It works on the principle of comparison between the phase angle and the magnitude of the same electrical quantities. Pdf easy method for testing transformer differential relays. Design and implementation of transformer static differential relay with harmonic blocking for transformer protection. High impedance busbar differential protection will not work properly if the cts are not sized correctly for the connected circuit. For generator differential protection, one set of current transformers ct are located on generator neutral side, whereas second set of ct is located on generator phase side. Design and implementation of transformer static differential relay. In such type of relays, the output is obtained by the static components like magnetic and electronic circuit etc. The difference amongst the currents may also be in phase angle or in magnitude or in each. In terms of operation, ssrs are not very different fr om mechanical relays that have moving contacts. A new chapter on microprocessor applications to protection has been added. Des cr1 pti on each type std relay is a singlephase unit. In addition to the differential function, a backup overcurrent protection for 1 windingstar point is integrated in the relay. In the event of such faults, the quick response of the differential element may limit the damage that may have otherwise occurred to the motor. The differential relay of the type explained above is likely to operate inaccurately with heavy through i.
The military specifications and standards are listed in table 1, and other information can be found in milstd46. Ge multilin electromechanical products catalog ge grid solutions. Fundamentals and improvements for directional relays. Phase comparison relays are line differential relays mainly intended for used with power line carrier. The relay which does not contain any moving parts is known as the static relay. Operate and restraint signals of a transformer differential relay page 4 of 24 emulating the delta connection of the cts for all the wyeconnected windings of a protected transformer, or by calculating and subtracting the zero sequence cu rrent explicitly. Pdtpr family of protective relays are advance numrical relays that. Sometimes called slope or slop this characteristic can be used to solve the problems of mismatched cts, ct saturation, and magnetizing inrush. Jul 26, 2017 differential protection relay 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. The sel487b relay provides bus current differential protectio n, circuit breaker failure protection, and backup overcurrent protection. Differential relaying provides selectivity by providing a zone of protection with a circuit of interconnected cts. This isolates the reed switch, protecting if from high current or voltages. Sel5870, 1 connectorized current differential relay.
Level detection is accomplished by using a highresolution thermal differential. This relay testing book is our core handbook and is used by large organizations across north america in their training programs. 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. The relay whose operation depends on the phase difference of two or more electrical quantities is known as the differential protection relay. The particular application can be chosen by setting. Selwa05010w wiring harness for sel501 and sel587 connectorized relays, features new shorting connector. The operation of removing the zero sequence component is necessary also for a delta. Type dth 31, 32 dttm 11, 12 high speed biased differential relays dth relay withdrawn from case features lhigh speed. One main difference between the pilot wire relay and the digital current differential relay is the communication medium used. Abb residual current breaker with overload protection rcbo. It thus provides a means for maintaining a practically constant.
I want to know how a high impedance differential scheme works we received this question from the ask chris form at. Current differential line protection setting consideration. In solid state relays, the inductor is replaced by a semiconductor element. The bonneville power administration bpa like other utilities, is converting many of its substations for supervisory control. Highimpedance differential relay protection use highimpedance differential elements for fast tripping for inzone faults, while providing security during heavy through faults and ct saturation. Optionally, a low or highimpedance restricted earthfault protection, a negativesequence protection and a breaker failure protection can be used.
Fundamentals of relay technology application note 1 fundamentals of relay technology electromechanical relays are us ed as interface modules between the process io devices, on the one hand, and the openloopclosedloop control and signaling equipment, on the other, for level and power adjustment purposes. A differential relay over current relay responds to the vector difference between two or more similar electrical quantities. High impedance busbar differential protection minimum allowable ct saturation voltage calculation. Differential relays and its types devices electrical. Protection and switchgear miet engineering college.
High impedance busbar differential protection valence. The block diagram for such a relay is shown in fig. The relays used in power system protection are of different types. New developments in commercial relay manufacture are also included. A static voltage differential relay for protection of shunt capacitors. Dictionary says that relay means the act of passing something from one thing to another, the same meaning can be applied to this device because the signal received from one side of the device controls the. The differential protection of power transformer is a unit protection scheme. It is used to protect the electrical equipment against internal fault such as internal winding short circuit or bus bar phase to phase short circuit, inter turn short, winding puncture etc. Csepro family of protective relays are advance numerical relays that provide multi protection and monitoring with reliable and fast protection solutions in a single unit.
A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. True bus differential relaying compares all currents entering and leaving a switchgear bus. Testing numerical transformer differential relays commissioning. Type ca percentage differential relay for transformer. The differential protection relay is used for the protection of the generator, transformer, feeder, large motor, busbars etc. A variant of the numerical differential protective relay with safety jacks and connectors mounted on the front panel to provide access to all relay inputs, outputs, and ports is also available. The differential relay measures the phasor difference between two similar electrical quantities voltagevoltage or currentcurrent. This paper carries the idea of selection of dual slope differential relay parameters for various faulty conditions on the system. This is because the induction disc characteristics of the overcurrent relays inverse characteristics are not amenable to simple mathematical analysis. The relay has 21 analog current inputs and three analog voltage inputs. Power transformers on the contrary of generators are static.
It is very effective for earth faults and faults between phases. In order to overcome this difficulty, differential relay are used. Pdf differential protection schemes and techniques for power. The mib202 is microcontroller based numerical biased differential protection relay with inbuild current amplitude and vector group compensation features and also with instantaneous differential highset element for two winding power transformer and autotransformers. The differential relay is one that operates when there is a difference between two or more similar electrical quantities exceeds a predetermined value. Follow this link to ask your own question and it might appear in a future blog post. May 1996 1 application the 7ut5127ut5 differential protection relays are used for fast and selective isolation of shortcircuits in transformers of all voltage levels and also in rotating electric machines and short lines.
I want to know how a high impedance differential scheme works. Reduce panel design cost and space requirements by using a single relay that includes threephase protection, resistors, and metal oxide varistors movs. Ssrs, however, employ semiconductor switching elements, such as thyristors, triacs, diodes, and transistors. The type pvd21 relay is a singlephase, highspeed, highimpedance, voltageoperated relay designed to provide protection in bus differential schemes. But the effect of even a rare fault may be very serious for a power transformer. Del a opencore toroid for differential relay ordering code inside diameter stock tdaa2 110mm tdab2 150mm tdac2 300mm del closedcore toroid for differential relay ordering code inside diameter stock tdga2 28mm tdgb2 35mm tdgh2 60mm tdgc2 80mm tdgd2 110mm tdge2 140mm tdgf2 210mm. We use a reed switch to actuate the relay at a prescribed value. Relay security is achieved by an optimized set of userselect. The percentage difference at which a differential relay is set to operate is dependent upon the ratio between the number of turns on the operating and restraint windings.
Differential protecting of transformers and generators from localised faults duration. This drawback is overcome by using percentagedifferential relay or biaseddifferential relay. Differential protection may be considered the first line of protection for internal phase to phase or phase to ground faults. Three phase differential protection relay for power. Siemens series 62 constant differential relays for air.
Revised edition released october 2010 previously presented at the 37th annual western protective relay conference, october 2010 originally presented at the 63rd annual conference for protective relay engineers, march. Sel587 current differential relay electrical part manual s. The first static relays developed were the high speed differential relays and the distance relays. Differential is generally applied for both pilot wire relays and digital current differential relays. Some differential pressure switch models allow for two relays on one instrument. 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.
Figure 1 typical application of currentdifferential relays for deltawye transformer protection. Among them differential relay is very commonly used relay for protecting transformers and generators from localised faults. The relay may lose its stability for through faults. Basic differential relay working function electrical4u. Sel587 current differential relay economical differential protection for power apparatus major features and benefits the sel587 current differential relay combines overcurrent and differential elements in an easytoapply power apparatus differential protection package. Micom p63x required data ratings of the power and current transformers mva voltage ratio rated voltage in kv hv side rated voltage in kv lv side vector group ct ratio hv side ct hv side vector group ct ratio lv side ct lv side vector group. May 15, 2018 differential relays can detect such type of faults.
When the relay is correctly set, one screw must be in the. Strictly speaking the rc tells us how much current a relay will use to restrain based on the currents. Click the new button and type in differential under the function name. Static relays phase, amplitude comparators synthesis of various relays using static. Such relays are less sensitive because they cannot make correct distinction between heavy load conditions and minor fault conditions. Type dth 31, 32 dttm 11, 12 high speed biased differential relays. In the differential relay scheme circuit, there are two currents come from two parts of an electrical power circuit. Latching relays are the same as the singleside stable relays described previously except that the core, yoke, and armature are made from semihard magnetic material and there are at least two coils in the relay. One of the most important protection in power system is differential protection. Apply the sel387e current differential and voltage relay to provide comprehensive protection, metering, and automation of transformers, reactors, and other power apparatus. This relay will be used as the reference for one of the cts while the pddctsec feeder breaker will be used as the other reference ct.
Pdf numerical differential protection algorithm for power. The definition of such a relay is one that operates when the vector difference of two or more similar electrical quantities exceeds a predetermined amount. It is a static device, totally enclosed and usually oil immersed, and therefore the fault occurs on them are usually rare. Differential protection of transformer differential relays. Differential relay it is a relay that checks for current balance between the primary and the secondary side of a transformer. This current would be detected by the motor relay as a ground fault.
Fundamentals and improvements for directional relays karl zimmerman and david costello schweitzer engineering laboratories, inc. Many customers select a differential pressure unit with a switch or a transmitter, which allows for remote readout and alerts. The book is a thoroughly revised and updated second edition of a successful text. I dont understand the working principle of the differential relay. A relay, in its most basic form, is a combination of a switch and an inductive element. Thus the simple differential relay is stable during normal operating condition. Within the limits of the accuracy of the cts and the relays, true bus differential relaying will detect all. Amy sinclair, elecsar engineering abstractthe greatest challenge of bus differential protection is dealing with false differential current due to. For buses with no more than seven terminals, use one sel487b in a single relay application.
Sel587 current differential relay schweitzer engineering. Differential relays take a variety of forms, depending on the equipment they protect. The relay which is used to checks the difference between the output and input currents for power system current in known as differential relay. Differential relays are very sensitive to the faults occurred within the zone of protection but they are least sensitive to the faults.
Differential relay current differential relay biased. Differential protective relay is a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents. Percentage differential relays type ijd 2 cover target reset button inner block top latch oradli oonniotino plug bottom latch fig. Oct 24, 2017 three phase differential protection relay for power transformer checked for a fault condition. Testing and maintenance of protective gear, protection against surgesurge absorber, surgediverter. Most of the relays discussed so far relied on excess of current for their operation. Differential pressure switches and relays orange research. Current differential and voltage relay protection expand transformer protection capabilities with restricted earth fault ref, negativesequence overcurrent, overexcitation, and frequency elements. Partial differential relaying powell industries, inc. Differential protection of a transformer the transformer is one of the major equipment in power system. The differential relay works on the principle of comparison between the phase angle. Cts having the same ratio are installed in all the connections to the.
Model series 62 constant differential relay introduction the constant differential relay maintains a constant pressure drop across an internal needle valve for any flow setting up to about 2. The differential relays normally response to those faults which occur in side the differential protection zone of. Differential protection of yy and connected power transformer mayurdhvajsinh p. The rectifier bridge amplitude comparator is the most common static form for applications as a differential relay element. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected 4 the first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as overcurrent, overvoltage, reverse power flow, overfrequency, and underfrequency.
Universal relay general electric t60 differential relay 87 module tdms software this applica on note will guide you step by step to perform tests on di. The following are the classification of the differential protection relay. The over current relay is wired to trip the two circuit breakers on either side of the equipment to be protected. For high speed differential protection of busses and feeders and shunt reactors. Type ca percentage differential relay for transformer protection 50 and 60 hertz instruction leaflet. Differential relays high impedance differential relay highimpedance differential relays are typically used for bus protection. A solid state relay ssr is a re lay that does not have a moving contact.
Such a system is called a merzprize circulating current system. Select the xfm relay device in the captor tcc drawing figure 4 and click the function button to display the protection functions. It incorporates the latest developments in semiconductor technology and its applications to power system protection. Moreover buchholz relay is provided in transformer for detecting any internal fault in the transformer but differential protection scheme detects the same in more faster way. Pdf optimizing differential protection settings for power. Principle and operation of differential relay what is differential relays. The following lists the major categories available. Principle and operation of differential relay my tech info. The type pvd21 utilizes the same operating principle high impedance voltage as the earlier pvd models, but provides faster operating speeds and higher seismic capabilities.
Set the power transformer vector group, the nominal primary and secondary voltage and the rated power. Applications and characteristics of differential relays. The implementation of current differential protection shown so far applies when either an electromechanical relay or a static protective relay is used. Differential relays can detect such type of faults. Series 62 constantdifferential relays ordering data model number constantdifferential relay purge rate 0. 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. The relay then closes its contacts and makes the circuit breaker to trip and thus isolated the protection from the system. Differential relays free download as powerpoint presentation. The numerical differential protective relay is powered via an ac power inlet mounted on the front of the relay enclosure.
Easy method for testing transformer differential relays. Sel387e current differential and voltage relay protection expand transformer protection capabilities with restricted earth. 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. It is also an application that demands the relay be able to operate with unequal ct. Skm software help desk using the differential function. Operating state set when current flows through coil a, the electromagnet made of. Pdf on dec 1, 2016, nikolina arapoglou and others published differential protection schemes and techniques for power transformers. Mib202 relay, which can be used to operate for internal faults, like. The overcurrent relays, even though simplest of all types of electromechanical relays, are the most difficult static relays. The differential relay works on the principle of comparison between the phase angle and magnitude of two or more similar electrical quantities. The relay which consists static and electromagnetic relay is also called static relay because the static units obtain the response and the. A relay is classified into many types, a standard and generally used relay is made up of electromagnets which in general used as a switch. For many solidstate electronic and microprocessorbased relays, the phase shift is made internally in the relay and the cts may be connected the same on the primary and secondary sides of the transformer regardless of the transformer winding connections. We calculated that the voltage across the nonsaturated ct, when another ct saturates, is 83.