JP2008295254A - Lightning arrester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightning arrester having a detection mechanism which detects rightly existence or non-existence of an abnormality of a lightening element, even at generation of an excessive surge. <P>SOLUTION: The lightening element 13 is connected between a voltage wire L and a neutral wire N through fuses 11, 12. When deterioration of characteristics is generated in the lightening element 13, the fuses 11, 12 disconnect the lightening element 13 from the voltage wire L and the neutral wire N. A primary side of a power transformer 16 is connected to the voltage wire L and the neutral wire N through the fuses 11, 12. If one or both of the fuses 11, 12 melt, a voltage of the primary side of the power transformer 16 is lost, and a voltage of a secondary side is also lost. As the voltage of the secondary side is lost, a relay 18 stops operating, and a break contact 18b turns on, then an alarm indicating that the abnormality of the lightening element is detected is output. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lightning arrester, and more particularly to a lightning arrester having means for detecting deterioration of characteristics of a lightning arrester.

  A lightning arrester is a device that protects a power device from an abnormal voltage caused by lightning. The lightning arrester constituting the lightning arrester is subjected to repeated lightning surge absorption and long-term use, resulting in characteristic deterioration. When characteristic deterioration occurs in the lightning arrester, the leakage current flowing through the lightning arrester increases and the element generates heat, which may lead to an abnormal heat generation state of the lightning arrester. Therefore, the lightning arrester is provided with means for detecting deterioration of the lightning arrester. When the deterioration of the lightning arrester is detected, an external alarm is issued to promote replacement of the lightning arrester, or the deteriorated lightning arrester is disconnected to avoid an abnormal heat generation state of the lightning arrester.

In order to separate the deteriorated lightning arrester from the power line, a fuse that is blown when the characteristics of the lightning arrester deteriorates is usually used. As a means for detecting blown fuses in the related art, there is one that inserts a photocoupler between the voltage line L and the neutral line N (see, for example, Patent Document 1). In addition, as another means for detecting blown fuses, there is a method in which a photocoupler is provided between power lines via a rectifier (see, for example, Patent Document 2). In any case, when the fuse is blown, the power supply to the photocoupler is interrupted and the external light emitting element is turned off by an external signal to generate an alarm.
JP-A-2005-316881 JP 2002-238110 A

  However, in the configuration of the related art, the photocoupler and the rectifier may be damaged by an excessive surge that is transmitted at the rising time of the wavefront length at which the lightning protection element cannot respond. Further, an alarm may be sent out even though the lightning protection element and the fuse are normal due to damage to the alarm sending photocoupler. On the other hand, the alarm may not be sent even though the lightning arrester is abnormal or the fuse is blown. Even if an alarm is sent, the lightning arrester will not be mounted after the fuse is blown, so if the next induced lightning surge is applied before the arrester is replaced, the induced lightning surge will enter the subsequent stage. As a result, there is a risk of damage to subsequent devices.

  Further, in the configuration using the rectifier, there is a problem that the cost of parts is increased and the risk of electric shock is increased by converting the AC voltage into the DC voltage. That is, the DC voltage generated by the rectifier is a value of about 1.4 times the AC voltage, for example, if the AC voltage is 200V, the DC voltage is 280V. Therefore, it is necessary to pay attention to electric shock when handling. In addition, it is necessary to select a high-voltage component for the rectifier and the subsequent stage, which leads to an increase in cost.

  An object of the present invention is to provide a lightning arrester having a detection mechanism that can correctly detect the presence or absence of an abnormality of a lightning arrester even when an excessive surge occurs.

  In order to achieve the above object, a lightning arrester of the present invention comprises a lightning arrester inserted between power lines, a disconnecting means for separating the lightning arrester from the power line when the characteristics of the lightning arrester are deteriorated, and a primary side, A transformer connected to the power supply line via a disconnecting means; and an abnormality detecting means connected to a secondary side of the transformer and detecting an abnormality of the lightning protection element based on the presence or absence of a secondary voltage. And

  The lightning arrester of the present invention includes a first lightning arrester inserted between a first power supply line and a second power supply line, and a first lightning arrester inserted between a third power supply line and the second power supply line. Second lightning protection element, a third lightning protection element inserted between the first power supply line and the third power supply line, and the first to third lightning protection elements when the characteristics deteriorate. Disconnecting means for disconnecting the first to third lightning arresters from the first and second power supply lines, a transformer having a primary side connected to the first and second power supply lines via the disconnecting means, and the transformer And an abnormality detecting means for detecting an abnormality of the first to third lightning arresters based on the presence or absence of a secondary voltage.

  With the lightning arrester of the present invention, it is possible to correctly detect the presence or absence of abnormality of the lightning arrester even when an excessive surge occurs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a power supply configuration to which the lightning arrester of the first embodiment of the present invention is applied. The voltage line is composed of a voltage line L (Live), a neutral line N (Neutral), and a ground wire FG (Frame Ground) single-phase 2 wire and a ground wire. The power device 50 is supplied with AC power via a voltage line L (first power line), a neutral line N (second power line), and a ground line FG (third power line). The power device 50 converts, for example, supplied AC power into DC power and supplies power to a device or a board (not shown). The voltage line L and the neutral line N are provided with a breaker 40 having a function of interrupting when an excessive current flows. The lightning arrester 10 is connected to a voltage line L, a neutral line N, and a ground line FG between the power receiving end and the breaker 40. The lightning arrester 10 has a structure that can be easily replaced when a failure or the like occurs.

  FIG. 2 shows a detailed configuration of the lightning arrester 10. The lightning arrester 10 includes fuses 11 and 12, regular lightning protection elements (first to third lightning protection elements) 13, 14, and 15, power transformer 16, relay 18, and spare lightning protection elements (fourth and fifth lightning protection elements). Element) 19 and 20. The fuses 11 and 12 are temperature fuses that blow when a predetermined temperature is exceeded. One end of the lightning protection element 13 is connected to the voltage line L via the fuse 11, and the other end is connected to the neutral line N via the fuse 12. One end of the lightning protection element 14 is connected to the neutral line N via the fuse 12, and the other end is connected to the ground line FG. One end of the lightning protection element 15 is connected to the voltage line L via the fuse 11, and the other end is connected to the ground line FG.

  The lightning arrester 13 clamps the voltage between the voltage line L and the neutral line N to a predetermined voltage when an induced lightning surge enters. The lightning arrester 14 clamps the voltage between the neutral line N and the ground line FG to a predetermined voltage when an induced lightning surge enters. The lightning arrester 15 clamps the voltage between the voltage line L and the ground line FG to a predetermined voltage when an induced lightning surge enters. As the lightning protection elements 13 to 15, a varistor voltage of 470 V (in the case of AC 100 to 200 V) is generally used with a varistor having a high response speed. In this case, if the induced lightning surge voltage is about 4 KV, each clamp voltage of the lightning protection elements 13 to 15 is about 650V. The varistor voltage is a voltage at both ends when current starts to flow. The clamp voltage is a voltage at both ends when a large current flows, and tends to increase in proportion to the flowing current.

  The lightning arresters 13 to 15 are deteriorated in characteristics due to repeated induction lightning surges and long-term use, and leakage current increases to generate heat. The lightning arrester 10 has a structure in which the heat generated by the lightning arresters 13 to 15 is effectively conducted to the thermal fuses 11 and 12. The thermal fuses 11 and 12 have a characteristic that they are not blown by an excessive induced lightning surge and are blown by heat generated when the characteristics of the lightning arresters 13 to 15 are deteriorated. When the fuses 11 and 12 are blown, the lightning arrester having deteriorated characteristics is disconnected from the voltage line L and the neutral line N.

  The primary side of the power transformer 16 is connected to the voltage line L and the neutral line N via the fuses 11 and 12. Further, a drive unit (coil) of the relay 18 is connected to the secondary side of the power transformer 16 via a resistor 17 for current limitation. The relay 18 is a small voltage AC relay. The small voltage AC is a low voltage AC such as 24V AC. Miniaturized power transformers and AC24V relays are commercially available. As the relay 18, for example, an AC 24V relay with which a relay contact can withstand a surge current of about 300 A (time 700 μs) is used.

  FIG. 3 shows the configuration of the power transformer 16. The winding ratio of the power transformer 16 is N: 1 (primary side: secondary side), where N is a natural number, and the power transformer 16 determines the voltage between the voltage line L and the neutral line N as 1 / Set to N and output. By increasing the turn ratio N: 1, the secondary voltage can be lowered and the relay 18 can be driven at a low voltage. For example, when the voltage between the voltage line L and the neutral line N is AC100V, the secondary side of the power transformer 16 becomes AC25V if the turns ratio is 4: 1. The power transformer 16 includes a coil and a core, and does not use parts that deteriorate due to an excessive surge. In addition, the cost is low. The power transformer 16 has a function of reducing the surge applied to the primary side to about 1/100 on the secondary side because the primary side and the secondary side are insulated.

  Returning to FIG. 2, the relay 18 has two break contacts (18a, 18b). The break contacts 18a and 18b open when a predetermined voltage, for example, 25V appears on the secondary side of the power transformer 16, and close the contact when no voltage appears. One end of the spare lightning protection elements 19 and 20 is connected to the voltage line L and the neutral line N, respectively, and the other end is connected to one end of the break contact 18a. The other end of the break contact 18a is connected to the ground line FG. The break contact 18b is a contact for alarm output and outputs an alarm output to the outside.

  FIG. 4A shows a general model of induced lightning surge. FIG. 4B shows a clamp voltage waveform by the lightning arrester when an induced lightning surge is applied. For example, when an induced lightning surge 4KV is applied, the line voltages between the voltage line L and the neutral line N, between the neutral line N and the ground line FG, and between the voltage line L and the ground line FG are: The lightning protection elements 13 to 15 are clamped to a voltage of about 650V. However, during the time of about 1 μs when the wavefront length of the induced lightning surge rises, the surge arrester cannot respond, so an excessive surge of about 1000 V to 1200 V is transmitted.

  The fuses 11 and 12 are configured not to be blown by an excessive surge transmitted at the time of rising of the wavefront length, but to be blown by a temperature rise due to characteristic deterioration of the lightning protection elements 13 to 15. The temperature at which the fuses 11 and 12 are blown is set to 130 ° C., for example. The fusing temperature 130 ° C. is a temperature setting value immediately before the lightning protection elements 13 to 15 generate heat and enter a smoke generation state. By configuring the fuses 11 and 12 not to be blown by an excessive surge, it is possible to prevent the fuse from being blown and erroneously detecting the abnormality of the lightning arrester 10 when the wavefront length rises. It is also conceivable to use current fuses for the fuses 11 and 12. However, in that case, the fuse is easily blown by the transmitted excessive surge.

  The transmitted excessive surge is applied to the primary side of the power transformer 16. However, since the primary side of the power transformer 16 has a high surge resistance, the power transformer 16 is not broken by this excessive surge. Further, since the primary side and the secondary side of the power transformer 16 are insulated, the excessive surge applied to the primary side is reduced to about 1/100 on the secondary side and becomes about 10V to 12V. Therefore, the resistor 17 and the relay 18 connected to the secondary side are not damaged by the excessive surge.

  When the lightning protection elements 13 to 15 are not deteriorated in characteristics, the leakage current is small, so that the lightning protection elements hardly generate heat. Therefore, heat generated by the lightning protection element does not reach the fusing temperature, and the fuses 11 and 12 do not blow. In the state where the fuses 11 and 12 are not blown and each lightning protection element is connected to the voltage line L, the neutral line N, and the ground line FG, for example, AC 100 is applied to the primary side of the power transformer 16. In this case, the secondary side voltage AC25V of the power transformer 16 is applied to the drive unit of the relay 18, and the break contacts 18a and 18b are opened. Accordingly, the spare lightning arresters 19 and 20 are disconnected from the ground line FG and do not function against the induced lightning surge. Further, an open signal indicating that the lightning arrester 10 is operating normally is output from the break contact 18b.

  When the break contact 18a is open, the spare lightning protection elements 19 and 20 are inserted in series between the voltage line L and the neutral line N, and are connected in parallel to the lightning protection element 13. is there. Assuming that the lightning arrester 13 has a varistor voltage of 470V, the series connection of the lightning arrester 19 and the lightning arrester 20 is varistor voltage 470V + 470V = 940V. When an induced lightning surge is applied, a clamp current flows concentrating on the smaller varistor voltage of the two lightning protection elements connected in parallel. For this reason, when an induced lightning surge is applied when the break contact 18a is open, a clamp current flows concentrated on the lightning protection element 13, and a large clamp current is applied to the lightning protection elements 19 and 20 having a large varistor voltage. Does not flow. Therefore, the lightning protection elements 19 and 20 can be held as a standby system without deterioration in characteristics.

  Next, consider a case where the lightning protection elements 13 to 15 are deteriorated in characteristics and the leakage current is increased to be in an abnormal heat generation state. Since the heat generation of the lightning arresters 13 to 15 is configured to be efficiently transmitted to the fuses 11 and 12, the temperature of the fuses 11 and 12 rises as the temperature of the lightning arresters 13 to 15 rises. When the temperature of the fuses 11 and 12 reaches the fusing temperature, one or both of the fuses 11 and 12 are blown. As a result, the lightning arrester having deteriorated characteristics is disconnected from the power supply line. When the fuses 11 and 12 are blown, no voltage appears on the primary side of the power transformer 16, and therefore no voltage appears on the secondary side. In this case, no voltage is applied to the drive unit of the relay 18, and the break contacts 18a and 18b are turned on. When the break contact 18b is turned on, an alarm based on a loop signal indicating a lightning arrester abnormality is output to the outside.

  Further, when the break contact 18a is turned on, the spare lightning protection element 19 is inserted between the voltage line L and the ground line FG, and the lightning protection element 20 is connected to the neutral line N and the ground line. It will be inserted between the FG. Thus, even if an induced lightning surge is applied before the lightning arrester 10 is replaced in a state where the lightning arresters 13 to 15 are disconnected from the power supply line, the spare lightning arresters 19 and 20 absorb the induced lightning surge. it can. The contact of the relay 18 is not damaged because it can withstand a high surge current (300 A / 700 μs) generated by the lightning protection elements 19 and 20 when an induced lightning surge is applied. Generally, most of the induced lightning surge is applied between the voltage line L and the ground line FG and between the neutral line N and the ground line FG, so that an alarm is generated and the replacement is maintained. If this period is short, this configuration is sufficient as a temporary protection circuit.

  In this embodiment, a power transformer 16 is used, and a relay 18 for alarm output is arranged on the secondary side of the power transformer 16. Since the power transformer 16 does not use a component that deteriorates against an excessive surge, the power transformer 16 has a high resistance to the surge. In addition, since the primary side and the secondary side are electrically insulated, the secondary side has a function of suppressing surge. Therefore, even when an excessive surge at the time of rising of the wavefront length that the lightning arrester cannot respond to passes through the lightning arrester, the occurrence of abnormality can be accurately detected without erroneously detecting characteristic deterioration of the lightning arrester. Furthermore, the power transformer 16 can be composed of a coil and a core, and there is an advantage that the resistance to excessive surge and the surge suppression function can be realized at low cost.

  In this embodiment, the voltage between the voltage line L and the neutral line N is stepped down to a predetermined voltage by the power transformer 16, and this is used as the drive voltage for the relay 18. In this way, by using the drive voltage of the relay 18 by stepping it down to a voltage that is easy to handle, a relay for low voltage can be used for the relay 18, and the handling of the relay 18 becomes easy. The effect is obtained. In this embodiment, thermal fuses are used for the fuses 11 and 12. Accordingly, the fuses 11 and 12 are not blown when an excessive surge is added, and it is possible to prevent the lightning arrester from being disconnected from the power line when no characteristic deterioration occurs in the lightning arrester.

  In the present embodiment, spare lightning protection elements 19 and 20 are prepared, and when the characteristics of the lightning arresters 13 to 15 are deteriorated and the fuses 11 and 12 are blown, the break contact 18a is turned on to prepare the spare lightning protection elements. 19 and 20 are inserted between the voltage line L and the ground line FG and between the neutral line N and the ground line FG, respectively, to prepare for the next induction surge. By doing in this way, even when an induced lightning surge enters before the lightning arrester 10 is replaced, the surge can be absorbed by the spare lightning arresters 19 and 20. Therefore, it is possible to protect a device connected to the subsequent stage of the lightning arrester 10 even when the characteristics of the lightning arresters 13 to 15 are deteriorated.

  In FIG. 5, the structure of the lightning arrester of 2nd Example of this invention is shown. The lightning arrester 10a of the present embodiment is different from the first embodiment in the configuration on the secondary side of the power transformer 16 having a high surge resistance and a surge suppression function. In the first embodiment, an AC relay is used as the relay 18. In this embodiment, a DC relay is used as the relay 26, the secondary voltage of the power transformer 16 is rectified, converted into a DC voltage, and input to the relay 26.

  For example, assuming that the primary voltage of the power transformer 16, that is, the voltage between the voltage line L and the neutral line N is 100 V AC and the transformer turns ratio is 4: 1, A voltage of 25 VAC appears on the secondary side. This AC25V is both-wave rectified by a diode 21 that rectifies the positive half-wave and a diode 22 that rectifies the negative half-wave. The voltage subjected to both-wave rectification is about 35 V, which is 1.4 times the AC voltage. The voltage subjected to both-wave rectification is smoothed by a smoothing circuit including the coil 23 and the capacitor 24 to generate DC35V. This DC 35V is applied to the relay 26 via the current limiting resistor 25.

  The relay 26 is a relay that operates with a DC voltage, and has two break contacts (26a, 26b). The break contact 26a is a contact corresponding to the break contact 18a (FIG. 2) in the first embodiment, and is a contact for controlling connection / disconnection of the spare lightning arresters 19 and 20 to / from the power supply line. The break contact 26b is a contact corresponding to the break contact 18b in the first embodiment, and is a contact for alarm output. Note that the above-described voltage value and the turn ratio of the power transformer are merely examples, and may be values other than the above-described values. For example, when a DC25V relay is used as the relay 26, the winding ratio of the power transformer 16 may be 6: 1.

  The operation of the lightning arrester 10a of the present embodiment is the same as the operation of the lightning arrester 10 of the first embodiment. That is, when both or one of the fuses 11 and 12 is blown, the voltage on the primary side of the power transformer 16 disappears and the DC voltage on the secondary side also disappears. As a result, the operation of the relay 26 is stopped, the break contact 26b is turned on, and an alarm is output. Also, the break contact 26a is turned on, and the spare lightning arresters 19 and 20 are connected to the ground line FG. When the break contact 26a is turned on, the lightning protection element 19 is inserted between the voltage line L and the ground line FG, and the lightning protection element 20 is inserted between the neutral line N and the ground line FG. Even when an induced lightning surge is applied before the replacement of the lightning arrester 10a, the spare lightning arresters 19 and 20 can absorb the induced lightning surge.

  In FIG. 6, the structure of the lightning arrester of 3rd Example of this invention is shown. The lightning arrester 10b of the present embodiment differs from the lightning arrester 10a of the second embodiment in the way of generating a DC voltage. That is, in the second embodiment, the DC voltage is generated by performing both-wave rectification on the AC voltage on the secondary side of the power transformer 16. In this embodiment, a DC voltage for driving the relay 26 is generated by using a photocoupler 32 having a light emitting unit and a light receiving unit therein.

  For example, if the primary voltage of the power transformer 16, that is, the voltage between the voltage line L and the neutral line N is 100 V AC and the turns ratio of the transformer is 4: 1, A voltage of 25 VAC appears on the secondary side. The AC voltage 25 V is input to the light emitting portion of the photocoupler 32 for AC input through the current limiting resistor 31. An electrolytic capacitor 33 is inserted between the collector and emitter of the transistor in the light receiving portion of the photocoupler 32. One end of the drive unit of the relay 26 is connected to the collector of the light receiving unit transistor of the photocoupler 32, and the other end is connected to the external power supply (+ V) via the resistor 34. Further, the GND of the external power supply is connected to the emitter of the transistor in the light receiving portion of the photocoupler 32.

  FIG. 7 shows operation waveforms of each part. FIG. 7A shows the voltage between the emitter and the collector of the transistor in the light receiving portion of the photocoupler 32. In a normal state, that is, in a state where the fuses 11 and 12 are not blown, AC25V is applied to the light emitting portion of the photocoupler 32. The light emitting unit emits light when a current flows through the diode in the positive half wave and the negative half wave, and the transistor in the light receiving unit is turned on. However, in the vicinity of the AC voltage cross point (zero point), none of the diodes can be turned on. Therefore, before and after the AC waveform crosses zero, the light receiving transistor is turned off. The voltage between the emitter and collector of the transistor in the light receiving portion is approximately 0 V when the transistor is on, and approximately + V when the transistor is off.

  FIG. 7B shows the current between the emitter and the collector of the transistor in the light receiving section. As shown in FIG. 7 (a), the transistor in the light receiving section is periodically turned off, so that the current between the emitter and the collector changes as shown in FIG. 7 (b), and the current flows periodically. No period occurs. Therefore, if the emitter-collector current is supplied to the drive unit of the relay 26 as it is, the break contacts 26a and 26b may be turned on irregularly. That is, an abnormal state may be detected during a normal state.

  FIG. 7C shows the drive current of the relay 26. The current fluctuation is smoothed by inserting an electrolytic capacitor 33 between the emitter and collector of the transistor in the light receiving section. When the transistor of the light receiving unit is on, the potential difference between the emitter and the collector is zero, so that the electrolytic capacitor 33 is in a no-load state. When the transistor is turned off, a charging current flows through the electrolytic capacitor 33. Thereby, the drive current of the relay 26 becomes as shown in FIG. 7C, and the break contacts 26a and 26b can be stably maintained in the open state.

  In the lightning arrester 10b, when both or one of the fuses 11 and 12 is blown, the voltage on the primary side of the power transformer 16 disappears and the AC voltage on the secondary side disappears. As a result, the light emitting unit of the photocoupler 32 stops emitting light, and the transistor of the light receiving unit is turned off. Therefore, the relay 26 stops operating, the break contact 26b is turned on, and an alarm is output. Further, the break contact 26a is turned on, the lightning protection element 19 is inserted between the voltage line L and the ground line FG, and the lightning protection element 20 is inserted between the neutral line N and the ground line FG. Thereby, even when an induced lightning surge is applied before the replacement of the lightning arrester 10b, the spare lightning arresters 19 and 20 can absorb the induced lightning surge.

  As mentioned above, although this invention was demonstrated based on the preferable Example, the lightning arrester of this invention is not limited only to the said Example, What gave various correction and change from the structure of the said Example. Are also included within the scope of the present invention.

The figure which shows the power supply structure to which the lightning arrester of 1st Example of this invention is applied. The circuit diagram which shows the structure of the lightning arrester of 1st Example. The figure which shows the structure of a power transformer. (A) is a figure which shows the general model of an induced lightning surge, (b) is a figure which shows the clamp voltage waveform by a lightning arrester when an induced lightning surge is applied. The circuit diagram which shows the structure of the lightning arrester of 2nd Example of this invention. The circuit diagram which shows the structure of the lightning arrester of 3rd Example of this invention. The wave form diagram which shows the operation | movement waveform of each part of the lightning arrester of 3rd Example.

Explanation of symbols

10: Lightning arrester 11, 12: Fuse 13-15: Lightning protection element 16: Power transformer 17: Resistance 18: Relay 18a, 18b: Break contact 19, 20: Lightning protection element (preliminary)
DESCRIPTION OF SYMBOLS 21, 22: Diode 23: Coil 24: Capacitor 25: Resistance 26: Relay 26a, 26b: Break contact 31, 34: Resistance 32: Photocoupler 33: Electrolytic capacitor 40: Breaker 50: Electric power equipment

Claims (9)

A lightning protection element inserted between the power lines,
A disconnecting means for separating the lightning arrester from the power line when the characteristics of the lightning arrester are deteriorated;
A transformer whose primary side is connected to the power line via the disconnecting means;
A lightning arrester comprising: an abnormality detecting means connected to the secondary side of the transformer and detecting an abnormality of the lightning arrester based on the presence or absence of a secondary voltage.   The lightning arrester according to claim 1, wherein the disconnecting means is constituted by a thermal fuse that blows when the temperature of the lightning arrester exceeds a predetermined temperature.   The lightning arrester according to claim 1 or 2, wherein the transformer turns ratio is N: 1 (N> 1).   The lightning arrester as described in any one of Claims 1-3 comprised with the AC relay which controls the ON / OFF of the alarm output contact based on the presence or absence of the secondary voltage of the transformer.   The abnormality detecting means rectifies the secondary voltage of the transformer to generate a DC voltage, and DC for controlling on / off of the alarm output contact based on the presence or absence of the DC voltage generated by the rectifying means The lightning arrester as described in any one of Claims 1-3 comprised with a relay.   The abnormality detection means includes a photocoupler having a transistor whose light emitting unit is driven by a secondary voltage of the transformer and switching according to the presence or absence of light emission in the light emitting unit, and an alarm output according to the switching of the transistor. The lightning arrester as described in any one of Claims 1-3 comprised with the relay which controls ON / OFF of the contact for operation.   The lightning arrester according to any one of claims 1 to 6, wherein when the abnormality is detected, the abnormality detecting unit connects a spare lightning arrester to the power line. A first lightning arrester inserted between the first power supply line and the second power supply line, a second lightning arrester inserted between the third power supply line and the second power supply line, and A third lightning arrester inserted between the first power line and the third power line;
Disconnecting means for separating the first to third lightning arresters from the first and second power lines when the first to third lightning arresters have deteriorated characteristics;
A transformer whose primary side is connected to the first and second power supply lines via the disconnecting means;
An arrester connected to the secondary side of the transformer, and comprising an abnormality detecting means for detecting an abnormality of the first to third lightning arresters based on the presence or absence of a secondary voltage.   The apparatus further comprises fourth and fifth lightning arresters inserted in series between the first power line and the second power line, and the abnormality detection means detects the abnormality and The lightning arrester according to claim 8, wherein a connection node between the lightning arrester and the fifth lightning arrester is connected to the third power line.

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