GB 3836.7-1987 Explosion-proof electrical equipment for explosive environments Sand-filled electrical equipment "q"
Some standard content:
1. National Standards of the People's Republic of China | Applicable to sand-filled electrical equipment. UDC621.3-78:622
.81
GB3836.7-87
1.2 In addition to complying with this standard, sand-filled electrical equipment must also Electrical equipment that complies with the relevant provisions of GB3836.1-83 "General Requirements for Explosion-Proof Electrical Equipment for Explosive Environments"
1.3 The rated voltage does not exceed 6kV and the moving parts do not directly contact the filler during use are allowed to be made. Sand-filled type. Chapter 1 Terminology, Technical Requirements
2 Terminology
2.1 Sand-filled electrical equipment q”
The shell is filled with sand material so that it can be used under specified conditions. , the arc generated in the shell, the propagating flame, the overheating of the shell wall or the surface of the sand material cannot ignite the electrical equipment of the surrounding explosive mixture. 2.2 Arc current (1.)
The average effective value of the continuous arc current caused by short circuit in the filler of sand-filled electrical equipment. 2.3 Short-circuit current (1ee)
The calculated value of the current flowing in the connection between the sand-filled electrical equipment and the power supply network under a complete short circuit. 2.4 Short circuit duration or arc duration (t) arc current I. The time elapsed from the onset of flow through an electrical device until it is completely extinguished. Note: ① The short-circuit arc current flowing at a given point of the power grid is usually not determined through experiments. According to the experience of some laboratories, when the voltage does not exceed 6kV, the calculated short-circuit current Ie and the actual arc current 1a have the following ratio: ~1.3
② When the electrical equipment is protected by a protective switch, time! It is equal to the entire disconnection time from the start of tripping of the protective switch to the complete disappearance of the current.
2.5 grid
A perforated metal sheet fixed within the casing and positioned within the filled sand to reduce the height of the filled sand material. 2.6 Minimum safe height (h.)
The shortest vertical distance between the free surface of the external explosive mixture and the nearest live part that the filling material, after being vibrated and compacted, can prevent the arc igniting the current and duration specified in the electrical equipment. distance. The minimum safe height of electrical equipment equipped with grids is the sum of the protective layer height hea and the reserve layer height d.
ho=hea+d
Approved by the National Bureau of Standards on 1987-06-18
Implemented on 1988-03-01
2.7 protective layer height (hea)||tt ||GB3836.7-87
The shortest distance between the live parts of the electrical equipment in the enclosure and the grid. 2.8 Reserve layer height (d)
The thickness of the filling material on the grid used to fill the occasional holes in the protective layer. 2.9 Density
The degree of compaction of sand material in the shell of sand-filled electrical equipment. 3. The outer casing of the external charging
must be made of metal materials. It can also be made of non-combustible or flame-retardant materials. However, their mechanical properties and long-term stability should be tested, and accurate instructions should be given to prevent them from being damaged. Replaced by other materials with different properties. 3.1 Mechanical strength
The shell must have sufficient mechanical strength and a certain safety factor so that it can withstand the impact and mechanical force imposed on the shell due to the characteristics and use of the installed electrical equipment. Regardless of the volume of the enclosure, it must withstand the hydrostatic test specified in Article 10.1 to check the minimum mechanical strength of the enclosure. 3.2 Protection level
The protection level of the shell must be no less than IP54. 3.3 Filling
When filling sandy materials in the shell, it must be subjected to forced vibration with a frequency of 25 ~ 50Hz and an amplitude of 1.0 ± 0.2mm Carry out for no less than 5 minutes, and try to fill all the gaps in the shell. In order to minimize the gaps that may appear on the top of the filling free surface during operation, one or more observation windows must be provided on the shell so that any gaps can be immediately detected. 3.4 Insulation of built-in electrical equipment
The windings in the enclosure should have sufficient insulation strength without considering the additional insulation effect of the filler. The heat-resistant classification of insulating materials must comply with the provisions of JB794-66 "Heat-resistant Classification of Insulating Materials for Motors, Electrical Appliances and Transformers". 3.5 Fasteners
Fasteners for Class I electrical equipment must comply with the requirements for special fasteners in Article 9.2 of GB3836.1. 4. Filling | ~1.25mm should account for more than 75%, and there should be no less than 0.25mm and no greater than 1.6mmb.
; the moisture content of
must not exceed 0.1% of its weight. 4.2 Other materials other than quartz
Other materials with properties not inferior to quartz are also allowed to be used. 5 Use of organic materials
No parts made of organic materials are allowed on the live parts inside the filler or between the live parts and the shell wall. 6 Introduction device
The cable entry device must comply with the protection level specified in Article 3.2. In addition, it must be able to withstand the stress generated by the allowable arc current 1. without damage.
7 Electrical distance
GB3836.7-87
7.1 Minimum distance between exposed live parts, between exposed live parts and internal grounded conductive parts, and between insulating components and shell walls The distance must comply with the requirements of column A in Table 1; the minimum distance between exposed live parts and the enclosure wall must comply with the requirements of column B of Table 1. Table 1 Electrical distance
rated voltage
V
U<300
300≤<700
700≤U<1500
1500 ≤U<3500
35006000
A
10
15
20
30
40||tt| |Minimum electrical distance, mm
B
15
20
30
A0
50
7.2 for rated For electrical equipment with a voltage not exceeding 500V, if it is made into a non-detachable closed structure (protection level not less than IP65), the distance between exposed live parts must be no less than 4mm, and the distance between exposed live parts and the shell must be no less than 5mm. 8 Minimum safety height (applicable to electrical equipment without grid) Minimum safety height h. It must be determined according to the test in Appendix A. However, when the voltage does not exceed 1500V, it must be no less than 30mm; when the voltage exceeds 1500v, it must be no less than 50mm.
9 Use of grid
In order to reduce the minimum safe height, it is allowed to place a grid for isolation in the fill. When using a metal enclosure, the grid must be conductively connected to the enclosure and manufactured in accordance with the following regulations. 9.1 Grid
The grid must be made of stainless or corrosion-resistant metal plates. The grid must have holes in the entire area, with a hole diameter of 8 to 10 mm, and a center distance of 50 to 70 mm between holes.
For electrical equipment with a volume less than 25L, the aperture of the grid may not be less than 5mm, and the center distance of each hole may not be less than 25mm. The thickness of the grid must be designed in accordance with the provisions of Article 9.2. Reinforcement ribs can be used when necessary, and the reinforcing ribs must be located on one side of the reserve layer. 9.2 Fasteners
The grid and fasteners must be able to withstand the load calculated by formula (1): P=0.25l.
Where: I.—arc current, A; || tt||Force
Static load of a grid, N.
Under the action of load P, the deformation of the grid must not be greater than 1.2mm. 9.3 Height of the protective layer
If the filler is made of quartz specified in Article 4.1, the height of the protective layer is calculated and determined by formula (2), but shall not be less than 20mm: hea0.31Vt
where: he.— Protective layer height, cm;
t—arc duration, s;
1.—arc current, A.
9.4 Reserve layer height
(1)
(2)
GB3836.7-87
The minimum height d of the reserve layer shall not be less than 0.2 times the height of the protective layer ha, and shall not be less than 10mm. 9.5 Requirements for grids at different usage locations of electrical equipment 9.5.1. Electrical equipment with only one use position. For electrical equipment with only one use position, the grid must be placed on top of the built-in electrical equipment. The thickness of the filler covering the upper part of the built-in electrical equipment must not be less than the minimum safe height. , the distance to the enclosure wall in other directions must comply with the requirements of Chapter 7. 9.5.2 For electrical equipment in any position of use
For electrical equipment in any position of use, the grid must completely surround the electrical equipment inside the enclosure, and the thickness of the filler coverage in any direction must not be less than the minimum safe height (see the figure below) . Come to you
Grid
Internal electrical equipment
Sand filling type schematic diagram
Second test
10 type test
In addition to the relevant provisions of Chapter 4 of GB3836.1, the type test of electrical equipment must also undergo the following supplementary tests. 10.1 Hydraulic pressure test
The shell must withstand a hydraulic pressure test of 5×10\Pa for at least 1 minute. The test results show that the shell should not leak or seep water, and no permanent deformation exceeding 0.5mm is allowed in any direction. 10.2 Determination of the minimum safe height of electrical equipment without grids The minimum safe height h of electrical equipment without grids. Determine according to the test method in Appendix A. However, if the minimum safe height has been determined in the past series of tests, this test is not allowed. 10.3 Determination of the protective layer height of electrical equipment with grids The height of the protective layer of electrical equipment with grids is measured according to the test method in Appendix A. However, if quartz is used as filler and the height of the protective layer meets the requirements of Article 9.3, this test is not allowed. 11 Factory test
The manufacturer must conduct factory test on each product. 11.1 Hydrostatic test
GB3836.7-87
The hydraulic test of the shell shall be carried out according to the requirements of Article 10.1. 11.2 Filler moisture content measurement
The moisture content of the filler must be measured before filling. The measurement method is not specified, and the measurement results must meet the requirements of Article 4.1. Note: Some of the following measurement methods can be considered equivalent to water content measurement: measuring dielectric strength, measuring resistivity, measuring capacitance, measuring loss angle, etc. Part III marks | |tt | ):
a. Maximum allowable arc current 1;
b. Arc duration t.
12.2 Instructions for use
Electrical equipment must be accompanied by instructions for use. The data on the nameplate should be repeated in the instructions and supplemented if necessary. For example, other related corresponding values ??or curves of arc current 1 and arc duration t. In the instructions, the operating procedures and precautions for replenishing the filler when a void occurs in the upper part during normal operation must be stated. In particular, the type and quality of the filler used should be explained. A.1 Gridless electrical equipment
GB3836.7-87
Appendix A
Determination of minimum safety height and protective layer height ( Supplement)
The test equipment for gridless electrical equipment is shown in Figure A1. Plastic film
Rubber belt
008
Spark plug
009
Packing discharge hole
Metal round bar
Test tank
e450
Mixture inlet valve
Mixture sampling valve
Gasket diagram
Pack level
Pneumatic vibrator
Mixture outlet valve
Telephone
Clamping assembly
Fast block
Picture A1 test equipment
Changing hair support
176|| tt | A mixture outlet valve for circulation. Connect the two electrodes with thin wires, then put the filler into the test tank, use the vibration of the vibrator (the vibration frequency, amplitude, and vibration time should be in accordance with Article 3.3) to enrich the filler and adjust it to the required height. Place a sealing gasket on the flange of the test tank, and then place a 300mm high metal cylinder to reliably connect it to the test tank. GB3836.7-87
The cylinder is equipped with a mixture inlet valve, a spark plug and a mixture sampling valve. The upper part of the round slip is covered with a plastic film and tied with a rubber band to form an integral seal between the test marrow and the round slip. Input the prepared explosive gas mixture into the test equipment. Use an optical interference gas analyzer to measure the concentration of the explosive gas mixture at the inlet, circulation outlet and sampling port. When the concentration reaches the requirements, close the valves at the inlet, circulation outlet and sampling port. Power is supplied to the electrodes through a time-adjustable protection circuit switch, which melts the thin wires between the electrodes to generate an arc, and cuts off the power supply at the end of the setting time. An oscilloscope can be used to record the arc short circuit process to obtain sufficiently accurate arc current 1. and arc duration values. If no ignition explosion occurs as a result of the test, a spark plug is used to detonate the upper explosive gas mixture after a few seconds to confirm that the test is effective.
If the arc does not ignite the upper explosive gas mixture, determine the height h of the mushroom-shaped lump formed in the filler. As a reference for determining the minimum safe height. At this time, part of the filling in the test tank must be released very carefully to avoid the mushroom-shaped hard lumps being broken due to the sliding of the filling.
Under the condition that the filling height h and the arc current 1. are kept at constant values, the longest arc current duration c that does not detonate in 10 tests is the limit of the arc current 1. under the specified filling height conditions. Allow duration t. Under the condition that the arc current 1. and the arc current duration t remain constant, the minimum filling height h that does not detonate after 10 tests is determined as the minimum non-detonation height h.
In the above two cases, the minimum safety height h must be determined according to formula (A1). . ho≥1.15h
where: h. —
minimum safe height, cm;
h minimum non-detonation height, cm.
In order to simplify the test, the starting test point can be determined by formula (A2). l·t-750h
Where: I. arc current, A;
t——arc duration, s;
h
-minimum filling height, cm.
(A1)
(A2)
Note: ①The power supply used must deliver as constant a current as possible throughout the arc duration. The arc current 1. is recorded on the oscilloscope average current.
② When testing with 8.5% methane and air mixture, the following results are obtained: h=10.0cm,
h=15.0cm,
h=20.0cm, ||tt ||Where:
In the formula: L—
L=760X10A*·S;
L=2500X10'A?.s
L=6500X10'A* ·s.
L-·t
- The ultimate impulse energy without detonation in the test, A\·s; - Arc current, A. The value range is 2000~6000A; la
—arc duration, s. The value range is 60×10-~120×10-s. The above test results can be used as a reference for design and verification. ③The nature of the gas has little impact on the minimum safe height. A.2 Electrical equipment with grid
Test equipment with grid electrical equipment must be equipped with a grid (as shown in Figure A2), but the use of reserve layers is not allowed. The grid must be fixed on the shell wall of the test tank with 6 evenly spaced fixing screws (Figure A3) so that the grid will not move during the test. Rubber belt
Plastic film
Grid
Packing discharge hole
GB3836.787
Metal round bar
Test||tt| |Figure A2
Fixing screws
Grid
Test equipment
Shell wall
Figure A3
Mixture import reading||tt| |Sealing Chu Waibzxz.net
Pneumatic vibrator
Mixture outlet valve
The test process is as described in A.1. When the upper explosive gas mixture does not detonate after 10 tests, and the arc is in the filler The height of the mushroom-like hard lumps produced inside GB 3836.7-87
shall not be greater than the height of the protective layer divided by 1.When 15 times, the protective layer height is considered to be sufficient. Note:
This standard was proposed by the National Technical Committee for Standardization of Explosion-proof Electrical Equipment. This standard was drafted by the Nanyang Explosion-proof Electrical Research Institute of the Ministry of Machinery Industry. The main drafter of this standard is Shi Fusheng, Ren Jiazhi, Ma Jinggang, Yang Yongzhu, and Li Xiaoquan entrusted the National Explosion-proof Electrical Equipment Standardization Technical Committee to be responsible for the interpretation of this standard.
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