A megohmmeter is a device for measuring high resistances, or rather, for measuring insulation resistance. The megohmmeter consists of a voltage generator, an electrical value meter, and special output terminals. The instrument kit includes connecting wires with probes. Sometimes, for the convenience of measurements, crocodile clips are put on the probes.
The voltage generator of the megohmmeter is either driven by a special rotary handle, or powered by an external or internal power source and generates voltage when a special button is pressed. It all depends on the type of megaohmmeter.
The voltage that the megohmmeter is capable of generating has a standard value. Usually it is 500V, 1000V, 2500V. There are also megohmmeters with a test voltage of 100V and 250V.
The essence of the megohmmeter is as follows. When the handle of a conventional megohmmeter is rotated or when the button of an electronic megohmmeter is turned on, a high voltage is applied to the output terminals of the device, which is applied through the connecting wires to the measured circuit or to electrical equipment. In the process of measuring on the device, you can observe the value of the measured resistance. When measuring, the resistance value can reach several kiloohms, megaohms, or be equal to zero.
Because megohmmeters are capable of generating voltages up to 2500V, then only trained and well-trained workers are allowed to work with them.
Even if the megohmmeter used has been tested and verified, it is necessary to check its performance immediately before measuring the insulation resistance. To do this, first connect the connecting wires to the output terminals. Then these wires are short-circuited and the measurement is taken.
With shorted wires, the resistance value should be zero. This will be visible on the scale or on the display, depending on the type of instrument. If the connecting wires are shorted, the integrity of these wires is also checked.
Next, a measurement is made with shorted wires. If the device is working, then the value of the insulation resistance in this case will be equal to “infinity” (if the old-style megohmmeter), or it will take a large, but fixed value (if the device is electronic with a digital display).
Before measuring with a megohmmeter, it is necessary to study the electrical circuit in which measurements will be made. The electrical circuit may contain electrical appliances, electrical apparatus and other electrical and electronic equipment that is not designed for the output voltage that the megohmmeter generates. For this reason, it is necessary to protect this equipment from the effects of megger voltage. To do this, you need to perform actions for grounding, disconnecting or removing equipment from the circuit of the measured circuit.
At present, along with modern digital megohmmeters, old-style devices manufactured back in Soviet times are often used. Working with both types of devices, in principle, is not much different, although there are some differences in operation.
The common thing is that the connecting wires are initially connected to the output terminals (terminals) of the megohmmeter. Then the value of the test voltage is selected. To do this, on old-style devices, the output voltage switch is set to 500V, 1000V or 2500V.
It is worth noting that some devices are capable of generating only one voltage value.
On digital megohmmeters, the required test voltage is selected by special keys on the display.
The next step is to connect the connecting wires to the measured circuit (electric cable, electric motor, bus bar, power transformer) and directly measure the insulation resistance. The measurement is made within one minute.
Some differences when working with devices of different types:
Documentation of measurement results
In the process of measuring the insulation resistance, all measured values are recorded and then entered into a special measurement and test protocol, which is signed and sealed.
Megaohmmeter- This is a device for measuring insulation resistance, which supplies a constant voltage of 100, 250, 500, 1000, 2500, 5000V. This is a universal portable device, also designed for testing with increased voltage. Megohmmeter test the windings of electric motors, power cable lines, windings of turbogenerators and other electrical equipment. In general, wherever there is insulation, a megohmmeter is used. These devices are manual, digital, analog, electronic, mechanical, high-voltage.
The most common type of measurement in my practice is the measurement of insulation resistance. This type of measurement can be made on the cable (before and after), winding, electric motor, transformer, even in relay protection, the circuit has to be constantly measured. In general, on any electrical equipment that has insulation, it is necessary to monitor its value and identify possible inconsistencies in order to prevent possible adverse consequences for the equipment.
Let's talk about the physical model of insulation resistance. More details about classes and types of isolation will be written in a separate article. Let us clarify that the factors that spoil the insulation are the currents flowing in the equipment and overcurrents (starting, short circuit currents). In this article, I will focus on the insulation equivalent circuit. This will be a circuit consisting of two active resistances and two capacitances. This means that we have:
Why do you need to know this? Well, I don't know, maybe show off in front of people who don't know these basics. Or, to understand the nature of the passage of direct current through the insulation.
The first circuit consists of capacitance C1. This capacity is called geometric, it is characterized by the geometric characteristics of the insulation, its location relative to the ground. This capacitance is discharged instantly when the insulation is grounded after the test. The same bdysch, a spark when grounding is brought to the test phase after the experiment.
The second circuit has two elements in its composition - capacitance C2 and active resistance R2. This circuit simulates the loss when an AC voltage is applied to the insulation. R2 characterizes the structure and quality of the insulation. The more frayed the insulation, the lower the value of R2. The capacity C2 is called the absorption capacity. This capacitance is charged, when a constant voltage is applied, not instantly, but in a time proportional to the product of R2 by C2. The better the dielectric properties of the insulation, the longer the capacitance C2 will charge, because the value of R2 will be greater for healthy insulation. In general, this capacitance answers the question why, after a spark, it is necessary to keep grounding for a couple more minutes on the core under test. It discharges slowly and does not charge instantly.
The third branch consists of active resistance R3, which characterizes the insulation leakage current and losses. The current increases when the insulation is wetted, is proportional to the area of the insulation and inversely proportional to the thickness of the insulation. Here is such an electrical insulation model.
Let's talk about the history of the development of megaohmmeters. Where did such a name come from? Probably because of the name of the measured quantity. By the way, a megaohmmeter is also called a shrew, or they say to measure the chain. Familiar? It turns out, and you probably knew it, this name comes from the name of the oldest company for the production of measuring equipment called "Megger". This company appeared back in the 19th century, and the first testers were produced back in 1951.
The first megohmmeters, then still megohmmeters, were with handles. You turn the knob, a constant voltage is generated, and you make tests. It was necessary to twist with a frequency of 120 rpm. However, not everyone could spin for a long time. After all, measurements must be made for one minute to determine the absorption coefficient. Therefore, science stepped forward, and similar meggers appeared, but with mains power and a voltage supply button. Holding a button is much more convenient than turning a knob. However, there is an inconvenience in the sense that it is necessary to find .
However, progress did not stop there, and electronic megaohmmeters appeared. They are already backlit, it is not necessary to hold the power button throughout the test, however, when testing the cable, the residual capacitance can burn the device (well, I did not check it, but some engineers say so).
Attention, I'm telling the truth. I wrote more about this here, but I will repeat it again. Correctly, a device for measuring megaohms is called a megaohmmeter. Previously, it was called a megohmmeter (for example, in the 1966 book it is called that). New times, new rules. It is correct to call it a megaohmmeter, so let's use this name in our electrical life. And if a megger is an outdated name, then other interpretations are simply wrong and illiterate. Although it is possible, for example, to call old devices with a pen, produced in the Soviet Union, megohmmeters, and new digital ones, for example, electronic Sonel type, to be called megohmmeters. But this is my personal opinion, more like a joke than an opinion.
Let's start with the simple ones. So, the first participants in today's parade are Ukrainian devices and ESO 210/3G. The letter "G" indicates that the device is powered by an internal generator and has a handle. The model without handle works from 220V network and from the button. They are small in size and easy to use. These are the faithful assistants of power engineers. They are convenient to megerit any electrical equipment. And you can also take one of the ends after the test and ground it, because the ends on both sides have metal tips. In models with a handle, an alternator acts as a voltage source, in models with a button, a transformer that converts alternating voltage to direct voltage.
So, let's go through the settings of the device. The instrument can be tested by applying a constant voltage of 500, 1000 or 2500 volts. Readings appear on a pointer scale, which has several limits that are switched by a switch. These are the "I", "II" and "IIx10" scales.
The "I" scale is the lower digits of the upper scale. The countdown goes from right to left. Values from 0 to 50 MΩ.
Scale "II" - the upper digits of the upper scale. The countdown goes from left to right. Values from 50 MΩ to 10 GΩ.
The IIx10 scale is similar to the II scale, however, the values are from 500 MΩ to 100 GΩ.
The device also has a lower scale from 0 to 600 V. This scale is available in the ESO-210/3 device and, when the voltage supply button is not pressed, shows the voltage at the ends. In general, they brought the ends of the megohmmeter to the outlet, and the arrow rose to 220V. But it is only necessary to connect them correctly to measure voltage, and not insulation resistance. One for the zipper and one for the Ux.
When voltage is applied, the red light on the scale lights up, which indicates the presence of voltage at the ends of the device.
How to connect the probes of the device? We have three holes for connecting probes - a screen, a high voltage and a third measuring one (rx, u). In general, two probes are paired and one of them is signed. It is not easy for an attentive person to make a mistake.
Let's take a step further and stop our eyes on a powerful Polish device called Sonel - megohmmeter mic-2510. This megger is digital. Outwardly, it is very nice, the kit includes a bag in which crocodile-type probes (quite powerful and reliable) and plug-in probes are folded. In addition, a charger is included in the package. The device itself is battery operated, which is quite convenient. It does not require a network connection and does not require the rotation of the handle, like the old models of domestic megohm meters. There is also a ribbon for a comfortable fit around the neck. At first, it seemed to me not very convenient, but in the end you get used to it and realize all the advantages. In addition to a reliable battery, the pluses include the ability to supply voltage without maintaining a button. To do this, first you press start, then "enter" and that's it - follow the readings and do not let anyone energized.
This device can measure the following quantities in two-wire and three-wire methods. The three-wire method is used for measurements where it is necessary to exclude the influence of surface currents - transformers, cables with a screen.
Also, the device can measure temperature using temperature sensors, voltage up to 600 volts, low-resistance contacts.
The scale of the device has the values 100, 250, 500, 1000, 2500 Volts. This is a wide enough range that can satisfy the needs of engineers when conducting a wide variety of tests. From the absorption coefficient to the polarization coefficient. The maximum measurable insulation resistance that the device is able to measure is 2000 GΩ - an impressive value.
The polarization coefficient characterizes the degree of aging of the insulation. The smaller it is, the more the insulation is worn out. The polarization coefficient at 2500V and measure the insulation resistance after 60 and 600s or after 1 and 10 minutes. If it is more than two, then everything is fine, if from 1 to 2 - then the isolation is doubtful, if the polarization coefficient is less than 1 - it's time to sound the alarm. Western chief engineers do not welcome high-voltage tests by the same AID, but are happy to conduct a vicious test at 5kV or 2.5kV with the measurement of this coefficient.
The absorption coefficient is the ratio of the insulation resistance after 60 and 15 seconds. This coefficient characterizes the moisture content of the insulation. If it tends to unity, then it is necessary to raise the issue of drying the insulation. For more information about its value for different types of equipment, please refer to your country's electrical test code.
In the course of my work, I met with other devices, but these two show how far progress has come in the production of megohmmeters. Each of the devices I have seen has its pros and cons.
How are insulation resistance measurements made (the most popular measurement, which is performed with a megaohmmeter) for various electrical equipment. Consider how to test, using the example of the power system of the Republic of Belarus. Although, the rules are basically the same, with minimal differences.
Before starting the measurement, it is necessary to check that the device is working, for this it is necessary to supply voltage with shorted ends and closed ones. When closed, we should get "0", and when open, we should have infinity (since we measure the resistance of air insulation). Next, we plant one end on the ground (grounding bolt, busbar, grounded equipment case), and the other on the tested phase, winding. Two people make tests, one holds the ends, and the second applies voltage. The reading is recorded after 15 seconds and after 60. At the end, the core to which the voltage was applied is grounded and after a minute or two (depending on the magnitude and time of the voltage supply), the ends are removed and measurements are made on the other core in a similar way.
How to ring anything with a megohmmeter, continuity is a check for the integrity of the circuit. Continuity is the first electrician's device, which he must assemble himself from a light bulb, a battery and wires. How to ring with a megaohmmeter? The megohmmeter does not quite ring, it shows that there is no connection between the phase and the ground, that is, the absence of a winding short to ground. However, if a large voltage is applied, then it is quite possible to burn the relay or motor winding.
So, we are approaching the electric motor, for example, this is a 380-volt motor of some kind of pump. Remove the cover, disconnect the power cable. Next, we apply 500V and look. If at the end of a minute the resistance is less than 1 MΩ, then it does not meet the standards. The absorption coefficient is not standardized for small electric motors. Voltage is applied between one phase and ground. The other two phases are connected to the body. At the end of the test, the tested core is grounded.
So we have a cable. On the one hand, for example, it is connected to a starter, and on the other hand, to an electric motor or a drive that starts the electric motor. We need to mega this cable. We disconnect it from the starter and from the electric motor. We put a person at the electric motor, if he is in another room, so that he does not let anyone near the open veins that we will test. Next, we apply a voltage between the core and the ground of 2500 V for a minute. The value of insulation resistance for cables with voltage up to 1000V must be at least 0.5 MΩ. For cables with voltages above 1 kV, the insulation resistance value is not standardized. If the megaohmmeter shows zero, then the core is broken and damage must be sought. The insulation resistance between the conductors is also measured. Or they combine three cores and to the ground, and if the value is inadequate, then it is already necessary to measure each core to the ground separately.
Also, at the end of the test, it is necessary to hang a ground wire on it before removing the wire through which voltage was applied. The more voltage applied, the longer the wait. For high-voltage cables, this time reaches several minutes.
Since the megohmmeter supplies high voltage, it is a potential source of danger both for those who supply this voltage and for those who are near the equipment, the cable to which this voltage is applied.
What should be remembered when working with a megohmmeter? Firstly, it is necessary to correctly connect the ends to the device, and secondly, it is necessary to securely fasten the ends through which voltage is supplied to the electrical equipment. Also, do not forget about the grounding of the equipment under test, both before the measurement and at the end to remove the residual charge.
About tricks with a megaohmmeter, I can only note that we have one worker whom we hacked at 500 volts, here, as he says, the main thing is to keep the ends tight and not let go. Attention!!! I don't recommend you do this!!!. The spectacle was creepy, of course. And theoretically, the current is small and the thermal effect does not bother.
In general, I wish you good luck in your work with a megaohmmeter, and be careful, because our profession is not only very interesting, but also quite dangerous. TV above all!!!
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The safety of operation of domestic or industrial electrical installations depends on the state of insulation of the conductors in them. In our country, there is a network of specialized laboratories whose task is to regularly check enterprises and housing.
One of the devices that is widely used by employees of these organizations is a megaohmmeter. The device received this name due to its features and its functional purpose. Among other employees of our company, I am engaged in complex testing of electrical devices of various types and classes. Each category has its own measurement programs. One of the most important characteristics of electrical equipment is the insulation resistance of power and other circuits. The minimum allowable values of this indicator for each group of current consumers are defined in GOST 183-74.
The insulation resistance is not a constant value and depends on many factors:
Reducing the insulation resistance can lead to rather unpleasant consequences. This can be, among other things, dangerous for the lives of people who are in direct contact with the operation of electrical appliances. A breakdown of the dielectric can lead to a short circuit between the windings or the appearance of voltage on the equipment case. This leads, in turn, to the failure of the device or to the possibility of electric shock to a person.
In our laboratory, various types of megohmmeters and modern digital time-tested analog devices are used. The operation of the device is based on measuring the strength of current and voltage, the result is obtained in the form of a ratio of these quantities. A megohmmeter is used to test the resistance of the windings of electrical machines or devices. To perform its functions, it is equipped with a power source.
In devices of old designs, this is a DC generator. We still use the M1101M device, which was made almost half a century ago. To bring it into action, you need to turn the handle of the dynamo that produces direct current. Despite its venerable age, this device still shows a fairly high accuracy at a maximum voltage value of 1000 V.
Modern electronic devices do not have electromechanical generators, and galvanic cells or batteries are used as current sources. Such devices are more convenient in operation, there is no need to turn the handle of the dynamo during the checks. Digital megohmmeters have storage devices and are able to record the results of measurements.
Our company uses the product E6-32, which, in addition to all other advantages, is also a voltmeter. In the instrumentation engineer's job, instrument versatility is critical. The mentioned device is used to perform tests on electrical networks and non-energized devices. The multimeter is designed for a maximum voltage of 700 V.
The E6-32 megohmmeter has a rubberized housing that is comfortable to hold in the process with one hand. The control keys are under an elastic polymer coating, their location is well thought out. In general, the device is compact and ergonomic, can be carried in the pockets of clothes, freeing up the hands. This device is relatively inexpensive and, importantly, has fairly high technical characteristics.
In the process of testing various installations, we apply approved methods. To obtain reliable results, employees first study the technical documentation for the product. The fact is that the nominal value of the voltage during the test must correspond to the class of electrical equipment. In other words, if the device is designed to work in household networks, then the tests are carried out with a device with a maximum voltage of 250 V.
Such checks are typical for residential, office and industrial premises. In order to avoid electric shock during insulation breakdown, the wiring in them must be equipped with grounding. This circuit is also subject to mandatory verification. At the same time, you often have to work in open areas and in different climatic conditions. Our equipment is reliably protected from external influences.
Especially, in this regard, modern digital measuring instruments, both imported and Russian, stand out. Their distinctive feature is the ability to select the required test range. At the same time, the results of such tests have a very high accuracy. The practice of using devices of this class can significantly reduce labor costs during verification work.
It is known that the value of insulation resistance changes not only under the influence of external conditions: temperature and humidity, but also during long-term operation of the equipment. to improve the reliability of studies, it is recommended that measurements be taken no earlier than 60 seconds after the rated voltage is applied to the installation. This approach makes it possible to bring the test conditions as close as possible to real ones.
Comparative tests show relatively small errors when using both devices. The use of a specific type of meters is rather a matter of habit, although, in my opinion, digital readings are more convenient for fixing and processing.
An integral part and indicator of the electrical network is such a thing as isolation. The protective sheath of the wire or cable, the electrical insulator of the overhead line, the insulator of the transformer terminals and other devices prevent the electric current from contacting where we do not need. The insulating sheath provides protection against short circuit, fire, breakdown on the body of an electrical device or machine, as well as protection of a person from electric shock. However, the insulation is subject to external factors such as time, sun, frost, water, mechanical wear, contact with aggressive media. In order to detect a defect in time, there is a device - a megaohmmeter. How to use this device, we will describe further, providing a method for measuring insulation resistance with a megohmmeter.
The megohmmeter generates voltage with its own high-voltage converter, and the milliammeter records the current in the measured circuit. From the school physics course, we know , and the relationship between the resistance R, which is equal to U divided by I.
At present, digital measuring instruments have become widespread due to their compactness and lightness, but pointer models with a manual dynamo still go along with them. Now we will consider how to properly use the old-style megger and the new one.
We draw your attention to the fact that some people call the device for measuring insulation resistance a megger. This is not quite the right name, because. if you break the word into parts, you get the prefix "mega", the unit of measurement is "ohm" and "meter" (translated from Greek as a measure).
Checking the insulation resistance is carried out on de-energized equipment or cable line, electrical wiring. Remember that the device generates high voltage and if safety measures for using a megohmmeter are violated, electrical injury is possible, because. Measuring the insulation of a capacitor or a long cable line can lead to the accumulation of a dangerous charge. Therefore, the test is carried out by a team of two people who have an idea about the danger of electric current and have received a safety clearance. During the test of the object, no unauthorized persons should be nearby. Be aware of high voltage.
Each time the device is inspected for integrity, for the absence of chips and damaged insulation on the measuring probes. Trial testing is carried out by testing with divorced and closed probes. If tests are carried out with a mechanical device, then it must be placed on a horizontal, even surface so that there is no measurement error. When measuring insulation resistance with an old-style megohmmeter, you need to rotate the generator knob at a constant frequency, approximately 120-140 rpm.
If you measure resistance relative to the case or ground, two probes are used. When testing the cable cores relative to each other, you need to use the “E” terminal of the megohmmeter and the cable screen to compensate for leakage currents.
The insulation resistance does not have a constant value and largely depends on external factors, so it may vary during the measurement. The check is carried out for at least 60 seconds, starting from 15 seconds, readings are recorded.
For domestic networks, tests are carried out with a voltage of 500 volts. Industrial networks and devices are tested with voltage in the range of 1000-2000 volts. What kind of measurement limit to use, you need to find out in the operating instructions. The minimum allowable resistance value for networks up to 1000 volts is 0.5 MΩ. For industrial devices, no less than 1 MΩ.
As for the measurement technology itself, you need to use a megohmmeter according to the method described below. For example, we took the situation with the measurement of insulation in the SC (power shield). So, the procedure is as follows:
At the end of the test, we remove the residual charge from the object, by means of a short circuit, and the measuring device itself, discharging the probes among themselves. Here, according to such instructions, it is necessary to use a megohmmeter when measuring the insulation resistance of cable and other lines. To make it easier for you to understand the information, below we have provided videos that clearly demonstrate the measurement procedure when working with certain models of devices.
First of all, we bring to your attention the instruction manual for the ES0202 / 2-G pointer megohmmeter:
Working with an old model
Another popular pointer meter, which is an analogue of the above model, is the m4100. Using it is also quite simple, as you can see by watching this video:
How to use m4100
Digital megohmmeters with a display are even easier to use. For example, to measure the insulation resistance of a cable with a modern meter UT512 UNI-T is possible using this technology:
Instruction manual for digital model
Well, the last instruction concerns another popular device - E6-32. The video below shows in sufficient detail how to use a megaohmmeter to measure the insulation resistance of a transformer, cable, and even a metal connection:
Application of E6-32
Here, according to this method, insulation resistance is measured with a megohmmeter. As you can see, using this device is not difficult, but you need to take safety precautions seriously and take all necessary protective measures.
All electrical installations and systems in operation require mandatory electrical measurements to determine the general condition, safety and operability of electrical networks, including testing insulation resistance parameters. For these measurements, you will need to work with a megohmmeter, a device designed to detect insulation defects in a timely manner. To use a megohmmeter, it is necessary to study its technical characteristics, principle of operation, device and specific features.
A megohmmeter is a device designed to measure large resistance values. Its distinguishing feature is the performance of measurements at high voltages generated by its own converter up to 2500 volts (the voltage value is different in different models). The device is often used to measure the insulation resistance of cable products.
Regardless of the type, the megohmmeter device consists of the following elements:
Working with a megaohmmeter is possible thanks to Ohm's law: I = U / R. The device measures the electric current between two connected objects (eg 2 strands of wire, strand to earth). Measurements are carried out with calibrated voltage: given the known values of current and voltage, the device determines the insulation resistance.
Most megaohmmeter models have 3 output terminals: ground (Z), line (L); screen (E). Terminals Z and L are used for all measurements of the device, E is intended for measurements between two similar current-carrying parts.
There are two types of megaohmmeters on the market today: analog and digital:
To work with the device, you need to know how to measure the insulation resistance with a megohmmeter.
The whole process can be conditionally divided into 3 stages.
Preparatory. During this stage, it is necessary to verify the qualifications of the performers (specialists with an electrical safety group of at least 3 are allowed to work with a megger), resolve other organizational issues, study the electrical circuit and turn off electrical equipment, prepare devices and protective equipment.
Basic. Within this stage, in order to correctly and safely measure the insulation resistance, the following procedure for working with a megohmmeter is provided:
Final. At this stage, the equipment is prepared for voltage supply and documentation for measurements is drawn up.
Before proceeding with measurements, you need to make sure that the device is working!
There is a way to check the megohmmeter for serviceability. It is necessary to connect wires to the terminals of the device and short-circuit the output ends. Then a voltage supply is required, and the results must be monitored. A working megohmmeter when measuring a shorted circuit shows the result "0". Then the ends are separated and repeated measurements are taken. The screen should display “∞”. This is the insulation resistance value of the air gap between the output ends of the instrument. Based on the values of these measurements, we can conclude that the device is ready for operation and its serviceability.
Before starting work with a resistance meter, you must familiarize yourself with the safety precautions when using a megohmmeter.
There are a number of basic rules:
To perform work with a megohmmeter in electrical installations, the device must pass the appropriate tests and be verified.
With the help of a megohmmeter, the resistance of cable products is often measured. Even for novice electricians, with the ability to use the device, it will not be difficult to check a single-core cable. Testing a multi-core cable will require a lot of time, as measurements are made for each core. In this case, the remaining cores are combined into a bundle.
If the cable is already in operation, before starting to measure the insulation resistance, it must be disconnected from the power supply and the load connected to it must be removed.
The control voltage during cable continuity with a megohmmet depends on the voltage of the network in which the cable is operated. For example, if the wire operates at a voltage of 220 or 380 volts, then for measurements it is necessary to set the voltage to 1000 volts.
To perform measurements, one probe must be connected to the cable core, the other to the armor, and then apply voltage. If the measurement value is less than 500 kΩ, then the wire insulation is damaged.
Before proceeding to check the electric motor with a megohmmeter, it must be de-energized. To perform work, it is necessary to provide access to the terminals of the windings. If the operating voltage of the electric motor is 1000 volts, it is worth setting 500 volts for measurements. For measurements, one probe must be connected to the motor housing, the other in turn to each output. To check the connection of the windings to each other, the probes are installed simultaneously on pairs of windings. Contact should be with metal without traces of paint and rust.
This is an informational article that is for informational purposes only. More detailed and accurate information is contained in the instructions for the use of meggers, technical and regulatory documents.
