Numerical relays protection and control products for power. Life cycle considerations for microprocessor relays. Microprocessor based protective relays are developed on the basis of early computer relaying devices. Microcontroller based protective relay testing system. Electromechanical and static relays have fixed wiring and the setting is manual. Life expectancy of microprocessorbased protective relays. Tests of microprocessorbased relay protection devices.
The paper concludes by showing many transmission line protection applications for microprocessor based relays. This paper proposes a protection strategy based on microprocessorbased relays for lowvoltage microgrids. Using event recordings to verify protective relay operations a. But microprocessor based relay protection devices are gradually driving out the traditional electromechanical and even electronic relay. One improvement is the use of programmable logic to reduce and simplify wiring. Schwartz, schweitzer engineering laboratories, inc.
The microprocessor may use some kind of counting technique, or use the discrete fourier transform dft to implement the algorithm. With the advent of more and more powerful microprocessors and the development of analytical algorithms, microprocessor based protective relays may provide a considerable. Microprocessor based relays are prefer able because several types of characteristics can be an overcurrent relay algorithm normally includes a implemented in the same hardware or with a minimum digital filter to extract the fundamentalfrequency com change of hardware 1,2. The relays use programmable logic to reduce and simplify wiring. Microprocessorbased overcurrent relays article pdf available in ieee transactions on industrial electronics ie331. The microprocessorbased scheme consist of a multifunction relay that provides three zones of step time distance protection, three levels of instantaneous or definite time directional ground overcurrent protection, a directional ground time overcurrent function, and threeshot recloser 9. Microprocessorbased protective relays applications in nigeria.
Abb microprocessor based protective relays traditionally have control. Further, the structure of a new relay enabling the proposed protection strategy is presented. A fully integrated ied equipped substation with 25 breakers. Protective relays feature past, present, and future a. Dec 28, 2015 fundamentals of microprocessor based protective relays suhag patel, p. Abstractthis report covers issues concerning the security of electronic communication paths to protective relays. Frequency racking is a method commonly t applied in microprocessorbased relays 2 3 4 frequency.
The timing method is dictated by how the relay samples the measured signal. The article is a continuation of a set of the authors previous publications about the reliability of the microprocessorbased protective devices. In case of line protection via distance protection schemes, microprocessorbased relays also provide over current protection, directional over current protection for selectivity. Microprocessorbased relays, also called digital relays, have a proven track record of reliability, with over 100,000 relayyears of field experience. A big difference between conventional electromechanical and static relays is how the relays are wired.
Digital relays are the functional replacements for electromechanical protective relays and may include many protection functions in a single unit, as well as providing metering, communication, and selftest. Protective relays are designed to take action when abnormal. Microprocessorbased protective relays deliver more information and superior reliability with lower maintenance costs richard d. Micro51 microprocessor based overcurrent relays are used for phase and ground overcurrent protection in utility, industrial and commercial electrical power systems. Introduction protective relays play a critical role in the operation of the electrical power system. When microprocessor relays began to be applied in the. Microprocessor relays with logic and communication capabilities can accomplish this type of scheme by using either hardwired trip contacts or by using communication signals between each other to transfer statuses. If in devices performing the function of protective relays one uses not rom. A customized logic algorithm that has been programmed into microprocessor based motor protection relays, eliminating additional undervoltage, control, timing relays, and wiring associated with traditional schemes, is described in this paper. Microprocessorbased distribution relay applications schweitzer.
Reliability of microprocessor based relay protection devices myths and reality part i by dr. Microprocessorbased protective relays applications in. Topics such as cybersecurity and instrument transformers are also explored. Operation and maintenance of protective relays and. Vladimir gurevich, israel electric corporation this first article in a twopart series examines four basic theses about the ostensibly high reliability of microprocessor based relay protection mp touted by supporters of mp. Life expectancy of microprocessorbased protective relays ied krisys electrical 11 feb 18 04. Microprocessorbased relays provide technical improvements and cost savings in several ways. In utility and industrial electric power transmission and distribution systems, a digital protective relay is a computer based system with software based protection algorithms for the detection of electrical faults. Field evaluation of automatic restart of essential motors. Microprocessor based protection relays, document number.
Relay information type, part number, style, and instruction manual. Most of todays microprocessor based relays implement multifunctional protection features. Analysis of microprocessor based protective re lays mbpr. Microprocessor relays are computer based systems that utilize software based protection algorithms for the detection of electrical faults. Now, microprocessor based digital relays are becoming the norm for new installations and many replacements, because of their improved protective capabilities, reliability, and additional features. Commissioning microprocessor based ied communication systems an65a00 6 b.
Introduction protective relays evolved from singlefunction electromechanical devices, through singlefunction or integrated static devices into a multifunction integrated microprocessor. Introduction protective relays playa critical role in the operation of the electrical power system. Typically, a utility utilizes the extended capability of microprocessor relays to provide status, control and metering functions to a station rtu via a serial communication link. Users have become accustomed to the electromechanical relays ability to last 50 plus years and this has strained the expectations of microprocessor based relays. They, in turn, inherit some of the computer relays functions. In practice it has turned out that most mpds simply do not sense the substitution of the whole printed board of one kind for the board of other kind which is not compatible with relay current settings. Microprocessor based distribution relays contribute to improved reliability and reduced costs on electric power systems. Substation commissioning to verify correct data reporting between a host device and an ied is a tedious and lengthy process. The text covers smart grids, integration of wind and solar generation, microgrids, and mmprs as the driving aspects of innovations in protective relaying. The protective relays that may be tested by our developed relay testing system are. Overload protection using microprocessor based overvoltage. Dec 24, 2012 compared to static relays, digital relays introduce analogue to digital convertor ad conversion of all measured analogue quantities and use a microprocessor to implement the protection algorithm.
Now, microprocessorbased digital relays are becoming the norm for new installations and many replacements, because of their improved protective capabilities, reliability, and additional features. This paper proposes a protection strategy based on microprocessor based relays for lowvoltage microgrids. It is the goal of this paper to present the reader with some background material and discussions by which they can. Electric utilities company of nigeria eucn have traditionally used electromechanical emr distance relays for the protection of transmission lines in the past. The statistical data introduced by the author coincide with data of other authors and con. Present day microprocessor based protective relays barely resemble their early 1990s distant cousins. The source concept considerations in a protective relay.
Microprocessorbased distribution relay applications. Microprocessorbased transmission line relay applications. Overcurrent relays, undercurrent relays, frequency relays. Review of microprocessor based protective relays request pdf. The internal architecture and principles of operation of microprocessor based devices including socalled microprocessor protective relays have little in common with devices called electric relays. The functions of electromechanical protection systems are now being replaced by microprocessorbased digital protective relays, sometimes.
Operation and maintenance of protective relays and associated. By using the boolean simplification, we can represent the logic in a microprocessor based relay in a few different ways. Conventional relays like electromechanical relays employed bulky sized mechanical comparators which reduced their speed and these relays often served a single function and a single characteristic. Nov 08, 20 this is a recreation of the first paper i ever presented from the neta conference in 2001 that was the foundation of the relay testing handbook series. Reliability of microprocessorbased relay protection. Protective relays, associated communication systems, voltage and current sensing devices, station batteries and dc control circuitry. This is a recreation of the first paper i ever presented from the neta conference in 2001 that was the foundation of the relay testing handbook series. We have designed and implemented microprocessor based relay testing system through the use of the new technologies such as microcontroller. Microprocessorbased protective relays deliver more. Misapplication of microprocessor protective relays has the same impact on protection reliability as the misapplication of relays of the prior technologies had. Commissioning microprocessor based ied communication systems. Protective relay testing verification and documentation of. Typical examples are rez 1 universal phase and ground distance relay for.
But in reality it was just the tip of the iceberg so to speak. Microcontroller based overcurrent relay and directional. Such relays are also termed as microprocessor type protective relays. Microprocessorbased relays can create comtrade files using either timing method described in section ii i. Problems and solutions 337 examining the relays reaction in supplying the signal to them. Hence domestic and industrial facilities are increasingly investing in microprocessor based relays to. Understanding microprocessor based relay logic part 1. These new relays would quickly be established as the wave of the future. The relays also provide protection for bus faults, breaker failure, and highside. Understanding the limitations of replaying relaycreated. Microprocessor based relays, also called digital relays, have a proven track record of reliability, with over 100,000 relay years of field experience.
Tests of microprocessor based relay protection devices. The micro51 operates from conventional 5a or 1a secondary current transformers. At first it was hybrid solutions, where the time critical filtering was performed with analogue electronics. Integrity of data exchange between the field devices and a host. Numerical relays are based on the use of microprocessors. File 1 file 2 file 10 60000 63199 40001 41153 41154 41408 41409 41919 4x memory read only readwrite capable quasireadwrite. 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. Power system, microprocessor based relays, electromechanical relays, engineering design, maintenances costs, protection schemes. Reliability of microprocessorbased relay protection devices. A proposed scheme of overcurrent relays dealing with programming of the singleboard microcomputer tk85, built by nec around intels 8bit 8085 microprocessor, is described. Introduction digital fault recorders dfr and modern microprocessor based relays have records consisting of oscillographic waveforms and event logs that can give the necessary information needed to.
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