JP2014155340A - Surge protection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a casing from being damaged by inner pressure increase by preventing a thermal separation mechanism or a current fuse from being made dirty by smoke generation from a thermally separated varistor.SOLUTION: A surge protection apparatus comprises thermally separated varistors MOV1 of which one-side electrodes are connected via a contact part 21 to a positive-side terminal and a negative-side terminal connected to a DC power supply line. The varistor MOV1 includes a thermal separation mechanism for cutting a current which flows in the varistor MOV1 by switching the contact part 21 from its own electrode 301 to a current fuse side in the case of heating. The thermal separation mechanism including the contact part 21 is enclosed by a heat-resistant first isolation cover 701 so as to be isolated from the thermally separated varistor MOV1. A second isolation cover 702 or a casing 200 for isolating a plug substrate 101 includes a thin portion and a lid part as needed.

Description

  The present invention relates to a surge protection device for protecting a system from a lightning accident, for example, connected to a DC power line in a photovoltaic power generation system.

FIG. 6 is a configuration diagram showing a main part of the photovoltaic power generation system.
In FIG. 6, A is a solar panel, and B is a power conditioner composed of an inverter or the like for converting the DC output voltage of the solar panel A into an AC voltage.
D is a surge protection device (SPD) connected to the DC power supply line C between the solar panel A and the power conditioner B. When lightning strikes the power supply line C, lightning surge current flows to the ground side and sunlight This prevents failure, destruction, or damage to the panel A or power conditioner B.

FIG. 7 is a circuit diagram showing an example of a conventional surge protection device. Here, the surge protection device is indicated by reference numeral D1.
In FIG. 7, DC + is a positive terminal connected to the DC power supply line C, DC− is a negative terminal, E is a ground terminal, 11, 12 and 13 are cables, MOV1, MOV2 and MOV3 are zinc oxide varistors (hereinafter referred to as the following). 21, 22, and 23 are contact portions that are disconnected by operating a heat separation mechanism such as a leaf spring or a thermal fuse due to heat generated by a short circuit failure or the like of the varistors MOV 1, MOV 2, and MOV 3.

The operation of this prior art will be described below. During a lightning strike, a lightning surge current flows through the varistor between the DC power line C and the grounding point E. Therefore, the lightning surge current does not flow into the solar panel A, the power conditioner B, etc. Protected from lightning strikes.
In addition, when the varistor is short-circuited due to aging or the like, the varistor generates heat due to the short-circuit current, the heat separation mechanism operates, and the contact portion is turned off, so that the varistor is disconnected from the DC power supply line C. Thereby, it is possible to prevent the varistor itself and peripheral circuits from being burned out.
However, when the voltage of the DC power supply line C is high, an arc generated when the contact portion is turned off remains without being extinguished, and there is a possibility that the flow to the varistor and the heat generation are continued.

Next, FIG. 8 is a circuit diagram showing another prior art, and a surge protection device is indicated by reference numeral D2.
In this prior art, current fuses F1 and F2 are connected in parallel to the varistors MOV1 and MOV2. When the varistors MOV1 and MOV2 generate heat, the contact points 21 and 22 are switched to the current fuses F1 and F2 side to generate an arc. The arc is extinguished.

In Patent Document 1, a low melting point metal alloy plate is attached to a terminal of a varistor so that the low melting point metal alloy plate is operated as a temperature fuse or a current fuse when the varistor fails or deteriorates so that the varistor is disconnected from the power supply circuit. A lightning protection device is described.
In Patent Document 2, a lead conductor and a spring material are fixed to the surface of a varistor with an adhesive, and a single copper wire including a fixed conductor portion, a current fuse portion and a temperature fuse portion is formed on the lead conductor. A varistor device in which a current fuse portion is urged by the spring material is described.
Further, Patent Document 3 describes a lightning arrester in which a heat separation mechanism including a spring is operated by heat generated by a varistor to short-circuit both ends of the varistor.

JP 2006-179842 A (paragraphs [0017] to [0026], FIG. 5 and the like). JP 2007-42753 A (paragraphs [0024] to [0035], FIG. 3 and the like). JP-T-2010-503163 (paragraphs [0026] to [0028], FIGS. 1 to 3 etc.).

  In the prior art shown in FIG. 8, some of the current fuses F1 and F2 are not blown up to, for example, 2 [A]. , F2 continues to flow until the current flowing through F2 reaches the fusing current value. For this reason, as a result of applying a high DC power supply voltage to both ends of the remaining varistor MOV3, the arc is not extinguished when the contact portion 23 is disconnected by the heat separation mechanism, and the varistor MOV3 continues to generate heat. In the worst case, there was a problem that the insulating resin melted and the terminal was exposed.

In addition, there is a possibility that smoke ejected from the varistor that has generated heat enters a heat separation mechanism including a movable part such as a contact part, thereby fouling the mechanism, or the gas pressure inside the casing is increased to damage the casing.
In addition, in the prior art which concerns on patent documents 1-3, the various solution solution resulting from the heat_generation | fever, smoke generation, etc. of a varistor as mentioned above is not shown.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a surge protection device that prevents the heat separation mechanism from being soiled by the smoke generated from the varistor and prevents the casing from being damaged due to an increase in internal pressure.

In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a protected device connected between a DC power line and a grounding point by means of a varistor connected in parallel to the protected device. A surge protection device for protecting against a surge, wherein the varistor is provided with a thermal separation type varistor having a thermal separation mechanism that cuts off a current flowing through the varistor by switching the contact portion from its own electrode to the current fuse side when the varistor generates heat. In the configured surge protection device,
The thermal separation mechanism including the contact portion is surrounded by a heat-resistant isolation cover and isolated from the thermal separation varistor.

  According to a second aspect of the present invention, in the surge protection device according to the first aspect, when the gas pressure in the casing is increased in the casing surrounding the thermal separation type varistor and the isolation cover in a sealed state, It is characterized in that it is provided with a portion such as a thin portion or a lid that is opened by gas pressure.

  According to a third aspect of the present invention, in the surge protection device according to the first or second aspect, the printed circuit board on which the thermal isolation varistor and the current fuse are mounted is surrounded by an isolation cover different from the isolation cover. It is characterized by that.

  The invention according to claim 4 is the surge protection device according to any one of claims 1 to 3, wherein the thermal separation mechanism melts the low melting point metal when the thermal separation varistor generates heat. The contact portion is separated from one electrode of the thermal separation varistor and is connected to the terminal portion of the current fuse by a restoring force of a spring.

  According to a fifth aspect of the present invention, in the surge protection device according to any one of the first to fourth aspects, between the contact portion and one electrode of the thermal separation type varistor during the operation of the thermal separation mechanism. It is characterized by having a blocking block for blocking the space.

  The invention according to claim 6 is the surge protection device according to any one of claims 1 to 5, wherein the contact portion is separated from one electrode of the thermal separation type varistor during operation of the thermal separation mechanism. It is characterized by having a state display unit indicating that the above has been performed.

  The invention according to claim 7 is the surge protection device according to any one of claims 1 to 6, wherein the contact portion is separated from one electrode of the thermal separation type varistor during operation of the thermal separation mechanism. A switch is provided for outputting an alarm signal indicating that this has occurred to the outside.

  According to an eighth aspect of the present invention, in the surge protection device according to the seventh aspect, the switch is turned on in conjunction with the blocking block according to the fifth aspect.

According to the present invention, the heat separation mechanism including the contact portion that contacts and separates from the electrode of the thermal separation varistor is surrounded by the heat-resistant isolation cover and is isolated from the thermal separation varistor, so that the smoke from the varistor due to heat generation is generated. And harmful gases can be prevented from entering the heat separation mechanism and being contaminated.
In addition, the casing that encloses the thermal separation varistor and the isolation cover in a sealed state is provided with a portion such as a thin-walled portion or a lid portion that breaks or scatters when the internal pressure of the casing increases, thereby damaging the entire casing. It is possible to release the internal high-pressure gas to the outside in the previous stage. Furthermore, if the printed circuit board on which the thermal isolation varistor and the current fuse are mounted is surrounded by another isolation cover, the current fuse and other components mounted on the printed circuit board can be protected.

It is a circuit diagram showing an embodiment of the present invention. It is an internal structure figure of the principal part of the embodiment of the present invention. It is an internal structure figure of the principal part of the embodiment of the present invention. In embodiment of this invention, it is a figure which shows the structure for releasing the high pressure gas in a casing outside. In embodiment of this invention, it is a figure which shows the structure for releasing the high pressure gas in a casing outside. It is a block diagram which shows the principal part of a solar power generation system. It is a circuit diagram which shows a prior art. It is a circuit diagram which shows another prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a circuit diagram of a surge protection device D according to the present embodiment, and the same components as those in FIG. 8 are denoted by the same reference numerals. This surge protection device D is connected in parallel to the solar panel A and the power conditioner B, which are protected devices, as shown in FIG.

In FIG. 1, as in FIG. 8, DC + is a positive terminal on the DC power supply line C side, DC− is a negative terminal, E is a ground terminal, 11, 12, and 13 are cables, MOV1, MOV2, and MOV3a are zinc oxide. The varistors 21 and 22 are contact portions that are switched by the operation of a thermal separation mechanism such as a leaf spring or a thermal fuse by the heat generated by the varistors MOV1 and MOV2 that are short-circuited.
In this embodiment, the varistor MOV3a is not provided with a heat separation mechanism. For this reason, in this embodiment, the varistors MOV1 and MOV2 having a thermal separation mechanism are also referred to as thermal separation varistors, and the varistor MOV3a having no thermal separation mechanism is also referred to as a non-thermal separation varistor.

  This embodiment differs from FIG. 8 in that the other end of the current fuse F1 whose one end is connected to the switching destination of the contact portion 21 is connected to the negative terminal DC−, and one end is connected to the switching destination of the contact portion 22. The other end of the current fuse F2 is connected to the positive terminal DC +, and the non-thermally separated varistor MOV3a is connected between the connection point between the thermally separated varistors MOV1 and MOV2 and the ground terminal E. It is.

Next, FIG. 2 is an internal structural diagram of the main part of the present embodiment, and is for explaining the varistor MOV1 in FIG. 1 and its heat separation mechanism. FIG. 2 shows a normal state of the varistor MOV1.
The structure of the varistor MOV2 in FIG. 1 and its heat separation mechanism are also the same.

In FIG. 2, a varistor MOV1 is molded inside a casing 200 inside a partition wall 202 formed of a heat resistant resin. The terminal portion 302 of the varistor MOV1 is fixed to the plug substrate (printed substrate) 101 in the second isolation cover 702 made of heat resistant resin. Although not shown, the current fuse F1 of FIG. 1 is also mounted on the plug substrate 101.
One electrode 301 is disposed on the side surface of the varistor MOV1, and the contact portion 21 is fixed to the electrode 301 via a low melting point metal (hereinafter referred to as low melting point solder).

The contact portion 21 is formed integrally with the upper end portion of the heat separating plate 401 made of a conductive spring material, and the lower end portion of the heat separating plate 401 surrounds the heat separating mechanism including the contact portion 21 and the like. 1 is connected to the positive terminal DC + of FIG. 1 on the plug substrate 101 through the first isolation cover 701 and the second isolation cover 702. The heat separating plate 401 is always urged in the direction in which the contact portion 21 is pulled away from the electrode 301 by the restoring force of the spring material.
A terminal portion 403 of the current fuse F1 in FIG. 1 is disposed at the destination of the contact portion 21 that is separated from the electrode 301. As described above, the current fuse F1 is mounted on the plug substrate 101. A step portion 402 is formed at the base of the contact portion 21 of the heat separation plate 401.

A state display portion 501 is disposed above the contact portion 21 that is fixed to the electrode 301. The state display unit 501 includes display surfaces 504 and 505 that can rotate around a rotation shaft 503 around which a torsion spring 502 is wound. One display surface 504 is colored in green, for example, “normal”. The other display surface 505 is colored, for example, in red to display “failure (abnormal)”. A part of the casing 200 facing the display surface 504 forms a display window 201 with a transparent material.
Further, a locking projection 506 that locks the contact portion 21 is formed at the lower end of the status display portion 501, and the status display portion 501 is rotated clockwise by the restoring force of the torsion spring 502. Always energized.

A blocking block 601 that is always urged upward by coil springs 603 and 606 is disposed on the side of the heat separation plate 401. The blocking block 601 includes a blocking plate 602 that contacts the stepped portion 402 of the heat separation plate 401 from below, and a rod 604 that extends below the blocking plate 602. The rod 604 includes a second isolation cover 702 and a plug. It extends downward through the substrate 101.
Reference numeral 102 denotes a switch substrate on which a microswitch 801 is mounted. A switch button 802 of the micro switch 801 is pushed by a switch lever 803, and a tip end portion of the switch lever 803 is locked to a locking rod 605 at the lower end portion of the rod 604. Here, other types of switches other than the micro switch 801 may be used.
The first isolation cover 701 isolates the entire thermal separation mechanism including the electrode 301, the contact portion 21, the thermal separation plate 401, the shielding plate 602, the status display portion 501, the terminal portion 403, and the like from the varistor MOV1. Besieged.

  The varistor MOV1, the heat separation mechanism thereof, the fuse F1, and the like configured as described above are housed in a sealed state in the casing 200 as a set, thereby forming a plug-in type surge protection element.

Next, the operation of this embodiment will be described with reference to FIGS. As described above, FIG. 2 shows the normal state of the varistor MOV1, and FIG. 3 shows the state of the main part when the varistor MOV1 is short-circuited due to aging or the like.
When the varistor MOV1 shown in FIG. 2 is normal, the DC voltage of the DC power supply line C is applied to the series circuit of the varistors MOV1 and MOV2. The protected device is protected by the series circuit.

  Next, in the state of FIG. 2, for example, when the varistor MOV1 is short-circuited, the electrode 301 generates heat and the low melting point solder melts. As a result, the contact portion 21 urged in the direction of being separated from the electrode 301 by the restoring force of the heat separation plate 401 is opened and switched to contact the terminal portion 403 of the current fuse F1 as shown in FIG. Therefore, as shown in FIG. 1, the positive side terminal DC + of the surge protection device D is connected to the negative side terminal DC− through a series circuit of the contact portion 21 and the current fuse F1.

As shown in FIG. 3, in a state where the contact portion 21 is separated from the electrode 301, the state display portion 501 is rotated clockwise by the restoring force of the torsion spring 502, and for example, a red display surface 505 is displayed on the display window. It becomes a state which can be visually observed through the part 201. For this reason, it can be easily confirmed from the outside that the contact portion 21 has been separated from the electrode 301 due to a short circuit failure of the varistor MOV1.
At the same time, the blocking plate 602, which is normally regulated by the step portion 402, moves upward by the restoring force of the coil springs 603 and 606 and blocks the space between the contact portion 21 and the electrode 301. The arc continuity is surely extinguished even if it occurs.

  Further, since the blocking plate 602 and the rod 604 move upward due to the restoring force of the coil spring 606, the locking rod 605 formed at the lower end of the rod 604 pushes up the switch lever 803 of the micro switch 801, whereby the switch button 802. Is pressed. For this reason, it is possible to output an alarm (contact signal) indicating that the contact portion 21 has been separated from the electrode 301 from the micro switch 801.

As described above, according to this embodiment, the contact portion 21 is separated from the electrode 301 by the heat generated by the varistor MOV1 and is switched to the terminal portion 403 of the current fuse F1, so that the contact portion 21 and the electrode 301 are separated from each other. Generation of an arc is prevented, and the circuit current flows from the positive terminal DC + to the negative terminal DC− through the contact portion 21 and the current fuse F1. Similarly, even when the varistor MOV2 generates heat due to a short-circuit failure, arcing between the contact 22 and the varistor MOV2 is prevented, and the circuit current passes through the current fuse F2 and the contact 22 from the positive terminal DC +. Through the negative terminal DC−.
Therefore, even when a circuit current equal to or lower than the fusing current value flows through the current fuse F1 or F2 when the thermal separation mechanism of the thermal isolation varistor MOV1 or varistor MOV2 is operated, the circuit current is non-thermally isolated varistor MOV3a. Therefore, the varistor MOV3a can be prevented from being heated and burned out.

  In addition, even if smoke or harmful gas is generated from the heat separation type varistor MOV1 (or MOV2) due to heat generation, the electrode 301, the contact portion 21, the heat separation plate 401, the shielding plate 602, and the status display portion 501 Since the heat separation mechanism including the terminal portion 403 and the like is surrounded by the first isolation cover 701 and isolated from the varistor MOV1, there is no fear that smoke particles or harmful gases may contaminate these components. In addition, since the plug substrate 101 on which the varistor MOV1 and the current fuse F1 are mounted is also surrounded by the second isolation cover 702, the wiring pattern and circuit components on the plug substrate 101 are protected from smoke particles and harmful gases. can do.

As the varistor MOV1 generates heat, the internal pressure of the casing 200 that encloses the varistor MOV1 and the heat separation mechanism in a sealed state may increase due to the gas. For example, the structure shown in FIGS. 4 and 5 is adopted. By doing so, the high-pressure gas can be discharged to the outside, and the entire surge protection device can be prevented from being damaged.
That is, FIG. 4A shows a structure in which a thin portion 203 is provided on the side surface portion of the casing 200, and the thin portion 203 is broken by the internal gas pressure to discharge high-pressure gas to the outside as shown in FIG. 4B. 5 (a), the lid portion 204 is fitted into the side surface or upper portion of the casing 200, and the lid portion 204 is scattered by the internal gas pressure as shown in FIG. 5 (b) to release the high-pressure gas to the outside. It is a structure to let you.
The numbers and positions of these thin portions 203 and lid portions 204 are not limited to the illustrated examples.

In the above-described embodiment, the microswitch 801 is turned on and the alarm is output to the outside during the operation of the heat separation mechanism, but these alarm output means (rod 604, locking rod 605, microswitch 801, etc.) It is not essential to the invention.
Similarly, even if the state display unit 501 is not provided, there is no problem in solving the problem of preventing the varistor MOV3a from generating heat and burning.

A: Solar panel B: Power conditioner C: DC power line D: Surge protection device DC +: Positive terminal DC-: Negative terminal E: Ground terminal MOV1, MOV2, MOV3a: Zinc oxide varistor F1, F2: Current fuse 11 , 12, 13: Cables 21, 22: Contact part 101: Plug board 102: Switch board 200: Casing 201: Display window part 202: Partition 203: Thin part 204: Lid part 301: Electrode 302: Terminal part 401: Thermal separation Plate 402: Step portion 403: Terminal portion 501: Status display portion 502: Torsion spring 503: Rotating shaft 504, 505: Display surface 506: Locking projection 601: Blocking block 602: Blocking plate 603, 606: Coil spring 604: Rod 605: Locking rod 701: First isolation cover 702: Second isolation cover 01: micro-switch 802: switch button 803: switch lever

Claims (8)

A surge protection device that protects a protected device connected between a DC power line and a ground point from a lightning surge by operation of a varistor connected in parallel to the protected device, wherein the varistor is In the surge protection device composed of a thermal separation type varistor with a thermal separation mechanism that cuts off the current flowing through the varistor by switching the contact part from its own electrode to the current fuse side during the heat generation,
A surge protection device comprising a heat isolation mechanism including the contact portion surrounded by a heat-resistant isolation cover and isolated from the heat isolation varistor. In the surge protection device according to claim 1,
A surge protection device comprising a casing that encloses the thermal separation varistor and the isolation cover in a sealed state, and a portion that is opened by the gas pressure when the gas pressure in the casing increases. In the surge protection device according to claim 1 or 2,
A surge protection device, wherein a printed circuit board on which the thermal isolation varistor and the current fuse are mounted is surrounded by an isolation cover different from the isolation cover. In the surge protection device according to any one of claims 1 to 3,
The thermal separation mechanism melts a low melting point metal when the thermal separation varistor generates heat, thereby separating the contact portion from one electrode of the thermal separation varistor, and by the restoring force of a spring, the current fuse A surge protection device that is connected to the terminal. In the surge protection device according to any one of claims 1 to 4,
A surge protection device comprising: a blocking block that blocks a space between the contact portion and one electrode of the thermal separation varistor during operation of the thermal separation mechanism. In the surge protection device according to any one of claims 1 to 5,
A surge protection device comprising a state display unit indicating that the contact portion is separated from one electrode of the thermal separation type varistor during operation of the thermal separation mechanism. In the surge protection device according to any one of claims 1 to 6,
A surge protection device, comprising: a switch for outputting an alarm signal indicating that the contact portion is separated from one electrode of the thermal separation varistor during operation of the thermal separation mechanism. The surge protection device according to claim 7,
A surge protection device, wherein the switch is turned on in conjunction with the blocking block according to claim 5.

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