Distance protection, in its basic form, is a nonunit system of protection offering considerable economic and technical advantages. The combined siprotec 7sl828687 line differential and distance protection have been designed particularly for the costoptimized and compact protection of lines in mediumvoltage and high voltage systems. With its flexibility and the powerful digsi 5 engineering tool, siprotec 7sl82 offers futureoriented system solutions with high investment. Numerical relays are the result of the application of microprocessor technology in relay. Unlike phase and neutral overcurrent protection, the key advantage of distance protection is that its fault coverage of the protected circuit is virtually independent of source impedance variations. Current differential line protection setting consideration. However, the increased availability of digital communications channels has renewed the interest in. Principles and characteristics of distance protection. The time of operation of such protection is a function of the ratio of voltage and current, i. Relion 670 series line differential protection red670 pre. Overcurrent protection, the simplest and most economical of these principles, is limited to radial lines. Pdf 1 abstract differential protection is able to provide the most selective protection compared. Line current differential relays can meet the requirements but require complex and expensive communications links. In this example we will assume that the entry and exit currents are equal.
Psl 6603u is always configured as a multifunction device. Current differential line protection setting considerations s. How do we detect and isolate faults on transmission lines. Each transformer unit can be protected by a differential relay. They are generally applied on short lines, normally less than 40 km long. Mohammed tawfeeq alzuhairi 321 differential protection differential protection is the best technique in protection. Line differential and distance protection siprotec 5. The distance protection then provide protection for the entire line including the remote end back up capability either in case of a communications failure or via use of an independent communication channel to provide a fully redundant scheme of protection that is a. Fundamental overcurrent, distance and differential. Principles of differential relaying the restraint characteristic what needs to be realised is that the first one is properly termed the restraint characteristic rc whilst the latter is an operating characteristic. For balanced protection system and distance protection special class current. Consider a simple radial system, which is fed from a single source. Pdf line protection in breakerandahalf configurations requires main protection functions to respond to the sum of the two currents. Line differential protection substation automation.
Erwin rfl electronics inc 353 powerville road boonton twp, nj 07005 abstract the most common pilot line protection today is directional comparison by use of distance relays. This impedance between the relay and the fault depends on the electrical distance between them. The systems in which selectivity is relative are nonunit systems. Dependent of communication distance protection in red670. Pdf application of distance and line current differential relays in. Pdf the implementation of distance protection relay in. The output signal is 1 if the input signals are different and 0 if they are equal. Single pole tripping using distance protection is a challenging application. Figure 1 shows a simple differential protection scheme, also known as a merzprice scheme in this simple scheme, we can assume that under normal operating conditions, the current entering into the piece of equipment under protection is equal or in the case of a transformer, proportional to its exiting current. With their flexibility and the highperformance digsi 5 engineering tool, siprotec 5 devices offer futureoriented system solutions with. A distance relay measures the impedance of a line using. This technical article covers 4 fundamental protection principles overcurrent protection, directional overcurrent, distance and differential. Principles of differential relaying the restraint characteristic suppose further that there is 0. Let us measure the apparent impedance vi at the sending end for the unloaded system, i 0, and the apparent impedance seen by the relay is infinite.
However the distance schemes have underperformed in some instances. Distance protection relay is the name given to the protection, whose action depends on the distance of the feeding point to the fault. Strictly speaking the rc tells us how much current a relay will use to restrain based on the currents. Differential protection what goes in must come out. Selective backup protection if the communication is unavailable the distance protection will also serve as protection main protection or backup protection for the adjacent busbar. Pilot wire differential relays device 87l the pilot wire differential relay is a highspeed relay designed for protection of transmission and distribution lines. Transmission line protection principles ge grid solutions. Line differential and distance protection siprotec 7sl82. Fundamental overcurrent, distance and differential protection. The l90 line differential relay and the l60 line phase comparison. Line differential and distance protection terminal. Pilot wire differential relays device 87l distance. The combined siprotec 7sl82 line differential and distance protection has been designed particularly for the costoptimized and compact protection of lines in mediumvoltage and highvoltage systems.
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