Test method for cable 0 4 sq. Standards for acceptance testing of power cable lines

Getting started cable insulation resistance measurement It is important to take into account the temperature indicators of the environment. Why is this so?

This is due to the fact that at sub-zero temperatures, the water molecules in the cable mass will be in a frozen state, actually in the form of ice. And as you know, ice is a dielectric and does not conduct current.

So, when determining the insulation resistance at sub-zero temperatures, it is these particles of frozen water that will not be detected.

To calculate the conductor resistance, you can use the conductor resistance calculator.

Instruments and means for measuring cable insulation resistance.

The next point when measuring the insulation resistance of cable lines will be the measuring instruments themselves.

The most popular device for measuring insulation resistance among our electrical laboratory workers is the MIC-2500 device.

Using this device manufactured by Sonel, you can not only take measurements of the resistance of cable lines, cords, wires, electrical equipment (transformers, switches, motors, etc.), but also determine the level of wear and moisture level of the insulation.

It is worth noting that it is the MIC-2500 device that is included in the state register of approved insulation resistance measurements.

According to the instructions, the MIC-2500 device must undergo annual state verification. After the verification procedure, a hologram and a stamp are applied to the device, which confirm the verification. The stamp contains information about the date of scheduled verification and the serial number of the measuring device.

Only serviceable and verified instruments are allowed to work with insulation resistance measurements.

Insulation resistance standards for various cables.

To determine the standard cable insulation resistance, you need to classify them. Cables according to their functional purpose are divided into:

above 1000 (V) - high-voltage power
below 1000 (V) - low-voltage power
control cables - (protection and automation circuits, secondary switchgear circuits, control circuits, power supply circuits for electric drives of switches, separators, short circuiters, etc.)

Insulation resistance measurement for both high-voltage cables and low-voltage cables is carried out with a megohmmeter for a voltage of 2500 (V). And control cables are measured at a voltage of 500-2500 (V).

Each cable has its own insulation resistance standards. According to PTEEP and PUE.

High-voltage power cables above 1000 (V) - the insulation resistance must reach at least 10 (MΩ)

Low voltage power cables below 1000 (V) - insulation resistance should not fall below 0.5 (MΩ)

Control cables - insulation resistance should not fall below 1 (MΩ)

Algorithm for measuring the insulation resistance of high-voltage power cables.

To understand and simplify the process of performing measurement work insulation resistance in high voltage power cables, we recommend the procedure for taking measurements.

1. Check the absence of voltage on the cable using a high voltage indicator

2. We install a test ground using special clamps on the cable conductors on the side where we will carry out the measurement.

3. On the other side of the cable we leave free conductors, while we separate them at a sufficient distance from each other.

4. We place warning information posters. It is advisable to place a person on the other side to monitor safety while measuring with a megohmmeter.

5. We measure each core for 1 minute with a 2500 (V) megohmmeter to obtain the indicators insulation resistance of the power cable.

For example, we measure the insulation resistance on the conductor of phase “C”. At the same time, we place the grounding on the conductors of phases “B” and “A”. We connect one end of the megohmmeter to grounding, or, more simply, to “ground”. The second end is to the core of phase “C”.

Visually it looks like this:

6. We record measurement data in the process of work in a notebook.

Methodology for measuring insulation resistance of low-voltage power cables.

As for measuring the insulation of low-voltage power cables, the measurement technique differs slightly from that described above.

Likewise:

1. We check that there is no voltage on the cable using protective equipment designed for work in electrical installations.

2. On the other side of the cable, we separate the conductors at a sufficient distance from each other and leave them free.

3. We place prohibition and warning posters. We leave a person on the other side to monitor safety.

4.Measurement insulation resistance of low voltage power cable run a megohmmeter at 2500 (V) for 1 minute:

between phase conductors (A-B, B-C, A-C)
between phase conductors and zero (A-N, B-N, C-N)
between phase conductors and ground (A-PE, B-PE, C-PE), if the cable is five-core
between zero and ground (N-PE), having previously disconnected zero from the zero bus

6. We record the obtained insulation resistance measurements in a notebook.

Methodology for measuring the insulation resistance of control cables.

A special feature of measuring the insulation resistance of control cables is that the cable cores can not be disconnected from the circuit and measurements can be taken together with the electrical equipment.

The insulation resistance of the control cable is measured using a familiar algorithm.

1. We check that there is no voltage on the cable using protective equipment that is designed for work in electrical installations.

2. We measure the insulation resistance of the control cable with a megohmmeter of 500-2500 (V) in the following sequence.

First, we connect one terminal of the megohmmeter to the core being tested. We connect the remaining conductors of the control cable to each other and to the ground. To the second terminal of the megohmmeter we connect either the ground or any other non-tested conductor.

We take 1 minute to measure the core being tested. Then we return this core to the rest of the cable cores and measure each core one by one.

3. We record all the obtained indicators for measuring the insulation resistance of the control cable in a notebook.

Protocol for measuring cable insulation resistance.

All of the above electrical measurements, after obtaining cable insulation resistance data, must be subjected to a comparative analysis with the requirements and standards of PUE and PTEEP. Based on the comparison, it is necessary to formulate a conclusion about the suitability of the cable for subsequent operation and draw up a protocol for measuring insulation resistance.

The resistance of a cable's insulating layer is one of the most important parameters of its performance. If you bought a cable and it was stored in a warehouse for some time, do not think that its insulation will be the same as when you bought it. Insulation can deteriorate both under unsatisfactory storage conditions and during operation and installation. In order to identify all possible problems, the cable insulation is checked with a megohmmeter.

Causes of poor cable insulation

There are several factors affecting the insulating properties of cables:

In order to identify an insulation problem in time, you will need a special device - a megohmmeter. These devices are of the old type (mechanical, where you need to rotate the handle):

and a new model - electronic:

Let's consider the operation of these devices.

Safety rules

Checking the cable insulation with a megohmmeter is carried out only with the equipment disconnected and de-energized.

The megaohmmeter is capable of producing high voltage (certain types up to 5000 Volts), so when working with it, strictly follow the following rules:

Preparatory work

The cable under test must be prepared before testing.

To do this:

⚡ check that there is no voltage on the cable cores
⚡ long cables may have induced or residual voltage
Therefore, before each measurement, using a separate piece of wire or portable grounding, wearing dielectric gloves, it is necessary to touch the core and the grounded body or grounding loop to remove this charge;
⚡ disconnect the cable from the connected equipment.
This must be done so that when checking the cable insulation with a megohmmeter, only the cable itself is involved in the test, without the equipment or machines to which it is connected. Disconnection must be done on both sides of the cable. Sometimes this is not done to speed up work. First, a measurement is taken, and if it shows a negative result, then only after that the wires are pulled back.

Checking the megohmmeter

Before checking the cable insulation with a megohmmeter, it is necessary to test the operation of the device itself.
Here's how to do it on the M4100 megohmmeter. The device has 2 scales: the upper one for measurements in megaohms and the lower one for measurements in kiloohms.

To work in megaohms:

⚡ connect the ends of the probe wires to the two left terminals. The probes must be open;
⚡ rotate the knob and watch the arrow readings. If the device is working properly, it will tend to the left - towards infinity;
⚡ close the probes together. When you rotate the knob, the arrow should deflect to the right to zero.

To work in kilo-ohms:

⚡ Place a jumper between the 2 left terminals and connect one of the ends there. The second end is connected to the rightmost terminal. The probes are open;
⚡ Rotate the knob and watch the readings. When the device is working properly, the arrow deviates as far as possible to the right;
⚡ After closing the probes and rotating the knob, the arrow will tend to zero on the lower scale (i.e. to the left).

Working with megaohmmeter M4100

First of all, check that there is no voltage on the cable
ground all conductors
place the device on a flat surface
When measuring conductor insulation to ground, one of the probes is connected to the wire, the other to the armor or grounding device. Then remove the grounding only from the core being measured;
Rotate the knob evenly for 60 seconds. Rotation speed is two revolutions per second. At 60 seconds, note the readings of the device;
after each measurement, remove the residual charge from the core and wires of the megohmmeter by touching them to ground.

It is enough to test household networks and home wiring with a voltage of 500 Volts. The minimum value that a cable insulation test with a megohmmeter should show in this case is 0.5 mOhm.

In industrial power networks, cables are tested with 2500 Volt megaohmmeters. The insulation resistance must be at least 10 mOhm.

Working with an electronic megohmmeter

How often is cable insulation checked with a megameter?

The first measurement is taken at the manufacturer's factory
Before installation on site
After installation before applying voltage
During operation, when defects are detected or during maintenance, once every three years.

⚡ some people get confused with the scales of the M4100 device. Where is the measurement scale in megaohms located, and where in kiloohms? In order not to forget, use the hint: megaohm (mOhm) as a unit of measurement is higher than kiloohm (kOhm), respectively, and its scale is higher!
⚡ Before measuring, clean the ends of the cable cores from dirt. Dirty insulation may give poor results, although the cable itself will be fine;
⚡ The measuring leads of the megohmmeter itself must have an insulation of at least 10 mOhm. Do not use strange scraps or pieces of old wires. You will only worsen the measurement readings and will not know the exact results;
⚡ when checking a cable in the circuit of which there is a meter, be sure to disconnect all phase conductors and the neutral conductor from the housing or busbar. Otherwise, due to the metering device, you will have megohmmeter readings as if the cable cores are short-circuiting among themselves;
⚡ If you sequentially measure individual sections of wiring, always disconnect the neutral conductors from the common bus. Otherwise, you will get the same measurements on all cables. And these results will be equal to the worst resistance of one of the connected cables;
⚡ if the cable is long (more than 1 km), with a large capacity, then the residual charge must be removed using a special rod. Otherwise you can create a big “boom” right before your eyes;
⚡ When taking measurements in lighting networks, unscrew the incandescent light bulbs from the lamps and leave the switches themselves turned on. For gas-discharge lamps, measurements can be carried out without removing the lamps from their housings, but with the obligatory unscrewing of the starter.

The quality of the cable insulation layer greatly affects the reliability of the electrical installation as a whole. It can change both during production at the factory and during storage, transportation, installation of the circuit, and, especially, during its operation.

For example, moisture that gets inside the insulation at subzero temperatures will freeze and change its electrically conductive properties. Determining its presence in this situation is very problematic.

Types of checks

Constant attention is paid to the quality of insulation, which is implemented comprehensively:

periodic mandatory inspections by trained personnel;

automatic tracking by special monitoring devices during the execution of a constant technological cycle.

During cable assessment, personnel determine its mechanical condition and check its electrical characteristics.

During an external inspection, which is mandatory during any inspection, quite often you can see only the ends of the cable brought out for connection, and the rest of it is hidden from view. But even with full access, it is impossible to determine the quality of the insulating layer.

Electrical tests make it possible to identify all insulation defects, which allows us to draw a conclusion about the suitability of the cable for further use and provide guarantees for its use. They are divided according to the degree of complexity into:

1. measurements;

2. tests.

The first method is used to assess quality in the following cases:

after purchase, before installation in the electrical circuit begins, so as not to waste time on laying and subsequent dismantling of a faulty cable;

after completing installation work to assess their quality;

when the tests are completed. This allows you to assess the serviceability of insulation exposed to increased voltage;

periodically during operation to monitor the safety of technical characteristics under the influence of operating current loads or environmental factors.

Cable insulation tests are carried out after its installation before connection to operation or periodically during operation as necessary.

How the cable works

To explain the principle of electrical testing, let's consider the structure of a simple, commonly found cable of the VVGng brand.

Each of its current-carrying conductors is equipped with its own layer of dielectric coating, which insulates it from neighboring conductors and leakage to ground. Current-carrying wires are placed in the core and protected by a sheath.

In other words, any electrical cable consists of metal wires, most often based on copper or aluminum, and an insulation layer that protects the conductors from leakage currents and short circuits between all phases and the ground.

Each cable is designed to transmit a specific type of energy under different operating conditions. It is subject to certain, specific requirements. They must be familiarized with before carrying out electrical measurements.

Instruments for testing

Sometimes novice electricians, to measure the insulation of a cable or electrical wiring, use testers or multimeters, which have a scale for measuring resistance in kiloohms and megaohms. This is a grave mistake. Such devices are designed to evaluate the parameters of radio components and operate from low-power batteries. They are not able to create the necessary load on the insulation of cable lines.

Special devices serve these purposes - megohmmeters, called “megohmmeters” in electricians’ jargon. They have many designs and modifications.

Before you start using any device, you must check its serviceability each time:

external inspection;

assessment of the timing of inspections by the metrological laboratory based on the state of its mark on the body. Safety rules do not allow the use of a measuring device with a broken mark, even when there is a passport about the inspection carried out before its expiration;

checking the timing of periodic insulation tests of the high-voltage part of the device by an electrical laboratory. A faulty megohmmeter or damaged connecting wires can cause electric shock to personnel.

control measurement of known resistance.

Attention! All work with a megohmmeter is classified as dangerous! They can only be performed by trained, tested and approved by the commission personnel with electrical safety group III and higher.

Technical issues of preparing cables for insulation measurements and testing

Please note that the organizational part is discussed here very briefly and not completely. This is a big, important topic for another article.

1. All measurement work must be carried out on the cable with the voltage removed from it and, as a rule, the surrounding equipment. The effect of induced electric fields on the measurement circuit must be excluded.

This is dictated not only by safety, but also by the operating principle of the device, which is based on supplying a calibrated voltage to the circuit from its own generator and measuring the currents generated in it. The scale divisions of analog instruments and the readings of digital models in Ohms are proportional to the magnitude of the resulting leakage currents.

2. The cable connected to the equipment must be disconnected from all sides.

Otherwise, the insulation resistance of not only its cores, but the entire remaining connected circuit will be measured. Sometimes this technique is used to speed up work. But, in any case, to obtain reliable information, the equipment connection diagram must be taken into account.

To disconnect a cable, its ends are separated or the switching devices to which it is connected are disconnected.

In the latter case, if negative results are obtained, it is necessary to check the insulation of the circuits of these devices.

3. The cable length can reach a large value on the order of a kilometer. At the remote end, at the most unexpected moment, people may appear and, through their actions, influence the measurement result or suffer from high voltage applied to the cable from the megohmmeter. This must be prevented by running .

Features of safe use of a megohmmeter and measurement technology

Long cables laid in electrical networks near a working one may be under induced voltage, and when disconnected from the ground loop, have a residual charge, the energy of which can harm the human body. The megohmmeter generates increased voltage, which is applied to the cable cores insulated from the ground. In this case, a capacitive charge is also created: each core acts as the plate of a capacitor.

Both of these factors together impose a safety condition - to use portable grounding when measuring the resistance of each core, both individually and in combination. Without it, touching the metal parts of the cable without using protective electrical equipment is strictly prohibited.

How to measure the insulation resistance of conductors relative to ground

Consider, as an example, checking the insulation resistance of one core relative to ground.

The first end of the portable grounding is initially securely attached to the ground loop and is no longer removed until the electrical checks are completed. One of the two wires of the megohmmeter is also connected here.

The second end of the grounding, equipped with an insulated tip with a safety ring and a clip for quick connection of the “Crocodile” type, in compliance with safety rules, is connected to the metal core of the cable to remove the capacitive charge from it. Then, without removing the grounding, the output of the second wire from the megohmmeter is switched here.

Only after this is the grounding “crocodile” allowed to be removed for measurements by applying voltage to the prepared electrical circuit. The measurement time must be at least one minute. This is necessary to stabilize transient processes in the circuit and obtain accurate results.

When the megohmmeter generator is stopped, it is impossible to disconnect the device from the circuit due to the capacitive charge present on it. To remove it, it is necessary to reuse the second end of the portable grounding and apply it to the core being tested.

The conductor coming from the megohmmeter is removed from the core after connecting a portable ground to it. Thus, the circuits of the measuring device are always connected to the test circuit only when grounding is installed, which is removed at the time of measurement.

The described check of the cable insulation condition with a megohmmeter for phase C is demonstrated by a sequence of drawings.

In the given example, to simplify the understanding of the technology, the actions with other conductors that remain under induced voltage, which must be removed by installing a short circuit with additional portable grounding, are not described, which significantly complicates the circuit and measurements.

In practice, in order to speed up the work of checking phase insulation relative to ground, all cable cores are connected to a short circuit. This operation must be performed by personnel authorized to work under voltage. She's dangerous.

In the example under consideration, these are phases PE, N, A, B, C. Next, measurements are carried out using the above technology for all parallel-connected chains at once.

Usually the cables are in good condition, then such a check is sufficient. If you get an unsatisfactory result, you will have to carry out all measurements in phases.

How to measure insulation resistance between cable cores

In order to improve understanding of the process, we will simplify that the cable is not under the influence of induced voltage and has a short length, which does not create significant capacitive charges. This will allow us not to describe actions with portable grounding that must be performed using the technology already discussed.

Before taking measurements, it is necessary to inspect the assembled circuit and check it using a voltage absence indicator on the cores. They must be moved apart without touching each other or any surrounding objects. The megohmmeter is connected at one end to the phase relative to which the measurement will be performed, and the remaining phases are alternately switched with the second wire to carry out measurements.

In our example, the insulation of all cores is measured one by one relative to the PE phase. When it ends, we select the next phase, for example, N as the common one. In the same way, we take measurements relative to it, but we no longer work with the previous phase. Its insulation between all cores has been checked.

Then we select the next phase as a common one and continue measurements with the remaining cores. In this way, we go through all possible combinations of connecting the cores to each other to analyze the state of their insulation.

Once again, I would like to draw your attention to the fact that this test is described for a cable that is not subject to induced voltage and does not have a large capacitive charge. It is impossible to blindly copy it for all possible cases.

How to document measurement results

The date and scope of the inspection, information about the composition of the team, the measuring instruments used, the connection diagram, temperature conditions, work conditions, all obtained electrical characteristics must be kept in a record. They may be required in the future for a working cable and serve as evidence of a fault for a rejected product.

Therefore, a protocol is drawn up for the measurements taken, certified by the signature of the work manufacturer. To draw it up, you can use an ordinary notepad, but it is more convenient to use a pre-prepared form containing information about the sequence of operations, reminders on safety measures, basic technical standards and tables prepared for filling out.

It is convenient to create such a document once using a computer, and then simply print it on a printer. This method saves time on preparation, registration of measurement results, and gives the document an official appearance.

Features of insulation testing

This work is carried out using special stands containing extraneous high-voltage sources with measuring instruments, which are classified as dangerous. It is performed by specially trained and authorized personnel, who are organizationally part of a separate laboratory or service at enterprises.

The testing technology is much like the insulation measurement process, but uses more powerful energy sources and high-precision measuring instruments.

The test results, as with measurements, are documented in a protocol.

Operation of insulation monitoring devices

A lot of attention is paid to automatic checking of the insulation condition of electrical equipment in the energy sector. It can significantly increase the reliability of power supply to consumers. However, this is a separate large topic that requires additional disclosure in another article.

Like any equipment or technique, over time, electrical cables of various types begin to fail. One of the methods for determining the safety factor of a cable and identifying defects is to measure the insulation resistance. This article explains what it is, when and how it is done.

Electrical wiring inspection

Each organization that manages electrical installations must have a person responsible for electrical equipment. His responsibilities include drawing up scheduled maintenance work for the repair of this equipment, as well as conducting periodic tests and measurements, and inspecting electrical wiring. The frequency of such measurements, as a rule, is based on the requirements of PTEEP. For example, regarding the measurement of insulation resistance, it says that tests should be carried out once every 3 years.

What is insulation resistance measurement

This is a measurement with a special device (megaohmmeter) of the resistance between two points of an electrical installation, which characterizes the leakage current between these points when DC voltage is applied. The result of the measurement is a value expressed in MOhm (megaOhm). The measurement is carried out by a device - a megohmmeter, the principle of which is to measure the leakage current that occurs under the influence of a constant pulsating voltage on an electrical installation. Modern megohmmeters provide different voltage levels for testing different equipment.

Allowable resistance for various equipment

The main guiding document is the PTEEP, which provides the frequency of tests, the magnitude of the test voltage and the standard resistance value for each type of electrical equipment (PTEEP Appendix 3.1, Table 37). Below is an excerpt from the document.

Do not confuse the resistance of electrical cables with the resistance of a coaxial cable and the characteristic impedance of the cable, because This applies to radio engineering and there are different principles of approach to permissible values.

Electrical safety issue

Insulation resistance measurement is carried out in order to protect a person from electric shock and for fire safety purposes. Hence the minimum resistance value is 500 kOhm. It is taken from a simple calculation:

U – phase voltage of the electrical installation;

RIZ – insulation resistance of electrical equipment;

RF is the resistance of the human body; for electrical safety calculations, RF = 1000 Ohm is taken.

Substituting known values (U=220 V, RIZ=500 kOhm), a leakage current of 0.43 mA is obtained. Sensible current threshold is 0.5 mA. Thus, 0.5 MOhm is the minimum insulation resistance at which the average person will not feel any leakage current.

When measuring with a megohmmeter, you should also pay attention to safety, because the device produces up to 2500 V on its probes, it can be fatal to humans. Therefore, only specially trained personnel can carry out measurements. The connection of the megohmmeter and measurements must be carried out at an electrical installation disconnected from the electrical network. It is necessary to check the electrical wiring for lack of voltage. If testing is carried out on a cable, the area should be protected from accidental contact with bare parts of the cable at the opposite end from the test site.

Method for measuring cable insulation resistance

First, personnel must determine that there is no voltage on the cable using a voltage indicator. At the opposite end, the cable cores must be separated at a sufficient distance so that there is no accidental short circuit. Then prohibition signs are posted in the testing area. You should also conduct a visual inspection of the cable, if possible, to determine if there are hot spots or exposed areas. After this, you can start measuring. It is necessary to measure the insulation resistance between phases (A-B, A-C, B-C), between phases and zero (A-N. B-N, C-N), between zero and the ground wire. The time of each measurement is 1 minute. After each test, it is necessary to ground the cable core, although modern megohmmeters can carry out independent discharge. The results obtained are recorded in the protocol. It is worth remembering that if the data obtained is made for some inspection commission, only a specialized electrical laboratory has the right to make the protocol.

Instruments for measurements

For testing with constant pulsating voltage, the best choice is a megohmmeter. In devices of older designs, a built-in mechanical generator operating on the principle of a dynamo was used to obtain voltages. To produce the required voltage, it was necessary to twist the knob hard. Currently, megohmmeters are made in the form of electronic devices powered by batteries; they have a compact size and convenient software.
temporary megohmmeters have a memory where several tests are stored. With each measurement, the absorption coefficient is automatically calculated. Its value is determined by the ratio of the polarization current to the leakage current through the dielectric - the winding insulation. With wet insulation, the absorption coefficient is close to 1. With dry insulation, R60 (insulation resistance 60 seconds after the start of the test) is 30-50% greater than R15 (after 15 seconds).

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How to check insulation

When wiring is done, they talk about the cross-section of the conductor. When creating an electrical contact, they think about the contact area of the conductors and whether it will be sufficient for reliable contact. But the area of contact between the insulation and the conductor in wires, cables or insulating substrates is never considered. How then to talk about this, and in general, how to measure insulation resistance?

Illustration 1

To measure the resistance of various materials, you can take a sample of a material of a certain shape and size and, by applying some voltage to the two ends, obtain some current. Measure it and get the resistance using Ohm's law

Formula

The resistivity will be equal to

Formula 2

It, unlike R, does not depend on either the length (thickness) of the material or the contact area.

According to this principle, resistivities are measured for various materials and can be found in reference tables. And for insulators too.

That is, for work, you could simply choose a better insulator and use it. Yes, this does not need to happen, because usually the word “isolator” speaks for itself. Electrical materials are produced by industry taking into account all standards. The task of the insulator is not to pass current, providing resistance (as we see from the table - the resistance is huge), but simply to isolate some conductors from others.

But reference values for insulator resistance may change over time. All materials age, collapse, decompose under the influence of temperature changes, light, vibrations, their structure is disrupted. Microcracks, peeling, and peeling appear. They become thinner, water penetrates into the pores, and can decompose chemically. Dust occurs, and not all dust is an insulator. That is, the insulating properties of dielectrics deteriorate over time.

Therefore, I would like to be sure that this particular insulator on a given wire or electrical bus will play its role well.

Then they check the insulation resistance of the cable (or wires and cables, cords, and so on). And at the same time they check for electrical strength at a certain measuring voltage. All this is done in electrical power circuits, where such characteristics are vital.

Cable insulation resistance standard

There are Rules for the Operation of Consumer Electrical Installations (PEEP, ed. 5, 1997, MinTopEnergo of the Russian Federation, Moscow), which set out standards regarding the safe operation of electrical installations, as well as power lines and premises where electrical equipment operates. Table 43 of Appendix 1 describes what voltages should be used to test insulation on various electrical installations up to 1000 volts. Specifically, in which places to measure and what standard resistance the insulation should have.

I present part of the table here (without extensive instructions on where exactly the insulation resistance is measured for many of the types of installations given in it).

As you can see, the insulation resistance should generally be no higher than 0.5 MOhm*m.

And measurements (tests) are carried out with voltages of up to 1000 volts, and this is a life-threatening voltage. The methodology is such that the test is carried out in installations at their locations. To prevent the test from damaging the circuit elements, they are first shunted.

Cables are tested by applying voltage to one of their wires and measuring the insulation resistance between it and the other wires of the cable.

Instruments for measuring insulation resistance

Any device for measuring electrical resistance uses a reference voltage source in its design. Some multimeters allow you to connect an external high voltage source to measure high resistances. There are only instruments specifically designed to measure cable insulation resistance. They are called megohmmeters. They carry out: measuring the insulation resistance of electrical wiring, checking the insulation resistance for breakdown by high voltage, measuring the insulation resistance in various devices, measuring the insulation resistance of power electrical equipment, and so on.

Megger Measuring device Cables

To operate, the megger must meet the following characteristics:

be in good working order - from the point of view of external inspection;
officially verified in a metrological laboratory, the period for the next verification must not be completed;
it must have an unbroken metrologists’ seal;
the high-voltage part must be tested in an electrical laboratory for proper insulation; the kit must contain high-voltage wires with a measured insulation resistance that is sufficient for work with high voltage;
A control measurement of the insulation of a sample with a known resistance must be carried out on it.

Please keep in mind that:

Any work with a megger is classified as dangerous. The danger concerns both the people directly carrying out the measurement and anyone who may be in the testing area. Equipment that may be damaged by the test voltage is also at risk.

The danger comes from the high voltage under which installation conductors, cables, and grounding bars are placed during testing.

Preparing for an Insulation Resistance Test

Much of the preparation for taking measurements concerns work safety. All actions must be carried out carefully to avoid accidents. Particular attention should be paid to alerting people who are not involved in the measurements, but who for some reason may find themselves near the work sites.

Insulation resistance measurements with a megger should be carried out on conductors disconnected from the supply voltage. Surrounding equipment must also be de-energized to avoid electrical fields influencing the measurement results.

Although the test voltage when measuring the insulation resistance of electrical wiring is high, the measurement itself is subtle and subject to very little interference. This is explained by the fact that currents of microampere values penetrate through the insulation, even at high voltage, due to the extremely high specific resistances of the insulators. Measuring these currents ultimately gives a resistance value of the order of several megohms.

The cable being tested, which is part of the working wiring of the equipment, must be completely disconnected from the rest of the wiring before measurements are taken.

Preparation diagram for measuring insulation resistance

Preparation diagram for measuring insulation resistance:

It is necessary to take into account the configuration and length of the cable being tested, since all of it will be under high test voltage. It is necessary to exclude the impact of this voltage on people along the entire length of its presence. This is achieved by posting warning signs and monitoring the testing area.
Long cables, which are typically exposed to high voltages, may carry significant residual charges or interference charges from surrounding high-voltage equipment when disconnected. This is dangerous for people and can damage equipment if discharged. This may affect the measurement results. For all these reasons, the cable under test, as well as all electrically conductive parts of the circuits, must be discharged through grounding.

How to use a megohmmeter

Use protective equipment and install portable grounding before starting work at a specific measurement location.

Protective attributes Protected tool Device

Method for measuring insulation resistance

There are several tests on cable lines; they cover all possible options for line breakdowns in different directions. Similar measurements of cable insulation with a megger are periodically carried out at places where electrical equipment is installed.

The insulation resistance of the wires relative to the ground is measured.

The sequence is:

First, portable grounding is installed.
One end is connected to the ground wire.
At the other end, all wires of the cable line are connected in turn to discharge them from residual charges. All cable cores are shorted together.
Without removing the grounding from them, the grounding wire is connected to the device.
The cores of the cable lines are disconnected from grounding.
The second wire of the megger is connected to the cores.
The test voltage is turned on - about 1000 V. It must be applied to the cable for about a minute so that all transient processes in the line wires are completed.
A measurement is made on the device, and the results are entered into the test table.

Measuring the insulation resistance of wires in a cable line relative to each other

The difference from the previous test is that the measurement is made sequentially in the cable conductors relative to the grounding conductor.

Preparation for core insulation measurement Continuation of measurement

In the same way, you can measure the resistance of the core insulators relative to the neutral wire and relative to each other.

Between different tests, the test voltage is turned off, and the cable line conductors participating in the test are discharged through grounding.

Measurements of the insulating properties of power equipment dielectrics relative to ground.

Equipment insulation measurements are carried out relative to grounding. Work of this kind should be carried out only after a thorough study of the equipment diagrams. First, all equipment is disconnected from external networks, then discharged through grounding, after which its insulation is tested at the terminals of the main buses supplying the equipment.

Equipment insulation measurement

Checking floors and walls for insulation resistance with a megger.

Wiring diagram for walls and floors

Floors and walls are checked several times at different distances from the equipment. First in the immediate vicinity, then after a few meters. One wire of the megger is connected to ground, the other to an electrode made of a piece of flat metal measuring at least 250x250 mm. The electrode, under which wet paper or cloth is placed, is pressed against the wall (floor) for the duration of the measurement. For pressing, a minimum force is used: 750 N - to the floor, 250 N - to the wall.

All work is carried out wearing rubber protective gloves and protective boots.

After all activities are completed, the results are documented in a protocol.

domelectrik.ru

Hello, readers of the Electrician's Notes blog.

In the previous article about testing cable lines, I told you that one of the points of testing cable lines is measuring the cable insulation resistance.

This is what we will talk to you about in detail. Let's consider how to correctly measure the insulation resistance of both power and control cables. We will also get acquainted with the methodology for carrying out these measurements.

Preparing to measure cable insulation resistance

Before starting work on measuring cable insulation resistance, it is necessary to accurately know the ambient temperature.

What is this connected with?

This is due to the fact that at negative temperatures, if there are water particles in the cable mass, these particles will be in a frozen state, i.e. in the form of pieces of ice. You all know that ice is a dielectric, i.e. has no conductivity.

Therefore, when measuring insulation resistance at subzero temperatures, these particles of frozen water will not be detected.

Instruments and measuring instruments

The second thing we need to measure the insulation resistance of cable lines is the availability of instruments and measuring instruments.

To measure the insulation resistance of cables for various purposes, I and the workers of our electrical laboratory use the MIC-2500 device. There are other devices, but we use them somewhat less frequently.

This device is manufactured by Sonel and can be used to measure the insulation resistance of cable lines, wires, cords, electrical equipment (motors, transformers, switches, etc.), as well as measure the degree of aging and moisture content of the insulation.

I would like to note that the MIC-2500 device is included in the state register of devices that are approved for measuring insulation resistance.

The MIC-2500 device must be subject to state verification annually. After passing verification, a hologram and a stamp indicating verification completion are placed on the device. The stamp indicates the serial number of the device and the date of the next verification.

Accordingly, it is necessary to measure insulation resistance only with a serviceable and verified device.

Insulation resistance standards for various cables

Before moving on to the standards for cable insulation resistance, it is necessary to classify them somehow.

I offer you my simplified classification of cables.

Cables according to their intended purpose are divided into:

high-voltage power above 1000 (V)
low-voltage power below 1000 (V)
control and control cables, we will simply call them control cables (this includes secondary switchgear circuits, power supply circuits for electric drives of switches, separators, short circuiters, control circuits, protection and automation circuits, etc.)

Insulation resistance measurement for both high-voltage cables and low-voltage power cables is carried out with a megohmmeter for a voltage of 2500 (V). And control cables are measured with a megohmmeter for a voltage of 500-2500 (V).

Accordingly, each cable has its own insulation resistance standards. According to PTEEP (clause 6.2. and table 37) and PUE (clause 1.8.37 and table 1.8.34):

High-voltage power cables above 1000 (V) - not standardized, but the insulation resistance must be at least 10 (MOhm)
Low voltage power cables below 1000 (V) - insulation resistance should not be less than 0.5 (MΩ)
Control cables - insulation resistance should not be less than 1 (MΩ)

Methodology for measuring insulation resistance of high-voltage power cables

For a clearer picture of the work on measuring the insulation resistance of high-voltage power cables, I will give you a visual diagram and procedure.

1. Check the absence of voltage on the cable with a high voltage indicator

2. We install a test grounding with special alligator clips on the cable cores from the side where we will measure the insulation resistance.

3. On the other side of the cable, leave the cores free and separate them at a sufficient distance from each other.

4. We hang prohibition and warning posters. On the other hand, I recommend leaving a person who will observe that when measuring the insulation resistance with a megohmmeter, no one comes under the test voltage.

5. We measure the insulation resistance of a high-voltage power cable with a 2500 (V) megohmmeter, alternately on each core for 1 minute.

For example, we measure the insulation resistance on the conductor of phase “C”. At the same time, we install test grounding on the conductors of phases “B” and “A”. We connect one end of the megohmmeter to a grounding device, or, more simply, to “ground.” The second end goes to the core of phase “C”.

In an example it looks like this:

6. We write down the readings obtained during the measurement of the insulation resistance of the high-voltage cable in a notebook.

Methodology for measuring insulation resistance of low-voltage power cables

The method for measuring the insulation resistance of low-voltage power cables differs from the previous one (described above), but only slightly.

Likewise:

2. On the other side of the cable, leave the cores free and separate them at a sufficient distance from each other.

3. We hang prohibition and warning posters. On the other hand, I recommend leaving a person who will observe that when measuring the insulation resistance with a megohmmeter, no one comes under the test voltage.

4. We measure the insulation resistance of a low-voltage power cable with a 2500 (V) megohmmeter for 1 minute:

between phase conductors (A-B, B-C, A-C)
between phase conductors and zero (A-N, B-N, C-N)
between phase conductors and ground (A-PE, B-PE, C-PE), if the cable is five-core
between zero and ground (N-PE), having previously disconnected zero from the zero bus

5. We write down the readings obtained during the measurement of the insulation resistance of the low-voltage cable in a notebook.

Methodology for measuring insulation resistance of control cables

Well, now we have reached the point of measuring the insulation resistance of control cables.

The peculiarity of their measurement is that the cable cores can not be disconnected from the circuit and measurements can be taken together with the installed electrical equipment.

Measuring the insulation resistance of the control cable is performed in the same way.

1. We check that there is no voltage on the cable using protective equipment designed for work in electrical installations.

2. We measure the insulation resistance of the control cable with a 500-2500 (V) megohmmeter as follows.

We connect one terminal of the megohmmeter to the core being tested. We connect the remaining conductors of the control cable to each other and to the ground. We connect the second terminal of the megohmmeter either to ground or to any other non-tested conductor.

For clarity, see the photo:

Within 1 minute we measure the core being tested. Next, we return the measured core to the rest of the cable cores and proceed to measuring the next core.

So every vein.

3. We write down all the obtained readings of the insulation resistance of the control cable in a notebook.

Cable insulation resistance measurement protocol

In all of the above electrical measurements, after receiving readings of the cable insulation resistance, it is necessary to compare them with the requirements and standards of PUE and PTEEP. Based on the comparison, it is necessary to draw a conclusion about the suitability of the cable for further operation and draw up a protocol for measuring the insulation resistance.

P.S. This concludes the article. If you have any questions, feel free to ask them. And also don’t forget to subscribe to new articles from my website.

zametkielectrika.ru

Measuring cable insulation resistance is one of the most important points in cable testing. For example, if the sheath, which has properties that protect the cable, is damaged, then unpleasant consequences are possible, among them various violations in the energy saving system are common. This is the main reason why it is necessary to measure the insulation resistance of cables.

To avoid electric shock, fires and other unpleasant situations, etc., it is necessary to constantly measure the insulation resistance of VVG cables in order to identify faulty areas in the electrical wiring.

In order to measure resistance, you need to start by inspecting the electrical wiring and wires. Particular attention should be paid to those cables that have connections to protection devices. There should be no melted ends so that the cable does not heat up during operation, as this can significantly complicate the work. For example, the cable may heat up due to improper connection of the cores to the terminals; it may also be due to the fact that the circuit breaker is in a faulty state.

In order to take a measurement, you need:

First, turn off all electrical appliances and all cables and wires that are subject to electrical measurements.
Before taking measurements, you need to remove all light bulbs from the lighting fixtures. At the same time, all lighting switches must be turned on.
It is necessary to turn off the power supply to cables and wires.

After following all the above instructions, the power system will be completely ready to measure insulation resistance.

The permissible cable insulation resistance reading must be above 0.5 mOhm. If these indicators do not meet, then this cable must be dismantled.

It is also necessary to take into account that the determination of resistance is carried out only after its phasing, as well as an integrity check. You need to measure the cable resistance using a megohmmeter. (Figure 1)

If you are taking a measurement with a large value, it is best to take it when the needle that is oscillating has completely calmed down. It is also necessary that all electrical appliances be unplugged from the network.

It is prohibited to determine the resistance of lines that are close to other similar lines.

Fig 1. Megaohmmeter

The resistance is determined using a megohmmeter with a voltage of 2500 (V) for 1 minute.

Measurements:

(A – B; B – C; C – A), that is, between phase conductors;
(A – N; B – N; C – N), also between neutral and phase conductors;
(A – PE; B – PE; C – PE), also between the ground and phase conductors;
(N – PE), and finally between ground and neutral conductors.

There are some rules to consider when measuring cable insulation resistance:

Firstly, in order to take a measurement, you need to know the exact ambient temperature. Because if there is a negative temperature, and there is water in the cable mass (even in small quantities), then it will turn into pieces of ice. And ice itself is a dielectric, that is, it does not have conductivity abilities. Moreover, when carrying out insulation, you will not be able to identify these pieces of ice, so you need to immediately take care of an acceptable temperature. The optimal temperature should not be lower than +5°C (exceptions are cases specified in special instructions.).
Secondly, if the resistance of the electrical wiring, which is in working condition, is less than 1 MOhm, then a conclusion about their suitability is given after a special check of this electrical wiring is first carried out, which consists of applying an alternating current of industrial frequency to it, but with a voltage of 1 kV, and then conclusions are drawn about their suitability.
Thirdly, we must not forget that only flexible wires should be used when measuring (they have special insulating handles at the ends, and they also have restrictive rings in front of the contact probes). The wires that connect have a minimum length.
Fourthly, a megohmmeter of 1000 V and above is used for determination. Devices that have not passed annual government inspections are not allowed for use.

If the voltage in electrical installations is above 1000 (V), measuring the cable resistance should be carried out wearing dielectric gloves.

In order to determine the standards for cable insulation resistance, you must first classify these cables:

Cable classification:

above 1000 (V), that is, high-voltage power;
below 1000 (V), that is, high-voltage power;
as well as control cables.

Accordingly, the insulation resistance standards are different for each type of cable, for example:

For cables above 1000 (V), high voltage, there is no specific standard, but the resistance will be higher than 10 (MOhm).
For cables below 1000 (V), low voltage - the resistance must be above 0.5 (MOhm).

Whether high or low voltage is used, it all depends on the voltage of your electrical installation.

myfta.ru

Power cable lines

Power cable lines with voltage up to 1 kV are tested according to paragraphs 1, 2, 7, 13, for voltages above 1 kV and up to 35 kV - according to paragraphs 1-3, 6, 7, 11, 13, for voltages of 110 kV and above - in to the full extent provided for in this paragraph.

1. Checking the integrity and phasing of the cable cores. The integrity and coincidence of the phase designations of the connected cable cores are checked.

2. Insulation resistance measurement. Produced with a megohmmeter for a voltage of 2.5 kV. For power cables up to 1 kV, the insulation resistance must be at least 0.5 MOhm. For power cables above 1 kV, the insulation resistance is not standardized. The measurement should be made before and after testing the cable with increased voltage.

3. Test with increased voltage of rectified current.

The test voltage is taken in accordance with Table 1.8.39.

Table 1.8.39 Rectified current test voltage for power cables

________________

* Rectified voltage tests of single-core cables with plastic insulation without armor (screens) laid in air are not carried out.

For cables for voltages up to 35 kV with paper and plastic insulation, the duration of application of the full test voltage is 10 minutes.

For rubber-insulated cables with a voltage of 3-10 kV, the duration of application of the full test voltage is 5 minutes. Cables with rubber insulation for voltages up to 1 kV are not subjected to high voltage tests.

For cables with a voltage of 110-500 kV, the duration of application of the full test voltage is 15 minutes.

Permissible leakage currents depending on the test voltage and permissible values of the asymmetry coefficient when measuring leakage current are given in Table 1.8.40. The absolute value of the leakage current is not a rejection indicator. Cable lines with satisfactory insulation must have stable leakage current values. During the test, the leakage current should decrease. If there is no decrease in the value of the leakage current, as well as if it increases or the current is unstable, the test should be carried out until the defect is identified, but not more than 15 minutes.

Table 1.8.40 Leakage currents and asymmetry coefficients for power cables

Cables voltage, kV	Test voltage, kV	Permissible values of leakage currents, mA	Acceptable values of the asymmetry coefficient ()
6	36	0.2	8
10	60	0.5	8
20	100	1.5	10
35	175	2.5	10
110	285	Not standardized	Not standardized
150	347	Same	Same
220	610	"	"
330	670	"	"
500	865	"	"

When laying mixed cables, take the lowest test voltage according to Table 1.8.39 as the test voltage for the entire cable line.

4. Test with AC voltage frequency 50 Hz.

Such a test is allowed for cable lines for a voltage of 110-500 kV instead of a rectified voltage test.

The test is carried out with voltage (1.00-1.73). It is allowed to carry out tests by switching on the cable line to the rated voltage. The duration of the test is according to the manufacturer's instructions.

5. Determination of the active resistance of the cores. Produced for lines 20 kV and above. The active resistance of the cable line conductors to direct current, reduced to 1 mm cross-section, 1 m length and temperature +20 ° C, should be no more than 0.0179 Ohm for a copper conductor and no more than 0.0294 Ohm for an aluminum conductor. The measured resistance (reduced to specific value) may differ from the specified values by no more than 5%.

6. Determination of the electrical working capacitance of the cores.

Produced for lines 20 kV and above. The measured capacitance should not differ from the factory test results by more than 5%.

7. Checking protection against stray currents.

The operation of the installed cathodic protection is checked.

8. Test for the presence of undissolved air (impregnation test).

Produced for oil-filled cable lines 110-500 kV. The content of undissolved air in the oil should be no more than 0.1%.

9. Testing of feeding units and automatic heating of end couplings.

Produced for oil-filled cable lines 110-500 kV.

10. Checking anti-corrosion protection.

When accepting lines into operation and during operation, the operation of anti-corrosion protection is checked for:

— cables with a metal sheath laid in soils with medium and low corrosive activity (soil resistivity above 20 Ohm/m), with an average daily leakage current density into the ground above 0.15 mA/dm;

— cables with a metal sheath laid in soils with high corrosive activity (soil resistivity less than 20 Ohm/m) at any average daily current density into the ground;

— cables with an unprotected sheath and destroyed armor and protective coverings;

— steel pipeline of high-pressure cables, regardless of the aggressiveness of the soil and types of insulating coatings.

During the test, potentials and currents in the cable sheaths and electrical protection parameters (current and voltage of the cathode station, drainage current) are measured in accordance with the guidelines for the electrochemical protection of underground energy structures from corrosion.

The assessment of the corrosive activity of soils and natural waters should be carried out in accordance with the requirements of GOST 9.602-89.

11. Determination of characteristics of oil and insulating liquid.

The determination is made for all elements of oil-filled cable lines for a voltage of 110-500 kV and for end joints (inputs into transformers and switchgear) of plastic-insulated cables for a voltage of 110 kV.

Samples of oils of grades S-220, MN-3 and MN-4 and insulating liquid of grade PMS must meet the requirements of the standards of tables 1.8.41 and 1.8.42.

Table 1.8.41 Standards for quality indicators of oils of grades S-220, MN-3 and MN-4 and insulating liquid of grade PMS

Note. Test oils not listed in Table 1.8.39 in accordance with the manufacturer's requirements.

Table 1.8.42 Tangent of the dielectric loss angle of oil and insulating liquid (at 100,%, no more, for voltage cables, kV)

110	150-220	330-500
0,5/0,8*	0,5/0,8*	0,5/-

________________

* The numerator indicates the value for S-220 grade oils, the denominator for MN-3, MN-4 and PMS

If the values of electrical strength and degree of degassing of MN-4 oil comply with the standards, and the values of tg δ, measured according to the GOST 6581-75 method, exceed those indicated in Table 1.8.42, the oil sample is additionally kept at a temperature of 100 ° C for 2 hours, periodically measuring. When the tg δ value decreases, the oil sample is kept at a temperature of 100 °C until a steady value is obtained, which is taken as the control value.

12. Ground resistance measurement.

Produced on lines of all voltages for terminations, and on lines 110-500 kV, in addition, for metal structures of cable wells and make-up points.

1. Scope of application.

1. This document has been developed for electrical laboratory applications during acceptance testing of consumer electrical installations.

2. This document defines the methodology for measuring insulation resistance and determining the insulation state of power, lighting wiring and cable lines with voltages up to 1 kV and testing the insulation of secondary circuits and devices with increased voltage of industrial frequency.

3. Tests are carried out to determine the presence of the required safety margin of the insulation of electrical conductors, the absence of general and local defects after installation work.

4. The purpose of the inspection is to check the compliance of the condition of porcelain insulators with the requirements of the PUE.

2. Test object.

Secondary electrical wiring circuits and power cable lines up to 1000 V are subject to testing.

3. Determined characteristics.

When checking power cable lines up to 1000 V, tests are carried out in the following scope:

4. Test conditions.

Tests of power cable lines up to 1000 V are carried out at an ambient temperature of not lower than +5 ° C and a relative humidity of not more than 90%.

5. Measuring tools.

Technical data of measuring instruments used in testing power cable lines up to 1000 V:

6. Procedure for carrying out measurements.

4. Checking the functionality of measuring instruments in accordance with the operating instructions.

7. Insulation resistance measurement.

Before use, it is recommended to subject the megohmmeter to a control test, which consists of measuring the readings on the scale with open and short-circuited wires of the megohmmeter itself. In the case of open wires, the megohmmeter needle should be at the “infinite” scale mark, and in the case of short-circuited wires, at the “0” scale mark. Familiarize yourself with the electrical diagram of the facility. Measure insulation resistance with an open external circuit. Turn on the switches that directly power the lighting groups. The light bulbs must be turned out. Protective grounding from the object is allowed to be removed only after the device is connected to it.

When measuring insulation resistance, the following operations must be performed:

— measure the insulation resistance of wiring and cables in the direction from the supply feeders and further as the circuit branches. Measurements should be taken between the conductors and between each conductor and the “ground” in turn.

— to develop the specified voltage on the megohmmeter generator, rotate the handle at a speed of 120 rpm. The generator is equipped with a centrifugal regulator that limits the rotation speed, so that the output voltage remains constant.

— measurements should be made with a stable position of the instrument needle. Readings should be taken 1 minute after the start of measurements.

— after completion of measurements, the test object must be discharged by short-term grounding.

— measure the insulation resistance of the cables in each ShR distribution cabinet, going from the fuse group to the ShchO lighting panels.

— the readings of all measurements are recorded in the work log and analyzed. Insulation is considered unsuitable for use if its resistance is below the minimum permissible value. In this case, the insulation temperature must not be lower than +5°C.

- when determining high insulation resistances, in damp weather (at high humidity), so that the megohmmeter readings are not influenced by leakage currents along the insulation surface, connect the megohmmeter to the test object using the “screen” clamp (E). Connect the “screen” terminal to a current-carrying electrode located on the insulated cable winding near the funnel, or to the grounded cable sheath.

— before carrying out measurements, it is necessary to reduce, if possible, the number of factors causing additional error.

8. High voltage insulation tests

industrial frequency.

Preparation for testing:

— before testing, all ground connections are removed and all equipment, the use of which does not allow high voltage testing, is disconnected.

— Temporary jumpers, which must be installed according to the condition of combining sections of the electrical circuit, must differ from the wires that make up the wiring diagrams.

— before applying voltage to the test installation, it is necessary to:

a) check whether all team members are in place and whether there are any unauthorized persons;

b) warn the crew with the words “Applying voltage”, after which remove the ground from the input of the testing installation and turn on the installation.

— at the end of the tests, the manufacturer removes the voltage from the test installation to zero, turns off the device, grounds the terminal of the test installation and informs the team workers with the words: “The voltage has been removed.” Only then can the wires be reconnected from the test setup or disconnected at the end of the test.

Performing tests:

— insulation testing with high frequency voltage is carried out according to the diagram in Fig. 1

— with a large number of branched circuits, to prevent overloading of the test installation with capacitive currents, tests should be carried out in sections.

— insulation is considered to have passed the high voltage test if there was no breakdown, partial discharges, gas or smoke release, a sharp decrease in voltage and increase in current, or local heating of the insulation.

Fig.1. Scheme for testing the insulation of secondary circuits with increased voltage.

10. Data processing and registration of measurement results.

1. Based on the data received, a protocol of the established form is drawn up.

The lowest of the obtained insulation resistance values of the measured circuit is entered into the protocol. The protocol is drawn up in the form of a table.

11. Safety and environmental requirements.

1. When performing tests, it is necessary to be guided by the requirements of the “Inter-industry rules for labor protection during the operation of electrical installations”.

2. Tests of busbars and connecting busbars do not pose any danger to the environment.