SIP cable

SIP cable is a self-supporting insulated wire for transmitting( usually three-phase) low voltage up to 600 V( phase voltage) / 1 kV( line voltage) over long distances and for local distribution. He came into use in exchange for naked for several reasons. In the Russian Federation, the use is made in accordance with GOST 52373. Within the framework of the document, a similar abbreviation is used for marking protected cables of high voltages up to 35 kV( linear), therefore, the products are also referred to as CIP.

The history of the invention of

CIP cables The first patent on the topic in question is considered to be US960291 A, declared on December 1, 1908. This is obvious for a simple reason: the text explicitly states that previously, for supporting, aerial cables were tied to a rope that supported them. Thus it was possible to avoid a cliff. Swedish engineers Reynold Fridtjof Reynoldson and Carl Emil Egner figured out how to simplify cable production and laying lines.

It was proposed to enclose insulated from each other with paper or other means of a core, a solid rope, into a single lead shield. On the material of the caliper is silent, but it is assumed strength. Attention is drawn to the fact that by that time there already existed polymers that were not really studied. The shell offered lead.

Since 1868, cellulose nitrate has been used as a material for making billiard balls. John Wesley Hyat was looking for. .. an insulator for electrical appliances, and helped players. In 1862, he guessed to mix cotton pyroxin with nitric acid and camphor. The result was celluloid, which today is used to make balls used in table tennis. Leo Hendrik Baekland received the first phenol-formaldehyde plastics in 1909, the material was clearly not suitable for use as cable insulation for objective reasons. If we touch upon the question of chemistry extensively, today the process of photodepolymerization of an insulator cannot be overcome in CIP cables.

A little talk about the initial steps for the use of inventions. It is believed that the first serious networks on low-voltage cables CIP began to be used in France, it happened in the 50s of the XX century. Since 1966, Electricite ’de France has been using an aluminum core, and since 1977, cross-linked polyethylene insulation. In the 10s of the 21st century, 140,000 km of CIP cable lines were laid in France, the figure is constantly increasing.

With regard to Scandinavia, the birthplace of the invention, most of all the novelty has found applications in Finland, where the technique of isolated air networks has been mastered since the 60s of the 20th century. According to some data, SIP cable accounts for up to 75% of the total length of routes. In Sweden, the development dates are similar, but the share is slightly lower - 40 percent( 1984).Other countries are in no hurry to switch to CIP cables.

Electrical energy and CIP

In the foreseeable future, electric energy will become an irremovable source for the operation of enterprises, factories, and organization of human leisure.

According to GOST 52373 self-supporting insulated wires( SIPs) are designed to transmit phase voltages up to 600 V. All others are called protected within the document. The division is made by the size of the cross section of the core, the rated voltage and the type of insulation. In SIP is called working, in others - protective. The State Standard classifies wires as follows:

• According to the design, the following types are distinguished: with insulated( 2), uninsulated( 1) neutral or without a specified core( 4), sealed( g) and with protective insulation( 3).
• Number of cores: 1, 2, 3 or 4. The phase section is selected from the range: 16, 25, 35, 50, 70, 95, 120, 150, 185 or 240 square millimeters, and zero( serving as a support) - 25,35, 50, 54.6, 70, 95. In the absence of a neutral, only the first two digits from the presented ones are possible for other lines. In wires with a zero core, there may be auxiliary( lighting or control circuit) with a number from 1 to 3 and a cross section of the following: lighting - 16, 25, 35;control - 1.5, 2.5, 4 square millimeters.

The CIP abbreviation is included in the labeling of the wire; people call the cable without the usual slang in such cases. The type is added through the dash( see above), then the number, phase section, zero, and( through the plus sign) auxiliary conductors( by the presence of those) are indicated. The marking is completed by the operating voltage( in kV: phase / linear - see above) and in some cases by the number of technical specifications for the product, containing tables with the decoding of parameters by type. Including: specific weight, breakage strength, etc.

Most of the parameters specified in GOST are only interesting for manufacturers - the number of wires in the core or the twist pitch. However, some take into account the electricians - the force to break and shear the insulation. The tables in the figure are for reference only. In carrying out specific manipulations with the laying of networks should be guided by the state standard, the text of which is periodically updated.

Electrical resistance is given in terms of 1 km for normal conditions( room temperature), and tensile forces will help to correctly determine the methods of laying the line. According to international agreements, the phases and the neutral are labeled in a certain way:

1. The polymer insulator of the first phase is red, with one longitudinal projecting strip.
2. The polymer insulator of the II phase is white and has two longitudinal protrusions.
3. III phase - blue, three protrusions.
4. Neutral has a dye-free multi-lane isolator.

The advantages of

CIP cables with non-insulated

power lines To understand the advantages of using CIP cables, let's talk about other methods of energy transmission over a distance. In order to save each phase goes on the bare wire. It is possible to reduce the price of braid. We have to put porcelain linear insulators, it is still less expensive. The frequency of 50 Hz is weakly radiated into space, and tangible interference with the laying of such networks is rare.

The phase conductors run in spans from above, directly below the lightning protection cable( on lines above 35 kV), below them( if necessary) - neutral. Suspensions can be vertical supporting( 1 pc per pole), or tension( double, with a loop of wire laid between them).Support with the first kind of insulators are called intermediate, with the second - anchor. Support suspension in case of breakage or displacement of loads slightly deviate to the side, spring and saving columns from falling. Anchor supports block the spread of deforming forces further along the network, by definition, more powerful( supplied with bolts).They are used on cornering lines with an angle of more than 10 degrees.

Each support is grounded: a piece of rail or metal pin is dug at the base. On this circuit it is possible to get the body of the distribution panel, after measuring the resistance. Grounding is required for proper operation of relay protection systems. Copper and aluminum are used as the core material as the inexpensive metals available to electrical engineering. Due to its cheapness, the aviation metal is taken by half a section larger to ensure proper strength, but weighs 60% less. Pure aluminum is used with a proportion of pure substance from 99.5 to 99.85%.

To ensure the mechanical strength of high-voltage lines( AHS), a steel core is inserted into the center. Examples of the performance of wires are present in GOST 839. The disadvantage of aluminum alloys is considered to be relatively strong corrosion, which, depending on the terrain, is 0.02-0.8 micron / year. To eliminate the defect go to different measures:

1. In the wires of the ASCS, the interwire space is filled with neutral lubricant.
2. In the wires of the automatic transmission, ASKP - the same, but the lubricant is of high heat resistance.
3. In ASK wires, the core of steel is additionally insulated with two polyethylene terephthalate tapes.

in sip otherwise. There, the conductors are intertwined and enclosed in a common polymer insulation. Neutral often goes in the middle. There are a number of drawbacks to bare wires in front of CIP:

1. Step voltage can kill small piglets that choose the gear line as their favorite gathering place. The voltage is so high that it is hypothetically possible that a situation will arise when the difference between the points located at a distance of a few centimeters becomes killing.
2. At break of a neutral it is difficult to reveal breakage. Such situations are hypothetically dangerous, the equipment begins to work in the wrong mode. Changes the direction of current movement on certain fractions of the frequency period.
3. The laying of power lines with bare wires requires an obligatory cleaning of the terrain: everyone has seen glades cut under high-voltage power lines so that discharge cannot reach discharge through wet branches and the ground in wet weather. Natural interference causes the breakage of the neutral, as mentioned above.
4. A strong wind can overlap the wires. Even if it does not last long, an arc will slip through and sparks will form. In a dry and hot season, it is likely to cause a fire.

All of the above leads to the fact that linear insulators have to be installed, and the phase conductors and the neutral are separated as far as possible. That naturally leads to the need to use crossbars( in the foundation) in order to increase the area of ​​support.

The differences between

CIPs From the above, the usual common considerations highlight the key advantages of CIP cable:

1. No need for powerful line insulators.
2. Comparative safety for service personnel.
3. Reducing the width of the route due to a combination of all the veins in the same insulation.
4. Non-critical to weather conditions, no corrosion, sparking.
5. No need for thorough cleaning.
6. Theft of electricity( a cape of conductors) becomes difficult, and for inspection - visually easily distinguishable.
7. Harmless to animals and birds, other representatives of the fauna.
8. Resistance to natural disasters, primarily by airflow overlap.
9. Easy route installation and material savings in production. The process is so simple that the usual case is this: a hook is screwed into the wall, to which a cable clings. Sometimes the insulation is crimped with a clamp.

There are also disadvantages, most of which relate to lines of considerable length. In the first place - a relatively large running weight, due to which the support must be set more often. If these are wooden poles, the process is relatively simple, but concrete structures are expensive, they are built more expensive. The cost of SIP cable is relatively high, but private owners have no other choice for local wiring.

No one can cancel the depolymerization process, it is obvious that today CIP cables remain the only solution for private homeowners. As for the industrial scale, it requires enhanced insulation. However, the chemistry of polymers does not stand still.