Surge protection coordination and optimization method of communication power supply system

Abstract

The invention discloses a surge protection coordination and optimization method for a communication power supply system, and relates to the technical field of lightning protection, and the method comprises the following steps: selecting a proper SPD for simulation experiment research according to the composition of the communication power supply system, and constructing an SPD model; analyzing the overvoltage and energy standard according to the constructed SPD model; the waveform of the fault traveling wave reaching the upstream SPD changes along with the change of the lightning stroke position, and time domain and frequency domain analysis is carried out on the change; reasonable optimization and coordination suggestions are obtained according to the found factors which can influence the overvoltage waveform reaching the load and the overvoltage waveform reaching the SPD at each level; aiming at the protection problem of a communication power supply system when the communication power supply system suffers from lightning surge, the invention provides a method for optimizing coordination between multiple stages of SPDs as well as between the SPD and a protected device, and by attenuating the lightning surge step by step and reasonably configuring the starting voltage, the energy absorption capability and the overvoltage level of each stage of SPD, the surge protection performance of the power supply system is improved. And the lightning tolerance and reliability of the communication power supply system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lightning protection, and in particular to a surge protection coordination and optimization method for a communication power supply system. Background Art

[0002] Lightning conductors and arresters in transmission lines effectively prevent direct lightning strikes. However, when a lightning strike occurs, the phase lines are subject to strong electromagnetic interference, causing induced lightning surges that reach the communications power system, impacting power supply stability. To achieve lightning surge protection, multiple levels of surge protective devices (SPDs) are often required, depending on the overvoltage category of the protected equipment and the wiring of the electrical installation. In this case, effective SPD coordination should be verified to prevent excessive stress on downstream SPDs while also limiting overvoltage levels to below the withstand voltage of the protected equipment.

[0003] In recent years, the research on SPD and the coordination between SPDs has been implemented in various systems and has achieved certain results. However, in reality, due to the frequent occurrence of power outages and short circuits in communications due to lightning strikes in communication power systems, it is still necessary to invest a lot of energy in the detailed research and improvement of surge protection in communication power systems. In the multi-level protection design of communication power systems, SPD is generally used as the core protection component. By reasonably selecting SPDs of different types and rated voltages and coordinating multiple levels of SPDs, the step-by-step attenuation of lightning surges can be effectively achieved. The efficient coordination and optimization method of this application is used to solve the above problems. Summary of the Invention

[0004] The object of the present invention is to provide a surge protection coordination and optimization method for a communication power supply system, so as to solve the problems existing in the prior art mentioned in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The surge protection coordination and optimization method for a communication power system includes the following steps:

[0007] S1: Select appropriate SPD according to the composition of the communication power system for simulation experimental research and build an SPD model;

[0008] S2: Analyze overvoltage and energy standards based on the constructed SPD model;

[0009] S3: The waveform of the fault traveling wave reaching the upstream SPD will change with the change of the lightning strike position. This change is analyzed in the time domain and frequency domain.

[0010] S4: The factors that affect the overvoltage waveform reaching the load and the overvoltage waveform reaching each level of SPD are simulated and explored using electromagnetic transient software, and reasonable optimization and coordination suggestions are obtained.

[0011] Preferably, in S2, the upstream SPD generally operates before the downstream SPD to absorb a larger impact current. When the fault voltage is not sufficient to activate the upstream SPD, it is necessary to consider whether the line wave impedance is equal to the load impedance, whether the traveling wave is refracted and reflected, what conditions the line parameters must meet to enable the upstream SPD to start first, and to judge the impact of the load condition on it.

[0012] Preferably, the specific optimization process of the SPD is:

[0013] Calculate the steepness of the lightning surge current wave and prioritize the activation of the upstream SPD based on the matching relationship between the line impedance and the load impedance. Adjust the transmission line length between SPDs so that the voltage protection coordination between SPDs conforms to the laws of lightning surge energy transfer. During the SPD configuration process, consider the load characteristics to ensure that the surge voltage level at the device end is within a safe range. Finally, by comparing the success of energy coordination under different loads, the corresponding overvoltage standards are studied.

[0014] Preferably, the specific analysis steps in S2 are:

[0015] S21: Since the line wave impedance is usually much larger than the line resistance, for the convenience of analysis, the influence of the line resistance is ignored here. Assuming that the line is a lossless uniform transmission line, the line length is l, the unit inductance is L0, the unit capacitance is R0, and the line wave impedance is Propagation speed The time required for the wave to propagate from point A to point B is τ = l / v, and Z C τ=lL0;

[0016] The rising edge of the applied impulse current can be approximately regarded as an oblique wave, that is, I g =at, assuming that the current starts from point A at time 0, after time τ, the wave head of the current wave reaches point B. Before the upstream SPD is turned on, the voltage on the upstream SPD is U A for:

[0017]

[0018] When the current wave reaches point B, according to U A Is it greater than the startup voltage U of the upstream SPD? 1-1ma , need to be discussed in two situations;

[0019] S22: When U A ≥U 1-1maWhen the upstream SPD is turned on before the current wave reaches point B, the general judgment formula for whether the upstream SPD operates before the downstream SPD is:

[0020] Line length l or line wave impedance Z C When is known, the rising edge slope a of the impulse current wave satisfies

[0021]

[0022] When the steepness a of the external impulse waveform is known, the line length or line wave impedance satisfies

[0023]

[0024] From equations (2) and (3), it can be seen that under the action of steep or large-amplitude surge current, the upstream SPD is likely to operate before the downstream SPD. Increasing the length of the transmission line between the two-stage protectors can make the upstream SPD operate before the downstream SPD.

[0025] S23: When U A ≤U 1-1ma When considering the effect of load on current wave refraction and reflection, it is necessary to discuss the value of load and line wave impedance.

[0026] S24: When Z l =Z C When the load impedance is equal to the line wave impedance, the current wave is not reflected at point B and is completely refracted into the load. After the current wave reaches point B, the voltage on the downstream SPD is required to reach the starting voltage U 2-1ma , the required time t1 is:

[0027]

[0028] In order for the upstream SPD to operate before the downstream SPD, the line parameters must meet the following requirements:

[0029]

[0030] S25: When Z l ≠Z C When the load impedance is not equal to the line wave impedance, the current wave is reflected at point B, and the current entering the load I L for:

[0031]

[0032] The voltage on the load must reach U 2-1ma Value, the required time t2 is:

[0033]

[0034] In order for the upstream SPD to operate before the downstream SPD, the line parameters must meet the following conditions: H(w) is the refractive index and K(w) is the reflection coefficient.

[0035]

[0036]

[0037] Preferably, the specific analysis steps of S3 are:

[0038] S31: According to the superposition principle, any fault on a line can be decomposed into a normal operating component and a fault component. The fault component can be regarded as a transient mechanism attached to a voltage source. The fault-attached voltage source will generate a wide-band traveling wave signal with a step-like characteristic. This signal originates from the fault point and is refracted and reflected along the line impedance discontinuity.

[0039] S32: Lightning surge voltage is an external fault. From the perspective of frequency domain, the fault traveling wave has a wide frequency band. The wave impedance, transmission function, and refraction and reflection coefficients are all functions of frequency, as shown in Equations (9) to (13). Affected by factors such as the transmission function and refraction and reflection coefficients, the amplitude attenuation degree and phase change of each frequency component of the traveling wave are different during the transmission process.

[0040]

[0041] A(w)=e -γx (26)

[0042] Where: A(w) is the transmission function, α(w) and β(w) are the attenuation coefficients, R0, L0, C0, and G0 are the line distribution parameters. When the lightning strike location is far away, the high-frequency component of the surge traveling wave will be greatly attenuated, resulting in a decrease in the steepness and amplitude of the surge reaching the SPD, thereby affecting the energy coordination between the SPDs. The impact on the energy coordination of the two SPDs was tested by changing the surge location generated by the lightning strike and the cable length between the SPDs.

[0043] Preferably, the specific steps in S4 are:

[0044] S41: When only the impact of lightning amplitude is considered, experiments are conducted using a surge generator that can generate 8 / 20µs direct lightning current to test the different distances between two series-connected SPDs. Energy coordination of the two-stage SPDs is studied, using SPD1 with a rated voltage of 660V and SPD2 with a rated voltage of 330V as examples. Lightning surge intrusion is also studied with lightning surge peak voltages of 10kV, 20kV, and 50kV.

[0045] S42: Taking four lightning strike locations as examples, namely 20m, 100m, 500m and 1km away, the energy absorption of the two-stage SPD is compared, and the inter-stage cable is appropriately extended for energy coordination;

[0046] S43: When the equipment is used as different loads, the system analyzes the electrical characteristics under three different loads, namely resistive, capacitive and resistive-capacitive loads, and makes optimization and coordination recommendations based on the analysis results.

[0047] Preferably, the present invention also includes experimentally exploring whether there is a correlation and influence between overvoltage and energy standards, providing a basis for whether the implementation of the two coordinated standards can be achieved separately.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The present invention addresses the issue of protecting communication power systems from lightning surges and proposes a method for optimizing the coordination between multiple levels of SPDs and between SPDs and protected devices. This method improves the lightning tolerance and reliability of communication power systems by gradually attenuating lightning surges and rationally configuring the starting voltage, energy absorption capacity, and overvoltage level of each level of SPDs.

[0050] 2. The present invention also considers the impact of different load conditions and lightning strike locations on the coordination of SPDs. Through simulation and experimental verification, specific optimization suggestions are put forward to ensure the coordination effect of SPDs under various complex situations. At the same time, the independence of the two coordination standards is obtained through this method, which not only improves the overall lightning resistance performance of the system, but also reduces resource waste, providing reliable protection for the stable operation of the communication power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a schematic diagram of the installation location of the multi-level protection SPD for the communication power system.

[0052] Figure 2 This is the wiring diagram of the two-stage voltage-limiting surge protector of the present invention.

[0053] Figure 3 This is the arrival time diagram of each surge harmonic in the present invention.

[0054] Figure 4 This is a time domain difference diagram of different lightning strike positions of the present invention.

[0055] Figure 5 This is a frequency domain difference diagram of different lightning strike positions of the present invention.

[0056] Figure 6 This is a diagram showing the relationship between energy coordination, voltage magnitude, and inter-stage cable length for the two-stage surge protection of the present invention.

[0057] Figure 7 This is a comparison diagram of energy absorption of cables between different levels of the two-level SPD at different lightning strike locations of the present invention.

[0058] Figure 8 Figure 2 is an overvoltage waveform diagram of different resistive loads of the present invention.

[0059] Figure 9 Figure 4 is an overvoltage waveform diagram of different capacitive loads of the present invention.

[0060] Figure 10 Figure 2 is an overvoltage waveform diagram of different resistive and capacitive loads according to the present invention.

[0061] Figure 11 This is a comparison diagram of energy absorption by the two-stage SPD under different conditions when the load is a resistor.

[0062] Figure 12 This is a comparison diagram of energy absorption of the two-stage SPD under different conditions when the load is a capacitor. DETAILED DESCRIPTION

[0063] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0064] See also Figure 1-12 , the present invention provides the following technical solutions:

[0065] Most of the interference or damage caused by lightning to the power supply of the communication power system is caused by the intrusion of the distribution system. In order to prevent lightning from intruding into the telecommunications equipment through the power lines as much as possible, the surge protection measures of the communication power system mostly adopt the secondary and tertiary protection of the low-voltage distribution system and install SPDs with different surge flow levels to improve the lightning tolerance of the communication power system. Figure 1 shown.

[0066] (1) Level 1 protection: voltage is around 6kV; 220 / 380VAC low-voltage main distribution panel input and main oil generator conversion panel input.

[0067] (2) Secondary protection: voltage is around 4kV, rectifier used at the input of AC distribution panel, UPS switch power input, and communication room in communication building.

[0068] (3) Level 3 protection: voltage is around 1kV, the input terminal of the AC distribution cabinet for communication equipment in the central computer room, the power input terminal of the communication air conditioner, and other locations including the input terminal of the outdoor 3G / 4G / 5G base station power system.

[0069] There are two common types of SPDs: voltage-switching SPDs and voltage-limiting SPDs. In practical applications, they are mostly installed in parallel or with Kelvin connections at all input ports of low-voltage distribution systems. Transient suppression diodes (TSDs) have fast response times but low flow rates. In practical applications, they are often used in conjunction with gas discharge tubes (GDTs). Due to their low parasitic capacitance, they are widely used in signal lines. However, switching SPDs inevitably experience arcing and continuous current issues, posing a threat to subsequent protected equipment. Voltage-limiting SPDs, on the other hand, are typically varistors, offering faster response times, stronger protection levels, and the ability to be equipped with monitoring interfaces for monitoring. Therefore, voltage-limiting SPDs were selected to construct the experimental model.

[0070] Typical wiring for two-stage voltage-limiting SPD coordination is as follows: Figure 2 As shown, the total energy input to the system increases with increasing surge voltage. The operating sequence of SPDs is closely related to the energy coordination of cascaded SPDs. When a surge current impacts an upstream SPD with a large magnitude, the upstream SPD can begin discharging first. The terminal voltage of the upstream SPD is equal to the sum of the terminal voltage of the downstream SPD and the voltage drop induced by the inductance of the leads connecting the upstream and downstream SPDs. The inductance of each pair of parallel leads is approximately 0.5 μH / m to 1 μH / m.

[0071] The coordination of SPDs must strictly adhere to two core principles: energy distribution and voltage protection. In terms of energy distribution, upstream SPDs should bear more energy dissipation to ensure the overall protection effectiveness of the system. In terms of voltage protection, downstream SPDs, due to their proximity to the protected equipment, should have voltage protection thresholds no higher than those of upstream SPDs to provide more precise overvoltage protection. Furthermore, when the downstream SPD is activated, it must ensure that the overvoltage experienced by the equipment does not exceed its rated protection level to ensure safe operation.

[0072] Overvoltage and energy standards are analyzed based on the constructed SPD model. The upstream SPD generally operates before the downstream SPD to absorb larger inrush currents. When the fault voltage is insufficient to activate the upstream SPD, it is necessary to consider whether the line wave impedance is equal to the load impedance, whether the traveling wave is refracted and reflected, what line parameters must meet to enable the upstream SPD to activate first, and determine the impact of the load condition on this.

[0073] The specific SPD optimization process is as follows: calculate the steepness of the lightning surge current wave and prioritize the activation of the upstream SPD based on the matching relationship between the line impedance and the load impedance; adjust the transmission line length between SPDs so that the voltage protection coordination between SPDs conforms to the laws of lightning surge energy transfer; during the SPD configuration process, consider the load characteristics to ensure that the surge voltage level at the device end is within a safe range; finally, by comparing the success of energy coordination under different loads, the corresponding overvoltage standards are studied.

[0074] The steps for analyzing overvoltage and energy standards are:

[0075] (1) Since the line wave impedance is usually much larger than the line resistance, for the convenience of analysis, the influence of the line resistance is ignored here. Assuming that the line is a lossless uniform transmission line, the line length is l, the unit inductance is L0, the unit capacitance is R0, and the line wave impedance is Propagation speed The time required for the wave to propagate from point A to point B is τ = l / v, and Z C τ=lL0;

[0076] The rising edge of the applied impulse current can be approximately regarded as an oblique wave, that is, I g =at, assuming that the current starts from point A at time 0, after time τ, the wave head of the current wave reaches point B. Before the upstream SPD is turned on, the voltage on the upstream SPD is U A for:

[0077]

[0078] When the current wave reaches point B, according to U A Is it greater than the startup voltage U of the upstream SPD? 1-1ma , need to be discussed in two situations;

[0079] (2)When U A ≥U 1-1ma When the upstream SPD is turned on before the current wave reaches point B, the general judgment formula for whether the upstream SPD operates before the downstream SPD is:

[0080] Line length l or line wave impedance Z C When is known, the rising edge slope a of the impulse current wave satisfies

[0081]

[0082] When the steepness a of the external impulse waveform is known, the line length or line wave impedance satisfies

[0083]

[0084] From equations (2) and (3), it can be seen that under the action of steep or large-amplitude surge current, the upstream SPD is likely to operate before the downstream SPD. Increasing the length of the transmission line between the two-stage protectors can make the upstream SPD operate before the downstream SPD.

[0085] (3)When U A ≤U 1-1ma When considering the effect of load on current wave refraction and reflection, it is necessary to discuss the value of load and line wave impedance.

[0086] (4) When Z l =Z C When the load impedance is equal to the line wave impedance, the current wave is not reflected at point B and is completely refracted into the load. After the current wave reaches point B, the voltage on the downstream SPD is required to reach the starting voltage U 2-1ma , the required time t1 is:

[0087]

[0088] In order for the upstream SPD to operate before the downstream SPD, the line parameters must meet the following requirements:

[0089]

[0090] S25: When Z l ≠Z C When the load impedance is not equal to the line wave impedance, the current wave is reflected at point B, and the current entering the load I L for:

[0091]

[0092] The voltage on the load must reach U 2-1ma Value, the required time t2 is:

[0093]

[0094] In order for the upstream SPD to operate before the downstream SPD, the line parameters must meet the following conditions: H(w) is the refractive index and K(w) is the reflection coefficient.

[0095]

[0096]

[0097] In engineering practice, the load impedance at the load end cannot always be equal to the line impedance. As shown in Equations (9) and (10), the impact of different load conditions needs to be discussed. The experiment will be divided into resistive load, capacitive load, and resistive-capacitive load, and the impact of different values on the overvoltage will be tested.

[0098] The waveform of the fault traveling wave reaching the upstream SPD will change with the change of the lightning strike location. This change is analyzed in the time domain and frequency domain. The specific analysis steps are as follows:

[0099] (1) According to the superposition principle, any fault on the line can be decomposed into a normal operating component and a fault component. The fault component can be regarded as a transient mechanism attached to the voltage source. The fault-attached voltage source will generate a wide-band traveling wave signal with a step-like characteristic. It is generated from the fault point and refracted and reflected along the line impedance discontinuity.

[0100] From the perspective of time domain, Figure 3 It is the time domain situation of reflection and refraction in the transmission process of each traveling wave surge within a certain time window. Refraction is often more complicated. Taking the refraction at point M as an example, the refraction of different surge harmonics is different. If the fault location is different, the traveling wave transmission path is different, resulting in different refraction and reflection processes and wave head arrival timing, such as Figure 4 As shown in Figure 2, there are obvious differences in the traveling wave waveforms at the detection points.

[0101] (2) The lightning surge voltage is an external fault. From the perspective of frequency domain, the fault traveling wave has a wide frequency band. The wave impedance, transmission function, and refraction and reflection coefficients are all functions of frequency, as shown in Equations (9) to (13). Affected by factors such as the transmission function and refraction and reflection coefficients, the amplitude attenuation degree and phase change of each frequency component of the traveling wave are different during the transmission process.

[0102]

[0103] A(w)=e -γx (39)

[0104] Where: A(w) is the transmission function, α(w) and β(w) are the attenuation coefficients, R0, L0, C0, and G0 are the line distribution parameters. When the lightning strike location is far away, the high-frequency component of the surge traveling wave will be greatly attenuated, resulting in a decrease in the steepness and amplitude of the surge reaching the SPD, thereby affecting the energy coordination between the SPDs. The impact on the energy coordination of the two SPDs was tested by changing the surge location generated by the lightning strike and the cable length between the SPDs.

[0105] The factors that affect the overvoltage waveform reaching the load and the overvoltage waveform reaching each level of SPD are simulated and explored using electromagnetic transient software, and reasonable optimization and coordination suggestions are obtained. The specific steps are as follows:

[0106] (1) When only the influence of lightning amplitude is considered, experiments are conducted on different distances between two-stage series SPDs using a surge generator that can generate 8 / 20us direct lightning current. The energy coordination of two-stage surge protectors is studied using SPD1 rated voltage of 660V and SPD2 rated voltage of 330V as examples, and the lightning surge intrusion is studied with lightning surge peak voltages of 10kV, 20kV and 50kV.

[0107] The absorption energy of SPD1 and SPD2 is as follows Figure 6 The figure compares the energy absorption of upstream and downstream SPDs under different surge voltages. Based on the analysis in Section 1, when two SPDs work together, the upstream SPD should absorb more energy than the downstream SPD. When a lightning surge below 10 kV is injected and the distance between the two SPDs is less than 3 m, the downstream SPD absorbs more energy than the upstream SPD, indicating a failure in energy coordination between the two SPDs. However, when the distance between the two SPDs is greater than 3 m, energy is primarily concentrated in the upstream SPD, achieving energy coordination. This principle also applies to other surge voltage conditions: the greater the surge voltage, the shorter the critical cable length, meaning fewer interstage cables are required. This also indicates that for a protection module composed of multiple SPDs, the rated voltage of the preceding SPD should not be too low, as this will result in severe overvoltage attenuation. Careful distribution is required to avoid weakening or even negating the energy coordination of subsequent SPDs.

[0108] (2) The difference in lightning strike locations is also a cause of energy coordination failure. Taking four lightning strike locations as examples, namely 20m, 100m, 500m and 1km, the energy absorption of the two-stage SPDs is compared, and the inter-stage cables are appropriately extended for energy coordination.

[0109] like Figure 7 As shown in the figure, a comprehensive analysis of the four graphs leads to the following conclusion: As the distance of the lightning current increases, the energy absorbed by the two-stage SPD gradually decreases. When the interstage cable is short, SPD1 absorbs much less energy than SPD2. This can lead to an imbalance in energy distribution, causing SPD1 to fail during surge protection, while SPD2 may overheat and malfunction due to excessive energy absorption. Further analysis shows that if the lightning strike point is close, for example, 20 meters, the interstage cable length only needs to be approximately 4 meters for SPD1 to absorb more energy than SPD2. However, when the lightning strike point is 1 kilometer away, the interstage cable length needs to be at least 100 meters.

[0110] In general, as the distance from the lightning strike point increases, the required interstage cable length also increases significantly. This increase can alter the energy distribution between the two SPD stages, affecting their overall effectiveness. In this case, consider replacing the longer cable with an inductor or resistor. This increases the voltage drop, allowing SPD1 to trigger and conduct promptly when the surge current passes through, thereby sharing some of the surge energy and reducing the energy burden on the secondary SPD.

[0111] (3) When the equipment is used as different loads, the system analyzes the electrical characteristics under three different loads, namely resistive, capacitive and resistive-capacitive loads, and makes optimization and coordination recommendations based on the analysis results.

[0112] like Figure 7 As shown in Figure 2, the maximum overvoltage amplitude on 1Ω, 10Ω, 50Ω and 100Ω resistive loads is compared with the change of the distance between the SPD and the load; Figure 8 As shown in Figure 2, the maximum overvoltage amplitude on 0.1nF, 1nF, 10nF and 100nF capacitive loads is compared with the change of the distance between the SPD and the load; Figure 9 Figure 3 compares the maximum overvoltage amplitude on 10Ω / 10pF, 20Ω / 10pF and 50Ω / 10pF resistive and capacitive loads as a function of the distance between the SPD and the load.

[0113] Furthermore, based on the second SPD coordination criterion, the cable length between resistive and capacitive loads when the downstream SPD operates was tested to determine the minimum effective protection distance. For resistive loads, using a protection distance of 100m as an example, the peak overvoltage changes between the load and the downstream SPD after the downstream SPD operates were recorded. For capacitive loads, the overvoltage value at the point of maximum overvoltage difference between the two loads when the downstream SPD operates was recorded by adjusting the protection cable length. The specific data are shown in Tables 1 and 2. These analysis results provide important reference for optimizing SPD configuration and load protection.

[0114] Table 1 Effect of resistive load

[0115]

[0116] The results show that if the device is treated as a resistive load, the overvoltage value exhibits a smaller steepness only when the load impedance is sufficiently small. When the load impedance exceeds 50Ω, the overvoltage peak remains almost unchanged, but the steepness still increases with the load impedance. When the resistive load is less than the characteristic impedance of the connecting cable (84.5Ω), the load voltage does not spike, indicating that the SPD effectively protects the device and has an unlimited effective protection distance. If the resistive load is greater than the characteristic impedance of the cable, the load voltage will spike shortly after the SPD operates. When the resistive load exceeds 120Ω, the peak overvoltage value exceeds the SPD overvoltage, and the effective protection distance rapidly decreases, generally to within 10m. In this case, the final SPD protection must be close to the protected device to prevent it from failing to provide protection and even affecting the normal operation of the device.

[0117] Table 2 Capacitive load impact

[0118]

[0119] If the device is considered as a capacitive load, the voltage across the load will oscillate, and the oscillation will cause severe damage to the protected device. Figure 8 As shown, the frequency and amplitude of the oscillation vary with the capacitance value. Larger capacitance results in lower oscillation frequency and higher amplitude; smaller capacitance results in higher oscillation frequency and lower amplitude. In experiments, repeated adjustments to the capacitance and shield cable length failed to eliminate the oscillation. Table 2 shows that reducing the shield cable length can effectively reduce the amplitude of overvoltage oscillations, while higher capacitance requires shorter shield cables. Therefore, placing the secondary shield closer to the device or adding a series resistor is recommended to minimize the impact of oscillations.

[0120] If the device is considered as a resistive-capacitive load, such as Figure 9 As shown, similar to a capacitive load, oscillation will occur at both ends of the load, and the oscillation frequency and amplitude will change with the capacitance. However, since the resistor has a damping effect, the amplitude is also affected by the resistance. The larger the resistance, the smaller the amplitude; the smaller the resistance, the larger the amplitude.

[0121] The present invention also includes an experiment to explore whether there is a correlation and influence between overvoltage and energy standards, and to provide a basis for whether the implementation of the two coordination standards can be achieved separately. When both coordination standards of the two-stage SPD are met, the protection effect can be maximized, but whether the implementation of the two coordination standards can be achieved separately is also worthy of attention in practical applications, so in addition to this, the present invention also explores whether there is a mutual influence between them. For the two cases where the load is resistive and capacitive, a comparative experiment is conducted on whether the two-stage SPD successfully performs energy coordination and two lightning amplitudes to compare whether the overvoltage standard is met, where E1 is the secondary SPD overvoltage and E2 is the load overvoltage. The results are as follows: Figure 11 and Figure 12 shown.

[0122] When the load is a resistor, the overvoltage curves of several types are similar and difficult to observe, so a scatter plot is used, mainly observing the YZ projection direction, such as Figure 11 As shown in the figure. Comparing the same overvoltage at the same surge amplitude and the same overvoltage, it was found that the overvoltages for unsuccessful energy coordination were higher than those for successful coordination. Different surge amplitudes had little effect on the overvoltages for unsuccessful or successful energy coordination. However, for different overvoltages at the same surge amplitude, regardless of successful energy coordination, the load overvoltage did not exceed the overvoltage of the secondary SPD. This indicates that overvoltage coordination is not directly related to successful energy coordination.

[0123] Depend on Figure 12 It can be seen that the surge amplitude significantly affects the overvoltage magnitude. Under high surge conditions, uncoordinated two-stage SPDs generate higher secondary overvoltages and higher load overvoltages. Under the same surge amplitude, when energy coordination fails, the load overvoltage of the two-stage SPDs experiences greater voltage fluctuations than when coordination is successful. The larger the surge amplitude, the more pronounced the voltage fluctuations. This indicates that overvoltage coordination is directly influenced by successful energy coordination.

[0124] In summary, the present invention aims to solve the coordination problem of multi-stage surge protectors in a communication power supply system, thereby avoiding the malfunction of protection modules and unnecessary waste of resources, and even affecting the power supply of equipment.

[0125] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A surge protection coordination and optimization method for a communication power supply system, characterized in that: The following steps are involved: S1: Select appropriate SPD according to the composition of the communication power system for simulation experimental research and build an SPD model; S2: Analyze overvoltage and energy standards based on the constructed SPD model; S3: The waveform of the fault traveling wave reaching the upstream SPD will change with the change of the lightning strike position. This change is analyzed in the time domain and frequency domain. S4: The factors that affect the overvoltage waveform reaching the load and the overvoltage waveform reaching each level of SPD are simulated and explored using electromagnetic transient software, and reasonable optimization and coordination suggestions are obtained.

2. The method for coordination and optimization of surge protection for a communication power supply system according to claim 1, wherein: In S2, the upstream SPD generally operates before the downstream SPD to absorb larger inrush currents. When the fault voltage is insufficient to activate the upstream SPD, it is necessary to consider whether the line wave impedance is equal to the load impedance, whether the traveling wave is refracted and reflected, what line parameters must meet to enable the upstream SPD to start first, and to determine the impact of the load condition on it.

3. The method for coordination and optimization of surge protection for a communication power supply system according to claim 2, characterized in that: The specific optimization process of the SPD is as follows: Calculate the steepness of the lightning surge current wave and prioritize the activation of the upstream SPD based on the matching relationship between the line impedance and the load impedance. Adjust the transmission line length between SPDs so that the voltage protection coordination between SPDs conforms to the laws of lightning surge energy transfer. During the SPD configuration process, consider the load characteristics to ensure that the surge voltage level at the device end is within a safe range. Finally, by comparing the success of energy coordination under different loads, the corresponding overvoltage standards are studied.

4. The method for coordination and optimization of surge protection for a communication power supply system according to claim 1, wherein: The specific analysis steps in S2 are: S21: Since the line wave impedance is usually much larger than the line resistance, for the convenience of analysis, the influence of the line resistance is ignored here. Assuming that the line is a lossless uniform transmission line, the line length is l, the unit inductance is L0, the unit capacitance is R0, and the line wave impedance is Propagation speed The time required for the wave to propagate from point A to point B is τ = l / v, and Z C τ=lL0; The rising edge of the applied impulse current can be approximately regarded as an oblique wave, that is, I g =at, assuming that the current starts from point A at time 0, after time τ, the wave head of the current wave reaches point B. Before the upstream SPD is turned on, the voltage on the upstream SPD is U A for: When the current wave reaches point B, according to U A Is it greater than the startup voltage U of the upstream SPD? 1-1ma , need to be discussed in two situations; S22: When U A ≥U 1-1ma When the upstream SPD is turned on before the current wave reaches point B, the general judgment formula for whether the upstream SPD operates before the downstream SPD is: Line length l or line wave impedance Z C When is known, the rising edge slope a of the impulse current wave satisfies When the steepness a of the external impulse waveform is known, the line length or line wave impedance satisfies From equations (2) and (3), it can be seen that under the action of steep or large-amplitude surge current, the upstream SPD is likely to operate before the downstream SPD. Increasing the length of the transmission line between the two-stage protectors can make the upstream SPD operate before the downstream SPD. S23: When U A ≤U 1-1ma When considering the effect of load on current wave refraction and reflection, it is necessary to discuss the value of load and line wave impedance. S24: When Z l =Z C When the load impedance is equal to the line wave impedance, the current wave is not reflected at point B and is completely refracted into the load. After the current wave reaches point B, the voltage on the downstream SPD is required to reach the starting voltage U 2-1ma , the required time t1 is: In order for the upstream SPD to operate before the downstream SPD, the line parameters must meet the following requirements: S25: When Z l ≠Z C When the load impedance is not equal to the line wave impedance, the current wave is reflected at point B, and the current entering the load I L for: The voltage on the load must reach U 2-1ma Value, the required time t2 is: In order for the upstream SPD to operate before the downstream SPD, the line parameters must meet the following conditions: H(w) is the refractive index and K(w) is the reflection coefficient.

5. The method for coordination and optimization of surge protection for a communication power supply system according to claim 1, wherein: The specific analysis steps of S3 are: S31: According to the superposition principle, any fault on a line can be decomposed into a normal operating component and a fault component. The fault component can be regarded as a transient mechanism attached to a voltage source. The fault-attached voltage source will generate a wide-band traveling wave signal with a step-like characteristic. This signal originates from the fault point and is refracted and reflected along the line impedance discontinuity. S32: Lightning surge voltage is an external fault. From the perspective of frequency domain, the fault traveling wave has a wide frequency band. The wave impedance, transmission function, and refraction and reflection coefficients are all functions of frequency, as shown in Equations (9) to (13). Affected by factors such as the transmission function and refraction and reflection coefficients, the amplitude attenuation degree and phase change of each frequency component of the traveling wave are different during the transmission process. A(w)=e -γx (13) Where: A(w) is the transmission function, α(w) and β(w) are the attenuation coefficients, R0, L0, C0, and G0 are the line distribution parameters. When the lightning strike location is far away, the high-frequency component of the surge traveling wave will be greatly attenuated, resulting in a decrease in the steepness and amplitude of the surge reaching the SPD, thereby affecting the energy coordination between the SPDs. The impact on the energy coordination of the two SPDs was tested by changing the surge location generated by the lightning strike and the cable length between the SPDs.

6. The method for coordination and optimization of surge protection for a communication power supply system according to claim 1, wherein: The specific steps in S4 are: S41: When only the impact of lightning amplitude is considered, experiments are conducted using a surge generator that can generate 8 / 20µs direct lightning current to test the different distances between two series-connected SPDs. Energy coordination of the two-stage SPDs is studied, using SPD1 with a rated voltage of 660V and SPD2 with a rated voltage of 330V as examples. Lightning surge intrusion is also studied with lightning surge peak voltages of 10kV, 20kV, and 50kV. S42: Taking four lightning strike locations as examples, namely 20m, 100m, 500m and 1km away, the energy absorption of the two-stage SPD is compared, and the inter-stage cable is appropriately extended for energy coordination; S43: When the equipment is used as different loads, the system analyzes the electrical characteristics under three different loads, namely resistive, capacitive and resistive-capacitive loads, and makes optimization and coordination recommendations based on the analysis results.

7. The method for coordination and optimization of surge protection for a communication power supply system according to claim 1, wherein: It also includes experiments to explore whether there is a correlation and impact between overvoltage and energy standards, and to provide a basis for whether the implementation of the two coordinated standards can be achieved separately.

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