CN213843435U

CN213843435U - Movable +/-800 kV direct-current withstand voltage test platform

Info

Publication number: CN213843435U
Application number: CN202022719826.7U
Authority: CN
Inventors: 任劼帅; 孟毅; 李劲彬; 陈隽; 吴传奇; 夏天; 陈敏
Original assignee: Electric Power Research Institute of State Grid Hubei Electric Power Co Ltd
Current assignee: Electric Power Research Institute of State Grid Hubei Electric Power Co Ltd
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2021-07-30
Anticipated expiration: 2030-11-23

Abstract

The utility model provides a mobile +/-800 kV direct current withstand voltage test platform, which comprises a withstand voltage test part, a supporting structure part, a lifting arrangement part and a field transfer part; the voltage withstand test part comprises a direct-current high-voltage generator, a double-layer hard equalizing ring and an operation part; the supporting structure part comprises a test platform chassis, a standing foot arranged at the bottom of the test platform chassis, a lifting lug arranged on the platform chassis and a cushion block; the arrangement lifting part adopts a hydraulic power-assisted mechanism to realize the automatic lifting and collecting functions of the test platform and complete the conversion of the platform between a test state and a transportation state; the transportation and transfer part comprises wheels arranged below the chassis of the test platform, a steering platform connected with the wheels and a traction pull rod connected with the steering platform. The utility model discloses can pull by the tractor and turn in a flexible way in the converter station, and can carry out on-the-spot withstand voltage test to the highest 800 kV's in the converter valve room DC equipment under the no hoist and mount condition.

Description

Movable +/-800 kV direct-current withstand voltage test platform

Technical Field

The utility model relates to a direct current equipment withstand voltage test field specifically is a portable 800kV direct current withstand voltage test platform.

Background

A large number of +/-800 kV, +/-500 kV conventional direct current and +/-420 kV ultra/extra-high voltage flexible direct current converter stations and the like are built in China, and a large number of ultra/extra-high voltage converter station engineering is still planned and built currently. According to the standard Q/GDW 1168-2013 power transmission and transformation equipment state overhaul test procedure and the standard DL/T1831-2018 flexible direct current transmission converter station overhaul procedure, in a handover test and a converter station annual overhaul routine test in the converter station construction process, the requirements of a withstand voltage test are required for a direct current transformer, and the requirements of direct current reference voltage, leakage current measurement and the like are required for an alternating current-direct current lightning arrester. Therefore, the requirements for the ultra/extra-high voltage direct current field test are higher for a longer period of time.

At present, a direct current device field voltage withstand test of +/-800 kV is usually performed by using a bulk direct current high voltage generator (direct current high voltage generator for short) for pressurization, and a direct current voltage divider is used for voltage measurement in bulk. The bulk equipment is usually composed of 2-3 sections of straight high voltage generators and voltage dividers, and is additionally provided with two large-diameter hard equalizing rings, current-limiting resistors and other accessory equipment. The equipment needs a large amount of hoisting, assembling and carrying work on a test site, and in a converter station with a gradually-compact design, the defects of large occupied area, long construction time and difficult risk management and control are obviously revealed. In particular, in the equipment in the converter valve hall, since the crane using fuel oil as energy is prohibited from entering the valve hall, the direct current equipment voltage withstand equipment in the valve hall is difficult to complete, and a direct current transformer voltage withstand test is not performed according to the standard due to condition limitation during annual inspection of the converter station.

Compared with a bulk test platform, the self-contained test platform has the advantages of high field unfolding speed, high automation degree, small occupied area and high safety coefficient. At present, for alternating current transformation equipment such as ultra/extra-high voltage transformers and GIS (gas insulated switchgear), a self-contained test platform or a test vehicle which can be used for transformer stations and converter station sites (including valve hall interiors) exists, and the application effect in field tests is good. However, at present, no self-contained test platform for ultra/extra-high voltage direct current equipment exists.

The patent document with the bulletin number of CN204008982U (bulletin date 2014, 12, 10) discloses a positive and negative high-power direct-high voltage generator of building block type, and the utility model discloses a direct current high voltage generator group of multisection building block type is spliced to form a direct current equipment withstand voltage test platform that can be used on site at the converter station, but does not possess the automatic function of arranging, needs to hoist and mount on site and arrange.

The patent CN103600680B (11/2015 on the publication date) on an alternating-current withstand voltage vehicle-mounted test platform for 750kV ultrahigh-voltage equipment provides an automatic test vehicle formed by combining building block type withstand voltage test equipment and an automatic displacement device, and the test vehicle can be used for withstand voltage tests of 750kV or below alternating-current equipment. However, in the arrangement process of the building block type test equipment platform, a plurality of displacement devices such as a motor, hydraulic pressure, air pressure and the like are needed, a plurality of power sources are needed, and the design complexity of the equipment far exceeds that of equipment with a single hydraulic power source; the building block type test platform disclosed by the patent can be actually arranged or collected on site for 40 minutes, is shorter than the traditional bulk equipment, but is not suitable for the ultrahigh voltage converter station with numerous direct current equipment and needing frequent arrangement and collection.

Different from the building block type automatic arrangement test platform, a pressure-resistant test platform of a turning lifting type extra-high voltage alternating current device only needing a hydraulic mechanism is provided by a patent with a publication number of CN209231458U (publication date of 2019, 8 and 9) and a patent with a publication number of CN208980252U (publication date of 2019, 6 and 14), namely an extra-high voltage GIS (gas insulated switchgear) self-loading and unloading electric power test moving platform. The platform further improves the test efficiency on the premise that the pressure-resistant test is completed by automatic arrangement without hoisting. However, such platforms have the characteristic of longer length than the building blocks, and the steering mechanism used in the above patent is difficult to meet the requirement that the longer platform is steered to 90 degrees in a road with the width less than 4m in a transformer substation and a converter station, especially when entering a converter valve hall. In practice, there are even situations where the crane is required to assist in turning in a station.

In addition, at present, no integral, movable and hoisting-free voltage withstand test platform for +/-800 kV direct current equipment exists, and particularly equipment in a converter valve hall is available.

SUMMERY OF THE UTILITY MODEL

The above-mentioned not enough to prior art exists, the utility model provides a based on convertible lifting of hydraulic pressure mechanism, and have full angle steering platform, can be in pulling the nimble turn in the converter station by the tractor, and can carry out on-the-spot withstand voltage test's equipment to the highest 800 kV's in the converter valve room DC equipment under the no hoist and mount condition, can promote DC equipment field test efficiency effectively, reduce personnel's cooperation, solve in the past because of forbidding fuel test car or tractor entering valve room and be difficult to accomplish the experimental problem of equipment in the valve room, for the new-built DC engineering's of future a period handing-over test and the routine experiment of having built the DC engineering, diagnostic test provides better option.

A mobile +/-800 kV direct current withstand voltage test platform comprises a withstand voltage test part, a supporting structure part, a lifting arrangement part and a field transfer part;

the voltage withstand test part comprises a direct-current high-voltage generator, a double-layer hard equalizing ring and an operation part, wherein the double-layer hard equalizing ring and the direct-current high-voltage generator are integrally arranged, and the operation part is used for controlling the direct-current high-voltage generator to generate 0-800kV negative direct-current voltage which is used as a power supply for testing a direct-current transmission device with the highest +/-800 kV;

the supporting structure part comprises a test platform chassis, a stand foot arranged at the bottom of the test platform chassis, a lifting lug arranged on the platform chassis and a cushion block, wherein the stand foot is used for stabilizing the test platform chassis during field test and road transportation, the lifting lug is used for lifting the platform down or up to a flat car for transportation when the platform enters or leaves, the cushion block comprises a DC high-voltage generator cushion block, and the DC high-voltage generator cushion block is used for supporting a DC high-voltage generator in a vertical state;

the arrangement lifting part adopts a hydraulic power-assisted mechanism to realize the automatic lifting and collecting functions of the test platform and complete the conversion of the platform between a test state and a transportation state;

the transportation transfer part comprises wheels arranged below a chassis of the test platform, a steering platform connected with the wheels and a traction pull rod connected with the steering platform, the steering platform can freely turn for 180 degrees, and the traction pull rod is used for being connected with a traction vehicle.

Furthermore, the withstand voltage test part also comprises a current-limiting resistor, and the current-limiting resistor is detachably arranged at the center of the double-layer hard grading ring.

Furthermore, the arrangement lifting part comprises a hydraulic station, a lifting hydraulic cylinder, a bracket, a base, a hoop hydraulic cylinder and a hydraulic controller for operating the lifting hydraulic cylinder;

the hydraulic station is used for providing power for the lifting hydraulic cylinders and the hoop hydraulic cylinders, and the pair of lifting hydraulic cylinders are positioned on two sides of the bracket and used for lifting the bracket and the reactor to be vertical for testing and falling back after the testing;

the bracket is positioned at the lower part of the direct-current high-voltage generator and is directly connected with the lifting hydraulic cylinder, and the bracket is used for dispersing the stress of the direct-current high-voltage generator in the lifting and falling processes;

the base is used for supporting the direct-current high-voltage generator, and a limiting buckle is arranged on the base and used for fixing the direct-current high-voltage generator in a test state;

the chassis of the test platform is provided with a position and angle sensor which is used for detecting whether the direct current high voltage generator is lifted to be vertical or falls back to a lying position or not and judging the result to be used by the logic locking of the hydraulic cylinder;

the hoop and the hoop hydraulic cylinder are positioned at the top end of the bracket and used for fastening the direct-current high-voltage generator and the bracket together in the lifting and falling processes, and the opening and closing power of the hoop is provided by the hoop hydraulic cylinder.

Furthermore, the cushion block also comprises a bracket cushion block, and the bracket cushion block is used for supporting the bracket in the lying state.

Furthermore, the standing legs use a manual rocker or a hydraulic boosting type to operate the lifting of the chassis of the test platform.

Furthermore, the diameter of the double-layer hard grading ring is 300mm, and the requirement of no discharge under 800kV negative polarity direct current voltage is met.

Further, the direct current high voltage generator comprises a middle transformer positioned at the bottom and a single-section voltage multiplying cylinder positioned above the middle transformer.

The utility model discloses can carry out on-the-spot withstand voltage test to highest 800 kV's direct current equipment, the platform can lie down the transportation, can transport by oneself at the current conversion station scene, and possesses the hydraulic pressure mechanism that can independently expand and put up, can realize not having on-the-spot direct current withstand voltage test of hoist and mount, has reduced experimental labour cost and improvement personnel work efficiency effectively, improves the flexibility and the mobility of test work.

Drawings

FIG. 1 is a front view of the movable + -800kV DC withstand voltage test platform of the present invention in a transportation state;

FIG. 2 is a top view of the movable + -800kV DC withstand voltage test platform of the present invention in a transportation state;

FIG. 3 is a front view of the movable + -800kV DC withstand voltage test platform of the present invention in a test state;

FIG. 4 is a left side view of the movable + -800kV DC withstand voltage test platform of the present invention in a test state;

fig. 5 is a schematic structural view of the manipulating part of the present invention.

In the figure: the device comprises a direct current high-voltage generator 1, a double-layer hard equalizing ring 2, a current-limiting resistor 3, an operation part 4, an intermediate transformer 5, a pressure doubling cylinder 6, an equipment box 7, a platform chassis 8, a platform chassis 9, a standing foot 10, a lifting lug 11, a cushion block 12, a lifting hydraulic cylinder 13, a bracket 14, a base 14, a hoop 15, a hoop hydraulic cylinder 16, a wheel 17, a steering platform 18 and a traction pull rod 19.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

Referring to fig. 1-4, one embodiment of the mobile ± 800kV dc withstand voltage test platform of the present invention comprises a withstand voltage test part, a supporting structure part, a lifting part and a field transfer part.

1) Pressure test section

The withstand voltage test part comprises a direct current high voltage generator 1(800kV), a double-layer hard equalizing ring 2, a current limiting resistor 3 and an operation part 4, and is a main part for implementing a direct current withstand voltage test.

The direct current high voltage generator 1 comprises a middle transformer 5 at the bottom and a single-stage voltage doubling drum 6 above. Through the control of the control part 4, the intermediate transformer 5 can output a linearly variable voltage, and finally a negative polarity direct current voltage of 0-800kV is generated at the direct current high voltage generator 1, so that the direct current high voltage generator can be used as a power supply for testing a direct current transmission device with the maximum voltage of +/-800 kV. The dc test voltage is obtained by measuring the output voltage of the rectifying voltage-dividing circuit, and needs to be corrected when the device is shipped. The performance index of the dc high voltage generator 1 is shown in table 1:

TABLE 1 DC HIGH-VOLTAGE GENERATOR PERFORMANCE PARAMETERS

The double-layer hard equalizing ring 2 and the direct-current high-voltage generator 1 are designed integrally, and overall lifting arrangement is facilitated. The diameter of each equalizing ring 2 is 300mm, and the requirement of no discharge under 800kV negative polarity direct current voltage is met.

The current limiting resistor 3 is positioned at the center of the double-layer hard equalizing ring 2 and is designed to be detachable. The function is to limit the short-circuit current to protect the direct-current high-voltage generator 1 when the short-circuit breakdown fault occurs to the test sample. The device needs to be installed in the device test with high voltage level and large short-circuit capacity, and can be disassembled on the contrary.

The control part 4 is positioned in an equipment box 7 at the front end of the test platform, the specific structure of the control part 4 is shown in fig. 5, and the control part 4 comprises a hydraulic control part, a straight high-rise test control part and a test power supply part. The hydraulic control part comprises a hydraulic station 4-1 for various hydraulic mechanisms and a hydraulic power distribution control box 4-2 connected with the control part; the direct high-voltage power generation test control part comprises a direct high-voltage power generation control box 4-3 and has the functions of manual or automatic voltage boosting, charging current limiting, test data recording, information display, fault protection and the like; the test power supply part comprises a power distribution control panel 4-4 and a cable drum 4-5 for connecting and supplying a test power supply.

2) Supporting structure part

The supporting structure part comprises a test platform chassis 8 and a standing foot 9 arranged at the bottom of the test platform chassis 8. The chassis 8 is a main framework of the test platform and is used for mounting other three parts of equipment; the standing foot 9 is used for stabilizing the test platform chassis 8 during field test and road transportation, and the manual rocker is used for operating the lifting of the test platform chassis. The platform chassis 8 is provided with 4 lifting lugs 10 for lifting the platform down or up to a flat car for transportation when entering or leaving the station. There are 6 cushion blocks 11 on the platform chassis 8, wherein 4 cushion blocks 11 in the middle part are bracket cushion blocks for supporting bracket 13 in the state of lying down, and 2 cushion blocks 11 at the tail part are DC high voltage generator cushion blocks for supporting DC high voltage generator 1 in the vertical state.

3) Arranging lifting parts

The arrangement lifting part adopts a hydraulic power-assisted mechanism to realize the functions of automatic lifting, folding and the like of the test platform, the conversion of the platform between a test state and a transportation state is completed, and the consumed time can be controlled within 4 minutes. The part mainly comprises a hydraulic station, a lifting hydraulic cylinder 12, a bracket 13, a base 14, an anchor ear 15, an anchor ear hydraulic cylinder 16 and a hydraulic controller for operating the lifting hydraulic cylinder 12.

The hydraulic station is positioned in an equipment box 7 at the head of the test platform and used for providing power for a lifting hydraulic cylinder 12 and a hoop hydraulic cylinder 16;

the pair of lifting hydraulic cylinders 12 are positioned at two sides of the bracket 13 and used for lifting the bracket 13 and the reactor to be vertical for testing and falling back after the testing;

the bracket 13 is positioned at the lower part of the direct-current high-voltage generator 1 and is directly connected with the lifting hydraulic cylinder 12, and the bracket 13 is used for dispersing the stress of the direct-current high-voltage generator 1 in the lifting and falling processes;

the base 14 is used for supporting the direct current high voltage generator 1, and the base 14 is provided with a limiting buckle for fixing the direct current high voltage generator 1 in a test state. And a position and angle sensor is arranged on the test platform chassis 8 and used for detecting whether the direct current high-voltage generator 1 is lifted to be vertical or falls back to a lying position or not, and judging results are used for logically locking the hydraulic cylinder.

The hoop 15 and the hoop hydraulic cylinder 16 are positioned at the top end of the bracket 13 and used for fastening the direct current high-voltage generator 1 and the bracket 13 together in the lifting and falling processes, and the switching power of the hoop 15 is provided by the hoop hydraulic cylinder 16.

The following protection logic locking exists among the hoop hydraulic cylinder 16, the lifting hydraulic cylinder 12 and the limit buckle:

(1) for hoop hydraulic cylinder 16:

when the lifting hydraulic cylinder 12 acts or the direct current high-voltage generator 1 is in a lying state, the hoop hydraulic cylinder 16 cannot act;

when the direct-current high-voltage generator 1 is lifted to be vertical and the base 14 and the test platform chassis 8 are fastened through the limiting buckle, the hoop 15 can separate the bracket 13 from the direct-current high-voltage generator 1;

when the dc high voltage generator 1 is separated from the bracket 13, the hoop 15 needs to be kept separated, and the hoop hydraulic cylinder 16 cannot be actuated.

(2) For the lifting hydraulic cylinder 12:

when the direct current high voltage generator 1 is separated from the bracket 13, no action limitation exists;

when the direct current high-voltage generator 1 is combined with the bracket 13, the hoop 15 is required to be folded to tightly hold the direct current high-voltage generator 1, and the holding lifting hydraulic cylinder 12 can act;

when the dc high voltage generator 1 is lifted to be vertical, if the bracket 13 and the dc high voltage generator 1 need to be separated, the lifting hydraulic cylinder 12 can be operated only when the base 14 is fastened with the test platform chassis 8 and the anchor ear 15 is in a separated state.

4) Onsite transport section

The on-site transfer part comprises two groups of wheels 17 arranged below the test platform chassis 8, a steering platform 18 connected with the wheels 17 and a traction pull rod 19 connected with the steering platform 18. The wheels 17 are solid rubber wheels bearing 5 tons in total, and a traction pull rod 19 in front of the steering platform 18 can be pulled by a forklift, a trailer and the like, so that the platform is convenient to transport in a station.

The pull rod 9 can be turned up to the vertical in the test state to save space. When the towing vehicle is used for towing, the pull ring at the top of the towing pull rod 19 can be hung in the bolt at the tail of the towing vehicle, so that a 2-degree-of-freedom towing system is formed between the towing vehicle, the steering platform 18 and the test platform body. The steering platform 18 can freely turn at 180 degrees, so the system can enable the test platform to steer at the maximum steering angle of 180 degrees in a transformer substation or a converter station, is convenient to drive on a narrow road surface in the station under the condition of no hoisting assistance, can steer in situ and can enter a valve hall entrance at a three-way intersection. If the used vehicle is an electric forklift, the test platform can enter a converter valve hall under the condition of not using fuel power, and the requirement that fuel waste gas cannot be discharged in the valve hall is met.

Besides the 4 parts, the test platform is also attached with accessories such as a cable coil, a high-voltage expanded-diameter conductor, a power socket, an alarm lamp, a safety isolation belt and the like.

The external maximum dimensions of the test platform when transported in the field are: 7.6 meters long, 2.1 meters wide and 2.4 meters high, and the total weight is less than 4.5 tons.

The utility model discloses portable 800kV direct current withstand voltage test platform's application method, including test platform experimental arrangement in the current conversion station and test platform experimental collection two stages in the current conversion station.

The test platform is used in the test arrangement stage in the converter station as follows:

1.1) positioning and fixing of test platform

The test platform is pulled to the vicinity of the equipment to be tested by a forklift or a trailer in the convertor station, and the safety distance between the test platform and the equipment to be tested and other nearby equipment needs to be ensured; and then driving the traction vehicle away from the test area, and enabling the 6 standing feet 9 to be in close contact with the ground in a manual rocker mode and leveling the test platform.

1.2) lifting of the direct-current high-voltage generator 1

Connect the test platform power, start the hydraulic pressure station, operation hydraulic controller extends lifting hydraulic cylinder 12, lift bracket 13 perpendicular together with direct current high voltage generator 1, it is fixed with platform chassis 8 to close spacing buckle with the base 14 of direct current high voltage generator 1, operation hydraulic controller passes through staple bolt pneumatic cylinder 16 and parts staple bolt 15, lift pneumatic cylinder 12 through hydraulic controller shrink afterwards, fall bracket 13 back to the position of lying down, close the hydraulic pressure station at last. Before this step, if the load short-circuit current is large, the current-limiting resistor 3 needs to be installed.

1.3) test connection

And completing the wiring of a test loop including a test platform according to the relevant standard of the extra-high voltage withstand voltage test.

The use process of the test platform in the test acceptance stage of the converter station is as follows:

2.1) removing the connection

Removing all test connection wires;

2.2) dropping of the DC high-voltage generator 1

Starting the hydraulic station, operating the hydraulic controller to extend the lifting hydraulic cylinder 12, lifting the bracket 13 to be vertical, and then operating the hydraulic controller to close the hoop 15 through the hoop hydraulic cylinder 16; separating the limiting buckle to release the fixation between the base 14 of the direct-current high-voltage generator 1 and the platform chassis 8, contracting the lifting hydraulic cylinder 12 through the hydraulic controller, dropping the bracket 13 together with the direct-current high-voltage generator 1 to the lying position, and finally closing the hydraulic station;

2.3) test platform transfer

The 6 standing feet 9 are separated from the ground in a manual rocker mode, and the test platform is pulled out of the test area by using a traction vehicle.

In the whole arrangement and collection stage, only the hydraulic system needs to be operated, and hoisting by a crane is not needed.

Under the condition that the test is carried out without entering a converter valve hall, the supporting structure part and the on-site transferring part of the platform can be replaced by a self-powered flat car, namely the platform is transformed into a test car, so that the road transportation is facilitated, and the hoisting link when the platform enters a converter station can be reduced;

in further embodiments, the 6 standing feet 9 of the support structure portion can be replaced from a manual rocker mode of operation to a hydraulically assisted type, and also using the hydraulic station of the platform head as a power source;

in another embodiment, the double-layer rigid grading ring 2 can be replaced by a double-layer or single-layer inflatable grading ring, which can reduce the transportation length of the platform, but can increase the time for on-site arrangement and collection due to on-site loading, unloading and inflation.

The utility model discloses following beneficial effect has:

1. the utility model provides a set of hydraulic mechanism capable of lifting automatically on the test site of a converter station, which can complete the arrangement and the collecting and tidying work of the DC withstand voltage test of the highest 800kV without lifting by manually operating a hydraulic controller, and especially can test the equipment in a valve hall;

2. the protection logic lock exists between the hydraulic mechanism (namely the lifting hydraulic cylinder 12 and the hoop hydraulic cylinder 16) and the limit buckle, so that the equipment toppling possibly caused by misoperation in the arrangement and the collection process of the test platform can be avoided;

3. the utility model discloses combine together direct current high voltage generator 1's field test device and the dull and stereotyped transfer device that has the platform that turns to 18, make test platform can in the current conversion station with the valve room in convenient the turning to, arrange in a flexible way, simplified the establishment of direct current equipment test scheme, reduced the influence each other between this experiment and other operation faces, reduce test cost.

4. The device has the characteristics of convenience in road transportation and field transportation, rapidness in test development, small occupied area and low maintenance frequency, and reduces the time and personnel requirements for field test and maintenance.

The above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are all covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The utility model provides a portable 800kV direct current withstand voltage test platform which characterized in that: the device comprises a pressure test part, a supporting structure part, a layout lifting part and an on-site transferring part;

2. The mobile ± 800kV dc withstand voltage test platform of claim 1, wherein: the withstand voltage test part also comprises a current-limiting resistor, and the current-limiting resistor is detachably arranged at the center of the double-layer hard grading ring.

3. The mobile ± 800kV dc withstand voltage test platform of claim 1, wherein: the arrangement lifting part comprises a hydraulic station, a lifting hydraulic cylinder, a bracket, a base, a hoop hydraulic cylinder and a hydraulic controller for operating the lifting hydraulic cylinder;

4. The mobile ± 800kV dc withstand voltage test platform of claim 3, wherein: the cushion block further comprises a bracket cushion block, and the bracket cushion block is used for supporting the bracket in a lying state.

5. The mobile ± 800kV dc withstand voltage test platform of claim 1, wherein: the stand foot uses a manual rocker or a hydraulic boosting type to operate the lifting of the chassis of the test platform.

6. The mobile ± 800kV dc withstand voltage test platform of claim 1, wherein: the diameter of the double-layer hard grading ring is 300mm, and the requirement of no discharge under 800kV negative polarity direct current voltage is met.

7. The mobile ± 800kV dc withstand voltage test platform of claim 1, wherein: the direct-current high-voltage generator comprises a middle transformer positioned at the bottom and a single-section voltage-multiplying cylinder positioned above the middle transformer.