Study and analysis of modern numerical relay compared to. Relay logic is very important to understand the microprocessor based relay. While many are still operational, we are seeing that the lifecycle of the. Micro51 microprocessorbased overcurrent relays are used for phase and ground overcurrent protection in utility, industrial and commercial electrical power systems. 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 relays, also called digital relays, have a proven track record of reliability, with over 100,000 relayyears of field experience.
Microprocessor is that these are general purpose electronic processing devices which can be programmed to execute a number of tasks microprocessor is its speed, which is measured in hertz. He is also the author of the relay testing handbook series and founder of valence electrical training services. In short, a phase comparator compares two input quantities in phase angle vertically irrespective of the magnitude and operates if the phase angle between them is pdf file. Implementation and performance of synchrophasor function.
Dec 28, 2015 fundamentals of microprocessor based relays 1. Integral to microprocessor based relay tc2 cc in1 breaker status input in2 trip circuit monitor input optional. From the viewpoint of reliability, a statistical study between 2000 and 2009, posted by a. Numerical relays are microprocessor based relays whereas the other relays are controlled electromechanically.
Commissioning microprocessor based ied communication systems an65a00 6 b. Now, microprocessorbased digital relays are becoming the norm for new installations and many replacements, because of their improved protective capabilities, reliability, and additional features. Understanding microprocessor based relay logic part 1. That kit used for this purpose is vinytics vmc 8506 which has an inbuilt adc interface based on adc0809 chip and also some relays which can be turned on or off by providing simple 8085 instructions. When microprocessor relays began to be applied in the mid 1980s, little to no consideration was given to endoflife. Reliability of microprocessorbased protective devices revisited 35 1940 1950 1960 protective relays design life expectancy 30 25 20 15 10 5 years to obsolescene 1970 1980 1990 fig. Microprocessorbased relays, also called digital relays, have a proven track record of reliability, with over 100,000 relayyears of field experience. Microprocessorbased protective relays deliver more. 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. Such relays are also termed as microprocessor type protective relays. This 8085 kit based interface circuit controls 64 relays.
Chris is an electrical engineering technologist, a journeyman power system electrician, and a professional engineer. Relay scheme design using microprocessor relays a report to the. The article is a continuation of a set of the authors previous publications about the reliability of the microprocessorbased protective devices. Problems and solutions 335 periodicity once in 4 years only for electromechanical relays is established. A fully integrated ied equipped substation with 25 breakers testing the full complement of data displayed on a local monitoring system and rtu.
Distribution substations at electric cooperatives and municipal utilities have historically involved simple protection schemes consisting of feeder circuit overcurrent, reclosing, and transformer protection, either with highside. In the event of a fault, protective relays protect electrical systems, equipment, and people from serious damage and injury. Microprocessorbased distribution relay applications. Multiprocessor relays allow for 86 lockout relay functions to be moved into the relay logic, reducing the number of components in the system. Though this relay has a microprocessor, it lacks the attributes of a digitalnumeric relay, and hence the term microprocessor. Tests of microprocessorbased relay protection devices. The functions of electromechanical protection systems are now being replaced by microprocessorbased digital protective relays, sometimes. Experimental results with better relay characteristic performances and high flexibility for implementing the desired value of n, including noninteger values, are obtained. The references provide the required background knowledge and allow for further reading to explore some of the topics in greater detail. Based control 29 is given a unique numeric address, which reprcsents its location just as a sreet adalrcss represents the location of a house, dala are written into memory and read out of memory, based solely on thoir address. Life cycle experiences with microprocessor based relays and. Then a relatively simple microprocessor does a slow speed ad conversion of the dc signal, integrates the results to create the timeover current curve response, and trips when the integration rises above a set point.
The microprocessor may use some kind of counting technique, or use the discrete fourier transform dft to implement the algorithm. Similarly, the output of a logic function is activated, that is, high or deactivated, that is, low. Operation and maintenance of protective relays and associated. 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. Assuming 60 synchrophasors are produced per second, the synchrophasor interrupts are to be generated every 1,666. Description the powerlogic digital relay figure 1 is a multifunction, microprocessor based device which performs these functions. Tutorial on operating characteristics of microprocessorbased. Pullman, washington introducrlon advanced microprocessorbased distribution relays have features that improve distribution protection and aid in event analysis and testing references i, 2, 3, and 4. Fundamentals of microprocessor based protective relays suhag patel, p. Microprocessor based overload relay 3rb12 power supply. Understanding microprocessor relay logic basic digital. 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.
In a particular memory circuit, the addresses might start at 1oo0 and run consecutively. Ppt microprocessor based power system protection powerpoint. Chakravarty bihar college of engineering, patna 800 005, bihar, india this paper presents a microprocessorbased distancerelaying scheme suitable for the protection of ehv lines. Dear sirs, we would like to thank you for your patronage and interest in our sphere of activityand products. The space requirement for the microprocessor based relay scheme is much less than the electromechanical relay scheme 5, 6. Microprocessorbased overcurrent relays article pdf available in ieee transactions on industrial electronics ie331. Reserve questions until the conclusion time limitation. Numerical relays are based on the use of microprocessors. Microprocessorbased distribution relays provide technical improvements and cost savings in several ways. For the most effective protection, many utilities and industrial facilities are replacing aging electromechanical relays with new generation microprocessor based relays. Microprocessor based overload relay 3rb12 free download as powerpoint presentation. Medium voltage products pr512 microprocessorbased self. Revised edition released june 2009 previously presented at the distributech conference, february 2007 previous revised edition released february 2008.
Microprocessor based distribution relays contribute to improved reliability and reduced costs on electric power systems. Data verified includes, but is not limited to that of scenario a, but also, alarms, control, status, events, reports. Microprocessorbased distribution relay applications schweitzer. Implementation and performance of synchrophasor function within microprocessor based relays 37 another issue is the required resolution of the internal oscillator. Electromechanical relays had no significant drawbacks in their protection functions, but the additional features offered by the microprocessor technologies encouraged the evolution of.
Intelligent electronic devices ieds, have evolved over time in hardware and firmware with new features. The relays use programmable logic to reduce and simplify wiring. The relays provide protection for bus faults, breaker failure, and highside transformer blown fuse detection at no or minimal additional cost. Abstractthis report covers issues concerning the security of electronic communication paths to protective relays. For the most effective protection, many utilities and industrial facilities are replacing aging electromechanical relays with new generation microprocessorbased. Microprocessor based protective relays deliver more information and superior reliability with lower maintenance costs richard d. Numerical relays protection and control products for. Microprocessor is its speed, which is measured in hertz. By using the boolean simplification, we can represent the logic in a microprocessor based relay in a few different ways. Protecting distribution substation assets modern protection schemes with microprocessorbased relays abstract.
The results from the evaluation of the relays, combined 11 with the fieldobserved reliability life curve confirm that when relays are manufactured from highquality materials and highquality processes and the effects of aging ar e considered during product design, that microprocessor based relays can reliably. Electromechanical relays had no significant drawbacks in their protection functions, but the additional features offered by the microprocessor technologies. A big difference between conventional electromechanical and static relays is how the relays are wired. The goal of this paper is to contribute to the better understanding of microprocessor based 87l relays and bring.
Operation and maintenance of protective relays and. 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. Implementation, conflicts, and corrective actions steven v. The microcomputer sends a tripping signal instantaneously if the measured value of x is less than xi. 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. The micro51 operates from conventional 5a or 1a secondary current transformers. A proposed scheme of overcurrent relays dealing with programming of the singleboard microcomputer tk85, built by nec around intels 8bit 8085 microprocessor, is described. Microprocessor relays provide many functions that were not available in electromechanical or solidstate designs. The statistical data introduced by the author coincide with data of other authors and con. These relays feature advanced programmable functions which maximize flexibility and monitoring.
Electromechanical and static relays have fixed wiring and the setting is manual. Microprocessorbased distribution relays contribute to improved reliability and reduced costs on electric power systems. Microprocessorbased relays provide technical improvements and cost savings in several ways. B microprocessorbased relays microprocessorbased relays incorporated analogtodigital converter adc to sample the analog signals incoming from instrument transformers, and used microprocessor to define the logic of the relay. Adv ances in microprocessorbased distribution rela vs edmund 0. These refays use algorithms similar in principle to their electromechanica1 counterparts. Moreover they do not interfere with any electronic apparatus near the installation. 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. The results from the evaluation of the relays, combined 11 with the fieldobserved reliability life curve confirm that when relays are manufactured from highquality materials and highquality processes and the effects of aging ar e considered during product design, that microprocessorbased relays can reliably. Electric utilities company of nigeria eucn have traditionally used electromechanical emr distance relays for the protection of transmission lines in the past. There are some advantages of microprocessor are given below. Life cycle considerations for microprocessor relays. It is the goal of this paper to present the reader with some background material and discussions by which they can. The question is whether such high sensitivity and accuracy are really required in relay protection of power units.
The relay can be on or off, that is, it has two stable states. For example, lets take microprocessorbased frequency relays picking up when frequency diverts by 0. Microprocessorbased protective relays applications in. Numerical relays protection and control products for power. Typical electromechanical relay scheme panel layout. Microprocessor based distance relays 19 reactance for the first zone of protection. Relay logic is very important to understand the microprocessorbased relay. Commissioning microprocessor based ied communication. Today we now find ourselves in the 30 year mark for the first generation microprocessor relays.
Advances in microprocessorbased distribution relays. If x is greater than xl but less than x2 it sends the tripping signal after a predetermined delay. Both the mib and pvd have the same high impedance operating principle, with the same limiting criteria of maximum short circuit current calculated from the number of feeders and the calculation of the minimum short circuit. B microprocessor based relays microprocessor based relays incorporated analogtodigital converter adc to sample the analog signals incoming from instrument transformers, and used microprocessor to define the logic of the relay.