Preface role <br> <br> mine is to prevent lightning current lightning damage resulting from electronic equipment, electronic products is essential to protect the device. As more and more electronic products are applied to people's lives, lightning arresters are becoming more and more familiar to everyone. In fact, the lightning protection of electronic systems is still a relatively new field. There are still many issues in the selection and application of lightning protection devices. This article explains the response time of lightning arresters and the sequence of actions of multi-stage lightning protectors.
When the operation of the multi-stage sequentially <br> <br> lightning when lightning single stage can not be compromised to a predetermined impact protection overvoltage suppression level of the surge protection should be employed comprising two, three or more Lightning arrester for non-linear suppression components.
The non-linear components Rv2 and Rv2 are varistors. In practice, RV1 can also make the gas discharge tube. Rv2 can also be a surge tube or a surge suppression diode (TVS tube). The isolation element Zs between the two poles may be an inductance Ls or a resistance Rs. If the ON voltages of RV1 and RV2 are Un1 and Un2, respectively, the selected element is always Un2>Un1.
Some people think that when the intrusion shock wave is added to the XE terminal, it is always the first level RV1 lead copper, and then it is the second level. In fact, first-order or second-level conduction is possible, depending on the following factors:
(1) The waveform of the intrusion shock wave is mainly the sound wave velocity (di/dt) of the current wavefront;
(2) Relative magnitudes of the on voltages Un1 and Un2 of the nonlinear elements Rv1 and RV2;
(3) The nature of the isolation impedance Zs is resistance or inductance, and their size.
When Zs is the resistance Rs, most of the cases are the second-stage conduction. After the second stage turns on, when the inrush current I rises to iRs+Un2≥Un1, the first stage turns on. After the first stage is turned on, the equivalent impedance of the first stage is much smaller than the sum of the equivalent impedance of the second stage at the large current. Therefore, most of the inrush current is discharged through the first stage, and the current through the second stage is much smaller. If the first stage is a gas discharge tube, its residual voltage after conduction is usually lower than the second-stage conduction voltage Un2, so the second stage is cut off, and the remaining inrush current is discharged through the first stage gas discharge tube.
If Zs is the inductance Ls, and the inrush current begins to rise rapidly, the condition Ls(di/dt)+Un2>Un1 is satisfied, and the first stage is turned on first. If the limiting voltage when the first stage is on is Uc1(1), then it will decrease with the inrush current increasing speed (di/dt) later when the condition UC1(1)≥Ls(di/dt)+Un2 is satisfied. Only the second level leads. After the second stage turns on, the voltage at output Y is suppressed to a lower level.
SPD response time <br> <br> many people mistakenly believe that the response time is an important indicator to measure the performance of lightning protection, the manufacturer is also its technical information set out in this argument, but many The manufacturer did not know its exact meaning, nor did it measure it. A popular point of view is that, during the response time, the lightning arrester has no inhibitory effect on the impact of the intrusion. The surge voltage is applied to the lower-level device through the lightning protector as it is. This does not comply with the working principle of lightning protection devices and is wrong.
The non-linear elements in the lightning arrester that suppress the impact overvoltage can be divided into "limited voltage type" (such as varistors, zener diodes) and "switch type" (such as gas discharge tubes) according to its working mechanism. Thyristor).
A zinc oxide varistor is a compound semiconductor device in which the current is very fast in response to the voltage applied to it.
Then, what happened to the lightning protection device constructed by using a varistor in the previous technical documents?
This is the response time defined in the technical standard IEEE C62.33-1982 [2]. It is a physical quantity used to characterize "overshoot" characteristics, and is a completely different concept from the usual sense of response time. To illustrate this point.
IEEEC62.3 (6.3) Voltage Overshoot (UOS). In the case of steep and large values ​​of the front of the impulse current wave front, the measurement of the limit voltage of the leaded varistor shows that it is greater than the limit voltage at the 8/20 standard wave. This voltage increment UOS is called "overshoot." Although the varistor material itself has a different response time to a steep shock, the difference is not significant. The main cause of overshoot is the establishment of a magnetic field around the current-carrying lead of the device, which is in the loop between the device lead and the protected circuit, or between the lead and the measurement circuit that simulates the protected circuit. The loop induces voltage.
In a typical use case, a certain lead length is unavoidable, this additional voltage will be added to the protected circuit behind the varistor, so measured in the shock wave front very steep and large values When limiting the voltage, it is necessary to recognize the dependence of the voltage overshoot on the lead length and the loop coupling, and not to view the overshoot as the intrinsic characteristic of the device.
The International Electrotechnical Commission published in recent years on the lightning arrester technical standards IEC61643-1 and IEC6163-21 did not introduce the response time parameter: IEEE technical standard C62.62-2000 [] more clearly pointed out that the wavefront response technology The requirement is not necessary for the typical application of the lightning protector, and may cause misleading technical requirements. Therefore, if there is no special requirement, the technical requirement is not specified, nor is it tested, measured, calculated or otherwise certified. This is because:
(1) For the purpose of impact protection, the limit voltage measured under the specified conditions is a very important characteristic.
(2) The response characteristic of the surge protector to the wavefront is not only related to the internal reactance of the surge protector and the conductive mechanism of the nonlinear element that limits the impact voltage, but also related to the rising rate of the intruded shock wave and the impact source impedance. The length of the wire and the wiring method also have an important influence.
Xiao Bian believes that for power protection surge protectors, the following three technical indicators are important: 1 limit voltage (protection level); 2 flow capacity (impact current stability); 33 continuous operating voltage life.
In addition, there are many parameters: such as lightning protection device operating voltage, protection level, discharge current, etc., these parameters may not be very clear to outsiders, so we must choose more attention when lightning protection device, choose regular, suitable Lightning protection products.
When the operation of the multi-stage sequentially <br> <br> lightning when lightning single stage can not be compromised to a predetermined impact protection overvoltage suppression level of the surge protection should be employed comprising two, three or more Lightning arrester for non-linear suppression components.
The non-linear components Rv2 and Rv2 are varistors. In practice, RV1 can also make the gas discharge tube. Rv2 can also be a surge tube or a surge suppression diode (TVS tube). The isolation element Zs between the two poles may be an inductance Ls or a resistance Rs. If the ON voltages of RV1 and RV2 are Un1 and Un2, respectively, the selected element is always Un2>Un1.
Some people think that when the intrusion shock wave is added to the XE terminal, it is always the first level RV1 lead copper, and then it is the second level. In fact, first-order or second-level conduction is possible, depending on the following factors:
(1) The waveform of the intrusion shock wave is mainly the sound wave velocity (di/dt) of the current wavefront;
(2) Relative magnitudes of the on voltages Un1 and Un2 of the nonlinear elements Rv1 and RV2;
(3) The nature of the isolation impedance Zs is resistance or inductance, and their size.
When Zs is the resistance Rs, most of the cases are the second-stage conduction. After the second stage turns on, when the inrush current I rises to iRs+Un2≥Un1, the first stage turns on. After the first stage is turned on, the equivalent impedance of the first stage is much smaller than the sum of the equivalent impedance of the second stage at the large current. Therefore, most of the inrush current is discharged through the first stage, and the current through the second stage is much smaller. If the first stage is a gas discharge tube, its residual voltage after conduction is usually lower than the second-stage conduction voltage Un2, so the second stage is cut off, and the remaining inrush current is discharged through the first stage gas discharge tube.
If Zs is the inductance Ls, and the inrush current begins to rise rapidly, the condition Ls(di/dt)+Un2>Un1 is satisfied, and the first stage is turned on first. If the limiting voltage when the first stage is on is Uc1(1), then it will decrease with the inrush current increasing speed (di/dt) later when the condition UC1(1)≥Ls(di/dt)+Un2 is satisfied. Only the second level leads. After the second stage turns on, the voltage at output Y is suppressed to a lower level.
SPD response time <br> <br> many people mistakenly believe that the response time is an important indicator to measure the performance of lightning protection, the manufacturer is also its technical information set out in this argument, but many The manufacturer did not know its exact meaning, nor did it measure it. A popular point of view is that, during the response time, the lightning arrester has no inhibitory effect on the impact of the intrusion. The surge voltage is applied to the lower-level device through the lightning protector as it is. This does not comply with the working principle of lightning protection devices and is wrong.
The non-linear elements in the lightning arrester that suppress the impact overvoltage can be divided into "limited voltage type" (such as varistors, zener diodes) and "switch type" (such as gas discharge tubes) according to its working mechanism. Thyristor).
A zinc oxide varistor is a compound semiconductor device in which the current is very fast in response to the voltage applied to it.
Then, what happened to the lightning protection device constructed by using a varistor in the previous technical documents?
This is the response time defined in the technical standard IEEE C62.33-1982 [2]. It is a physical quantity used to characterize "overshoot" characteristics, and is a completely different concept from the usual sense of response time. To illustrate this point.
IEEEC62.3 (6.3) Voltage Overshoot (UOS). In the case of steep and large values ​​of the front of the impulse current wave front, the measurement of the limit voltage of the leaded varistor shows that it is greater than the limit voltage at the 8/20 standard wave. This voltage increment UOS is called "overshoot." Although the varistor material itself has a different response time to a steep shock, the difference is not significant. The main cause of overshoot is the establishment of a magnetic field around the current-carrying lead of the device, which is in the loop between the device lead and the protected circuit, or between the lead and the measurement circuit that simulates the protected circuit. The loop induces voltage.
In a typical use case, a certain lead length is unavoidable, this additional voltage will be added to the protected circuit behind the varistor, so measured in the shock wave front very steep and large values When limiting the voltage, it is necessary to recognize the dependence of the voltage overshoot on the lead length and the loop coupling, and not to view the overshoot as the intrinsic characteristic of the device.
The International Electrotechnical Commission published in recent years on the lightning arrester technical standards IEC61643-1 and IEC6163-21 did not introduce the response time parameter: IEEE technical standard C62.62-2000 [] more clearly pointed out that the wavefront response technology The requirement is not necessary for the typical application of the lightning protector, and may cause misleading technical requirements. Therefore, if there is no special requirement, the technical requirement is not specified, nor is it tested, measured, calculated or otherwise certified. This is because:
(1) For the purpose of impact protection, the limit voltage measured under the specified conditions is a very important characteristic.
(2) The response characteristic of the surge protector to the wavefront is not only related to the internal reactance of the surge protector and the conductive mechanism of the nonlinear element that limits the impact voltage, but also related to the rising rate of the intruded shock wave and the impact source impedance. The length of the wire and the wiring method also have an important influence.
Xiao Bian believes that for power protection surge protectors, the following three technical indicators are important: 1 limit voltage (protection level); 2 flow capacity (impact current stability); 33 continuous operating voltage life.
In addition, there are many parameters: such as lightning protection device operating voltage, protection level, discharge current, etc., these parameters may not be very clear to outsiders, so we must choose more attention when lightning protection device, choose regular, suitable Lightning protection products.
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