JPH0365689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fault detection method for communication cables used in telegraph and telephone lines, etc., and in particular detects abnormalities in the communication cables due to flooding, fire accidents, etc. occurring in buildings, warehouses, etc. The present invention relates to a remote abnormality monitoring system that can centrally detect abnormalities and monitor abnormalities at remote locations.

Conventionally, the method of monitoring failures, accidents, etc. of objects to be monitored that occur at remote locations using a central monitoring device, activating alarms, and displaying failure points has been to detect failures using failure detection sensors installed at several locations. Either the signal is sent to a central monitoring device using time division multiplexing or frequency multiplexing and the data is analyzed to determine the fault location, or the detection signals from fault detection sensors installed at each remote location are sent to a central monitoring device. There was a method of collecting information via individual communication lines laid down to each point.

However, although the former multiplexing method has the advantage of reducing the number of communication lines to be laid to transmit signals, it has the disadvantage that the central monitoring equipment and detection sensors are expensive. The disadvantage is that the number of communication lines increases, making it expensive to install them.

In addition, as a method for monitoring failure points in communication cables, the communication cable is constantly filled with gas (nitrogen gas, dry air, etc.), and the pressure and pressure gradient are detected using a sensor installed at the connection part of the communication cable. A method is known in which water is detected by a sensor and flood accidents are monitored based on the detection result, but such a method also has the disadvantage that the detection sensor is expensive and the monitoring mechanism is complicated.

This invention was developed in consideration of the above-mentioned circumstances, and a central monitoring device assigns a certain weight to two or more detection points to be monitored via a round-trip communication path when a failure occurs in the object to be monitored. Detection sensors from which current flows out are connected in parallel via a reciprocating communication line, and the current flowing out from the detection sensors is collected and measured by a central monitoring device, so that the point where a fault occurs can be detected. This provides a system for monitoring abnormalities at remote locations.

The outline of this invention will be explained below based on FIG. 1.

In this figure, L ₁ and L ₂ are round-trip communication lines through which detection current flows, and S _a1 , S _a2 ...S _ao , and
S _b1 , S _b2 ... S _bo is located at each detection point a _o , S _o-1 ... a ₁ , and b _o , b _o-1 ... b ₁ and detects a failure of the monitored object. Showing the sensor.

Therefore, for example, when the object to be monitored is a communication cable and a flooding accident in the communication cable is to be detected, the round-trip communication lines L ₁ and L ₂ are either the communication cable itself or a communication cable including coaxial cable, etc. This serves as a monitoring line for intervening monitoring. S _a1 , S _a2 ...S _ao , and S _b1 , S _b2 ... S _bo serve as water immersion sensors that mainly detect water intrusion of communication cables.

Furthermore, in the case of fault detection in warehouses, buildings, etc., which are objects to be monitored, the round-trip communication lines L ₁ and L ₂ are monitoring lines laid inside the building to collect detection signals, and S _a1 and S _a2 ...S _ao , and S _b1 , S _b2 ...
...S _bo is a detection sensor that is mainly sensitive to temperature, smoke, humidity, etc.

The detection sensors S _a1 to S _ao and S _b1 to _{S bo} each include a humidity sensing element m and a constant current source I driven by the humidity sensing element m when detecting water intrusion, as will be explained in detail in the circuit described later. ₁ to I _o , and a diode D, and when the humidity sensing element m detects a flooding accident, a (constant) current i ₁ to _{i o} flows in the direction of the diode D.
is starting to flow.

Furthermore, the area surrounded by a dashed line indicates a measuring section of the central monitoring device, and this measuring section W is generally composed of a power source E, a resistor R, a changeover switch SW, an adder circuit A, and the like.

In this remote abnormality monitoring method, if each detection sensor placed at each arbitrary detection point does not detect an abnormality (we will explain the flooding accident below),
The current flowing out from the detection sensors S _a1 to _{S ao} and S _b1 to _{S bo} is 0, and a slight current i ₀ (idle current) flowing to the humidity sensing element m energized by the power source E is detected.

However, when the changeover switch SW is turned on so that the polarity is as shown, for example, the detection point
When a flooding accident occurs in the communication cable, which is the object to be monitored, at a1, the constant current source _I1 of the detection sensor _{S a1} is driven, and the current _i1 flows through the resistor R of the measuring part W, and reaches the point P.
A voltage of i ₁ R + ni ₀ R is generated. Note that when the changeover switch SW is turned on to the dotted line position, the power E is supplied with the opposite polarity, so the detection sensor S _b1
~S _bo is energized, and the current (i ₁ to i _o ) flowing out when a flooding accident occurs between detection points b _o to b ₁ is detected.

Therefore, if we now set the value of the constant current flowing out from each constant current source I ₁ to I _o to be 1 to 2 ^n-1 times the unit current I, the detected voltage e _i obtained across the resistor R is , e _i = RI _SV = RI {K _o 2 ^n-1 + K _o-1 2 ^n-2 +...K ₂ 2 + K} + Rni ₀ ...(1) (However, K _o , K _o-1 ...K ₂ , _K1 is 1 for the detection point where there is flooding, and 0 for the point where there is no flooding.) In other words, the current value of each constant current source _I1 to _Io is 1,
Make it something with a weight of 2, 4, 8...

Then, the detection voltage e _i will be a different value, not only when a flooding accident occurs at one of the detection points, but also when a flooding accident occurs at multiple detection points, so the idle voltage can be calculated from this detection voltage e _i. Rni ₀ = e _o
By monitoring the monitoring voltage e (output of adder circuit A) obtained by subtracting , any type of flooding condition can be properly detected. (However, e _o < IR) That is, e=e−e _o = RI (K _o 2 ^n-1 + K _o-1 2 ^n-2 +…+K ₂ 2 + K ₁ ) …(2) (However, K _o , K _o-1 , ...K ₂ , K ₁ are 1 for the detection point where there is flooding and 0 for the point where there is no flooding.)

Also, when the changeover switch SW is turned to the dotted line position, detection sensors S _b1 to S _bo are activated, so _bo
Flood accidents from point b to point _b1 can be detected for the same reason. Therefore, due to the round-trip communication lines L ₁ and L ₂ ,
2n detection points can be monitored.

Fig. 2 shows a specific circuit example of the measurement unit W surrounded by the dashed line, in which OP ₁ to _{OP 3} are differential amplifiers that constitute a high input resistance differential amplifier circuit, SW is a changeover switch, and SP indicates a lightning protection circuit, and AAC indicates a monitoring device that analyzes detected current, provides warnings, displays, etc.

As described above, a plurality of detection sensors S _a1 to S _ao and S _b1 to S _bo are connected to the reciprocating communication lines L ₁ and L ₂ and are supplied with power E via the changeover switch SW.

(Note that the lightning protection circuit SP is not necessarily required.) The high input resistance differential amplifier circuit has an output voltage e p3 of the high input resistance differential amplifier circuit, where the voltages at the input points are e _i1 and e _i2 , and the output voltage e _p3 is e _p3 = {1+R ₂ +R ₃ / R ₁ )e _i2 −(1+R ₂ +R ₃ /R ₁ )e _i1 }R ₅ /R ₄ . Here, if R ₂ = R ₃ and R ₄ = R ₅ , then e _p3 = (1+2R ₂ /R ₁ ) (e _i2 − e _i1 ) (3).

Therefore, the value is (1+2R ₂ /R ₁ ) times the potential difference e _i generated across the two resistors R/2.

Then, the common mode input noise voltage commonly induced in the round-trip communication lines L ₁ and L ₂ can be removed.

On one side of the adder circuit installed in the monitoring device AAC,
The output voltage e _p3 of the high input resistance differential amplifier circuit is added to the other, and the idle voltage -(1+
If a voltage multiplied by 2R ₂ /R ₁ ) is applied, the output voltage will be proportional to the sum of the currents in the flooded area.

Therefore, if the voltage value of this output voltage is monitored, a flooded location can be detected from the above equations (1) to (3).

In this case, the currents flowing out from the detection sensors S _a1 to S _ao and S _b1 to _{S bo} are constant currents, and are weighted 1 to 2 ^n-1 times the unit current I as described above.
It is not affected by the resistance of the round-trip communication lines L ₁ and L ₂ .

Figure 3 shows a specific circuit example of the detection sensors S _a1 to S _ao and S _b1 to _{S bo} , where m is a humidity sensing element, T ₁ and T ₂ are transistors, and D _z1 to D _z3 are Showing a Zener diode.

The humidity sensing element m has comb-shaped electrodes arranged on an insulating substrate and is coated with a resistive film made of resin and conductive particles, and its electrical characteristics are 10KΩ or less at normal humidity, as shown in Figure 4. It is composed of a resistor whose resistance value increases sharply (several 100KΩ or more at around 100% humidity) as the spacing between conductive particles expands when it gets wet due to water immersion.

Therefore, the bias voltage of the transistor T ₁ specified by the Zener diode D _z1 is normally set to an off state when the resistance value of the humidity sensing element m is low, so the transistor
No bias current flows through T ₂ and a constant current circuit is not formed.

However, when this detection sensor is placed in a nearly 100% humidity atmosphere due to flooding or a flooding accident, the resistance value of the humidity sensing element m rapidly increases, the transistor _T1 becomes conductive, and the Zener Zener voltage is generated when sufficient current flows through the diodes D _z2 and D _z3 .

At this time, the current _io flowing through the transistor _T2 rapidly rises to a constant current as shown by _io in FIG. Zener voltage of Zener diode D _z3
If V _z , then i _o ≒ V _z - V _BE /R, so depending on the setting of the resistance R or the Zener voltage V _z , the current will vary for each detection sensor S _a1 ~ S _ao , S _b1 ~ _{S bo} can be set so that the current i _o
It is possible to perform weighting.

Although a sensor using a humidity sensitive element m has been described, it goes without saying that a temperature sensitive element, a pressure sensitive element, etc. can be used depending on the type of fault in the monitored object to be detected.

Further, the idle current flowing through the sensing element may be supplied by a third line provided separately.

As explained above, in the remote abnormality monitoring method of the present invention, the detection sensor placed at the fault detection point connected by the round-trip communication line has a built-in constant current source, and the fault detection method of the monitored object is detected. Since the current flowing out from the constant current source is given a certain weight, the point where a fault has occurred can be immediately detected by measuring and monitoring this current flowing out.

Therefore, laying a line to collect the detected current,
Another advantage is that although the detection sensor is simplified, it is possible to accurately detect the occurrence of failures at multiple points.

Furthermore, by reversing the polarity of the power supply supplied to the round-trip communication line, the number of detection sensors can be doubled, and furthermore, if the number of detection sensors is not increased, the detection accuracy can be improved accordingly. It has the effect of being able to

[Brief explanation of drawings]

Fig. 1 is a schematic diagram for explaining the remote abnormality monitoring system of the present invention, Fig. 2 is a block diagram showing an embodiment of the central monitoring device, Fig. 3 is a circuit diagram of a detection sensor, and Fig. 4 is a humidity FIG. 3 is a data diagram showing an example of resistance characteristics of a sensing element and detected current. In the figure, L ₁ and L ₂ are round-trip communication lines, S _a1 ~ S _ao , S _b1
~ _Sbo are detection sensors provided at detection points a1 _{~ ao} and _b1 ~ _bo , respectively; W is a measurement unit of the central monitoring device;
_I1 to _Io indicate constant current sources.

Claims (1)

[Claims] 1. From a central monitoring device to 2. via a round-trip communication line.
A detection sensor that outputs a certain weighted current when a failure of the object to be monitored is detected is placed at the above remote location, and the current flowing from the detection sensor is collected in the central monitoring device. A remote abnormality monitoring method that detects fault points by measuring 2. The monitoring device is equipped with a power supply that supplies a voltage with reversed polarity to three or more detection sensors, and the current can be collected when at least one of the detection sensors is connected to the power supply with reverse polarity. A remote abnormality monitoring system according to claim 1, characterized in that: