This standard specifies the terminology, use conditions, structural requirements, technical requirements and test methods of air-insulated bus trunk systems (air-insulated bus ducts) (hereinafter referred to as bus ducts). This standard applies to bus ducts with rated voltages up to 660V AC, frequencies of 50HZ or 60HZ, and rated currents up to 5000A. This standard does not apply to self-contained components selected in bus duct systems, such as relays, which should comply with their own technical standards. JB/T 8511-1996 Air-insulated bus trunk systems (air-insulated bus ducts) JB/T8511-1996 Standard download decompression password: www.bzxz.net

Machinery Industry Standard of the People's Republic of China
JB/T 8511 - 1996
Air Insulated Bus Trunk System (Air Insulated Bus Duct1996-11-07 Issued
Ministry of Machinery Industry of the People's Republic of China
1997-07-01 Implementation
JB/T 8511 - 1996
This standard is prepared with reference to the national standard "Low Voltage Complete Switchgear and Control Equipment Part 1: Requirements for Type Test and Partial Type Test Complete Equipment"; National Standard "Low Voltage Complete Switchgear and Control Equipment Part 2: Special Requirements for Bus Trunk System (Bus Duct)". The preparation of the standard takes into account the actual requirements of users and ensures coordination with relevant standards, so that the preparation of this standard meets advanced and reasonable requirements.
Taking into account the current national requirements for the safety of electrical products, this standard is specifically The safety requirements for bus ducts are clearly stated in the clause. Appendix A and Appendix B of this standard are both appendices to the standard. This standard was proposed and managed by the Tianjin Electric Drive Design Institute of the Ministry of Machinery Industry. The drafting unit of this standard: Beijing Electric Factory. The main drafters of this standard are Liu Maolan
Wu Zhongjie
Yang Zhanyuan Hou Fulin
This standard was first issued in 1996.
Machinery Industry Standard of the People's Republic of China
Air Insulated Bus Trunk System (Air Insulated Bus Duct) 1 Scope
JB/T 8511 - 1996
This standard specifies the terminology, use conditions, structural requirements, technical requirements and test methods of air-insulated busbar trunking system (air-insulated busbar) (hereinafter referred to as busbar).
This standard is applicable to busbars with rated voltage AC up to 660V. Frequency 50Hz or 60Hz, rated current up to 5000A. This standard does not apply to self-contained components selected in the busbar system, such as circuit breakers, etc., which should comply with their own technical standards.
2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. At the time of publication of the standard, the versions shown are valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB2681--81
GB/T 2900.1—92
GB/T2900.5--83
GB/T 2900.18--92
GB/T4208-1993
GB5585.1~5585.3—85
GB9466—88
JB3084—82
National Standard
National Standard
3 Terms and Model Codes
3.1 Terms
Special Terms and Definitions of This Standard.
3.1.1 Air Insulated Busway
Clean Wire Color of Electrical Complete Set
Electrical Terminology Basic Name Terms
Electrical Technical terms Electrical insulation materials
Electrical terms Low-voltage electrical appliances
Classification of enclosure protection levels
Electrical copper, aluminum and alloy busbars
Basic test methods for low-voltage complete switchgear Product packaging and transportation regulations for power transmission control stations Low-voltage complete switchgear and controlgear Part 1: Requirements for type test and partial type test complete equipment
Low-voltage complete switchgear and controlgear Part 2: Special requirements for busbar trunk systems (busbar ducts)
Busbar ducts that support bare busbars with insulating pads in the shell and are insulated by air dielectric. 3.1.2 Feeder busbars
Feeder busbars are composed of various busbar trunk units without tapping devices (no plug-in holes), which are used to transmit electrical energy directly from the power supply to the distribution center.
3.1.3 Tap-off device
In order to connect the tap-off unit to the busbar trunk, the device installed on the busbar or the structural measures taken, 3.1.4 Plug-in bus duct
Plug-in bus duct consists of a busbar trunk unit with a tap-off device and a plug-in distribution box (feeder box), which is used to transmit electric energy. It can be approved by the Ministry of Machinery Industry on November 7, 1996
Implementation on July 1, 1997
Bow out the power branch.
3.1.5 Phase-changing unit for each line
JB/T8511 -1996
A busbar trunk unit that changes the relative position of the phase conductors to balance the reactance of each phase or change the arrangement position of each phase. 3.1. End cover
A device that terminates and closes the terminal of the bus duct. 3.1.7 Transverse partition
A partition or other protective device that prevents the free flow of air or moisture in the bus duct. 3.1.8 Indoor bus duct
Applicable to bus ducts installed in buildings that protect the bus duct from the sun. 3.1.9 Outdoor bus duct
Applicable to bus ducts that work outdoors and are not affected by weather. 3.1.10 Straight bus trunk unit (straight segment) Bus trunk unit with a straight line shape.
3.1.11 L-shaped bus trunk unit (L-shaped joint) Bus trunk unit with a right-angle bend shape. 3.1.12 T-shaped bus line unit (T-shaped joint) Line trunk unit with a T shape that can be connected to other bus line units in three directions. 3.1.13 X-shaped (cross-shaped) busbar line unit (X-shaped joint) is a cross-shaped busbar line unit that can be connected to other busbar line units in four directions. 3.1.14 Z-shaped busbar line unit (Z-shaped joint) is a busbar line unit that can be displaced parallel to the B shape on the busbar line. Except for 3.1, this standard uses the terms and terms related to this standard in GB/T2900.1, GB/T2900.5, GB/T2900.18, the national standard "Low-voltage complete switchgear and control equipment part 1", and the national standard "Low-voltage complete switchgear and control equipment part 2".
3.2 Model code
To be determined. bZxz.net
4 Technical requirements
4.1 Environmental conditions for use
4.1.1 Normal working conditions
4.1.1.1 Ambient air temperature
The ambient air temperature shall not exceed +40℃, and its average temperature shall not exceed +35℃ within 24h. The lower limit of ambient air temperature is -5℃.
4.1.1.2 Atmospheric conditions
The air is clean, and its relative humidity does not exceed 50% when the maximum temperature is +40℃. Higher relative humidity is allowed at lower temperatures, such as 90% at +20℃, but attention should be paid to occasional moderate condensation due to changes in condensation. 4.1.1.3 Altitude
The altitude of the installation site shall not exceed 2000m. 4.1.1.4 Pollution level
The pollution level shall be selected as level 3 according to the provisions of the national standard "Low-voltage complete switchgear and control equipment part 1". 4.1.2 Special working conditions
When any of the following special conditions exist, they must be specified in the specific product standards or resolved by negotiation between the user and the manufacturer. 4.1.2.1 The temperature, humidity and altitude specified in 4.1.1 are not interchangeable. 2
JB/T 8511 - 1996
4.1.2.2 During use, the temperature or atmospheric pressure changes rapidly, and abnormal condensation occurs in the device. 4.1.2.3 The air is seriously polluted by dust, smoke, corrosive particles, radioactive particles, steam or salt mist. 4.1.2.4 Exposure to strong electric and magnetic fields: Exposure to high temperatures, such as direct sunlight or baking in a furnace. 4.1.2.5
Affected by mold or microorganisms.
Installed in a location with fire or explosion hazard. Subjected to strong vibration and shock.
4.1.2.9 Install in places where the current carrying capacity and breaking capacity will be affected, such as installing the equipment in a machine or embedding it in a wall. 4.1.2.10 Take appropriate measures to solve the interference of electrical and optical radiation. 4.2 Installation conditions
4.2.1 Overvoltage category (installation category)
The overvoltage category complies with the national standard "Part 1 of low-voltage complete switchgear and control equipment" and can be classified as II, II and IV. The manufacturer should provide it in the instruction manual. 4.2.2 Installation method
The installation should be carried out according to the manufacturer's installation instructions. 4.3 Rated parameters
4.3.1 Rated current
The rated current value of the bus duct shall be one of the standard values ​​in Table 1. Table 1 Rated current value (RMS value)
63, 100, 125, 160, 200, 250, 315, 400, 500, 630800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 50004.3.2 Rated working voltage
The rated working voltage of the bus duct shall be AC ​​380V, 660V. 4.3.3 Rated insulation voltage
The rated insulation voltage of the bus duct is the voltage value related to the dielectric strength test, electrical clearance and creepage distance. Unless otherwise specified, the rated working voltage of the circuit is not allowed to exceed the rated insulation voltage. 4.3.4 Rated frequency
The rated frequency is 50Hz or 60Hz.
4.3.5 Rated short-time withstand current
The rated short-time withstand current of the bus duct refers to the current (RMS value) that the bus duct circuit can withstand in 1s under the specified test conditions. The values ​​are shown in Table 2.
Table 2 Rated short-time withstand current values ​​(RMS values) 4, 4.5, 5, 6.3 (7), 10 (15), 20, 25, 30, 35, 40, 45, 50 (55), 63 (60), 80, 90 Note: The numbers in brackets should be avoided as much as possible. 4.3.6 Rated peak withstand current
The rated peak withstand current of the bus duct refers to the current peak value that the bus duct can withstand under the specified test conditions. The value is the product of the short-time withstand current (RMS value) in Table 6 and the coefficient n. 4.4 Structural requirements
4.4.1 General
Air-insulated bus ducts shall be designed as type-tested low-voltage complete switchgear and controlgear (TTA). 3
JB/T8511-1996
Bus ducts are divided into plug-in air-insulated bus ducts and feeder air-insulated bus ducts and various bus duct units. The structure of the bus duct must be safe and reliable, easy to operate and maintain. At the same time, it should be made of materials that can withstand the mechanical, electrical and thermal stresses specified in this standard. The materials should be appropriately surface treated or use appropriate anti-corrosion materials. 4.4.1.1 Mechanical load
The busbar shall meet the requirements of 7.1.1.1 to 7.1.1.3 in the national standard "Low-voltage Complete Switchgear and Controlgear Part 2". 4.4.1.2 Each line trunk unit
The bus duct trunk unit shall support and separate the bus with supports made of insulating materials and be installed in the shell. The distance between the supports shall ensure the strength requirements of the bus. Plug-in bus ducts can be provided with several sockets as required. 4.4.1.3 Bus duct connection
The bolts, nuts and washers used in the connection between bus duct units shall be made of steel or copper alloy products with electroplating layer with sufficient strength. Plug-in junction box (feeder box)
Plug-in junction box (feeder box) is divided into the following types according to its use: a) Junction box directly connected to the cable and no other electrical components are installed; b) Junction box with circuit breaker installed inside,
c) Junction box with knife switch installed inside;
d) Junction box without opening and closing components inside, only with fuse, button or other electrical components and measuring meter installed. The structure of the plug-in junction box must meet the following requirements: a) When the connector of the junction box is inserted into the busbar trunk unit, the mechanical connection with the busbar duct should be firm, the electrical contact should be good, and no live parts should be exposed. In addition, its structure should make it easy to insert and remove, and ensure that it can still work normally after 50 insertions and removals; b) The operating mechanism in the junction box should be flexible and reliable; c) The various electrical components selected for the junction box should comply with its own product standards; d) The installation of all parts in the junction box should be firm and reliable; e) The structure of the junction box should ensure that the relays and electrical components are easy to install and maintain; ) The junction box should have a warning mark or warning that plugging and unplugging under load is not allowed. 4.4.2 Materials
4.4.2.1 Shell
The selection of busbar shell materials can meet the requirements of 4.4.1.1 of this standard. The interconnected parts of the shell can be welded or bolted, but the electrical continuity of the shell connected by bolts should be guaranteed: all fasteners used on the shell should have a good anti-corrosion coating, and the shell surface should be covered with a flame-retardant, non-glare and reflective coating. The coating color should be uniform, neat and beautiful, and there should be no defects such as blistering, cracks and flow marks.
4.4.2.2 Conductor
a) The conductor should be made of copper, aluminum and its alloy materials with sufficient mechanical strength and current carrying capacity: b) The conductor must be made of materials that meet the requirements of GB5585.1~5585.3. 4.4.2.3 Insulating materials
a) Conductor supports must be made of flame-retardant and moisture-resistant insulating materials, and should have sufficient mechanical properties; b) Insulating materials must have heat resistance not lower than that required by 4.5.1 of this standard; Insulating materials should have sufficient insulation performance, and the insulation should have a certain safety factor; d) Insulating materials should be made of materials with sufficient aging resistance. 4.4.3 Terminals for shell conductors
The terminals for external conductors of bus ducts shall comply with the requirements of 7.1.3 of the national standard "Low-voltage complete switchgear and control equipment Part 1". 4.4.4 Electrical clearance and creepage distance
The electrical clearance and creepage distance between exposed live conductors of different polarities in the bus duct and between them and the shell shall not be less than the provisions of Table 3. Otherwise, an impulse withstand voltage test should be carried out for verification. 4
Rated insulation voltage
60U300
300U690
4.4.5 Shell protection grade
JB/T 8511 - 1996
Electrical distance
Table 3 Electrical clearance,
Electrical clearance
The protection grade of bus duct shell shall not be lower than the IP30 requirement specified in GB/T4208. A4.6 Color and arrangement of bus duct conductors
Ship electrical distance
Bus duct shall have obvious conductor phase sequence markings. The phase sequence arrangement of conductors shall comply with the provisions of Table 4, and the color of conductors shall comply with the requirements of GB2681. The color of the protective conductor in the bus duct must be yellow-green double color. When the protective conductor is an insulated single-core wire, this color shall also be used. And through the entire length of the conductor, yellow-green double color is not allowed to be used for any other purpose except as the identification color of the protective conductor. The terminal of the external protective conductor shall be marked with a grounding symbol.
Table 4 Busbar Phase Sequence Arrangement
1 phase (phase A)
2 phase (B)
3 phase (phase C)
Neutral line N
Neutral protection line PEN
Protection line PE
Vertical arrangement
Horizontal arrangement
Note: In special cases, if this phase sequence arrangement will cause difficulty in busbar matching, it is not necessary to follow the provisions of Table 4. 4.5 Performance requirements
4.5.1 Temperature rise
Front and rear arrangement
The busbar is tested according to 5.1.2.2, and the temperature rise of each part should not exceed the provisions of Table 5. In special cases, if the insulation performance and service life of the insulating material are not affected, the temperature rise value can be appropriately increased. Table 5 Temperature rise value
Bus duct part
Terminals for connecting external insulated wires
Plug-in contacts on the bus and fixed connections with the bus Copper tinned Copper tinned (or the pin surface is specially treated) Aluminum tinned - aluminum tinned
Copper silver plated - copper silver plated
Aluminum tinned - copper tinned
Copper - copper
Contactable shell and cover
Metal surface
Insulating material surface
Note: 1) Unless otherwise specified, for the shell surface of the busbar that is accessible but not required to be touched during normal operation, the temperature rise can be increased, the metal surface can be increased by 25K, and the insulating surface can be increased by 15K. 5
4.5.2 Protection against electric shock
4.5.2.1 Protection against direct electric shock
JB/T 8511 - 1996
The protection requirements for direct electric shock of busbars shall comply with the provisions of the national standard "Low-voltage complete switchgear and control equipment".
4.5.2.2 Protection against indirect contact
The protection requirements for indirect contact shall comply with the provisions of the national standard "Low-voltage complete switchgear and control equipment".
4.5.2.3 Grounding terminal
7.4.2
7.4.3 in Part 1
The busbar trunk unit shall have a grounding terminal and a firm grounding mark. The grounding terminal shall be made of a material with good conductivity and shall have anti-corrosion measures and shall be installed in an easily accessible place. The connection resistance between any unpainted point on the busbar unit housing and the grounding terminal must be low enough to ensure the safe operation of the busbar trunk system, and its resistance value should be stated in the relevant technical documents. 4.5.3 Short-circuit strength (short-circuit current carrying capacity) Within the rated parameter range, the bus duct shall be able to withstand the thermal stress and electromotive stress generated by the specified rated short-time withstand current and rated peak withstand current. The value of the short-time withstand current shall be specified in the product standard. The peak value of the rated short-time withstand current and the rated peak withstand current shall be obtained by multiplying the coefficient n by the root mean square value of the short-time withstand current. The standard value of the coefficient n and the corresponding power factor are shown in Table 6. Table 6 Standard value of coefficient n and corresponding power factor Short-time withstand current Icw root mean square value
5Icw10
10lcw20
20lcw50
4.5.4 Resistance, reactance and impedance
Peak factor
The specific values ​​of the resistance, reactance and impedance of the bus duct product shall be given in the manufacturer's instructions or other documents. It shall comply with the requirements of 4.10 in the national standard "Low-voltage complete switchgear and control equipment part 2". .5.5 Insulation resistance
When tested according to 5.1.2.6, the insulation resistance of the bus duct at the nominal voltage shall not be less than 10002/V. The insulation resistance of each bus duct unit shall be given in the product standard. 4.5.6 Dielectric strength
Under normal use conditions, the bus duct between each phase bus and between live parts and dead parts shall be able to withstand the test voltage given in Table 7 for 1 min.
Table? Withstand test voltage
Rated insulation voltage Ui
300690
Test voltage (RMS value)
5 Test method
5.1 Type test
5.1.1 Type test items
Type test items include the following:
Mechanical load test (see 5.1.2.1);
Temperature rise test (see 5.1.2.2);
JB/T 8511 - 1996
Protection circuit continuity test (see 5.1.2.3); d)
Short-circuit strength test (see 5.1.2.4);
Verify resistance, reactance and impedance (see 5.1.2.5); Verify insulation resistance (see 5.1.2.6);
Dielectric strength test (see 5.1.2.7);
Verify electrical clearance and creepage distance (see 5.1.2.8); h)
Verify the mechanical operation of the bus duct and the junction box plug-in (see 5.1.2.9); 1)
Verify the degree of protection of the enclosure (see 5.1.2.10). j)
5.1.2 Type test method
5.1.2.1 Mechanical load test
In addition to the tests in accordance with 8.2.10.1 to 8.2.10.3 of the national standard "Low-voltage complete switchgear and control equipment part 2", the bus duct that needs to be installed vertically must also be subjected to a vertical load test. During the test, a straight busbar trunk unit is vertically suspended, and the hanging point should be fixed on the busbar shell. A weight equivalent to 5 times the mass of the busbar conductor is hung on each conductor for a duration of 2 minutes, as shown in Figure 1. The test results must meet the following requirements:
a) During and after the test, there should be no cracks at the connection points or other parts of the busbar trunk unit, and the deformation of the ear shell does not damage the protection level or the electrical clearance and creepage distance are not reduced to less than the specified values ​​in Table 3 of this standard. There should be no obvious permanent deformation after the test, for example; there is a tendency to affect the correct insertion of the incoming and outgoing line units. b) The protection circuit should maintain its function during and after the test: c) After each test in accordance with 8.2.10.1 to 8.2.10.3 of the national standard "Low-voltage complete switchgear and control equipment Part 2", a dielectric test should be carried out in accordance with 8.2.2 of the national standard "Low-voltage complete switchgear and control equipment Part 1". When testing in accordance with 8.2.10.18.2.10.3 of the national standard "Low-voltage complete switchgear and control equipment Part 2", the support point spacing D and D1 values ​​are determined by the manufacturer.
W=5 times the conductor's deadweight
5.1.2.2 Temperature rise test
a) Bus duct layout
JB/T 8511-1996
When the bus duct is tested, it should be arranged according to normal use, and all covering plates, etc. should be in place. The rated current of the bus duct will be affected by the installation layout. Therefore, the temperature rise test must be carried out with the rated current suitable for the installation layout given by the manufacturer. If only one test is performed, the most unsuitable installation configuration should be used. b) Temperature rise test
The test should be carried out on a bus duct with a total length of at least 6m and including at least one connection point. The test current should be roughly equal in the live conductor. The tested components should be prevented from any unintentional air flow and the ends should be closed. In addition, the temperature rise test should be carried out on the tapping units connected to different sections of each line trunk system. For this test, the tapping unit shall be passed with rated current, and the busbar trunk system shall be loaded with rated current. The size and arrangement of the external conductors used in the test shall be included in the test report. The requirements are shown in Appendix A. The test shall be carried out for a sufficient time for the temperature rise to reach a constant value (but not more than 8 hours). In fact, this condition is met when the change does not exceed 1K per hour. Note: In fact, in the first stage of the test, the test time can be shortened and the current can be increased, and then reduced to the specified test current. In the absence of detailed description of the use conditions, the cross-section of the external conductor is shown in Appendix A. The temperature shall be measured by thermocouples during the test, and the ambient temperature shall be 10-40℃. After the test, the measured temperature rise does not exceed the requirements of Table 5 of this standard, the insulation in the bus duct is not damaged, and it can work normally, which means that the temperature rise test is considered to be qualified.
5.1.2.3 Protection circuit continuity test
5.1,2.3.1 Verification of effective connection between protection circuits It shall be verified whether the different bare conductive parts of the bus duct meet the requirements of 4.5.2.3 of this standard. Whether its resistance value meets the requirements of the specific product standard.
5.1.2.3.2 Verify the short-circuit strength of the protection circuit A single-phase test power supply, one pole is connected to the incoming terminal of one phase, and the other pole is connected to the terminal of the incoming protective conductor. If the bus duct has a separate protective conductor, the nearest phase conductor should be used. A separate test should be carried out for each representative outgoing unit, that is, a short-circuit connection is made between the outgoing terminal of the corresponding phase of the unit and the relevant outgoing protective conductor with a bolt. Each outgoing unit in the test should be equipped with a protective device that allows the unit to pass the maximum peak current and It value. This test allows the use of protective devices outside the complete set of equipment. For this test, the frame of the complete set of equipment should be insulated from the ground. The test voltage should be equal to the single-phase value of the rated working voltage. All other conditions of this test should be similar to 5.1.2.4. 5.1.2.3.3 Test results
The test results should meet the requirements of item b in 4.5.2 of this standard. 5.1.2.4 Short-circuit strength test
5.1.2.4.1 Bus ducts with a rated short-circuit withstand current not exceeding 10kA are not required to undergo short-circuit withstand strength tests. 5.1.2.4.2 Test arrangement
The bus duct shall be arranged as in normal use. The type test shall be carried out on an installation that includes at least one busbar trunk feeder unit connected to an appropriate number of linear busbar line units with a total length not exceeding 6m. Other types of busbar line units and tapping units not included in the above test shall be tested separately. 5.1.2.4.3 Test results
a) After the test, the conductor shall not have any excessive deformation, as long as the electrical room and creepage distance still comply with the provisions of Table 3, and the deformation does not affect the proper connection with the tapping unit. Minor deformation of the busbar is allowed. At the same time, the insulation and insulation support parts of the conductor shall not show any obvious signs of damage. That is to say. The main characteristics of the insulation ensure that the mechanical properties and dielectric properties of the equipment meet the requirements of this standard. b) The detection device has no fault current indication; c) The parts used to connect the busbar should not be loose, and the conductor (busbar) should not be separated from the output terminal; 8
JB/T8511-1996
d) Ensure that the effectiveness of the protective conductor for protecting against electric shock is not weakened in the event of a fault; e) The deformation of the casing is allowed without compromising the protection level and the electrical clearance is not less than the specified value; It can withstand the tolerance test of Table 7 of 4.5.6 according to the test method of 5.1.2.7 without maintenance; f)
name) The state of the electrical appliances combined in the busbar system must meet the requirements of the specific product standard. If the above conditions are met, the test is considered to be qualified. 5.1.2.5 Verification of resistance, reactance and impedance
The average value of resistance, reactance and impedance (see 4.5.4) should be determined on the test sample used for the temperature rise test, that is, it should include at least one contact.
Examples of calculations using measured values ​​are given in Appendix B. 5.1.2.6 Verify insulation resistance
The insulation resistance of the bus duct shall be measured in each unit under normal use conditions. The insulation resistance is measured between the phases of the bus duct and between the phase conductor and the grounding terminal. The insulation resistance value shall comply with the requirements of 4.5.5 of this standard.
The voltage level of the instrument for measuring insulation resistance shall not be less than 500V. 5.1.2.7 Dielectric strength test
This test verifies whether the insulation performance of each part of the bus duct meets the requirements of 4.5.6. The test voltage is applied between the phases of the bus duct and between the live conductor and the bus duct casing (grounding terminal). The voltage of the test power supply shall be a sine wave with a frequency between 45 and 62Hz. When the output end is short-circuited, the current shall not be less than 0.5A. During the test, the specific operation should be to first apply 30% to 50% of the test voltage data specified in Table 7 to the test position, then gradually increase to the specified test voltage value within 10 to 30 seconds, and maintain at this value for 1 minute, and finally perform a voltage reduction operation until the voltage is zero and then cut off the power supply. During the test, if there are electrical components in the distribution box that cannot withstand this voltage value, they should be removed before the test. If there is no breakdown flashover phenomenon during the test, it is considered that the dielectric strength test of the bus duct has passed. 5.1.2.8 Verification of electrical clearance and creepage distance When measuring the electrical clearance and creepage distance of the bus duct, the possible deformation of the trough shell and busbar should be taken into account, including any possible changes caused by short circuit and mechanical load. For bus trunk units with tapping devices, it is also necessary to measure the electrical clearance and creepage distance of the withdrawable components at different working positions. Special measuring tools or general measuring tools can be used for measurement. The measured results (sizes) should meet the requirements of 4.4.4. 5.1.2.9 Verify mechanical operation
This test is to verify whether the connection between the bus duct and the junction box meets the requirements of 4.4.1.4a of this standard. After 50 insertions and extractions (insertion and extraction count as one time). Check whether the plug-in parts are intact, flexible, and reliable. And conduct a temperature rise test, the temperature rise should meet the requirements of 4.5.1.
5.1.2.10 Verify the protection level
The protection level of each duct should be tested in accordance with the provisions of GB/T4208 and should meet the requirements of 4.4.5 of this standard. 5.2 Factory Inspection
5.2.1 Factory Inspection Items
The factory inspection items include the following:
a) General inspection (see 5.2.2.1);
b) Dielectric strength test (see 5.2.2.2) Inspection of protection circuit continuity (see 5.2.2.3);
Verification of insulation resistance (see 5.1.2.6).
5.2.2 Factory Inspection Methods
5.2.2.1 General Inspection
General inspection includes:
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