Why guard connection is given for megger?

Why guard connection is given for megger?
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1 Answer

Answer :

For true measurement of IR value of HV to earth of a transformer, connect line to HV, earth to transformer tank and guard to LV. Therefore leakage current from HV to LV is not included.  
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Related questions

The reading at 'M' on the megger scale illustrated, is ____. EL-0044 A. 7.1 meg ohms B. 71 meg ohms C. .71 meg ohms D. 200,000,000 ohms

Description : The reading at 'M' on the megger scale illustrated, is ____. EL-0044 A. 7.1 meg ohms B. 71 meg ohms C. .71 meg ohms D. 200,000,000 ohms

Last Answer : Answer: A

When testing for blown fuses in a three-phase supply circuit to a motor, you should first ___________________. A. apply the megger across the tops of the line fuses B. apply an ammeter diagonally across the top of the first line fuse and the bottom of the third line fuse C. apply the voltage tester across the bottoms of the line fuses D. ensure the circuit is de-energized, and then use a continuity tester

Description : When testing for blown fuses in a three-phase supply circuit to a motor, you should first ___________________. A. apply the megger across the tops of the line fuses B. apply an ammeter diagonally across ... of the line fuses D. ensure the circuit is de-energized, and then use a continuity tester

Last Answer : Answer: D

The reading at 'M' on the megger scale shown in the illustration, is __________. EL-0044 A. 7.1 meg ohms B. .71 meg ohms C. 71 meg ohms D. 200,000,000 ohms

Description : The reading at 'M' on the megger scale shown in the illustration, is __________. EL-0044 A. 7.1 meg ohms B. .71 meg ohms C. 71 meg ohms D. 200,000,000 ohms

Last Answer : Answer: A

Which of the conditions listed will indicate the need to clean the insulation on the windings of an electric motor? A. Higher than normal operating temperature. B. Excessive vibration at normal speed. C. Sparking at the brushes. D. High megger readings.

Description : Which of the conditions listed will indicate the need to clean the insulation on the windings of an electric motor? A. Higher than normal operating temperature. B. Excessive vibration at normal speed. C. Sparking at the brushes. D. High megger readings.

Last Answer : Answer: A

The reading at 'Z' on the megger scale shown in the illustration is ____________. EL-0044 A. 30,000 ohms B. 300,000 ohms C. 3,000,000 ohms D. 30,000,000 ohms

Description : The reading at 'Z' on the megger scale shown in the illustration is ____________. EL-0044 A. 30,000 ohms B. 300,000 ohms C. 3,000,000 ohms D. 30,000,000 ohms

Last Answer : Answer: C

Routine maintenance of dry-type transformers should include ______________. A. preventing the entrance of water from broken pipe lines steam lines B. keeping protective surfaces and insulating bushings free of dirt and conductive debris C. periodic testing of insulation resistance with a megger D. all of the above

Description : Routine maintenance of dry-type transformers should include ______________. A. preventing the entrance of water from broken pipe lines steam lines B. keeping protective surfaces and insulating bushings free of ... debris C. periodic testing of insulation resistance with a megger D. all of the above

Last Answer : Answer: D

The reading at 'K' on the megger scale shown in the illustration, is ______________. EL-0044 A. 400 ohms B. 4,000 ohms C. 40,000 ohms D. 400,000 ohms

Description : The reading at 'K' on the megger scale shown in the illustration, is ______________. EL-0044 A. 400 ohms B. 4,000 ohms C. 40,000 ohms D. 400,000 ohms

Last Answer : Answer: D

The reading at 'C' on the megger scale illustrated, is ________. EL-0044 A. 200,000 ohms B. 2,000,000 ohms C. 20,000,000 ohms D. 200,000,000 ohms

Description : The reading at 'C' on the megger scale illustrated, is ________. EL-0044 A. 200,000 ohms B. 2,000,000 ohms C. 20,000,000 ohms D. 200,000,000 ohms

Last Answer : Answer: C

The reading at 'V' on the megger scale shown in the illustration, is __________. EL-0044 A. 40 meg ohms B. 0.40 meg ohms C. 4.0 kilo ohms D. 40,000 ohms

Description : The reading at 'V' on the megger scale shown in the illustration, is __________. EL-0044 A. 40 meg ohms B. 0.40 meg ohms C. 4.0 kilo ohms D. 40,000 ohms

Last Answer : Answer: D

The reading at 'P' on the megger scale shown in the illustration, is __________. EL-0044 A. 15 meg ohms B. 1.5 meg ohms C. 1.5 kilo ohms D. 150,000 ohms

Description : The reading at 'P' on the megger scale shown in the illustration, is __________. EL-0044 A. 15 meg ohms B. 1.5 meg ohms C. 1.5 kilo ohms D. 150,000 ohms

Last Answer : Answer: B

Which of the listed conditions could indicate the need for cleaning electrical insulation? A. Low ambient temperature B. Low operating temperature C. High dielectric strength D. Low megger readings

Description : Which of the listed conditions could indicate the need for cleaning electrical insulation? A. Low ambient temperature B. Low operating temperature C. High dielectric strength D. Low megger readings

Last Answer : Answer: D

Discharge switches are often located on hand-driven meggers. The purpose of these switches is to discharge capacitive charges stored in the _____________. A. megger hand generator B. megger movement coils C. tested equipment while conducting test D. tested equipment after testing

Description : Discharge switches are often located on hand-driven meggers. The purpose of these switches is to discharge capacitive charges stored in the _____________. A. megger hand generator B. megger movement coils C. tested equipment while conducting test D. tested equipment after testing

Last Answer : Answer: D

The need for insulation cleaning may be determined by _____. A. visual inspection for dirt accumulation B. high megger readings C. low operating temperature D. the time period since the last cleaning

Description : The need for insulation cleaning may be determined by _____. A. visual inspection for dirt accumulation B. high megger readings C. low operating temperature D. the time period since the last cleaning

Last Answer : Answer: A

If the pointer on a megger fails to return to 'zero' when not being used, the _____________. A. megger is out of calibration B. megger is operating normally C. hairsprings are burned out D. pointer probably stuck in that position

Description : If the pointer on a megger fails to return to 'zero' when not being used, the _____________. A. megger is out of calibration B. megger is operating normally C. hairsprings are burned out D. pointer probably stuck in that position

Last Answer : Answer: B

When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown control fuse C. a reading of 'zero' on a megger from one of the coil's leads to ground D. a higher-than-normal voltage reading across the winding

Description : When troubleshooting motor controllers, a shorted relay or contactor coil is often indicated by _______________. A. a resistance reading of 'infinity' on an ohmmeter B. charred insulation and/or a blown ... of the coil's leads to ground D. a higher-than-normal voltage reading across the winding

Last Answer : Answer: B

A useful instrument for checking A.C. motor performance by measuring possible unbalanced currents is the _____________. A. hand or battery-operated megger B. vibrating-reed frequency meter C. hook-on voltmeter-ammeter D. D'Arsonval iron-vane probe

Description : A useful instrument for checking A.C. motor performance by measuring possible unbalanced currents is the _____________. A. hand or battery-operated megger B. vibrating-reed frequency meter C. hook-on voltmeter-ammeter D. D'Arsonval iron-vane probe

Last Answer : Answer: C

Electrical machinery insulation will break down more rapidly due to _________________. A. low loading of motors and generators B. frequent megger testing C. high temperatures and vibration D. high operating frequencies

Description : Electrical machinery insulation will break down more rapidly due to _________________. A. low loading of motors and generators B. frequent megger testing C. high temperatures and vibration D. high operating frequencies

Last Answer : Answer: C

Routine maintenance of a ship's service alternator should include ______________. A. changing the pedestal bearing insulation yearly B. megger testing of all rectifying diodes C. lubricating excitation slip rings D. periodic cleaning of the air filters or screens

Description : Routine maintenance of a ship's service alternator should include ______________. A. changing the pedestal bearing insulation yearly B. megger testing of all rectifying diodes C. lubricating excitation slip rings D. periodic cleaning of the air filters or screens

Last Answer : Answer: D

A suspected 'open' in a motor field can be tested by using a/an ____________. A. potentiometer B. megger C. wattmeter D. ammeter

Description : A suspected 'open' in a motor field can be tested by using a/an ____________. A. potentiometer B. megger C. wattmeter D. ammeter

Last Answer : Answer: B

To determine if a stator coil is grounded, you should use a/an _____________. A. ammeter B. ground detection lamp C. magneto D. megger

Description : To determine if a stator coil is grounded, you should use a/an _____________. A. ammeter B. ground detection lamp C. magneto D. megger

Last Answer : Answer: D

If the pointer fails to return to zero when a megger is disconnected, the _____________. A. pointer is stuck B. hair springs are burned out C. megger is out of calibration D. megger is operating normally

Description : If the pointer fails to return to zero when a megger is disconnected, the _____________. A. pointer is stuck B. hair springs are burned out C. megger is out of calibration D. megger is operating normally

Last Answer : Answer: D

The electrician reports to you that he has obtained low (but above 1 megohm) megger readings on the windings of a deck winch motor. Upon checking the records of that motor, you find the readings have consistently been at that level for the last six yea A. motor be replaced B. windings be dried C. windings be cleaned D. readings are acceptable

Description : The electrician reports to you that he has obtained low (but above 1 megohm) megger readings on the windings of a deck winch motor. Upon checking the records of that motor, you find the readings have ... yea A. motor be replaced B. windings be dried C. windings be cleaned D. readings are acceptable

Last Answer : Answer: D

A generator has been exposed to water and is being checked for its safe operation. Therefore, it is necessary to _______________. A. check for shorted coils with a growler B. take moisture readings with a hydrometer C. test insulation values with a megger D. ground the commutator, or slip rings and run it at half load for 12 hours

Description : A generator has been exposed to water and is being checked for its safe operation. Therefore, it is necessary to _______________. A. check for shorted coils with a growler B. take moisture readings with a ... a megger D. ground the commutator, or slip rings and run it at half load for 12 hours

Last Answer : Answer: C

As shown in the illustration, what maintenance would be required of the circuit components? EL-0058 A. Change out both 'C' units monthly. B. Clean the glass surrounding 'E1' & 'E2' as needed. C. File the points at the upper end of 'G' every six months. D. Take megger readings on 'E1' & 'E2' windings quarterly.

Description : As shown in the illustration, what maintenance would be required of the circuit components? EL-0058 A. Change out both 'C' units monthly. B. Clean the glass surrounding 'E1' & 'E2' as needed. C. File ... upper end of 'G' every six months. D. Take megger readings on 'E1' & 'E2' windings quarterly.

Last Answer : Answer: B

As a general rule, the first troubleshooting action to be taken in checking faulty electric control devices is to _____________. A. draw a one line diagram of the circuitry B. test all fuses and measure the line voltage C. take megger readings D. insulate the apparatus from ground

Description : As a general rule, the first troubleshooting action to be taken in checking faulty electric control devices is to _____________. A. draw a one line diagram of the circuitry B. test all fuses and measure the line voltage C. take megger readings D. insulate the apparatus from ground

Last Answer : Answer: B

Different between megger and contact resistance meter?

Description : Different between megger and contact resistance meter?

Last Answer : Answers: Megger used to measure cable resistance, conductor continuity, phase identification where as contact resistance meter used to measure low resistance like relays ,contactors.

What is the difference between megger test equipment and contact resistance meter test instruments?

Description : What is the difference between megger test equipment and contact resistance meter test instruments?

Last Answer : Megger test equipment used to measure cable electric resistance, conductor continuity, phase identification. Contact resistance meter test instruments used to measure low resistance like relays, contactors.

What is Megger?

Description : What is Megger?

Last Answer : The megohmmeter, commonly called a megger for short, is used to measure very high resistance values. It is primarily used to test the insulation of conductors. To measure high resistance values, a high voltage is applied, either by the use of a handcranked generator or electronic power supply. 

Why megger value of 1 minute is less than 10-minute value?

Description : Why megger value of 1 minute is less than 10-minute value?

Last Answer : After 10 minutes the high voltage applied make the molecules such a way that stabilised in a good insulation. If insulation is weak it leads to more leakage current due to high potential. 

Different between megger and contact resistance meter?

Description : Different between megger and contact resistance meter?

Last Answer :  Megger used to measure cable resistance, conductor continuity, phase identification where as contact resistance meter used to measure low resistance like relays, contactors.

State functions of ; i) Cable box ii) Guard wire iii) Shackle insulator iv) Stay wire used in service connection

Description : State functions of ; i) Cable box ii) Guard wire iii) Shackle insulator iv) Stay wire used in service connection

Last Answer : i) Function of Cable box: To hold and inspect incoming and outgoing terminals  ii) Function of Guard wire : A grounded conductor placed beneath an overhead transmission line in order to ground ... in service connection: To give mechanical Support to pole, line and prevent leakage current if any

In accordance with Coast Guard Regulations (46 CFR), a steering gear feeder circuit from the emergency switchboard or alternate power supply must have the capacity for continuous operation of the rudder 15° side to side in not more than 60 seconds for a A. 1/4 hour B. 1/2 hour C. 1 hour D. 2 hours

Description : In accordance with Coast Guard Regulations (46 CFR), a steering gear feeder circuit from the emergency switchboard or alternate power supply must have the capacity for continuous operation of the rudder 15° side to side in not more than 60 seconds for a A. 1/4 hour B. 1/2 hour C. 1 hour D. 2 hours

Last Answer : Answer: B

According to Coast Guard Regulation (46 CFR) for emergency power and lighting systems, which of the listed items is the only permissible starting aid for the emergency diesel generator engine? A. Ether B. Lube oil heater C. Jacket water heater D. Fuel oil heater

Description : According to Coast Guard Regulation (46 CFR) for emergency power and lighting systems, which of the listed items is the only permissible starting aid for the emergency diesel generator engine? A. Ether B. Lube oil heater C. Jacket water heater D. Fuel oil heater

Last Answer : Answer: C

Coast Guard Regulations (46 CFR) require that each alternating current generator arranged for parallel operation shall be provided with _____________. A. more than one means of excitation B. individual circuit fuses C. a high back-pressure trip D. a reverse-power trip

Description : Coast Guard Regulations (46 CFR) require that each alternating current generator arranged for parallel operation shall be provided with _____________. A. more than one means of excitation B. individual circuit fuses C. a high back-pressure trip D. a reverse-power trip

Last Answer : Answer: D

Coast Guard Regulations (46 CFR 199) require that each lifesaving appliance, including lifeboat equipment, must be inspected at least once every _____________. A. week B. 2 weeks C. month D. 3 months

Description : Coast Guard Regulations (46 CFR 199) require that each lifesaving appliance, including lifeboat equipment, must be inspected at least once every _____________. A. week B. 2 weeks C. month D. 3 months

Last Answer : Answer: C

Coast Guard Regulations (46 CFR) require instrument and control wiring in a switchboard to be of what minimum size? A. 12 AWG B. 14 AWG C. 16 AWG D. 18 AWG

Description : Coast Guard Regulations (46 CFR) require instrument and control wiring in a switchboard to be of what minimum size? A. 12 AWG B. 14 AWG C. 16 AWG D. 18 AWG

Last Answer : Answer: B

According to Coast Guard Regulations (46 CFR), a battery installation must be in a room that is only for batteries or a box on deck. This would be termed a ____________. A. small installation B. moderate installation C. large installation D. high amp/hour capacity installation

Description : According to Coast Guard Regulations (46 CFR), a battery installation must be in a room that is only for batteries or a box on deck. This would be termed a ____________. A. small installation B. moderate installation C. large installation D. high amp/hour capacity installation

Last Answer : Answer: C

According to U. S. Coast Guard Regulations (46 CFR), the motor controller for a submersible electric motor driven bilge pump should be installed _____________. A. in the shaft alley B. at the submersible bilge pump C. above the uppermost continuous deck D. at the engine room emergency control panel

Description : According to U. S. Coast Guard Regulations (46 CFR), the motor controller for a submersible electric motor driven bilge pump should be installed _____________. A. in the shaft alley B. at the submersible bilge pump C. above the uppermost continuous deck D. at the engine room emergency control panel

Last Answer : Answer: C

Where automatic restart does not present a hazard after a power failure, Coast Guard Regulations (46 CFR) require motor controllers for auxiliaries vital to the propelling equipment to be provided with ________________. A. overload protection B. low voltage protection C. low voltage release D. reverse current protection

Description : Where automatic restart does not present a hazard after a power failure, Coast Guard Regulations (46 CFR) require motor controllers for auxiliaries vital to the propelling equipment to be provided ... overload protection B. low voltage protection C. low voltage release D. reverse current protection

Last Answer : Answer: C

According to Coast Guard Regulations (46 CFR), which of the following is an acceptable lining for battery trays containing alkaline batteries? A. Brass B. Lead C. Steel D. Zinc

Description : According to Coast Guard Regulations (46 CFR), which of the following is an acceptable lining for battery trays containing alkaline batteries? A. Brass B. Lead C. Steel D. Zinc

Last Answer : Answer: C

Coast Guard Regulations (46 CFR) require each switchboard to have ___________. A. non-conductive deck covering at the frount B. non-conductive deck coverings at the rear C. a name plate for each circuit breaker D. all the above

Description : Coast Guard Regulations (46 CFR) require each switchboard to have ___________. A. non-conductive deck covering at the frount B. non-conductive deck coverings at the rear C. a name plate for each circuit breaker D. all the above

Last Answer : Answer: D

When portable cords are connected to devices such as portable tools, you must eliminate direct tension on the joints or terminal screws. Coast Guard Regulations (46 CFR), allow this to be done by _____________. A. knotting the cords together at the plugs B. taping the plugs together C. installing a special fitting to eliminate plug separation D. all of the above

Description : When portable cords are connected to devices such as portable tools, you must eliminate direct tension on the joints or terminal screws. Coast Guard Regulations (46 CFR), allow this to be done by ... the plugs together C. installing a special fitting to eliminate plug separation D. all of the above

Last Answer : Answer: D

Coast Guard Regulations (46 CFR) require that the emergency diesel generator engine shut down when _____________. A. lubricating oil pressure is lost B. the engine overspeeds dangerously C. fixed CO2 is released into the emergency diesel generator space D. all of the above

Description : Coast Guard Regulations (46 CFR) require that the emergency diesel generator engine shut down when _____________. A. lubricating oil pressure is lost B. the engine overspeeds dangerously C. fixed CO2 is released into the emergency diesel generator space D. all of the above

Last Answer : Answer: D

Coast Guard Regulations (46 CFR) require that fire door holding and release systems are to comply with subpart _________. A. 111.15 B. 111.54 C. 111.99 D. 111.112

Description : Coast Guard Regulations (46 CFR) require that fire door holding and release systems are to comply with subpart _________. A. 111.15 B. 111.54 C. 111.99 D. 111.112

Last Answer : Answer: C

In accordance with Coast Guard Regulations (46 CFR), each battery operated relay-controlled lantern must _____________. A. be readily portable B. contain a dry cell battery having a minimum capacity of 10 amp hours C. have an automatic battery charger to maintain the battery in a fully charged state D. all of the above

Description : In accordance with Coast Guard Regulations (46 CFR), each battery operated relay-controlled lantern must _____________. A. be readily portable B. contain a dry cell battery having a minimum capacity of ... automatic battery charger to maintain the battery in a fully charged state D. all of the above

Last Answer : Answer: C