Test periods for rubber dielectric mats. Testing of dielectric mats

Dielectric mat.

A dielectric mat or, according to the rules, dielectric rubber carpets and insulating stands are used as additional electrical protective equipment in electrical installations up to and above 1000 V.

Carpets are used in closed electrical installations of all voltages, except for particularly damp rooms, and in open electrical installations in dry weather. The stands are used in damp and dirty areas.

Depending on the purpose and operating conditions, carpets are manufactured in accordance with GOST 4997-75 of standard design and are oil and petrol resistant. Carpets must have a corrugated front surface and be one color.

Carpets are made in the following sizes:

length from 500 - 1000 mm and over 1000 - 8000 mm;

width from 500 - 1200 mm;

thickness 6± 1 mm.

The insulating support consists of a flooring mounted on supporting insulators with a height of at least 70 mm. Insulators of the CH-6 type are produced especially for the manufacture of stands.

Flooring measuring at least 500x500 mm should be made from wooden planks without knots or cross-layers, planed from well-dried wood. The gaps between the slats should not exceed 30 mm. Solid floorings are not recommended, as they make it difficult to verify the absence of accidental bridging of insulators. The flooring must be painted on all sides.

Insulating supports must be strong and stable. If removable insulators are used, their connection to the flooring must prevent the possibility of the flooring slipping. To eliminate the possibility of the insulating stand overturning, the edges of the deck should not protrude beyond the supporting surface of the insulators.

Testing of dielectric carpets and insulating supports.

Carpets and coasters are not tested for use. They are rejected during inspections. Carpets should be cleaned of dirt and inspected at least once every 6 months. If defects are found in the form of punctures, tears and cracks, they should be replaced with new ones.

The supports are inspected once every 3 years for any damage to the integrity of the supporting insulators, kinks, or weakening of the connection between individual parts of the flooring. If these defects are detected, they are rejected, and after the defects are eliminated, they are tested according to the acceptance testing standards.

Rules for using dielectric carpets and stands.

After storage at sub-zero temperatures, carpets must be kept in packaged form at a temperature of 20 ± 5° C for at least 24 hours before use.

Before use, carpets and insulating supports must be cleaned of dirt, dried and inspected for defects - punctures, tears, cracks of carpets and for the absence of violations of the integrity of the supporting insulators, kinks, weakening of the connection between individual parts of the flooring.

Dielectric carpets GOST 4997-75

Rubber dielectric mats are used for protection when working with electrical installation equipment in enterprises, factories and substations, protect against possible impact electric current and harmful effects of electric fields.
The product is manufactured in accordance with GOST 4997-75 from rubber fabric, which has dielectric properties. Also by technical specifications Carpets should have a corrugated front surface, the depth of the reefs should be 1-3 mm, the texture should provide anti-slip when working on the carpet.
Rubber dielectric mats should not have cracks, protrusions, or foreign inclusions.

There are two types of dielectric carpets:
Group 1 - for work at temperatures from -15 to 40 C
Group 2 - oil and petrol resistant carpets for operation at temperatures from -50 to + 80; under such conditions, the operating time of the carpet should not exceed 3000 hours.

Carpet sizes:
500×500×6 mm
600×600×6 mm
700*700 *6 mm
750×750×6 mm
900×900×6 mm
1000×1000×6 mm
1000×8000×6 mm

Technical requirements:
test voltage - 20 kV AC with a frequency of 50 Hz
acceptable maximum current leakage - no more than 160 mA/m2
electrical strength - not less than 10 kV/mm

Quality control:
Dielectric mats are tested in accordance with the requirements of GOST 4997-75.
Each batch of carpets must be subjected to acceptance tests according to the characteristics stated in GOST.
Each batch of dielectric carpets has a quality document. The certificate contains basic data about the batch:
- information about the manufacturer
- batch number
- number of carpets and sizes
- date of manufacture
- report on test results.

Test table example:

QUALITATIVE INDICATORS

Periodic testing must be carried out at least once a month.

Labeling and packaging:
Each carpet is marked with indelible paint.
Dielectric mats are supplied on pallets, tied with packing tape.
Transportation and storage
Dielectric mats in accordance with the requirements of GOST 4997-75 must be transported and stored at a temperature environment within the range from 0C to +30C without deformation or damage.
Rugs should be protected from direct exposure sun rays and store at a distance of at least 1 meter from heating devices. Exposure to oils, gasoline and other rubber-destroying substances is not allowed.
In case of transportation or storage at negative temperatures, before use it is necessary to keep the carpets in the packaging at a temperature of +20C±5C for 24 hours.

Warranty period:
The manufacturer guarantees compliance dielectric mats requirements of GOST 4997-75. Subject to the conditions of transportation, storage and operation, the manufacturer guarantees a shelf life of products for 3 years from the date of manufacture. The warranty period for dielectric mats is 3 years from the date of their commissioning.

The price of a dielectric mat depends on the size and quantity of the batch.

Product Description:

Dielectric carpets

Dielectric rubber carpets and insulating stands are used as additional electrical protective equipment in electrical installations up to and above 1000 V.

Carpets are checked for test voltage and leakage current alternating current with a frequency of (50÷0.2) Hz at (25±10) 0C and relative humidity (45-75)%

Carpet testing is carried out using one of three methods.

Carpets are pulled between metal rollers with a diameter of 200±25 mm, which serve as electrodes. The lower roller is grounded and driven forcibly at a speed of (3±0.3) cm/s. The upper roller is connected to a high voltage source and rotates freely. The length of the electrodes should ensure that the entire width of the carpet is tested, with the exception of 50 mm on each side of the carpet. A test voltage of 20 kV is applied to the electrodes and removed from them at a distance of 50 mm from the line of contact of the electrodes to the edges of the carpet.

The test is carried out on carpets with dimensions of 750x750 mm. Water is poured into a metal bath, which serves as a grounded electrode. The carpet sample to be tested is then placed in the bath so that its edges protrude approximately 50mm above the edges of the bath. Water is poured onto the front surface of the test sample and the second electrode is lowered. In this case, the edges of the test sample, approximately 50 mm wide, must remain dry. The beginning of the test is taken to be the moment the voltage reaches 20 kV. The sample is maintained at this voltage for 1 minute. The leakage current should be no more than 67 mA.

The carpet is placed between two flat electrodes. The corners and side surfaces of the electrodes must be rounded. The radius of curvature of the side surface of the electrodes should be equal to half the thickness of the electrode. The size of the electrodes should be such that their edges do not reach the edges of the carpet on each side by 50 mm. It is allowed to use electrodes whose area is smaller than the area of ​​the carpet. In this case, the tests are carried out sequentially over the entire surface of the carpet in such a way that adjacent test areas of the carpet surface are not subjected to the test voltage more than once.

The alternating voltage of industrial frequency 50 Hz is gradually increased to 20 kV, after which it is maintained for 1 minute. Monitor the leakage current, which should be no more than 160 mA/m2.

GOST states that the first method is more preferable, but it is difficult to implement. The second method is applicable only for carpets with a size of 750x750 mm, but the third method is the easiest to use.

Standards and frequency of electrical testing of dielectric mats.

Dielectric mats are used as an additional measure of protection when working with electrical installations under high voltage. The material from which the product is made must meet the established requirements. Depending on the purpose, the size of the litter is selected, and the storage time is also taken into account when purchasing, which is limited to three years.

Purpose of products

Dielectric mats are an additional means of protection. High potential can penetrate personal equipment: gloves, boots, current measuring instruments used. In areas with ungrounded metal stands or with high floor humidity, such measures are simply necessary.

At voltages up to and above 1000 V, it is mandatory to use dielectric mats. When working with any increased voltage, a corrugated surface made of a special material is placed under the personnel’s feet. It is resistant not only to potential, but also to oils and mechanical wear.

Requirements for protective products

Dielectric mats meet the requirements regulatory documents: GOST 4997-75. The material of the product is able to withstand numerous bending cycles. The shelf life in the warehouse is 3 years, after which the manufacturer recommends changing the protective equipment. This is due to the properties of rubber to change its composition under the influence of air: it hardens, becomes brittle, and loses its ability to insulate surfaces.

The surface of the mat is corrugated and anti-slip, the depth of the grooves is about 1-3 mm. The material can withstand voltages up to 20 kV with a frequency of 50 Hz. The leakage current is measured, which does not exceed 16 Ohm A/sq. m. Structure appearance should be uniform, dark tones predominate in it.

Types of protective equipment

Products are divided into the following types:

• An ordinary dielectric mat, the price is low, the service life is limited.
• Oil and petrol resistant used in aggressive environments. Often placed on stands.

Depending on the conditions of use, the dielectric mat has a fixed size. The price depends on the dimensions. Products are divided according to standard values:

• Length 500-1000 mm. Can be more than 1000 mm and up to 8 m. Cost - from 100 to 500 rubles.
• Width - 500-1200 mm.
• Thickness - 6±1 mm.

Specialized dielectric mats are sold at prices above 500 rubles. Stands, depending on the design, can cost several thousand rubles. Unique products made to order (according to the customer’s drawing) have negotiable payment and production time.

In humid environments, it is recommended to use an insulated stand. It is a high-rigidity dielectric surface placed on legs made of a similar material. The height of the products starts from 70 mm. The flooring is laid out from wooden blocks with a gap of more than 30 mm. For the legs, special insulators of the CH-6 type are used. Additional protection can be provided by a rubber mat placed on the surface of the stand.

Checking protective equipment

The dielectric and insulating support are subject to periodic diagnostics for breakdown and integrity of materials. Before use, an external inspection of the mats is carried out; checking for cracks in the material is carried out during bending of the plastic structure. It is recommended to inspect the stands for the presence of chips on the legs and bedding.

If defects are found, mats, flooring and other protective equipment must be replaced. If the stands do not move, then diagnostics are carried out at least once every 3 years. If the defect can be eliminated, then the dielectric must be checked for breakdown in accordance with the standards.

To prevent premature wear of rubber coatings, it is recommended to observe following rules product use:

• Mats are stored at a temperature of 20-25 degrees.
• Before using coatings that were brought in from the cold, you need to let them warm up in a warm room for about a day.
• Oily surfaces are immediately cleaned without using alcohol solutions to prevent the rubber from becoming hard.
• Personnel should not use wet surfaces during work.
• In cold rooms, a specialized dielectric mat, gloves, and stands are used. There are products that can withstand temperatures from -50 to +80 degrees.

Additional protections

When working in high-voltage cabinets with an electric winch, it is necessary to use insulating devices:

• gloves are used not only for measurements; welders wear them to insulate them from the ground;
• boots, rubber boots, galoshes;
• for measuring electrical parameters;
• a protective mask must be worn to protect the eyes;
• a plastic helmet is a dielectric;
• specialized electric arc kits;
• When carrying out PPR, current-carrying parts located in the work area are covered with rubber dielectrics.

Personnel servicing high-voltage installations are given specialized heat-resistant suits. To work at height, ladders and stepladders with dielectric inserts are used.

172. Dielectric rubber mats (mats) are tested by passing them at a speed of 2-3 cm at 1 sec between cylindrical electrodes.

To measure the currents flowing through the mat, in electrical circuit The ammeter turns on. The breakdown of the mat is recorded using a voltmeter.

It is allowed to test mats in a metal bath filled with water, just like rubber insulating pads (see paragraph 179).

173. The amount of current flowing through the mat should not exceed 1 mA at 1000 V test voltage.

The test voltage is set:

a) for dielectric mats manufactured in accordance with GOST for electrical installations with voltages above 1000 V - 20 kV ;

b) for rugs used in electrical installations with voltages up to 1000 V -3.5 kV .

Testing of insulating supports

174.- Electrical and mechanical tests of stands are carried out only after they have been manufactured and overhauled.

175. Testing of insulating stands for mechanical strength is carried out before the electrical test and consists of subjecting the assembled insulating stand to a uniformly distributed load of 350 kg/m 2 for at least 1 min. In this case, there should be no deflection of the stand flooring and other deformations - cracks, violations of the integrity of the support insulators, weakening of the connection between individual parts of the flooring, kinks, etc.

After manufacturing, the platforms are also tested for overturning (clause 106).

If any of the listed defects are detected, the insulating stand will be rejected.

176. Electrical testing of insulating supports consists of testing support insulators.

When performing electrical tests, the following conditions must be met:

a) the test voltage must be 40 kV regardless of the voltage of the electrical installation for which the stands are intended;

b) the duration of the test should be 1 min;

c) supporting insulators of insulating stands can be tested either separately or together with the flooring; in the latter case, before testing, the support insulators are connected by wire along the upper and lower bases separately, after which voltage is applied from one of the terminals of the test transformer to the upper bases, and from the other terminal directly or through the ground to the lower bases of the insulators.

177. While the insulators are under voltage, it is necessary to carefully monitor their condition: if sliding discharges or overlaps occur, the stand is rejected.

After the test, a test stamp is placed on the support insulators (at the ends).

Rejected support insulators are broken, the insulating supports are completely or partially repaired, after which they are subject to retesting,

Testing of insulating pads

178. Insulating linings made of bakelite, textolite, plastics, etc. must be tested for breakdown and for overlapping on the surface with a voltage of 20 kV within 5 min.

To test the pads for breakdown, each electrode must have

the surface of contact with the lining is at least 50% of one side surface of the lining.

Testing of linings for surface overlap should be carried out using electrodes of any size applied to each side of the lining.

The distance between the electrodes along the surface of the pad should be no more than the distance between the poles of the disconnector for a voltage of 10 kV.

The condition of the linings during testing should be monitored in accordance with the instructions in paragraph - 146.

179. After manufacturing, insulating rubber pads “must be tested at a voltage of 5 kV in a special metal bath.

Water poured into the bath over the lining should not reach the edges of the lining on the outer and inner sides by 50 mm. One terminal of the test transformer is connected to a grounded bath, the second is connected to an electrode placed in water on top of the pad.

To measure the current flowing through the pad, a milliammeter is connected to the step-up winding circuit of the transformer. The current should not be more than 5 mA. Test duration 1 min.

You can also test by passing pads between cylindrical electrodes, in the same way as dielectric mats are tested (section 172).

Periodic tests of rubber pads are carried out, as indicated above, in a bath by applying a voltage of 3.5 kV for 1 minute. The current should not be more than 3.5 mA.