the pulse group generator test uses interference to charge the line junction capacitance. when the energy on the junction capacitance accumulates to a certain extent, it may cause errors in the line (or even the system). therefore, there is a process of line error, and there is a certain contingency. it cannot be guaranteed that the error will occur at any interval, especially when the test voltage is close to the critical value. for this reason, some product standards stipulate that the test on the power line is conducted between the line and the ground. it is required to conduct three tests on one line under one test voltage polarity, one minute each time, with an interval of one minute: after one polarity is completed, change to another polarity. when one line is finished, change to another line. of course, pulses can also be injected into two lines, or even several lines at the same time. because the transmission process of the pulse group generator signal on the power line is very complex, it is difficult to judge whether to add pulses separately or together, and the equipment is more likely to fail.
therefore, adding pulses at the same time is only a form of experiment, and it is ultimately up to the experiment to draw a conclusion.
other standards (such as gb4343.2) stipulate that 2min positive polarity pulse shall be added to one line first, and then 2min negative polarity pulse shall be added after a short rest. it can be seen that different standards have different provisions, but they all have a relatively long test process to avoid contingency. and expose hidden dangers through a variety of combinations. usually, the test object is only sensitive to the test of one wire and one polarity.
burst immunity test is a kind of test that is difficult to pass in all common immunity tests, and it is also a kind of test with poor repeatability and comparability. therefore, in the description of this section, it is emphasized that the essence of this test is common mode test. because the waveform contains rich harmonic components and high upper limit frequency, the standardization of the test is particularly important.