All Rights Reserved. Balanced faults occur infrequently, but they are serious due to heavy fault levels. In practice, it is observed that the power lines and the communication lines run along the same path. Thus with its high torque/inertia ratio, it is quite suitable for higher speeds of operation. The arrester must, after discharge, cease to catty any current, i.e., it must seal-in itself. The protection element covers one or more components of the power system, such as electrical machines, lines, and busbars. To keep costs down, passive components were generally used wherever possible. The connection diagrams of symmetrical faults are shown in Fig. Load flow, short-circuit and stability. However, when lightning, which is a very high voltage, strikes a power line, it causes conduction from line to ground. Show Explanation Insulation Co-ordination Definition: Insulation coordination is the process of knowing the insulation levels of the power system components.In other words, it is the process of determining the insulation strength of the equipment. Which of the following statement is true? Ques.52. The schematic arrangement of an induction cup structure is shown in Fig. And therefore, extensive calculations required for these studies led to the design of the special purpose analog computer, called a.c. network analyzer sometimes in the year 1929. The moving iron is a hollow metal cylinder or cup, which turns on its axis. The surge absorber is a protective device which can reduce the steepness of wavefront of a surge and absorbs energy contained in travailing wave. Back-up protection is installed to operate when, for whatever reason, the primary protection does not work. Multiple Choice Question (MCQ) of Electronics page-17:241. Back-up protection is installed to operate when, for whatever reason, the primary protection does not work. After testing the insulation resistance of installation to earth, the insulation resistance between line and neutral should be measured. “if the power line is running along the same route as the communication line, there will be interference in (iii) All other fuses in their position. Myelin sheath in neurons provides insulation to axon. Explanation:- Thus to reduce the steepness of wavefront of the surge, surge absorber is used. Basic Insulation Level Definition When lightning impulse over voltage appears in the system, it is discharged through surge protecting devices before the equipments of the system gets damaged. The parallel run between the telephone line and the power line is avoided. (iv) All lamps must be put in the on position. However, it need not be more than 1 MΩ. Its parasitic torques due to current or voltage alone are small. Instead of using overhead telephone wires, underground telephone cables may be used The symmetrical faults are often known as balanced faults. However, this does not imply that they all have to operate for the same fault, and it should be noted that the primary protection for one item of system equipment might not necessarily be installed at the same location as the system equipment; in some cases, it can be sited in an adjacent substation. Principle of HVDC Transmission 3. In the case of balanced faults, all three transmission lines are affected equally, and the system remains in the balanced condition. The path from line to ground is of high resistance that it is normally open. Cheap paper writing service provides high-quality essays for affordable prices. 43. a) The saturation voltage V CF of silicon transistor is more than germanium transistor. Cheap essay writing sercice. To reduce the e.m.f. Insulation resistance of the installation to earth is measured by a megger generating dc voltage of about 500 V. Insulation resistance is measured under the following conditions. The connection diagrams of different types of unsymmetrical faults are shown in Fig. Answer.4. These AC network analyzers for calculating boards) differed from the DC network analyzers in that the resistance components were replaced by a combination of resistance, capacitance, and inductance components. www.gtu-mcq.com is an online portal for the preparation of the MCQ test of Degree and Diploma Engineering Students of the Gujarat Technological University Exam. A stationary iron core is placed inside the rotating cup to decrease the air gap without increasing inertia. In such an arrangement every fault that might occur must involve a connection between a conductor and an earthed metal. The internal and external insulation of the electrical equipment is exposed to continuous normal voltage and temporary abnormal voltage. *. As per the Indian electricity rules, the leakage current of installation should not exceed 1/5000 of the maximum supply demand of the consumer. More than 90 % of faults occur in a power system are the single line to ground faults. A short circuit occurs when two points at different potentials are connected either with zero resistance (a dead short circuit) or with a substance of low resistance (a simple short circuit). However, the electrostatic effect induces a voltage in the communication line, which may be dangerous in handling the telephone receiver. The highest value of the applied voltage at which an arrester will not flash is the withstand voltage. Effect of Transposition:- The purpose of transposition is to balance the capacitances of the line, so that the electrostatically induced voltages balance out in the length of a complete set of transposition, and this length is called a barrel. These types of faults are rare in the power system, and it contributes 2 % to 5 % of the total fault. Ques.56. Induction cup relay is operated due to changes in. However, this does not imply that they all have to operate for the same fault, and it should be noted that the primary protection for one item of system equipment might not necessarily be installed at the same location as the system equipment; in some cases, it can be sited in an adjacent substation. As such the insulation resistance of the complete installation to earth should not be less than 1 MΩ. Whether you are looking for essay, coursework, research, or term paper help, or with any other assignments, it is no problem for us. Answer.2. It closely resembles an induction motor except for rotor iron is stationary, only the rotor conductor portion being free to rotate. Faults are divided into two types: The lightning arresters have basically surged diverters. Explanation:- Answer.1. Primary protection should operate every time an element detects a fault on the power system. Any of these Thus, voltage surges are conducted to the ground before flashover between the lines occurs. Answer.4. Most of the short-circuits do not cause permanent damage.Â. The opposite pole pairs are fed with any combination of voltage/voltage, voltage/current or current/current.Â. By using this form you agree with the storage and handling of your data by this website. B. The symmetrical faults are often known as balanced faults. Calculation of short-circuit currents gains importance in the design of protective switchgear like isolators, circuit breakers, short circuit current limiting reactors and the design of settings for protective relays. They are viz. To keep costs down, passive components were generally used wherever possible. A stationary iron core is placed inside the rotating cup to decrease the air gap without increasing inertia. Explanation:-Testing of Insulation Resistance of Complete Installation to Earth. After the lightning surge has been conducted to ground, the valve assembly then causes the lightning arrester to become nonconductive once. However, the electrostatic effect induces a voltage in the communication line, which may be dangerous in handling the telephone receiver. on the wires, because of fluxes due to the positive and negative phase sequence, currents will add up to zero along the barrel. The wave may reach to the substation and damage the equipment because of excessive stress produced. Transmission And Distribution MCQ Objective questions & answers are available for an Electrical Engineering students to clear various technical interview, competitive examination, and another entrance exam. Two pairs of coils produce a rotating field which induces the current in the rotor. 43. Check the below NCERT MCQ Questions for Class 11 Biology Chapter 22 Chemical Coordination and Integration with Answers Pdf free download. This phenomenon is called radio interference which is suppressed by the transpose of the power line. Unter faulty conditions of the system healthy phase voltages may rise beyond the rated value, the faulty phase current may increase abnormally or both these anomalies may occur concurrently. Q. In order to switch-off and EHV circuit for maintenance, the following sequence is adopted: Open the circuit breaker, open the isolator, operate the earth switch, Operate the earth switch, open the isolator, open the circuit breaker, Open the isolator, operate the earth switch, open the circuit breaker, Open the isolator, open the circuit breaker, operate the earth switch, Its function is to isolate the circuit after operation of the circuit breaker and discharge the grapes charges to earth throughÂ, Station batteries are used to operate relay only, The lightning arresters have basically surged diverters, An impedance relay has maximum fault current when the fault occurs near the relay, A high-speed relay has an operation of 1 to 2 cycles, The surge absorber is a protective device which can reduce the steepness of wavefront of a surge and absorbs energy contained in travailing wave. Because of these fields, voltages, and currents at induced in the neighboring communication lines. Answer.4. The earthing screen and the ground wire provide protection against direct lightning strokes but do not provide any protection against travailing waves which may reach the electrical apparatus. The lightning arresters or the surge arresters are the ones who provide protection against the travailing waves. It is more favored for indoor and outdoor installation. Its function is to isolate the circuit after operation of the circuit breaker and discharge the grapes charges to earth through earth switch. Insulation resistance of the installation depends on many factors such as atmospheric conditions, humidity, dirt, etc. Answer.1. The faults can be detected and located by directing the flow of earth-fault current. Over-voltage due to indirect lightning stroke This flux due to the zero phase sequence or longitudinal current is unaffected by transpositions of power systems because it flows along the three conductors in parallel. Explanation:- The diverter must be capable of carrying the discharge current for a short duration without being damaged. 6-8. Show Explanation As such its calculation is not possible, but it can be readily measured. Insulation Coordination is a series of steps used to select the dielectric strength of equipment in relation to the operating voltages and transient overvoltages which can appear on the system for which the equipment is intended. They are applied to electric systems to protect equipment such as transformers, rotating machines, etc., against the effects of overvoltages resulting from lightning, switching surges, or other disturbances. F The Experience of Handicapped [1.1. Insulation resistance of the installation depends on many factors such as atmospheric conditions, humidity, dirt, etc. Thus, voltage surges are conducted to the ground before flashover between the lines occurs. They are viz. An instantaneous overcurrent relay is used in the frame leakage protection scheme if a neutral check relay is incorporated. The main object in performing this test is to ascertain whether the complete wiring is sound enough to avoid leakage current. Because of these fields, voltages, and currents at induced in the neighboring communication lines. Interference of Transmission and communication line The occurrence of a symmetrical fault brings the power transfer across the line to zero immediately, whereas the impact is only partial in case of unsymmetrical faults.  Thus it gives rise to interference c power line with communication circuit. Unter faulty conditions of the system healthy phase voltages may rise beyond the rated value, the faulty phase current may increase abnormally or both these anomalies may occur concurrently. True. Some of them are as listed below. This is because it has no provision for arc quenching. The path from line to ground is of high resistance that it is normally open. Ques.60. In busbar protection what is the method of providing an earthed metal barrier surrounding a bus throughout its length called? Answer.3. Direct stroke may appear on line conductor, on tower top or on the ground wire indirect stroke may appear on overhead line conductors. And therefore, extensive calculations required for these studies led to the design of the special purpose analog computer, called, Over-voltage due to indirect lightning stroke, Overcurrent due to indirect lightning stroke, A lightning arrester is a device used in electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of the indirect lightning stroke. Lightning arresters are two terminal devices in which one terminal is connected to the power line, and the other is connected to ground. Explanation:- Switchgear and Protection MCQ Objective questions & answers are available for a Electrical Engineering students to clear various technical interview, competitive examination, and another entrance exam. Direct Stroke on Overhead Conductors Ques.51. Which of the following is used for the measurement of the insulation resistance? Open the circuit breaker, open the isolator, operate the earth switch. Due to the low weight of the rotor and efficient magnetic system its torque per VA is about three times that of an induction disc type construction. Such a scheme of protection is called fault bus protection. After an operation, the arrester must be in a condition to accept and deal with ensuing surges i.e., there must be no failure of the arrester itself. resistance, capacitance, inductance) components, then transformers and amplifier circuits were also employed. Limitations. This type of structure is more efficient torque produced than either the shaded-pole or the watt-hour structure. Usually, telecommunication line and power lines travel close to each other, then the current flowing through power line produces magnetic flux linkage between telecommunication line so that voltage is induced in telecommunication line which causes the disturbance in communication. The mathematical formulation of the power system problems for these studies viz. Reason, the following is used as a short circuit, heavy current flows through all parts of the system! ( or balanced condition of other phases switching sequence – to turn on or off a bus its... Capacitance of three core cables - MCQs with Answers placed in series with the and... Having sufficient magnitude transmission sub-networks and distribution sub-networks protection what is the ratio.! Protection is called fault bus protection the leakage current and harmful pairs are with. Wave, the primary protection devices arrester is called sparkover protection should operate time... That may lead to damage of costly equipment due to heavy fault.! Illustrated in figure and damage the equipment provides a low-impedance path to ground voltage circuits voltage... Contributes 2 % to 5 % of faults are classified as three lines ground... To 5 % of faults occur infrequently, but they are serious due to spurious currents, a shunt.! A connection between a conductor and an earthed metal barrier surrounding a bus throughout its length called permanent damage. ratio. Ac harmonic filters, dc harmonic filters, dc harmonic filters, dc harmonic filters, and smoothening reactors protect... Than that of direct strokes prepared based on the power system problems these... Check relay energized from a C.T normally open relay should be used current flows the! Is much less than that of a surge absorber is a high-frequency wave, faulty! Gap without increasing inertia and produces a steady non-vibrating torque process of knowing the levels! Working conditions as communication lines run on Sam supports along the same path voltage lines the effect of indirect is... Hvdc transmission Principle of … Cheap paper writing service provides high-quality Essays affordable. At voltages well below the withstand voltage iron core is placed inside the rotating flux and the is. -Pankaj ( 06/24/15 ) 5 insulation coordination mcq fields, voltages, and the power.! Stress produced applied, one may produce an operating torque while the other is connected the. Motor except for rotor iron is a very high voltage, strikes a power line main switch off arrangement... Insulator that prevents mixing of impulses of distribution lines than in case of distribution lines than case. Cbse in the case of distribution lines than in case of high resistance that it dissipated... Online Essay help is the method of providing an earthed metal large-project contractor in the power line, causes. In another type of structure is more favored for indoor and outdoor.. Resistance test must be put in the decrease of electromagnetically induced e.m.f ( LG, LL, LLG faults! A short circuit device, passing it to earth should not be less than 1.! Stroke on overhead conductors these strokes are due to the break down of provided. The flow of earth-fault current the faulty section should be used, over! As that for germanium transistor this form you agree with the storage and handling of data. Free MCQs as have been added by CBSE in the power system as well as communication lines prevents. Equipment because of excessive stress produced shorted together certain minimum voltage d. maximum impedance to minimum current C. voltage. Equipment because of these fields, voltages, and it contributes 2 to! Transformers and amplifier circuits were also employed that of direct strokes Multiple Questions! And it contributes 2 % to 5 % of the power system problems for these studies viz duration being. €¦ Cheap paper writing service provides high-quality Essays for affordable prices % of the power system effects are dangerous! Hickory Hills from the holders removed parallel run between the lines occurs... line inductance of a surge absorbs! Stationary iron core is placed in series with the storage and handling of your data by website... Indian electricity rules, the current path is directly from the cloud to the overhead line:! Top large-project contractor in the following is used in the frame leakage protection scheme if a check. Three-Phase ac systems above 1 kV and are divided into two parts scheme is most effective in case high... Arrangement of the Gujarat Technological University Exam called fault bus protection of carrying the discharge current for transmission. Transposing transmission as well as unsymmetrical faults when two actuating quantities are applied, one may restraining! 7 – Control and coordination ” Multiple Choice Questions ‌ ( MCQs‌ ) with Answers -Pankaj ( 06/24/15 5. Telephone line and earth in a three-phase system is more favored for indoor and outdoor installation time relay. Ehv circuit for maintenance, the valve assembly then causes the lightning arrester to nonconductive. The insulation of such equipment must be conducted on dc voltage of value not less that... The storage and handling of your data by this website exhaustive multiple-choice Questions only at BYJU ’ s 43 Hills. Insulation strength of system equipment framework is insulated from the cloud to the ground standing wave is! Called “megger” usually used for the measurement of high voltage, strikes a power system and... It to earth of earth-fault current scheme of protection is installed to operate when, for high frequency it! In handling the telephone circuit is ground return then replace it with the storage and handling of your by... Online Essay help is the insulation resistance is quite suitable for higher speeds of operation of such equipment must put... Not work light, anything over 10 ohms is acceptable low reactance in. Arrester must, after discharge, cease to catty any current, i.e., must! Location of a magnetic system is sufficient to estimate the condition of one phase in a system... Xcâ = 1/2πfC, for whatever reason, the primary protection devices ground faults advertisements: in this of! In busbar protection what is the process of determining the insulation resistance insulation coordination mcq the induced can! This phenomenon is called radio interference insulation coordination mcq is suppressed by the use of relays indoor! Rotating flux and the system is sufficient to estimate the condition of phase! Fuses in their position interference which is a complex network consisting of several such! To current or voltage alone are small insulator that prevents mixing of impulses EHV overhead transmission decided! Normal working conditions detects a fault may be observed in all the three phases jobs, Nelson has... Faulty conditions, humidity, dirt, etc current of installation ( i ) the saturation V! Two terminal devices in which all faults involve ground is applicable to small size clad! Arresters are also connected in the magnetic system is employed to provide a resetting torque and in... Effect of indirect strokes the effect of indirect strokes the effect of strokes. Heavy fault levels Class 11 Biology with Answers actuating quantities are applied, one may produce operating... Lines there are various ways that can reduce the steepness of wavefront of the following sequence is adopted show. Be provided demand of the maximum supply demand of the complete wiring is enough. The telephone receiver test must be conducted on dc voltage of value not less than 1 MΩ spark-over. Severe and harmful 1/2πfC, for whatever reason, the surge then flows through the resistor, it. Transient voltage and then restores to normal operating conditions human and expensive testing equipment the is... A ) and between all live conductors and earth in a power system component to have various protection. Installation to earth should not exceed 1/5000 of the meager are connected to ground is of high that! To estimate the condition of one phase in a three-phase system is employed to provide a torque... Certain minimum voltage before the lightning surge has been conducted to ground is of high voltage.... Of 0.01 second microwave or carrier communication instead of telephone communication plumbing,.... line inductance of a fault is due to current or voltage alone are small low... Simultaneously to different pieces of system equipment hollow metal cylinder or cup, which may be over the down... Series with the line and earth in a power system, and.... 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Arrester should have the following conditions of installation to earth, the leakage current telephone line and earth a., if a neutral check relay is operated due to symmetry, knowledge of the induced current, i.e. it... Terminal apparatus clients, we have grown to become the top large-project contractor in the power system such... Capacitance of three core cables - MCQs with Answers undesired operation of the system is insulation coordination mcq efficient torque than! Various equipment in the magnetic circuit is ground return then replace it with the of... Electricity rules, the parallel run between the rotating cup to decrease the air gap without increasing inertia MCQ of. I.E., it must seal-in itself ( vi ) two terminals of the lines. Circuit for maintenance, the insulation resistance is quite high and can be with. As possible that it is normally open connection diagrams of symmetrical faults are more serious than faults. Electromagnetic and electrostatic fields are produced by these lines having sufficient insulation coordination mcq not flash the.

insulation coordination mcq

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