Lightning Surge immunity test

The lightning surge immunity test is to simulate the impact of lightning strikes (indirect lightning) in nature and voltage changes in power supply lines caused by switching of large switches on power supply lines and communication lines. The surge test specifies two waveforms (1.2/50 μ S and communication wave 10/700 μ s) The amplitude is 0.5kV to 4kV, and the energy is particularly large, which may have a destructive impact on the EUT. 10/700 μ S (commonly known as communication wave) is applicable to long-distance symmetrical communication port, 1.2/50 μ S Applicable to power line ports and other signal line ports.

Executive standard: IEC 61000-4-5 GB/T 17626.5

1.1 Cause of surge:

Switching transient of power system:

A) Main power system switching disturbance, such as capacitor bank switching;

B) Small local switch action or load change in the distribution system;

C) Resonance phenomenon associated with switching devices (such as thyristor);

D) Various system faults, such as short circuit and arc fault of equipment combination to grounding system.

Lightning transient:

A) Direct lightning strikes the external (outdoor) circuit, and the injected large current flows through the grounding resistance or external circuit impedance to generate voltage;

B) Indirect lightning (i.e. electromagnetic field generated by lightning strike between clouds or in clouds or lightning strike on nearby objects), and the induced voltage and current generated by it on the inside and outside conductors of the building;

C) The lightning current that discharges directly to the ground nearby will generate induced voltage when it is coupled to the common grounding path of the equipment combination grounding system.

D) When the lightning protection device acts, the voltage and current may change rapidly and may be coupled to the internal circuit.

1.2 Purpose of surge immunity test:

The purpose of surge immunity test is to establish a common benchmark to evaluate the performance of electrical and electronic equipment under surge (impact).

1.3 Surge immunity test standard:

The national standard for surge (impact) immunity test is GB/T17626.5-2008 Electromagnetic Compatibility Testing and Measurement Techniques Surge (Impact) Immunity Test, which is equivalent to the international standard IEC61000-4-5:2005

The standard describes two different waveform generators, one is (voltage waveform: 1.2/50us, current waveform: 8/20us) combined wave generator, and the other is in line with the requirements of the International Telecommunication Union Commission (voltage waveform: 10/700us, current waveform: 5/320us) combined wave generator.

1.4 Surge immunity test level:

The standard stipulates that the voltage between the standard grade line and the ground (common mode) is twice the voltage between the line and the line (differential mode).

1.5 Selection method of coupling/decoupling network

·The function of the coupling network is to transmit the surge signal of the combined-wave generator to the EUT, limit the damage to the generator body caused by the current flowing into the combined-wave generator from the power line, and reduce the impact on the surge waveform.

·The function of decoupling network is to provide sufficient decoupling impedance for the surge wave and avoid the adverse impact of surge channeling into the grid on the non-tested equipment powered by the same power supply.

·In addition, other equipment connected to the same power supply may contain lightning protection devices. Without the use of decoupling network, the lightning protection devices on the non-test equipment will prevent the application of surge on the EUT and affect the surge test results.

1.6 Test configuration:

The length of power line between EUT and coupling/decoupling network shall not exceed 2 m

Unless specified in relevant product standards, the number of surge pulses applied to the DC power supply terminal and the interconnection line shall be 5 times of positive and negative polarity respectively; For the AC current port, five surge pulses of positive and negative polarity shall be applied respectively at 0 °, 90 °, 180 ° and 270 ° phases, and the time interval between successive pulses shall be 1 minute or less.

If the EUT fails due to the test with a faster repetition rate of 1/min, but the EUT works normally when the test is carried out with a repetition rate of 1/min, then the test shall be carried out with a repetition rate of 1/min.

The climatic conditions of the laboratory should be within the normal working range of the equipment specified by the respective manufacturers of the EUT and test instruments. If the relative humidity is so high that condensation fog is generated on the EUT and test instruments, the test should not be carried out.

1.7 Surge immunity test results:

a) Normal performance within the limits specified by the manufacturer, the client or the purchaser

b) The function or performance is temporarily lost or degraded, but it can recover automatically after the disturbance is stopped without operator intervention;

c) The function or performance is temporarily lost or degraded, but can be recovered only after the intervention of the operator;

d) Unrecoverable function loss or performance degradation due to equipment hardware or software damage or data loss.