JPH06251624A - Insulation composition and power cable - Google Patents

Abstract

PURPOSE:To provide a power cable having a small dielectric loss, composed of an insulation composition having a small dielectric loss and an insulator available therefrom. CONSTITUTION:This insulation composition is made of polyethylene based polymer, and manufactured by a high pressure method where ethylene gas is compressed to high pressure on the operation of a booster compressor using a fluorocarbon lubricant as lubricating oil. As a result, polyethylene does not contain any polyether compound as an impurity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating composition which is an insulator having a small dielectric loss, and a power cable using the insulating composition.

[0002]

2. Description of the Related Art Conventionally, a cross-linked polyethylene (XLPE) has been used as an insulator used for a power cable and its accessories.
Is widely used. Low density PE (LDPE) polymerized by a high pressure method is generally used for polyethylene (PE) as a base polymer of this XLPE. This high-pressure method uses ethylene gas at high pressure (1000 to 3000).
This is a method in which PE is polymerized in a reaction tube after being compressed to Kg / cm ² ), but an extremely small amount of impurities may be mixed in during the manufacturing process.

Examples of such trace impurities include lubricant impurities from an ethylene gas booster compressor (compression cylinder) and impurities from a reaction tube wall. Here, as the lubricant used in the booster compressor, a polyether-based water-soluble lubricating oil is generally used. This is because when hydrocarbon-based lubricating oil is used, carbon sludge is deposited on the packing and sliding surface of the booster compressor, shortening the maintenance interval.

By the way, a power cable using this crosslinked polyethylene is called a CV cable, and generally its electrical tan δ (dielectric loss tangent) is low, and therefore the dielectric loss is also small, so that the energy loss of the cable is also small. ing.

[0005]

However, the above-mentioned C
Even in the case of a V cable, particularly when transmitting a high voltage, that is, when the electric field or temperature of the ultra-high voltage CV cable is used, the electrical tan δ is increased, and the dielectric loss is increased accordingly. There was a problem that the loss would increase.

[0006]

In view of the above problems, the present inventor has conducted diligent research to investigate the cause of the increase in electrical tan δ in a CV cable, and as a result, although a detailed theory is unknown, polyethylene is produced. When the polyether-based lubricating oil of the booster compressor used at the time of mixing is mixed as an impurity in polyethylene, the above-mentioned ta
It was clarified that an increase in nδ was observed, and the present invention was completed.

That is, in the insulating composition according to the first aspect of the present invention, a polyethylene-based base produced by a high pressure method in which ethylene gas is compressed to a high pressure by a booster compressor using a hydrocarbon lubricating oil as a lubricating oil is used. The use of a polymer was used as a means for solving the above problems. In the power cable according to claim 2, the insulator obtained from the insulating composition according to claim 1 is used as a means for solving the problems.

The present invention will be described in detail below. In order to identify whether polyethylene was obtained by using a hydrocarbon-based lubricating oil in a booster compressor or a polyether-based lubricating oil during its production Can be determined by whether or not absorption is observed at around 320 nm when a water extract from a polyethylene compound is subjected to ultraviolet absorption analysis.

That is, when subjected to ultraviolet absorption analysis,
Those with absorption around 320 nm were obtained by using polyether type as lubricating oil, while those without absorption around 320 nm were almost hydrocarbon type with lubricating oil. Can be specified as obtained by using. The polyethylene obtained by using the hydrocarbon lubricating oil is shown in the examples as compared with the polyethylene obtained by using the polyether lubricating oil, that is, the polyether lubricating oil is contained as an impurity. It was found that the tan δ was small.

[0010]

[Example] When polyethylene is produced by the high pressure method, a low density polyethylene compound (example product) produced by using a hydrocarbon type as a lubricating oil for an ethylene gas booster compressor and a polyether type are used. Low-density polyethylene compound manufactured using (comparative example product)
And prepared.

[Ultraviolet Absorption Analysis] In order to analyze whether the obtained compound contains a polyether compound, a qualitative analysis using a cobalt thiocyanate method was carried out as follows. (Preparation of Measurement Sample) First, a part of the compound was pulverized, and 500 g of the pulverized product was sampled. Then 1 for each of these samples
Pure water was added in an amount of 000 g each, and the mixture was further heated and subjected to reflux extraction treatment for 48 hours. After extraction under reflux, each is filtered,
1000 ml of the filtrate was distilled under reduced pressure using an evaporator, and accurately concentrated to 50 ml to obtain these as measurement samples.

(Preparation of Cobalt Ammonia Thiocyanate Aqueous Solution) Ammonium thiocyanate [NH ₄ SCN] 6.
2 g and cobalt nitrate [Co (NO ₃ ) ₂ ] 2.8 g were dissolved in pure water to prepare 100 ml of an aqueous solution of cobalt thiocyanate. (Preparation of Sample for Ultraviolet Absorption Analysis) 50 ml of the measurement sample prepared above and aqueous solution of ammonia cobalt thiocyanate 1
5 ml and 20 g of sodium chloride (NaCl) were placed in a separatory funnel, shaken and stirred until NaCl was completely dissolved, and then left standing for 15 minutes. Next, exactly 30 ml of 1,2-dichloroethane was added to each of the separating funnels, and the mixture was shaken and stirred for 1 minute and allowed to stand still to separate two layers. Then
The 1,2-dichloroethane (lower side) separated into two layers was separated and dehydrated by adding a small amount of anhydrous sodium sulfate. Further, the filtrate obtained by filtering this was used as a sample for ultraviolet absorption analysis.

(Ultraviolet absorption analysis) Two kinds of the obtained samples for ultraviolet absorption analysis were measured by a measuring instrument manufactured by JASCO Corporation [Ubest-50 U
V / VIS Spectrophotometer] to measure its absorbance. The measurement condition is a wavelength of 200
˜400 nm, scan speed 100 nm / min, and spectral bandwidth 2.0 nm. The measurement result of the sample from the example product is shown in FIG. 1, and the measurement result of the sample from the comparative example product is shown in FIG. From FIG. 1, in the example product, no peak was observed near 320 nm. On the other hand, from FIG. 2, in the comparative example product, the vicinity of 320 nm (300 nm to 320 n
A small peak P was seen in m).

[Measurement of tan δ] Next, tan δ of each of the example product and the comparative example product was measured as follows. First, to 100 parts by weight of each compound prepared above, 2 parts by weight of DCP (dicumyl peroxide) and 0.2 parts by weight of a thiobisphenol-based antioxidant were added and kneaded, and then formed into a sheet. Then, it was heated and crosslinked to obtain a crosslinked polyethylene sheet.

The two types of sheets thus obtained are shown in FIG.
The stainless electrodes 2a and 2b are brought into contact with both surfaces of the sample 1, and the sample 1 is grounded on the side of the electrode 2b.
The measuring device 3 was connected to the electrode 2b, and a high voltage was applied to the electrode 2a in this state to measure tan δ (dielectric loss tangent). (However, in FIG. 3, the effective portion thickness of Sample 1 is indicated by t.
As measurement conditions, the measurement temperature atmosphere was 90 ° C., and the applied stress was 20 kV / mm. ) Example product ta
nδ was 0.022%, while the tan δ of the comparative product was 0.041%. Therefore, no absorption was observed around 320 nm, and the tan δ of the example product containing no polyether compound was smaller than that of the comparative product, and thus it was confirmed that the insulating composition using this polyethylene had a small dielectric loss. Was done.

Further, an organic peroxide (DCP), an antioxidant, a filler, a coloring material and the like were appropriately added to the low density polyethylene compound of the example product to obtain an insulating composition of the present invention. Then, by forming such an insulating composition into a desired shape, that is, in the case of manufacturing a power cable or an accessory thereof, after molding into a desired shape as various insulators integrally incorporated therein, by heating in a crosslinking tower, , And cross-linked polyethylene (XLPE) which is an insulator. In a power cable using such an insulator, ta of the insulator
Since nδ (dielectric loss tangent) was small, the dielectric loss of the cable itself was small.

[0017]

As described above, the insulating composition according to claim 1 of the present invention is produced by a high pressure method in which ethylene gas is compressed to a high pressure by a booster compressor using a hydrocarbon lubricating oil as a lubricating oil. Since polyethylene is used as a base polymer, polyethylene does not contain a polyether compound as an impurity, and therefore tan δ (dielectric loss tangent) is caused by the polyether compound.
Can be suppressed, which makes it possible to manufacture an insulator with low dielectric loss. Claim 2
The described power cable is obtained from the insulating composition,
Since the insulator using the small dielectric loss is used, the energy loss of the power cable is small. Further, since the energy loss is small as described above, the power cable of the present invention is suitable for use in an ultrahigh voltage CV cable to which an ultrahigh voltage is applied.

[Brief description of drawings]

FIG. 1 is a view showing a result of ultraviolet absorption analysis of an example product.

FIG. 2 is a view showing a result of ultraviolet absorption analysis of a comparative example product.

FIG. 3 is a diagram for explaining a method of measuring dielectric loss tangent.

[Explanation of symbols]

 1 ... Sample, 2a, 2b ... Stainless electrode, 3 ... Measuring instrument.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Nakaji 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Kenji Matsui 1-1-5 Kiba, Koto-ku, Tokyo Shares Company Fujikura (72) Inventor Shiro Nakayama 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Takashi Takahashi 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Mitsutaka Yata 1-5-1, Kiba, Koto-ku, Tokyo, Fujikura Ltd. (72) Inventor Toshio Niwa 1-5-1, Kiba, Koto-ku, Tokyo, Fujikura Ltd.

Claims (2)

[Claims] 1. An insulating composition comprising polyethylene as a base polymer, wherein the polyethylene is produced by a high pressure method in which ethylene gas is compressed to a high pressure by a pressure-up compressor, and the pressure-up compressor contains hydrocarbon as a lubricating oil. An insulating composition comprising a system lubricating oil. 2. A power cable using an insulator obtained from the insulating composition according to claim 1.