internal functions of the IED itself in order to receive a block command from internalfunctions. Through OR gate it can be connected to both binary inputs and internalfunction outputs.The input BLKTRIP is intended to be connected to the trip output from any of theprotection functions included in the IED. When activated for more than 20 ms, theoperation of the fuse failure is blocked; a fixed drop-out timer prolongs the block for100 ms. The aim is to increase the security against unwanted operations during theopening of the breaker, which might cause unbalance conditions for which the fusefailure might operate.The output signal BLKZ will also be blocked if the internal dead line detection isactivated. The dead line detection signal has a 200 ms drop-out time delay.The input signal MCBOP is supposed to be connected via a terminal binary input to theN.C. auxiliary contact of the miniature circuit breaker protecting the VT secondarycircuit. The MCBOP signal sets the output signals BLKV and BLKZ in order to blockall the voltage related functions when the MCB is open independent of the setting ofOpModeSel selector. The additional drop-out timer of 150 ms prolongs the presence ofMCBOP signal to prevent the unwanted operation of voltage dependent function due tonon simultaneous closing of the main contacts of the miniature circuit breaker.The input signal 89b is supposed to be connected via a terminal binary input to theN.C. auxiliary contact of the line disconnector. The 89b signal sets the output signalBLKV in order to block the voltage related functions when the line disconnector isopen. The impedance protection function is not affected by the position of the linedisconnector since there will be no line currents that can cause malfunction of thedistance protection. If 89b=0 it signifies that the line is connected to the system andwhen the 89b=1 it signifies that the line is disconnected from the system and the blocksignal BLKV is generated.The output BLKV can be used for blocking the voltage related measuring functions(undervoltage protection, energizing check and so on) except for the impedanceprotection.The function output BLKZ shall be used for blocking the impedance protectionfunction.13.2.7.2 Delta current and delta voltage detection M13685-3 v7A simplified diagram for the functionality is found in figure 131. The calculation of thechanges of currents and voltages is based on a sample analysis algorithm. Thecalculated delta quantities are compared with their respective set values DIPU andDVPU. The algorithm detects a fuse failure if a sufficient change in voltage without asufficient change in current is detected in each phase separately. The followingquantities are calculated in all three phases:Section 13 1MRK 511 408-UUS ASecondary system supervision372 Phasor measurement unit RES670 2.2 ANSITechnical manual
