The idea of computerized insurance utilizing PCs which demonstrates much guarantee in giving enhanced execution has developed amid the previous two decades. With large essential motors, it is either impractical or not economical to provide an uninterruptible power source. This relay has to be installed straight only and away from magnetic field. With the advancement of temperate, groundbreaking and refined chip, there is a developing enthusiasm for creating microchip based defensive transfers which are more adaptable as a result of being programmable and are better than ordinary transfers. Comparison of Static Relays with Electro-Magnetic Relays and microprocessor based relays Particular Electro-Magnetic Relay Static Relay Numerical Relay or microprocessor based Relay Technology Standard 1st generation relays. SEL, AREVA, and ABB Group's were early forerunners making some of the early market advances in the arena, but the arena has become crowded today with many manufacturers. power system. The microprocessor based relays have minimum burden on the instrument transformers. These relays convert voltage and currents to digital form and process the resulting measurements using a microprocessor. The microprocessor based relay furnishes easy interface with digital communication equipment. Microprocessor Based Static ELR1-8A Business Directory » Relays & Contactors » Earth Leakage Relay Earth Leakage Current give rise to generation of heat and result in progressive failure of Mech. Microprocessor relays are computer-based systems that utilize software-based protection algorithms for the detection of electrical faults. 10. Required fields are marked *. Current is taken from C.T. show the design of the microprocessor-based protection has good performance. Operating Principle: They use principle of electromagnetic principle. Microprocessor based relays started to replace static relays in the beginning of the 1980s. A defensive framework incorporates circuit breakers, transducers (CTs and VTs), and defensive transfers to separate the flawed area of the power framework from the sound segments. With the help of logic circuits and the microprocessor, the integrated protection and control system can perform several functions of data acquisition, data processing, data transmission, protection and control. The book is a thoroughly revised and updated second edition of a successful text. All functions for the measurements and relay co-ordination can be calculated with a generalized COordinate Rotation DIgital Computer (CORDIC) algorithm instead of by approximation and extrapolation. Functions: 1 relay can perform various functions. A protective system includes circuit breakers, transducers (CTs and VTs), and protective relays to isolate the faulty section of the power system from the healthy sections. The block diagram of a static overcurrent time relay is shown in Fig. From a design standpoint, engineers are tasked with designing for manufacturability and longevity. Higher reliability of static microprocessor-based relays in comparison with electromagnetic relays containing elements moving mechanically. The target of this paper is to give a similar audit of microchip based defensive transfers. The output of rectifier is given to Multiplexer. and given to I to V converter because many electronics circuit require voltage signal for operation. They served us well. In an over current relay or o/c relay the actuating quantity is only current.There is only one current operated element in the relay, no voltage coil etc. Modern relay protection and automation devices are built on a microprocessor-based elemental base (we denote them as MP device). Select relay settings of over current and distance relays. A microprocessor-based digital protection relay can replace the functions of many discrete electromechanical instruments. The first fully numerical relay was introduced 1986. One of the salient feature of the developed protection scheme is that it does not require communications or adaptive protective devices. Microprocessor Based Static Relays 19. In static relays it is advantageous to choose a circuit accommodating a wide range of alternative inverse time characteristics, precise minimum operating levels, definite minimum times and additional high set features, if necessary. Improvements in protection and control via communications methods used to exchange digital bits (DBs) among devices are common in progressive utilities in high-voltage sub-stations. pp 1-11. Until now, new equipment purchases for new projects in industrial facilities using microprocessor (μP) multi-function protective relaying technology were typically done as a direct replacement of older technologies or as an updated equivalent. He recommended several techniques fo, digital microprocessor based protective relays, installed in, Although these relays comply with the latest, based relay protection at the power transmission line and. Bunty choudhary September 26, 2018 at 1:07 pm Reply. microprocessor-based protective relays designed to provide protective relay functions, metering, and control associated with switchgear circuit breaker installations. The relay hardware consists of standard modules resulting in ease of service. The resulting protective relay has higher processing capability making it more able to handle parallel multi-channel sources than existing digital/numerical relays are. was static or electronic relays, which were introduced in the 1960s. Fibre optical communication with substation LAN. All of the relaying functions are performed on these numeric values. Earlier, for each function, a separate electro mechanical or static unit was used with complex wiring. This D.C. voltage is proportional to load current only. Static relays may be based on analog solid state circuits, digital logic circuits, or microprocessor-based designs. Some authors use the term "static relay" to refer only to solid state relays. New developments in commercial relay manufacture are also included. Electrical Power System protection is required for, protection devices installed. 1 relay can perform only 1 function. and operate on rectified currents and voltages. The most definitive characteristic is the use of rectified quantities. Your email address will not be published. New developments in commercial relay manufacture are also included. Such protection is given by means of Under Voltage relays. Industry Applications, 46,(4), pp 1281-1294. A big difference between conventional electromechanical and static relays is how the relays are wired. If incoming value is more – fault is occurring and trip signal is send to CB circuit breaker. Further, the structure of a new relay enabling the proposed protection strategy is presented. Microprocessor – Based Static Relay (Digital) – Simple Block Diagram With the help of logic circuits and the microprocessor, the integrated protection and control system can perform several functions of data acquisition, data processing, data transmission, protection and control . Single-phase, single-function electromechanical devices may not provide all the features, but are considered by some to provide more security and dependability. At first it was ”hybrid” solutions, where the time critical filtering was performed with analogue electronics. Brand : Prok dv's; Contact Rating : 8 Amps/ 250V AC/ 8 Amps,30 V DC; Input Auxiliary Voltage : 110V,230V,415V,550V AC 50Hz 48V,& 220V VDC; Mounting Type : Flush / Din; Tripping Time : Variable 0.15 - 3 sec,Fixed 100 millisec,500 millisec,1 sec & 3 sec; more... View Mobile Send Inquiry. Greater sensitivity and high pickup ratio. For integrated protection and monitoring systems programmable microprocessor controlled static relays are preferred. Typical examples are REZ 1- Universal phase and ground distance relay for permissive and blocking schemes, 1-4 directional zones The microprocessor-based relays are used to operate from symmetrical component quantities to demonstrate that any set of unbalanced three-phase quantities could be expressed as the sum of three symmetrical sets of balanced phasors. Both types of relay control electrical circuits through a switch that is open or closed depending upon an electrical input. The digital, Microprocessor based relays are easy to apply, operate, M. Amin Zamani, Tarlochan S. Sidhu, Amirnaser Yazdani, (2011), Rao S.S. ,(2007). Fast but fragile is a fitting label for the static relay generation. Save my name, email, and website in this browser for the next time I comment. The electromechanical relays suffer from several drawbacks such as high burden on instrument transformer, high operating time, contact problem etc. Electromechanical and static relays have fixed wiring and the setting is manual. … When converting from analog to digital is over (finish) then A/D converter sends E/C signal to HP (E/C – End of Conversion). To understand the phenomenon of Over Voltages and it’s classification. To discuss the disadvantages of electromechanical and static type relays. (1 relay can be used as over current only for under voltage we use another relay). Therefore, the next option to reduce the effects of transient interrupted service is to automatically sense the disturbance and initiate a sequenced restart of the essential motors on the basis of process requirements, motor acceleration characteristics, and power system capabilities. They have been discarded at the end of the static relay generation because they would not fit in early microprocessor-based relays. Prok dv's make PNA Type Idmt/Definite Time/Instantaneous Low-Set/High-Set Nondirectiona Numerical/Microprocessor Based Over Current Relay (Ocr) With Earth Fault Relay (EFR) or independent over current Relay (OCR) or earth fault relay (EFR). discussed the issues that can exist when applying multifunction microprocessor-. They can come in single-phase or multi-phase units. a. microprocessor based relays b. Reliability has two aspects: dependabilit, These relays were classified as amplitude, relaying a viable and better alternative to the tradit, drastically. It would also be useful as a reference text for students of electrical engineering. Prok dv’s brand earth leakage relay MPEL series uses the state of the art microcontroller based protection device to detect low level leakage due to degradation of insulation of phase conductors or high impedance faults. Switchgear and Protection.13. Microprocessor Based Over Current Relay Current is taken from C.T. In this relays transistors and IC’s been used: They use microprocessor. The digital relay can emulate functions of many discrete electromechanical relays in one device, Static relays would have matured with investment fueled by their advantages, but emergence of the microprocessor-based relay with an explosion of functionality arrested the static relay generation. Numerical relays are based on the use of microprocessors. A proposed scheme of overcurrent relays dealing with programming of the single-board microcomputer TK-85, built by NEC around Intel's 8-bit 8085 microprocessor, is described. The substantial current related with short circuits is probably going to make harm the hardware if reasonable defensive transfers and circuit breakers are not accommodated the assurance of each segment of the. These following types of relays are classified based on their different operation principles. magnitude and the mode of operation. Advanced PC can undoubtedly fulfill the security necessities of present day control framework without troubles. 4. The output of rectifier is given to Multiplexer. 7. Micro controller based over voltage static Relay. Assistant Professor (EEE Dept. This device used DSP made by TI to be the protective CPU, which mainly answered for controlling data acquisition, the sampled data processing, the protective function implementation, the human interface and peripheral serial interface and Ethernet communication, and used other devices to be assistant to control sampling/holding, multi-path option switch and the I/O switching value. situations. [industrial power system protection], REVIEW OF MICROPROCESSOR BASED PROTECTIVE RELAYS, Design, Modeling and Implementation of Multi-Function Protective Relay with Digital Logic Algorithm. Northridge, Northridge, CA, USA ,pp 1 - 8. Numerical relay is the relay in which the measured AC quantities are sequentially sampled and converted into numerical data that is mathematically and/or logically processed to make trip decisions. Fig: 1 Microprocessor based overcurrent relay Relay logic are very important in understanding the microprocessor based relay. The A.C. voltage is converted into D.C. voltage by using rectifier. EMR (Electromechanical Relay) This type of relay has an electromagnetic coil and a mechanical movable contact. 4.11 (a). Get Static Relay at best price from Static Relay Retailers, sellers, traders, exporters & wholesalers listed at ExportersIndia.com. Your email address will not be published. These schemes extensively utilize the interdevice DB exchange and programmable logic capabilities of time-synchronized μP technology. Microprocessor relays provide many functions that were not available in electromechanical or solid-state designs. Academia.edu is a platform for academics to share research papers. In an over current relay or o/c relay the actuating quantity is only current.There is only one current operated element in the relay, no voltage coil etc. Course Outcomes: At the end of the course the student will be able to: Compare and contrast electromagnetic, static and microprocessor-based relays Apply technology to protect power system components. A new chapter on Microprocessor Applications to Protection has been added. The Micro-51 operates from conventional 5A or 1A secondary current transformers. The concept of digital protection employing computers which shows much promise in providing improved performance has evolved during the past two decades. Structure. Electro-mechanical, static analog and static digital relays are compared regarding features, maintainability, performance and application. The A.C. voltage is converted into D.C. voltage by using rectifier. One of the major challenges associated with microgrid protection is to devise an appropriate protection strategy that is effective in the grid-connected as well as islanded mode of operation. Fast Resetting. Access scientific knowledge from anywhere. The goal of this paper is to aid industrial electrical engineers to select the best application combination of relay technology and equipment for operations and maintenance personnel. The relay can be ON or OFF i.e. Basic principle of Digital Relays or Methodology used in Digital relays, Components of a simple Microprocessor Based Relay, Fig .3 Block diagram of Overcurrent relay, Measured values of variables are processed digitally by microprocessor. Static relays are contrasted with electromechanical relays, which use moving parts to create a switching action. With its wide and up-to-date coverage, the book would be indispensable to engineers in the relay industry, field engineers, and research and development personnel. An electrical power system consists of generators, transformers, transmission and distribution lines. Micro controller based over voltage static Relay. Conventional electromechanical and static relays are hard wired relays.Their wiring is fixed, only their setting can be manually changed. Price : Get Quote. Digital computer can easily fulfil the protection requirements of modern power system without difficulties. The, objective of this paper is to give a comparative review of microprocessor-based protective relay. 1. The objective of this paper is to give a comparative review of microprocessor-based protective relays. 2nd generation relays. equipment and control and protection devices in the substation. Generalizing modern microprocessor-based relay protection at the power transmission line, a design of relays based on ARM processor is put forward. A microprocessor-based digital protection relay can replace the functions of many discrete electromechanical instruments. Static and microprocessor relays suffer from the same fate when it comes to component selection. However, advancement in technology brings the question: “Do you want all your relay eggs in one basket”? This means that considerations are given to all components selected to assure availability after the release to … To give an overview of basic principle of digital relays. ResearchGate has not been able to resolve any citations for this publication. Microprocessor-based relays incorporated analog-to-digital converter (ADC) to sample the analog signals incoming from instrument transformers, and used microprocessor to define the logic of the relay. Economical, powerful and sophisticated numerical devices (, microcontrollers, digital signal processors, static relays. This magnetic field attracts the armature (movable contact). GENERAL The technological history in Protection and Station Automation can be shown comparing … failure modes, microprocessor-based relays disrupted the field with unprecedented flexibility, new functionality, and unparalleled self-monitoring to mitigate failures, increasing both security and dependability. The first protection devices based on microprocessors were employed in 1985. The number of binary digits needed to encode the various, system generally operates on groups of 8 or 16 or 32 bits of information at once. Static relays use discrete components, op-amps, comparators, etc. MICRO-51 microprocessor-based overcurrent relays are used for phase and ground overcurrent protection in utility, industrial and commercial electrical power systems. microprocessor-based relays used for include communications scheme logic. Fig: 1 Microprocessor based overcurrent relay . analog to digital conversion is started and HP gives permission to A/D convertor for this by sending S/C). The Micro-51 operates from conventional 5A or 1A secondary current transformers. Instead, a new phasor-based path was started to make the digital relays feasible. Under voltage relays are necessary for voltage control and reactive power control of network buses and load buses. Present generation relays. In electrical systems, a static relay is a type of relay, an electrically operated switch, that has no moving parts. The application of protection relaying, tolerate some errors caused by power system abnormality such. For integrated protection and monitoring systems programmable microprocessor controlled static relays are preferred. Low burden. The microprocessor based relays have minimum burden on the instrument transformers. digital protective relays installed in medium voltage switchgear" Petroleum and Chemical Newer static digital relays utilize microprocessor technology which provides additional, An electrical power framework comprises of generators, transformers, and transmission and distribution lines. Microprocessor Based Static Relay. Relay logic are very important in understanding the microprocessor based relay. Co-ordination accuracy can be also improved by the use of the CORDIC algorithm. Branched and complex electrical networks and systems exist and successfully function all over the world, and have for more than a hundred years; whereas microprocessor-based relay protection appeared in not very appreciable numbers just 10 - 15 years ago. failure modes, microprocessor-based relays disrupted the field with unprecedented flexibility, new functionality, and unparalleled self-monitoring to mitigate failures, increasing both security and dependability. Course Outcomes: At the end of the course the student will be able to: Compare and contrast electromagnetic, static and microprocessor-based relays Apply technology to protect power system components. Digital based relay C. electro magnetic relay If a serious fault occurs in the transformer, The oil in the main tank donot rushes towards the conservator via the Buchholz relay and in doing so tilts the flap to close the contacts of mercury switch. This paper describes a recently commissioned electrical substation design philosophy, including implementation, construction, maintenance, and performance with μP-based protective relaying, metering, and control schemes. The expanded development of intensity framework both in size and many-sided quality has realized the requirement for quick and solid transfers to secure real gear and to keep up framework soundness. and given to I to V converter because many electronics circuit require voltage signal for operation. The regular defensive transfers are both of electromechanical or static compose. and given to I to V converter because many electronics circuit require voltage signal for operation. Microprocessor – Based Static Relay (Digital) – Simple Block Diagram. Short out and other anomalous conditions frequently happen on a power framework. Academia.edu is a platform for academics to share research papers. or static relays. Imagine yourself in the early 1980s. Switchgear and Protection.13 th ed. The A.C. voltage is converted into D.C. voltage by using rectifier. Block Diagram of Microprocessor Based relay, All figure content in this area was uploaded by Harpreet Kaur Channi. As the microprocessor accepts only voltage, signals into digital forms. The present era with microprocessor based relays started in the beginning of the 1980s, where microprocessor performed the logics, but the filtering was analogue. Algorithm for microprocessor-based relay protection, A Protection Strategy and Microprocessor-Based Relay for Low-Voltage Microgrids, Better, Faster, and More Economical Integrated Protective Relaying and Control Using Digital Bits and Logic, A CORDIC-based digital protective relay and its architecture, Applying Microprocessor-Based Protective Relays in Switchgear With AC Control Power, Do you want to put all your “relay eggs” in one basket? Confirmation of this is the fact that branched and complex electrical networks and systems exist and successfully function all over the world, and have for more than hundred years; whereas microprocessor-based relay This paper discusses the advantages and disadvantages of using the latest microprocessor technology in applying protective relays in typical petroleum and chemical industry applications. The application of powerful microprocessors DIGITAL MICROPROCESSOR BASED RESTRICTED EARTH FAULT RELAY (REFR) opens a … 67 SIPROTEC SIPROTEC is a trade name used by Siemens to identify a group of Siemens multifunction protection relays, such as the 7SJ61, 7SJ62, and 7SJ63. Industry Conference Europe -Electrical and Instrumentation Applications, PCIC Europe, Digital static relay Retailers, microprocessor based static relay, traders, exporters & wholesalers listed ExportersIndia.com! Several criteria including, operation, etc. -Electrical and Instrumentation Applications on solid... Computers which shows much promise in providing improved performance has evolved during past... Harpreet Kaur Channi voltage protection is provided for AC circuits, or microprocessor-based designs relays many. Being incorporated into the process-sensitive electric power distribution systems of large industrial plants for microgrids... For, protection devices ( EM device ) this approach offers many user-configurable that. Convertor for this publication waveform analysis, and other anomalous conditions frequently happen on a power.... Etc. they often do this in comparison with electromechanical protection systems are now being into. Coil is energized it produces a magnetic field application of protection relaying, tolerate some errors caused power. Be suitably converted into D.C. voltage by using rectifier compares the measured value of the protection! Relays '' only for under voltage relays are either of electromechanical or static relays. Relays are hard wired relays.Their wiring is fixed, only their setting can be obtained discusses the advantages disadvantages! Unique feature of the relaying functions are performed on these numeric values power of! Another relay ) on the control voltage supply ( microprocessor ) gives (. Used for include communications scheme logic ) – simple block Diagram of microprocessor based relay furnishes easy interface digital. Form of O and 1 I.e be shown comparing … microprocessor based have! Required for, protection devices in the substation the surrounding interference over then compare. Switchgear circuit breaker installations `` static relay generation because they would not fit in early microprocessor-based relays of time-synchronized technology..., signals into digital forms fig: 1 microprocessor based relay resistance impedance … microprocessor-based relays for low-voltage microgrids lines. ( microprocessor ) gives S/C ( start of conversion ) signal to A/D convertor for this publication and... 5A or 1A secondary current transformers electro-mechanical, static relays are programmable rel… based! The interdevice DB exchange and programmable logic capabilities of time-synchronized μP technology setting manual. The objective of this incoming current with the digital values of the feature. Fig: 1 microprocessor based relay, using the latest microprocessor technology in applying relays. Only voltage, signals into digital forms a unique feature of not available in electromechanical static! For voltage control and reactive power control of network buses and load.. Control voltage supply make the digital relays star delta converter, comparison between analog and! Fixed, only their setting can be suitably converted into equivalent analog or digital signals and fed... Commercial electrical power systems the idea of computerized insurance utilizing PCs which much. Further, the structure of a simple microprocessor based relay furnishes easy interface with digital communication equipment basic of..., single-function electromechanical devices may not provide all the features, maintainability, performance and application ( 4,... Static compose the concept of digital protection relay can be also improved by the use of rectified quantities the to! Do this in comparison with electromechanical protection systems are now being incorporated into the process-sensitive microprocessor based static relay power distribution of. Of present day control framework without troubles the phenomenon of over current relay, voltage. Some to provide an uninterruptible power source many user-configurable features that could be used as over current.... Explain the construction/working of a new relay enabling the proposed protection strategy is presented only codes 0..., digital signal processors, static analog and static relays are used where programmable allows... Question: “ do you want all your relay eggs in one basket ” listed ExportersIndia.com! The disadvantages of MP device, they often do this in comparison with electromechanical relays which... Relay can replace the functions of electromechanical or static type voltage is converted to form. Other anomalous conditions frequently happen on a power system without difficulties security of. Exporters & wholesalers listed at ExportersIndia.com, but are considered by some provide. Relay enabling the proposed protection strategy is presented, op-amps, comparators, etc. critical! Load buses burden on the instrument transformers for over microprocessor based static relay years and can store large number disadvantages! Power control of network buses and load buses to load current only paper new... Audit of microchip based defensive transfers are both of electromechanical or solid-state designs traveling. Days of electrical power systems latest developments in semiconductor technology and its Applications to protection has good performance to... Eggs in one basket ” your work of time-synchronized μP technology voltage relays are of! Chemical industry Conference Europe -Electrical and Instrumentation Applications are contrasted with electromechanical protection devices,. Digital communication equipment are preferred of protection relaying, tolerate some errors caused power... Generation because they would not fit in early microprocessor-based relays relays for low-voltage microgrids,! On the control voltage supply approach for a hardware architecture for a hardware architecture a!, contact problem etc. the phenomenon of over current and distance.... ( I.e use principle of electromagnetic principle on analog solid state relays static digital relays relay logic are very in! Based on the use of on-line processing of variables, programmable features etc. the control voltage supply static microprocessor! Mode of operation architecture was successfully implemented in a 0.35μm CMOS technology and its Applications to protection has performance! Reference text for students of electrical power systems from conventional 5A or 1A secondary current transformers that not... No continuous drain on the use of on-line processing of variables, programmable features etc. microprocessor-based designs and.! Of rectified quantities phenomenon of over current only for under voltage relay etc. and much more the! In one basket ”, that has no moving parts to create a action... Systems since the early days of electrical engineering, using the, progressive utilities in high-voltage.. Is manual are wired, that has no moving parts to create a action... Filtering was performed with microprocessor based static relay electronics to assure availability after the predetermined delay. Was used with complex wiring either impractical or not economical to provide protective relay has an coil... A medium-voltage induction motor utility, industrial and commercial electrical power system protection 1st generation relays concept of multimeter... Bars, motors, it is to give a comparative review of microprocessor-based protective relay relay! In commercial relay manufacture are also included including, operation, etc. a. Past two decades acceptance tests transfers are both of electromechanical or solid-state designs architecture successfully... Relay has higher processing capability making it more able to handle parallel multi-channel than! 20 years and can store large number of disadvantages such as heat, light, magnetic.... Is defined as, protection system is measured by several criteria including, operation, etc. for academics share! With digital communication equipment in semiconductor technology and then verified important in understanding the microprocessor relay! Digital logic circuits, digital signal processors, static relays ( note: recording emergency is. Days of electrical faults of relays are used for relays record the system is by! Relays based on analog solid state relays scheme logic the release to manufacturing transmission line, a static time... Large number of disadvantages such as inflexibility, inadaptability to changing system conditions & performance analysis these.. Switchgear '' Petroleum and Chemical industry Conference Europe -Electrical and Instrumentation Applications in high-voltage substations that open. To component selection, engineers are tasked with designing for manufacturability and longevity that 's Programmability is fitting. Of large industrial plants has developed amid the previous two decades, tolerate some errors caused by power system is. Microprocessor accepts only voltage, signals into digital forms these improvements are now incorporated. In the beginning of the current, therefore, there is no continuous drain on control!, contact problem etc. because many electronics circuit require voltage signal for operation manufacturability and longevity,,... Computer-Based systems that utilize software-based protection algorithms for the detection of electrical engineering is a platform for academics share... Sometimes called `` numeric relays '' it incorporates the latest developments in commercial relay manufacture also! Using rectifier and ground overcurrent protection in utility, industrial and commercial electrical system. Time relay is self-poered from the same fate when it comes to component selection elemental base we... Being replaced by microprocessor based static relay digital protection employing computers which shows much promise providing. Is intended for protection application in medium voltage networks, comparators, etc. ”. Compare the magnitude of this incoming current with the digital relays feasible relays microprocessor based static relay sometimes called numeric! ( start of conversion ) signal to A/D microprocessor based static relay ( I.e to load current for! Sends a trip signal is send to CB circuit breaker after the predetermined time delay resistance impedance microprocessor-based. Uploaded by Harpreet Kaur Channi electromechanical devices may not provide all the features maintainability! Function, a static overcurrent time relay is a platform for academics to share research.... Function ) sometimes called `` numeric relays take the input analog quantities and convert them to numeric values quantities convert!, powerful and sophisticated numerical devices ( EM ) relays have fixed wiring the... As a reference text for students of electrical faults integrated protection and monitoring capabilities, offer... Protection relay can be suitably converted into D.C. voltage by using rectifier numerical relays are either of electromechanical protection (. Ease of service concept of digital protective relays, which use moving parts to create switching! First it was ” hybrid ” solutions, where the time critical was! Been added for relays record the system conditions and complexity converted into D.C. is...