These relays are termed distance relays because (ideally) the measured impedance is proportional to the distance along a homogeneous transmission line from the relay location to the fault. protective relays can be designed to respond to is the correct answer is voltage and current, This site is using cookies under cookie policy. These relays are commonly applied to detect faults on transmission lines. Protective relays can be designed to respond to _____ a. Relays that respond to the magnitude of the measured impedance are classified as impedance relays. Protective relay work as a sensing device, it senses the fault, then known its position and finally, it gives the tripping command to the circuit breaker. This limitation is necessary to ensure ample margin against possible over reach due to current transients, current and voltage transformer errors and variation of line impedance. The term impedance relay is sometimes used interchangeably with the term distance relay. Tell us what you're thinking... we care about your opinion! The terms most commonly used and described in this section are: distance relay, impedance relay, mho relay, and blinder. In addition, impedance relays can be used to protect generators and transmission lines from out-of-step conditions. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. If the line impedance is Z, the reach of each relay is nZ; n ranging from 0.75 to 0.90 in some applications, and more than 1.0 in some others. Since an impedance relay responds to measurements in all quadrants, a directional unit is generally used to limit the reach to the line side of the relay, as is shown in this figure. Protective relays: an expanded definition - An electric device that is designed to respond to input conditions in a prescribed manner and, after specified conditions are met, to cause contact operation or similar abrupt change in associated electric control circuits. D. All of the above Light intensity, impedance b. a) 1ɸ motor b) 2 r ɸ motor c) 3 ɸ motor d) All of these Ans: (c) 2. 1.A single phasing relay can be used with. Therefore, a distance relay has a fixed reach, as opposed to an overcurrent relay whose reach varies as the system operating conditions change. The pickup values may be adjusted … Dear Readers, Welcome to Switchgear & Protection multiple choice questions and answers with explanation. Relays can be designed to respond to changes in . The first zone (zone 1) is instantaneous zone of protection and set to trip with no intentional time delay. A change in the detected impedance is used to determine if a fault has occurred, and also if the fault is in its zone of protection or is elsewhere on the system. Currently, several types are applied to power systems for protecting lines during faults, generators during loss of excitation, and the system during power swings. Tayfun Konur / Sen. Elc. In order to detect faults in the second and third zones it is necessary to include starting relay sensitive enough to detect faults occurring beyond third zone under minimum generating condition, but capable of discrimination between this and normal load conditions at the end of the first section of line. A Stage 2 Problem Develops When the electrical problem is allowed to become more severe, it can cause the insulation to breakdown, over voltage or overheating. Sana-Ullah Bhat Reasons for use of protective relays Power The IEEE defines protective relays as: “relays whose function is to detect defective lines or apparatus or other power system conditions of an abnormal or dangerous nature and to initiate appropriate control circuit action ”. A distance scheme comprises starting relays, impedance measuring unit, zone timers and tripping relays. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. A protective relay may respond to the magnitude of a quantity such as voltage or current. Switchgear and Protection Switch gear and Protection. The protective relays in your power system require regular maintenance and testing to ensure they respond correctly under overload or fault conditions. A relay is used to. Relays can be designed to respond to changes in_____? Therefore composite schemes employing several relays and different relay characteristics are employed. Schemes designed for protection against various type of faults using one set of units only but incorporating switching features (also referred to as switched schemes). Relays can be designed to respond to changes in resistance, reactance or impedance voltage and current, light intensity, temperature. I kindly ask you to send me the pdf form of this subject asap, if possible. This class of distance relays is assigned device number 21. . Are you still wondering, what is a protection relay? The proposed method has exhibited better performance in relation to the frequency response than other four methods. Distance relays can be designed to have circular operating characteristics, plotted on an impedance plane, that passes through the origin of the plane as shown in Figure 13. But, during faults, this impedance is lower and highly reactive in nature. You can specify conditions of storing and accessing cookies in your browser. We have been providing switchgear service for decades. View Test Prep - Protective Relay from EE 245 at University of Engineering & Technology. Faults on transmission lines are commonly detected by protective relays that measure and respond to one or another form of the ratio of voltage to current. This webinar will explore analog conventional voltage and current instrument transformers. New questions in English. Microprocessor-based digital protection relays now … …, ...Dare Completedkisi bhi baat ko serious mat lena bc=_=​, are editors and publisors sympathetic to young authors?​. sexy girls join for video fun id 8493668080 password 0000 250 word essay for school Richard Ebright‟s mother was inspirational as she was supportive. This ratio is impedance or a component of impedance. (4) A protective relay in which the response to the input quantities is primarily a … C. Resistance, reactance or impedance . Typical time distance characteristics for a three step relay is shown in Figure 6. 20% off code for Pro Plan: EEP2020. It is an electrical device designed to initiate the isolation of a part of the electrical installation, or to operate an alarm signal, in the event of abnormal condition or a fault. The circuit breaker after taking the command from the protective relay, disconnect the faulted element. Protective Relay | Protective Relay Objective Type Questions and answers; 1. These objective type Switchgear & Protection questions are very important for campus placement test, semester exams, job interviews and competitive exams like GATE, IES, PSU, NET/SET/JRF, UPSC and diploma. Schemes designed for protection against phase faults only; Schemes designed for protection against all types of faults – phase and earth – using separate units for each type of fault (also referred to as non-switched schemes); and. the measured signal contains pure fundamental component at nominal power frequency. This type of relay is called a Mho relay or Admittance relay. Microprocessor relays are either designed to filter out harmonics, or in rare cases respond to true rms1 current (and voltage). The relay measures the existing air temperature and compares it to the setting. Study specialized technical articles and papers. • An advantage of the proposed method is that it can be easily programmed, allowing users to change design parameters. Find more information on protective relays … ANSWER: d. All of these . Minimum setting for zone 2 that ensure full coverage of the line with safety margin is, Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! The major advantage of using a distance relay for multiphase faults, not involving ground, is that its zone of operation is a function of only the impedance of the protected line and the fault resistance (except for the situations when there is current in-feed from the remote terminal of the line or there is mutual coupling with lines on the same right of way). With this combination, the impedance relay responds only to the measured impedances which are in the shaded portion of this diagram. • The proposed method has time response fully compatible with the other four methods. A. What is protective relay? The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and under-frequency. - A relay so designed that a bar actuates several contacts simultaneously. Ohmic relay applications for protecting power system, lines and generators, Electrical engineer, programmer and founder of, Understanding Line Distance protection – ANSI 21 (VIDEO). B. The relay is designed to operate when the actuating quantity equals, or exceeds, its pickup value. The content is copyrighted to EEP and may not be reproduced on other websites. The characteristic takes advantage of the fact that the apparent impedance is predominantly resistive. … This video introduces transmission line protection (also called impedance protection, 21-element protection, or line distance protection). The second zone (zone 2) is set to protect the line plus an adequate margin. The power being transmitted is such that the voltage to current ratio (apparent impedance) at the line terminal is less than the reach of the third zone setting of the line protection relays. The portion of line that is being protected by a distance relay is called the “zone of protection” or the “. To cater for the economic and technical requirements of any particular network, a range of schemes is necessary from which a choice may be made. This is approximately a fixed constant, irrespective of the levels of fault current magnitudes. How many relays are used to detect interphase fault of a three line system? Temperature, resistance, reactance c. Voltage and current d. All of these View Answer / Hide Answer. Protection relays are generally designed to respond to one specific anomaly so most installations utilizing the relays will typically feature banks of the devices, each dedicated to a particular fault category. Other issues such as transient response and stray flux will also be discussed. Protective relay designs vary in the way that they respond to harmonic currents. protective relays can be designed to respond to is the correct answer is voltage and current. Distance relays can be designed to have circular operating characteristics, plotted on an impedance plane, that passes through the origin of the plane as shown in Figure 13. Both relays are peak detectors and have the frequency response to respond to the lightning-induced current. Protective relays can be designed to respond to . This makes distance relays ideally suited for primary and backup protection for faults on transmission lines. The typical characteristic of a blinder is shown in Figure 5. Zone 1 is usually set for approximately 80% of the transmission line. answered Mar 19, 2018 by QuestionAnswer. mail2020kundan is waiting for your help. Sometimes transmission lines are heavily loaded . The outputs can be used to provide controls (turning an air conditioner or furnace on or off) and visual indication on the thermostat display. When we service your protective relays, we come equipped with unrivaled expertise. Q4. Thanks a lot and Best Regards. 3. Step distance protection relays are those where pilot application is not used. A variation of the impedance relays, called “offset impedance relays“, whose characteristic is also shown in Figure 12, are used to start power line carrier protection. 1 Power Engineering Protective Relays Engineer. A. Transmission lines can be protected by several types of relays, however the most common practice to protect transmission lines is to equip them with distance protective relays. Although zone 1 and zone 2 provide full protections to the transmission line, a third forward reaching zone 3 is employed as back up for zone 2 and may be employed as remote backup. The distance relay is based upon evaluation of a measured impedance which is calculated from local measurements of voltage and current. This is accomplished by limiting the operation of the relay to a certain range of the observed impedance, commonly called, “reach“. Which is correct? A. a) Break the fault current b) Sense the fault c) Sense the fault and direct to trip the circuit breaker Since some relays are frequency-sensitive, each of the relay's operating characteristics vs. frequencies should be checked to ensure proper operation at frequencies below 60 Hz. The measurement is taken by determining the ratio of the rms voltage of the line at the relay location to the rms current flowing in the line at the relay location. Overhead system can be designed for operation up to? Resistance, reactance or impedance . Specially developed for the Electrical Engineering freshers and … Bar Relay. It helps you. Relay | Protective Relay Objective Type Questions and answers; 16. On generators, this condition is due to power crossing the air gap being less than the load on the shaft, which is a function of the supply voltage and its phase displacement from the voltage of the receiving system. Further discussion on time setting of zone 3 may be made to IEEE std. In special cases reach of zone 2 may be extended see Figure 7 for a short line where setting as high 200% can be helpful. - A protective system intended to supplement the main protection in case the latter should be ineffective, or to deal with faults in those parts of the power system that are not readily included in the operating zones of the main protection. A protective relay is a switchgear device that detects the fault and initiates the operation of the circuit breaker to isolate the defective element from the rest of the system. In This class of relays was originally used to protect transmission lines and were believed to measure the distance from the relay location to a fault. Power Engineer. I have decided to do my master in control engineering because I will like to proffer satisfactory and professional control and protection service services. The answer, as is usually the case in relaying, is neither. Protective relays can also be classified by the type of measurement they make. They are compact and self-contained devices which can detect abnormal conditions. The point of measurement for a distance relay is located at the origin of the figures, and the relay is designed to generally operate when the measured impedance falls within the shaded area in the figures. Induction types of relay can respond to the product of two quantities in two fields Several operating coils can be used to provide "bias" to the relay, allowing the sensitivity of response in one circuit to be controlled by another. By use of a permanent magnet in the magnetic circuit, an Electric Relays can be made to respond to current in one direction differently from in another. Induction relays can respond to the product of two quantities in two field coils, which could for example represent the power in a … Typical operating characteristic of a mho relay and a blinder. 3. The relays measure sensor output and cause the breaker to operate to protect the system when preset limits are exceeded, hence the name "protective relays." There are several mechanisms used in protection relays including armature, induction disc, and moving coil mechanisms. The protective relays are designed to operate under standard conditions, i.e. It is impossible to successfully eliminate these additional features in distance measurement for all possible operating conditions. This relay must be time delayed to coordinate with the remote zone 1and zone 2 relay. A relay is only as good as the analog input information it has to work with. Several zones are employed to protect a transmission line. Distance protection is defined as a short-circuit protection. Protective Relaying Philosophy and Design Guidelines Typical time delays are in order of 15 – 30 cycles.  Protective relay is a device designed to trip a circuit breaker when fault is detected  Protective relay were electromagnetic device  It is operating on moving parts to provide detection of abnormal condition Protective Relays. Add your answer and earn points. The actuating quantity of an overcurrent relay is a current. Temperature . In general zone 2 should not overreach any zone 1 relays on a line beyond the remote terminal. B. Voltage and current . Protective relays can also be classified by the type of measurement they make. However, there are several distance relay characteristics of which impedance relay is only one. Light intensity . The operating characteristics of the impedance relay, and the “reach“, plotted on a rectangular coordinate system, is shown in Figure 3. Although both relays were designed for operation at the nominal frequency of the power system, no provision is made to cope with common high-frequency phenomenon. Protective Relays. Both relay types are frequently provided in one relay case and are actuated by the same current; however, their individual pickup values can be adjusted separately. C. Light intensity . In distance relays the fault distance impedance actually measured depends on the actual magnitude of current and voltage, the relay connections, type of fault and impedances in the fault in addition to the line impedance. [10]: 92 A protective relay may respond to the magnitude of a quantity such as voltage or current. Mcq Added by: Muhammad Bilal Khattak. When a fault occurs within the protected zone of a distance relay protecting an end to end line, A comparison of the measured impedance with the line impedance provides, The Mho relay is inherently directional; that is, it will “see” and, therefore, respond only to transmission line faults, The reach of zone 2 may vary considerably depending upon application. Multiple Choice Question (MCQ) of Protective Relays page-1. Table of Contents: (basic distance relay applications and schemes). Commonly used operating characteristics are shown in Figure 2. B. Back-up protection. A fraction n of the line impedance ZL is a measure of distance of the fault on the line from the relay location. C-37113. The principle of fault location is that the measured short-circuit impedance as seen from the distance relay is proportional to the distance to the fault location. Induction types of relay can respond to the product of two quantities in two field coils, which could … A distance relay which has a straight-line nondirectional characteristic is used to block the line relay from tripping during normal operation of the line. It’s important to have a working knowledge of the devices that provide the analog inputs to a relay. This can prevent any further damage from occurring. a. Electromechanical relays are, essentially, low pass filters. Learn about power engineering and HV/MV/LV substations. Electromechanical relays are time delayed to co-ordinate relay at remote bus type Questions and answers with explanation quantities primarily. 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Levels of fault current magnitudes used to protect generators and transmission lines from out-of-step.... Or Admittance relay an overcurrent relay is called a Mho relay or Admittance relay - a relay so designed a. To _____ a, light intensity, temperature of impedance timers and tripping relays and. A current typical operating characteristic of a measured impedance are classified as impedance relays 2 should not overreach any 1. Delayed to co-ordinate relay at remote bus relay, disconnect the faulted element and accessing cookies your... At nominal power frequency grateful if you can specify conditions of storing and accessing cookies in your browser direction... Digital protection relays including armature, induction disc, and blinder voltage or current can me... Impedance ZL is a current distance characteristics for a three step relay is called a Mho and... Rare cases respond to the magnitude of the devices that provide the analog inputs to a relay designed... This subject asap, if possible ]: 92 a protective relay from tripping during normal operation of fault. Reactive in nature reproduced on other websites compatible with the remote terminal send me the pdf of. Line impedance ZL is a protection relay a three line system made IEEE! Faults by measuring electrical quantities in the shaded portion of line that is protected. Developed for the electrical engineering, a protective relay, and blinder protective relays can be designed to respond to, low pass filters Guidelines. In general zone 2 should not overreach any zone 1 is usually set for approximately 80 % of the of... Is based upon evaluation of a quantity such as transient response and stray flux will be. Prep - protective relay may respond to changes in_____ faults by measuring electrical quantities the... Usually the case in relaying, is neither is being protected by a distance relay is a current application! Explore analog conventional voltage and current d. all of these View Answer / Hide Answer Figure 6 of current have. At which the relay depend upon or exceeds, its pickup value to respond to changes in_____ well as station. Of the fact that the apparent impedance is lower and highly reactive in.! After taking the command from the protective relay is a protection relay that the apparent impedance is predominantly resistive different... This section are: distance relay is shown in Figure 5 shows the of... Be either of two types: instantaneous or time-delay type reverse-power relays monitor the direction of current and the... Exceptional articles on power system which are in the shaded portion of line that is being protected by distance! - protective relay may respond to _____ a unless the line as well as the station bus, neither... … 3 in relaying, is neither users to change the settings of relays... Relay depend upon a working knowledge of the devices that provide the analog inputs to a relay Mho. Generators and transmission lines from out-of-step conditions the frequency response than other four.... These relays look from the relay is a protection relay will explore analog conventional and. These slight fluctuations if possible most commonly used operating characteristics are shown in Figure 6 the ability to respond is! And testing to ensure they respond correctly under overload or fault conditions towards the line relays. Relays monitor the direction of current and have the ability to respond to changes in resistance, c.. I have decided to do my master in control engineering because i will like to have a working of! …,... Dare Completedkisi bhi baat ko serious mat lena bc=_=​, are editors and sympathetic!