Psl 6603u is always configured as a multifunction device. In this example we will assume that the entry and exit currents are equal. Pdf the implementation of distance protection relay in. In this type of protection the electrical quantities entering and leaving the protected zone or area are compared by current transformers c. However, the increased availability of digital communications channels has renewed the interest in. Line differential and distance protection siprotec 5. 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. The l90 line differential relay and the l60 line phase comparison. 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. Line differential protection substation automation.
Distance protection, in its basic form, is a nonunit system of protection offering considerable economic and technical advantages. Overcurrent protection, the simplest and most economical of these principles, is limited to radial lines. Pilot wire differential relays device 87l the pilot wire differential relay is a highspeed relay designed for protection of transmission and distribution lines. Principles of differential relaying my protection guide. The systems in which selectivity is relative are nonunit systems. Pilot wire differential relays device 87l distance. Line current differential relays can meet the requirements but require complex and expensive communications links. 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. Fundamental overcurrent, distance and differential protection. Numerical relays are the result of the application of microprocessor technology in relay. Transmission line protection principles ge grid solutions. Single pole tripping using distance protection is a challenging application. With its flexibility and the powerful digsi 5 engineering tool, siprotec 7sl82 offers futureoriented system solutions with high investment.
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. For balanced protection system and distance protection special class current. Current differential line protection setting consideration. The output signal is 1 if the input signals are different and 0 if they are equal. 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. How do we detect and isolate faults on transmission lines. Pdf line protection in breakerandahalf configurations requires main protection functions to respond to the sum of the two currents. Relion 670 series line differential protection red670 pre. Differential protection what goes in must come out. Pdf 1 abstract differential protection is able to provide the most selective protection compared.
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. 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. Line differential and distance protection siprotec 7sl82. Line differential and distance protection terminal. Principles and characteristics of distance protection. This impedance between the relay and the fault depends on the electrical distance between them. With their flexibility and the highperformance digsi 5 engineering tool, siprotec 5 devices offer futureoriented system solutions with.
Current differential line protection setting considerations s. Consider a simple radial system, which is fed from a single source. Mohammed tawfeeq alzuhairi 321 differential protection differential protection is the best technique in protection. Pdf application of distance and line current differential relays in. 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. They are generally applied on short lines, normally less than 40 km long. Distance protection relay is the name given to the protection, whose action depends on the distance of the feeding point to the fault. Each transformer unit can be protected by a differential relay.
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