0.0 and P_OC1=2.05. set StartCurr_OC1 equal to the value xthen the OC1 step of the CVGAPC function can be used for generator negativesequence inverse overcurrent protection.1. select positive sequence current as measuring quantity for this CVGAPCfunction2. make sure that the base current value for CVGAPC function is equal to thegenerator rated current3. set k = 37.5 for the IEC standard or k = 41.4 for the ANSI standard4. set A_OC1= 1/1.162 = 0.74325. set C_OC1= 1/1.162 = 0.74326. set B_OC1 = 0.0 and P_OC1 = 2.07. set StartCurr_OC1 = 116%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 functionoperation in case of repetitive overload conditions.Furthermore the other built-in protection elements can be used for other protectionand alarming purposes.In the similar way rotor overload protection in accordance with ANSI standard canbe achieved.12.1.3.4 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 moresecure it is possible to restrain it by requiring that at the same time the measuredunbalance current must be bigger than 97% of the maximum phase current. Bydoing this it will be insured that function can only pickup if one of the phases isopen circuited. Such an arrangement is easy to obtain in CVGAPC function byenabling the current restraint feature. The following shall be done in order to insureproper operation of the function:1. Connect three-phase currents from the protected object to one CVGAPCinstance (for example, GF03)2. Set CurrentInput to value UnbalancePh3. Set EnRestrainCurr to On4. Set RestrCurrInput to MaxPh5. Set RestrCurrCoeff to value 0.971MRK 506 369-UEN B Section 12Multipurpose protectionLine distance protection REL670 2.2 IEC 577Application manual
