Method for distributing working voltage proportion of voltage dependent resistor and discharge tube series circuit

Abstract

The invention discloses a method for distributing the working voltage proportion of a voltage dependent resistor and discharge tube series circuit in the surge protection field. According to the method of the invention, after a voltage dependent resistor and a discharge tube are connected in series into a power-frequency power grid, a resistor is connected in parallel at the discharge tube, so that the load proportions of the working voltage of the power grid on various elements can be conveniently adjusted. According to the method disclosed by the invention, the discharge tube with a low direct-current breakdown voltage value can be selected, the amplitude of wave heads which are shifted before the discharge tube is switched on during the generation of surge is effectively reduced, a protection level is improved, and more margin for the tolerance of the abnormal fluctuation of the voltage of the power grid is realized.

Description

technical field [0001] The invention relates to the field of surge protection, in particular to a method for distributing the working voltage ratio of a series circuit of a piezoresistor and a discharge tube. Background technique [0002] It is a common method in surge protection technology to connect the varistor and the discharge tube in series to the power frequency grid. In the state of no surge, since the discharge tube is disconnected, there is almost no resistive current passing through the series circuit, only the inherent capacitance of the two components connected in series causes a weak capacitive current to pass through, and the capacitive current is multiplied by The respective capacitive reactance can be used to obtain the partial voltage of the grid operating voltage on each component, and the sum of the partial voltages of the two components is equal to the voltage at both ends of the series circuit (represented by Uc). The inherent capacitance value of the ...

AI Technical Summary

Problems solved by technology

[0003] Due to the extreme imbalance of the working voltage distribution, some disadvantages are brought about. First, the DC breakdown voltage value of the discharge tube needs to be selected higher, which increases the thickness of the discharge tube and increases the price; the second is to withstand abnormal fluctuations in the grid voltage. The capacity of the discharge tube is weak, unless the DC breakdown voltage value of the discharge tube is further greatly increased; the third is that after the DC breakdown voltage value of the discharge tube is increased, the corresponding impulse discharge voltage value will also increase, and the surge wave head will enter the subsequent stage The amplitude of the protected circuit will also be higher, which affects the protection effect

In addition, when the series circuit is used as a part of some more complex combination circuits, it will not achieve the best effect due to the unsatisfactory working voltage distribution.

[0004] Chinese invention patent number 201811040267.8 discloses a surge protection circuit, such as figure 2 As shown, in the actual application of this circuit, since the inherent capacitance of the discharge tubes GDT1 and GDT2 is very small, under the normal state without surge impact, the grid operating voltage at both ends of the circuit is almost all added to the two discharge tubes, while the GDT2's The DC breakdown voltage value cannot be selected too high, which will cause the circuit's ability to withstand abnormal fluctuations in grid voltage is not high

For example, in the usual 220V power frequency power grid, one of the more common grid faults is poor contact or open circuit of the zero line, causing the line voltage to rise to close to 380V for a short time. At this time, GDT2 will be turned on and the thermal protection function will be activated in advance. action, allowing the circuit to exit the grid without damage, causing waste

In a more special case, when Rv2 has deteriorated to a certain extent, Rv2 may also be broken down when encountering such a grid fault. At this time, the abnormal overvoltage of the grid up to 380 volts will be directly added to both ends of GDT1 , if its DC breakdown voltage value is lower than 550 volts, it will also conduct, causing Rv1 to break down and short circuit, so that the circuit's open circuit exits and the function of safety failure is lost, causing a short circuit fault in the grid line

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