Question 1: How do I use a megger to test if a line is grounded? A megohmmeter, also called a megohmmeter, is an instrument used to measure the insulation resistance and high value resistance of the equipment under test. a hand-crank generator, a meter head and a It consists of three bonding terminals (i.e. L: line terminal, E: earth terminal, G: shield terminal ).
Megger, also known as megger, is used to test the insulation condition of electrical circuits or equipment. The usage method and precautions are as follows:
1. First, select a megometer suitable for the voltage level of the component under test. For electrical lines or equipment rated 500 V and below, a 500 V or 1000 V megometer should be used. For electrical lines or equipment above 500 V, a 1000 V or 2500 V megger should be used.
2. When testing the insulation of high voltage equipment with a megger, two people should do it.
3. Before measurement, the power supply of the circuit or electrical equipment under test must be completely disconnected, that is, it is not allowed to measure resistance insulation when the device is powered. And make sure no one is working on any wiring or electrical equipment before continuing.
4. The meter wire used by the megger must be an insulated wire and it is not suitable to use a double stranded insulated wire. The ends of the meter wires must have insulating jackets; L" of the megger. Ground terminal "E" should be connected to the measured phase of the equipment. Ground terminal "E" should be connected to the shell of the equipment and the unmeasured phase of the equipment The shield terminal “G” must be connected to the protective ring or the cable insulation sheath p.to reduce the impact of leakage current on the insulation surface. Error caused by measurement.
5. The megger should be checked for an open circuit before measuring. When the “L” end and “E” end of the megger are discharged, the shaker pointer should point to “∞” when the “L” end and “E” end of the megger are short-circuited. is shaken, the pointer should point to "0". This indicates that the megger is working well and can be used.
6. The circuit or electrical equipment under test must be grounded and discharged before testing. When testing a line, you must obtain permission from the other party before continuing.
7. When measuring, shake the scale handle at a uniform speed of 120 rpm; take the reading after maintaining a steady speed for 1 minute to avoid the influence of current draw.
8. During the test, both hands are not autored to touch both wires at the same time.
9. After the test is completed, the stitches should be removed first, and then stop shaking the watch. This helps prevent electrical equipment from charging the megger and damaging it.
10. During a lightning strike, it is strictly forbidden to test the insulation of the line.
Question set:
380 volt motors typically use 500 volt or 1000 volt meggers.
The megger relies on its own power output to generate current to measure resistance. The measured object should not be loaded and should be unloaded before testing, otherwise the test results will be affected.
What is the insulation resistance standard for measuring a load with a megger?
Generally, if the measurement exceeds 1 MΩ, it meets the insulation requirements of low-voltage equipment.
The current standard seems to be 380V 0.5 M or more. rootDetermined by the voltage, it can be explained by Ohm's law. This means that the voltage on the wire divided by the resistance of the insulation equals the current outside the wire. Just make sure it doesn't feel dangerous to the touch. About 1000 V = 1 M. How to use a megger to measure the resistance of the motor to determine the quality of the motor.
I will tell you how to determine the quality of the motor. After disassembling the connection parts, First, use a multimeter to measure the three-phase windings. If the resistance is passed, then use one lead from the megger to connect to the motor shell and use the other lead to measure if the resistance of all three. -phase to ground windings are normal. The minimum resistance value should not be less than 0.5 megohm3 if the resistance of the three-phase windings to earth is normal. The last step consistste to measure the phase between phases. Insulation resistance. Simply connect one lead of the megger to the terminal of one phase winding and connect the other lead to the other two terminals respectively. Be careful not to connect two wires at the same time after completing separate connections and measurements. , swap the oscillator leads to measure the other two phase windings. Measure only the upper or lower three terminals and the resistance should not be less than 0.5 megohms.
Attach one of the two oscillator test leads to the junction box terminal and attach the other to the case. Shake the oscillator handle evenly. The reading obtained is the insulation resistance of the. grounded motor. Generally, it is considered qualified if it is around 200K~2M.
Attach the two oscillator test leads to the terminals of the different phases in the junction box and shake the handle evenlyof the oscillator. The reading obtained is the insulation resistance between the motor phases. Generally, it is qualified if it is above 100K
Question 2: How to use the grounding megometer Friends, 1. The testing method of the grounding megometer ZZC29B-2 is as follows:
(1) When measuring the earth resistance at the two E-E terminals, short circuit it with a chrome-plated copper plate and connect it to the copper wire pure 5 m long supplied with the meter. The end of the wire is connected to the ground test point to be measured. When measuring the shield resistance, loosen the chrome copper plate, connect one terminal E to the ground body and the other terminal E to the shield.
(2) The P pillar is connected to the 20m pure copper wire supplied with the meter, and the other end of the wire is connected to the pin.
(3) The C pillar is connected to the 40m pure copper wire supplied with the meter, and the other exend of the wire is connected to pin 2.
2? Technical requirements for setting up the earth resistance tester
(1) The earth resistance tester should be placed 1-3m away from the test point, and the placement should be stable. and easy to use.
(2) The terminals of each terminal must be in good contact and firmly connected.
(3) The two grounding pins should be placed at a distance of 20m and 40m respectively from the grounding body to be measured; if the two pins are connected by a straight line, the grounding body to be measured; should basically be at It's a straight line.
(4) Other wires should not be used in place of those configured with the instrument. Pure copper wires 5m, 20m, 40m long.
(5) If the earth resistance tester is used as the center of the circle, the angle between the two pins and the tester should not be less than 120°, and incore less tuned in the same direction.
(6) The ground where the two pins are fixed must be solid and cannot be put in mud, embankment, next to tree roots, grass, etc.
(7) The soil resistance test can only be carried out after 7 consecutive sunny days after rain.
(8) The grounding body to be tested must first be derusted to ensure a reliable electrical connection.
3? Working Principles of Earth Resistance Tester
(1) Start measuring the earth resistance value only after the tester parameters meet the specifications.
(2) Before measurement, the earth resistance adjustment knob should be turned to the maximum speed, which is x10 speed, and the earth resistance value adjustment knob should be placed on the 6 ~ 7Ω position.
(3) Turn the handle slowly. If the galvanometer pointer quickly deviates towardsto the right of the 0 balance point in the middle, this means that the original range selection is too large. the range at x1, such as The deviation direction is as before, and the speed selection can be turned to the speed x0?1.
(4) After selection in step (3), slowly turn the handle. If the galvanometer pointer moves to the right from the balance point 0, it means that the ground resistance value is still too large. . While slowly turning the handle, the floor resistance knob should be turned slowly clockwise. When the galvanometer pointer returns to 0, gradually increase the handle speed until the handle speed reaches 120 rpm. the earth resistance
is multiplied by the gearing. The bit multiple is the measured earth resistance value of the earthing body. If the galvanometer pointer slowly deviates towards the gAlso, it means that the resistance value of the earth resistance button is lower than the actual earth resistance value. You can slowly turn it counterclockwise to increase the resistance indication value of the meter.
(5) If the galvanometer needle jumps irregularly when the handle is turned slowly, it means that the ground on the ground where the two grounding pins are fixed is not dense or there is a bad contact point. at one of the joints, in this case recheck two grounded pins or each connector.
(6) When measuring the soil resistance of a static pressure pile with a soil resistance measuring instrument, it is normal for the galvanometer needle to swing slightly toward the left and right at 0 o'clock.
(7) When the galvanometer pointer moves slowly towards the balance point 0, the poiGenerating the instrument generator can be accelerated. The rated speed of the handle is 120 rpm. It is strictly forbidden to accelerate the rotation of the handle when the galvanometer needle still deviates significantly.
(8) After use, the resistance value of the measuring instrument should be placed in the maximum position, which is the x10 position. Lay out the three test leads supplied with the instrument, clean the dirt on the two pins, and put them in a bag for storage.
2. The ZC29B test method is as follows:
(1) When measuring the earth resistance at the two terminals E-E, use a chrome-plated copper plate for the short circuit and connect it to the 5m long pure copper wire, the other end of the wire connect it to the grounding test point to be tested. When measuring the shield resistance, loosen the chrome copper plate, connect one terminal E to the ground body, and the other terminalE to shielding.
(2) The P pillar is connected to the 20m pure copper wire supplied with the meter, and the other end of the wire is connected to the pin.
(3) The C pillar is connected to the 40m pure copper wire supplied with the meter, and the other end of the wire is connected to pin 2.
2 ? Technical requirements for setting up the ground resistance tester
(1) The ground resistance tester should be placed 1-3m away from the test point, and the placement should be stable. .... ..>>
Question 3: How to use a megometer to measure whether the line is grounded If the electricity transmission and distribution line is grounded, you must use a megger. It is safe, compared to the earth resistance. If it is lower than the nominal value, it can be judged that there is a problem, and then it can be checked. Generally speaking, the nominal value is 1 MΩ/KV. For a 400 V line, use a mego500 V hmmeter. In theory, it should not be less than 0.5, but generally it is not less than 1 MΩ to be considered qualified.
This multimeter is really not good. The voltage of this battery is too low and the judgment is inaccurate.
Question 4: How to use a megger to measure grounding? The megger must be an insulation resistance meter. It measures megohms, and the maximum grounding resistance is only a few ohms. so you cannot use a megger to measure grounding. There is another type called a grounding resistance meter, which is also hand-cranked. It requires two auxiliary ground rods. You must read the instructions.
Question 5: Operation steps of earth resistance test megger 1. The meter terminal button wiring must be correct 2. Adjust the zero position mmechanics of the galvanometer after the meter is placed horizontally 3. "Set the magnification switch to the maximum magnification. Gradually increase the crank speed up to 150 rpm. When the pointer of the galvanometer deviates in a certain direction, turn the dial so that the pointer of the galvanometer points to the "0" point. At this time, the magnification gear on the dial corresponds to the measured resistance value 4. If the dial reading is less than 1 and the. balance has not been achieved, you can adjust the magnification switch to a smaller magnification until it is adjusted to complete balance 5. If the galvanometer pointer of the instrument shakes, the speed. crank can be changed to eliminate shaking 6. If the sensitivity of the instrument's galvanometer is too low, you can add water or salt water around the probe to moisten it. >
Question 6: How to measure soil resistance with a megometer A megometer cannot be used to measure soil resistance. To measure earth resistance, use an earth resistance measuring instrument. A megger, also called a megger, is used to measure insulation resistance. Usually, the insulation resistance of low-voltage electrical appliances cannot be less than 500,000 ohms. Therefore, the megohm meter's unit of measurement is the megohm, and one megohm is equal to 1,000,000 ohms. Earth resistance should generally be between 4 and 10 ohms, which cannot be measured with a megger.
Question 7: How to use the grounding meter? Using an oscillator
(1) Calibration of the counter. Before measuring, shake the meter and perform an open circuit and short circuit test on the meter to check whether the meter is in good condition. Open bothconnecting wires, shake the handle, the pointer should point to "∞", then short circuit the two connecting wires, the pointer should point to "0", if the above conditions are met, it is good, otherwise it cannot be used.
(2) the equipment under test is disconnected from the line and the large capacity equipment must be unloaded.
(3) Select a megger with a constant voltage level.
(4) When measuring insulation resistance, only terminals "l" and "e" are generally used, but when measuring insulation resistance of the cable at the earth or leakage current of the device under test is serious, it is necessary to use terminal "g", and connect terminal "g" to the shield or to the case. After the circuit is connected, you can turn the shake handle clockwise. Shaking speed should be slow to fast. When the rotation speed reaches approximately 120 revolutions per minute (typicalzc-25), continue rotating at a constant speed and read it. reading after 1 minute. Take the measurements by shaking and don't stop to read.
(5) Disconnect and discharge. Once the reading is complete, shake slowly while removing the wires, then discharge the device under test. The discharge method involves removing the ground wire used in the measurement from the megometer and shorting it to the device under test (not to the megometer discharge).
Question 8: How to connect the oscillating meter to the insulation ground with one end connected to the conductor and one end connected to the shell. Shake the oscillating meter handle. If the pointer points to zero, it means it is grounded; if there is a reading, it means it is well insulated. In real applications it is often compared to the relevant driver. If it is smaller, that means it is grounded.
How to use an melectronic egohmmeter (megohmmeter)?
The principle of the megometer:
Use a magnetoelectric ratio measuring mechanism.
Insulation resistance tester, also known as megohmmeter, megohmmeter and megohmmeter. The insulation resistance meter mainly consists of three parts. The first is a high voltage DC generator, used to generate high DC voltage. The second is the measurement loop. The third is the display.
In the previously mentioned megger (megger), the measuring circuit and the display part are combined into one. It is completed by a flow meter head composed of two coils with an included angle of 60° (approximately). One of the coils is parallel to both ends of the voltage and the other coil is in series with the measuring loop. . medium. The angle of deviation of the meter pointer is determined by the current ratio in the two coils. Different deviation anglesrepresent different resistance values, the higher the coil current in the measuring loop, the greater the deviation. pointer angle. Another method is to use a linear ammeter for measurement and display. Since the magnetic field in the coil is not uniform in the current ratiometer used previously, when the pointer is at infinity, the current coil is located exactly where the magnetic flux density is strongest. Therefore, even if the measured resistance is large, the current flowing through the current coil. Very rarely the coil deflection angle will be greater at this time. When the measured resistance is small or zero, the current flowing through the current coil is large and the coil has been deflected to a place where the magnetic flux density is small, and the deviation angle caused by this will not be very large. In this way, a corrnonlinear ection is obtained. Generally, the resistance display on the megger head should span several orders of magnitude. But this will not work when a linear ammeter is directly connected in series to the measuring loop. At high resistance values, the scales are all tightly packed and cannot be distinguished. In order to achieve nonlinear correction, nonlinear components must be added to the loop. measuring loop. This makes it possible to obtain a shunt effect when the resistance value is low. When the resistance is high, no shunt is generated, so the resistance value display reaches several orders of magnitude.
Instructions for use:
1. Before measurement, the megger should be held in a horizontal position, hold the meter body with your left hand and shake the megger rocker with your right. hand at a speed of approximately 120 rpm, the pointmeter must point towards infinity (∞), otherwise it means that the megger is defective.
2. Before measurement, the power supply to the electrical apparatus and the circuit under test should be cut off, and the relevant components should be temporarily grounded and discharged to ensure the safety of people, the megger and the accuracy. measurement results.
3. The wiring must be correct when measuring. The megger has three terminals (L, E, G). When measuring the resistance of the loop to ground, the L end is connected to the exposed conductor of the loop and the E end is connected to the ground wire or metal shell when measuring the resistance d 'loop isolation, the first and; the last ends of the loop are connected to L and E respectively; cable insulation is measured when measuring resistance, to prevent leakage current on the cable surface from affecting the accuracyWhen measuring, the shielding layer of the cable must be connected to terminal G.
4. The flexible measuring wire coming from the megger terminal should be well insulated and a proper distance should be maintained between the two wires and between the wire and the ground to avoid affecting the measurement accuracy.
5. When shaking the megger, do not touch the megger terminals and the circuit under test with your hands to avoid electric shock.
6. After shaking the megger, do not short the terminals to avoid damage.
7. Do not shake the megger for too long.
Key points for using the electronic megger:
1. Before measurement, the power supply to the equipment under test must be turned off and the device must be short-circuited and discharged to ground. Never allow the equipment to be powered for measurement to ensure the safety of people and equipment. For equipmentts likely to induce high voltage, this possibility must be eliminated before measurements can be made.
2. The surface of the object to be measured should be clean to reduce contact resistance and ensure the accuracy of the measurement results.
3. Before measurement, the megger should be subjected to open circuit and short circuit test to check whether the megger is in good condition. That is, before connecting the megger to the object to be measured, shake the handle so that the generator reaches the rated speed (120 rpm) and observe whether the pointer points to the “∞” position of the scale.
Short the “line (L) and ground (E)” terminal, slowly shake the handle and observe whether the pointer points to the “0” position of the scale. If the pointer cannot point to the finger position, it indicates that the megger is defective and needs to be repaired before use.
4. When using megohmbe, it must be placed in a stable and sturdy location, away from large external current conductors and external magnetic fields.
5. The wiring must be correct. There are generally three terminals on the megger, among which L is connected to the insulated conductive part between the tested object and the ground, and E is connected to the shell of the tested object or the ground.
G is connected to the shield of the object under test or No measured parts are required. When measuring insulation resistance, usually only the “L” and “E” terminals are used. However, when measuring the insulation resistance of the cable to ground or the leakage current of the device under test is serious, the "G" end should be used and the "G" end should be connected to the armor layer or hull. Once the lines are connected, you can turn the handle clockwise.
The stirring speed should be slowe to fast. When the rotation speed reaches approximately 120 revolutions per minute (ZC-25 model), continue rotating at a constant speed and take a reading after 1 minute. should be taken by shaking without stopping. Go down and do a reading.
6. Place the megger in a horizontal position during shake measurement and do not allow short circuit between the terminal knobs when the handle is turned. The handle should be shaken slowly and gradually. If the pointer is at zero, it means that the measured insulation may be short-circuited. At this time, the handle cannot be continued to prevent the coil inside the meter from heating. and damaged.
7. After reading, discharge the device under test. The discharge method involves removing the ground wire used when measuring from the megger and shorting it to the device under test (no discharging the megger).
Detailed informations:
Usage notes:
1 . It is prohibited to measure insulation resistance during lightning or near high voltage equipment. It can only be measured when the equipment is not charged and there is no induced electricity.
2. During the shake test, no one may work on the equipment under test.
3. The megger wires cannot be twisted together, but must be separated.
4. It is strictly forbidden to touch the megger with hands until it stops rotating or before the device under test is discharged. When removing the wires, do not touch the metal parts of the cables.
5. Large capacity equipment must be unloaded at the end of the measurement.
6. The flexible measuring wire coming from the megger terminal must be well insulated and a suitable distance must be maintained between the two wires and between the wire and theground to avoid affecting the measurement accuracy.
7. In order to avoid resistance leakage on the surface of the equipment under test, the intermediate layer of the equipment under test (such as the internal insulation between the cores of the cable shell) should be connected to the protection cable. sound when using a megger.
8. Check its accuracy regularly.
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