How does a megohmmeter measure a cable, and what is the insulation resistance of a cable measured by

The choice of megohmmeter: It is mainly to choose the voltage of the megohmmeter and its measurement range according to different electrical equipment. For electrical equipment with a rated voltage of less than 500V, a megohmmeter with a voltage level of 500V or 1000V should be selected; For electrical equipment with a rated voltage of more than 500V, a 1000-2500V megohmmeter meter should be selected, also known as a shake meter

How to use a megohmmeter when measuring the insulation resistance of a cable.

A megohmmeter has three binding posts: one with "L", one with "E", and one with "G" (shielded). When measuring the insulation resistance of power lines or lighting lines, "L" is connected to the line under test and "E" is connected to the ground wire.

When measuring the insulation resistance of the cable, in order to make the measurement result accurate and eliminate the measurement error caused by the leakage on the surface of the core insulation layer, the "g" should also be connected to the insulating paper of the cable.

Here are a few things to keep in mind when measuring:

1. To measure the insulation resistance of electrical equipment, the power supply must be cut off first, and the line must be discharged first when encountering equipment with capacitive properties, such as cables.

2. When the megohmmeter is used, it must be laid flat.

3. Before using the megohmmeter, turn it a few times to see if the pointer is at the maximum position, and then short circuit the two binding posts of "L" and "E", and slowly turn the handle of the megohmmeter to see if the pointer is at "zero".

4. The megohmmeter leads must be well insulated, and the two wires should not be twisted together.

5. When the megohmmeter is measured, the reading after one minute of rotation shall prevail.

6. When measuring, the megohmmeter revolution should reach 120 revolutions.

7. The range of the megohmmeter is often up to several gigaohms, and the minimum scale is about 1 megaohm, so it is not suitable for measuring the resistance below 100 kiloohms.

Ground-to-ground or wire-to-line testing.

The measured value of cable insulation resistance stipulates that the insulation resistance should be measured before the power cable is put into operation, and the value of the 1kV shake meter should be used below 1kv, and its value should not be less than 10m.

Use the shake meter above 1kv: The insulation resistance value of the cable of 3kv and below is not less than 200m.

6 The insulation resistance value of 10kV cable is not less than 400m.

20 The insulation resistance value of the 35kV cable is not less than 600m.

The insulation resistance value of 220kV cable is not less than 4500m km.

Safety Technical Methods for Measuring Insulation Resistance of Cables:

1. First of all, remove the installed cable from other equipment at the connection after full discharge, wipe the cable joint clean, and keep a certain safety distance from the equipment.

2. Measuring shake meter: 1kV megohmmeter for cables of 1kV and below, and 2500V megohmmeter for cables above 1kV.

3. Before the insulation of the underground rocking cable with gas, it is necessary to check the low pressure of gas concentration within 10 meters around the roadway before telemetry.

Connect the instrument's power plug to the AC220V. Press the power switch to the ON position, preheat for 10 minutes, and the test can be normal.

Select the appropriate test voltage (500V).

Determine whether the "test" light is off, make sure that the binding post is not charged, connect the test piece, press the "test" button, and the instrument can charge the test piece and measure.

After the test is completed, press the "RESET" button or the test time is until the instrument automatically resets, and then the test specimen can be removed.

Repeat the above steps for the next measurement.

This tester can be used after the power is turned on, but in order to ensure accuracy, please warm up for more than 10 minutes.

When connecting the object to be measured, it must be in the reset state, that is, when the test light is off, to prevent high-voltage electric shock.

When measuring more than 100m, it is best to shield the measuring line. When wiring, the grounding post on the front panel of the instrument should be connected to the housing or housing of the DUT.

Try to avoid measuring too small a resistor, or shorting the two test clips. Earth Resistance Tester Instruction Manual (I=10a,

The instrument is equipped with a pair (two groups) of test wires, red thick wire to red current binding post, red thin wire to red resistance binding post, black thick wire to black current binding post, black thin wire to black resistance binding post. 2. Connect the power plug of the instrument to AC220V. Press the power switch to the ON position, and the digital tube of each window will turn on.

3. Turn the current adjustment knob counterclockwise to the zero position. 4. Before the test, select the range. 5. The clamps of the two sets of test wires are short-circuited to each other.

6. Manual test.

One megaohm is equivalent to 1,000,000 ohms. Why do we need to measure such a high resistance? Don't think about measuring resistance, think of it as test equipment.

It specifically tests the insulation of the motor windings. Depending on the insulation rating of the motor, a good motor can measure megaohms or 1,000,000,000,000 ohms well!

This is an insulation test of the windings of a motor, commonly known as a megohmmeter, megohmmeter or megohmmeter motor. We are testing the insulation of the motor, more specifically the insulation between the motor windings and the motor housing. If a small fraction of the current is flowing, it can be measured by these highly sensitive meters.

Motor insulation is rated and manufactured to withstand different temperatures. Time and heat can break the insulation of the motor. Proper use of a megohmmeter will test any motor insulation.

Depending on the level of insulation you are testing, this will have an impact on the number of ohms that the meter should read. To test high-grade insulation, you should use a megohmmeter that is capable of testing megohms. Otherwise, your test may be unreliable or inaccurate.

Most drives and drives are very sensitive to insulation losses, and the drive can preemptively shut down the motor to prevent drive damage. Ensure that the motor rating meets the environmental requirements and check the heat rating and use factor.

Respondent: Huatian Power.

will be a megohmmeter. The "grounding" binding post (i.e., the E binding post) is reliably grounded (generally connected to a certain grounding body), and the "line" binding post (i.e., the L binding post) is connected to the line under test, as shown in the following figure.

Once connected, clockwise.

Shake the megohmmeter, the speed gradually increases, keep it at about 120 rpm and then shake it at a constant speed, when the speed is stable, the pointer of the watch is also stable, the value indicated by the pointer is the insulation resistance of the measured object.

Value. In actual use, the two binding posts of E and L can also be arbitrarily connected, that is, E can be connected with the measured object, and L can be connected with the grounding body (i.e., grounded), but the G binding post must not be connected wrong.

2) Measure the insulation resistance of the motor.

Connect the megohmmeter E binding post to the casing (i.e., grounding), and the L binding post is connected to the winding of a certain phase of the motor, as shown in the figure above, the measured insulation resistance value is the insulation resistance value of a certain phase to the ground.

3) Measure the insulation resistance of the cable.

When measuring the insulation resistance of the conductive core of the cable and the cable housing, the terminal post E is connected with the cable housing, and the terminal post L is connected with the wire core, and the terminal post G is connected with the insulation layer between the cable housing and the core at the same time, as shown in Figure C above. (such a multi-operation overall diagram).

1. The megohmmeter is used to detect the insulation resistance of electrical equipment, household appliances or electrical circuits to the ground and between phases, so as to ensure that these equipment, electrical appliances and circuits work in a normal state and avoid accidents such as electric shock and equipment damage.

2. The scale of the megohmmeter is measured in megohms (m). Megohmmeters are composed of medium and large-scale integrated circuits. The output power of this meter is large, the short-circuit current value is high, and the output voltage level is multi-level (each model has four voltage levels).