JP7663201B2 - Information processing device, information processing method, display method, and computer program - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies. Published on January 25, 2021, in the High Voltage Study Group, Institute of Electrical Engineers Study Group Materials, pages 37 to 41, held on January 28 and 29, 2021. Published on January 28, 2021, at the High Voltage Study Group, Institute of Electrical Engineers of Japan. Published on August 1, 2021, in the Proceedings of the 39th National Conference of the Institute of Electrical Engineers of Japan.

The present invention relates to an information processing device, an information processing method, a display method, and a computer program.

When lightning strikes a building or near a building, the magnetic field fluctuates, causing a lightning surge to penetrate surrounding power lines and communication lines (induced lightning), or a lightning surge to penetrate through the ground wire due to an increase in the earth's potential (backflow lightning), causing failures in facilities and electrical and electronic equipment within the building. For this reason, lightning and EMC (Electromagnetic Compatibility) countermeasures are important in highly electronic societies, such as research facilities, hospitals, and factories (smart factories).

Patent Document 1 discloses a system that analyzes lightning surges in structures by applying an evaluation signal that models the waveform of a lightning surge to a circuit network model that combines circuit elements that are equivalent to metal structural members in a structure such as a building.

JP 2020-135181 A

In facilities and buildings, power is received from the power distribution system at a distribution board, and then supplied to electrical and electronic equipment through low-voltage wiring from the distribution board. Surge protective devices (SPDs) are installed on the distribution board to protect electrical and electronic equipment from lightning surges. In order to calculate the voltage generated at the end of low-voltage wiring due to a lightning surge that enters through the ground wire or power line, a complex numerical analysis method must be used, and no simple method for evaluating voltage has been established.

The present invention has been made in consideration of the above circumstances, and aims to provide an information processing device, an information processing method, a display method, and a computer program that can easily evaluate the voltage generated at one end of a wiring connected to a lightning arrester due to a lightning surge.

The present application includes multiple means for solving the above problem, and as an example, the information processing device of this embodiment is an information processing device that calculates the voltage at one end of a wiring connected to a lightning arrester at the other end, and includes a first acquisition unit that acquires first parameters including the crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and the wiring length from the one end to the other end, and a second voltage calculation unit that calculates a second voltage at the other end based on the first parameters acquired by the first acquisition unit.

The present invention makes it possible to evaluate the voltage generated by a lightning surge at the end of wiring (low-voltage wiring) that is connected downstream from the distribution board.

FIG. 1 is a diagram illustrating an example of a configuration of electrical equipment in a building. FIG. 2 is a diagram illustrating an example of an analysis circuit of an electrical facility constructed in the first embodiment. FIG. 13 is a diagram showing an example of values of a grounding system. FIG. 1 illustrates an example of a configuration of an information processing device. FIG. 1 is a diagram showing an example of a model of electrical equipment used in an EMTP analysis. FIG. 11 is a diagram illustrating an example of parameters used in an evaluation function for calculating a first voltage. FIG. 1 shows a first example of EMTP analysis. FIG. 13 shows a second example of EMTP analysis. FIG. 11 is a diagram illustrating an example of calculation of a correction coefficient. FIG. 13 is a diagram illustrating an evaluation function for calculating a first voltage. FIG. 4 is a diagram showing an example of evaluation of a first voltage according to the present embodiment. FIG. 1 is a diagram showing an example of a lightning surge entering a low-voltage wiring; FIG. 11 is a diagram illustrating an example of parameters used in an evaluation function for calculating a second voltage. FIG. 13 is a diagram illustrating an example of a second voltage when the number of reflections is 0. FIG. 13 is a diagram illustrating an example of a second voltage when the number of reflections is 1. FIG. 13 is a diagram illustrating an example of a second voltage when the number of reflections is two. FIG. 13 is a diagram illustrating an example of a second voltage when the number of reflections is three. FIG. 13 is a diagram illustrating an evaluation function for calculating a second voltage. FIG. 11 is a diagram showing an example of evaluation of a second voltage according to the present embodiment. FIG. 1 shows an example of EMTP analysis. FIG. 13 is a diagram illustrating an example of an analysis circuit of an electrical facility constructed in the second embodiment. FIG. 11 is a diagram illustrating an example of an evaluation of a second voltage according to the second embodiment. FIG. 13 is a diagram illustrating an example of an EMTP analysis according to the second embodiment. FIG. 2 is a diagram illustrating an example of a protection range of an SPD. FIG. 2 is a diagram showing a first method for identifying the protection range of an SPD. FIG. 13 illustrates a second method for identifying the protection range of an SPD. 10 is a flowchart showing a procedure of a calculation process of a first voltage by the information processing device. 10 is a flowchart showing a procedure of a calculation process of a second voltage by the information processing device. 10 is a flowchart showing a processing procedure of a first method for specifying a protection range by an information processing device. 10 is a flowchart showing a processing procedure of a second method for specifying a protection range by the information processing device. FIG. 13 is a diagram showing an example of an overvoltage calculation screen for an SPD installation location. FIG. 13 is a diagram showing an example of an overvoltage calculation screen for a load installation location. FIG. 13 is a diagram showing an example of a protection range calculation screen of an SPD.

The present invention will be described below with reference to the drawings showing the embodiment. FIG. 1 is a diagram showing an example of the configuration of electrical equipment in a building. In this embodiment, an evaluation method is provided for protecting electrical equipment from lightning surge overvoltages that enter low-voltage wiring via electric circuits and ground wires when lightning strikes a building or near the building. Specifically, an evaluation function is used to calculate the overvoltages that occur in electrical and electronic equipment (hereinafter also referred to as equipment or load) connected from a distribution board via low-voltage wiring, or the overvoltages that occur in the distribution board, and the protection range of an SPD (Surge Protective Device) installed in the distribution board is calculated. The protection range of an SPD can be expressed as the length of the low-voltage wiring, and the equipment connected from one end of the low-voltage wiring where the SPD is installed to the end (other end) of the low-voltage wiring can be the maximum length of the low-voltage wiring that the SPD can protect. In other words, equipment within the protection range from the point where the SPD is installed can be protected by the SPD.

As shown in FIG. 1, the electrical equipment in a building includes, for example, a distribution board 20 that receives power from a wiring system, and low-voltage wiring 10 (also simply called "wiring") is wired from the distribution board 20 to which a load 40 is connected. An SPD 30 is installed in the distribution board 20. The SPD 30 is connected to one end of the low-voltage wiring 10, and the load 40 is connected to the other end (terminal) of the low-voltage wiring 10.

The SPD 30 includes, for example, a voltage-limiting varistor between the phase wires, and a gas-filled discharge tube between the phase wires and the ground wire, and between the ground wire. The circuit model of the gas-filled discharge tube can be expressed as a circuit in which an internal inductance caused by wiring inside the SPD 30 is connected in series to a parallel circuit of a switch and a capacitor. In the initial state, the switch is off, and when the terminal voltage (voltage between the phase wire and the ground wire) becomes equal to or higher than the discharge start voltage Vf (threshold voltage), the switch is turned on. The discharge start voltage Vf can be 1.3 kV, but is not limited to this. In this embodiment, the lightning surge overvoltage that occurs between the phase wires and the ground wire is targeted against the lightning surge that enters from the ground wire and the electric circuit. In this case, since the phase wires are short-circuited, the phase-wire varistor is excluded from the consideration. When the SPD 30 operates, the switch is turned on, so the limiting voltage Vs of the SPD 30 can be 0 V. In the case of a varistor type, the limiting voltage is determined by the VI characteristics of the varistor.

The low-voltage wiring 10 is, for example, a 2 mm diameter, three-core VVF cable, with one core being a ground wire (represented by the symbol E) and the other two cores being phase wires (a power line represented by the symbol L and an N-phase wire represented by the symbol N), but is not limited to this. The phase wires are connected via the main line of a higher-level distribution system through a winding of a transformer (not shown), and the N-phase wire of the phase wires is connected to a system ground electrode (class B ground electrode). In the experiment, the VVF cable was installed 0.5 m above a copper plate laid on the ground to reproduce the distance to the steel frame of the building structure.

First Embodiment
In electrical equipment within a building, a type B ground (system ground) for an N-phase line and a protective ground (e.g., a housing ground) for equipment are buried separately. Therefore, a lightning strike generates a potential difference between the ground electrodes according to the earth potential distribution, and a lightning surge penetrates into the ground wire. In the first embodiment, a case in which a lightning surge penetrates into the low-voltage wiring 10 from a building (building structure) via a ground wire will be described first.

2 is a diagram showing an example of an analysis circuit of an electrical equipment constructed in the first embodiment. As shown in FIG. 2, the N-phase wire of the low-voltage wiring 10 and the power line L are connected on the secondary side of a transformer (not shown), and the N-phase wire is connected to a B-type ground electrode (system ground electrode). The ground wire to the B-type ground electrode can be represented by a series circuit of resistance Rb and inductance Lb, and the ground resistance is represented by the symbol R. The ground wire to the D-type ground electrode (casing ground electrode) of the SPD 30 can be represented by a series circuit of resistance Rg and inductance Lg. The internal inductance due to the wiring inside the SPD 30 is represented by the symbol Le. The inductance of the wiring from the phase wire to the SPD 30 is represented by the symbol Lf. The inductance Lg + Le + Lf is represented by the SPD-related inductance Ls. The symbol Vg is a voltage source that simulates a lightning surge waveform that enters from the ground wire.

The lightning surge voltage can be expressed by the crest value, the crest time (also called the crest length), and the tail time (also called the tail length). The crest value can be 30 kV, but is not limited to this. The lightning surge uses standard waveforms used in lightning surge tests, such as a trailing lightning stroke with a crest time/tail time of 0.25/100 μs, an impulse withstand test voltage of 1.2/50 μs, a direct lightning stroke with a crest time/tail time of 10/350 μs, and an induced lightning waveform with a crest time/tail time of 8/20 μs, but is not limited to these waveforms.

The lightning surge overvoltage (hereinafter referred to as overvoltage) at the installation location of the SPD 30 (one end of the low-voltage wiring 10) is V1 (first voltage), and the lightning surge overvoltage at the end (other end) of the low-voltage wiring 10 to which the load is connected is V2 (second voltage). The first voltage V1 is the overvoltage between the N-phase line and the ground line E, and the second voltage V2 is the overvoltage between the power line L and the ground line E when the end of the low-voltage wiring 10 is in an open state.

Figure 3 shows an example of values for the ground system. In this embodiment, for type B grounding (system grounding), the ground resistance R is 30Ω, the ground wire resistance Rb is 1 mΩ, and the ground wire inductance Lb is 0.1 μH. For type D grounding (chassis grounding), the ground wire resistance Rg is 5 mΩ, the ground wire inductance Lg is 1 μH, the internal inductance Le of the SPD 30 is 0.3 μH, and the wiring inductance Lf of the SPD 30 is 0.7 μH. The SPD-related inductance Ls (= Lg + Le + Lf) is 2 μH. Note that the values are merely examples and are not limited to those shown in Figure 3.

Figure 4 is a diagram showing an example of the configuration of the information processing device 50. The information processing device 50 may be a tablet terminal, a smartphone, or the like that can be carried by a user (e.g., a person in charge of designing, inspecting, and maintaining electrical equipment), or may be a personal computer. The information processing device 50 can easily calculate the second voltage V2 at the end of the low-voltage wiring 10 and the first voltage V1 at one end of the low-voltage wiring 10 where the SPD 30 is installed, simply by the user setting (or inputting) certain parameters. In addition, the information processing device 50 can easily identify the protection range (length of the low-voltage wiring 10) of the SPD 30. The information processing device 50 includes a control unit 51 that controls the entire device, a communication unit 52, a memory unit 53, a display panel 54, an operation unit 55, a display processing unit 56, a first voltage calculation unit 57, a second voltage calculation unit 58, a reflection count calculation unit 59, a protection range identification unit 60, and a necessity determination unit 61.

The control unit 51 can be configured with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The CPU can execute an application (app) stored in the storage unit 53, thereby allowing the app to run on the information processing device 50.

The storage unit 53 is composed of a semiconductor memory or a hard disk, etc., and can store required information. The storage unit 53 can store the analysis circuit exemplified in FIG. 2, the numerical values of the circuit elements exemplified in FIG. 3, etc. The storage unit 53 may store parameters set (or input) by the user. The storage unit 53 may also store the results of processing by the information processing device 50, information during processing, etc.

The communication unit 52 includes a communication module and can perform wired or wireless communication with an external device. The communication unit 52 can transmit and receive information with the external device. The communication unit 52 can receive and acquire parameters from the external device.

The display panel 54 can be configured with a liquid crystal panel or an organic EL (Electro Luminescence) display, etc. The operation unit 55 can acquire parameters by accepting an operation by the user to set (or input) parameters. The operation unit 55 can be configured with, for example, a touch panel incorporated in the display panel 54, and can perform predetermined operations performed by the user on the display panel 54. The operation unit 55 can perform operations on a keyboard displayed on the display panel 54. The operation unit 55 may be a hardware keyboard, a mouse, etc.

The display processing unit 56 performs processing to display the required screen on the display panel 54.

The first voltage calculation unit 57 calculates the first voltage V1 (overvoltage) at the location where the SPD 30 is installed (between the N-phase wire at one end of the low-voltage wiring 10 and the ground wire E) based on parameters (second parameters) including the discharge start voltage Vf of the SPD (lightning arrester) 30, the limit voltage Vs of the SPD 30, and the peak value of the surge current flowing through the SPD 30 due to a lightning surge. The second parameters may be obtained by the user operating the operation unit 55, or may be obtained from an external device via the communication unit 52. The method of calculating the first voltage V1 will be described in detail later.

The second voltage calculation unit 58 calculates a second voltage V2 (overvoltage) at the end (other end) of the low-voltage wiring 10 to which the load (apparatus) is connected, based on parameters (first parameters) including the crest time tr of the lightning surge, the first voltage V1 generated at one end of the low-voltage wiring 10 by the lightning surge, and the length (wiring length) L from one end to the other end of the low-voltage wiring 10. The first parameter may be obtained by the user operating the operation unit 55, or may be obtained from an external device via the communication unit 52. The value calculated by the first voltage calculation unit 57 may be used as the first voltage V1. The method of calculating the second voltage V2 will be described in detail later.

This makes it easy to evaluate the voltage generated at the end of the low-voltage wiring 10 that is connected downstream from the distribution board 20 due to a lightning surge.

The reflection count calculation unit 59 calculates the number of reflections that the lightning surge that entered the low-voltage wiring 10 makes as it travels back and forth between one end (short-circuited end) and the other end (open end) of the low-voltage wiring 10. The method for calculating the reflection count will be described in detail later.

The protection range specification unit 60 has a function as a specification unit and specifies the protection range of the SPD 30. When the SPD 30 is installed at one end of the low-voltage wiring 10 and a device (load) is connected to the other end, the protection range can be set as the maximum length of the low-voltage wiring that the SPD 30 can protect the device. Generally, the lightning surge overvoltage increases the farther away from the installation location of the SPD 30, so if the length of the low-voltage wiring 10 exceeds the protection range, the overvoltage (second voltage V2) at the end of the low-voltage wiring 10 will exceed the withstand voltage of the device, and it is therefore important to understand the wiring length of the low-voltage wiring 10 to protect the device. The method of specifying the protection range will be described in detail later.

The necessity determination unit 61 has a function as a determination unit, and determines whether an SPD is required at the other end of the low-voltage wiring 10 based on the second voltage V2 calculated by the second voltage calculation unit 58. For example, if the withstand voltage of the device connected to the other end is Vm, it can be determined that an SPD needs to be installed at the other end of the low-voltage wiring 10 if V2>Vm.

The EMTP (Electro Magnetic Transients Program) analysis method was used to confirm the validity of the evaluation function for calculating the first voltage V1 and the second voltage V2. EMTP is a numerical analysis method that models electrical equipment and inputs the lightning surge that penetrates the electrical equipment into the model to calculate the voltage and current at required locations. However, EMTP has the disadvantage that it is difficult to use unless you are an experienced engineer. In this embodiment, EMTP is used to calculate the first voltage V1' at one end of the low-voltage wiring 10 and the second voltage V2' at the other end, and based on the results, an evaluation function for calculating the first voltage V1 and the second voltage V2 in a simple manner (for example, by simply inputting parameters) is derived.

FIG. 5 is a diagram showing an example of a model of electrical equipment used in EMTP analysis. In the model, a route of a lightning surge entering a building structure or a grounding electrode to a grounding wire is assumed. A 3-core VVF cable with a diameter of 2 mm is used for the low-voltage wiring, with one core being the grounding wire E and the other two cores being phase wires (L, N). The VVF cable is installed 0.5 m above a copper plate laid on the ground to reproduce the distance from the structure. The phase wires are connected to the secondary side of the transformer via the trunk line, and the N phase wire is connected to a B-type grounding electrode. In the experiment, the phase wires are connected at the location where the SPD is placed, and are grounded via a 30 Ω resistor assuming B-type grounding. A 5.5 mm ² IV wire is used for the grounding wire for the SPD and the B-type grounding wire. The overvoltage at the location where the SPD is placed is V1', and the overvoltage at the end (open end) of the VVF cable is V2'.

First, we will explain how to find the evaluation function for calculating the first voltage V1 based on the overvoltage V1' obtained by EMTP analysis.

Figure 6 is a diagram showing an example of parameters used in the evaluation function for calculating the first voltage V1. As shown in Figure 6, the discharge start voltage of the SPD is Vf, the limit voltage of the SPD is Vs, the SPD-related inductance is Ls, the peak value of the lightning surge current flowing through the SPD is I, and the crest time of the lightning surge current flowing through the SPD is tr. That is, the crest time tr of the lightning surge current is the time until the value of the lightning surge current reaches the crest value. The SPD-related inductance Ls can be expressed as Ls = Ld + Le + Lf. Ld is the inductance of the ground line of the SPD, Le is the internal inductance of the wiring inside the SPD, and Lf is the inductance of the wiring of the SPD. The discharge start voltage Vf of the SPD is 1.3 kV, the limit voltage Vs of the SPD is 0 V, and the SPD-related inductance Ls is 2 μH. That is, Vf, Vs, and Lf are determined by the SPD specifications and the SPD wiring specifications and wiring length. In this embodiment, since the SPD is a gap type, Vs = 0 V, but if the SPD is a varistor type, Vs according to the VI characteristics of the SPD can be used.

Figure 7 shows a first example of EMTP analysis. Figure 7 shows the waveform of overvoltage V1' obtained by EMTP analysis when the crest time/tail time of the lightning surge waveform are 0.25/100 μs, 1.2/50 μs, and 10/350 μs, respectively. Overvoltage V1' is shown when the VVF cable lengths are 5 m, 10 m, 30 m, and 50 m, respectively.

When the crest time/tail time of the lightning surge waveform is 0.25/100μs, Vf = -1.3kV, the peak voltage indicated by the symbol P represents Ls·dI/dt, and its value is -8.8kV. When the crest time/tail time of the lightning surge waveform is 1.2/50μs, Vf = -1.3kV, the peak voltage indicated by the symbol P represents Ls·dI/dt, and its value is -2.16kV. When the crest time/tail time of the lightning surge waveform is 10/350μs, Vf = -1.3kV, the peak voltage indicated by the symbol P represents Ls·dI/dt, and its value is -0.25kV.

If we look at the maximum peak of the overvoltage V' in the cases of 0.25/100μs, 1.2/50μs, and 10/350μs, we can see that in the cases of 0.25/100μs and 1.2/50μs, Ls·dI/dt is the maximum peak, and in the case of 10/350μs, Vf is the maximum peak. In other words, when |Ls·dI/dt|>|Vf|, the overvoltage V1' can be expressed as V1'=Ls·dI/dt, and when |Ls·dI/dt|<|Vf|, V1'=Vs, and in the case of the gap type, Vs=0, so it can be expressed as V1'=Vf.

Figure 8 shows a second example of EMTP analysis. Figure 8 shows the current I flowing through the SPD, overvoltage V1', and Ls·dI/dt when the crest time/tail time of the lightning surge waveform using the Hydra function are 0.25/100 μs, 1.2/50 μs, and 10/350 μs, respectively. Ls·dI/dt is calculated using the current I. Focusing on overvoltage V1' and Ls·dI/dt, it can be seen that overvoltage V1' can be calculated by V1' = Ls·dI/dt. However, since there is a slight difference between V1' and Ls·dI/dt, by correcting this difference, overvoltage V1' can be reproduced with even greater accuracy.

Figure 9 shows an example of how the correction coefficient is calculated. In Figure 9, the crest value I (kA) of the lightning surge current, the crest speed (I/tr), the crest speed dI/dt obtained from the Hydra function, and the correction coefficient are shown for each crest time (tr).

When the crest time tr is 0.25 μs, if the crest value I of the lightning surge current is 1 kA, the crest speed (I/tr) is 4 (= 1/0.25). The crest value I of the lightning surge current may be calculated simply as I = 30 kv/30 Ω = 1 kA if the crest value of the lightning surge voltage is 30 kV and the ground resistance R of the system ground (class B ground) is 30 Ω. The crest speed dI/dt obtained from the Hydra function is 4.4 when calculated from the waveform in Figure 8. The crest speed dI/dt obtained from the Hydra function is 1.1 times larger than the value calculated from the crest value and crest time of the lightning surge current, so when calculating the first voltage V1 from the crest value and crest time of the lightning surge current, the accuracy of the first voltage V1 can be improved by using B = 1.1 as the correction coefficient B.

When the crest time tr is 1.2 μs and the crest value I of the lightning surge current is 1 kA, the crest speed (I/tr) is 0.83 (= 1/1.2). The crest speed dI/dt obtained from the Hydra function is 1.08 when calculated from the waveform in Figure 8. The crest speed dI/dt obtained from the Hydra function is 1.3 times larger than the value calculated from the crest value and crest time of the lightning surge current, so when calculating the first voltage V1 from the crest value and crest time of the lightning surge current, the accuracy of the first voltage V1 can be improved by using a correction coefficient B of B = 1.3.

When the crest time tr is 10 μs, the first voltage V1 is calculated by V1 = Vf, and the crest speed dI/dt is not used, so no correction coefficient is required. In this case, the correction coefficient B can be set to 1.

Using the EMTP analysis results, the evaluation function for calculating the first voltage V1 can be summarized as follows:

Figure 10 shows the evaluation function for calculating the first voltage V1. When |Ls·dI/dt|<|Vf|, the first voltage V1 can be calculated by the formula V1=Vf. When |Ls·dI/dt|>|Vf|, the first voltage V1 can be calculated by the formula V1=Vs+B·Ls·dI/dt. To estimate on the safe side, the first voltage V1 can be estimated higher by calculating V1=β1·V1, where β1>1.

As described above, the first voltage calculation unit 57 can calculate the first voltage using different calculation formulas depending on the magnitude of the multiplication value of the time change dI/dt of the lightning surge current and the associated inductance Ls, and the discharge start voltage Vf of the SPD 30. This makes it possible to accurately calculate the overvoltage (first voltage V1) at the installation location of the SPD 30 for each lightning surge with different crest time and crest time. Note that the time change dI/dt of the lightning surge current may be calculated using the formula I/tr, where I is the crest value of the lightning surge current and tr is the crest time of the lightning surge current.

The first voltage calculation unit 57 can also calculate the first voltage using a correction coefficient B that corresponds to the crest time tr of the lightning surge. This allows the overvoltage (first voltage V1) at the location where the SPD 30 is installed to be calculated with high accuracy.

Figure 11 is a diagram showing an example of an evaluation of the first voltage V1 according to this embodiment. Figure 11 shows the calculated values of overvoltage V1' by EMTP when the crest time tr is 0.25 μs, 1.2 μs, and 10 μs, and the calculated values of the first voltage V1 according to this embodiment when the wiring length L is 5 m, 10 m, 30 m, and 50 m. As can be seen from Figure 11, according to this embodiment, the error {= (V1 - V1') / V1'} is within the range of -7.7% to 3.4%, which shows that this is fully practical.

Next, we will explain how to find the evaluation function for calculating the second voltage V2.

Figure 12 is a diagram showing an example of a lightning surge entering the low-voltage wiring 10. The lightning surge that enters from one end of the low-voltage wiring 10 propagates through the low-voltage wiring 10 and reaches the other end. In the following explanation, the time when the head of the lightning surge reaches the other end is used as the reference, and t = 0. One end (distribution board side) is a short-circuited end, and the other end (load side) is an open end.

13 is a diagram showing an example of parameters used in an evaluation function for calculating the second voltage V2. As shown in FIG. 13, the wiring length (length from one end to the other end) of the low-voltage wiring 10 is L, the crest time of the lightning surge is tr, the propagation speed of the lightning surge is c, the round-trip time of the lightning surge is to, and the number of reflections is n. The round-trip time to of the lightning surge is the time required for the lightning surge to go back and forth between one end and the other end of the low-voltage wiring 10, and can be calculated as to=2L/c. The number of reflections represents the number of times that the lightning surge is reflected and repeatedly reaches the other end during the time from the time (t=0) when the head of the lightning surge reaches the other end to the time tr when the voltage at the other end reaches the crest value. The number of reflections n can be calculated as n=tr/to, and can be expressed as n=a.b. Here, a is the integer part, and b is the decimal part. The propagation speed c of a lightning surge is slightly slower than the speed of light, 3×10 ⁸ m/s. Specifically, if the relative dielectric constant of the insulator of a cable such as the low-voltage wiring 10 is ε and the relative magnetic permeability is 1, the propagation speed c of a lightning surge can be expressed as c=c0/√ε. c0 is the speed of light in a vacuum. Since the relative dielectric constant ε is ε>1, the propagation speed c of a lightning surge is slower than the speed of light. The value of the propagation speed c of a lightning surge may be stored in advance in the memory unit 53, or may be calculated using the relative dielectric constant of the low-voltage wiring 10 obtained via the operation unit 55.

Next, we will explain the second voltage V2 when a lightning surge that reaches the other end of the low-voltage wiring 10 is reflected at the other end, propagates through the low-voltage wiring 10, is reflected again at one end, reaches the other end again, and repeats reflections between one end and the other end of the low-voltage wiring 10.

Figure 14 is a diagram showing an example of the second voltage V2 when the number of reflections is 0. Figure 14A shows the reflection of a lightning surge, and Figure 14B shows the second voltage V2. As shown in Figure 14A, at t = 0, the lightning surge V1 reaches the other end and is reflected at the other end. Since the other end is an open end, no current flows, so no energy is absorbed and the voltage V1 of the same polarity returns through the low-voltage wiring 10. Therefore, the voltage at the other end is twice as high as V1. The voltage V1 propagating toward one end of the low-voltage wiring 10 reaches one end and is reflected at the one end. Since the one end is a short-circuited end, the voltage is forcibly set to 0. In order for the voltage to become 0, it is necessary to cancel out the propagated voltage V1, so a voltage of the opposite polarity -V1 is generated and propagates toward the other end as a reflected wave 1. The voltage propagating through the low-voltage wiring 10 is reflected as a voltage of the same polarity at the other end and as a voltage of the opposite polarity at the one end. The time t0 when reflected wave 1 reaches the other end is t0 = 2L/c.

As shown in FIG. 14B, the voltage V1 that arrives at t=0 rises to twice the voltage, becoming 2·V1 at the crest time tr. That is, the second voltage V2=2·V1. Because the number of reflections n is 0, the reflected wave does not arrive within the crest time, and the reflected wave 1 does not arrive at the other end at t=tr. That is, when the number of reflections is 0, to>tr. At t=to, a voltage of the opposite polarity, -V1, arrives, so the second voltage V2 at the other end drops after time to. As can be seen from FIG. 14B, the maximum value of the second voltage V2 is 2·V1. Therefore, when the number of reflections n (integer part a) is 0, the second voltage V2 can be calculated by the formula V2=2·V1.

Figure 15 is a diagram showing an example of the second voltage V2 when the number of reflections is 1. Since Figure 15A is similar to the case of Figure 14A, the explanation will be omitted. Since the number of reflections is 1, the reflected wave 1 reaches the other end once within the crest time. In other words, when the number of reflections is 1, to < tr. As shown in Figure 15B, the voltage V1 that arrives at t = 0 increases to twice the voltage. However, since the reflected wave 1 of the opposite polarity arrives before the second voltage V2 reaches voltage 2 · V1 (maximum value), the second voltage V2 becomes a constant voltage. When t = tr, the voltage V1 stops increasing, so the second voltage V2 decreases. As can be seen from Figure 15B, the maximum value of the second voltage V2 can be calculated by the formula V2 = 2 · V1 · to / tr.

Figure 16 shows an example of the second voltage V2 when the number of reflections is 2. Figure 16A is similar to the case of Figure 14A. Figure 16A shows reflected waves 1, 2, and 3. The reflected wave has the opposite polarity at one end, and the reflected wave remains the same polarity at the other end. Therefore, reflected wave 1 is reflected once at one end, so it is -V1. Reflected wave 2 is reflected twice at one end, so it is V1. Reflected wave 3 is reflected three times at one end, so it is -V1. In other words, if the number of reflections is odd, it will have the opposite polarity of the reflected wave, and if the number of reflections is even, it will have the same polarity as the reflected wave.

As shown in FIG. 16B, the number of reflections is 2, so the reflected wave arrives at the other end twice (reflected waves 1 and 2) within the crest time. In other words, when the number of reflections is 2, 2·to<tr. As in the case of FIG. 15B, the voltage V1 that arrives at t=0 increases to twice the voltage. However, at time t0 before the second voltage V2 reaches voltage 2·V1 (maximum value), reflected wave 1 of the opposite polarity arrives, so the second voltage V2 becomes a constant voltage. At time 2·to, reflected wave 2 of the same polarity arrives, so the second voltage V2 rises again. When t=tr, the rise in voltage V1 stops, so the second voltage V2 becomes constant.

If the number of reflections n is expressed as n = a.b, then a = 2. From FIG. 16B, the time difference Δt between time tr and time 2·to can be expressed as Δt = 0.b × to. Therefore, the increase ΔV2 in the second voltage V2 from time 2·to to time tr can be expressed as ΔV2 = 2·V1 × 0.b × to/tr. Since the second voltage from time to to time 2·to is 2·V1·to/tr, the maximum value of the second voltage V2 can be calculated by the formula V2 = 2·V1·to·(1.b)/tr.

Figure 17 is a diagram showing an example of the second voltage V2 when the number of reflections is 3. Figure 17A is the same as the case of Figure 16A. As shown in Figure 17B, since the number of reflections is 3, the reflected wave reaches the other end three times (reflected waves 1, 2, and 3) within the crest time. In other words, when the number of reflections is 3, 3·to<tr. As in the case of Figure 16B, the voltage V1 that arrives at t=0 becomes twice as high and rises. However, at time t0 before the second voltage V2 becomes voltage 2·V1 (maximum value), the reflected wave 1 of the opposite polarity arrives, so the second voltage V2 becomes a constant voltage. Also, at time 2·to, the reflected wave 2 of the same polarity arrives, so the second voltage V2 rises again. Furthermore, at time 3·to, the reflected wave 3 of the opposite polarity arrives, so the second voltage V2 becomes constant. When t=tr, the voltage V1 no longer rises, so the second voltage V2 drops due to the influence of the reflected wave 3. The second voltage from time to to time 2·to is 2·V1·to/tr, and the increase in the second voltage from time 2·to to time 3·to is also 2·V1·to/tr, so the maximum value of the second voltage V2 can be calculated using the formula V2 = 2·V1·to·2/tr.

As described above, when an odd-numbered reflected wave reaches the other end, the second voltage V2 becomes a constant value from that point onward, and when an even-numbered reflected wave arrives, the second voltage V2 increases from that point onward. In other words, the state of the second voltage differs depending on whether the number of reflections is odd or even.

Figure 18 shows the evaluation function for calculating the second voltage V2. The number of reflections n is expressed as n = a.b. Here, a indicates the integer part and b indicates the decimal part. When a is an odd number, the coefficient A is defined as A = (a + 1)/b, and when a is an even number, the coefficient A is defined as A = (a/2) + b. When a = 0, the second voltage V2 can be calculated using the formula V2 = 2 · V1, and when a ≥ 1, the second voltage V2 can be calculated using the formula V2 = {2 · V1 · to/tr} · A.

As described above, the reflection count calculation unit 59 calculates the reflection count, which indicates the number of times that a lightning surge that reaches the other end of the low-voltage wiring 10 from one end is repeatedly reflected between the one end and the other end, and reaches the other end again within the time until the voltage at the other end reaches the peak value. The second voltage calculation unit 58 can calculate the second voltage based on the reflection count calculated by the reflection count calculation unit 59. Since the state of the overvoltage at the end differs depending on the reflection count of the reflected wave, an actual overvoltage situation can be reproduced by taking the reflection count into consideration.

The second voltage calculation unit 58 can calculate the second voltage using a different formula depending on whether the number of reflections calculated by the reflection count calculation unit 59 is an even number or an odd number. Since the state of the overvoltage at the terminal differs depending on whether the number of reflections is an even number or an odd number, the actual overvoltage situation can be reproduced by taking into account whether the number of reflections is an even number or an odd number.

As described above, specifically, when the number of reflections is 0, the second voltage calculation unit 58 can calculate the second voltage V2 by the formula (2 x V1). Here, V1 is the first voltage which is the overvoltage at one end. Also, when the number of reflections is 1 or more, the second voltage calculation unit 58 can calculate the second voltage V2 by the formula (2 x V1 x t0 x A/tr). Here, V1 is the first voltage which is the overvoltage at one end, to is the round trip time of the lightning surge between one end and the other end of the low-voltage wiring 10, tr is the crest time of the lightning surge, A is A = (a + 1) / 2 when the integer part a of the number of reflections is odd, and A = b + a / 2 when the integer part a is even, and b is the decimal part of the number of reflections.

As described above, it is possible to easily evaluate the voltage generated at the end of the low-voltage wiring 10 connected later from the distribution board 20 due to a lightning surge.

Figure 19 shows an example of the evaluation of the second voltage V2 according to this embodiment. Figure 19 shows the calculated values of overvoltages V1' and V2' by EMTP when the crest time tr is 0.25 μs, 1.2 μs, and 10 μs, and the calculated value of the second voltage V2 according to this embodiment when the wiring length L is 5 m, 10 m, 30 m, and 50 m. As can be seen from Figure 19, according to this embodiment, the error {= (V2 - V2') / V2'} is within the range of -11.6% to 4.9%, which shows that this is fully practical.

Figure 20 shows an example of an EMTP analysis. Figure 20 shows the waveform of overvoltage V2' by EMTP analysis when the crest time/tail time of the lightning surge waveform are 0.25/100 μs, 1.2/50 μs, and 10/350 μs, respectively. Overvoltage V2' is shown when the VVF cable length is 5 m, 10 m, 30 m, and 50 m, respectively. The peak value of each waveform shown in Figure 20 represents the calculated value of overvoltage V2' by EMTP in Figure 19.

To further improve the accuracy of the second voltage V2, the increase or decrease of the lightning surge at the installation location of the SPD 30 (one end of the low-voltage wiring 10) and at the load end (the other end of the low-voltage wiring 10) may be taken into consideration. If the reflection coefficients at one end and the other end are α1 and α2, respectively, when a = 0, V2 may be calculated using the formula V2 = {α1 α2} 2 V1, and when a ≥ 1, V2 may be calculated using the formula V2 = {α1 α2} 2 V1 to/tr} A. In addition, to estimate on the safe side, the second voltage V2 may be estimated higher by calculating V2 = β2 V2, where β2 > 1.

Second Embodiment
In the first embodiment, a case where a lightning surge enters the low-voltage wiring 10 from a building (building structure) via a ground wire is described. In the second embodiment, a case where a lightning surge enters the low-voltage wiring 10 via a power line (electrical path) is described.

Figure 21 is a diagram showing an example of an analysis circuit for electrical equipment constructed in the second embodiment. The difference from the first embodiment shown in Figure 2 is that the position of the voltage source Vg that simulates the lightning surge waveform is connected to the power line L instead of the ground line. The ground resistance for type D grounding is represented by R, the resistance of the ground line is represented by Rd, and the inductance of the ground line is represented by Ld. The SPD-related inductance Ls can be expressed as Ls = Lg + Le + Lf, as in the case of Figure 2. In addition, the crest time / tail time for the lightning surge was set to 1.2 / 50 μs and 8 / 20 μs. The peak value was set to 30 kV. The other configurations of the analysis circuit and the numerical values of the circuit elements are the same as those of the first embodiment.

Figure 22 is a diagram showing an example of evaluation of the second voltage V2 according to the second embodiment. Figure 22 shows the calculated values of overvoltage V2' by EMTP when the crest time tr is 1.2 μs and 8 μs, and the calculated values of the second voltage V2 according to this embodiment when the wiring length L is 5 m and 150 m. As can be seen from Figure 22, according to this embodiment, the error {= (V2 - V2') / V2'} is within the range of -7.3% to 8.3%, which shows that this is fully practical.

Figure 23 is a diagram showing an example of an EMTP analysis of the second embodiment. Figure 23 shows the waveform of overvoltage V2' obtained by EMTP analysis when the crest time/tail time of the lightning surge waveform are 1.2/50 μs and 8/20 μs, respectively. The overvoltage V2' is shown when the VVF cable length is 5 m, 10 m, 100 m, and 150 m, respectively. The peak value of each waveform shown in Figure 23 represents the calculated value of overvoltage V2' by EMTP in Figure 22.

As described above, the evaluation function illustrated in FIG. 18 can be used in the second embodiment. Also, the evaluation function illustrated in FIG. 11 can be used in the second embodiment.

Third Embodiment
Next, a description will be given of the protection range of the SPD 30. The protection range described below is applicable to both the first and second embodiments.

Figure 24 is a diagram showing an example of the protection range of SPD 30. The method of identifying the protection range can be divided into, for example, three cases depending on the conditions. First, when first voltage V1 ≧ device withstand voltage Vm, the voltage V1 (overvoltage) at the location where SPD 30 is installed is equal to or higher than the device withstand voltage Vm, so it is necessary to reselect an SPD to lower voltage V1.

When 2·V1<Vm, the maximum value (2·V1) of the second voltage V2 at the end where the device is installed does not exceed the withstand voltage Vm of the device, so the length of the low-voltage wiring 10 between the SPD 30 and the device can be set to the required length without any restrictions.

If the two conditions mentioned above are not met, i.e., Vm/2≦V1<Vm, there are two ways to specify the range of protection of the SPD 30. The first method specifies the protection range of the SPD 30 by selecting the wiring length so that the voltage V2 (overvoltage) at the location where the device is installed does not exceed the withstand voltage Vm of the device. The second method specifies the protection range (wiring length) of the SPD in the case of one reflection and in the case of multiple reflections, and the shorter distance is set as the protection range of the SPD. The first and second methods are explained below using specific examples.

25 is a diagram showing a first method for identifying the protection range of the SPD 30. As parameters, the crest time tr of the lightning surge is 1 μs, the first voltage V1 is 2.2 kV, the propagation speed c of the lightning surge is 2.8×10 ⁸ m/s, and the withstand voltage Vm of the device is 2.5 kV. The wiring length L, which is the length from one end of the low-voltage wiring 10 to the other end, is 5 m. The number of reflections n is tr/to=tr/(2L/c)=28. That is, a=28, b=0. Since the number of reflections is an even number, A=(a/2)+b=14. The second voltage V2 is V2={2·V1·to/tr}·A=2.2 kV.

If the wiring length L is 15 m, the number of reflections n is 9.33, so a = 9, b = 0.33. Since the number of reflections is odd, A = (a + 1)/2 = 5. The second voltage V2 is V2 = {2 V1 to/tr} A = 2.35 kV. If the wiring length L is 20 m, the number of reflections n is 7, so a = 7, b = 0. Since the number of reflections is odd, A = (a + 1)/2 = 4. The second voltage V2 is V2 = {2 V1 to/tr} A = 2.51 kV.

The longest wiring length in the range where the second voltage V2 does not exceed the withstand voltage Vm of the device is when the wiring length L = 15 m, so the protection range of the SPD 30 can be specified as 15 m. Note that in the example of FIG. 25, wiring lengths of 5 m, 15 m, and 20 m are considered, but the selection of the wiring length is not limited to this, and an appropriate length can be considered, for example, in increments of 1 m, 2 m, 5 m, or 10 m. In addition, when the protection range is specified by the information processing device 50, a lower limit or upper limit of the wiring length can be set in advance, and the user can gradually change the wiring length using a desired increment from the set lower limit or upper limit to search for the protection range.

As described above, the protection range determination unit 60 can identify the wiring length that can be protected by the SPD 30 by comparing the second voltage V2 for each of the multiple wiring lengths of the low-voltage wiring 10 calculated by the second voltage calculation unit 58 with the withstand voltage Vm of the device connected to the other end.

In an analysis using EMTP, it is not possible to output the range (wiring length) that the SPD can protect as a solution, but according to this embodiment, the protection range of the SPD 30 can be easily identified.

Figure 26 is a diagram showing a second method for identifying the protection range of SPD 30. The parameters are the same as those of the first method in Figure 25. When the number of reflections is one, the second voltage V2 is V2 = 2 V1 to/tr. The wiring length L1 for Vm > V2 is L1 < Vm c tr/(4 V1), and L1 = 79.5 m. When the number of reflections is two or more, the second voltage V2 is V2 = {2 V1 to/tr} A. Assuming that the number of reflections is an odd number, A = (a + 1)/2 can be approximated by (n + 1)/2, and the wiring length L2 for Vm > V2 is L2 < {(Vm/V1) - 1} c tr/2, and L2 = 19.1 m. The shorter of L1 and L2 can be set as the protection range, and the protection range of SPD30 can be specified as 19.1 m.

As described above, the protection range specification unit 60 has the functions of a first wiring length calculation unit and a second wiring length calculation unit, and calculates the first wiring length L1 at which the second voltage calculated by the second voltage calculation unit 58 is equal to or less than the withstand voltage Vm of the device connected to the other end when the number of reflections is one, and calculates the second wiring length L2 at which the second voltage calculated by the second voltage calculation unit 58 is equal to or less than the withstand voltage Vm when the number of reflections is multiple. The protection range specification unit 60 can specify the shorter of the calculated first wiring length L1 and second wiring length L2 as the wiring length that can be protected by the SPD 30.

In an analysis using EMTP, it is not possible to output the range (wiring length) that the SPD can protect as a solution, but according to this embodiment, the protection range of the SPD 30 can be easily identified.

Figure 27 is a flowchart showing the procedure for the calculation process of the first voltage V1 by the information processing device 50. For convenience, the following description will be given with the control unit 51 as the main part of the process. The control unit 51 acquires the parameter values of each parameter, namely, the discharge start voltage Vf of the SPD 30, the limit voltage Vs of the SPD 30, the SPD-related inductance Ls, the crest time tr of the lightning surge, the peak value I of the lightning surge current flowing through the SPD 30, and the withstand voltage Vm of the device (S11).

The control unit 51 determines whether or not |Vf|>|Ls·dI/dt| (S12). Here, dI/dt may be calculated using the formula (I/tr). If |Vf|>|Ls·dI/dt| (YES in S12), the control unit 51 calculates the first voltage V1 using the formula V1=Vf (S13) and determines whether or not Vm≧V1 (S14).

If Vm≧V1 (YES in S14), the control unit 51 ends the process, and if Vm≧V1 is not true (NO in S14), the control unit 51 notifies the user of the need to reselect the SPD (S15) and ends the process. The notification of the need may be displayed on the display panel 54 or output as audio. The notification may also be sent to an external device via the communication unit 52.

If |Vf|>|Ls·dI/dt| is not satisfied (NO in S12), the control unit 51 selects a correction coefficient B according to the crest time tr (S16), calculates the first voltage V1 using the formula V1=Vs+B·Ls·dI/dt (S17), and determines whether Vm≧V1 is satisfied (S18).

If Vm≧V1 (YES in S18), the control unit 51 ends the process, and if Vm≧V1 is not true (NO in S18), the control unit 51 notifies the user of the need to reduce the SPD-related inductance (S19) and ends the process. The notification of the need may be displayed on the display panel 54 or output as audio. The notification may also be sent to an external device via the communication unit 52. The notification content may be created in advance and stored in the memory unit 53.

Figure 28 is a flowchart showing the procedure of the calculation process of the second voltage V2 by the information processing device 50. The control unit 51 acquires the parameter values of each parameter, namely, the wiring length L of the low-voltage wiring 10, the crest time tr of the lightning surge, and the first voltage V1 which is the overvoltage at one end of the low-voltage wiring 10 (S31). The first voltage V1 may be a value input by the user, or may be a voltage calculated by the first voltage calculation unit 57.

The control unit 51 calculates the round trip time to of the lightning surge (S32). The round trip time to can be calculated using the formula 2L/c, where c is the propagation speed of the lightning surge. The control unit 51 calculates the number of reflections n of the reflected wave = a. b (S33). The number of reflections n can be calculated using the formula tr/to = tr/(2L/c). The control unit 51 determines whether the integer part a of the number of reflections n is 0 or not (S34), and if a = 0 (YES in S34), calculates the second voltage V2 using the formula V2 = 2 · V1 (S35), and performs the processing of step S40 described below.

If a is not 0 (NO in S34), the control unit 51 judges whether the integer part a is even or odd (S36). If a is even (even in S36), the control unit 51 calculates the coefficient A using the formula A = (a/2) + b (S37), calculates the second voltage V2 using the formula V2 = {2 V1 to/tr} A (S38), and performs the process of step S40 described below. If a is odd (odd in S36), the control unit 51 calculates the coefficient A using the formula A = (a + 1)/2 (S39), and performs the process of step S38.

The control unit 51 determines whether the withstand voltage of the device is Vm≧V2 (S40), and if Vm≧V (YES in S40), notifies that an SPD is not required at the load end (S41) and ends the process. If Vm≧V is not true (NO in S40), the control unit 51 notifies that an SPD is required at the load end (S42) and ends the process. The notification may be displayed on the display panel 54 or output as a sound. The notification may also be sent to an external device via the communication unit 52. The notification content may be created in advance and stored in the memory unit 53.

Figure 29 is a flowchart showing the processing steps of the first method of identifying the protection range by the information processing device 50. The control unit 51 acquires the parameter values of each parameter, namely, the crest time tr of the lightning surge, the first voltage V1, and the withstand voltage Vm of the device (S51). The first voltage V1 may be a value input by the user, or may be a voltage calculated by the first voltage calculation unit 57. The control unit 51 sets the counter N=1 (S52), and selects the wiring length L of the low-voltage wiring 10 by the formula L=α·N (S53). α is a step size for changing the wiring length that can be freely set by the user.

The control unit 51 calculates the round trip time to of the lightning surge (S54). The round trip time to can be calculated using the formula 2L/c, where c is the propagation speed of the lightning surge. The control unit 51 calculates the number of reflections n of the reflected wave = a. b (S55). The number of reflections n can be calculated using the formula tr/to = tr/(2L/c). The control unit 51 determines whether the integer part a of the number of reflections n is 0 or not (S56), and if a = 0 (YES in S56), calculates the second voltage V2 using the formula V2 = 2 · V1 (S57), and performs the processing of step S62 described below.

If a is not 0 (NO in S56), the control unit 51 judges whether the integer part a is even or odd (S58). If a is odd (odd in S58), the control unit 51 calculates the coefficient A using the formula A = (a + 1)/2 (S59), calculates the second voltage V2 using the formula V2 = {2 V1 to/tr} A (S60), and performs the process of step S62 described below. If a is even (even in S58), the control unit 51 calculates the coefficient A using the formula A = (a/2) + b (S61), and performs the process of step S60.

The control unit 51 determines whether the second voltage V2 is equal to or greater than the withstand voltage Vm of the device (S62), and if V2 is not equal to or greater than Vm (NO in S62), it increments the counter N by 1 (S63) and repeats the process from step S53 onwards. If V2 is equal to or greater than Vm (YES in S62), the control unit 51 sets the protection range of the SPD 30 to L = α (N-1) (S64) and ends the process.

Figure 30 is a flowchart showing the processing steps of the second method of identifying the protection range by the information processing device 50. The control unit 51 acquires the parameter values of each parameter, namely, the crest time tr of the lightning surge, the first voltage V1, and the withstand voltage Vm of the device (S71). The first voltage V1 may be a value input by the user, or may be a voltage calculated by the first voltage calculation unit 57. The control unit 51 calculates the first wiring length L1 by the formula L1 = Vm c tr / (4 V1) (S72).

The control unit 51 calculates the second wiring length L2 using the formula L2 = {(Vm/V1) - 1} c tr/2 (S73). The control unit 51 determines whether L1 < L2 (S74), and if L1 < L2 (YES in S74), sets the protection range of SPD 30 to L1 (S75) and ends the process. If L1 < L2 is not true (NO in S74), the control unit 51 sets the protection range of SPD 30 to L2 (S76) and ends the process.

29 and 30 assume that the condition Vm/2≦V1<Vm is satisfied. If V1≧Vm, the overvoltage at the location where the SPD 30 is installed is greater than the withstand voltage of the device, so a notification such as "You need to reselect the SPD or reconsider the length of the grounding wire" may be issued. If 2·V1<Vm, the maximum value of the second voltage V2 at the end where the device is installed does not exceed the withstand voltage Vm of the device, so a notification such as "The length of the low-voltage wiring between the SPD and the device can be set to the required length" may be issued.

The information processing device 50 can also be realized by using a computer equipped with a CPU (processor), RAM, etc. A computer program (which can be recorded on a recording medium) that defines the processing procedures as shown in Figures 27 to 30 is loaded into the RAM equipped in the computer, and the computer program (app) is executed by the CPU (processor), thereby realizing the information processing device 50 on the computer.

The information processing device 50 has a function as a display device. For example, a user can input a parameter value to the information processing device 50 or select a desired parameter value from among multiple parameter values and set the parameter value, whereby the information processing device 50 can display the processing result.

Figure 31 is a diagram showing an example of an overvoltage calculation screen 110 for an SPD installation location. As shown in Figure 31, the user can input or set the following parameter values: lightning surge current crest value I, crest time tr, SPD limit voltage Vs, SPD discharge start voltage Vf, SPD-related inductance Ls, and device withstand voltage Vm. By operating the "Clear" icon, the parameter values can be cleared, and the desired parameter values can be input or set again. By operating the "Calculate" icon, the information processing device 50 calculates the first voltage V1 using the input or set parameter values, and the calculation result is displayed.

The evaluation content is notified according to the calculation result of the first voltage V1. The evaluation content can provide countermeasures such as, for example, "The overvoltage at the SPD installation location exceeds the withstand voltage of the load, and it is necessary to reselect the SPD or reduce the inductance of the grounding wire." This not only lets the user know that the overvoltage caused by lightning exceeds the withstand voltage of the equipment, but also tells which components of the electrical equipment to focus on (e.g., the impedance of the grounding wire, the SPD) and how to redesign the electrical equipment. The evaluation content is not limited to this.

Figure 32 is a diagram showing an example of an overvoltage calculation screen 120 at a load installation location. As shown in Figure 32, the user can input or set the following parameter values: the crest time tr of the lightning surge, the wiring length L of the low-voltage wiring 10, and the voltage (overvoltage) V1 at the SPD installation location. In addition, detailed parameters may be set by operating a "detailed parameter setting" icon. The detailed parameters may include, for example, the relative dielectric constant of the low-voltage wiring 10, the reflection coefficient α1 on the SPD side, the reflection coefficient α2 on the load side, and a safety factor β2 against overvoltage. When the "calculation" icon is operated, the information processing device 50 calculates the second voltage V2 using the input or set parameter values, and the calculation result is displayed.

The evaluation content is notified according to the calculation result of the second voltage V2. The evaluation content can provide a countermeasure, such as, for example, "An SPD is required at the end of the cable" or "An SPD is not required at the end of the cable." Note that the evaluation content is not limited to this.

As described above, the information processing device 50 can display a reception screen for accepting the setting of parameters including the crest time tr of the lightning surge, the first voltage V1 generated by the lightning surge at one end of the low-voltage wiring 10 to which the SPD 30 is connected, and the wiring length L from one end of the low-voltage wiring 10 to the other end, and can display the second voltage V2 at the other end calculated based on the parameters set on the reception screen. The information processing device 50 can also display a reception screen for accepting the setting of the withstand voltage Vm of the device connected to the other end, and can display the result of the determination of whether or not an SPD is required at the other end, determined based on the withstand voltage set on the reception screen.

This not only lets users know that lightning-induced overvoltages exceed the withstand voltage of equipment, but also tells them which components of electrical equipment (e.g., SPDs) to focus on and how to redesign the electrical equipment.

Figure 33 is a diagram showing an example of an SPD protection range calculation screen 130. As shown in Figure 33, the user can input or set the following parameter values: the crest time tr of the lightning surge, the withstand voltage Vm of the device, and the voltage (overvoltage) V1 at the SPD installation location. When the "Calculation" icon is operated, the information processing device 50 uses the input or set parameter values to identify the protection range of the SPD and displays the results. The evaluation content can be, for example, "It is necessary to reselect the SPD or reconsider the grounding line length," or "The wiring length of the low-voltage wiring between the SPD and the device can be the required length (there is no limit on the cable length)."

As described above, the information processing device 50 can display a reception screen that accepts the setting of parameters including the crest time tr of the lightning surge, the first voltage V1 generated by the lightning surge at one end of the low-voltage wiring 10 to which the SPD 30 is connected, and the withstand voltage Vm of the device connected to the other end of the low-voltage wiring 10, and can display the wiring length that can be protected by the SPD, identified based on the parameters set on the reception screen.

This allows the user to obtain the range (cable length) that the SPD 30 can protect by simply inputting or setting parameters.

According to this embodiment, it is possible to calculate the overvoltage at the location where the SPD is installed in the distribution board and the overvoltage at the end of the low-voltage wiring laid out from the distribution board when a lightning surge enters, in a simple manner without using complex numerical analysis methods, and with accuracy within a practically acceptable error range compared to numerical analysis methods. Also, according to this embodiment, it is possible to determine the protection range of the SPD in a simple manner, which is not possible to obtain using numerical analysis methods. Furthermore, according to this embodiment, it is possible to know which components of the electrical equipment should be focused on as a countermeasure against lightning surges, and to know how to redesign the electrical equipment.

The information processing device of this embodiment is an information processing device that calculates the voltage at one end of a wiring to which a lightning arrester is connected, and includes a first acquisition unit that acquires first parameters including the crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and the wiring length from the one end to the other end, and a second voltage calculation unit that calculates a second voltage at the other end based on the first parameters acquired by the first acquisition unit.

The information processing device of this embodiment includes a second acquisition unit that acquires second parameters including the discharge start voltage of the lightning arrester, the limit voltage of the lightning arrester, the associated inductance of the lightning arrester including the inductance of the grounding wire of the lightning arrester, and the peak value of the surge current flowing through the lightning arrester due to the lightning surge, and a first voltage calculation unit that calculates the first voltage based on the second parameters acquired by the second acquisition unit, and the first acquisition unit acquires the first voltage calculated by the first voltage calculation unit.

In the information processing device of this embodiment, the first voltage calculation unit calculates the first voltage using different calculation formulas depending on the magnitude of the time change of the surge current and the multiplication value of the associated inductance, and the discharge start voltage of the lightning arrester.

In the information processing device of this embodiment, the first voltage calculation unit calculates the first voltage using a correction coefficient according to the crest time of the lightning surge.

The information processing device of this embodiment includes a reflection count calculation unit that calculates the number of reflections indicating the number of times that a lightning surge that has reached the other end from one end is repeatedly reflected between the one end and the other end and reaches the other end again within the time until the voltage at the other end reaches a peak value, and the second voltage calculation unit calculates a second voltage based on the reflection count calculated by the reflection count calculation unit.

In the information processing device of this embodiment, the second voltage calculation unit calculates the second voltage using a different formula depending on whether the number of reflections calculated by the reflection number calculation unit is an even number or an odd number.

In the information processing device of this embodiment, when the number of reflections is 0, the second voltage calculation unit calculates the second voltage by the formula (2 x V1), where V1 is the first voltage.

In the information processing device of this embodiment, when the number of reflections is 1 or more, the second voltage calculation unit calculates the second voltage by the formula (2 x V1 x t0 x A/tr), where V1 is the first voltage, to is the round trip time of the lightning surge between one end of the wiring and the other end, tr is the crest time of the lightning surge, and A is A = (a + 1)/2 when the integer part a of the number of reflections is odd, and A = b + a/2 when the integer part a is even, and b is the decimal part of the number of reflections.

The information processing device of this embodiment includes a first wiring length calculation unit that calculates a first wiring length at which the second voltage calculated by the second voltage calculation unit is equal to or less than the withstand voltage of the device connected to the other end when the number of reflections is one, a second wiring length calculation unit that calculates a second wiring length at which the second voltage calculated by the second voltage calculation unit is equal to or less than the withstand voltage when the number of reflections is multiple, and an identification unit that identifies the shorter of the first wiring length and the second wiring length as the wiring length that can be protected by the lightning arrester.

The information processing device of this embodiment includes a determination unit that compares the second voltage calculated by the second voltage calculation unit for each of the multiple wiring lengths of the wiring with the withstand voltage of the device connected to the other end to determine the wiring length that can be protected by the lightning arrester.

The information processing device of this embodiment includes a determination unit that determines whether or not a lightning arrester is required at the other end based on the second voltage calculated by the second voltage calculation unit.

The information processing method of this embodiment is an information processing method for calculating the voltage at one end of a wiring to which a lightning arrester is connected, and obtains first parameters including the crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and the wiring length from the one end to the other end, and calculates a second voltage at the other end based on the obtained first parameters.

The computer program of this embodiment is a computer program that calculates the voltage at one end of a wiring to which a lightning arrester is connected, and causes a computer to execute a process of acquiring first parameters including the crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and the wiring length from the one end to the other end, and calculating a second voltage at the other end based on the acquired first parameters.

The display method of this embodiment displays a reception screen that accepts the setting of parameters including the crest time of the lightning surge, a first voltage generated by the lightning surge at one end of the wiring to which the lightning arrester is connected, and the wiring length from the one end to the other end of the wiring, and displays a second voltage at the other end calculated based on the parameters set on the reception screen.

The display method of this embodiment displays a reception screen that accepts the setting of the withstand voltage of the device connected to the other end, and displays the result of the determination of whether or not a lightning arrester is required at the other end, based on the withstand voltage set on the reception screen.

The display method of this embodiment displays a reception screen that accepts the setting of parameters including the crest time of a lightning surge, a first voltage generated by the lightning surge at one end of the wiring to which the lightning arrester is connected, and the withstand voltage of the device connected to the other end of the wiring, and displays the wiring length that can be protected by the lightning arrester, which is identified based on the parameters set on the reception screen.

10 Low voltage wiring 20 Distribution board 30 SPD
40 Load 50 Information processing device 51 Control unit 52 Communication unit 53 Storage unit 54 Display panel 55 Operation unit 56 Display processing unit 57 First voltage calculation unit 58 Second voltage calculation unit 59 Reflection count calculation unit 60 Protection range specification unit 61 Necessity determination unit

Claims (16)

An information processing device for calculating a voltage at one end of a wiring having a lightning arrester connected to the other end,
A first acquisition unit that acquires first parameters including a crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and a wiring length from the one end to the other end;
and a second voltage calculation unit that calculates a second voltage at the other end based on the first parameter acquired by the first acquisition unit.
Information processing device. a second acquisition unit that acquires second parameters including a discharge start voltage of the lightning arrester, a limit voltage of the lightning arrester, a related inductance of the lightning arrester including an inductance of a ground wire of the lightning arrester, and a peak value of a surge current flowing through the lightning arrester due to the lightning surge;
a first voltage calculation unit that calculates the first voltage based on the second parameter acquired by the second acquisition unit,
The first acquisition unit is
acquiring the first voltage calculated by the first voltage calculation unit;
The information processing device according to claim 1 . The first voltage calculation unit
Calculating a first voltage using different calculation formulas depending on the magnitude of the multiplication value of the time change of the surge current and the related inductance and the discharge start voltage of the lightning arrester.
The information processing device according to claim 2 . The first voltage calculation unit
Calculating the first voltage using a correction coefficient according to the crest time of the lightning surge;
4. The information processing device according to claim 2. a reflection count calculation unit that calculates a reflection count indicating the number of times that a lightning surge that has reached the other end from the one end is repeatedly reflected between the one end and the other end and reaches the other end again within a time until a voltage at the other end reaches a peak value;
The second voltage calculation unit
calculating a second voltage based on the number of reflections calculated by the number-of-reflection calculation unit;
The information processing device according to claim 1 . The second voltage calculation unit
calculating a second voltage using a different arithmetic expression depending on whether the number of reflections calculated by the number of reflections calculation unit is an even number or an odd number;
The information processing device according to claim 5 . The second voltage calculation unit
When the number of reflections is 0, the second voltage is calculated by the formula (2×V1).
Here, V1 is the first voltage.
7. The information processing device according to claim 5 or 6. The second voltage calculation unit
When the number of reflections is 1 or more, the second voltage is calculated by the formula (2×V1×t0×A/tr).
Here, V1 is the first voltage, to is the round trip time of the lightning surge between one end and the other end of the wiring, tr is the crest time of the lightning surge, A is A=(a+1)/2 when the integer part a of the number of reflections is an odd number, and A=b+a/2 when the integer part a is an even number, and b is the decimal part of the number of reflections.
7. The information processing device according to claim 5 or 6. a first wiring length calculation unit that calculates a first wiring length such that the second voltage calculated by the second voltage calculation unit is equal to or less than a withstand voltage of a device connected to the other end when the number of reflections is one;
a second wiring length calculation unit that calculates a second wiring length at which the second voltage calculated by the second voltage calculation unit is equal to or less than the withstand voltage when the number of reflections is a plurality of times;
and a determination unit that determines a shorter wiring length of the first wiring length and the second wiring length as a wiring length that can be protected by the lightning arrester.
The information processing device according to claim 5 . and a determination unit that compares a second voltage calculated by the second voltage calculation unit for each of the plurality of wiring lengths of the wiring with a withstand voltage of a device connected to the other end, to determine a wiring length that can be protected by the lightning arrester.
The information processing device according to claim 1 . a determination unit that determines whether or not a lightning arrester is required at the other end based on the second voltage calculated by the second voltage calculation unit;
The information processing device according to claim 1 . An information processing method for calculating a voltage at one end of a wiring having a lightning arrester connected to the other end, comprising:
Obtaining first parameters including a crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and a wiring length from the one end to the other end;
Calculating a second voltage at the other end based on the acquired first parameter.
Information processing methods. A computer program for calculating a voltage at one end of a wiring having a lightning arrester connected to the other end,
On the computer,
Obtaining first parameters including a crest time of a lightning surge, a first voltage generated at the one end by the lightning surge, and a wiring length from the one end to the other end;
Calculating a second voltage at the other end based on the acquired first parameter.
A computer program that executes a process. displaying a reception screen for receiving settings of parameters including a crest time of a lightning surge, a first voltage generated at one end of a wiring to which a lightning arrester is connected by the lightning surge, and a wiring length from the one end to the other end of the wiring;
displaying the second voltage at the other end calculated based on the parameters set on the reception screen;
Display method. displaying a reception screen for receiving a setting of a withstand voltage of a device to be connected to the other end;
displaying a result of a determination as to whether or not a lightning arrester is required at the other end, the determination being based on the withstand voltage set on the reception screen;
The display method according to claim 14. displaying a reception screen for receiving settings of parameters including a crest time of the lightning surge, a first voltage generated by the lightning surge at one end of a wiring to which the lightning arrester is connected, and a withstand voltage of a device connected to the other end of the wiring;
displaying the wiring length that can be protected by the lightning arrester, which is specified based on the parameters set on the reception screen;
Display method.

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