How main generator earthing is done?

How main generator earthing is done?
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1 Answer

Answer :

Generator neutral earthing is done through transformer and earth fault current is limited through resistance, which is connected across the secondary of the transformer. Generator 16.5 kV earth fault current is isolated from 220 kV through GT. Only star point of the generator is grounded. 
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Related questions

Why the earthing transformer primary voltage is 16.5 kV rated in main generator even though actual voltage during the E/F is root 3 times less?

Description : Why the earthing transformer primary voltage is 16.5 kV rated in main generator even though actual voltage during the E/F is root 3 times less?

Last Answer : The transformer should not saturate during E/F otherwise it will cause ferroresonance with the GT winding capacitance. Dangerous O/V and neutral shifting will occur. During loss of load or field ... saturation. Saturation can also occur due to point on wave of application causing flux doubling. 

How many earthing should be done for motors? Why?

Description : How many earthing should be done for motors? Why? 

Last Answer : Two. For reliability.  

In a diesel electric plant, raising the generator's field excitation will cause the DC propulsion motor to ________. A. increase in speed B. decrease in speed C. affect generator speed only D. affect main motor speed if done in conjunction with higher generator engine speeds

Description : In a diesel electric plant, raising the generator's field excitation will cause the DC propulsion motor to ________. A. increase in speed B. decrease in speed C. affect generator speed only D. affect main motor speed if done in conjunction with higher generator engine speeds

Last Answer : Answer: A

What is the neutral point earthing and its advantages?

Description : What is the neutral point earthing and its advantages?

Last Answer : In substation all the neutrals of rotating machines, transformers, busbars and other equipment are connected to ground. Some of the advantages are: Earth fault protection is based on the method of ... , grounding of neutral helps to reduce the over-voltages which occur on the one healthy phases

Why we do 2 types of earthing on transformer i.e.: body earthing & neutral earthing, what is function. I am going to install a 5oo kva transformer & 380 kva DG set what should the earthing value?

Description : Why we do 2 types of earthing on transformer i.e.: body earthing & neutral earthing, what is function. I am going to install a 5oo kva transformer & 380 kva DG set what should the earthing value?

Last Answer : The two types of earthing are Familiar as Equipment earthing and system earthing. In Equipment earthing: body (non conducting part) of the equipment should be earthed to safeguard the human ... earthing will be further classified into directly earthed, Impedance earthing, resistive (NGRs) earthing.

Explain types of Earthing.

Description : Explain types of Earthing.

Last Answer : A:The two types of earthing are Equipment earthing and system earthing. In Equipment earthing: body ( non conducting part) of the equipment should be earthed to safegaurd the human beings ... . This type of earthing is further classified into directly earthed, Impedance earthing, resistive earthing.

What is different between resistance grounding system and resistance earthing system?

Description : What is different between resistance grounding system and resistance earthing system?

Last Answer : 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. Resistance earthing system is done in an electric equipment in order to protect the equipment in occurrence of fault in the system.

State the various types of earthing.

Description : State the various types of earthing.

Last Answer : Solid earthing, resistance earthing , reactance earthing , voltage transformer earthing and zig-zag transformer earthing.

What is difference between earthing and grounding?

Description : What is difference between earthing and grounding?

Last Answer : Both have same meaning. The term earthing is used in U.K. and grounding in U.S.A.ground means earth.

Why the neutral is earthed through earthing resistance in case of UT and SUT?

Description : Why the neutral is earthed through earthing resistance in case of UT and SUT? 

Last Answer : This is done to limit the earth fault current.  

What is the purpose of shaft earthing and bearing insulation?

Description : What is the purpose of shaft earthing and bearing insulation?

Last Answer : The voltage generated in the shaft due to the leakage fluxes can circulate current through the shaft. If shaft earthing is not done the leakage current will flow through the bearings to ground and pitting of bearings will result. Hence bearing foundation and pipelines are insulated. 

Why shaft-earthing brush is different from normal brush?

Description : Why shaft-earthing brush is different from normal brush?

Last Answer : The contact resistance should be very low for shaft earthing brush, to prevent even small current through the oil film, so used copper magnite brush or silver carbon brush.

What should the statutory provision of earthing?

Description : What should the statutory provision of earthing?  

Last Answer : a. Earthing shall generally be carried out in accordance with the requirement of India electricity rule 1956, as amended from time to time and the relevant regulations of the electricity supply ... , etc. used in earthing shall conform to Indian standard specifications, wherever these exist. 

What is difference between earthing and grounding?

Description : What is difference between earthing and grounding?

Last Answer : Both have same meaning. The term earthing is used in U.K. and grounding in U.S.A. ground means earth.  

What earthing is done in hilly areas ?

Description : What earthing is done in hilly areas ?

Last Answer : Sheet earthing is done in hilly areas. Shit electrodes are placed by digging trenches on the slopes of the hill.

Why is earthing done ?

Description : Why is earthing done ?

Last Answer : Earthing is done to allow the current to flow to the ground during an electrical fault so that the protection device can work to disconnect the faulty circuit.

Earthing-up in potato is done at

Description : Earthing-up in potato is done at

Last Answer : Ans.30 – 45 DAS

Earthing up in sugarcane is done at

Description : Earthing up in sugarcane is done at

Last Answer : Ans.4 month after planting

Earthing-up is done in groundnut crop at

Description : Earthing-up is done in groundnut crop at

Last Answer : Ans.35 to 45 DAS

What are the works to be done in generator in major overhauling?

Description : What are the works to be done in generator in major overhauling?

Last Answer : Works on stator a) Hydro test (DM water at 5 kg/cm2 pressure, leak acceptable is 5% for 24 hrs). b) Hydro test of H2 coolers (DM water at 4 kg/cm2 for 30 seconds no leak is allowed) ... . j) Slip-ring groove cutting and machining. k) Patina formation. Then OCC test. 

The shipboard general alarm system must receive its main source of power from _____________. A. a storage battery B. the emergency generator C. an auxiliary generator D. the ship's service generator

Description : The shipboard general alarm system must receive its main source of power from _____________. A. a storage battery B. the emergency generator C. an auxiliary generator D. the ship's service generator

Last Answer : Answer: A

The source of emergency lighting and power at loss of normal ship's power on a cargo vessel should be obtained from the ______________. A. emergency generator supply to the emergency switchboard B. emergency generator supply to the main switchboard C. battery supply to the main switchboard D. turbogenerator supply to the emergency switchboard

Description : The source of emergency lighting and power at loss of normal ship's power on a cargo vessel should be obtained from the ______________. A. emergency generator supply to the emergency ... switchboard C. battery supply to the main switchboard D. turbogenerator supply to the emergency switchboard

Last Answer : Answer: A

The main purpose of an electric space heater installed in a large AC generator is to _____________. A. keep the lube oil warm for quick starting B. prevent moisture from condensing in the windings when the machine is shutdown C. prevent the windings from becoming brittle D. prevent acidic pitting of the slip rings

Description : The main purpose of an electric space heater installed in a large AC generator is to _____________. A. keep the lube oil warm for quick starting B. prevent moisture from condensing in the ... is shutdown C. prevent the windings from becoming brittle D. prevent acidic pitting of the slip rings

Last Answer : Answer: B

In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter B. help the windings to cool to ambient temperature C. release any residual capacitive charge from the windings D. help the windings to cool to the same temperature as the ground test connection

Description : In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter ... the windings D. help the windings to cool to the same temperature as the ground test connection

Last Answer : Answer: C

The prime mover of an AC two pole main propulsion generator drives the generator at 3600 RPM. If the main propulsion motor has 80 poles, what will be the propeller speed? A. 45 RPM B. 80 RPM C. 90 RPM D. 180 RPM

Description : The prime mover of an AC two pole main propulsion generator drives the generator at 3600 RPM. If the main propulsion motor has 80 poles, what will be the propeller speed? A. 45 RPM B. 80 RPM C. 90 RPM D. 180 RPM

Last Answer : Answer: C

As shown in the illustration, the motor generator(M-G) set's three-phase motor drives the ______________. EL-0101 A. motor and the generator B. motor and the exciter C. generator and the exciter D. main field and the interpole field

Description : As shown in the illustration, the motor generator(M-G) set's three-phase motor drives the ______________. EL-0101 A. motor and the generator B. motor and the exciter C. generator and the exciter D. main field and the interpole field

Last Answer : Answer: C

Undervoltage trips are frequently installed on switchboard circuit breakers to trip ____________. A. out generators in the event of severe arcing or sparking B. out generators when there is reversal of power in the main circuit C. the breaker if the generator overspeeds by 5%, but continues to run D. out generators when there is low voltage in the main circuit

Description : Undervoltage trips are frequently installed on switchboard circuit breakers to trip ____________. A. out generators in the event of severe arcing or sparking B. out generators when there is reversal of power ... , but continues to run D. out generators when there is low voltage in the main circuit

Last Answer : Answer: D

The purpose of the reverse power relay, provided on a ship's service alternator panel, is to trip the circuit in the event of ______________. A. main circuit overload B. high power transfer C. generator overspeeding D. alternator motorization

Description : The purpose of the reverse power relay, provided on a ship's service alternator panel, is to trip the circuit in the event of ______________. A. main circuit overload B. high power transfer C. generator overspeeding D. alternator motorization

Last Answer : Answer: D

A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker

Description : A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker

Last Answer : Answer: D

As shown in the illustration, the M-G set's three-phase motor drives the ______________. EL-0101 A. motor and the generator B. motor and the exciter C. generator and the exciter D. main field and the interpole field

Description : As shown in the illustration, the M-G set's three-phase motor drives the ______________. EL-0101 A. motor and the generator B. motor and the exciter C. generator and the exciter D. main field and the interpole field

Last Answer : Answer: C

Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Last Answer : Answer: B

The frequency of an AC generator is adjusted by means of the ____________. A. main alternator field rheostat B. exciter field rheostat C. prime mover governor control D. equalizing reactor

Description : The frequency of an AC generator is adjusted by means of the ____________. A. main alternator field rheostat B. exciter field rheostat C. prime mover governor control D. equalizing reactor

Last Answer : Answer: C

The main purpose of an electric space heater installed in a large AC generator is to _____________. A. prevent the windings from becoming brittle B. prevent moisture from condensing in the windings during shutdown C. prevent acidic pitting of the slip rings D. keep the lube oil warm for quick starting

Description : The main purpose of an electric space heater installed in a large AC generator is to _____________. A. prevent the windings from becoming brittle B. prevent moisture from condensing in the windings during ... C. prevent acidic pitting of the slip rings D. keep the lube oil warm for quick starting

Last Answer : Answer: B

Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated for by the __________ A. governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Last Answer : Answer: B

In an AC synchronous motor electric propulsion plant, propeller speed is controlled by varying the _____________. A. prime mover speed B. electric coupling field strength C. number of energized main motor poles D. propulsion generator field strength

Description : In an AC synchronous motor electric propulsion plant, propeller speed is controlled by varying the _____________. A. prime mover speed B. electric coupling field strength C. number of energized main motor poles D. propulsion generator field strength

Last Answer : Answer: A

On a vessel with turbo-electric drive, which of the following conditions would indicate that the propulsion motor had dropped out of synchronization with the propulsion generator? A. Excessive vibration of the vessel B. Tripped main motor interlocks C. Overheated crosstie busses D. Closed contact in the field circuits

Description : On a vessel with turbo-electric drive, which of the following conditions would indicate that the propulsion motor had dropped out of synchronization with the propulsion generator? A. Excessive ... Tripped main motor interlocks C. Overheated crosstie busses D. Closed contact in the field circuits

Last Answer : Answer: A

Why main generator/UT is not provided with separate overfluxing protection?

Description : Why main generator/UT is not provided with separate overfluxing protection?

Last Answer : Since GT is provided with overfluxing protection, it is adequate to protect main generator / UT also. Main generator can withstand higher degree of overfluxing. If a generator CB is used, separate overfluxing protection is essential for main generator. 

Why 100% winding protection is felt essential for main generator stator E/F protection? (Used in NAPS onwards?)

Description : Why 100% winding protection is felt essential for main generator stator E/F protection? (Used in NAPS onwards?)  

Last Answer : At MAPS 4% of winding is not protected. Earlier felt that the Electro magnetic stress due high external fault currents near 4% of neutral may not be high to cause E/F here. But now felt that the mechanical stress can leads to E/F. 

What precautions should be taken while meggering main generator?

Description : What precautions should be taken while meggering main generator?

Last Answer : All PT’s are racked out. Earthing transformer grounding terminals disconnected. Barring gear shall be kept off. Stator water shall be drained fully and hot air blown through conductors. Generator flexible lines shall be disconnected to isolate GT/UT. 

What are the working principles of generator main protections?

Description : What are the working principles of generator main protections?

Last Answer : GENERATOR START UP PROTECTIONS SUPPLEMENTARY PROTECTION OF GENERATOR The generator is normally expected to run rated speed before excitation power is applied by closing the field breaker. ... position to ensure that the protection is inoperable when the machine is connected to grid.  

How main generator protection grouped?

Description : How main generator protection grouped?

Last Answer : The various protections associated with the generator, Generator transformer and Unit transformer are connected to a trip unit through trip relays 86A, 86B and 86C. The protective levels of generator are in ... breaker. During Class C trip, the generator will come on House load mode of operation.  

Write nameplate details of the main generator.

Description : Write nameplate details of the main generator. 

Last Answer : Type THW-235 kW 237700 kVA 264000 Voltage 16500 V Amps 9240 A Power factor 0.9 lag. Field voltage 326 V Field current 2755 A Insulation Class-F Speed 3000 rpm 50 Hz, 3, double star connection. 

What is the purpose of back up impedance protection in main generator?

Description : What is the purpose of back up impedance protection in main generator?  

Last Answer : Covers inter-phase faults both externals to the GT and in GT. This also covers partially faults inside generator, time delayed to coordinate with 230 kV-distance protection. 

Why cannot we have cables instead of bus duct in main generator?

Description : Why cannot we have cables instead of bus duct in main generator? 

Last Answer : Very large number of cables in parallel required problems of sealing the terminations. 

Will main generator differential relay pick up for generator earth faults?

Description : Will main generator differential relay pick up for generator earth faults? 

Last Answer : No earth fault current limited to 5A, while differential setting is 10%. 

When the hydrogen explosion will take place in main generator?

Description : When the hydrogen explosion will take place in main generator?

Last Answer : When hydrogen concentration in air is more than 4% and less than 74% causes the explosion.  

What are main types of DC generator?

Description : What are main types of DC generator? 

Last Answer : Mainly there are three types. a. Series generator or series wound generator. b. Shunt generator or shunt wound generator. c. Compound generator. There are different types of compound generator. ... a. Under compound generator. b. Flat or level compound generator. c. Over compound generator. 

What is Earthing Lead ?

Description : What is Earthing Lead ?

Last Answer : The wire that connects the earth continuity wire and the earth electrode is called the earthing lead.