In addition, microprocessorbased protective relays have a builtin feature for measuring phase angles and computing the busbar frequency from the measured voltage signal from the vt 2. Operation, maintenance, and field test procedures for. The statistical data introduced by the author coincide with data of other authors and con. But in reality it was just the tip of the iceberg so to speak. 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 devices myths and reality part i by dr. Microprocessorbased relays provide technical improvements and cost savings in several ways. These new relays would quickly be established as the wave of the future. Relaying with microprocessor based relays fernando calero schweitzer engineering laboratories, inc. Chris is an electrical engineering technologist, a journeyman power system electrician, and a professional engineer. 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. Medium voltage products pr512 microprocessorbased self.
Protective relays are of three different technology eras, electro mechanical, electronic and microprocessor based electromechanical relays installed up to 1983 with a 30 year life expectancy electronic relays installed 1980 through 1995 with 15 to 20 year life expectancy. With the advent of more and more powerful microprocessors and the development of analytical algorithms, microprocessor based protective relays may provide a considerable. Protective relays feature past, present, and future a. Reliability of microprocessorbased relay protection devices. Operation and maintenance of protective relays and associated. 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. The question arises if the microprocessor based protection device is a relay in the full sense of the word. Relaying with microprocessorbased relays fernando calero schweitzer engineering laboratories, inc. Proper testing of these protective relays ensures the integrity of the protection scheme, prevents nuisance. Life expectancy of microprocessorbased protective relays ied krisys electrical 11 feb 18 04. Reliability of microprocessor based relay protection devices. Abstractthis paper explains how microprocessorbased protective relays are used to provide both control and protection functions for small microgrids. Also, microprocessor based relays can provide easy current magnitude and angle checks to ensure proper connections.
Rebirth of negativesequence quantities in protective. The emphasis is on numerical relays since they have facilitated the calculation of symmetrical components. Vladimir gurevich, israel electric corporation this first article in a twopart series examines four basic theses about the ostensibly high reliability of microprocessorbased relay protection mp touted by. The article is a continuation of a set of the authors previous publications about the reliability of the microprocessorbased protective devices. Power system, microprocessorbased relays, electromechanical relays, engineering design, maintenances costs, protection schemes. On closer examination it turns out that the microprocessor based relay is a small computer in which the output circuits usually builtin ct or vt fig. The functions of electromechanical protection systems are now being replaced by microprocessorbased digital protective relays, sometimes called numeric relays.
Present day microprocessor based protective relays barely resemble their early 1990s distant cousins. In addition, microprocessor based protective relays have a builtin feature for measuring phase angles and computing the busbar frequency from the measured voltage signal from the vt 2. Life expectancy of microprocessorbased protective relays. Understanding microprocessor based relay logic part 1. C16 working group june 2014 relay scheme design using microprocessor relays a supplement to relay trip circuit design by ieee psrc 1999. Protective relaying senses the abnormal condition in a part of power system and gives an alarm or isolates that part from healthy system. Protective relays are designed to take action when abnormal. The relays use programmable logic to reduce and simplify wiring. Microprocessorbased overcurrent relays article pdf available in ieee transactions on industrial electronics ie331. Microprocessorbased relay testing, distributionindustrial.
Analysis of microprocessor based protective re lays mbpr. Complete monitoring of a relay and the associated relay scheme helps to reduce maintenance costs because the time between routine maintenance can be extended. In case of line protection via distance protection schemes, microprocessorbased relays also provide over current protection, directional over current protection for selectivity. Fundamentals of microprocessor based protective relays suhag patel, p. Microprocessorbased distribution relay applications. Meth ods have been suggested 26 to implement relaying functions using a dedicated microprocessor.
Users have become accustomed to the electromechanical relays ability to last 50 plus years and this has strained the expectations of microprocessor based relays. Digital energy the ge multilin ddfr is a power system fault recorder that collects, archives and manages disturbance and fault information that is recorded by microprocessor based protective relays distributed throughout your local power system. The increased growth of power system both in size and complexity has brought about the need for fast and reliable relays. When microprocessor relays began to be applied in the. Therefore, you can connect the cts in wye on both sides of the bank, regardless of the transformer bank connection. Myths and reality 169 insufficient mechanical resource, as a kind of the relay, is absolutely unreasonably. Understanding microprocessor based relay logic part 3 relay.
Dec 28, 2015 fundamentals of microprocessor based protective relays suhag patel, p. Moreover they do not interfere with any electronic apparatus near the installation. It is the goal of this paper to present the reader with some background material and discussions by which they can. This 8085 kit based interface circuit controls 64 relays. Using protective relays for microgrid controls william edwards and scott manson, schweitzer engineering laboratories, inc. Overcurrent relays, undercurrent relays, frequency relays. The improvement in enlargement of power system both in mass and difficulty has brought the requirement for quick and dependable relays to defend. Problems and solutions 337 examining the relays reaction in supplying the signal to them. The digital protective relay is a protective relay that uses a microprocessor to analyze power system voltages, currents or other process quantities for the purpose of detection of faults in an electric power system or industrial process system. Abstractthis paper explains how microprocessorbased protective relays are used to provide both control and protection functions for. Microprocessorbased protective relays deliver more. Microprocessorbased protective relays deliver more information and superior reliability with lower maintenance costs richard d. They are considered as a complete protection package in a single unit.
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. Microprocessor based transformer differential relays can make the delta internally. This paper deals with the implementation of inversetime multiple overcurrent relays. The new chapters in this new edition, are focused on microprocessor based protection relays, and their integration in substation automation systems. A customized logic algorithm that has been programmed into microprocessorbased motor protection relays, eliminating additional undervoltage, control, timing relays, and wiring associated with traditional schemes, is described in this paper. Life cycle considerations for microprocessor relays. The relays provide protection for bus faults, breaker failure, and highside transformer blown fuse detection at no or minimal additional cost. Microprocessorbased transformer differential relays can make the delta internally. The main features of a good protective relaying are its reliability, sensitivity, simplicity, speed, and economy. 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. Microprocessor based relaying free download as powerpoint presentation.
Operation and maintenance of protective relays and. The protective relays that may be tested by our developed relay testing system are. A relay which is actuated by rotation of the shaft of some type of motor, for example, a shadedpole, inductiondisk, or hysteresis motor. 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. 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. This transition from the electromechanical to the numerical relays can be justified by the large flexibility and the wonderful features such as. Schwartz, schweitzer engineering laboratories, inc. We have designed and implemented microprocessor based relay testing system through the use of the new technologies such as microcontroller.
However, during the past 1520 years, there has been a widespread displacement of emr by microprocessorbased relay protection devices gurevich, 2012. The pr512 microprocessor based protection relays ensure correct operation and are immune to unwarranted trips, even in the presence of interference caused by electronic apparatus, by stormy weather conditions or electric discharges. Microcontroller based protective relay testing system. Microcontroller based overcurrent relay and directional.
Nov 11, 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. Authors paul price, nate myers, jim dehaan bureau of reclamation hydropower technical services group denver, colorado 5d. Understanding microprocessor relay logic basic digital. In case of line protection via distance protection schemes, microprocessor based relays also provide over current protection, directional over current protection for selectivity.
He is also the author of the relay testing handbook series and founder of valence electrical training services. Reliability of microprocessor based relay protection devices myths and reality part i by dr. The protective relays do not eliminate the possibility of fault occurrence on the power system rather their circuit actions start only after the fault has occurred on the system. Microprocessorbased protective relays applications in.
Fist 38, operation, maintenance, and field test procedures for protective relays and associated circuits 5a. Microprocessorbased protective devices, relay damages, relay protection reliability. Introduction protective relays play a critical role in the operation of the electrical power system. Now, microprocessorbased digital relays are becoming the norm for new installations and many replacements, because of their improved protective capabilities, reliability, and additional features. Electromechanical and static relays were used in the beginning which had several drawbacks such as high burden on instrument transformers, long operating time, contact problems, inflexibility, inadaptability to changing system conditions, complexity and cost etc. Thus, phase angles and frequency measurements are also available for use within the relay. Field evaluation of automatic restart of essential motors. Abstractthis report covers issues concerning the security of electronic communication paths to protective relays. 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. A proposed scheme of overcurrent relays dealing with programming of the singleboard microcomputer tk85, built by nec around intels 8bit 8085 microprocessor, is described. Most of todays microprocessor based relays implement multifunctional protection features. The pr512 microprocessorbased protection relays ensure correct operation and are immune to unwarranted trips, even in the presence of interference caused by electronic apparatus, by stormy weather conditions or electric discharges. 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.
Protective relaying is a team work of ct, pt, protective relays, time delay relays, trip circuits, circuit breakers etc. Also, microprocessorbased relays can provide easy current magnitude and angle checks to. 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. Tests of microprocessorbased relay protection devices. A digital protective relay may also be called a numeric protective relay.
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