9.1.3 Setting guidelinesGlobalBaseSel: Selects the global base value group used by the function to define (IBase),(VBase) and (SBase).Current circuit supervision CCSRDIF (87) compares the residual current from a three-phase set of current transformer cores with the neutral point current on a separate inputtaken from another set of cores on the same current transformer.The minimum operate current, IMinOp, must be set as a minimum to twice the residualcurrent in the supervised CT circuits under normal service conditions and rated primarycurrent.The parameter Pickup_Block is normally set at 150% to block the function duringtransient conditions.The FAIL output is connected in the PCM configuration to the blocking input of theprotection function to be blocked at faulty CT secondary circuits.9.2 Fuse failure supervision SDDRFUF9.2.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberFuse failure supervision SDDRFUF - -9.2.2 ApplicationDifferent protection functions within the protection IED, operates on the basis of themeasured voltage in the relay point. Examples are:• impedance protection functions• undervoltage function• energizing check function and voltage check for the weak infeed logicThese functions can operate unintentionally if a fault occurs in the secondary circuitsbetween the voltage instrument transformers and the IED.It is possible to use different measures to prevent such unwanted operations. Miniaturecircuit breakers in the voltage measuring circuits, located as close as possible to thevoltage instrument transformers, are one of them. Separate fuse-failure monitoring IEDsor elements within the protection and monitoring devices are another possibilities. TheseSection 9 1MRK 511 286-UUS ASecondary system supervision172Application manual
