Article 4.5.6 1 The contact protection voltage shall meet one of the following requirements:
1) The steel bars interconnected between buildings and metal frames of buildings are natural downlead composed of at least 10 columns, and the columns of buildings as natural downlead include those around and in buildings.
2) The surface resistivity within 3m of the down conductor is not less than 50km? , or lay a 5cm thick asphalt layer or a 15cm thick gravel layer.
3) For the bare down conductor, the conductor below 2.7m from the ground shall be 1.2/50s? An insulating layer with a pulse voltage of 100kV, or a crosslinked polyethylene layer with a thickness of at least 3mm. 4) Use guardrails and warning signs to minimize the possibility of contacting the down lead. Paragraph 2 of Article 4.5.6, step-by-step voltage shall meet one of the following requirements:
1) The steel bars interconnected between buildings and metal frames of buildings are natural downlead composed of at least 10 columns, and the columns of buildings as natural downlead include those around and in buildings.
2) The surface resistivity within 3m of the down conductor is not less than 50km? , or lay a 5cm thick asphalt layer or a 15cm thick gravel layer.
3) Use the mesh grounding device to carry out potential equalization treatment on the ground.
4) Use guardrails and warning signs to minimize the possibility of entering the ground within 3m of down lead.
2. There are new regulations on down lead spacing. 18m (secondary level) and 25 m (tertiary level) are the spacing when the down lead is specially designed.
According to Article 5.3.8, when the second type lightning protection building or the third type lightning protection building is a steel structure or reinforced concrete building, the connection between steel members or steel bars shall meet the requirements of this specification and serve as a natural downlead (it is required to calculate the total surface area of connecting steel bars in each foundation according to the requirements of the specification: 0. The second type is 82m? Three kinds of 0.37 m? ), when its columns all play the role of down lead, it is not required to meet the specially designed down lead spacing.
3. Metal objects applicable to external lightning protection devices are defined as follows:
According to Article 5.4.5, when the grounding body buried in the soil is connected with the steel bar or steel used as the foundation grounding body in the concrete foundation, the grounding body in the soil shall be made of copper or copper-plated or stainless steel conductor.
If galvanized angle steel, flat steel, round steel or steel pipe is used, it can be encapsulated with cement mortar. The steel bars in contact with soil are protected by 1:2 cement mortar, and the protection thickness of cement mortar is ≥50mm, and the diameter is ≥ 100 mm ... See page 19 of 03d50 1-3 "Lightning Protection and Grounding Installation of Building Metal Bodies" for details. 4. The regulations for preventing side collision have been changed:
In the original specification, the division of anti-side attack was determined according to the radius of the ball, that is, anti-side attack measures should be taken for the level above 30m, the level above 45m and the level above 60 m.
According to the standards of the International Electric Power Working Committee, measures should be taken to prevent side attacks above 60m. Paragraph 7 of Article 4.2.4 of the new Chinese regulation GB 50057-2010+00 stipulates that, considering the importance of lightning-proof buildings, measures should be taken to prevent side lightning strikes over 30m; For the second-class lightning-proof buildings, according to Article 4.3. 1 of the new regulations, when the height of the building exceeds 45m, measures should be taken to prevent lateral lightning strike; For Class III lightning protection buildings, when the height exceeds 60m, the upper part of the building accounts for 20% of the height and the part exceeding 60m should be protected against side attack.
For example, if the height of a building is 70m, then 70×20%= 14m, it can be 14m, but when the height exceeds 60 m, it is only 10 m, so the side attack prevention measures are only taken at the part above 60m.
For another example, if the building is 80 m high, then 80×20%= 16m, 16m will do. 80m over 60m is 20m, so only the part above 64 m can be used as a side attack prevention measure.
5. Paragraph 1 2 of Article 4.5.7 clearly stipulates the lightning protection measures for the second and third types of lightning protection buildings, isolated metal roof objects and non-conductive roof objects.
6. The new provisions of Article 4.2.4, Paragraph 8 (Category I), Article 4.3.8, Paragraphs 4 and 5 (Category II) and Article 4.4.7, Paragraph 2 (Category III) have made mandatory provisions on the requirements for selecting surge protectors for electrical systems: (1) A surge protector with level I test shall be installed at the main distribution box leading into the power supply.
When it is impossible to calculate and determine, the surge current impi of each protection mode is ≥12.5 ka; When connection form 2(3P+N) in J. 1.2 of this specification is adopted, the surge current of surge protector between neutral line and PE line is impi≥ 12.5 ka×4 = 50ka (three-phase system);
ImpI≥ 12.5kA×2=25 kA for single-phase system. The most common connection form is 1, in which the surge current of surge protector between sex line and PE line is impI≥ 12.5kA.
In addition, Articles 4.2.4, 1 1, 12 (category I), 4.3.8, 7 and 8 (category II) and 4.4.7, 3 and 4 (category III) respectively have negative effects on the surge protection of electronic systems. See the new regulations for details.
.4.
. Reinforced concrete buildings are 20 meters long and 25 meters wide. Diameter. At this time, the lightning current Iimp = 1ck×0 flowing through the steel pipe.
× 150 = 0.44× 150 = 66kA； The shunt through SPD is Iimp=2ck66? =[( 1/n)+0. 1]×66 = 0. 15×66 = 9.9 kA。 . The roof distribution box is a three-phase TN-S system. When SPD is installed, the shunt is 5 molecules.
Considering the circuit (3-phase line, 1 N line, 1 PE line), the current flowing through each SPD is 10/350s? Then Iimp=9.9/5≈2 kA. , usually the same as 8/20s? The nominal discharge current nI can be switched 10 times. Namely:
(2) Paragraph 3 of the new regulation 4.5.4 stipulates that holiday lanterns and aviation are fixed on buildings.
nI= 10Iimp= 10×2=20
(kA。 ), generally 8/20? The nominal discharge current nI of waveform SPD is half of its maximum discharge current maxI, so Ni =10 impi =10× 2 = 20 (ka. ). The voltage drop of lightning current on the steel pipe is 66× (0.12× 20)/100 =1.584 (kV. )= 1584 (V)。
According to Article 4.4.7, Paragraph 2 of the new code GB50057-20 10, the lightning current of the three types of lightning protection buildings is considered as 100kA. Under this condition, the lightning current iimp =1CK×100 = 0.40 when other conditions are the same as those of the second type lightning protection buildings. Waveform current Iimp=244ck? =[( 1/n)+0. 1]×44 = 6.6(kA。 )。 The roof distribution box is a three-phase TN-S system. When installing SPD, the shunt is considered as a 5-molecule loop (3-phase line, 1 N line, 1 PE line), and the current flowing through each SPD is 10/350s? ，iimp = 6.6/5 = 1.32≈ 1.5(ka)。 That is, ni =10 impi =10×1.5 =15 (ka. ). The lightning current is at 25? The voltage drop on the steel pipe is 44× (0.12×× 20)/100 =1.056 (kv. )= 1056 (V)。
(3) The installation of the surge protector in the distribution box of the roof ventilator is similar to that in the distribution box such as holiday lights, except that the power switch of the distribution box is generally turned on.
(4) According to the second paragraph of Article 6.4.5 of the new regulations, when SPD needs to be installed near the protected equipment, that is, LPZ2 area and high interface, the SPD with Grade II or III test should be selected for the electrical system; In addition, according to the third paragraph of Article 6.4.5 of the new regulation, the surge protector of the electrical system should cooperate with the surge protector at the upstream of the same line in energy, and the cooperation information should be provided by the manufacturer. Without this information, the nominal discharge current (nI) of the surge protector in the secondary test should not be less than 5kA；; The rated discharge current (nI) of the surge protector in the three-level test shall not be less than 3kA. The new regulations 6.4.5 to 6.4.6 stipulate the voltage protection level (pU) of SPD.
(5) Electronic systems are divided into metal wires and optical cables, and different types of surge protectors are installed according to the first, second and third lightning protection buildings. See Articles 4.2.4, 1 1, 12, 4.3.8, 7.8, 4.4.7 and 3.4 of the new regulations for details. Namely:
D 1 high-energy experimental surge protector is selected for metal lines, with short-circuit currents of 2kA, 1.5kA,1ka; They are;
The incoming cable adopts B2 type slow-rise test surge protector, and the short-circuit currents are 100 A, 75A and 50A respectively.
Obstacle signal lights and other electrical equipment (including roof ventilation distribution box) should be switched in the distribution box.