JP3349275B2 - Elephant for cable head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct connection to enclosed electrical equipment.
Cable for conducting AC withstanding voltage test of
The present invention relates to a head elephant part.

[0002]

2. Description of the Related Art For a power cable, a withstand voltage test is performed on site after a new construction of a cable line, a system change construction, a trouble recovery construction, or the like. In addition, the insulation performance of power cables may deteriorate gradually during long-term use, leading to dielectric breakdown. In particular, CV cables, which have been frequently used recently, may not be used depending on the manufacturing conditions and usage environment. Insulation performance may deteriorate in a relatively short period of time due to water trees that may occur, causing dielectric breakdown.Therefore, in order to diagnose the dielectric strength of power cables, a withstand voltage test, corona test, leakage current test, etc. Various characteristic tests are performed. As a withstand voltage test of the power cable after the installation, a DC withstand voltage test has been conventionally performed. This is because if the distance of the cable line becomes longer, a large charging current flows in the AC withstanding voltage test, so that the power supply equipment such as a transformer becomes large, and the withstanding voltage test becomes difficult.

Recently, from the viewpoint of reducing the size of land at receiving substations and improving the reliability of power transmission and distribution, electric devices such as switchgears and transformers are housed in an equipment case together with an insulating medium such as gas or oil. Sealed electrical equipment has become widely adopted, but since the high-voltage part of these sealed electrical equipment is not exposed outside the equipment case, especially both ends are directly connected to the sealed electrical equipment. In the case of the power cable line, there is a problem that it takes a lot of trouble and time to perform the above-described DC withstand voltage test.

FIG. 2 shows a gas insulated switchgear (hereinafter referred to as GIS).
Shows the vicinity of the end portion of the directly coupled power cable) of the equipment case 1 accommodating the GIS body (not shown), Ri Contact <br/> comprise Elephant portion 2 cable head, the The bottom plate 3 of the elephant portion is provided with three gas terminal connection portions 4. A power cable 5 is connected to each of these gas-terminated terminal connections, and a connecting rod 6 connects between the extraction rod 4a of each gas-terminated terminal 4 and the high-pressure portion of the GIS. Further, the side surface of the cable head elephant portion 2 is closed by a case cover 7 and the inside of the device case 1 is filled with an insulating gas such as SF6 at a predetermined pressure.

When performing a DC withstand voltage test of a power cable directly connected to a sealed electric device having such a configuration, first, an insulating gas such as SF6 filled in the device case 1 is removed, and the case lid 7 is removed. Disconnect the gas terminal connection 4 and GIS
Remove the connecting rod 6 connecting the high pressure part of
As shown in FIG. 3, the extraction rod 4a of the terminal connection part 4 in gas
Attach a three-phase short-circuit metal fitting 8 between the tips of. It should be noted that removing the connecting rod 6 connecting the gas terminal connection portion 4 and the high pressure portion of the GIS may cause various inconveniences when a high DC voltage is applied to the high pressure portion of the GIS. So
To avoid it. Next, a withstand voltage adapter 10 is attached to the side surface of the cable head elephant portion 2 via a sleeve tube 9. A withstand voltage test terminating connector 11 is pre-installed in a lower power supply port of the withstand voltage adapter 10, and a slip-on structure power supply lead cable 12 is connected thereto. In addition, terminal connection part 1 for withstand voltage test
A resistor 14 is mounted between the drawer rod 13 and the three-phase short-circuit fitting 8, and the side wall of the withstand voltage adapter 10 is closed with a case lid 15. Then, after evacuating the inside of the equipment case 1,
An insulating gas such as SF6 is filled again. When the test preparation is completed as described above, a corona test, a leakage current test, and the like are performed as necessary, and a predetermined DC voltage is applied from the other end of the power supply lead cable 12 to screen the power cable 5. And confirm its soundness. After the above test is completed, remove the withstand voltage adapter and the like and attach the connecting rod 6 in the reverse order to the above order, fill the insulating gas such as SF6 again, and set the GIS to the operating state. Will be restored.

[0006]

As described above, when performing a DC withstand voltage test of a power cable line whose both ends are directly connected to a sealed electric device, mounting and dismounting of a withstand voltage adapter and connecting rods are required. There is a problem that it takes a lot of trouble and time for preparation work such as attachment / detachment or removal of the insulating gas such as SF6 or filling and filling of the insulating gas such as SF6, and for cleaning up. Moreover,
Particularly in recent substations where emphasis is placed on downsizing, the carrying-in passage, installation space and assembly space of the withstand voltage adapter are easily restricted, so the withstand voltage adapter is a three-phase package as described above. However, in the case of long-distance power cable lines, the withstand voltage test may not be able to be performed by three-phase batch application due to charging capacity, and diagnosis for each cable single-phase There is a disadvantage that it is not possible to perform.

As described above, the withstand voltage test of the power cable line whose both ends are directly connected to the sealed electric device has been conventionally performed exclusively by the DC method. Insufficient destructive energy may result in failure to detect power cable defects even at high applied voltages. For example,
In the case of a 66KV class CV cable, according to the results of a recent test conducted by the present inventors, a harmful tree is detected even when a voltage of about 152 KV, which is twice the electric equipment standard, is applied in the DC withstand voltage test. May not be enough to prevent accidents. On the other hand, in the case of the same CV cable, if a water tree having a length of 3 mm or more exists in the cable insulator,
The cable breaks at a working voltage of 38 KV, but
When KV is applied, if a water tree having a length of 2 mm or more is present, the cable will be destroyed. Therefore, screening the cable with such an AC voltage will surely prevent an accident during operation of the cable. Further, the AC withstanding voltage test is closer to the actual operating conditions than the DC withstanding voltage test, and effective test data can be obtained.

Accordingly, the present invention provides a cable head for performing a withstand voltage test of a power cable for efficiently and reliably screening a power cable directly connected to a sealed electric device.
It is an object of the present invention to provide an elephant part for a vehicle .

[0009]

SUMMARY OF THE INVENTION A cable head according to the present invention.
Elephant connection part is a device case of sealed electric equipment
And the bottom plate constituting a part of the equipment case,
From three phases close to each other at almost the same triangular position
A power cable in-gas termination connection,
Place the bushing mounting board, which constitutes a part,
Facing each other at the same triangular position,
Terminal connection for withstand voltage test mounted close to three phases
Wherein the gas-terminated terminal connection portion of the sealed electric device
Electrically connected to the main body high voltage section,
The connecting portions are each electrically connected to the opposite gas terminal connection.
Cable head elephant section,
The terminal connection for the pressure test is such that the leg is
Air tightly penetrated and the head is reinforced with the power lead cable side.
Bushing with tapered power entry to receive edge
And the power supply lead cable embedded in the bushing.
When the cable is installed, it is electrically connected to the cable conductor.
A shield fitting, one end of which is connected to the shield fitting
Is the tip of the bushing leg in the equipment case
An inner conductor exposed from the bushing and a power inlet of the bushing head
And a detachable insulating stopper for closing the insulating stopper.
Attach the power lead cable to the removed power port
In this way, a power application test using the AC voltage of the power cable was performed.
This is the elephant part for the cable head.

[0010]

According to the cable head elephant part of the present invention,
If the power cable under test is insulated and the insulation is degraded, the screening is performed by applying an AC voltage at a commercial frequency at a level that causes insulation breakdown, and the conditions are closer to the operating conditions than the DC withstand voltage test. Tests can be performed, and cables that may cause an accident during operation can be reliably detected and removed. The terminal connection for withstand voltage test to attach the power lead cable is very compact,
It does not occupy a large space unlike the conventional withstand voltage adapter. In addition, there is no need to perform operations such as attaching and detaching the withstand voltage adapter, attaching and detaching the connection rod and the like, and extracting and filling the insulating gas such as SF6, thereby greatly improving the workability.

[0011]

Next, an embodiment of a withstand voltage test method for a power cable according to the present invention will be described with reference to FIGS. 1, 4 and 5. FIG. In these figures, the same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals. FIG. 4 illustrates the vicinity of an elephant part for a cable head of a GIS to which a termination connection part for a withstand voltage test used when applying the method of the present invention is shown, and is an apparatus housing a GIS body (not shown). An elephant part 2 for a cable head is attached to the case 1, and a bottom plate 3 of the elephant part is provided.
Are provided with three end connection portions 4 in gas. The side and upper surfaces of the cable head elephant part 2 are airtightly closed by an elephant part case lid 7 and a bushing mounting board 20 which constitute a part of the equipment case.
The bushing mounting board 20 is provided with three bushings 21 formed by molding an insulating material such as epoxy resin, and their legs 21a are arranged so as to pass through the bushing mounting board 20, and are hermetically fixed. . Note that these bushings 21 are, as shown in FIG.
The bushing mounting board 20 is disposed close to the vertex position of an equilateral triangle on the same circumference from the center.

The bushing 21 has a shielding metal fitting 22 buried in a head 21b located outside the cable head elephant part 2, and an internal conductor 23 buried in a leg 21a. In this embodiment, the shielding fitting 22 and the inner conductor 23 are manufactured as an integral body formed by processing a metal material such as copper, and the lower end of the inner conductor 23 projects from the leg of the bushing 21 and is exposed. The head 21b of the bushing 21 has tapered power receiving ports 21b1 and 21b2 on both left and right sides for receiving a reinforcing insulator on the side of a power receiving lead cable described later. These power application ports are arranged so that their axes and the axis of the internal conductor 23 are substantially orthogonal to each other, and are closed by the insulating plug 24 during normal operation of the GIS.

The insulating plug 24 is formed by molding ethylene / propylene rubber or the like, and the power inlet 21 b of the bushing 21 is formed.
A pre-molded insulator 25 having a convex tapered surface corresponding to the concave tapered surface of 1, 1b2, and a high-voltage-side shielding electrode 26 and a low-voltage-side shielding electrode 27 fixed to the inner and outer ends thereof for alleviating an electric field. And a mounting plate 29 mounted on the outer surface of the low voltage side shielding electrode 27 via a spring 28. Pull-out rod 4 of each gas end connection 4
a, the lower end of the inner conductor 23, and the high-pressure portion (not shown) of the GIS main body are connected by connecting rods 6 for each phase, and the end terminal 4 in the gas is connected to the power supply. Cable 5 is connected. Further, in the device case 1 including the cable head elephant portion 2, SF
It is filled with an insulating gas such as 6. Among the three bushings 21 fixed to the bushing mounting board 20, the bushing connected to the central power supply lead cable has a longer leg portion 21a than the remaining two bushings, and a spacer. It is air-tightly fixed to the bushing mounting board 20 via 30.

In the GIS having such a configuration, a high voltage is supplied via a power cable 5 from a transformer or other power supply equipment (not shown) on the upstream side when the power system is normally operated. This high voltage is also applied to the shield metal fitting 22 at the termination connection part for the withstand voltage test. The high pressure side shielding electrode 26 and the low voltage side shielding electrode 2 are crimp-fitted to 21b1 and 21b2.
The dielectric strength of the interface between 7 is maintained.

Next, when performing the AC withstand voltage test of the power cable 5 connected to the GIS as described above, the power supply circuit applying the high voltage to the power cable 5 is cut off, and the bushing 21 of each phase is cut off. One of the insulation plugs 24 is removed from the power application ports 21b1 and 21b2, and instead, the distal end of the power application lead cable 12 is inserted and fixed as shown in FIG.

As the power application lead cable 12, a cable having a slip-on structure at its tip is used. That is, a reinforcing insulator 32 having a convex tapered surface corresponding to the power application ports 21b1 and 21b2 on the bushing 21 side is formed at the end of the cable insulating layer 31 of the power application lead cable 12.
And electrically connecting the semiconductive layer 33 at the outer end thereof to the shielding layer 34 of the power supply lead cable 12 and providing a support mechanism 36 having a spring 35 for applying a pressing force to the reinforcing insulator 32. It is mounted on the power application ports 21b1 and 21b2 on the bushing 21 side so that the convex tapered surface of the reinforcing insulator 32 is in close contact with the power application ports 21b1 and 21b2. In this case, a plug 38 is fixed via a wedge to the cable conductor 37 that is exposed by stepping off the distal end portion of the insulating layer of the power receiving lead cable 12. And a wedge is formed between the cable conductor 37 and the shield 22 when the reinforcing insulator 32 is mounted, and conduction is established via the plug 38 and the conductive contact.

As described above, the power supply lead cable 12
Is completed, the AC voltage of the commercial frequency is applied simultaneously from the other end to the three phases simultaneously or sequentially for each single phase. The applied voltage in this case is set to a level higher than the level at which insulation breakdown occurs when the power cable 5 to be tested has insulation deterioration. That is, for example, in the case of the above-mentioned 66 KV class CV cable, the length is 3 m in the cable insulator.
If there is a water tree of m or more, the cable will have a working voltage of 3
It is destroyed at 8 KV, but when applying 76 KV with AC, the cable is destroyed by the presence of a water tree with a length of 2 mm or more. The above AC voltage may be applied. If the power cable under test is destroyed by this screening, the cable has a high risk of causing an accident during operation, and is removed as ineligible and replaced with another power cable. When the connection work of the new power cable is completed, the AC withstanding voltage test is performed again in the same manner as described above, and if the test is successful, it is determined to be acceptable.

As described above, according to the present invention, an AC voltage is applied to a cable to test its withstand voltage. Therefore, the test environment is close to the actual use conditions of the cable, and a deteriorated cable is used. If present, it can be reliably detected and removed. In addition, since an AC voltage having a commercial frequency is used, there is no need to disconnect the cable under test from the sealed electrical device to which they are directly connected or to switch to three-phase batch connection, and the device is filled in the device case. There is no need to remove or refill the insulating gas. Also,
The sealed electrical equipment to which the cable under test is directly connected is GI
In the case of S, if it is not desired to apply a test voltage to the high voltage portion or the electric equipment connected to the high voltage portion, the test may be performed by opening the GIS. In addition, the termination connection for withstand voltage test used in the present invention is very compact, and its high-voltage portion is always closed with an insulating plug, so that it is safe, and Connection work is also easy.

In particular, in the case where a terminal connection portion for withstand voltage test is used in which the axis of the tapered power supply opening of the bushing and the axis of the internal conductor are arranged to be substantially orthogonal to each other. Since the power lead cable can be pulled out in the direction parallel to the bushing mounting board, the power lead cable does not need to be bent with a large curvature even in a narrow substation or the like, and the installation work is easy. Ma
And, when the two tapered voltage application port in Bed ashing uses the withstand voltage test terminating portion provided on symmetrical around the inner conductor, the person is not used for voltage application leads cable installation Another cable, for example, a power cable 5 for power supply, can be directly connected to the power application port. In this case, the gas end connection section 4 can be omitted.

Further, as described in claim 3, three for withstand voltage test sealing end, the bushing mounting substrate constituting a part of the device case of the closed type electric equipment, approximately equal triangle from the center A terminal connection for withstand voltage test connected to the centrally located power supply lead cable of the power supply lead cables mounted close to the position and arranged substantially in parallel passes through the bushing mounting board. If the bushing leg is longer than the bushing legs of the other two terminal connection parts for withstand voltage test and is attached to the bushing mounting board via a spacer arranged outside the equipment case, three withstand voltage Since the test terminating connection portions can be arranged in a staggered manner and the power application lead cables can be arranged in a three-ply stack, the mounting range of the withstanding voltage test terminating connection portion can be further reduced.

[0021]

According to the present invention, a power cable which may cause dielectric breakdown during actual use can be reliably detected and removed, so that the reliability of the power system can be improved. Also, as in the case of the DC withstanding voltage test, there is no need to disconnect the cable under test from the enclosed electrical equipment to which they are directly connected or switch to three-phase batch connection, and the cable is filled in the equipment case. There is no need to remove or refill the insulating gas that is present. Therefore, the power cable directly connected to the sealed electric device can be efficiently and reliably screened.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state in which a power application lead cable is attached to an end connection part for withstanding voltage test in a cable head elephant part of FIG.

FIG. 2 is a longitudinal sectional view showing the vicinity of a terminal end of a power cable directly connected to a conventional GIS.

FIG. 3 is a longitudinal sectional view showing a state in which a power application lead cable is attached to an end portion of the power cable of FIG. 2 via a withstand voltage adapter.

FIG. 4 is a vertical cross-sectional view illustrating the vicinity of an elephant portion for a cable head of a GIS to which a terminal connection portion for withstand voltage test used when applying the method of the present invention is attached.

FIG. 5 is a plan view showing the vicinity of a terminal connection part for withstand voltage test and a power receiving lead cable in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Equipment case 2 ... Elephant part for cable head 4 ... Terminal connection part in gas 5 ... Power cable 6 ... Connecting rod 8 ... Three-phase short-circuit fitting 10 ... Adapter for withstand voltage 11 ... Withstand voltage Terminating connection part for test 12 ... Lead cable 13 for applying power 13 ... Leader rod 14 ... Resistor 20 ... Substrate for bushing 21 ... Bushing 21 b1, 21 b2 ... Power port 22 ... Shielding metal 23 ... Internal conductor 24 insulating plug 25 pre-molded insulator 26 high-voltage side shield electrode 27 low-voltage side shield electrode 30 spacer 32 reinforcing insulator 37 cable conductor 38 plug

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 31/12 H02B 13/00-13/08 H02G 15/00-15/196

Claims (3)

(57) [Claims] 1. A device case for a sealed electric device and a bottom plate constituting a part of the device case, which are arranged from the center thereof.
Electric power installed in three-phase proximity at almost the same triangular position
A cable end connection part in gas and a bushing mounting board constituting a part of the equipment case
At the same triangular position from its center
Withstand voltage installed three-phase close to each connection
A terminal connection for test, wherein the terminal connection in gas is connected to the main body high pressure of the sealed electric device.
And the terminating connection for withstand voltage test is paired.
Cables respectively electrically connected to the gaseous terminal connection in
A bull head elephant part, wherein the leg part of the terminal connection part for the pressure resistance test has
Through the attached board in an airtight manner.
Bush with tapered power entry to receive reinforced insulation
And the charging lead case embedded in the bushing.
Electrically connected to the cable conductor when the cable is installed
And one end connected to the shielding fitting.
The other end of the bushing leg in the equipment case
An inner conductor exposed from the tip and a section of the bushing head;
A detachable insulating plug for closing the electrical outlet, and a power lead cable connected to the electrical outlet from which the insulating plug has been removed.
By attaching the power cable to the AC voltage of the power cable.
The elephant part for the cable head where the power application test is performed. 2. A voltage-testing termination connection portion, wherein an axis of a tapered power supply port of a bushing and an axis of an inner conductor are arranged so as to be substantially orthogonal to each other. Elephant part for cable head. Wherein the three withstand voltage test sealing end is the distal end portion of the voltage application leads cables are arranged substantially parallel are connected respectively, are connected to the voltage application lead cables located at the center One of the terminating connections for withstanding voltage test has a bushing leg extending through the bushing mounting board longer than the bushing legs of the other two withstanding voltage testing terminating connections. 3. The elephant part for a cable head according to claim 2 , wherein the elephant part is attached to the bushing attachment board via a spacer arranged in the bushing .