JP5697263B2 - Abnormality detection circuit for communication surge protection element - Google Patents

Description

  The present invention relates to an abnormality detection circuit for a communication surge protection element that is connected to various communication lines to protect communication equipment, instrumentation equipment, and the like from lightning surges, and more particularly, easily detects deterioration of the surge protection element. The present invention relates to a possible abnormality detection circuit.

In this type of surge protection element, lightning surge current flows repeatedly, and the characteristics deteriorate with use over time, so that leakage current increases and heat is generated, which may lead to so-called thermal destruction.
For this reason, for example, as shown in Patent Document 1, a circuit has been proposed in which the life of a surge protection element is predicted to facilitate replacement thereof.

  3 is an abnormality detection circuit described in Patent Document 1. In the figure, L is a communication line, 1 is a terminal for controlling a load not shown, and 2 is a transmission unit for controlling communication of the terminal 1. 3 is a lightning arrester for bypassing the lightning surge applied to the communication line L to the ground side, and 4 is a display for displaying the state of the lightning arrester 3. The lightning arrester 3 is provided at a remote location to some extent away from the terminal 1 and the display 4.

  The lightning arrester 3 includes a varistor 31 connected to the communication line L, a current sensor 32 that detects a current flowing through the varistor 31, and an A / D converter that converts an output signal (surge current value) of the current sensor 32 into a digital signal. 33, a memory 35 for storing the number of occurrences of surge, a CPU 34 for calculating the number of occurrences of surge, controlling communication with the display 4, and the like, and a communication driver circuit 36 having an interface function with the communication line L. ing.

In this prior art, the CPU 34 compares the output signal of the A / D converter 33 with a threshold value to obtain the number of surge occurrences, updates the number of surge occurrences stored in the memory 35, and updates the surge. The number of occurrences is displayed on the display 4 via the communication driver circuit 36.
With the operation as described above, the life of the varistor 31 can be predicted from the number of surge occurrences displayed on the display 4, and replacement of the varistor 31 can be promoted before the varistor 31 undergoes thermal destruction.

In addition, what was described in patent document 2 is known as a degradation display apparatus of the lightning arrester connected to the power distribution system, for example.
This deterioration display device charges a capacitor by the leakage current of a lightning protection element connected to the ground line of the power distribution system, and when the voltage of this capacitor exceeds the trigger voltage of the diac, the diac conducts and generates a thyristor gate signal. The display device connected in series to the thyristor is driven to display the deterioration of the lightning protection element.

JP, 2011-19069, A (paragraphs [0023]-[0054], FIG. 1 etc.). JP-A-6-5350 (paragraphs [0013] to [0015], FIG. 1 and the like).

In the prior art described in Patent Document 1, an A / D converter 33, a CPU 34, a communication driver circuit 36, and the like are required to count and display the number of surge occurrences, which complicates the circuit configuration. There is a problem of incurring high costs.
In addition, the prior art described in Patent Document 2 must provide a Zener diode in front of the capacitor in order to prevent erroneous display when a switching surge current or a lightning surge current flows. There was also a problem that the circuit configuration was complicated.
Furthermore, these Patent Documents 1 and 2 do not mention any technique for displaying the deterioration of a plurality of varistors or lightning protection elements using a single DC power source.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an abnormality detection circuit for a communication surge protection element that can easily detect an abnormality such as deterioration for a plurality of surge protection elements with a simple circuit configuration.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that both ends of a surge protection element for communication are respectively connected to the output side of a diode bridge whose input side is connected to a pair of communication lines, and one end of the surge protection element is connected. Communication is performed by connecting the cathode of the first diode to the ground terminal and connecting the other end of the surge protection element to the anode of the second diode and connecting the cathode to the ground terminal. Surge protection circuit for
A voltage of a DC power source is applied to the surge protection element via a third diode having a cathode connected to one end of the surge protection element and a fourth diode having an anode connected to the other end of the surge protection element. Sometimes, a switch element is turned on by a leakage current flowing through the surge protection element, and an abnormal display is performed by a display element connected in series to the switch element.

The invention according to claim 2 is the abnormality detection circuit according to claim 1, further comprising an input unit and an output unit , wherein the input unit is connected in series to the switch element, and the switch element is turned on and the input is performed. And a relay for operating the output unit to output an alarm when an abnormality detection current flows through the unit .

The invention according to claim 3, in the abnormality detection circuit according to claim 1 or 2, wherein the DC power source, said third diode, the surge protection device, and the series circuit of the fourth diode, further constant current Elements are inserted in series.

The invention according to claim 4, in the abnormality detection circuit according to claim 1, wherein the display element, the switching element, the third diode, the surge protection device, and the fourth at least comprising an abnormality detecting unit diodes, which are connected a plurality, in parallel to the DC power source.

According to the present invention, a DC power supply voltage is constantly applied to a surge protection element such as a varistor, and when the leakage current exceeds a predetermined value, the switch element is turned on to display an abnormality. Abnormalities due to deterioration of the surge protection element can be detected.
Further, by supplying a power supply voltage to a plurality of abnormality detection units using a single DC power supply, it is possible to monitor abnormalities of surge protection elements respectively provided on a plurality of communication lines.

1 is a configuration diagram of a communication surge protection circuit to which an embodiment of the present invention is applied. It is a block diagram of the abnormality detection circuit which concerns on embodiment of this invention. It is a circuit diagram which shows a prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a configuration diagram of a communication surge protection circuit to which the present embodiment is applied. In FIG. 1, 100 is a communication surge protection circuit, and 110 is a pair of communication lines having input terminals L1 and L2 and output terminals T1 and T2.

A pair of communication lines 110 are connected to input terminals of a diode bridge 102 composed of diodes D1 to D4, and a surge protection element 101 such as a varistor is connected between the output terminals.
One end of each of the first and second diodes D5 and D6 is connected to both ends of the surge protection element 101, and the other ends of these diodes D5 and D6 are commonly connected to the ground terminal E.
Further, an abnormality detection circuit to be described later is connected to both ends of the surge protection element 101 via third and fourth diodes D7 and D8 connected with the polarities shown.

  In the communication surge protection circuit 100 configured as described above, the lightning surge current that has entered the communication line 110 flows to the ground terminal E via the diode bridge 102 and the surge protection element 101. There is no fear of flowing into communication equipment or instrumentation equipment, and these can be protected from lightning surge.

  Next, FIG. 2 shows an abnormality detection circuit according to the present embodiment. This abnormality detection circuit includes the communication surge protection circuit 100 and diodes D7 and D8 shown in FIG. 1 and their peripheral circuits. Yes. In FIG. 2, the components of the communication surge protection circuit 100 other than the surge protection element 101 are not shown.

In FIG. 2, an abnormality detection unit 150 is provided for each communication surge protection circuit 100, and a plurality of abnormality detection units 150 are connected in parallel to a series circuit of a battery B and a relay Ry described later. . The abnormality detection unit 150, the battery B, and the relay Ry constitute an abnormality detection circuit according to this embodiment.
That is, the communication surge protection circuit 100 of FIG. 1 is connected to each communication line whose abnormality should be monitored, and the abnormality detection circuit of FIG. 2 can collectively detect the abnormality of the surge protection element 101 in a plurality of communication lines. ing.

As shown in FIG. 2, at both ends of a series circuit of a battery B as a direct current power source and a relay Ry composed of a photo MOS (Photo-MOS) relay, a current limiting resistor R, a light emitting diode D10, A thyristor TH is connected in series as a switch element. Here, the relay Ry includes an input unit and an output unit.
Further, one end of a constant current element CRD made of a constant current diode, a resistor or the like is connected to the positive electrode of the battery B, and the other end is connected to one end of the surge protection element 101 via the anode and cathode of the diode D7. . The other end of the surge protection element 101 is connected to the anode of the diode D8, and the cathode is connected to the gate of the thyristor TH.
In the above configuration, a transistor may be used as a switching element instead of the thyristor TH.

Next, the operation of this embodiment will be described.
The lightning surge absorption operation by the communication surge protection circuit 100 of FIG. 1 is as described above, and the surge protection element 101 repeatedly absorbs the lightning surge and is used over a long period of time. Deteriorates and the normal resistance value decreases. Thus, in the abnormality detection circuit in FIG. 2, the leakage current flows through a path of the input portion of the battery B → constant current element CRD → diode D7 → surge protection element 101 → diode D8 → relay Ry. Here, the deterioration of the characteristics of the surge protection element 101 such that leakage current flows, failure, etc. are referred to as “abnormality” of the surge protection element 101.

When the leakage current of the surge protection element 101, that is, the gate current of the thyristor TH exceeds a predetermined value set by the constant current element CRD, the thyristor TH is turned on, and the battery B → resistance R → light emitting diode D10 → thyristor TH → An abnormality detection current flows through the path of the input portion of the relay Ry.
For this reason, the light emitting diode D10 is turned on to visually display the deterioration of the surge protection element 101, and an alarm by contact output or sound can be generated by the operation of the output unit of the relay Ry.

According to this embodiment, since both ends of the surge protection element 101 connected to the battery B via the diodes D7 and D8 are connected to the communication line 110 via the diode bridge 102, the surge protection element 101 communicates with each other. It can be connected by floating in a DC manner from the line 110 side and the ground side. As a result, the abnormality detection operation for detecting the leakage current by constantly applying the DC power supply voltage to the surge protection element 101 does not adversely affect the communication line 110 and thus the signal transmitted and received.
Further, as shown in FIG. 2, by connecting a plurality of abnormality detection units 150 in parallel to the series circuit of the battery B and the relay Ry, the surge protection elements 101 respectively disposed on the plurality of communication lines are connected. Abnormalities can be monitored collectively.

DESCRIPTION OF SYMBOLS 100: Surge protection circuit for communication 101: Surge protection element 102: Diode bridge 110: Communication line 150: Abnormality detection part D1-D8: Diode L1, L2: Input terminal T1, T2: Output terminal E: Grounding terminal Ry: Relay B : Battery R: Resistance CRD: Constant current element D10: Light emitting diode TH: Thyristor

Claims (4)

Both ends of a communication surge protection element are connected to the output side of a diode bridge whose input side is connected to a pair of communication lines, one end of the surge protection element is connected to the cathode of the first diode, and the anode is grounded And connecting the other end of the surge protection element to the anode of the second diode and connecting the cathode to the ground terminal to constitute a communication surge protection circuit,
A voltage of a DC power source is applied to the surge protection element via a third diode having a cathode connected to one end of the surge protection element and a fourth diode having an anode connected to the other end of the surge protection element. An abnormality detection circuit for a surge protection element for communication, characterized in that a switch element is turned on by a leakage current that sometimes flows through the surge protection element, and an abnormality is displayed by a display element connected in series to the switch element. In the abnormality detection circuit according to claim 1,
An input unit and an output unit are provided, and the input unit is connected in series to the switch element. When the switch element is turned on and an abnormality detection current flows to the input unit, the output unit is operated to output an alarm. An abnormality detection circuit for a surge protection element for communication, comprising a relay for causing a failure. In the abnormality detection circuit according to claim 1 or 2,
The DC power source, said third diode, the surge protection device, and the fourth series circuit of a diode, the abnormality detection circuit of the communication surge protection element, characterized in that the further insert the constant current element in series. In the abnormality detection circuit according to any one of claims 1 to 3,
The display element, the switching element, the third diode, the surge protection device, and at least including an abnormality detecting portion said fourth diode, characterized more, that it has connected in parallel to the DC power source Abnormality detection circuit for communication surge protection element.

Images