Selection Of Surge Protector Current Capacity (iimp, In, Imax)
1. Definition of flow rate parameters:
Impact current Iimp: The test waveform is 10/350μs, which is a T1 test. The first-level surge protector must have this parameter. The test values are usually: 12.5kA, 15kA, 25kA, 50kA;
Nominal discharge current In: The test waveform is 8/20μs, which is a T2 test. The test values are usually: 10kA, 20kA, 30kA, 40kA, 50kA, 60kA, etc.;
Maximum discharge current Imax: The test waveform is 8/20μs, which is a T2 test. The test value is usually twice In, such as 20kA, 40kA, 60kA, 80kA, 100kA, 120kA, etc.
2. Multi-level surge design size selection configuration
The lightning protection of the distribution system should be configured in a graded manner according to the standard requirements. The first-level protection should be able to withstand most of the lightning current. The second-level configuration discharges the residual lightning current and limits the residual voltage at the equipment end, while cooperating with the first-level protection.
①. The first-level protection of the power supply of the main distribution cabinet of the building:
GB50057-2010 Building Lightning Protection Design Code requires: A surge protector of level I test should be installed at the main distribution box where the power supply is introduced. The voltage protection level value of the surge protector should be less than or equal to 2.5 kV. The impact current value Iimp of each protection mode, when it cannot be determined, the impact current should be taken as ≥ 12.5 kA.
GB50343-2012 Technical Specification for Lightning Protection of Building Electronic Information Systems requires that the impulse current Iimp of the first-level surge protector of the highest-level building should be ≥20kA, and 25kA products are recommended to meet all requirements.
Recommended model: AM-10/350
Maximum continuous working voltage: 385V AC
Impact current Iimp: 25kA (10/350μs)
Nominal discharge current In: 25kA (8/20μs)
Protection level: ≤1.5kV
Protection mode: 4P, 3P+N, 3P, 2P, 1P+N optional
Response time: ≤25ns
Recommended wiring diameter: L/N (10mm2); PE (16mm2)
Recommended backup protection fuse rated current value: 100~125A
②Selection of first-level surge protection for outdoor equipment main distribution cabinet
The outdoor equipment main cabinet should select a first-level surge protector according to the lightning protection zone, but because it is impossible to design multi-level surge protection, the residual voltage of the internal surge protector will be fully loaded on the equipment. If a conventional first-level surge protector Up≤2.5kV or 2.0kV product is selected, Up is higher than the equipment withstand voltage Uw value, which may cause equipment damage (for the relationship between Up and Uw, please refer to Article 7 of this article).
Therefore, it is recommended to use a first-level surge protector with a protection level Up≤1.2kV. When the lightning protection standard is met, the low residual voltage design can better protect the equipment.
Recommended model: AM-L/N-BD
Maximum continuous working voltage Uc: 320VAC
Impact current limp (10/350μs): 12.5kA
Nominal discharge current In (8/20μs): 12.5kA
Protection level Up: 1.2kV
Combination: 4P, 3P, 3+NPE, 2P, 1P+N
Response time: ≤25ns
Recommended wiring diameter: L/N (10mm2); PE (16mm2)
Recommended backup protection fuse rated current value: 100~125A
③, Second level power supply protection:
The second level surge protector uses products with T2 test (8/20μs test waveform) parameters.
We recommend that the main switch of the distribution cabinet below 100A choose the AM40 series surge protector (Uc: 385V, In: 20kA, Imax: 40kA, Up: 1.8kV, 4P)
100A and above choose the AM80 series surge protector (Uc: 385V, In: 40kA, Imax: 80kA, Up: 2.1kV, 4P)
Secondary surge recommended model: AM40A
Maximum continuous working voltage Uc: 385V AC
Nominal discharge current In: 20kA (8/20μs)
Maximum current capacity Imax: 40kA (8/20μs)
Protection level Up: 1.7kV (In)
Protection mode: L1/L2/L3, N-PE
Response time: ≤25ns
Dimensions: 95×72×65mm
Recommended wiring diameter: L/N≥2.5mm²; PE≥6mm²
Recommended backup protection switch rated current value: 32~60A
④, Power supply third-level protection:
The third level is generally a single-phase power surge protector, and the third level uses products with T2 test (8/20μs test waveform) parameters, maximum current capacity (Imax) 20kA, nominal current capacity (In), maximum continuous working voltage 275VAC, protection level Up: 1.2kV.
Recommended model for the third-level lightning protection single-phase power supply system: AM20C275
Maximum continuous working voltage Uc: 275V AC
Nominal discharge current In: 10kA (8/20μs)
Maximum current capacity Imax: 20kA (8/20μs)
Protection level Up: 1.2kV
Protection mode: L, N-PE
Response time: ≤25ns
Dimensions: 95×36×65mm
Wiring diameter: L/N≥2.5mm²; PE≥6mm²
Recommended backup protection switch rated current value: 16A circuit breaker
Recommended model for the third-level lightning protection three-phase power supply system: AM20A
Maximum continuous working voltage: 385V AC
Nominal discharge current: 10kA (8/20μs)
Maximum current capacity: 20kA (8/20μs)
Protection level: 1.5kV
Protection mode: L1, L2, L3, N-PE
Response time: ≤25ns
Dimensions: 95×72×65mm
Wire diameter: L/N≥2.5mm²; PE≥6mm²
Recommended backup protection switch rated current value: 16A circuit breaker
⑤, fourth-level power supply protection:
The fourth-level power supply lightning protection generally uses a power supply lightning protection socket to provide fine protection for the equipment
