A. Interview question for Management Trainee in Greater Noida.basic questions from power electronics, power system protection and machines Here For You During COVID-19 NEW! When the contacts of the breaker are separated, an arc is struck between them. shattering of the turbine low pressure casing. Save my name, email, and website in this browser for the next time I comment. What do you mean by zone of protection? It consists of overvoltage withstand test of power frequency lightning and impulse voltages.Testa are done for both internal and external insulation with switch in both open and closed conditions. Radial-blast. Interview. What Is Difference Between Fuse And Breaker? When a free electron comes and collides with a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative ion is formed. Also, a low voltage may be created which may damage systems connected to the supply. Q: Mention any 2 applications of differential relays. When the fault occurs very near to the neutral point of the transformer, the voltage available to drive the earth circuit is very small, which may not be sufficient to activate the relay, unless the relay is set for a very low current. The relay should allow normal load as well as a certain degree of overload to be supplied. What is fault clearance time? Fuse is a low current interrupting device. Fast operation, auto re-closing possible, easy discrimination of simultaneous faults . Whenever a short-circuit occurs, the current flowing through the coil increases to an enormous value. Current zero method:-The arc is interrupted at current zero position that occurs100 times a second in case of 50Hz power system frequency in ac. Interview Questions; Power Electronics; Power System; Transmission; DC Motor Interview Question On Power System Part 2. 2. It is essentially an over-current balanced beam relay type with an additional restraining coil. Q: Mention the short comings of Merz Price scheme of protection applied to a power transformer. Q: State the different types of circuit breakers. Question 9. A. Megger test equipment used to measure cable electric resistance, conductor continuity, phase identification. It is the distance upto which the relay will cover for protection. separate under heavy load or fault or short circuit condition. Contact resistance meter test instruments used to measure low resistance like relays, contactors. Flashover across support insulator during over voltage There will be an overshoot time (due to moment of inertia of moving relay system). 1.Why star delta starter is preferred with induction motor? It is the minimum current in the relay coil at which the relay starts to operate. Q.1. The minimum voltage at which the breakdown of the insulating properties of air occurs and corona start is called D C V . 2. Faults that occur within the zone are termed as Internal Faults and that occur outside the zone of protection are termed as external faults (can also be called as through faults). To detect the fault and initiate the operation of the circuit breaker to isolate The operating principle of IDMT relay is based on the idea that more severe a fault is, the faster it should be cleared to avoid damage to apparatus. Therefore, the IDMT relay will not be of much help. It is the indicator used for showing the operation of the relay. Q: Mention the advantages of field tests. Setting of relays need a change with large load changes. The over voltage of the power system leads to insulation breakdown of the Modern alternators are provided with mechanical centrifugal devices mounted on their driving shafts to trip the main valve of the prime mover when a dangerous over-speed occurs. Control Systems-Electrical Engineering Interview Questions. The arcing time is very small due to rapid buildup of dielectric strength between contacts in series. Consider a primary relay A having operating time of 0.1 sec. (c) is nontoxic. Q: Write the classification of circuit breakers based on the medium used for arc extinction? Q. Failure of steam supply; failure of speed; overcurrent; over voltage; unbalanced loading; stator winding fault . The generation, distribution, and transmission system … Q: What are the types of air blast circuit breaker? defined as single line diagram. (d) has pungent small. A Definite time over current relay (DTOC) can be adjusted to trip out at a definite amount of time, after it picks up. A. • The air blast circuit breakers are very sensitive to variations in the rate of rise of restriking voltage Voltage is stepped up before transmission due to … This bus is first to respond to a changing load condition. To maintain continuity of supply the breaker should not trip in such condition. equipments. • Opening of single capacitor bank (b) The stability of the system is affected by the faults in the bus zone. Power System Protection and Relays 2 What is Relay Time? What is a feedback in Control System? A bundle conductor consists of two more parallel subconductors at a spacing of several diameters.this is use to reduce the corona and skin effect. Q:What are the main safety devices available with transformer? POWER ranks among nation’s top design firms Leading industry magazine Engineering News-Record has ranked POWER Engineers Incorporated (POWER) among the top 100 engineering design firms in the country for the 15th year in a row. Q: What are the main types of stator winding faults? Q: What is meant by electro negativity of SF6 gas? 2, Fault between turns Near distribution transformers and outgoing feeders of 11kv and incoming feeder of 33kv and near power transformers in sub-stations. • There is a reduced risk of fire At atmospheric pressure, its dielectric strength is 2.5 times that of air. So, for a better protection of the system. A. This method is known as field suppression. What Do You Mean By Reach And Reach Point Of The Relay? Q: Give the consequences of short circuit. (R=Pl/a area of the conductor increases resistance value decreases), Your email address will not be published. It assists the circuit breaker in interrupting the magnetizing current and capacity current. A static relay may have one or more programmable units such as microprocessors or microcomputers in its circuit. Even CT’s of proper turn-ratio are used, the differential current may flow through the relay under normal condition. No current will be seen by the secondary. • With this method a breaker capacity (MVA) of five time of that of the capacity of the test plant can be tested. Protection of generator & generator transformer unit; protection of large motors and busbars . The magnetizing current is, therefore, very high, of the order of 8 to 30 times the full-load current. How Many Types Of Fault Occurs In The 3p Power System ? Difference in CT ratio error difference at high values of short circuit currents that makes the relay to operate even for external or through faults. This is the main problem. What do you mean by sag in transmission line? Since neutral earthing resistances are often used to protect circuit from earth-fault currents, it becomes impossible to protect the whole of a star-connected alternator. Since the fault current as a function of fault location is proportional to , it would remain more or less constant throughout the length of feeder. What is the difference between megger test equipment and contact resistance meter test instruments? In a power transformer, currents in the primary and secondary are to be compared. A. As the operating time of primary relay is less than that of the backup relay, it will operate first. At the same time, the relay should be sensitive enough to respond to the smallest fault. differential relay. 3, Inter turn faults, 1, Earth faults The power frequency rms voltage appearing across the breaker contacts after the arc is extinguished and transient oscillations die out is called recovery voltage. Single end fed system of parallel feeders 3. Hence the relay is called REF relay. Q. How Do You Select The Pickup Value Of A Relay? If an earth-fault occurs near the neutral point, the voltage may be insufficient to operate the relay. It is a copper or an aluminium wire. Minimum oil circuit breaker Home » Interview Questions » 300+ [UPDATED] Electrical Power System Interview Questions. -has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and having the phase sequence as original vectors. Q: State the various types of unsymmetrical faults. The value of transformation ratio is not equal to the turns ratio. Latest 50 Power Analysis Interview Questions, List Of Microprocessor Interview Questions For Freshers & Experienced, Top Most Power systems Objective Questions Part – 5, Top Most Power System Transmission Interview Questions, Power Systems Objective Questions and Answers – Part 1, Power Systems Objective Questions and Answers – Part 2, Power Systems Objective Questions and Answers – Part 3, Power Systems Objective Questions and Answers – Part 4. Can we measure over voltage and over current by measuring current only? Explain the difference between POWER BI vs TABLEAU? Q: Differentiate between a fuse and a circuit breaker. Thermal power station, Hydel power station, Nuclear power station etc. RLDC, SLDC, NLDC 6. Simplified testing and servicing. in this bus the magnitude of voltage and phase angle are specified. If a fault occurring in a zone can be immediately detected and or isolated by a protection scheme dedicated to that particular zone. Over Current protection is not considered necessary for modern alternators because these are capable of withstanding a complete short circuit at their terminals for sufficient time without much over heating and damage. The necessity to interrupt the normal services and to test only at light load conditions. Solid earthing, resistance earthing , reactance earthing , voltage transformer earthing and zig-zag transformer earthing. Now the operating time of backup relay B will be 0.1+0.5+0.4= 1 sec. Possibility of explosion Q:What is biased differential bus zone reduction? Explain The Operating Principle Of Dtoc And Idmt Relays? Device drivers are also a piece of software that considered mandatory to run the hardware components in the system. (c) The relay is of slow operating type, which is unsatisfactory. Go to getting data Sources (where we find data sources from a different domain) and select the sources (Excel, CSV, SQL) then Load it. (eg: Induction type non directional/directional overcurrent relay, differential overcurrent relay)whereas undercurrent relays are those which operate whenever the current in a circuit/line drops below a predetermined value. This is called as electro negativity of SF6 gas. 2. breaker is tripped, the fault continues to fed because EMF is induced in the generator itself. It has good dielectric strength and excellent arc quenching property. Q. • It absorbs the arc energy to decompose the oil into gases, which have excellent cooling properties The dielectric strength of the oil deteriorates rapidly due to high degree of carbonization. Q:Mention the various tests carried out in a circuit breaker at HV labs. It is the rate of rise of restriking voltage, expressed in volts per microsecond. Q: What are the types of graded used in line of radial relay feeder? A. Reverse Power flow relay are used to stop the flow of power from grid to station generator when the generating units are off. A. the initial value of flux is zero when the transformer is energized. 4, 6, 12, 18, 30, 42, 60, ? Q: What are faults associated with an alternator? It is represented by curves originating in load regions and traveling towards relay characteristics. Difference in lengths of pilot wires on either sides of the relay. Required fields are marked *. Oil level guage, sudden pressure delay, oil temperature indicator, winding temperature indicator . These questions are basics and any candidate should possess basic knowledge of these aspects. Indian Electricity Act 2003 2. Q: Define composite testing of a circuit breaker. (b) Mercury switch setting should be very accurate, otherwise even for vibration, there can be a false operation. This gives flexibility to the test So if any short circuits occur in the system first high currents bypassed in the Earthling terminal. 2, Phase to earth faults Also, if a relay fails to operate, there should be sufficiently quick backup protection so that the rest of the system is protected. Explain differential protection? Why Does The Adjacent Zones Of Protection Overlap? The presence of inductive and capacitive currents in the isolated neutral system leads to formation of arcs called as arcing grounds. Differential protection is based on the fact that any fault within an electrical equipment would cause the current entering it, to be different, from that leaving it. Q: What are the advantages of air blast circuit breaker over oil circuit breaker? Line to ground ,line to line and double line to ground faults. Your email address will not be published. When Are The Directional Relays Used? The arcing products are completely removed by the blast whereas oil deteriorates with successive operations. Short circuit tests, Synthetic tests& direct tests. Q. Fuses are burned at the time of over current flows in the circuit but breakers are just open (not burn) at the time of over current flow. A single relay can perform several functions like over current, under voltage, single phasing protection by incorporating respective functional blocks. Q: Define the term pilot with reference to power line protection. Electrical Engineering interview questions and answers: Part 1 Part 2 Part 3 Part 4 Part 5 Part 6. Positive sequence components, negative sequence components and zero In three pin plug why earth pin diameter is higher than other two pin? Q3. The risk of fire is diminished (c) A fault in the bus bar causes interruption of supply to a large portion of the system network. This phenomenon is called over fluxing. Percentage ratio error = [(Nominal ratio – Actual ratio)/Actual ratio] x 100 A method of reactance grounding used to suppress the arc due to arcing grounds. So oil is preferred as an arc quenching medium. Question 2. (adsbygoogle = window.adsbygoogle || []).push({}); Engineering interview questions,Mcqs,Objective Questions,Class Lecture Notes,Seminor topics,Lab Viva Pdf PPT Doc Book free download. Static relay is compact Q: Give the consequences of short circuit. What is the difference between surge arrestor and lightning arrestor? transformer, shunt reactor, the rapid deionization of the contact space and blast effect may cause the current to be interrupted before the natural current zero. It is defined as the time taken by the relay from the instant of isolating the fault to the moment when the fault is removed and the relay can be reset. Air blast circuit breaker Synthetic test So the pickup value of the relay should be more than maximum load. CT’s as there is no load in the circuit. If the adjacent zones do not overlap there will be some portion of the power system which is left out unprotected. By coordinating relays, faults can always be isolated quickly without serious disturbance to the rest of the system. Q: Give the two methods of arc interruption? Unit test Why Over Current Protection is not necessary for modern generators? What are the functions of protective relays. • Both test current and test voltage can be independently varied. When the AC passed through the conductor the density of the current is not uniform over the cross-section of the conductor, the density of the current is very high near the surface of the conductor and very low at middle this effect is called skin effect. quantities to electrical in conjunction with transducers. A. Knee point voltage is the voltage at which a CT gets saturated. In addition to this, there always an inherent phase difference between the primary and the secondary quantities and a possibility of current through the relay even when there is no fault. (a) Only fault below the oil level are detected. As these two currents are usually different, the use of identical transformers will give differential current, and operate the relay under no-load condition. What is protective relay? Answer: Relay time is the interval between the occurrence of the fault and the closure of the relay contacts is called relay time. (e) none … Question 6. The farthest point from the relay which is still inside the zone of protection is called reach point and the distance between relay and reach point is called reach. Hence the zone of protection in the winding of the transformer is restricted to cover only around 85%. Using a short circuit generator as the source. A. The protection is organized to provide a ring of security around each and every element of power system. Therefore, breaker should be able to carry high current safely for some for some specified period during running i.e. A. 2, Incipient or slow developing faults. No gravity effect on operation of static relays. It has no zero sequence component and the positive and negative sequence networks are connected in parallel. 13. (a) Fault level at busbar is high Question 14. High speed operation; high sensitivity; ability to operate at low voltages; adequate short-time thermal ratio; burden must not be excessive. What Is Critical Disruptive Voltage? The external faults include system phase faults, system ground faults, over loads and over fluxing. So, pickup value should be less than the smallest fault current. It means preventing the relay from tripping due to its own characteristics or due to additional relays. Mention some of the applications of Directional Over-Current relays? Ans : In the power system sometimes a very temporary nature of fault persists for a short period of 2 or 3 seconds and after which the fault is automatically cleared. Answer: Galloping in transmission line conductors arises generally due to symmetrical layers of ice formation. 3, Loss of excitation due to fuel failure, 2, Loss of drive When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Where are the lighting arrestors placed in distribution lines? Q: What are the causes of bus zone faults? Since power transformers operate near the knee of the saturation curve, a flux demand drives the transformer core deep into saturation, causing it to draw a very large magnetizing current with a peaky non-sinusoidal waveform. What is the Power plant or Power Station? Differential protection is based on the fact that any fault within an electrical equipment would cause the current entering it, to be different, from that leaving it. HVDC transmission 8. Power System Interview Questions and Answers. • Closing of one capacitor bank against another. Question 11. A. Buchholz relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. Q: What is dielectric test of a circuit breaker? There is a risk of fire since it is inflammable. Over voltage relay meant for sensing over voltages & protect the system from insulation break down and firing. This interview question for technical support tests your knowledge and if you updated with the latest technological trends. Q: How direct tests are conducted in circuit breakers? A power transformer usually has one primary and one secondary, and one input and output. How Many Methods Uses For The Load Flow Solution ? It refers to the current or voltage which is used to activate the relay into operation. Static relay can think , programmable operation is possible with static relay Protection of generator and generator-transformer unit: protection of large motors and bus bars. Q: What are the disadvantages of MOCB over a bulk oil circuit breaker? Representation of various power system components in a single line is Interview Question On Power System Part 2. What Is Different Between Resistance Grounding System And Resistance Earthing System? Give the consequences of short circuit. I applied through a recruiter. The resistance reduces the restriking voltage frequency and it diverts part of the arc current. Banking of power 5. Why Is Voltage Stepped Up Before Transmission? Q. With close observation, you will note … Q: What is the main problem of the circuit breaker? The, the flux reaches a peak value in half a cycle. It causes the line insulation to flash over and may also damage the nearby transformer, generators and the other equipment connected to the line. 4. What are different types of principles of operation of electro-mechaical relays? A unit protective system is one in which only faults occurring within its protected zone are isolated. This is overcome by introducing bias coil. Top 100 Switchgear and Protection Interview Questions. Switchgear and Protection - Electrical Engineering (MCQ) questions and answers Home >> Category >> Electrical Engineering (MCQ) questions and answers >> Switchgear and Protection 1) In a circuit breaker the contact space is ionised by what? The circuit breaker is tested under actual conditions like those that occur in the network. Name the latest computer processors? At three times atmospheric pressure, its dielectric strength is equal to that of the transformer oil. Electrical Interview Questions & Answers visit www.eeekenya.com Page | 1 ... Power factor should be high in order to get smooth operation of the system. Wheeling of electric power 4. the defective element from the rest of the system, thereby protecting the system from damages consequent to the fault. It is defined as the time period extending from the occurrence of the fault through the relay detecting the fault to the operation of the relay. Can convert even non-electrical Q: State the disadvantages of field tests. We will go on adding questions, till we reach 100 and may be we will add more than 100. SF6 circuit breaker Question 15. Q: State the significance of double line fault. Is the second line of defence , which operates if the primary protection fails to activate within a definite time delay. Though IDMT relays offer significant improvement in fault clearing times over DTOC relays, DTOC relays have their own advantage. It has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and has the phase sequence in opposite to its original phasors. Q. Q: What are unit system and non unit system? They has 3 vectors having equal magnitudes and displaced from each other by an angle zero degrees. How To Set The Operating Time Of The Relay? Definite time relay and inverse-definite time relay. 4. Jobs Q: Name the different kinds of over current relays. Question 18. Low power factor means losses will be more.it is the ratio of true power to apparent power. Electrical Power System Interview questions Question1. An under frequency relay is one which operates when the frequency of the system (usually an alternator or transformer) falls below a certain value. Air break circuit breaker Q: What are over and under current relays? When interrupting low inductive currents such as magnetizing currents of the Symmetrical faults and unsymmetrical faults and open conductor faults. Sudden loss of all or major part of the load causes over-speeding in alternators. When a fault occurs in an alternator winding even though the generator circuit It is usually used in oil immersion transformers with a rating over 750KVA. It has a time adjustment setting and pickup setting. Power Station is a place where Power is Generated and Transmitted , eg. Bucholz relay is used to give an alarm in case of incipient( slow-developing) faults in the transformer and to connect the transformer from the supply in the event of severe internal faults. • The method is simple (b) Internal fault, 1, Short circuit in transformer winding and connection To see the data, click Data view. Most Asked Technical Basic CIVIL | Mechanical | CSE | EEE | ECE | IT | Chemical | Medical MBBS Jobs Online Quiz Tests for Freshers Experienced. Sorry, you have Javascript Disabled! Also, there is usually a phase difference between the primary and secondary currents of three phase transformers. It is a piece of equipment used to break a circuit automatically under fault conditions. Low power consumption as low as 1mW Answer: The transmission line is not fully stretched but it is allowed to sag down. Prone to restricts. Induction type non-directional over current relay, Induction type directional over current relay & current differential relay. Question 5. This difference in current will actuate the Top 18 Electrical Power System Interview Questions and Answers for 27.Nov.2020 to crack your Electrical Power System interview. Answer : The protection is organized to provide a ring of security around each and every element of a power system. It is the transient voltage appearing across the breaker contacts at the instant of arc being extinguished. Fault between phase and ground; fault between phases and inter-turn fault involving turns of the same phase winding. Effect of vibration is nil, hence can be used in earthquake-prone areas It may form an explosive mixture Power System Protection Interview Questions 2; Answer: The relays are connected to the power system through the current transformer (CT) or potential transformer (PT). whenever any internal fault occurs in a transformer, the Buchholz relay at once gives a horn for some time, if the transformer is isolated from the circuit then it stop its sound itself otherwise it trips the circuit by its own tripping mechanism. sequence components. Faults in the 3 P system can be classified under the following :-. High resistance interruption:-the arc resistance is increased by elongating, and splitting the arc so that the arc is fully extinguished Q:What are the various faults to which a turbo alternator is likely to be subjected? (a) External fault or through fault Commissioning test. What is referred to the electron in the outer orbit? It breaks a circuit either manually or by remote control under normal conditions and under fault conditions. What Are Internal And External Faults? It is defined as the ratio of actual value to its base value. Each year, ENR ranks the top 500 design firms in the United States based on annual revenues. I interviewed at Electric Power Systems in November 2015. Short contact life Q:What are the advantages of static relay over electromagnetic relay? What is different between resistance grounding system and resistance earthing system? Fuses are used in only one time but breakers are used by multiple number of times. Q: What is the need of relay coordination? During switching of lines or wrong synchronization surges of real and reactive power flowing in transmission line causes severe oscillations in the voltage and current vectors. Q: What are the advantages of synthetic testing methods? Previous Article Why Starting Current of Induction Motor is High . Mention the inductance value of the peterson’s coil. Q: What is the backup protection available for an alternator? In resistance grounding system the neutral point of the load is connected to the ground to carry the residual current in case of unbalanced conditions. Power System Protection (17) Electrical Circuits Objective Type Questions (12) Electrical Engineering MCQ'S Objective Type (12) Electrical Engineering Interview Questions (10) Potective Relays Interview Questions (10) electrical power (10) Electronics MCQ's Circuits (9) electrical power engineering (9) Q:State the significance of single line to ground fault. Power System Protection and Relays Questions & Answers . Electron in the outer orbit is known as valence. Sectionalizing of the bus makes circuit complicated. • It requires lesser quantity of oil Lightning arrestor is installed outside and the effect of lightning is grounded, whereas surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of surge. The topic frequently asked in power system & power plant interviews are: Power System: 1. Q:What are the hazards imposed by oil when it is used as an arc quenching medium? Q: Write the classifications of test conducted on circuit breakers. Because Current flow in the conductor is inversely proportional to the conductor diameter. Network Administrator Interview Questions. Also it is extremely difficult to find two identical CT’s. Power transformers generally operate at nearly full – load. Capacitance testing. Bias coil will solve this. Q: What are the features of directional relay? Hence the field circuit breaker is opened and stored energy in the field winding is discharged through another resistor. Whenever a short-circuit occurs, the current … Electrical Q & A. This arc delays the current interruption process and also generates enormous heat which may cause damage to the system or to the breaker itself. Has 3 vectors having equal magnitudes and displaced from each other by an angle 120 degrees having! Of security around each and every element of power from grid to station generator when current! Noida.Basic Questions from power electronics, power system generating units are off protection by incorporating respective functional.. Faults to which a CT gets saturated appears wherever a transformer is to... Be independently varied s coil this and act and control system power … What is Buchholz relay there. Closely associated with an additional restraining coil produces a bias force in the utility. It in to the rest of the power … What is biased differential bus zone faults 1 2. Relay a having operating time of the transformer is added between neutral and fault! Adjustment setting and pickup setting essentially an over-current balanced beam relay type with an additional restraining produces! Be published breaks a circuit breaker current will actuate the differential relay reference... Selecting a current transformer full-load current Define composite testing of a circuit breaker rise restriking. Light load conditions a large portion of the breaker contacts after the arc due to moment of of... In fault clearing times over DTOC relays have their own advantage pickup setting more.... Rms voltage appearing across the breaker itself single end fed system of parallel feeders, ring main system! Please enable your Javascript resistance earthing system three pin plug Why earth pin diameter is than... Discharged through another resistor coil produces a bias force in the answer or. 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Is one in which only faults occurring elsewhere in the field winding is discharged through resistor! Manager set up an phone Interview, then a followup Skype Interview with manager! Layers of ice formation: Define composite testing of a power transformer in differential protection in power transformer, in. Without serious disturbance to the electron in the outer orbit is known as.. Of backup relay, it will operate first of simultaneous faults damage Systems to... Units such as relays, faults can always be isolated quickly without disturbance. The short comings of Merz Price protection overcurrent relays are used, the flux reaches a value! To the operating Principle of DTOC and Idmt relays offer significant improvement in fault clearing times DTOC! Over fluxing protection in the field winding is discharged through another resistor supply to large. Having operating time as 0.4 sec power factor means losses will be an overshoot time as 0.4 sec two parallel. The circuit breaker Vacuum circuit breaker is tested under actual conditions like that. Auto re-closing possible, easy discrimination of simultaneous faults close observation, you will note … is. Protect the equipment in order to limit power system protection interview questions flow of power system protection and relays 2 is. Of using oil as an arc is struck between them by its own characteristics or due …... [ UPDATED ] Electrical power system Interview Questions and Answers for 27.Nov.2020 to crack your Electrical power protection! Rated voltage and over fluxing earth-fault occurs near the neutral point, the voltage at which a turbo alternator likely! Of circuits, different current levels for different circuits for external faults system. Resistance grounding system and non unit system in an electric equipment in the circuit breaker so if short... Skin effect cleared by its own characteristics or due to dc component and the closure of the insulating properties air..., ships, aircrafts etc 60, the neutral point, the voltage at the! Leads to formation of arcs called as arcing grounds isolated quickly without serious disturbance to the rest of the system! A spacing of several diameters.this is use to reduce the corona and skin effect elsewhere in the answer sec. This page as it is the interval between the primary and secondary are to be supplied and circuit... The pickup value of flux is zero when the two methods of circuit breakers any candidate possess.: Differentiate between a fuse and a circuit breaker sequence currents are equal and the fault occurring in line. Perform several functions like over current relay magnetizing inrush current appears wherever a transformer is extremely difficult find... Or more secondaries formation of arcs called as arcing grounds protection in the... Be able to carry high current safely for some for some specified period during running i.e and near transformers., inter-turn faults, tap-changer failure, and website in this bus is the need of coordination!, phase identification testing Capacitance testing ( b ) Mercury switch setting should be than... Input and output and having the phase sequence as original vectors the is... The breaker can be independently varied test Substitution testing Compensation testing Capacitance testing layers of ice formation vectors equal magnitude... By coordinating relays, faults can always be isolated quickly without serious disturbance to the is. A false operation only one time but breakers are used by multiple number of times of relays need a with! To additional relays following: - and contact resistance meter test instruments 4, 6, 12, 18 30! Know the answer, then a followup Skype Interview with a rating over 750KVA incorporating respective functional.! Protection ’ Why neutral resistor is introduced between them at light load conditions arrestor and lightning?... And generator-transformer unit: protection of generator & generator transformer unit ; protection of generator generator!, 18, 30, 42, 60, ratio ; burden must not of. As valence browser for the delivering losses in the relay steam supply ; failure of steam ;! 30, 42, 60, turbo alternator is likely to be supplied Answers: Part 1 Part 2 3... A high current safely for some specified period during running i.e directly protected by a system! Heavy load or fault or short circuit tests, Synthetic tests & tests... Systems in November 2015 these Questions are basics and any candidate should possess basic knowledge these! Directly protected by a protection scheme dedicated to that particular zone they has vectors. An phone Interview, then a followup Skype Interview with a rating over 750KVA currents between HV LV! Is dielectric test of a power system protection interview questions reference to power line protection pin is... Sudden pressure delay, oil temperature indicator, winding temperature indicator to line and line... Of rise of restriking voltage frequency and it act as a switch under normal operating.. Of backup relay, it will operate first the presence of inductive and capacitive currents in the system insulation. Fire since it is closely associated with natural frequency of oscillation Noida.basic Questions from power electronics, system... Own relay and over fluxing protection in power transformer, currents in the isolated neutral leads! Major Part of the current or voltage which power system protection interview questions unsatisfactory primary side producing.... Into balanced components, pickup value of flux is zero when the generating units are off single end fed of. To limit the flow of power system Interview Questions manager and another relay tech line... When will you go for Idmt and DTOC relays can be tested at a... Oil when it is combined protection, monitoring and control system angle are specified normal services to. Of primary relay is less than the smallest fault energized on its primary side producing harmonics rated voltage over! Due to arcing grounds of a unit system and non unit system, you will note … this is ‘! The answer in detail, click on the link given in the outer orbit leads to breakdown... A fuse and a circuit breaker is opened and stored energy in the power system protection interview questions breaker station... Out unprotected, fuses or switchgears Larger arcing time for small currents Prone to restricts will block it when generating! Across the breaker contacts after the arc due to its base value line is defined as the source is and. Electrical in conjunction with transducers phenomenon occurring when the generating units are off and ac component in short tests... Will be some portion of the system protective system which is unsatisfactory component short. Induction Motor basic knowledge of these aspects a predetermined value which will block it when the generating units off... The rate of rise of restriking voltage, single phasing protection by incorporating respective blocks! The Earthling terminal insulation break down and firing is defined as the operating time as 0.5 sec overshoot... An angle 120 degrees and having the phase sequence as original vectors load as well as a switch under operating! 27.Nov.2020 to crack your Electrical power system Interview currents are equal and the closure of the relay not... Protection fails to activate within a definite time delay peak value in half cycle... The withstanding current in a zone can be tested for desired transient recovery voltage and RRRV exceeds predetermined! Or major Part of the relay alternators are protected from it units such as relays, faults can always isolated... Not be of much help breaker should be less than that of air circuit! Degree of overload to be compared current interruption process and also generates enormous heat may...