Surge protection device separator

Abstract

To provide a surge protection device separator that is compact and has both high surge current withstand capability and low rated current capability.SOLUTION: A surge protection device separator device 1 is connected in series to a surge protection device 3 that protects a device 2 to be protected against over-voltage surges. The surge protection device separator 1 includes a series circuit of a current breaker 20 and a resistor 21 and a voltage switching type surge protection component 22 connected in parallel to the series circuit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surge protection device isolation apparatus that is connected in series with a surge protection device that protects a protected device against overvoltage surges. [Background technology]

[0002] Conventionally, in low-voltage power distribution systems, surge protective devices (SPDs) are installed to protect electrical / electronic equipment, communication equipment, and other protected devices from transient overvoltage surges caused by non-direct lightning strikes. A surge protective device typically consists of a series circuit of an internal separator, a metal oxide varistor (MOV), and a gas discharge tube (GDT).

[0003] The MOV of such an SPD is connected between the charging line and neutral line of the power supply, and therefore deteriorates over time due to being constantly subjected to a voltage from the commercial power supply, and to repeated operation due to multiple lightning surges, etc. Deterioration of the MOV undesirably increases leakage current and generates self-heating.

[0004] In addition, if an excessive surge current flows through the MOV and causes an instantaneous short-circuit fault, the power source's charging line and neutral line will be short-circuited. If this short-circuit condition continues, a current interrupter such as a breaker upstream of the SPD in the distribution system will operate and cut off the power supply, causing a power outage in the protected equipment and causing the equipment to stop operating.

[0005] Therefore, when an SPD fails, it is necessary to quickly disconnect the SPD before the upstream current breaker operates.As an SPD disconnecting device used to disconnect such an SPD, there is known one that increases the surge current resistance by fusing a low melting point alloy to the fusible element of a conventional current fuse, and that, when a fault current flows, fuses the fusible element by utilizing the diffusion of a low melting point metal to disconnect the failed SPD from the charging line of the power source (for example, see Patent Document 1).

[0006] Also, a current fuse for an SPD separator is known that can reduce the current that can be interrupted to a smaller value in response to a fault current caused by deterioration of the SPD (see, for example, Patent Document 2).

[0007] Furthermore, a mechanism is known that is composed of a circuit of multiple components including a voltage switching surge protective component (SPC), a resistive element, and a thermal fuse, and that cuts off the thermal fuse by utilizing the self-heating of the resistive element that occurs when a short-circuit current from the power supply flows through the resistive element (see, for example, Patent Document 3).

[0008] The performance of the SPD isolation device described above requires both low rated current performance and high surge current withstand performance. In other words, when an SPD fails, it is required from a safety perspective to quickly isolate the failed SPD from a healthy power system with as small a short-circuit current as possible, and from a lightning surge protection perspective to be able to protect the protected equipment even against high-level lightning surges.

[0009] However, when a fuse or breaker is used alone as an SPD isolation device, it is difficult to achieve both the conflicting requirements of low rated current performance and high surge current withstand performance because their performance is proportional to one another.

[0010] For example, the current fuse in Patent Document 1 has a rated current of 21 A and a maximum nominal discharge current (In) of 6.7 kA. However, considering that an SPD for general household use requires a maximum discharge current (Imax) of 10 kA, there is a demand for even greater surge current withstand capability.

[0011] In the case of Patent Document 2, the DC resistance of the fuse's fusible element is large, and the length of the fusible element is long, which suppresses heat dissipation toward the terminal and results in a fusing current of 30 A. However, considering that the minimum rated current of a breaker in an ordinary household is 15 A, there is a risk that the fuse and breaker will not cooperate with each other.

[0012] Furthermore, in the case of Patent Document 3, the operating mechanism uses the self-heating of a resistor when a short-circuit current of the power supply flows through the resistor in the event of an SPD failure, and cuts off the circuit with a thermal fuse. Therefore, it takes time for the resistor to heat up, for that heat to be transmitted to the thermal fuse, and for the temperature to rise to the point where the thermal fuse breaks, resulting in an issue of slow operation.

[0013] In this regard, an SPD isolation device or SPD is known that achieves both low rated current performance and high surge current withstand performance by connecting a surge protection component in parallel to a series circuit of a current breaker and a coil which is an impedance element (see Patent Documents 4 and 5).

[0014] However, in the cases of Patent Documents 4 and 5, a coil is used as an impedance element connected to the current breaker, so a large coil is required to obtain the necessary inductance, which poses a problem of overall large size. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] JP 2011-3350 A [Patent Document 2] JP 2014-36013 A [Patent Document 3] JP 2012-210009 A [Patent Document 4] JP 2012-65461 A [Patent Document 5] Japanese Utility Model Application Publication No. 54-6537 Summary of the Invention [Problem to be solved by the invention]

[0016] As described above, there is a demand for a surge protection device isolation apparatus that is compact and can achieve both a large surge current withstand capability and a small rated current capability.

[0017] The present invention has been made in consideration of the above points, and has an object to provide a surge protection device isolation apparatus that is compact and yet capable of achieving both large surge current withstand capability and small rated current capability. [Means for solving the problem]

[0018] The surge protection device isolation device described in claim 1 is a surge protection device isolation device connected in series to a surge protection device that protects a protected device against overvoltage surges, and comprises a series circuit of a current breaker and a resistor, and a voltage switching type surge protection component connected in parallel to this series circuit.

[0019] The surge protection device isolation device of claim 2 is the surge protection device isolation device of claim 1, in which the voltage switching type surge protection component does not operate below the power supply voltage, but operates when the sum of the voltage drops across the current breaker and resistor due to the surge current when a surge is applied reaches a predetermined voltage below the withstand voltage of the protected device.

[0020] The surge protection device isolation device of claim 3 is a surge protection device isolation device of claim 1 or 2, in which the current squared time product of the current breaker is greater than the current squared time product of the surge flowing through the current breaker before the voltage switching type surge protection component operates.

[0021] A surge protection device isolating apparatus according to claim 4 is the surge protection device isolating apparatus according to claim 1 or 2, wherein the current interrupter is a fuse or a breaker.

[0022] A surge protection device isolating apparatus according to claim 5, in which in the surge protection device isolating apparatus according to claim 1 or 2, the voltage switching type surge protection component is a gas-filled discharge tube or a surge protection thyristor. Effect of the Invention

[0023] According to the present invention, it is possible to achieve both a large surge current withstand capability and a small rated current capability while being compact. [Brief description of the drawings]

[0024] [Figure 1] 1 is a circuit diagram of a surge protection device isolation apparatus according to one embodiment; [Diagram 2] FIG. 2A is a circuit diagram showing an example of the surge protection device isolation apparatus, and FIG. 2B is a circuit diagram showing another example of the surge protection device isolation apparatus. [Diagram 3] 3A to 3D are graphs showing response characteristics of a simulation of a class III test in an embodiment based on the example of FIG. 2A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] An embodiment of the present invention will be described with reference to the drawings.

[0026] In Fig. 1, 1 denotes a surge protection device isolation apparatus (hereinafter referred to as isolation apparatus 1). The isolation apparatus 1 of this embodiment is an external isolation device that isolates a surge protection device 3 (hereinafter referred to as SPD 3) that protects a protected apparatus 2 from a transient overvoltage surge caused by a non-direct lightning strike that occurs when lightning strikes a low-voltage distribution system, or a part of the device, from the low-voltage distribution system in the event of a failure. A current breaker 4 is connected upstream of the low-voltage distribution system to which the isolation apparatus 1 is connected. The current breaker 4 is a device that isolates the protected apparatus 2 from the power supply side in the event of an abnormality. For example, a circuit breaker is used as the current breaker 4.

[0027] The protected device 2 may be, for example, an electric or electronic device. The protected device 2 has a predetermined withstand voltage. The power line of the protected device 2 is electrically connected to a charging line 5 and a neutral line 6 of a low-voltage power distribution system, and the ground terminal is electrically connected to a ground (earth) 8 via a ground line 7.

[0028] The SPD 3 is for low-voltage power distribution. The SPD 3 is typically composed of an internal separator 10, a metal oxide varistor 11 (hereinafter referred to as MOV 11), and a gas-filled discharge tube 12 (hereinafter referred to as GDT 12) in a series circuit, and usually has three terminals 13, 14, and 15.

[0029] The internal separator 10 may be, for example, a thermal isolation mechanism that uses heat generated when the MOV 11 fails to isolate the failed SPD 3 from the power supply system. The internal separator 10 may be, for example, a thermal fuse or an interruption mechanism using a contact opening mechanism that uses a low melting point metal and a spring. The internal separator 10 is, for example, intimately attached to the MOV 11 and integrated with it.

[0030] Terminal 13 is an external separator connection terminal electrically connected to the separation device 1. Terminal 14 is a ground connection terminal electrically connected to the ground 8. A series circuit of the internal separator 10, MOV 11, and GDT 12 is electrically connected between terminals 13 and 14. Furthermore, terminal 15 is a neutral conductor connection terminal electrically connected to the neutral conductor 6 of the power supply. The connection point between the MOV 11 and GDT 12 is electrically connected to terminal 15. Therefore, since the MOV 11 is connected between the charging line 5 and neutral conductor 6 of the power supply through the internal separator 10 and the separation device 1, it is in a charged state in which the voltage of the commercial power supply is constantly applied.

[0031] The separation device 1 is a device formed by combining a plurality of parts and devices. The separation device 1 is composed of a current breaker 20, a resistor 21, and a voltage switching surge protection component 22 (hereinafter referred to as SPC 22), and has two terminals 23 and 24.

[0032] The current interrupter 20 has an impedance. The current interrupter 20 is electrically connected to the terminal 23.

[0033] Moreover, the resistor 21 is electrically connected in series with the current breaker 20 to form a series circuit with the current breaker 20 between the terminals 23 and 24. In the present embodiment, the resistor 21 is electrically connected between the current breaker 20 and the terminal 24, but this is not limiting, and the resistor 21 may be electrically connected to the terminal 23, and the current breaker 20 may be electrically connected between the resistor 21 and the terminal 24. The SPC 22 is electrically connected in parallel between both ends of the series circuit of the resistor 21. That is, the SPC 22 is electrically connected between the terminals 23 and 24.

[0034] In this embodiment, the separation device 1 has a function in which the current breaker 20 is responsible for the small rated current function, the SPC 22 is responsible for the large surge current withstand function, and the resistor 21 is responsible for timing design to switch the path through which the surge current flows from the current breaker 20 to the SPC 22 when a surge current is applied.

[0035] That is, the SPC 22 does not operate below the voltage of the commercial power supply, and when a lightning surge is applied, a surge current first flows through the current breaker 20 and the resistor 21, and when the sum (total) of the voltage drops of each reaches the discharge start voltage of the SPC 22, which is a predetermined voltage below the withstand voltage of the protected device 2, the SPC 22 operates, transitioning to a low voltage state and the surge current flows as an arc current, thereby demonstrating the large surge current withstand characteristic of the SPC 22. In other words, the timing at which the SPC 22 operates in response to a lightning surge is determined according to the resistance value of the resistor 21. The surge current that has passed through the separation device 1 is released to the ground 8 via the SPD 3.

[0036] On the other hand, by designing the operating voltage of SPC22 to be higher than the peak voltage of the power supply in the power distribution system, even if MOV11 of SPD3 fails and becomes low impedance, SPC22 will not operate, and when the rated current of the power supply flows through current breaker 20, current breaker 20 will immediately perform an interruption operation to isolate the failed SPD3 from the power supply system, demonstrating a power supply current interruption characteristic.

[0037] In this manner, the separation device 1 of the present embodiment can have the large surge current withstand capability function provided by the SPC 22 and the small rated current capability provided by the current breaker 20 shared between them.

[0038] Here, when a lightning surge is applied, the current breaker 20 does not separate due to the lightning surge current, and in order to shunt the lightning surge current to the SPC 22, the current squared time product I 2 t (melting characteristic in the case of a fuse) is the current squared time product I 2 It is essential that the resistance is greater than t, and by making it larger, it is possible to withstand multiple surge currents.

[0039] In the example shown in FIG. 2(a), in the separation device 1a, the current breaker 20 is a current fuse 20a, and the SPC 22 is a GDT 22a.

[0040] When a current fuse 20a is used as the current breaker 20, there is no inoperable time and it can operate even in 10 ms or less, compared to using a breaker that is essentially unable to cut off at less than the half-wave frequency time of the applied AC power source (for example, 10 ms at 50 Hz), thereby increasing the operating speed.

[0041] Furthermore, by using resistor 21 as an impedance element that forms a series circuit with current breaker 20, separation device 1 can be made smaller than when a coil is used. For example, in a specific design example of SPD3 applied to a low-voltage distribution system, a surge withstand capability In=5kA, 8 / 20μs is required for "Class IISPD." If SPC 22 in separation device 1 is a GDT and its discharge start voltage is assumed to be 400V, then the required coil inductance L must be 400V / (5kV / 8μs)=0.64μH or more. Meanwhile, inductance L is expressed as follows, where a is the coil radius (m), b is the coil length (m), n is the number of coil turns, k is the Nagaoka coefficient, and μ 0 If the magnetic permeability of air is 1, then L=k×μ 0 ×π×a 2 ×n2 / b, and for inductances of 0.64 μH or more, the non-permeability μ 0 If we set is 1, then we would need a diameter of 2 cm, a length of 5 cm, and 10 turns (Nagaoka coefficient k = 0.8498517532738905), as shown below, which would result in a physically large shape.

[0042] L=0.8498517532738905×1×π×(0.01) 2 ×10 2 / 0.05=0.67μH When the GDT 22a is used as the SPC 22, the surge resistance of the separation device 1 can be increased by adopting one having a large surge resistance.

[0043] The example shown in Fig. 2(a) above is the most preferable combination of the current interrupter 20 and the SPC 22, which have characteristics that show excellent performance as the separation device 1, but is not limited to this combination. For example, in the example of a separation device 1b shown in Fig. 2(b), the current interrupter 20 is a breaker 20b, and the SPC 22 is a surge protection thyristor (Thyristor Surge Suppressor, TSS) 22b.

[0044] When the breaker 20b is used as the current interrupter 20, recovery after the breaker 20b operates can be performed quickly.

[0045] Furthermore, when the TSS 22b is used as the SPC 22, the operation speed can be increased compared to when the GDT is used.

[0046] In this way, the separation device 1 of this embodiment is small and yet has both a large surge current withstand capability and a small rated current capability. Therefore, the protected device 2 can be protected against a high-level lightning surge, and a faulty SPD 3 can be quickly separated from a healthy power system by a small short-circuit current. Furthermore, compared with an SPD separation device that uses a simple current fuse or the like, the separation device 1 of this embodiment has a faster separation operation. Therefore, when the SPD 3 fails, the current breaker 4 upstream of the SPD 3 does not operate to cut off the power supply to the protected device 2, ensuring the soundness of the normal power system and preventing the protected device 2 connected to this normal power system from being unnecessarily stopped.

[0047] It should be noted that the current breaker 20 and SPC 22 constituting the separation device 1 are not limited to those shown in these examples. For example, the current breaker 20 is not limited to a fuse, breaker, etc., and any part or device that functions as a current breaker may be used. Similarly, the SPC 22 is not limited to a GDT or TSS, so long as it is a part or device that functions as a voltage switching surge protection component. Furthermore, by freely combining these parts and devices, a separation device 1 that makes use of the characteristics of each part or device can be configured.

[0048] The separation device 1 can be applied not only to commercial AC power systems, but also to communication systems that similarly involve power supply. That is, the protected device 2 may be a communication device or the like.

[0049] An example of the embodiment shown in FIG. 2(a) will be described. In this example, the circuit constants are, for example, a rated current of the current fuse 20a, which is the current breaker 20, of 1 A, a fusing current squared time product I 2 t is 0.3A 2 The resistance of resistor 21 is 47 Ω, and the DC discharge starting voltage of GDT 22a, which is SPC 22, is 400 V.

[0050] With these circuit constants, the response characteristics of the circuit analysis simulation when applying a combination waveform of a current waveform of 8 / 20 μs, a voltage waveform of 1.2 / 50 μs, and a nominal discharge current In: 5 kA, which is the SPD3 Class III test combination waveform specified in JIS C 5381-11, are shown in Figure 3. Figure 3 shows the voltage and current waveforms in (a) the entire SPD separation device 1, (b) the GDT which is the SPC 22, (c) the current fuse which is the current breaker 20, and (d) the resistor 21.

[0051] The GDT, which is SPC22, discharges in 104 ns. The terminal voltages during discharge are GDT: 800 V, current fuse: 14 V, and resistor: 786 V.

[0052] In addition, the GDT has a DC discharge start voltage of 400V, but the discharge voltage in the surge response has Vt characteristics and rises when a steep waveform is applied. In this embodiment, the GDT discharges at approximately 800V, which is the sum of the voltage drops of the current fuse (14V) and resistor (786V), and after 104ns after discharge, most of the surge current flows through the GDT.

[0053] 3(c) and 3(d), a current flows through the current fuse 20a and resistor 21, which are the current breaker 20, until 104 ns when the GDT, which is the SPC 22, discharges, and the maximum current value is about 16.7 A. The current squared time product I 2 t is 2.9×10 ―5 A 2 s, and the fuse melting current squared time product I 2 The nominal value of t is 0.3A. 2 Since the current fuse 20a does not melt due to the surge current, the current squared time product I 2 The value of t varies with the level of the applied surge current.

[0054] Therefore, in the entire range of expected input surge currents, the current squared time product I 2The t value is the fuse melting current squared time product I 2 It is important to design it to be smaller than the nominal value of t.

[0055] In this embodiment, the surge current withstand capability of the separation device 1 is equal to the maximum discharge current withstand capability of the GDT used, and therefore, by this selection, a nominal discharge current In: 10 kA can be achieved.

[0056] On the other hand, when the SPD 3 fails, the short-circuit current of the power supply flows through the current fuse 20a, and the current fuse 20a melts down at a rated current of 1 A. The rated current of the current fuse 20a is smaller than 20 A, which is the minimum breaking capacity of the upper current breaker 4 installed in the power distribution system, and therefore sufficient operational coordination characteristics can be obtained.

[0057] In this manner, it was shown that this embodiment can achieve both the contradictory small rated current of 1 A and the large surge current resistance of 10 kA (8 / 20 μs). [Explanation of symbols]

[0058] 1 Surge protection device isolation device 2 Protected equipment 3. Surge protection devices 20 Current Breaker 21 Resistance 22 Voltage switching surge protection devices

Claims

1. A surge protection device isolation device connected in series with a surge protection device that protects a protected device against an overvoltage surge, comprising: A series circuit of a current breaker and a resistor; a voltage switching surge protection component connected in parallel to the series circuit; A surge protection device isolation apparatus comprising:

2. Voltage switching surge protection devices do not operate below the power supply voltage, but operate when the total voltage drop across the current breaker and resistor due to the surge current when a surge is applied reaches a specified voltage that is below the withstand voltage of the protected device.

2. The surge protection device isolation apparatus according to claim 1.

3. The current squared time product of a current breaker is greater than the current squared time product of the surge that flows through said current breaker before the voltage switching type surge protection component operates.

3. The surge protection device isolation apparatus according to claim 1 or 2.

4. The current interrupter is a fuse or a circuit breaker.

3. The surge protection device isolation apparatus according to claim 1 or 2.

5. The voltage switching surge protection component is a gas-filled discharge tube or a surge protection thyristor.

3. The surge protection device isolation apparatus according to claim 1 or 2.

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