The differential protection relay is used for the protection of the generator, transformer, feeder, large motor, busbars etc. A sensitive current element in series with the highimpedance element is calibrated in volts based on the voltage drop across the internal impedance. Digital current differential relays power line carrier figure 1. Bus bar protection schemes,simple current differential scheme,need for bus bar protection,requirement of bus bar protection,recommendations for providing bus b slideshare uses cookies to improve functionality and performance, and to. Principles of differential relaying my protection guide. Protection elements the sel311l differential elements compare phase and sequence components from each line terminal, as illustrated in figure 2. Sel311l line current differential protection and automation. Applying digital line current differential relays over pilot wires 73 1. Scope this document introduces the application of the threephase differential protection in ref542plus. The faults occur in the transformer inside the insulating oil can be detected by buchholz relay. It improves and enhances the sensitivity of the operation of the digital differential relay that protects power transformers by discriminating between inrush current. Solution scheme for time synchronization of current.
The twj starting component is responsible for starting the reclosing function under unwanted tripping of the circuit breaker. Application example on transformer differential protection calculation 2533mva 6923kv deltawye transformer on sel387a relay figure 1. Sep 08, 2016 calculation for transformer differential protection given details. The protection for internal fault in such type of transformer is to be provided by using differential protection system. However, the differential current can sometimes be substantial even without an. Line current differential protection relay electrical. Current comparison relays with associated communication media current differential line protection current differential relaying is a method of extending the benefits of differential protection as applied to transformers, buses or generators to the protection of transmission lines. The red670 ieds feature phasesegregated current differential protection with excellent sensitivity for high resistive faults and secure phase selection for up to five line terminals.
This paper discusses a unique new approach to numerical current differential line protection that offers improved performance over the conventional percentage. Generally instantaneous attracted armature type relays are used for this purpose because all they have high speed operation and also they are free from being affected by any ac transient of the power circuit. Current differential protection with optional subcycle distance. When no fault is present in the protected equipment, the sum of current phasors i1 and i2 is null i. Basic transformer differential protection calculation. Therefore, differential protection of transformer should be provided with a proportional bias of an amount which exceeds in effect the maximum ratio deviation. In addition its effect on the reliability of substa. The relay was able to automatically compensate for the power transformer vector group connection and even to compensate for the current magnitude differences caused by onload tapchanger oltc operation. Because line charging current has a very low negativesequence component, negativesequence current differential protection allows for high sensitivity without compromising security. Scribd is the worlds largest social reading and publishing site. It is assumed with these schemes that a certain degree of ct saturation is possible under throughfault conditions. As you differential protection is based on the law of kirchhoff. Abstractline current differential protection creates challenges for relay design and application. Apply subcycle current differential protection with included fourzone distance and directional overcurrent backup.
This is especially true of line current differential applications applied to. The measurement algorithm is extremely reliable, offering fast detection of internal faults, and stability for external faults. Easy to integrate and with an extensive function library, the relion family of protection and control delivers advanced functionality and. The following are the classification of the differential protection relay. Line current differential protection free download as powerpoint presentation. An alternative principle for line protection that is quickly becoming the norm is differential protection. The technical manual for this device gives instructions for its installation, commissioning, and operation. Differential protection of transformer differential. Appropriate placement of fault current limiting reactors. Provides line current faults and differential protection to power lines. Modern line current differential protection solutions schweitzer. Line current differential protection principlesintroduces the reader to the 87l operation principles, design challenges, and solutions. It is based on the fact that it is only in the case of faults internal to the zone that the differential current difference between input and output currents will be high. Two or threewinding power transformers can be included in the protected zone.
Power system protection college of engineering and. We will start the transformer differential protection calculation with the identification of the transformer vector group. In electric current differential protection of busbar, if ct secondary circuits, or bus wires is open the relay may be operated to isolate the bus from live system. Compared with many other methods, it is more eco nomical. May 15, 2018 at maximum through fault current, the spill output produced by the small percentage unbalance may be substantial. Pdf modern line current differential protection solutions. Differential and common mode noise murata manufacturing. The differential protection used for power transformers is based on merzprize circulating current principle. The algorithm has a dual slope percentage bias restraint, as shown in figure 2. An internal fault will generate differential current. Red670 line differential protection substation automation.
Novel sensitive current differential protection of citeseerx. Therefore, the primaryside protective device will not receive a trip signal for events on the primary bus, and this device will not get called on to clear. Current differential protection with optional subcycle. Traditionally, current differential protection communication channels are either direct fiber optic cable or multiplexed. Built on the industryleading ur platform, the multilin l90 transmission protection relay provides highspeed current differential protection suitable for transmission lines and cables of various voltage levels, while supporting complete distance protection and dualbreaker applications suitable for single and threepole tripping applications. Busbar protection busbar differential protection scheme. Use single or dual differential channels for reliability. This is especially true of line current differential applications applied to breakerandahalf and ringbus configurations. The differential protection of transformer has many advantages over other schemes of protection. A differential relay is defined as the relay that operates when the phase difference of two or more identical electrical quantities exceeds a predetermined amount. Pdf a new method for differential protection in power transformer. A new approach to current differential protection for transmission.
From a design perspective, the distributed nature of the line current differential system imposes limits on the amount of data that can be exchanged between the system terminals and calls for data. Generally differential protection is provided in the electrical power transformer rated more than 5mva. Appropriate placement of fault current limiting reactors in. A fault outside the zone gives the same fault current at the entry and exit of the zone, but faults within the zone. Current transformers in a differential scheme must be chosen to have nearidentical response to high overcurrents. Differential protection of transformer differential relays. A differential scheme acts on the difference between current entering a protected zone which may be a bus bar, generator, transformer or other apparatus and the current leaving that zone. Pdf advanced line current differential protection with reduced.
From a design perspective, the distributed nature of the. Current differential protection is based o n kirchhoffs current law and the change of differential current can ef fectively reflect whether the busbar is faulty or not, it is a widely used protection. Jan 14, 2017 a differential relay is defined as the relay that operates when the phase difference of two or more identical electrical quantities exceeds a predetermined amount. Designed to seamlessly consolidate functions, relion relays are smarter, more flexible and more adaptable. Differential protection is a unittype protection for a specified zone or piece of equipment. Use the sel311l line current differential relay with integral fourzone distance backup for easytoapply, highspeed line protection.
Current differential line protection setting consideration. Even in cases of fail tripping, the mdr2 offers an adjustable tripping characteristic function that compensates for unbalanced current measurements, avoiding fail. Transformer vector group and ct to relay connection. Theimprove ment in sensitivity is a result of adaptive control of the restraining region in a current differential. Easy to integrate and with an extensive function library, the relion family of protection and control delivers advanced functionality and improved performance. System protection is the art and science of detecting. Modern line current differential protection solutions sel. It is important to remember that the current transformers for the transformer differential protection are typically located on the bushings of the transformer. Abstract digital current differential protection has the advantages of application simplicity, operation speed, and high sensitivity. The aim is to provide reference for engineering application of data synchronization of current differential protection between digital substations in future. The differential relay works on the principle of comparison between the phase angle. This course explains protection relay selection process by detailing how to protect against each fault type or abnormal condition. Line differential protection psl 6603u product guide.
Connection diagram connection diagram due to its flexibility, the ref542plus offers a lot of options for connecting the device to the current transformers. Applying digital line current differential relays over. The mdr2 is a stateoftheart combined differential protection and shortcircuit protection relay for generator protection against internal short circuits leaking currents. Applying digital line current differential relays over pilot. Differential protection schemes are mainly used for protection against phasetophase fault and phase to earth faults. Line differential protection substation automation. The differential protection is designed to protect power transformers or highvoltage motors. The differential protection is provided in the generator by using longitudinal differential relay. Use cables and connections that give low impedance. Communications and time sourcesdiscusses communications.
Abstractparalleling current transformers cts is a common practice in differential or line protection applications where the number of cts exceeds the number of relay current inputs. Differential protection for arbitrary 3ph power transformer. Explain challenges of transformer differential protection understand need for tap, phase, and zerosequence compensation and how they work understand how transformer differential relays are made secure for inrush and overexcitation transformer differential protection presentation objectives. Protective relays, associated communication systems, voltage and current. Differential protection of generator or alternator. The papers are grouped in sections that cover the following topics. Paralleling cts for line current differential applications.
Principles of differential relaying current balance high impedance also known as unbiased differential protection only one actuating relay quantity current required for operation. Abb library is a web tool for searching for documents related to abb products and services. Noise suppression by common mode choke coils d effect on differential mode current since magnetic flux caused by differential mode current cancels out, impedance is not produced. In this section, the previouslyintroduced short circuit reduction methods are briefly described. Line current differential protection creates challenges for relay design and application. Differential protection is based on kirchhoffs laws, stating that all current into a network node shall add up to 0 in an ideal system. Differential protection can be used to provide protection for zones with multiple terminals and can be used to protect lines, generators, motors, transformers, and other electrical plant. As a unit protection with its zone constrained by location of current transformers cts, the differential protection principle is considered superior with respect to selectivity, sensitivity, and.
Modern line current differential protection solutions. The highimpedance input is created by an internal impedance, typically resistive, of 2000 ohms or higher. Protection functions bias differential protection 87 harmonic restraint protection over fluxing i. Protection relays differential relays b high impedance differential protection. Communications and time sourcesdiscusses communications and timing for 87l protection. A typical dc circuit for busbar differential protection scheme is given below. Differential protection, frame leakage protection the systems in which selectivity is relative are nonunit systems. Apr 19, 2016 bus bar protection schemes,simple current differential scheme,need for bus bar protection,requirement of bus bar protection,recommendations for providing bus b slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The operating characteristic of the percentage restraint current differential relay with a slope of. A high current injection test unit capable of injecting a. Differential protection is applicable to all parts of the power system.
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