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. Problems and solutions 337 examining the relays reaction in supplying the signal to them. 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. 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. Overcurrent relays, undercurrent relays, frequency relays. In case of line protection via distance protection schemes, microprocessorbased relays also provide over current protection, directional over current protection for selectivity. 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. We have designed and implemented microprocessor based relay testing system through the use of the new technologies such as microcontroller. The relays provide protection for bus faults, breaker failure, and highside transformer blown fuse detection at no or minimal additional cost. This transition from the electromechanical to the numerical relays can be justified by the large flexibility and the wonderful features such as. Operation and maintenance of protective relays and associated. Complete monitoring of a relay and the associated relay scheme helps to reduce maintenance costs because the time between routine maintenance can be extended.
Microprocessorbased protective relays deliver more information and superior reliability with lower maintenance costs richard d. Microprocessorbased transformer differential relays can make the delta internally. Microprocessorbased overcurrent relays article pdf available in ieee transactions on industrial electronics ie331. Microprocessorbased protective devices, relay damages, relay protection reliability. Now, microprocessorbased digital relays are becoming the norm for new installations and many replacements, because of their improved protective capabilities, reliability, and additional features. The increased growth of power system both in size and complexity has brought about the need for fast and reliable relays. Proper testing of these protective relays ensures the integrity of the protection scheme, prevents nuisance.
Microprocessor based relaying free download as powerpoint presentation. Operation, maintenance, and field test procedures for. A proposed scheme of overcurrent relays dealing with programming of the singleboard microcomputer tk85, built by nec around intels 8bit 8085 microprocessor, is described. Reliability of microprocessor based relay protection devices myths and reality part i by dr. Life cycle considerations for microprocessor relays. Life expectancy of microprocessorbased protective relays. 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. The emphasis is on numerical relays since they have facilitated the calculation of symmetrical components. Protective relaying is a team work of ct, pt, protective relays, time delay relays, trip circuits, circuit breakers etc.
Chris is an electrical engineering technologist, a journeyman power system electrician, and a professional engineer. With the advent of more and more powerful microprocessors and the development of analytical algorithms, microprocessor based protective relays may provide a considerable. But in reality it was just the tip of the iceberg so to speak. Tests of microprocessorbased relay protection devices. Meth ods have been suggested 26 to implement relaying functions using a dedicated microprocessor. It is the goal of this paper to present the reader with some background material and discussions by which they can.
Introduction protective relays play a critical role in the operation of the electrical power system. 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. He is also the author of the relay testing handbook series and founder of valence electrical training services. 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. Myths and reality 169 insufficient mechanical resource, as a kind of the relay, is absolutely unreasonably. This paper deals with the implementation of inversetime multiple overcurrent relays. Fist 38, operation, maintenance, and field test procedures for protective relays and associated circuits 5a. 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 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. Rebirth of negativesequence quantities in protective. Abstractthis report covers issues concerning the security of electronic communication paths to protective relays. Thus, phase angles and frequency measurements are also available for use within the relay. Microprocessorbased distribution relay applications.
Life expectancy of microprocessorbased protective relays ied krisys electrical 11 feb 18 04. Understanding microprocessor relay logic basic digital. This 8085 kit based interface circuit controls 64 relays. 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. 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. Protective relays feature past, present, and future a. Also, microprocessor based relays can provide easy current magnitude and angle checks to ensure proper connections. Moreover they do not interfere with any electronic apparatus near the installation. In case of line protection via distance protection schemes, microprocessor based relays also provide over current protection, directional over current protection for selectivity. Also, microprocessorbased relays can provide easy current magnitude and angle checks to. 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. Microprocessor based inversetime multiple overcurrent relays.
Microprocessorbased relay testing, distributionindustrial. Most of todays microprocessor based relays implement multifunctional protection features. The article is a continuation of a set of the authors previous publications about the reliability of the microprocessorbased protective devices. 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. Protective relaying senses the abnormal condition in a part of power system and gives an alarm or isolates that part from healthy system. A relay which is actuated by rotation of the shaft of some type of motor, for example, a shadedpole, inductiondisk, or hysteresis motor. Understanding microprocessor based relay logic part 1. The protective relays that may be tested by our developed relay testing system are. Schwartz, schweitzer engineering laboratories, inc. However, during the past 1520 years, there has been a widespread displacement of emr by microprocessorbased relay protection devices gurevich, 2012.
Relaying with microprocessor based relays fernando calero schweitzer engineering laboratories, inc. Microprocessor based transformer differential relays can make the delta internally. When microprocessor relays began to be applied in the. Operation and maintenance of protective relays and. Reliability of microprocessorbased relay protection devices myths and reality part i by dr. The statistical data introduced by the author coincide with data of other authors and con.
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. 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. A digital protective relay may also be called a numeric protective relay. Therefore, you can connect the cts in wye on both sides of the bank, regardless of the transformer bank connection. Impedance calculation algorithm for microprocessor based.
Power system, microprocessor based relays, electromechanical relays, engineering design, maintenances costs, protection schemes. Users have become accustomed to the electromechanical relays ability to last 50 plus years and this has strained the expectations of microprocessor based relays. The functions of electromechanical protection systems are now being replaced by microprocessorbased digital protective relays, sometimes called numeric relays. 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. Analysis of microprocessor based protective re lays mbpr. 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. 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. Medium voltage products pr512 microprocessorbased self. Microcontroller based overcurrent relay and directional. Understanding microprocessor based relay logic part 1 history of protective relays. 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.
While most microprocessorbased relays, also called numeric or digital relays, have some automatic selftest functions, technicians still must understand how to test analog input and output circuitry as well as interpret the results. Power system, microprocessorbased relays, electromechanical relays, engineering design, maintenances costs, protection schemes. The question arises if the microprocessor based protection device is a relay in the full sense of the word. Abstractthis paper explains how microprocessorbased protective relays are used to provide both control and protection functions for small microgrids.
Understanding microprocessor based relay logic part 3 relay. 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. The new chapters in this new edition, are focused on microprocessor based protection relays, and their integration in substation automation systems. Authors paul price, nate myers, jim dehaan bureau of reclamation hydropower technical services group denver, colorado 5d. 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. These new relays would quickly be established as the wave of the future. 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.
The improvement in enlargement of power system both in mass and difficulty has brought the requirement for quick and dependable relays to defend. C16 working group june 2014 relay scheme design using microprocessor relays a supplement to relay trip circuit design by ieee psrc 1999. They are considered as a complete protection package in a single unit. Reliability of microprocessor based relay protection devices. Inversetime overcurrent relays play an important role in protecting transmission and distribution equip ment against overload and shortcircuit currents.
Protective relays are designed to take action when abnormal. Dec 28, 2015 fundamentals of microprocessor based protective relays suhag patel, p. Fundamentals of microprocessor based protective relays suhag patel, p. Microcontroller based protective relay testing system.