Section 9 Secondary system supervision9.1 Current circuit supervision CCSRDIF (87)9.1.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberCurrent circuit supervision CCSRDIF - 879.1.2 ApplicationOpen or short circuited current transformer cores can cause unwanted operation of manyprotection functions such as differential, ground-fault current and negative-sequencecurrent functions. When currents from two independent three-phase sets of CTs, or CTcores, measuring the same primary currents are available, reliable current circuitsupervision can be arranged by comparing the currents from the two sets. If an error in anyCT circuit is detected, the protection functions concerned can be blocked and an alarmgiven.In case of large currents, unequal transient saturation of CT cores with differentremanence or different saturation factor may result in differences in the secondarycurrents from the two CT sets. Unwanted blocking of protection functions during thetransient stage must then be avoided.Current circuit supervision CCSRDIF (87) must be sensitive and have short operate timein order to prevent unwanted tripping from fast-acting, sensitive numerical protections incase of faulty CT secondary circuits.Open CT circuits creates extremely high voltages in the circuits which isextremely dangerous for the personell. It can also damage the insulationand cause new problems.The application shall, thus, be done with this in consideration, especiallyif the protection functions are blocked.1MRK 511 286-UUS A Section 9Secondary system supervision171Application manual
