Electrical Switchgear And Protection Pdf

electrical switchgear and protection pdf

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The main function of a fuse is to a protect the line b open the circuit c protect the appliance d prevent excessive currents e none of the above Ans: d.

Introduction of MVSWGR SLD In an electric power system, switchgear is composed of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Protection of generators against Stator faults, Rotor faults, and Abnormal Conditions. Abb Switchgear Manual Enterzocf Author download.

Handbook of Switchgears Bharat Heavy Electrical Limited

The main function of a fuse is to a protect the line b open the circuit c protect the appliance d prevent excessive currents e none of the above Ans: d. On which of the following routine tests are conducted? SF6 gas a is yellow in colour b is lighter than air c is nontoxic d has pungent small e none of the above Ans: c. The arcing contacts in a circuit breaker are made of a copper tungsten alloy b porcelain c electrolytic copper d aluminium alloy Ans: a. Which of the following medium is employed for extinction of arc in air circuit breaker?

With which of the following, a circuit breaker must be equipped for remote operation? Fault diverters are basically a fuses b relays c fast switches d circuit breakers Ans: c. A thermal protection switch can protect against a short-circuit b temperature c overload d over voltage Ans: c.

Arc in a circuit behaves as a a capackive reactance b an inductive reactance c a resistance increasing with voltage rise across the arc d a resistance decreasing with voltage rise across the arc Ans: d.

Thermal circuit breaker has a delayed trip action b instantaneous trip action c both of the above d none of the above Ans: a. Relays can be designed to respond to changes in a resistance, reactance or impedance b voltage and current c light intensity d temperature e all above Ans: e. Overload relays are of…… type. Thermal overload relays are used to protect the motor against over current due to a short-circuits b heavy loads c grounds d all of the above Ans: b.

The relay operating speed depends upon a the spring tension b the rate of flux built up c armature core air gap d all of the above Ans: d. In order that current should flow without causing excessive heating or voltage drop, the relay contacts should a have low contact resistance b be clean and smooth c be of sufficient size and proper shape d have all above properties Ans: d. Circuit breakers usually operate under a transient state of short-circuit current b sub-transient state of short-circuit current c steady state of short-circuit current d after D.

Circuit breakers are essentially a current carrying contacts called electrodes b arc extinguishers c circuits to break the system d transformers to isolate the two systems e any of the above Ans: a. The current zero interruption, in oil and air blast circuit breakers, is achieved by a lengthening of the gap b cooling and blast effect c both a and b d deionizing the oil with forced air e none of the above Ans: c.

Air blast circuit breaker is used for a over currents b short duty c intermittant duty d repeated duty Ans: d. An efficient and a well designed protective relaying should have a good selectivity and reliability b economy and simplicity c high speed and selectivity d all of the above Ans: d.

Burden of a protective relay is the power a required to operate the circuit breaker b absorbed by the circuit of relay c developed by the relay circuit d none of the above Ans: b. Directional relays are based on flow of a power b current c voltage wave d all of the above Ans: a. A differential relay measures the vector difference between a two currents b two voltages c two or more similar electrical quantities d none of the above Ans: c.

A transmission line is protected by a inrush protection b distance protection c time graded and current graded over current protection d both b and c e none of the above Ans: d. Large internal faults are protected by a merz price percentage differential protection b mho and ohm relays c horn gaps and temperature relays d earth fault and positive sequence relays Ans: a.

When a transmission line is energized, the wave that propagates on it is a current wave only b voltage wave only c both a and b d power factor wave only Ans: c. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring a current during abnormal condition b voltage during abnormal condition c constantly the electrical quantities which differ during normal and abnormal conditions d none of the above Ans: c.

Ionization in circuit breaker is facilitated by a high temperature b increase of mean free path c increasing field strength d all of the above Ans: d. In a circuit breaker the basic problem is to a maintain the arc b extinguish the arc c transmit large power d emit the ionizing electrons Ans: c.

Overheating of relay contacts or contact born out is due to a slow making and breaking of load circuit contacts b foreign matter on the contact surface c too low contact pressure d all of the above Ans: d.

Interruption of large currents by relay requires a arc suppressing blow out coils b wide separation of the opened contacts c high speed opening of contacts d all of the above Ans: d. Shunt capacitance is neglected while considering a short transmission line b medium transmission line c long transmission line d medium and long transmission lines Ans: a. The arc voltage produced in A. The time of closing the cycle, in modern circuit breakers is a 0. Insulation resistance of high voltage circuit breakers is more than a 1 mega ohms b 10 mega ohms c mega ohms d mega ohms Ans: c.

Which of the following is the least expensive protection for overcurrent is low voltage system? The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to a lubricate the contacts b insulate the contacts from switch body c extinguish the arc d all of the above e none of the above Ans: c.

To protect most of the electrical equipment handling low power, the types of relays used are a thermocouple b electronic and bimetallic c both a and b d none of the above Ans: c. Wave trap is used to trap waves of a power frequencies b higher frequencies entering generator or transformer units c either of the above d none of the above Ans: b.

Ungrounded neutral transmission system is not recommended because of system a insulation being overstressed due to over voltages b insulation overstress may lead to failure and subsequent phase to phase faults c being inadequately protected against ground fault d all of the above Ans: d. The reflection co-efficient at the open circuited end of a transmission line.

For the protection of power station buildings against direct strokes the requirements are a interception b interception and conduction c interception, conduction and dissipation d interception, conduction, dissipation and reflection e none of the above Ans: c. The line insulation is the insulation level of the station equipment. The interaction between a transmission line and communication line is minimized by a transposing transmission as well as communication lines b increasing the height of the trans-mission line tower c increasing the distance between the two lines d all of the above Ans: d.

When a wave propagates on a transmission line, it suffers reflection several times at a tapping b load end c sending end d sending and other end e all of the above Ans: d. Which of the following statements is incorrect? Discrimination between main and back up protection is provided by the use of relays which are a fact b sensitive c slow d none of the above Ans: c.

Induction cup relay is operated due to changes in a current b voltage c impedance d all of the above Ans: d. Short-circuit currents are due to a single phase to ground faults b phase to phase faults c two phase to ground faults d three phase faults e any of these Ans: e. To reduce short circuit fault currents are used. Bus coupler is very essential in arrangement a single bus b double bus, double breaker c main and transfer bus d all of the above Ans: c. For cost and safety, the outdoor substations are installed for voltages above a 11 kV b 33 kV c 60kV d kV Ans: b.

The short circuit in any winding of the transformer is the result of a mechanical vibration b insulation failure c loose connection d impulse voltage Ans: d. For which of the following protection from negative sequence currents is provided? Distance relays are generally a split-phase relays b reactance relays c impedance relays d none of the above Ans: d. For which of the following ratings of the transformer differential protection is recommended?

The under voltage relay can be used for a generators b busbars c transformers d motors e all of the above Ans: e. The relay with inverse time characteristic will operate within a 1. The single phasing relays are used for the protection of a single phase motors only b two phase motors only c two single phase motors running in parallel d three phase motors Ans: d. Which of the following devices will receive voltage surge first travelling on the transmission line? Which of the following parameter can be neglected for a short line?

Series reactors should have a low resistance b high resistance c low impedance d high impedance Ans: a. Which of the following circuit breakers has high reliability and minimum maintenance? Arc in a circuit breaker is interrupted at a zero current b maximum current c minimum voltage d maximum voltage Ans: a. What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load?

The inverse definite mean time relays are used for over current and earth fault protection of transformer against a heavy loads b internal short-circuits c external short-circuits d all of the above Ans: b. Over voltage protection is recommended for a hydro-electric generators b steam turbine generators c gas turbine generators d all of the above e none of the above Ans: d. Air blast circuit breakers for kV power system are designed to operate in a microsecond b 50 millisecond c 0.

Overfluxing protection is recommended for a distribution transformer b generator transformer of the power plant c auto-transformer of the power plant d station transformer of the power plant Ans: b. Series capacitors are used to a compensate for line inductive reactance b compensate for line capacitive reactance c improve line voltage d none of the above Ans: a.

The material used for fuse must have a low melting point and high specific resistance b low melting point and -low specific resistance c high melting point and low specific resistance d low melting point and any specific resistance Ans: a. If the fault occurs near the impedance relay, the VII ratio will be a constant for all distances b lower than that of if fault occurs away from the relay c higher than that of if fault occurs away from the relay d none of the above Ans: b.

The torque produced in induction type relay shaded pole structure is a inversely proportional to the current b inversely proportional to the square of the current c proportional to the current d proportional to square of the current Ans: b. The steady state stability of the power system can be increased by a connecting lines in parallel b connecting lines in series e using machines of high impedance d reducing the excitation of machines e none of the above Ans: a.

The inductive interference between power and communication line can be minimized by a transposition of the power line b transposition of the communication line c both a and b d increasing the distance between the conductors Ans: c.

The power loss is an important factor for the design of a transmission line b motor c generator d feeder Ans: a. A fuse is connected a in series with circuit b in parallel with circuit c either in series or in parallel with circuit d none of the above Ans: a. The fuse blows off by a burning b arcing c melting d none of the above Ans: c.

On which of the following effects of electric current a fuse operates? An isolator is installed a to operate the relay of circuit breaker b as a substitute for circuit breaker c always independent of the position of circuit breaker d generally on both sides of a circuit breaker Ans: d.

A fuse in a motor circuit provides protection against a overload b short-circuit and overload c open circuit, short-circuit and overload d none of the above Ans: b. A fuse is never inserted in a neutral wire b negative of D. Oil switches are employed for a low currents circuits b low voltages circuits c high voltages and large currents circuits d all circuits Ans: c. A switchgear is device used for a interrupting an electrical circuit b switching an electrical circuit The fuse wire, in D.

By which of the following methods major portion of the heat generated in a H. A short-circuit is identified by a no current flow b heavy current flow c voltage drop d voltage rise Ans: b.

The information to the circuit breaker under fault conditions is provided by a relay b rewirable fuse c H. To limit short-circuit current in a power system are used. A balanced 3-phase system consists of a zero sequence currents only b positive sequence currents only c negative and zero sequence currents d zero, negative and positive sequence currents Ans: b. In a single bus-bar system there will be complete shut down when a fault occurs on the bus itself b fault occurs on neutral line c two or more faults occur simultaneously d fault occurs with respect to earthing Ans: a.

Your email address will not be published. The main function of a fuse is to a protect the line b open the circuit c protect the appliance d prevent excessive currents e none of the above Ans: d 2. SF6 gas a is yellow in colour b is lighter than air c is nontoxic d has pungent small e none of the above Ans: c 4. The arcing contacts in a circuit breaker are made of a copper tungsten alloy b porcelain c electrolytic copper d aluminium alloy Ans: a 5.

Fault diverters are basically a fuses b relays c fast switches d circuit breakers Ans: c 8. A thermal protection switch can protect against a short-circuit b temperature c overload d over voltage Ans: c 9. Arc in a circuit behaves as a a capackive reactance b an inductive reactance c a resistance increasing with voltage rise across the arc d a resistance decreasing with voltage rise across the arc Ans: d

Switchgear

Premium Membership. Learn from experienced power engineers. The neutral point of the generator is usually earthed , so as to facilitate the protection of the stator winding and associated system. Impedance is inserted in the earthing lead to limit the magnitude of the earth fault current. Generators which are directly connected to the transmission or distribution system are usually earthed through a resistance which will pass approximately rated current to a terminal earth fault. In case of generator-transformer unit, the generator winding and primary winding of a transformer can be treated as an isolated system that is not influenced by the earthing requirements of the transmission system. It is important that the earthing transformer never becomes saturated, otherwise a very undesirable condition of ferro resonance may occur.

The switches, fuses, circuit breaker , isolator, relays, current and potential transformer, indicating instrument, lightning arresters and control panels are examples of the switchgear devices. The switchgear system is directly linked to the supply system. It is placed in both the high and low voltage side of the power transformer. It is used for de-energizing the equipment for testing and maintenance and for clearing the fault. When the fault occurs in the power system, heavy current flow through equipment due to which the equipment get damaged, and the service also get interrupted. So to protect the lines, generators, transformers and other electrical equipment from damage automatic protective devices or switchgear devices are required. The automatic protective switchgear mainly consists of the relay and circuit breaker.

Low-voltage switchgear fundamentals

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Shri S G Deshpande, Sr. Switchgear is an important link in any power system network, including transmission and distribution systems. These days, increased emphasis is being given to designing the best possible switchgear and associated equipment system. This book aims to provide a holistic view of all the aspects of switchgear, and highlights the role it plays alongwith its associated systems, in the control and regulation of power flow in power system network. This book is the collective effort of 22 experts from BHEL, a leading switchgear manufacturer in India.

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Electrical switchgear refers to a centralized collection of circuit breakers, fuses and switches circuit protection devices that function to protect, control and isolate electrical equipment. The circuit protection devices are mounted in metal structures.

Common Terms

 Оно есть, - кивнул Стратмор.  - Тебя оно не обрадует. - В ТРАНСТЕКСТЕ сбой. - ТРАНСТЕКСТ в полном порядке. - Вирус. - Никакого вируса. Выслушай меня внимательно, - попросил Стратмор.

 У вас испуганный вид, - сказала Сьюзан. - Настали не лучшие времена, - вздохнул Стратмор. Не сомневаюсь, - подумала. Сьюзан никогда еще не видела шефа столь подавленным. Его редеющие седые волосы спутались, и даже несмотря на прохладу, создаваемую мощным кондиционером, на лбу у него выступили капельки пота. Его костюм выглядел так, будто он в нем спал.

Сьюзан обмякла, испытав огромное облегчение, и почувствовала, что вновь нормально дышит: до этого она от ужаса задержала дыхание. Предмет в руке Стратмора излучал зеленоватый свет. - Черт возьми, - тихо выругался Стратмор, - мой новый пейджер, - и с отвращением посмотрел на коробочку, лежащую у него на ладони. Он забыл нажать кнопку, которая отключила звук. Этот прибор он купил в магазине электроники, оплатив покупку наличными, чтобы сохранить анонимность. Никто лучше его не знал, как тщательно следило агентство за своими сотрудниками, поэтому сообщения, приходящие на этот пейджер, как и отправляемые с него, Стратмор старательно оберегал от чужих глаз. Сьюзан опасливо огляделась.

Protection and Switchgear

 Где мой ключ? - прозвучал знакомый голос.

Стратмор повернулся, и Сьюзан сразу же его потеряла. В страхе она вытянула вперед руки, но коммандер куда-то исчез. Там, где только что было его плечо, оказалась черная пустота.

 - Первым делом вы отдаете мне пистолет. И оба идете со. - В качестве заложников? - холодно усмехнулся Стратмор.  - Грег, тебе придется придумать что-нибудь получше.

Pdf of switchgear and protection Pdf of switchgear and protection Pdf of switchgear and protection

Вот. Все прочитали: - Разница в весе незначительна… разделяются вследствие газовой диффузии… 10,032498X10134 в сравнении с 1939484X1023. - Ну вот, наконец-то! - вскрикнул Джабба.  - Это и есть их вес. - Тридцать секунд.

Прикрыв глаза, давая им долгожданный отдых, он вдруг почувствовал, что кто-то тянет его за ногу. - Джабба. Вылезай скорее! - послышался женский голос. Мидж все же его разыскала. Он застонал.

Все было сделано как положено. Тогда откуда же пришла команда на ручное отключение. - рассердилась .

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Gooddaystifsand

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What is Switchgear? • Switchgear is the combination of switches, fuses or circuit breakers(CB) used to control, protect & isolate electrical equipment. • It is used.

Afra B.

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