HOLDTU> =200% (of SCB voltage rating); Voltage level required for pickuptHOLDT =10s; Definite time delay for harmonic overload tripSettings for IDMT delay stepHOLIDMTU> =110% (of SCB voltage rating); Voltage level required for pickup ofIDMT stage. Selected value gives pickup recommended by international standards.kHOLIDMT =1.0; Time multiplier for IDMT stage. Selected value gives operatetime in accordance with international standardstMaxHOLIDMT =2000s; Maximum time delay for IDMT stage for very low levelof harmonic overloadtMinHOLIDMT =0.1s; Minimum time delay for IDMT stage. Selected value givesoperate time in accordance with international standards8.15.3.1 Restrike detection GUID-114747A5-0F7C-4F48-A32D-0C13BFF6ADCE v1Opening of SCBs can be quite problematic for certain types of circuit breakers(CBs). Typically such problems are manifested as CB restrikes.In simple words this means that the CB is not breaking the current at the first zerocrossing after separation of the CB contacts. Instead current is re-ignited and onlybraked at consecutive current zero crossings. This condition is manifested as highcurrent pulses at the moment of current re-ignition.To detect this CB condition, the built in overcurrent feature can be used. Simply,any start of the overcurrent feature during breaker normal opening means arestrike. Therefore simple logic can be created in the Application Configurationtool to detect such CB behavior. Such CB condition can be just alarmed, and ifrequired, the built in disturbance recorder can also be triggered.To create this logic, a binary signal that the CB is going to be opened (but not tripcommand) shall be made available to the IED.8.16 Voltage-restrained time overcurrent protectionVRPVOC GUID-613620B1-4092-4FB6-901D-6810CDD5C615 v48.16.1 Identification GUID-7835D582-3FF4-4587-81CE-3B40D543E287 v4Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberVoltage-restrained time overcurrentprotectionVRPVOC I>/U< 51V1MRK 511 401-UEN A Section 8Current protectionBay control REC670 2.2 IEC 221Application manual
