16.1.2.4 Intertrip scheme M16866-71 v4In some power system applications, there is a need to trip the remote end breakerimmediately from local protections. This applies for instance when transformers orreactors are connected to the system without circuit-breakers or for remote trippingfollowing operation of breaker failure protection.In an intertrip scheme, the send signal is initiated by an underreaching zone or from anexternal protection (transformer or reactor protection). At the remote end, the receivedsignals initiate a trip without any further protection criteria. To limit the risk for anunwanted trip due to the spurious sending of signals, the timer tCoord should be set to10-30 ms dependant on the type of communication channel.The general requirement for teleprotection equipment operating in intertrippingapplications is that it should be very secure and very dependable, since both inadequatesecurity and dependability may cause unwanted operation. In some applications theequipment shall be able to receive while transmitting, and commands may betransmitted over longer time period than for other teleprotection systems.16.1.3 Setting guidelines IP15021-1 v1M13869-4 v4The parameters for the scheme communication logic function are set via the local HMIor PCM600.Configure the zones used for the CS send and for scheme communication tripping byusing the ACT configuration tool.The recommended settings of tCoord timer are based on maximal recommendedtransmission time for analogue channels according to IEC 60834-1. It is recommendedto coordinate the proposed settings with actual performance for the teleprotectionequipment to get optimized settings.16.1.3.1 Blocking scheme M13869-8 v5SetOperation EnabledSetSchemeType BlockingSettCoord 25 ms (10 ms + maximal transmission time)SettSendMin 0 sSetUnblockDisabled(Set toNoRestart if Unblocking scheme with no alarm for loss of guard is to beused.Set toRestart if Unblocking scheme with alarm for loss of guard is to be used)SettSecurity 0.035 sSection 16 1MRK 504 163-UUS AScheme communication818 Transformer protection RET670 2.2 ANSIApplication manual
