Lightning protection device and lightning protection method

Abstract

A lightning protection device for protecting a DC power supply device from a lightning surge current, the lightning protection device comprising a positive-electrode-side lightning arrester connected between a positive-electrode-side power supply cable of the DC power supply device and a ground point and a negative-electrode-side lightning arrester connected between a negative-electrode-side power supply cable of the DC power supply device and the ground point, wherein a difference in operating voltage between the positive-electrode-side lightning arrester and the negative-electrode-side lightning arrester is set equal to or larger than a reference value.

Description

Technical Field

[0001] The present invention relates to a lightning protection device and a lightning protection method.

Background Art

[0002] Measures have been developed for the case where a lightning surge enters a power supply device due to a lightning strike. As a countermeasure against lightning surges in a DC power supply device (for example, a DC / DC converter), it is known to install an SPD (Surge protective device) such as a zinc oxide varistor (hereinafter referred to as a varistor) on the output side (where the lightning surge enters) of the DC power supply device. For example, by installing the varistor in Non-Patent Document 1 between the positive electrode of the DC power supply device and the ground, and between the negative electrode and the ground, it is possible to let the lightning surge that has entered from the cable escape to the ground through the varistor.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] DC power supply devices have the following problems. In the internal circuitry of a DC power supply device, as a countermeasure against lightning surges entering from the output side of the DC power supply device, varistors are installed between the positive terminal and ground and between the negative terminal and ground on the output side of the DC power supply device. This allows lightning surges that enter the positive terminal side, lightning surges that enter the negative terminal side, or lightning surges that enter both the positive and negative terminals simultaneously to be discharged to ground. However, if there is an electronic element or electronic circuit that has the effect of rectifying the current, such as a diode, which causes current to flow in only one direction, the varistor installed between the negative terminal and ground will not operate, the lightning surge that entered the negative terminal side will flow to the positive terminal side through the diode, the varistor installed between the positive terminal and ground will operate, and the lightning surge that entered the negative terminal side will flow to ground. In this case, there is a problem that the diode may be destroyed by the lightning surge current, causing the device to malfunction.

[0005] The disclosed technology aims to properly dissipate lightning surges to earth, even when there are rectifying electronic elements or circuits between the lines of a DC power supply device. [Means for solving the problem]

[0006] The disclosed technology is a lightning protection device for protecting a DC power supply device from lightning surge currents, A positive-side surge arrester is connected between the positive-side power cable of the DC power supply device and the ground point. The DC power supply device includes a negative-side surge arrester connected between the negative-side power cable and the ground point, The operating voltage of the positive-side surge arrester is higher than the operating voltage of the negative-side surge arrester. The difference in operating voltage between the positive-side surge arrester and the negative-side surge arrester is greater than or equal to a reference value, and an electronic element or electronic circuit having a rectifying effect is provided between the positive-side power cable and the negative-side power cable. It is a lightning protection device. [Effects of the Invention]

[0007] Even if there are rectifying electronic elements or circuits between the lines of a DC power supply device, lightning surges can still be properly discharged to ground. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of the configuration of a conventional lightning protection device. [Figure 2] This diagram illustrates what happens when a lightning surge enters a DC power supply device that includes an electronic element or circuit with rectifying properties. [Figure 3] This diagram illustrates the case where a lightning surge enters only the positive terminal side of a DC power supply device that includes an electronic element or circuit with rectifying properties. [Figure 4] This is the first diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. [Figure 5] This is a second diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. [Figure 6] This is a third diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. [Figure 7] This is the fourth diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. [Figure 8] This diagram illustrates a method for ensuring the maximum allowable circuit voltage between lines. [Figure 9] This diagram illustrates a method for calculating the difference in operating voltage. [Figure 10] This is the first figure showing an example of the configuration of a lightning protection device according to this embodiment. [Figure 11] This is a second figure showing an example of the configuration of a lightning protection device according to this embodiment. [Figure 12] This is a third figure showing an example of the configuration of a lightning protection device according to this embodiment.

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention (the present embodiment) will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments. Before explaining the technology according to the present embodiment, first, the related prior art and its problems will be described.

[0010] (Regarding the prior art) FIG. 1 is a diagram showing an example of the configuration of a conventional lightning protection device. The lightning protection device 10 is a device for protecting a DC power supply device 20 (and its internal circuit 21) from lightning surges. The lightning protection device 10 includes a lightning protection element or circuit (hereinafter, varistor) such as a zinc oxide varistor. Specifically, the lightning protection device 10 includes a positive electrode varistor 11 and a negative electrode varistor 12.

[0011] The positive electrode varistor 11 is connected between the positive electrode side power supply cable 901 of the DC power supply device 20 and the ground point 903. The positive electrode varistor 11 is an example of a positive electrode side lightning arrester (lightning protection element or circuit). The negative electrode varistor 12 is connected between the negative electrode side power supply cable 902 of the DC power supply device 20 and the ground point 903. The negative electrode varistor 12 is an example of a negative electrode side lightning arrester (lightning protection element or circuit).

[0012] In the configuration of FIG. 1, when a lightning surge current is generated due to a lightning strike or the like, the lightning surge current can be discharged to the ground point 903 via the positive electrode varistor 11 and the negative electrode varistor 12.

[0013] FIG. 2 is a diagram for explaining the case where a lightning surge invades a DC power supply device including an electronic element or circuit having a rectifying action. The DC power supply device 20 shown in FIG. 2 has a diode 22. The diode 22 is an example of an electronic element or circuit having a rectifying action.

[0014] In the configuration of FIG. 2, when a lightning surge current is generated due to a lightning strike or the like, no voltage is applied to the negative varistor 12 by the diode 22, and the lightning surge current that has invaded the negative side may flow to the positive side through the diode 22 and then flow to the ground point 903 through the positive varistor 11. Therefore, there is a possibility that the diode 22 may be damaged by the lightning surge current and the DC power supply device 20 may malfunction.

[0015] FIG. 3 is a diagram for explaining the case where a lightning surge invades only the positive side of a DC power supply device including an electronic element or an electronic circuit having a rectifying action. When a lightning surge invades only the positive side, no lightning surge current flows into the diode 22, so the positive varistor 11 operates normally and the DC power supply device 20 does not malfunction.

[0016] FIG. 4 is a first diagram for explaining the case where a lightning surge invades only the negative side of a DC power supply device including an electronic element or an electronic circuit having a rectifying action. When a lightning surge invades only the negative side, a lightning surge current flows into the diode 22, so no voltage is applied to the negative varistor 12 (the varistor does not operate), and there is a possibility that the DC power supply device 20 may malfunction due to damage to the diode 22.

[0017] Note that FIG. 4 shows the lightning surge current flowing through each varistor when the operating voltages of the positive varistor 11 and the negative varistor 12 are approximately the same (for example, both are 910V). In this case, no lightning surge current flows through the negative varistor 12, and most of the lightning surge current generated in the positive varistor 11 flows.

[0018] Figure 5 is a second diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. Figure 5 shows the lightning surge current flowing through each varistor when there is a small difference in the operating voltages of the positive varistor 11 and the negative varistor 12 (for example, the operating voltage of the positive varistor 11 is 910V and the operating voltage of the negative varistor 12 is 790V). By creating a difference in operating voltages, the negative varistor 12 becomes more likely to operate, allowing the invading lightning surge to flow not only to the positive side but also to the negative side.

[0019] Figure 6 is a third diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. Figure 6 shows the lightning surge current flowing through each varistor when there is a relatively large difference in the operating voltages of the positive varistor 11 and the negative varistor 12 (for example, the operating voltage of the positive varistor 11 is 910V and the operating voltage of the negative varistor 12 is 680V). By creating a relatively large difference in operating voltages, the negative varistor 12 becomes more easily operated, and the invading lightning surge can be distributed almost equally between the positive and negative sides. As a result, the lightning surge current flowing through the diode 22 is reduced, and failure of the DC power supply device 20 can be prevented.

[0020] Figure 7 is a fourth diagram illustrating the case where a lightning surge enters only the negative side of a DC power supply device that includes an electronic element or circuit with rectifying properties. Figure 7 shows the lightning surge current flowing through each varistor when there is an extremely large difference in the operating voltages of the positive varistor 11 and the negative varistor 12 (for example, the operating voltage of the positive varistor 11 is 910V and the operating voltage of the negative varistor 12 is 470V). By creating a relatively large difference in operating voltages, only the negative varistor 12 operates, allowing almost all of the invading lightning surge to flow to the negative side. As a result, almost no lightning surge current flows through the diode 22, thus preventing failure of the DC power supply device 20.

[0021] Figure 8 illustrates how to ensure the maximum allowable circuit voltage between the lines. The positive varistor 11 and the negative varistor 12 have a maximum allowable circuit voltage for operation under normal circumstances, and their operating voltage cannot be freely reduced. The maximum allowable circuit voltage is determined by the output voltage of the DC power supply device 20.

[0022] Therefore, in order to ensure the voltage to ground, as shown in Figure 8, the lightning protection device 10 is equipped with a varistor 13 for ensuring the voltage to ground between the positive varistor 11 and the negative varistor 12 and the grounding point 903. This makes it possible to ensure the maximum allowable circuit voltage between ground and between lines. The varistor 13 for ensuring the voltage to ground is an example of a surge arrester (surge arrester element or surge arrester circuit) for ensuring the voltage to ground.

[0023] Next, we will explain how to calculate an appropriate value for the difference in operating voltage between the positive varistor 11 and the negative varistor 12.

[0024] Figure 9 is a diagram illustrating a method for calculating the difference in operating voltage. The method shown in Figure 9 is an example of a method for calculating an appropriate value as the difference in operating voltage by conducting a test that generates a lightning surge. The assumed lightning surge (e.g., combination waveform, 10 / 350ms waveform, etc.) is applied to the DC power supply device 20 to be protected as follows.

[0025] First, a lightning surge (first lightning surge) is applied to the positive terminal side, gradually increasing the level from a low level, and the level at which a fault occurs is defined as the operating voltage V(+).

[0026] Secondly, a lightning surge (second lightning surge) is applied to the negative electrode side, gradually increasing the level from a low level, and the level at which a fault occurs is defined as the operating voltage V(-).

[0027] Thirdly, the difference in operating voltage V (diff) is calculated using the following equation 1.

[0028] V(diff) = V(+) - V(-) ... (Equation 1)

[0029] Alternatively, an appropriate value may be calculated as the difference in operating voltage from the withstand voltage of diode 22, without relying on testing.

[0030] For example, the operating voltage difference V(diff) is determined by the following equation 2, using the diode's breakdown voltage V(d) as a reference. Here, a is a coefficient less than or equal to 1.

[0031] V(diff) = a × V(d) ... (Equation 2)

[0032] Alternatively, both the test results and the breakdown voltage of diode 22 may be considered. For example, the difference in operating voltage V (diff) is determined by the following equation 3.

[0033] V(diff)=[a×V(d)+b{V(+)-V(-)}] / 2...(Equation 3)

[0034] (Configuration of the lightning protection device according to this embodiment) Figure 10 is the first diagram showing an example of the configuration of the lightning protection device according to this embodiment. Based on the above considerations, the lightning protection device 10 according to this embodiment comprises a positive varistor 11, a negative varistor 12, a varistor 13 for securing voltage to ground, a positive terminal 14, a negative terminal 15, and a grounding terminal 16.

[0035] The operating voltage of the positive varistor 11 is higher than the operating voltage of the negative varistor 12. Using the difference V(diff) determined by the calculation method described above as a reference value, the difference in operating voltage may be, for example, greater than or equal to the reference value.

[0036] Figure 11 is a second diagram showing an example of the configuration of a lightning protection device according to this embodiment. The lightning protection device 10 comprises a positive varistor 11 (for example, with an operating voltage of 910V), a plurality of negative varistors, a varistor 13 for ensuring voltage to ground, a positive terminal 14, a plurality of negative terminals, and a ground terminal 16.

[0037] The multiple negative varistors include, for example, a first negative varistor 12a (operating voltage 390V), a second negative varistor 12b (operating voltage 470V), and a third negative varistor 12c (operating voltage 680V).

[0038] Furthermore, the multiple negative terminals include a first negative terminal 15a corresponding to the first negative varistor 12a, a second negative terminal 15b corresponding to the second negative varistor 12b, and a third negative terminal 15c corresponding to the third negative varistor 12c.

[0039] According to the lightning protection device 10 shown in Figure 11, the operating voltage of the negative varistor can be selected by selecting the negative terminal depending on the device to be protected.

[0040] Figure 12 is a third diagram showing an example of the configuration of a lightning protection device according to this embodiment. The lightning protection device 10 comprises a positive varistor 11 (for example, with an operating voltage of 910V), a plurality of negative varistors, a varistor 13 for ensuring voltage to ground, a positive terminal 14, a negative terminal 15, a grounding terminal 16, and a plurality of switches.

[0041] The multiple negative varistors include, for example, a first negative varistor 12a (operating voltage 390V), a second negative varistor 12b (operating voltage 470V), and a third negative varistor 12c (operating voltage 680V).

[0042] Furthermore, the multiple switches include a first switch 17a corresponding to the first negative varistor 12a, a second switch 17b corresponding to the second negative varistor 12b, and a third switch 17c corresponding to the third negative varistor 12c.

[0043] According to the lightning protection device 10 shown in Figure 12, the operating voltage of the negative varistor can be selected by switching a switch depending on the device to be protected.

[0044] According to the lightning protection device 10 of this embodiment, by creating a difference in the operating voltage between the positive varistor 11 and the negative varistor 12, the negative varistor 12 becomes more likely to operate, allowing the incoming lightning surge to flow not only to the positive side but also to the negative side. This reduces the lightning surge current passing through the diode 22 and reduces the risk of failure of the DC power supply device 20. Therefore, even if there are electronic elements or circuits with rectifying properties between the lines of the DC power supply device 20, the lightning surge can be properly discharged to ground.

[0045] (Summary of the embodiments) This specification includes lightning protection devices and lightning protection methods as described in at least the following sections. (Section 1) A lightning protection device for protecting a DC power supply device from lightning surge currents, A positive-side surge arrester is connected between the positive-side power cable of the DC power supply device and the ground point. The DC power supply device includes a negative-side surge arrester connected between the negative-side power cable and the ground point, The difference in operating voltage between the positive-side surge arrester and the negative-side surge arrester is greater than or equal to a reference value. Lightning protection device. (Section 2) The system further includes a surge arrester for ensuring the voltage between the positive and negative surge arresters to ground. Lightning protection device as specified in paragraph 1. (Section 3) The negative-side surge arrester includes a plurality of negative-side surge arresters with different operating voltages. Each of the aforementioned multiple negative-side surge arresters further comprises multiple negative terminals connected to each of them. Lightning protection device as described in paragraph 1 or 2. (Section 4) The negative-side surge arrester includes a plurality of negative-side surge arresters with different operating voltages. The system further includes a switch to select each of the aforementioned multiple negative-side surge arresters. Lightning protection device as described in paragraph 1 or 2. (Section 5) A lightning protection method for protecting a DC power supply device from lightning surge currents, A positive-side surge arrester is connected between the positive-side power cable of the DC power supply device and the ground point. A negative-side surge arrester is connected between the negative-side power cable of the DC power supply device and the ground point. The difference in operating voltage between the positive-side surge arrester and the negative-side surge arrester is set to be equal to or greater than a reference value. Lightning protection method.

[0046] Although this embodiment has been described above, the present invention is not limited to this specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0047] 10 Lightning protection device 11 Positive varistor 12 Negative Electrode Barista 12a First negative varistor 12b Second negative varistor 12c Third Negative VARISTOR 13. Varistor for ensuring voltage to ground 14 Positive terminal 15 Negative terminal 15a First negative terminal 15b Second negative terminal 15c Third negative terminal 16 Ground terminal 17a First switch 17b Second switch 17c Third switch 20 DC power supply device 21 Internal circuit 22 diodes 30 Power Cables 901 Positive side power cable 902 Negative side power cable 903 Grounding point

Claims

1. A lightning protection device for protecting a DC power supply device from lightning surge currents, A positive-side surge arrester is connected between the positive-side power cable of the DC power supply device and the ground point. The DC power supply device includes a negative-side surge arrester connected between the negative-side power cable and the ground point, The operating voltage of the positive-side surge arrester is higher than the operating voltage of the negative-side surge arrester, the difference in operating voltage between the positive-side surge arrester and the negative-side surge arrester is greater than or equal to a reference value, and an electronic element or electronic circuit having a rectifying effect is provided between the positive-side power cable and the negative-side power cable. Lightning protection device.

2. The system further includes a surge arrester for ensuring the voltage between the positive and negative surge arresters to ground. Lightning protection device according to claim 1.

3. The negative-side surge arrester includes a plurality of negative-side surge arresters with different operating voltages. Each of the aforementioned multiple negative-side surge arresters further comprises multiple negative terminals connected to each of them. A lightning protection device according to claim 1 or 2.

4. The negative-side surge arrester includes a plurality of negative-side surge arresters with different operating voltages. The system further includes a switch to select each of the aforementioned multiple negative-side surge arresters. A lightning protection device according to claim 1 or 2.

5. A lightning protection method for protecting a DC power supply device from lightning surge currents, A positive-side surge arrester is connected between the positive-side power cable of the DC power supply device and the ground point. A negative-side surge arrester is connected between the negative-side power cable of the DC power supply device and the ground point. The lightning protection method is such that the operating voltage of the positive-side surge arrester is higher than the operating voltage of the negative-side surge arrester, and the difference between the operating voltages of the positive-side surge arrester and the negative-side surge arrester is greater than or equal to a reference value. An electronic element or circuit having a rectifying effect is provided between the positive-side power cable and the negative-side power cable. Lightning protection method.

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