JP2898880B2 - Crosslinked polyethylene insulated power cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is a high temperature, has excellent electrical characteristics even under a high electric field, to crosslinked polyethylene insulated power cable using a suitable polyethylene emissions as a material for the insulator layer of the power cable.

[0002]

2. Description of the Related Art As an electric power cable, an OF cable having an insulating layer made of kraft paper or semi-synthetic paper impregnated with insulating oil and a cross-linked polyethylene insulated power cable having an insulating layer made of cross-linked polyethylene are used. ing. Of these power cables, cross-linked polyethylene insulated power cables are becoming widely used because they are easy to maintain and have low dielectric loss. And, with the expansion of the field of use, the use environment is under increasing pressure.

Meanwhile, in the case of the above-mentioned crosslinked polyethylene insulated power cable, the average operating electric field shifts to a higher level and the temperature during operation increases to a higher level in response to the increase in the pressure. Go. For example, 275
In a kV class crosslinked polyethylene insulated power cable, the average operating electric field is about 6 kV / mm and the operating temperature is about 9 kV / mm.
Increase to 0 ° C.

[0004] When the operating electric field increases in this manner, the electric field concentration on the defective portion existing in the insulator layer further increases, and in some cases, several tens of kV /.
mm. When the insulator layer of the crosslinked polyethylene is placed under a high temperature and a high electric field, the dielectric loss tangent (tan) is increased.
δ) rises and the insulator layer generates heat, and its dielectric breakdown value is greatly reduced. In addition, the dielectric loss increases with an increase in tan δ, and as a result, the power transmission capacity of the power cable may decrease.

In order to maintain high insulation performance over a long period of time, it is necessary to keep tan δ at a low level even when an electric field of about twice the average operating electric field is applied.
Therefore, in order to manufacture a crosslinked polyethylene power cable having a stable insulation performance and a large power transmission capacity, it is necessary to configure the insulator layer with crosslinked polyethylene having a low tan δ even at a high average operating electric field. Will be needed.

[0006]

SUMMARY OF THE INVENTION The present invention meets the above-mentioned demands for crosslinked polyethylene power cables, and has an average operating electric field of 10 kV / mm or more at a high temperature, even when an electric field twice as large is applied. , tan [delta has a high insulation performance without increasing, and an object thereof is to provide a cross-linking polyethylene power cable capable large capacity transmission.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above-mentioned object, and have obtained an uncrosslinked polyethylene which is a starting material of a crosslinked polyethylene constituting an insulator layer. The relationship between properties and tan δ was examined. As a result, as described later, a specific high-pressure low density polyethylene have found facts that it is useful for achieving the above objects, led to the development of cross-linking polyethylene insulated power cable of the present invention.

That is, the crosslinked polyethylene insulated power cable of the present invention comprises: (1) a crosslinked polyethylene insulated power cable having an average operating electric field of 10 kV / mm or more, wherein the insulator layer is synthesized by radical polymerization of ethylene; The following properties: a, MFR 0.1 to 10 g / 10 min; b, density 0.915 to 0.935 g / cm ³ ; c, wave number 1725 ± 4 cm in infrared absorption spectrum
The absorbance of a ketone-type carbonyl group having a peak at a position of ^-1 is 0.03 to 1.0, and the absorbance of an ester-type carbonyl group having a peak at a wave number of 1743 ± 4 cm ^-1 is 1.0.
And the absorbance based on other carbonyl groups is less than 0.03 (the absorbance referred to here is
Ri value Der when converted into per fee 1 mm, the unit is (- /
mm) and made); a cross-linked polyethylene insulated power cable, characterized in that it is formed by crosslinking of the low-density polyethylene having a (2) average operating electric field 10 kV / mm or more crosslinked polyethylene power A cable, the insulator layer of which is synthesized by radical polymerization of ethylene, and having the following properties: a, MFR of 0.1 to 10 g / 10 min; b, density of 0.915 to 0.935 g / cm ³ ; d, the density of the target low-density polyethylene was determined to be D (g / cm) in a measurement using a cross-separation apparatus combining temperature-rise elution fractionation and gel permeation chromatography.
³ ) The content of components eluted at a temperature equal to or higher than the elution temperature T (° C.) calculated based on T = 687 × D-547 is 3% by weight or less; A crosslinked polyethylene insulated power cable characterized by being formed of a crosslinked body, (3) a crosslinked polyethylene power cable having an average operating electric field of 10 kV / mm or more, wherein the insulator layer is formed by radical polymerization of ethylene. And the following properties: a, MFR 0.1 to 10 g / 10 min; b, density 0.915 to 0.935 g / cm ³ ; c, wave number 1725 ± 4 cm in infrared absorption spectrum
The absorbance of a ketone-type carbonyl group having a peak at a position of ^-1 is 0.03 to 1.0, and the absorbance of an ester-type carbonyl group having a peak at a wave number of 1743 ± 4 cm ^-1 is 1.0.
And the absorbance based on other carbonyl groups is less than 0.03 (the absorbance referred to here is
Ri value Der when converted into per fee 1 mm, the unit is (- /
d ) In a measurement using a cross-separation apparatus that combines temperature-rise elution fractionation and gel permeation chromatography, the density of the target low-density polyethylene is D (g / cm).
³ ) The content of components eluted at a temperature equal to or higher than the elution temperature T (° C.) calculated based on T = 687 × D-547 is 3% by weight or less; It is a crosslinked polyethylene insulated power cable characterized by being formed of a crosslinked body.

The polyethylene used as the material of the insulator layer in the present invention is a low-density polyethylene synthesized by high-pressure radical polymerization of ethylene. These low-density polyethylenes have a MFR (melting flow rate) of 0.1 to 10 g / 10 minutes. Preferably 0.7 to 5 g / 10 minutes, particularly preferably 0.8 to 3
g / 10 minutes.

[0010] If the MFR is too high, the melt tension is lowered, so that it is practically difficult to form an insulator layer during the production of a power cable. If used, the work of melt-extrusion coating of the insulator layer on the conductor becomes difficult and causes a decrease in productivity. Here, the MFR is a value measured according to JIS K7210.

The low density polyethylene has a density of
0.915 to 0.935 g / cm ³ . Preferably,
0.917 to 0.928 g / cm ³ , particularly preferably 0.918 g / cm ³
~ 0.924 g / cm ³ . If the density of the polyethylene is too high, the flexibility of the formed insulator layer is reduced, and there is a difficulty in handling in practical use as a power cable. This is because the actual use becomes difficult because there are too many unnecessary components.

The density referred to here is JIS K7112
Means a value measured in accordance with Further, the low-density polyethylene used in the present invention has a wavenumber of 1725 in infrared absorption spectrum measurement with a wavenumber resolution of 4 cm-1 or more.
The absorbance of the ketone-type carbonyl group having a peak at a position of ± 4 cm −1 is 0.03 to 1.0, preferably 0.03 to 1.0.
~ 0.5, the absorbance of the ester type carbonyl group having a peak at the position of the wave number 1743 ± 4 cm -1 is 1.0 or less,
Preferably 0.5 or less, wave number 1743 ± 4 cm
The peak at the position of -1 may not be present,
And the absorbance based on other carbonyl groups is 0.03
It has a property c that is smaller, preferably such that there is no peak. The property c hardly changes even if the polyethylene is crosslinked.

The absorbance referred to here is 1 mm for a measurement sample.
It is a value converted to a hit, and the unit is-/ mm. The insulator layer made of polyethylene that does not satisfy the above property c is affected by the carbonyl group, and tan δ increases, especially at high temperature and high electric field, and accordingly, the dielectric loss of the insulator layer increases and the power consumption increases. The transmission capacity of the cable will be reduced. Further, in such a power cable, heat generation due to an increase in tan δ significantly reduces a dielectric breakdown value at a high temperature.

The property d of the low-density polyethylene used in the present invention is measured by using a cross-separation apparatus (hereinafter referred to as CFC) in which temperature-rise elution separation and gel permeation chromatography are combined. In the relationship between the elution temperature T calculated by the equation (1) and the density D of the low-density polyethylene, components eluted at a temperature equal to or higher than the elution temperature T are 3% by weight or less based on the total elution amount. , Preferably 1.5% by weight or less.

The measurement using CFC in the present invention is performed as follows using a commercially available device. That is, based on the principle described in J. Appl. Polym. Sci., 26, 4217 (1981), first, the target polyethylene is completely dissolved at 140 ° C. and 1 ° C. from 140 ° C. to 0 ° C.
After cooling at 0 ° C./min and holding at 0 ° C. for 30 minutes, measurement is performed under the following conditions. By this measurement, the concentration of the components eluted at each temperature after the temperature is increased stepwise is detected, and the composition distribution of the polyethylene is measured by plotting the relationship between the elution amount and the elution temperature.

The insulator layer made of polyethylene that does not satisfy the above property d has a high temperature and a high electric field.
As nδ increases, the dielectric loss of the insulator layer increases and the transmission capacity of the power cable decreases. In addition, heat generation due to an increase in tan δ significantly reduces a dielectric breakdown value at a high temperature. Therefore, in an ultra-high voltage power cable operated under a high temperature and a high electric field, it is preferable to use polyethylene having both properties c and d as the resin for the insulator layer.

Further, the polyethylene for the power cable insulator layer of the present invention has one peak of the differential elution curve showing the relationship between the elution temperature and the elution amount in the measurement using the above-mentioned CFC.
Ratio of the area (S _H ) on the high temperature side of the portion surrounded by the tangent line at the height of / 2 and the differential elution curve and the total area (S _A ) of the peak [S = (S _H / S _A )] × 100: unit%] is 8% or less, preferably 7% or less, and particularly preferably 6% or less.

The polyethylene used in the present invention is, for example,
Chem. Eng. , 113 Dec (19), 1966.
It can be produced by a known method described in a document such as Specifically, first, ethylene gas purified in an ethylene plant and unreacted ethylene gas circulated from a reactor as described later are sent to a primary compressor, where about 200 kg / cm ² After compressing to the degree, it is sent to the next secondary compressor.

In this secondary compressor, 1500-35 with unreacted ethylene gas circulated from the reactor described later.
After compression to about 00 kg / cm ² , the mixture is press-fitted into a reactor together with a radical initiator and the like, and the radical polymerization reaction proceeds at a maximum reaction temperature of 150 to 350 ° C. in this reactor. At this time, since only about 18 to 20% by weight of the supplied gas is polymerized, this polymerized polymer and unreacted ethylene gas are separated by a high-pressure separator of about 200 kg / cm ² , Separate with a low pressure separator of about 0.3 kg / cm ² .

The unreacted ethylene gas separated by the high-pressure separator is returned to the secondary compressor, and the unreacted ethylene gas separated by the low-pressure separator is supplied to a surge tank,
Via compressor, a portion is returned to the primary compressor described above with refining ethylene gas. Were pelleted polymerization polymer separated in the low pressure separator pelletizer
Obtain low density polyethylene. In addition, radical polymerization initiator
As organic peroxide and oxygen are known,
It is preferably a peroxide.

The power cable of the present invention is synthesized as described above, and is made of a high-pressure low-density polyethylene having the above-mentioned properties a, b, c and / or d as a base resin. , T-
Butylperoxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexene, 2,4-dichloro- An organic peroxide such as benzoyl peroxide is compounded as a cross-linking agent, and the resulting mixture is coated on the outer periphery of the conductor to form an uncross-linked insulator layer. It can be produced by converting high density polyethylene into a crosslinked product.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example 1 Based on the method described in Chem. Eng., 113 Dec (19), 1966, the following conditions: reactor, tubular reactor; reaction pressure, 2800 kg
/ cm ² ; Maximum reaction temperature, 280 ° C; Ethylene supply rate, 35 kg / hr
A polymerization initiator, t-butyl peroxybenzoate; a supply amount of the polymerization initiator, 1.45 g / hr;

With respect to the obtained polyethylene, measurement using CFC, MFR measurement, density measurement, IR
Analysis was carried out. CFC measurement: Model, CFCT-150A (manufactured by Mitsubishi Yuka Co., Ltd.) Solvent, o-dichlorobenzene Flow rate, 1 ml / min. Concentration, 4 mg / ml injection amount, 0.4 ml column, AD80M / S, 3 tubes (manufactured by Showa Denko KK) Elution temperature, 0 ° C, 5 ° C, 10 ° C, 20 ° C, 30 ° C, 40
° C, 45 ° C, 49 ° C, 52 ° C, 55 ° C, 58 ° C, 61
° C, 64 ° C, 67 ° C, 70 ° C, 73 ° C, 76 ° C, 79
° C, 82 ° C, 85 ° C, 88 ° C, 91 ° C, 94 ° C, 97
° C, 100 ° C, 120 ° C, 140 ° C Elution time, 39 minutes Detector, infrared spectrophotometer Detection wavelength, 3.42 µm MFR: Conforms to JIS K7210 Density: Conforms to JIS K7112 IR analysis (for carbonyl groups in polyethylene) Identification): Using 1600 series FT-IR manufactured by Perkin Elmer Co., Ltd., wave number resolution 4 cm ^-1 , integration frequency 64 times, sample thickness about 1
The measurement was performed under the condition of mm, and the presence or absence of a peak and the absorbance at each wave number shown in Table 1 were measured.

With respect to 100 parts by weight of this polyethylene, 2 parts by weight of dicumyl peroxide (crosslinking agent), 4,4'-
Thiobis- (6-t-butyl-3-methylphenol)
(Antioxidant) 0.3 part by weight is blended, and this mixture is mixed with 15 parts by weight.
After extrusion-coating as an insulator layer together with an inner semiconductive layer and an outer semiconductive layer on a 0 mm ² conductor, a cross-linking treatment was performed to produce a power cable.

With respect to this power cable, the average electric field was 5 kV / mm and 10 kV / m at room temperature and 90 ° C.
m, tan δ at 15 kV / mm, 20 kV / mm and 25 kV / mm were measured. In addition, as a measuring device,
Automatic Shuring Bridge manufactured by Soken Electric Co., Ltd. (Model:
DAU-PSC-UA) and the measurement frequency is 50 Hz
And

The results are shown in Table 1. Example 2 The conditions for the radical polymerization reaction were as follows: reactor, autoclave reactor; reaction pressure, 2000
kg / cm ² ; Maximum reaction temperature, 235 ° C; Ethylene supply rate, 45 kg / hr
A polymerization initiator, t-butyl peroxyisobutyrate and t
Butyl peroxypropyl carbonate; feed of polymerization initiator, 1.28 g / hr;
Polyethylene was synthesized in the same manner as in Example 1.

Using this polyethylene, a power cable was manufactured under the same conditions as in Example 1. The CFC measurement, MFR, density, IR analysis, and tan δ measurement of the power cable of this polyethylene were performed in the same manner as in Example 1. The results are shown in Table 1. Examples 3 and 4 and Comparative Examples 1 to 4 An electric power cable was manufactured and evaluated in the same manner as in Example 1 except that polyethylene having the properties shown in Table 1 was used. The results are shown in Table 1.

[0028]

[Table 1]

As is clear from the results in Table 1, in the present invention ,
Insulation layer made of polyethylene with specified properties
The formed power cable has an average electric field of 20 kV /
mm as well as at 25 kV / mm
There is almost no increase in nδ. Therefore, the power cable of the present invention can secure long-term stability of insulation performance even in an ultrahigh-voltage power transmission application in which the average operating electric field is 10 kV / mm or more.

[0030]

As apparent from the above description, in the present invention
A power cable in which an insulating layer made of a polyethylene-based resin having specified properties is formed has almost no increase in tan δ even under a high temperature and a high electric field. Therefore, the dielectric breakdown value at high temperature is large,
It that-out is in <br/> functioning as a large power cable transmission capacity.

Continued on front page (72) Inventor Koji Yamamoto 1 Toho-cho, Yokkaichi-shi, Mie Prefecture Mitsubishi Yuka Co., Ltd. Yokkaichi Research Institute (72) Inventor Mitsugu Ishioka 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Yokkaichi Co., Ltd. Within the research institute (72) Inventor Setsuo Goto 1 Toho-cho, Yokkaichi-shi, Mie Pref.

Claims (3)

(57) [Claims] 1. A crosslinked polyethylene power cable having an average operating electric field of 10 kV / mm or more, wherein an insulating layer thereof is synthesized by radical polymerization of ethylene, and has the following properties: a, MFR of 0.1 to 10 g. B, density 0.995 to 0.935 g / cm ³ ; c, wave number 1725 ± 4 cm in infrared absorption spectrum
The absorbance of a ketone-type carbonyl group having a peak at a position of ^-1 is 0.03 to 1.0, and the absorbance of an ester-type carbonyl group having a peak at a wave number of 1743 ± 4 cm ^-1 is 1.0.
And the absorbance based on other carbonyl groups is less than 0.03 (the absorbance referred to here is
Ri value Der when converted into per fee 1 mm, the unit is (- /
mm)) ; a crosslinked polyethylene insulated power cable formed of a crosslinked product of low density polyethylene having: 2. A crosslinked polyethylene power cable having an average operating electric field of 10 kV / mm or more, wherein an insulating layer thereof is synthesized by radical polymerization of ethylene and has the following properties: a, MFR of 0.1 to 10 g. B, density: 0.915 to 0.935 g / cm ³ ; d, low-density polyethylene of interest in measurement using a cross-separation apparatus combining temperature-rise elution fractionation and gel permeation chromatography Of D (g / cm
³ ) The content of components eluted at a temperature equal to or higher than the elution temperature T (° C.) calculated based on T = 687 × D-547 is 3% by weight or less; A crosslinked polyethylene insulated power cable formed of a crosslinked body. 3. A crosslinked polyethylene power cable having an average operating electric field of 10 kV / mm or more, wherein an insulating layer thereof is synthesized by radical polymerization of ethylene, and has the following properties: a, MFR of 0.1 to 10 g. B, density 0.995 to 0.935 g / cm ³ ; c, wave number 1725 ± 4 cm in infrared absorption spectrum
The absorbance of a ketone-type carbonyl group having a peak at a position of ^-1 is 0.03 to 1.0, and the absorbance of an ester-type carbonyl group having a peak at a wave number of 1743 ± 4 cm ^-1 is 1.0.
And the absorbance based on other carbonyl groups is less than 0.03 (the absorbance referred to here is
Ri value Der when converted into per fee 1 mm, the unit is (- /
d ) In a measurement using a cross-separation apparatus that combines temperature-rise elution fractionation and gel permeation chromatography, the density of the target low-density polyethylene is D (g / cm).
³ ) The content of components eluted at a temperature equal to or higher than the elution temperature T (° C.) calculated based on T = 687 × D-547 is 3% by weight or less; A crosslinked polyethylene insulated power cable formed of a crosslinked body.