Section 13 Scheme communication13.1 Scheme communication logic for distance orovercurrent protection ZCPSCH IP15749-1 v313.1.1 IdentificationM14854-1 v4Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberScheme communication logic fordistance or overcurrent protectionZCPSCH - 8513.1.2 Application IP15020-1 v1M16866-3 v5To achieve fast fault clearing for a fault on the part of the line not covered by theinstantaneous zone 1, the stepped distance protection function can be supportedwith logic that uses a communication channel.One communication channel in each direction, which can transmit an on/off signalis required. The performance and security of this function is directly related to thetransmission channel speed and security against false or lost signals.Communication speed, or minimum time delay, is always of utmost importancebecause the purpose for using communication is to improve the tripping speed ofthe scheme.To avoid false signals that could cause false tripping, it is necessary to payattention to the security of the communication channel. At the same time it isimportant to pay attention to the communication channel dependability to ensurethat proper signals are communicated during power system faults, the time duringwhich the protection schemes must perform their tasks flawlessly.The logic supports the following communications schemes:• blocking schemes (blocking and delta blocking)• permissive schemes (overreaching and underreaching)• unblocking scheme and direct intertripA permissive scheme is inherently faster and has better security against falsetripping than a blocking scheme. On the other hand, a permissive scheme depend1MRK 505 393-UEN B Section 13Scheme communicationLine differential protection RED650 2.2 IEC 277Application manual
