JP2012220215A - Withstand voltage test method for plant joint part of long power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform, in small test voltage generation facilities, a withstand voltage test for a plant joint part of a long power cable formed by joining and elongating a required number of unit power cables having a continuously manufacturable length at a plant.SOLUTION: A plant joint part 1 to be tested includes a joint part external semiconducting layer 9 electrically edge-cut from the external semiconducting layers of both-side unit power cables 2A and 2B of the plant joint part, in the outer periphery of a reinforced insulation body 8, and a tentative shielding layer 10 in the outer periphery thereof. A withstand voltage test of the plant joint part is performed by applying a test voltage to the tentative shielding layer 10, with conductors 3 of the long power cables grounded.

Description

  The present invention relates to a withstand voltage test method for a factory joint portion of a long power cable obtained by lengthening a required number of unit power cables that can be manufactured in a continuous manner at a factory.

  Since submarine cables and the like need to be laid for a long distance, the length of cables shipped from the factory is extremely long, for example, several tens of kilometers or more. However, in the case of power cables, the length of cables that can be manufactured continuously is about several kilometers to several tens of kilometers, so long power cables that are several tens of kilometers or longer are long enough to be manufactured continuously. It is manufactured by joining the required number of unit power cables in the factory and lengthening them.

  Even in the case of such a long power cable, it is necessary to conduct a withstand voltage test to confirm the soundness before shipment from the factory. About each unit electric power cable, it is possible to confirm a soundness by performing a withstand voltage test with the conventional test voltage generation equipment at the stage of manufacture (before a joint). However, it is the factory joint part that needs the most soundness check rather than a unit power cable that can be manufactured mechanically in one continuous operation. The withstand voltage test of the factory joint part can be performed only in the state of a long power cable obtained by jointing a plurality of unit power cables.

  In general, a withstand voltage test of a power cable including a plurality of joint portions in the middle is performed by applying a test voltage to a conductor of the power cable (see Patent Document 1).

JP-A-5-87864

  However, the method of performing a withstand voltage test by applying a test voltage to the conductor of the power cable requires a test voltage generating facility with a large capacity according to the length of the power cable, so the total length is several tens of kilometers or more. In the case of a long power cable, in order to conduct a withstand voltage test by this method, a test voltage generating facility having an extremely large capacity is required. In addition, a compensation reactor is also required in the AC withstanding voltage test. For this reason, when a high voltage test of 100 kV or higher is performed on a long power cable with a length of about 10 km to 100 km, it cannot be handled by a general test voltage generation facility, and it is necessary to construct a new test voltage generation facility. Come out. The cost is over several hundred million yen, and it is not easy to conduct a withstand voltage test.

  An object of the present invention is to provide a method capable of performing a withstand voltage test on a factory joint portion of a long power cable with a test voltage generating facility having a small capacity.

  The withstand voltage test method according to the present invention is a withstand voltage test method for a factory joint part of a long power cable obtained by joining a unit power cable having a length that can be manufactured continuously and lengthening by joining at the factory. The outer semiconductive layer of the joint part electrically separated from the outer semiconductive layer of at least one unit power cable on both sides of the factory joint part on the outer periphery of the reinforcing insulator of the factory joint part to be tested And a temporary shielding layer is provided on the outer periphery thereof, and a withstand voltage test of the factory joint portion is performed by applying a test voltage to the temporary shielding layer in a state where the conductor of the long power cable is grounded. Is.

  The withstand voltage test method according to the present invention provides a stress relief cone composed of a semiconductive portion and an insulating portion from the outer periphery of the end of the joint portion external semiconductive layer to the outer periphery of the insulator of the unit power cable, The withstand voltage test can also be performed in a state where the above is relaxed.

  In this case, the semiconductive portion of the stress relief cone can be formed by semiconductive tape winding, and the insulating portion can be formed by insulating tape winding.

  Further, the stress relief cone may be formed of a rubber molded body in which the semiconductive portion and the insulating portion are integrally formed.

  According to the present invention, since the test voltage is applied to the temporary shielding layer of the factory joint section cut off from the outer semiconductive layer of the unit power cable with the conductor of the long power cable grounded, The withstand voltage test can be performed with a test voltage generating facility having a small capacity as compared with a method in which a voltage is applied to the entire length.

  Further, by attaching a stress relief cone to the edge cut portion, the electric field at the edge cut portion can be relaxed, so that a withstand voltage test with a high test voltage can be performed.

Sectional drawing which shows one Example of the test method which concerns on this invention. Sectional drawing which shows the other Example of the test method which concerns on this invention. Sectional drawing which shows the further another Example of the test method which concerns on this invention. Sectional drawing which shows the further another Example of the test method which concerns on this invention.

  FIG. 1 shows an embodiment of the present invention. In the figure, 1 shows a factory joint part of one of the long power cables formed by joining the required number of unit power cables (CV cables) of a length that can be manufactured in a continuous manner at the factory. Reference numerals 2A and 2B denote unit power cables connected by the factory joint section 1. The unit power cables 2A and 2B have the same structure and are composed of a conductor 3, an insulator 4, an external semiconductive layer 5, a metal shielding layer 6 and the like (other components are not shown). The factory joint part 1 is comprised from the conductor connection part 7, the reinforcement insulator 8, etc. (other structural members are abbreviate | omitting illustration).

  In order to conduct a withstand voltage test of the factory joint portion 1, the end portions of the unit power cables 2A and 2B are stripped of the metal shielding layer 6 and the external semiconductive layer 5 to expose the insulator 4 for a required length. Further, a joint portion external semiconductive layer 9 is provided on the outer periphery of the reinforcing insulator 8 by semiconductive tape winding. The joint portion outer semiconductive layer 9 is provided so that both ends thereof are located on the outer periphery of the cable insulator 4, but is electrically separated from the cable outer semiconductive layer 5. That is, an insulation interval sufficient to withstand the test voltage is provided between the end portion of the joint portion outer semiconductive layer 9 and the end portion of the cable outer semiconductive layer 5. In addition, a temporary shielding layer 10 is provided on the outer periphery of the joint portion outer semiconductive layer 9 with a metal foil or the like.

  After the factory joint section 1 is treated as described above, the conductor 3 and the metal shielding layer 6 of the long power cable are grounded, the temporary shielding layer 10 is connected to the test voltage generating facility 11, and the temporary shielding layer is connected. The withstand voltage test of the factory joint part 1 is performed by applying a test voltage to 10.

  In this way, since the test voltage only needs to be applied to the temporary shielding layer 10, the test voltage generating equipment 11 has a very small capacity compared to the case where the test voltage is applied to the entire conductor length of the long power cable. This can save a lot of cost.

  When the soundness of the factory joint part is confirmed by the above test, the temporary shielding layer 10 and the joint part external semiconductive layer 9 are removed, and the regular joint part external semiconductive layer and the metal shielding layer are provided to provide the factory joint part. To complete. If the factory joint part fails as a result of the withstand voltage test, the factory joint part is cut out and rejoined.

  FIG. 2 shows another embodiment of the present invention. In the embodiment of FIG. 1, the joint portion outer semiconductive layer 9 on the outer periphery of the reinforcing insulator 8 is cut off from the outer semiconductive layers 5 of the unit power cables 2A and 2B on both sides thereof. Only one end side of the semiconductive layer 9 is cut off from the outer semiconductive layer 5 of one unit power cable 2A, and the other end side is not cut off from the outer semiconductive layer 5 of the other unit power cable 2B. This is the case.

  For example, the withstand voltage test can be performed in such a configuration as follows. That is, out of the total length (several tens of kilometers) of the long power cable, when the length from the factory joint to be tested to one end of the long power cable is much shorter than the length to the other end, for example, the factory joint For example, one unit power cable 2B of 1 is located at the end of the long power cable. In this case, even if the withstand voltage test is performed in the configuration as shown in FIG. 2, the capacity of the test voltage generating facility is almost the same as the case where the withstand voltage test is performed on one unit power cable 2B (length of several kilometers). Therefore, the capacity of the test voltage generating facility can be remarkably reduced as compared with the case where the test voltage is applied to the entire conductor length of the long power cable.

  FIG. 3 shows still another embodiment of the present invention. In the test method of FIG. 1, since the curvature of the equipotential line is large and the interval is narrow near the end of the joint portion semiconductive layer 9 to which the test voltage is applied, the electric field tends to concentrate on that portion. When the test voltage is about 100 kV or less, the withstand voltage test can be performed even with the test method of FIG. However, when the test voltage increases to 100kV to 200kV, the electric field near the end of the joint outer semiconductive layer 9 becomes stronger in the test method of FIG. Or discharge occurs, making it difficult to conduct a withstand voltage test using partial discharge measurement.

  Therefore, in the embodiment of FIG. 3, the stress relief cone 12 composed of the semiconductive portion 12a and the insulating portion 12b is provided from the outer periphery of the end portion of the joint outer semiconductive layer 9 to the outer periphery of the insulator 4 of the unit power cables 2A and 2B. In addition, a withstand voltage test is performed. The semiconductive portion 12a is formed by semiconductive tape winding, and the insulating portion 12b is formed by insulating tape winding. The semiconductive portion 12 a is formed so that a part thereof is located on the outer periphery of the end portion of the joint portion external semiconductive layer 9, and the interface between the semiconductive portion 12 a and the insulating portion 12 b extends from the end portion of the joint portion external semiconductive layer 9. It is formed in a tapered shape (trumpet shape) in which the inner diameter gradually increases as the distance increases. In this way, the equipotential line passing through the edge cut portion is gently bent and the electric field at the edge cut portion is relaxed, so that a withstand voltage test is performed without causing dielectric breakdown even when the test voltage is 100 kV to 200 kV. be able to.

  FIG. 4 shows still another embodiment of the present invention. When the stress relief cone 12 is formed by tape winding as in the embodiment of FIG. 3, when the test voltage is further increased, partial discharge is likely to occur from the triangular void portion caused by tape winding, and the partial discharge measurement is used in combination. It becomes difficult to perform a withstand voltage test normally.

  Therefore, in the embodiment of FIG. 4, the stress relief cone 12 is constituted by a rubber molded body in which the semiconductive portion 12a and the insulating portion 12b are integrally formed. Silicone rubber or ethylene propylene rubber may be used as the rubber material. Since this stress relief cone 12 is a unitary body, before the unit power cables 2A and 2B are joined, they are sheathed on the cable in a state of expanding the diameter against the rubber elasticity and after the factory joint portion 1 is formed. Then, it is pulled back to the position shown in the drawing and reduced in diameter by rubber elasticity to be mounted at a predetermined position. If such a stress relief cone 12 is used, a withstand voltage test can be performed even at a test voltage of 200 kV or higher.

  In the case where the test voltage is further increased and there is a possibility that a flashover may occur at the edge cut portion even when the integrated stress relief cone 12 as shown in FIG. 4 is used, the same applies to the cable external semiconductive layer 5 side. A stress relief cone may be provided.

1: Factory joint part 2A, 2B: Unit power cable 3: Cable conductor 4: Cable insulator 5: Cable outer semiconductive layer 6: Metal shielding layer 7: Conductor connecting part 8: Reinforced insulator 9: Joint part outer semiconductive Layer 10: Temporary shielding layer 11: Test voltage generating facility 12: Stress relief cone 12a: Semiconductive portion 12b: Insulating portion

Claims (4)

  A withstand voltage test method for factory joints of long power cables obtained by joining and lengthening the required number of unit power cables of a length that can be manufactured in a continuous manner at the factory joint part to be tested On the outer periphery of the reinforced insulation, a joint external semiconductive layer electrically cut from the external semiconductive layer of at least one unit power cable on both sides of the factory joint is provided, and a temporary shielding layer is provided on the outer periphery. And withstanding the conductor of the long power cable, a withstand voltage test of the factory joint part is performed by applying a test voltage to the temporary shielding layer. Voltage test method.   A stress relief cone consisting of a semiconductive part and an insulating part is provided from the outer periphery of the end of the semiconductive layer of the joint part to the outer periphery of the insulator of the unit power cable, and a withstand voltage test is performed with the electric field at the edge cut part relaxed. The withstand voltage test method for a factory joint part of a long power cable according to claim 1.   3. The withstand voltage test method for a factory joint portion of a long power cable according to claim 2, wherein the semiconductive portion of the stress relief cone is formed by semiconductive tape winding, and the insulating portion is formed by insulating tape winding.   3. The withstand voltage test method for a factory joint portion of a long power cable according to claim 2, wherein the stress relief cone is made of a rubber molded body in which a semiconductive portion and an insulating portion are integrally formed.

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