Lightning protection device

Abstract

To provide a lightning protection device that reduces energy loss. [Solution] The device comprises a surge-resistant transformer 1 for suppressing the transition voltage of lightning surges, and a filter circuit 2 connected to the primary side of the surge-resistant transformer. The impedance of the filter circuit 2 is 100Ω or more and less than 1000Ω. The frequency-to-gain characteristics of the lightning protection device are such that the gain is maintained at 0 in the frequency band of 100Hz or less, and the gain is 0 or less near the frequency corresponding to the resonance point of the surge-resistant transformer 1.

Description

Technical Field

[0001] The present invention relates to a lightning protection device for protecting electrical equipment and the like from abnormal high voltages such as lightning surges.

Background Art

[0002] Conventionally, a high-frequency suppression circuit is added to the secondary side of a lightning-resistant transformer for suppressing the transition voltage of a lightning surge that transitions from the primary side to the secondary side, so that high-frequency noise caused by high-frequency components included in the lightning surge transition voltage does not adversely affect various electrical equipment (Patent Document 1). The high-frequency suppression circuit described in Patent Document 1 had an attenuation characteristic of reducing high-frequency components of 200 to 300 kHz including a 210 kHz high-frequency component.

[0003] The high-frequency suppression circuit described in Patent Document 1 is a direct resonance circuit composed of a resistor, a coil, and a capacitor. The resistance value R of the resistor related to the high-frequency suppression circuit is 10.3 Ω, the reactance L of the coil is 32 μH, and the capacitance C of the capacitor is 0.023 μF.

[0004] By the way, the inventor has confirmed through independent research that there is a resonance point near 100 kHz in the frequency characteristics between the terminals of the lightning-resistant transformer, which is the same as the frequency band of the lightning surge (Non-Patent Document 1). Due to the existence of such a resonance point, when a lightning surge transitions from the primary side to the secondary side, there is a concern that the surge voltage will appear largely on the secondary side.

[0005] Therefore, in Non-Patent Document 1, the inventor has proposed connecting filter circuits to the primary side and the secondary side of the lightning-resistant transformer to address this concern. The primary-side filter circuit described in Non-Patent Document 1 is a series circuit composed of a resistor, a coil, and a capacitor. The resistance value R of the resistor is 1 Ω, the reactance L of the coil is 22 μH, and the capacitance C of the capacitor was 220 μF.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Patent No. 6119012 [Non-patent literature]

[0007] [Non-Patent Document 1] IEEJ Study Group Materials, The Papers of Technical Meeting on “High Engineering”, IEE Japan 2023.1.26-27, HV-23-021, P.103~P.108 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, it was confirmed that with this circuit configuration, when a low-frequency voltage of several tens of Hz is applied, current flows to the resistor, resulting in energy loss.

[0009] This invention was made to solve the above problems and aims to provide a lightning protection device that reduces energy loss. [Means for solving the problem]

[0010] To achieve the above objective, a lightning protection device according to one aspect of the present invention has the following features.

[0011] (1) A voltage-resistant transformer for suppressing the transition voltage of lightning surges, and a filter circuit connected to the primary side of the voltage-resistant transformer, The impedance of the aforementioned filter circuit is 100Ω or more and less than 1000Ω. The frequency-to-gain characteristics of the lightning protection device are characterized in that the gain is maintained at 0 in the frequency band of 100 Hz or less, and the gain is 0 or less near the frequency corresponding to the resonance point of the lightning protection transformer.

[0012] (2) In the lightning protection device described in (1), the filter circuit has a coil, a capacitor, and a resistor arranged in series from the primary side. The resistance value of the resistor may be greater than 1Ω, and the capacitance of the capacitor may be less than 220μF. (3)(2) In the lightning protection device described above, The secondary side of the aforementioned power-insulating transformer may be configured so that no filter circuit other than the aforementioned filter circuit is connected. (4)(2) In the lightning protection device described above, The resistance value of the resistor may be less than 10Ω. [Effects of the Invention]

[0013] According to the present invention, energy loss can be reduced. [Brief explanation of the drawing]

[0014] [Figure 1] This is an example of a circuit configuration for a lightning protection device according to the first embodiment. [Figure 2] (a) is a graph showing the frequency-to-gain characteristics of the filter circuit according to the first embodiment, and (b) is a graph showing the frequency-to-phase characteristics of the filter circuit according to the first embodiment. [Figure 3] (a) is a graph showing the frequency-to-gain characteristics of the lightning protection device according to the first embodiment, and (b) is a graph showing the frequency-to-phase characteristics according to the first embodiment. [Figure 4] (a) is a graph showing the frequency-to-gain characteristics of the filter circuit related to Effectiveness Verification Comparison 1, and (b) is a graph showing the frequency-to-phase characteristics of the filter circuit related to Effectiveness Verification Comparison 1. [Figure 5] (a) is a graph showing the frequency-to-gain characteristics of the lightning protection device related to Effectiveness Verification Comparison 1, and (b) is a graph showing the frequency-to-phase characteristics of the lightning protection device related to Effectiveness Verification Comparison 1. [Figure 6] This is an example of a circuit configuration for a lightning protection device related to the effectiveness verification comparison 2. [Figure 7](a) is a graph showing the frequency - gain characteristics of the lightning protection device related to the effectiveness verification comparison 2, and (b) is a graph showing the frequency - phase characteristics of the lightning protection device related to the effectiveness verification comparison 2. [Figure 8] It is a circuit configuration example of the lightning protection device related to the effectiveness verification comparison 3. [Figure 9] (a) is a graph showing the frequency - gain characteristics of the lightning protection device related to the effectiveness verification comparison 3, and (b) is a graph showing the frequency - phase characteristics of the lightning protection device related to the effectiveness verification comparison 3.

Embodiments for Carrying out the Invention

[0015] <First Embodiment> Hereinafter, the lightning protection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration example of the lightning protection device X1 according to the first embodiment. As shown in FIG. 1, the lightning protection device X1 has a lightning - resistant transformer 1, a filter circuit 2, an input terminal 3, and an output terminal 4.

[0016] First, the lightning - resistant transformer 1 will be described. The lightning - resistant transformer 1 has a primary - side circuit 11, a secondary - side circuit 12, an electrostatic shield layer 13, an in - transformer input terminal 14, and an in - transformer output terminal 15.

[0017] The primary - side circuit 11 has a primary - side first wire 11a, a primary - side second wire 11b, and a primary - side coil 11c. The primary - side coil 11c is connected to both the primary - side first wire 11a and the primary - side second wire 11b.

[0018] The secondary - side circuit 12 has a secondary - side first wire 12a, a secondary - side second wire 12b, and a secondary - side coil 12c. The secondary - side coil 12c is connected to both the secondary - side first wire 12a and the secondary - side second wire 12b.

[0019] The electrostatic shield layer 13 is formed between the primary - side coil 11c and the secondary - side coil 12c.

[0020] The transformer's internal input terminal 14 consists of a first input terminal 14a and a second input terminal 14b. The first input terminal 14a is connected to the primary side first wire 11a, and the second input terminal 14b is connected to the primary side second wire 11b. The primary side second wire 11b is connected to ground via the second input terminal 14b.

[0021] The transformer's internal output terminal 15 consists of a first output terminal 15a and a second output terminal 15b. The first output terminal 15a is connected to the secondary first wire 12a, and the second output terminal 15b is connected to the secondary second wire 12b. The secondary second wire 12b is connected to ground via the second output terminal 15b.

[0022] Next, filter circuit 2 will be described. Filter circuit 2 includes internal wires 20, a resistor 21, a capacitor 22, an inductor 23, an internal input terminal 24, and an internal output terminal 25.

[0023] The filter's internal wiring 20 includes a first internal wiring 20a, a second internal wiring 20b, and a third internal wiring 20c. The first internal wiring 20a and the second internal wiring 20b are arranged in parallel. The first internal wiring 20a and the second internal wiring 20b are connected by the third internal wiring 20c.

[0024] The filter's internal input terminal 24 consists of a first internal input terminal 24a and a second internal input terminal 24b. The first internal input terminal 24a is connected to the first internal wire 20a, and the second internal input terminal 24b is connected to the second internal wire 20b.

[0025] The filter's internal output terminal 25 consists of a first internal output terminal 25a and a second internal output terminal 25b. The first internal output terminal 25a is connected to the first internal wire 20a, and the second internal output terminal 25b is connected to the second internal wire 20b.

[0026] Resistor 21 is located in the third wire 20c within the filter. Capacitor 22 is located on the first wiring 20a side of the filter, closer to resistor 21, in the third wire 20c within the filter. Coil 23 is located between the first input terminal 24a within the filter on the first wiring 20a within the filter and node Y between the first wiring 20a and the third wiring 20c within the filter. Therefore, resistor 21, capacitor 22, and coil 23 form a series circuit.

[0027] The resistance R of resistor 21 is 5Ω, the capacitance C of capacitor 22 is 4.7μF, and the reactance L of coil 23 is 47μH.

[0028] Furthermore, the filter circuit 2 is connected to the primary side circuit 11 of the lightning protection transformer 1 via the filter's output terminal 25. Specifically, the first output terminal 25a of the filter is connected to the first input terminal 14a of the transformer, and the second output terminal 25b of the filter is connected to the second input terminal 14b of the transformer.

[0029] Here, we will describe the frequency characteristics of the input voltage (V1) and output voltage (V2) of the filter circuit 2. Figure 2(a) is a graph showing the frequency-to-gain characteristics of the filter circuit 2, and Figure 2(b) is a graph showing the frequency-to-phase characteristics of the filter circuit 2.

[0030] In Figures 2(a) and 2(b), the horizontal axis represents frequency on a logarithmic scale. On the other hand, the vertical axis in Figure 2(a) represents gain (20·log 10 (V2 / V1))[dB] represents the phase (tan). The vertical axis in Figure 2(b) is the phase (tan). -1 This represents (V2 / V1)[θ]. Note that the graphs shown in Figures 2(a) and 2(b) represent the results measured by the inventor.

[0031] As shown in Figure 2(a), the gain is maintained at "0" in the low-frequency band below 100 Hz and in the frequency band between 100 Hz and 2-3 kHz, while the gain decreases as the frequency increases in the frequency band above 10 kHz.

[0032] Let's return to Figure 1 for the explanation. Next, let's describe input terminal 3. Input terminal 3 consists of a first input terminal 3a and a second input terminal 3b. The first input terminal 24a inside the filter is connected to the first input terminal 3a, and the second input terminal 24b inside the filter is connected to the second input terminal 3b. A power supply (not shown) is connected to both the first input terminal 3a and the second input terminal 3b.

[0033] Next, we will describe output terminal 4. Output terminal 4 consists of a first output terminal 4a and a second output terminal 4b. The first output terminal 15a inside the transformer is connected to the first output terminal 4a, and the second output terminal 15b inside the transformer is connected to the second output terminal 4b. Equipment that is subject to lightning protection (not shown) is connected to the first output terminal 4a and the second output terminal 4b.

[0034] Here, we will describe the frequency characteristics of the input voltage (V1) and output voltage (V2) of the lightning protection device X1. In Figure 3(a), the solid line represents the frequency-to-gain characteristics of the lightning protection device X1, and in Figure 3(b), the solid line represents the frequency-to-phase characteristics of the lightning protection device X1. In addition, the dashed line in Figure 3(a) represents the frequency-to-gain characteristics of the lightning protection transformer 1, and in Figure 3(b), the dashed line represents the frequency-to-phase characteristics of the lightning protection transformer 1.

[0035] In Figures 3(a) and 3(b), the horizontal axis represents frequency on a logarithmic scale. On the other hand, the vertical axis in Figure 3(a) represents gain (20·log 10 (V2 / V1))[dB] represents the phase (tan). The vertical axis in Figure 3(b) is the phase (tan). -1 This represents (V2 / V1)[θ]. Note that the graphs shown in Figures 3(a) and 3(b) represent the results measured by the inventor.

[0036] As shown in Figure 3(a), the gain is maintained at "0" in the low-frequency band below 100 Hz, and in the frequency band above 100 Hz, the gain generally decreases gradually as the frequency increases, except at 100 kHz. Furthermore, although the frequency corresponding to the resonance point of the lightning protection transformer 1 is considered to be around 100 kHz, the gain at the frequency corresponding to this resonance point (around 100 kHz) is suppressed so as not to exceed "0". In addition, no propagation of current to the resistor 21 was confirmed in the low-frequency band below 100 Hz. Regarding the lightning protection device X1, in the low-frequency band below 100 Hz, the voltage applied to the first output terminal 25a and the second output terminal 25b in the filter is almost the same as the voltage applied to the first input terminal 3a and the second input terminal 3b. On the other hand, in the high-frequency band above 100 kHz, the voltage is divided by resistor 23, so the voltage applied to the first output terminal 25a and the second output terminal 25b in the filter becomes lower than the voltage applied to the first input terminal 3a and the second input terminal 3b.

[0037] Next, we will describe Comparison 1 (Effectiveness Verification Comparison 1) for verifying the effectiveness of the lightning protection device X1 in suppressing gain increase. As part of Effectiveness Verification Comparison 1, we measured the frequency characteristics of lightning protection device X2 in which filter circuit 2 was replaced with another filter circuit 6.

[0038] The circuit configuration of filter circuit 6 is the same as that of filter circuit 2. Therefore, although not shown in the diagram, filter circuit 6, like filter circuit 2, has a resistor 61, a capacitor 62, and an inductor 63. The resistance value R of resistor 61 is 10Ω, the capacitance C of capacitor 62 is 4.7μF, and the reactance L of inductor 63 is 470μH.

[0039] Here, we will describe the frequency characteristics of the input voltage (V1) and output voltage (V2) of the filter circuit 6. Similar to Figures 2(a) and 2(b), Figure 4(a) is a graph representing the frequency-to-gain characteristics of the filter circuit 6, and Figure 4(b) is a graph representing the frequency-to-phase characteristics of the filter circuit 6.

[0040] As shown in Figure 4(a), regarding the frequency-gain characteristics, similar to the case of filter circuit 2, the gain is maintained at "0" in the low-frequency band below 100 Hz and in the frequency band from 100 Hz to 2-3 kHz, while in the frequency band above 10 kHz, the gain decreases as the frequency increases.

[0041] Next, the frequency characteristics of the input voltage (V1) and output voltage (V2) of the lightning protection device X2, which has been replaced by the filter circuit 6, will be described. Similar to Figures 3(a) and 3(b), the solid line in Figure 5(a) is a graph representing the frequency-to-gain characteristics of the lightning protection device X2, and the solid line in Figure 5(b) is a graph representing the frequency-to-phase characteristics of the lightning protection device X2. The dashed line in Figure 5(a) is a graph representing the frequency-to-gain characteristics of the lightning protection transformer 1, and the dashed line in Figure 5(b) is a graph representing the frequency-to-phase characteristics of the lightning protection transformer 1.

[0042] As shown in Figure 5(a), regarding the frequency-gain characteristics, similar to the case of filter circuit 2, the gain is maintained at "0" in the low-frequency band below 100 Hz. However, unlike the case of filter circuit 2, the gain is maintained at "0" from above 100 Hz up to around 30 kHz, and then rises sharply up to around 100 kHz, in a range where the gain exceeds "0" but does not exceed the range where filter circuit 6 is not included, similar to the case where filter circuit 6 is not included. Then, above 100 kHz, the gain decreases as the frequency increases.

[0043] Next, we will explain Comparison 2 (Effectiveness Verification Comparison 2) for verifying the effectiveness of the lightning protection device X1 in suppressing gain increase. As part of Effectiveness Verification Comparison 2, we measured the frequency characteristics of lightning protection device X3, in which the filter circuit 6 was connected to the secondary side of the lightning protection transformer 1.

[0044] Figure 6 shows an example of the circuit configuration of the lightning protection device X3. As shown in Figure 6, the first output terminal 15a inside the transformer is connected to the first input terminal 64a inside the filter circuit 6, and the second output terminal 15b inside the transformer is connected to the second input terminal 24b inside the filter circuit 6. In addition, the first output terminal 4a inside the filter circuit 6 is connected to the first output terminal 65a inside the filter circuit 6, and the second output terminal 4b inside the filter circuit 6 is connected to the first output terminal 65b inside the filter circuit 6.

[0045] Here, we will describe the frequency characteristics of the input voltage (V1) and output voltage (V2) of the lightning protection device X3. Similar to Figures 3(a) and 3(b), the solid line in Figure 7(a) is a graph representing the frequency-to-gain characteristics of the lightning protection device X3, and the solid line in Figure 7(b) is a graph representing the frequency-to-phase characteristics of the lightning protection device X3. The dashed line in Figure 7(a) is a graph representing the frequency-to-gain characteristics of the lightning protection transformer 1, and the dashed line in Figure 7(b) is a graph representing the frequency-to-phase characteristics of the lightning protection transformer 1.

[0046] As shown in Figure 7(a), the frequency-gain characteristics are similar to those of the lightning protection device X1, with the gain remaining at "0" in the low-frequency band below 100 Hz. Furthermore, the gain remains at "0" in the frequency band from 100 Hz to 200-300 Hz. In the frequency band from 200-300 Hz to 100 kHz, the gain gradually decreases with increasing frequency, with a steeper slope than in the case of the lightning protection device X1. However, unlike the lightning protection device X1, the gain does not rise sharply around 100 kHz, but is maintained in the frequency band from 100 kHz to 300-400 kHz, and then gradually increases with increasing frequency in the frequency bands beyond that. In other words, the gain is at its lowest point in the frequency band from 100 kHz to 300-400 kHz. Furthermore, with respect to the lightning protection device X3, in the low-frequency band below 100 Hz, the voltages applied to the first output terminal 65a and the second output terminal 65b within the filter are almost the same as the voltages applied to the first input terminal 3a and the second input terminal 3b. On the other hand, in the high-frequency band above 100 kHz, the voltage is divided by the resistor 63, so the voltages applied to the first output terminal 65a and the second output terminal 65b within the filter are lower than the voltages applied to the first input terminal 3a and the second input terminal 3b.

[0047] Next, we will explain Comparison 3 (Effectiveness Verification Comparison 3) for verifying the effectiveness of the gain increase suppression effect of the lightning protection device X1. As part of Effectiveness Verification Comparison 3, we measured the frequency characteristics of lightning protection device X4, in which a filter circuit 6 is connected to the secondary side of the lightning protection transformer 1 in lightning protection device X1. Since lightning protection device X1 and lightning protection device X3, in which a filter circuit 6 is connected to the secondary side of the lightning protection transformer 1, have been described above, a detailed explanation of the circuit configuration of lightning protection device X4 will be omitted, but Figure 8 shows an example of the circuit configuration of lightning protection device X4.

[0048] Here, we will describe the frequency characteristics of the input voltage (V1) and output voltage (V2) of the lightning protection device X4. Similar to Figures 3(a) and 3(b), the solid line in Figure 9(a) is a graph representing the frequency-to-gain characteristics of the lightning protection device X4, and the solid line in Figure 9(b) is a graph representing the frequency-to-phase characteristics of the lightning protection device X4. The dashed line in Figure 9(a) is a graph representing the frequency-to-gain characteristics of the lightning protection transformer 1, and the dashed line in Figure 9(b) is a graph representing the frequency-to-phase characteristics of the lightning protection transformer 1.

[0049] As shown in Figure 9(a), the frequency-to-gain characteristics are similar to those of lightning protection device X1, with the gain remaining at "0" in the low-frequency band below 100Hz. Furthermore, the gain remains at "0" in the frequency band from 100Hz to 200-300Hz. In the frequency band from 200-300Hz to 100kHz, the gain decreases with increasing frequency at a steeper rate than that of lightning protection device X1, and even steeper than that of lightning protection device X3. However, unlike lightning protection device X1, the gain increases with increasing frequency in the frequency band above 100kHz. That is, the gain is lowest around 100kHz. For lightning protection device X4, in the low-frequency band below 100Hz, the voltages applied to the first output terminal 25a and the second output terminal 25b within the filter are almost identical to the voltages applied to the first input terminal 3a and the second input terminal 3b. On the other hand, in the high-frequency band above 100 kHz, the voltage is divided by resistor 23, so the voltages applied to the first output terminal 25a and the second output terminal 25b within the filter become lower than the voltages applied to the first input terminal 3a and the second input terminal 3b.

[0050] The graphs shown in Figures 4(a) and 4(b), 5(a) and 5(b), 7(a) and 7(b), and 9(a) and 9(b) represent the results measured by the inventor.

[0051] As described above, the lightning protection device X1 comprises a surge-resistant transformer 1 for suppressing the transition voltage of lightning surges, and a filter circuit 2 connected to the primary side of the surge-resistant transformer 1. The impedance of the filter circuit 1 is 100Ω or more and less than 1000Ω. The frequency-to-gain characteristics of the lightning protection device X1 are such that the gain is maintained at 0 in the frequency band of 100Hz or less, and the gain is 0 or less near the frequency corresponding to the resonance point of the surge-resistant transformer 1 (around 100KHz). Therefore, it is possible to prevent energy loss while preventing the impact on the lightning protection performance from equipment connected to the secondary side of the lightning protection device X1.

[0052] Furthermore, in filter circuit 2, the coil 21, capacitor 22, and resistor 23 are arranged in series from the primary side. Since the resistance value of resistor 21 is greater than 1Ω and the capacitance of capacitor 22 is less than 220μF, it is possible to more reliably prevent current from propagating to resistor 21 in the low frequency band below 100Hz. Moreover, in the lightning protection device X1, since no filter circuit other than filter circuit 2 is connected to the secondary side of the surge-proof transformer 1, the cost of the lightning protection device X1 is reduced. In addition, since the resistance value of resistor 21 in filter circuit 2 is less than 10Ω, the gain increase near the frequency corresponding to the resonance point of the surge-proof transformer 1 can be kept below zero.

[0053] It should be noted that the embodiments described above are merely illustrative examples and do not limit this disclosure in any way. Various improvements and modifications are possible without departing from the gist of the disclosure.

[0054] For example, the circuit configuration of the filter circuit connected to the primary side of the lightning protection transformer 1, and the specifications of each circuit element, may be appropriately modified as long as the gain is maintained at 0 in the frequency band below 100 Hz and the gain is 0 or less around the frequency corresponding to the resonance point of the lightning protection transformer 1 (for example, 100 kHz). [Explanation of symbols]

[0055] X1~X4...Lightning protection devices 1…Lightning-protected transformer 2, 6... Filter circuits 3…Input terminals 4…Output terminals 11…Primary side circuit 12…Secondary side circuit 13…Electrostatic shielding layer 21, 61… Resistance 22, 62… Capacitors 23, 63... coil

Claims

1. The system comprises a surge-resistant transformer for suppressing the transition voltage of lightning surges, and a filter circuit connected to the primary side of the surge-resistant transformer. The impedance of the aforementioned filter circuit is 100Ω or more and less than 1000Ω. A lightning protection device characterized in that, as a frequency-to-gain characteristic of the said lightning protection device, the gain is maintained at 0 in the frequency band of 100 Hz or less, and the gain is 0 or less near the frequency corresponding to the resonance point of the lightning protection transformer.

2. A lightning protection device according to claim 1, In the aforementioned filter circuit, a coil, a capacitor, and a resistor are arranged in series from the primary side. A lightning protection device characterized in that the resistance value of the resistor is greater than 1 ohm and the capacitance of the capacitor is less than 220 μF.

3. A lightning protection device according to claim 2, A lightning protection device characterized in that no filter circuit other than the filter circuit is connected to the secondary side of the power-insulating transformer.

4. A lightning protection device according to claim 2, A lightning protection device characterized by having a resistance value less than 10 ohms.

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