Pilot wire differential relays device 87l distance. 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. Single pole tripping using distance protection is a challenging application. 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. Transmission line protection principles ge grid solutions. With their flexibility and the highperformance digsi 5 engineering tool, siprotec 5 devices offer futureoriented system solutions with. Psl 6603u is always configured as a multifunction device. Pdf application of distance and line current differential relays in. How do we detect and isolate faults on transmission lines. Relion 670 series line differential protection red670 pre. Principles of differential relaying my protection guide.
Strictly speaking the rc tells us how much current a relay will use to restrain based on the currents. This technical article covers 4 fundamental protection principles overcurrent protection, directional overcurrent, distance and differential. The systems in which selectivity is relative are nonunit systems. Consider a simple radial system, which is fed from a single source. The principles of differential protection you must. In this example we will assume that the entry and exit currents are equal. However the distance schemes have underperformed in some instances. Line differential and distance protection terminal. 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. Line differential protection substation automation. Distance protection relay is the name given to the protection, whose action depends on the distance of the feeding point to the fault. A distance relay measures the impedance of a line using. Pdf line protection in breakerandahalf configurations requires main protection functions to respond to the sum of the two currents.
Line differential and distance protection siprotec 7sl82. They are generally applied on short lines, normally less than 40 km long. However, the increased availability of digital communications channels has renewed the interest in. Each transformer unit can be protected by a differential relay. This impedance between the relay and the fault depends on the electrical distance between them. 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. Pilot wire differential relays device 87l the pilot wire differential relay is a highspeed relay designed for protection of transmission and distribution lines. Fundamental overcurrent, distance and differential protection. Line differential and distance protection siprotec 5. Overcurrent protection, the simplest and most economical of these principles, is limited to radial lines. Current differential line protection setting considerations s. The time of operation of such protection is a function of the ratio of voltage and current, i.
In this type of protection the electrical quantities entering and leaving the protected zone or area are compared by current transformers c. Differential protection what goes in must come out. The output signal is 1 if the input signals are different and 0 if they are equal. Dependent of communication distance protection in red670. Line current differential relays can meet the requirements but require complex and expensive communications links. The l90 line differential relay and the l60 line phase comparison. Current differential line protection setting consideration. Principles and characteristics of distance protection. Principles of differential relaying the restraint characteristic suppose further that there is 0. Numerical relays are the result of the application of microprocessor technology in relay. 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 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. 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. With its flexibility and the powerful digsi 5 engineering tool, siprotec 7sl82 offers futureoriented system solutions with high investment. Pdf 1 abstract differential protection is able to provide the most selective protection compared. 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.
1169 1339 465 407 1274 1153 489 781 1204 341 1421 1443 775 782 814 1540 143 931 1549 1198 116 288 1384 354 889 521 1034 925 1048 1401 1087