JP2007288114A - Spd for direct lightning stroke - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exhibit a stabilized shielding performance against an excessive surge, even if there is a temperature rise by an electromagnetic energy or a self generation of heat by a large surge current due to a discharge energy. <P>SOLUTION: In an SPD for direct lightning stroke, a zinc oxide varistor 10 is connected between a pair of terminals 30a, 30b, and a separator 20 for separating the zinc oxide type varistor 10 and the terminal 30b, is connected between the zinc oxide type varistor 10 and one of the terminal 30b. The separator 20 is constituted of a temperature fuse 22 which is made of a low melting metal which is melted by a generation of heat by deterioration of the zinc oxide type varistor 10 and is not melted by the self generation of heat by the surge current a rated withstand current or less, and a separation conductor 24 which is separated at a marginal withstand current beyond the rated withstand current of the zinc oxide type varistor 10 connected with the temperature fuse 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a direct lightning SPD that incorporates a zinc oxide type varistor, and absorbs a surge voltage caused by a direct lightning strike with the zinc oxide type varistor to protect electrical equipment from the direct lightning strike.

  For example, in order to prevent lightning damage due to direct lightning strikes, a surge protection device (Surge Protective Device) is a device that shunts surge current by limiting transient overvoltage due to direct lightning strikes between electrical equipment and the ground in a single-phase AC circuit. : SPD) is installed. This direct lightning SPD includes a structure in which a zinc oxide varistor is incorporated.

  The zinc oxide varistor deteriorates with time depending on the input level when a surge due to a direct lightning strike is repeatedly input. When the zinc oxide varistor deteriorates, the leakage current increases and heat is generated, causing smoke and ignition due to thermal runaway. Moreover, due to the deterioration of the zinc oxide varistor, an excessive surge that greatly exceeds the rated withstand capacity of the zinc oxide varistor causes the zinc oxide varistor to short-circuit instantaneously and cause damage to surrounding electrical equipment.

  For this reason, it is desirable that the direct-current lightning SPD has a function to prevent smoke and ignition due to thermal runaway of the zinc oxide varistor and to prevent an instantaneous short circuit of the zinc oxide varistor due to an excessive surge exceeding the rated capacity. .

  Protective fuses for lightning protection devices have been proposed as a function to prevent smoke and ignition due to thermal runaway of this zinc oxide varistor and to prevent instantaneous short circuit of the zinc oxide varistor due to excessive surge exceeding the rated capacity. (For example, refer to Patent Document 1). This protective fuse combines a thermal fuse function that prevents smoke and fire due to thermal runaway of a zinc oxide varistor, and a current fuse function that prevents instantaneous short circuit of the zinc oxide varistor due to an excessive surge exceeding the rated capacity. is there.

In the direct lightning SPD with a built-in protective fuse disclosed in Patent Document 1, when the zinc oxide varistor deteriorates and the temperature rises due to self-heating, the protective fuse is blown to remove the zinc oxide varistor from the main circuit. I try to separate them. Also, when a surge current flows due to an excessive surge exceeding the rated withstand capacity, the protective fuse is blown to disconnect the zinc oxide varistor from the main circuit.
Japanese Patent Laid-Open No. 2003-197080

  By the way, in the conventional direct lightning SPD described above, a temperature fuse function that prevents smoke and ignition due to thermal runaway of the zinc oxide type varistor and a current fuse that prevents instantaneous short circuit of the zinc oxide type varistor due to an excessive surge exceeding the rated capacity. It has a built-in protective fuse that has both functions.

  However, the function of disconnecting the zinc oxide type varistor, that is, the temperature fuse function that prevents smoke and ignition due to thermal runaway of the zinc oxide type varistor, and the current fuse that prevents instantaneous short circuit of the zinc oxide type varistor due to excessive surge exceeding the rated capacity. When two protective functions are provided in one protective fuse, the mechanical strength of the protective fuse itself is low. Therefore, in the case of a surge current with a very high discharge energy such as a direct lightning SPD, electromagnetic force or The temperature rise due to self-heating may cause the protective fuse to melt even within the rated withstand capacity of the zinc oxide varistor, and it may be difficult to exert a stable breaking performance against an excessive surge.

  Therefore, the present invention has been proposed in view of the above-mentioned problems, and the object of the present invention is to prevent an excessive surge even if there is a temperature increase due to electromagnetic force or self-heating due to a very large surge current of discharge energy. An object of the present invention is to provide a direct lightning SPD capable of exhibiting stable blocking performance.

  As a technical means for achieving the above-mentioned object, the present invention connects a zinc oxide type varistor between a pair of terminals, between the zinc oxide type varistor and one of the terminals, and between the zinc oxide type varistor and the terminals. SPD for direct lightning with a separator that can be separated, and the separator is fused by heat generation due to deterioration of the zinc oxide varistor, and it is low melting that does not melt by self-heating with a surge current below the rated capacity It is composed of a thermal fuse made of metal and a separated conductor that is directly connected to the thermal fuse and separated by a limit tolerance exceeding the rated tolerance of the zinc oxide varistor.

  In the present invention, a thermal fuse made of a low-melting metal that is blown by heat generation due to deterioration of a zinc oxide type varistor and that is not blown by self-heating with a surge current less than the rated withstand voltage, and is directly connected to the thermal fuse, and zinc oxide The above-mentioned thermal fuse has a thermal fuse function that prevents smoke and ignition due to thermal runaway of the zinc oxide type varistor by configuring the separator with a separated conductor that is separated with a critical tolerance exceeding the rated capability of the type varistor. The aforementioned disconnected conductor is provided with a current fuse function for preventing an instantaneous short circuit of the zinc oxide varistor due to an excessive surge exceeding the rated withstand capability.

  With regard to the thermal fuse made of a low-melting metal with low mechanical strength and large strength variation by separating the thermal fuse function and the current fuse function from the thermal fuse function and the thermal conductor. Can be limited to only having a thermal fuse function, it becomes easy to select a thermal fuse having a sufficient mechanical strength, and it becomes easy to exhibit a stable breaking performance against an excessive surge.

  Further, according to the present invention, in the configuration described above, the zinc oxide varistor is accommodated in the sealed case and a pair of terminals are led out from the sealed case, and the temperature fuse of the separator is connected to the zinc oxide varistor side and disconnected. It is desirable to have a structure in which a conductor is connected to the terminal side, and a separator composed of a thermal fuse and a disconnected conductor is housed and disposed in a space adjacent to the zinc oxide varistor in the sealed case.

  In this way, if a thermal fuse is directly connected to a zinc oxide varistor, and the thermal fuse is housed in a space adjacent to the zinc oxide varistor in the sealed case, the heat generated by the deterioration of the zinc oxide varistor can be reduced. Efficient transmission to the thermal fuse is facilitated, and the temperature setting of the thermal fuse can be increased.

  Further, according to the present invention, in the configuration described above, the thermal fuse and the disconnecting conductor are arranged in a straight line, and the indicator is disconnected to the conductor via a spring that elastically biases the tensile force in a direction intersecting the disconnecting conductor. It is desirable to have a structure in which the indicator is displaced in the direction in which the tensile force is applied by the tensile force of the spring when either the thermal fuse is blown or the disconnected conductor is disconnected.

  In this way, the thermal fuse is disconnected or disconnected by energizing the conductor in the direction intersecting the direction in which the thermal fuse and the disconnecting conductor are arranged in a straight line, and displacing the indicator with the tensile force. By displaying the operation of one of the separations of the wires, if the tensile force is shared by the separated conductor with high mechanical strength, a large tensile force directly acts on the thermal fuse with low mechanical strength. Thus, normal operation of the thermal fuse can be ensured without applying undesired stress.

  According to the present invention, the two disconnecting functions consisting of the thermal fuse function and the current fuse function are separated from each other by the thermal fuse and the disconnecting conductor, so that the mechanical strength is low and the low-melting metal has a large strength variation. Since the thermal fuse can be limited to only having a thermal fuse function, it is easy to select a thermal fuse with sufficient mechanical strength, and it is easy to demonstrate stable shut-off performance against excessive surges. It is possible to provide a high-performance direct lightning SPD.

  In addition, if a thermal fuse is directly connected to the zinc oxide varistor and the thermal fuse is housed in a space adjacent to the zinc oxide varistor in the sealed case, the heat generated by the deterioration of the zinc oxide varistor can be removed. It becomes easy to efficiently transmit to the thermal fuse, and the temperature setting of the thermal fuse can be increased, and the design of the direct lightning SPD is facilitated.

  Further, the tensile force is disconnected and biased toward the conductor in a direction crossing the direction in which the thermal fuse and the disconnecting conductor are arranged in a straight line, and the indicator is displaced by the tensile force, so that the thermal fuse is blown or disconnected. By displaying the operation of either one of the two parts, if the tensile force is shared by the disconnected conductor with high mechanical strength, a large tensile force acts directly on the thermal fuse with low mechanical strength, and the The normal operation of the thermal fuse can be ensured without applying desired stress, and the reliability of the direct lightning SPD can be improved.

  FIG. 1 shows a basic circuit configuration of a direct lightning SPD according to an embodiment of the present invention.

  The direct lightning SPD of this embodiment includes a pair of terminals including a zinc oxide varistor 10 which is a lightning protection element mainly composed of ZnO and a separator 20 including a thermal fuse 22 and a disconnecting conductor 24 as shown in FIG. 30a and 30b are connected in series, and the separator 20 is connected to the separator 20 to notify the deterioration of the zinc oxide varistor 10 or the invasion of excessive surge by the separation operation of the zinc oxide varistor 10 by the separator 20. It has the structure connected to. In this direct lightning SPD, main components including a zinc oxide varistor 10 and a separator 20 including a thermal fuse 22 and a disconnecting conductor 24 are built in a resin-made sealed case 50 and connected to the separator 20. The display 40 is arranged in the window of the sealed case 50.

  2 is an exploded perspective view showing a direct lightning SPD in which the zinc oxide varistor 10 is built in the sealed case 50, and FIG. 3 is a front view showing a state where the lid 54 (see FIG. 2) of the sealed case 50 is removed. FIG. 4 is a schematic view showing a connection form of main components including the zinc oxide varistor 10 described above.

  The zinc oxide varistor 10 has a thin disk shape as shown in FIG. 2, and a pair of electrodes 12 and 14 (see FIG. 4) made of a conductive metal are joined to both front and back surfaces. One electrode 12 provided on the front surface side of the zinc oxide varistor 10 is partially cut to raise a tongue-like electrode lead-out portion 12a, and is provided on the back surface side of the zinc oxide varistor 10. The other electrode 14 has a tongue-like electrode lead-out portion 14a formed by cutting and raising a part of the other electrode 14 and bending it to the surface side. In this way, the pair of electrodes 12 and 14 are led out in the same direction on the surface side of the zinc oxide varistor 10 and the two electrode lead portions 12a and 14a are arranged, thereby facilitating wiring work in the sealed case 50. can do.

  As shown in FIG. 2, the sealed case 50 has a substantially rectangular shape, and a case main body 52 that houses main components including the separator 20 including the zinc oxide varistor 10, the thermal fuse 22, and the disconnecting conductor 24, and It is comprised with the cover body 54 which obstruct | occludes the opening part of the case main body 52. FIG.

  A partition wall portion 56 that is curved in a substantially circular shape is integrally provided on the peripheral wall portion of the case body 52 so as to surround the disk-shaped zinc oxide varistor 10. A plurality of slits 58 are formed at the bottom of the case body 52, and a concave spacer 51 having a peripheral edge bent in the depth direction of the case body 52 is accommodated and disposed. A gap is formed between the bottom portion. A pair of terminals 30 a and 30 b made of conductive metal are disposed at two corners of the case body 52. Each of the terminals 30 a and 30 b is a plate-shaped member formed by bending, and a base end portion is disposed in the vicinity of the partition wall portion 56, and a distal end portion is led out from the case main body 52.

  On the other hand, the lid body 54 includes a lid plate portion 54a having a shape that matches the opening shape of the case main body 52, and stop portions 54b that project from the four locations of the lid plate portion 54a in the thickness direction. The lid 54 is attached to the case main body 52 by closing the opening of the case main body 52 with the lid plate portion 54 a and hooking and locking the stopper 54 b to the recess 52 b on the outer periphery of the peripheral wall portion of the case main body 52. A sealed case 50 is formed.

  In addition, a large number of small holes 53 are formed in the lid plate portion 54a, and the above-mentioned small holes 53 are closed by adhering an adhesive sheet 55 to the portions where the small holes 53 are formed. 50 is formed. As a result, even if the internal pressure of the sealed case 50 rises due to metal evaporation when the thermal fuse 22 is melted or disconnected, the adhesive sheet 55 is partially peeled off and the small holes 53 are interposed. By absorbing the pressure increase, the sealed case 50 is prevented from bursting.

  In the direct lightning SPD, with the pair of terminals 30a and 30b attached to the case main body 52, the spacer 51 is accommodated in the bottom of the case main body 52, and the zinc oxide varistor 10 is placed in the partition wall 56. Store. By providing a gap between the spacer 51 and the case main body 52, the case main body 52 is prevented from being heated by heat from the zinc oxide varistor 10. Furthermore, in order to suppress the heating of the case main body 52, the slit 58 of the case main body 52 functions as a vent hole.

  In this state, a zinc oxide varistor 10 is embedded in the filler 60 by injecting a filler 60 such as silicone resin into the partition wall portion 56 in which the zinc oxide varistor 10 is accommodated. The filler 60 is preferably a silicone resin, but may be another material as long as it exhibits moisture resistance, flame retardancy, and a high insulating function.

  Of the pair of electrode lead portions 12a and 14a protruding from the filler 60 of the zinc oxide varistor 10, the electrode lead portion 14a led out from the back side electrode 14 of the zinc oxide type varistor 10 is attached to the case body 52. The terminal 30a is electrically and mechanically connected by screwing. Further, one end of the thermal fuse 22 is connected to the electrode lead portion 12 a led out from the surface side electrode 12 of the zinc oxide type varistor 10. The thermal fuse 22 has a rectangular parallelepiped shape made of, for example, a low melting alloy of bismuth and tin that melts at 138 ° C., and one end thereof is electrically and mechanically connected to the electrode lead portion 12a by screwing.

  The other end of the rectangular parallelepiped thermal fuse 22 is cut off by screwing and electrically and mechanically connected to one end of the conductor 24. The separating conductor 24 is formed of a strip-like thin plate made of copper, and a slit 24a is formed along the longitudinal direction thereof. The other end of the separation conductor 24 is electrically and mechanically connected to the other terminal 30b attached to the case body 52 by screwing.

  In this way, the thermal fuse 22 and the disconnecting conductor 24 are arranged in a straight line, and are installed in a state of being close to and substantially parallel to the surface of the filler 60. The disconnecting conductor 24 is provided with an indicator 40 that displays either the fusing of the thermal fuse 22 or the disconnecting of the disconnecting conductor 24 (see FIGS. 2 and 3).

  The indicator 40 has one end of a tension coil spring 42 fixed in the vicinity of a window 57 provided at one corner of the case main body 52, and a bar-like member 44 serving as an index for the coil portion 42a of the tension coil spring 42. Is inserted, and the base end portion of the rod-shaped member 44 is hooked and locked to the end portion of the coil portion 42 a of the tension coil spring 42, and the other end extending from the end portion of the coil portion 42 a is disconnected and connected to the conductor 24. The other end of the tension coil spring 42 is shaped like a bowl and connected to the slit 24a of the separation conductor 24 by being hooked and locked from a direction substantially perpendicular to the direction in which the separation conductor 24 extends.

  Thus, in the steady state where the tension coil spring 42 is disconnected and connected to the conductor 24, the distal end portion of the rod-shaped member 44 is in a state of being retracted by the window portion 57 of the sealed case 52. The elastic force of the tension coil spring 42 is biased in a direction orthogonal to the separation conductor 24, that is, in a direction in which the rod-shaped member 44 protrudes. As a result, the rod-shaped member 44 protrudes from the sealed case 50 by the action of the elastic force of the tension coil spring 42 by fusing the thermal fuse 22 or separating the cut-off conductor 24.

  FIG. 3 shows a state in which the tension coil spring 42 is disconnected and connected to the conductor 24, and the tip of the bar-shaped member 44, which is an indicator of the indicator 40, is retracted through the window 57 of the sealed case 52. 6 shows a state in which the rod-shaped member 44 protrudes from the sealed case 50 due to the action of the elastic force of the tension coil spring 42 due to the melting of the thermal fuse 22, and FIG. A state in which the rod-shaped member 44 protrudes from the sealed case 50 by the action of the elastic force 42 is shown.

  In this embodiment, the alarm contact 62 is disposed at a portion adjacent to the rod-shaped member 44 of the case body 52, and the switch portion 62 a of the alarm contact 62 is formed on the side of the rod-shaped member 44. By inserting and arranging in the recess 44a, when the thermal fuse 22 is melted or disconnected, the conductor 24 protrudes from the sealed case 50 by the action of the elastic force of the tension coil spring 42. The alarm contact 62 is turned on by moving the switch part 62a of the contact 62 for use.

  The direct lightning SPD of this embodiment includes a thermal fuse 22 made of a low-melting metal that is blown by heat generation due to deterioration of the zinc oxide varistor 10 and that is not blown by self-heat generation due to a surge current less than the rated withstand capability, and the thermal fuse The separator 20 is composed of a disconnecting conductor 24 that is directly connected to 22 and separated by a limit tolerance exceeding the rated tolerance of the zinc oxide varistor 10.

  Thus, a thermal fuse 22 made of a low-melting metal that is blown by heat generation due to deterioration of the zinc oxide varistor 10 and that is not blown by self-heating with a surge current below the rated withstand capability, and is directly connected to the thermal fuse 22, and By forming the separator 20 with the separated conductor 24 that is separated with a limit withstand capacity exceeding the rated withstand capacity of the zinc oxide varistor 10, a temperature fuse function that prevents fuming and ignition due to thermal runaway of the zinc oxide varistor 10 is provided. The above-described thermal fuse 22 is provided, and the above-described disconnected conductor 24 is provided with a current fuse function for preventing an instantaneous short circuit of the zinc oxide varistor 10 due to an excessive surge exceeding the rated withstand capability.

  Accordingly, by separating the two disconnecting functions consisting of the thermal fuse function and the current fuse function by the thermal fuse 22 and the disconnecting conductor 24, the thermal fuse made of a low-melting metal having low mechanical strength and large variation in strength. 22 can be limited to having only a thermal fuse function, it becomes easy to select the thermal fuse 22 having a sufficient mechanical strength, and it becomes easy to exhibit a stable breaking performance against an excessive surge.

  Further, in this direct lightning SPD, the zinc oxide varistor 10 is accommodated in the sealed case 50 and a pair of terminals 30a and 30b are led out from the sealed case 50, and the temperature fuse 22 of the separator 20 is connected to the zinc oxide varistor. The separator 20 is connected to the terminal side, the separator 24 is connected to the terminal side, and the separator 20 composed of the thermal fuse 22 and the separator conductor 24 is housed in a space m adjacent to the zinc oxide varistor 10 in the sealed case 50. (See FIG. 5).

  As described above, the thermal oxide 22 is directly connected to the zinc oxide varistor 10, and the thermal fuse 22 is housed and disposed in the space m adjacent to the zinc oxide varistor 10 in the sealed case 50. Thus, it becomes easy to efficiently transfer the heat generated by the deterioration of the thermal fuse 22 to the thermal fuse 22, and the temperature setting of the thermal fuse 22 can be increased.

  Further, in this direct lightning SPD, the thermal fuse 22 and the disconnecting conductor 24 are arranged in a straight line, and displayed via a spring 42 that elastically biases a tensile force in a direction orthogonal to the extending direction of the disconnecting conductor 24. The bar-like member 44 of the indicator 40 is connected to the disconnecting conductor 24, and the indicator 40 is moved in the direction of the action of the tensile force of the spring 42 when either the thermal fuse 22 is blown or the disconnecting conductor 24 is disconnected. It is made to protrude.

  In this way, the tensile force is cut in the direction perpendicular to the direction in which the thermal fuse 22 and the disconnecting conductor 24 are arranged in a straight line, the bias is applied to the conductor 24, and the indicator 40 is projected by the tensile force, thereby causing the thermal fuse 22 to protrude. By displaying the operation of either fusing or separation of the disconnected conductor 24, the tensile force is applied to the thermal fuse 22 having a low mechanical strength by sharing the tensile force with the disconnected conductor 24 having a high mechanical strength. It is possible to ensure normal operation of the thermal fuse 22 without directly acting and applying undesired stress.

It is a circuit diagram which shows the basic circuit structure of SPD for direct lightning strikes in embodiment of this invention. It is a specific structural example of a direct lightning SPD, and is an exploded assembly perspective view of the direct lightning SPD. It is a front view which shows the state which removed the cover body of the airtight case by the specific structural example of SPD for direct lightning strikes. It is a schematic diagram which shows the connection form of each main component including a zinc oxide type varistor. It is sectional drawing which shows the internal structure of an airtight case in the specific structural example of SPD for direct lightning strikes. It is a front view which shows the state which the indicator protruded by the melting of the thermal fuse in the state which removed the cover body of the airtight case. It is a front view which shows the state which the indicator protruded by the cutting-off of a cut-off conductor in the state which removed the cover body of the airtight case.

Explanation of symbols

10 Zinc Oxide Varistor 20 Separator 22 Thermal Fuse 24 Disconnected Conductor 30a, 30b Terminal 40 Display 50 Sealed Case m Space 42 Spring

Claims (3)

This is a direct lightning SPD in which a zinc oxide varistor is connected between a pair of terminals, and a separator capable of separating the zinc oxide varistor and the terminals is connected between the zinc oxide varistor and one of the terminals. And
The separator is blown by heat generation due to deterioration of the zinc oxide type varistor, and a thermal fuse made of a low melting metal that does not melt by self-heating with a surge current below the rated withstand voltage, and is directly connected to the thermal fuse, and SPD for direct lightning, characterized in that it is composed of a separated conductor separated by a limit withstand capability exceeding the rated withstand capability of a zinc oxide type varistor.   The zinc oxide varistor is housed in a sealed case and a pair of terminals are led out from the sealed case, the thermal fuse of the separator is connected to the zinc oxide varistor side, and the disconnecting conductor is connected to the terminal side, The SPD for a direct lightning strike according to claim 1, wherein a separator comprising a thermal fuse and a disconnecting conductor is housed and disposed in a space adjacent to the zinc oxide varistor in the sealed case.   The thermal fuse and the disconnecting conductor are arranged in a straight line, and an indicator is connected to the disconnecting conductor via a spring that elastically biases a tensile force in a direction crossing the disconnecting conductor, so that the thermal fuse is blown or The direct lightning SPD according to claim 1 or 2, wherein the indicator is displaced in the acting direction of the tensile force by the tensile force of the spring during the operation of any one of the separation conductors.

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