JPH028662B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an insulation monitoring device for monitoring insulation performance of communication cables.

Conventionally, insulation resistance has been measured by measuring leakage current when a voltage is applied and converting this into a resistance value. This is the principle of an insulation resistance meter.

FIG. 1 is a connection diagram of three basic insulation resistance measuring circuits implemented in a conventional insulation monitoring method. In the figure, 1 is L ₁ of the cable core to be monitored, 2 is L ₂ , 3 is the measurement terminal of L ₁ , 4 is the measurement terminal of L ₂ , 5 is the ground terminal at ground potential, and 6 is the insulation resistance. 7 is a battery for measuring insulation resistance.

Conventionally, the insulation of communication cables has been monitored by monitoring the insulation between the L ₁ (1) and the ground (Fig. 1 a) and between the L ₂ (2) and the earth (Fig. 1 b) and L ₁ (1)−
This is done by comparing the measured insulation resistance values of the three connections between L ₂ (2) (FIG. 1 c) with a preset insulation resistance standard value. When switching the connection mode in this way, a charging/discharging current flows with respect to the capacitance of the core wire due to a change in the applied state of the measurement voltage, and it is necessary to wait until a steady state is reached before making a determination, which may cause insulation failure. Detection required several seconds to several tens of seconds. Furthermore, there is a drawback that it may not be possible to detect when the circuit on the other side with the insulation failure has a power source or when the insulation failure occurs for a short time.

The present invention is performed using conventional insulation monitoring methods.
L ₁ -core wire to earth, L _2- core wire to earth, and L _1- core wire to earth.
L In addition to being able to monitor insulation between _two core wires, it is also possible to monitor insulation regardless of whether or not the circuit on the other side of the insulation failure has a power supply, and it is also possible to monitor insulation for short-term insulation failures. It is an object of the present invention to provide a communication cable insulation monitoring device that can eliminate the drawbacks of the prior art and expand the monitoring range.

The main points of the configuration of the present invention include a resistor circuit that sets the core wire of the communication cable whose insulation is to be monitored to a specific potential, and a resistor circuit that sets the potential at which the core wire becomes insulated with respect to the ground as an upper limit value. The lower limit value is set to the potential at which the core wire becomes insulated from another circuit that has a power supply, and the potential of the core wire monitored not only deviates from the potential set by the resistor circuit but also The present invention includes a comparator that outputs a signal indicating poor insulation when the voltage exceeds the range defined by the upper limit value and the lower limit value.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a connection configuration diagram showing one embodiment of the present invention, and FIG. 3 is an explanatory diagram of its operation.

In FIG. 2, 8 is the insulation monitoring device according to the present invention, 9 is the resistor R ₁ , 10 is the resistor R ₂ , 11 is the resistor R ₃ ,
Reference numeral 12 denotes R ₄ , and 13 denotes an insulation monitoring power supply, which normally uses a negative power supply for communication of 48 volts (hereinafter referred to as [V]), but here it is denoted as -v [V]. 1
4 is a comparator that outputs a signal indicating poor insulation when the potential of measurement terminal 3 of L ₁ core wire 1 is out of a preset range, and 15 is a comparator that outputs a signal indicating insulation failure when the potential of measurement terminal 4 of L ₂ core wire 2 is A comparator 16 is an OR circuit which outputs a signal indicating poor insulation when the voltage exceeds a set range. 17 is a comparator 14
18 is the output terminal of the comparator 15, 19
is a logical sum output terminal of output terminals 17 and 18.
20 is the insulation resistance R ₁₀ between _L1 core wire and _L2 core wire, 21 is
The insulation resistance R ₁₁ , 22 between L ₁ core wire 1 and ground is determined by the insulation resistance between L ₁ core wire 1 and the communication power supply when insulation failure occurs between L 1 core wire 1 and the circuit that has the power supply. The insulation resistance R ₁₂ , 23 is the insulation resistance R ₁₃ , 24 between _L2 core wire 2 and the ground, and 24 is the insulation resistance 22
Same as L ₂ Insulation resistance of wire 2 side R ₁₄ , 25 and 26
1 and 2 show communication power supplies of insulation resistors 22 and 24, respectively. Comparators 14 and 15 are generally called window comparators.

The operation of the apparatus of the present invention will be explained with reference to FIGS. 2 and 3. The cable core 1 to be monitored is set to a specific potential v ₁ by resistors 9 and 10.Similarly, the cable core 2 to be monitored is set to a specific potential v1 by resistors 11 and 12.
Set it to _v2 . This is the insulation resistance 20, 21,
22, 23 and 24 are at infinity and are the potentials when the cable is completely normal. When the input potential of the comparator 14 is within a preset range centered around _v1 , its logical output is "0". If this range is exceeded, the logic output becomes "1", indicating an insulation failure. The same goes for the comparator 15, when the input potential is within a preset range centered around _v2 ,
The logic output is "0", but when this range is exceeded, the logic output becomes "1", indicating an insulation failure. As a result, the output of the OR circuit 16 also becomes logic "1". As mentioned above, the resistance values of resistors 9 and 10 are R ₁ ,
If R ₂ [ohm] (hereinafter referred to as [Ω]), then v ₁ = −v×R ₁ /R ₁ +R ₂ [V] is set. Similarly, the resistance values of resistors 11 and 12 are
If R ₃ and R ₄ [Ω], set v ₂ = −v×R ₃ /R ₃ +R ₄ [V].

In FIG. 3, v ₁₁ is the upper limit setting value of the comparator 14,
v ₁₂ is the lower limit setting value. Similarly v ₂₁ is comparator 15
is the upper limit setting value, and _v22 is the lower limit setting value.

The upper limit setting value _v11 of the comparator 14 is set when _L1 of the cable core to be monitored has poor insulation with respect to the ground.
In other words, it detects when the resistance value R ₁₁ of the insulation resistor 21 in Figure 2 falls below the standard value. If this standard value is R _11f , it means that R ₁ and R _11f are connected in parallel. v ₁₁ =-v×R ₁ ×R ₁₁ f/R ₁ +R ₁₁ f/R ₁ ×R ₁₁ f/R ₁ +R ₁₁
Set f＋R ₂ [V].

The lower limit setting value v ₁₂ of the comparator 14 is set when L ₁ of the monitored cable core has poor insulation between the negative communication power supply (another circuit with a power supply), that is, the insulation resistance 22 in FIG. This occurs when the resistance value R ₁₂ of is below the standard value, and if this standard value is R _12f , then R ₂ and R _12f are connected in parallel, so v ₁₂ = −v×R ₁ /R ₁ +R ₂ ×R ₁₂ f/R ₂ +R ₁₂ f [V].

The same goes for the comparator 15, and the standard value for the resistance value _R13 of the insulation resistance 23 of the monitored cable core _L2 to the ground is _R13f , and the insulation resistance 24 for the negative communication power supply (other circuits having a power supply) Assuming that the standard value for the resistance value R ₁₄ is R _14f ,
The upper limit setting value v ₂₁ and lower limit setting value v ₂₂ are set as follows.

v ₂₁ =-v×R ₃ ×R ₁₃ f/R ₃ +R ₁₃ f/R ₃ ×R ₁₃ f/R ₃ +R ₁₃
f＋R ₄ [V] v ₂₂ = -v×R ₃ /R ₃ +R ₄ ×R ₁₄ f/R ₄ +R ₁₄ f [V] With the above explanation, the insulation resistance standard values R ₁₁ , R _12f , R _13f
and R _14f are shown individually, but they are generally the same value.

The reason why there is a difference in the potential setting between L ₁ and L ₂ of the cables to be monitored, such as v ₁ and v ₂ in Figure 3, is as follows.

In Figure 2, L ₁ −L ₂ of the cable core to be monitored
When the resistance value R ₁₀ of the insulation resistance 20 between
If the set value v ₁ of the core wire L ₁ and the set value v ₂ of the core wire L ₂ are the same, the input potentials of the comparators 14 and 15 do not change,
This cannot be detected. If the settings are shifted as shown in FIG. 3, the input potentials of the comparators 14 and 15 will approach each other as the insulation resistance value R ₁₀ of the insulation resistor 20 decreases. Input of comparator 14
Insulation failure is detected when the voltage is higher than v ₁₁ or when the input of comparator 15 is lower than v ₂₂ , so the core wire L ₁
-L ₂ insulation failure can be detected. Core wire L ₁ −
The insulation resistance R ₁₀ between L ₂ decreases and the detected value
When R _10f is assumed, R _10f is detected as a value lower than other insulation resistance standard values R _11f , R _12f , R _13f and R _14f due to the configuration of this device. The value is the set potential of core wires L ₁ and L ₂
v ₁ , v ₂ and insulation resistance standard values R _11f , R _12f , R _13f , R _14f
Determined by

One embodiment of the present invention is configured as described above, and when the cable core wire to be monitored has poor insulation, a logic signal "1" indicating poor insulation is output to the output terminal 19, and this causes the external Activate alarm bells, etc. Furthermore, it is possible to know from the output terminals 17 and 18 which comparator has detected the insulation defect.

In the above explanation, the conductor resistance of the monitored cable core is usually ignored because it is very small compared to the standard insulation resistance value.

FIG. 4 is a circuit diagram showing a specific configuration of an embodiment of the present invention. 27, 28, 29, 30 in the same figure
is a resistor, 31 is a power supply for setting the judgment potential of the comparator,
32 and 33 monitor the potentials of the two input terminals, positive and negative, and output a logic signal "1" if the potential of the positive input terminal (hereinafter referred to as + input) is high.
Comparator 3 that outputs a logic signal "0" if the potential of the negative input terminal (hereinafter referred to as -input) is high.
4 is an OR circuit, which constitutes the comparator 14. Similarly, 35, 36, 37, 38 are resistors, 39 is a power supply for setting the judgment potential of the comparator, 40,
41 monitors the potential of two input terminals, positive and negative, and outputs a logic signal "1" if the potential of the + side input terminal is high, and outputs a logic signal "0" if the potential of the one side input terminal is high. The comparator 42 is an OR circuit, which constitutes the comparator 15.

FIG. 5 is an explanatory diagram of the operation of comparators 14 and 15 in the circuit configuration shown in FIG. 4. Comparator 1 below
The operation of No. 4 will be explained.

The negative input of the comparator 32 is connected by resistors 27 and 28.
v Set to ₁₁ . Resistors 29 and 30 set the +input of comparator 33 to v ₁₂ . + of comparator 32
The input and the -input of the comparator 33 are connected to the measurement terminal 3 of the cable core _L1 to be monitored. When the insulation state of the monitored cable core L ₁ is normal and the insulation resistances R ₁₁ and R ₁₂ are infinite (indicated by ∞ in the figure), the potential of the measurement terminal 3 is v ₁ . At this time, the output of the comparator 32 is logic "0". When the insulation resistance R ₁₁ decreases, it is equivalent to a decrease in the resistance value R ₁ of the resistor 9, and the potential at the measurement terminal 3 increases, and when it exceeds v ₁₁ , the voltage at the comparator 3
The output of 2 becomes logic "1". Or insulation resistance
When R ₁₂ decreases, it is equivalent to a decrease in the resistance value R ₂ of resistor 10, and the potential at measurement terminal 3 decreases, causing v ₁₂
When the value exceeds 0, the output of the comparator 33 becomes logic "1". When the output of either comparator 32 or 33 becomes logic "1", the output of OR circuit 34 becomes logic "1"
Then, the logic output of the comparator 14 becomes logic "1", indicating an insulation failure of the core wire _L1 .

The same applies to the comparator 15, and the insulation resistance R ₁₃ or
When R ₁₄ decreases and exceeds v ₂₁ or v ₂₂ , the output of the OR circuit 42 becomes logic "1" and the logic output of the comparator 15 becomes logic "1", indicating poor insulation of the core wire L ₂ . The operation of the OR circuit 16 is the same as that shown in FIG. 2, and when the output of the comparator 14 or 15 is logic "1", the logic output becomes "1", indicating poor insulation of the cable.

As explained above, according to the present invention, various insulation defects occurring in communication cables can be detected. In addition, in the conventional technology, it was necessary to change the connection of the core wire of the cable to be monitored, and immediately after the change of connection, monitoring was impossible for a while until the influence of the charging and discharging current disappeared, but in the present invention, Since it is not necessary to change the connection of the monitored cable core during monitoring and continuous monitoring can be performed, it is possible to detect insulation failures that occur for a short period of time.

As described above, according to the present invention, the range of insulation monitoring is expanded compared to the conventional technology, so that insulation defects in communication cables can be quickly and accurately detected, and maintenance and management of telecommunications networks is facilitated. , which has the advantage of being highly sophisticated.

[Brief explanation of drawings]

Figure 1 is a connection diagram of three basic insulation resistance measurement circuits implemented in the conventional insulation monitoring method.
Fig. 2 is a connection configuration diagram showing an embodiment of the present invention, Fig. 3 is an explanatory diagram of its operation, Fig. 4 is a specific circuit diagram of an embodiment of the invention, and Fig. 5 is an explanatory diagram of its operation. , is. Symbol explanation, 1... L ₁ of the monitored cable core,
2... _L2 of the monitored cable core, 3... _L1 measurement terminal, 4... _L2 measurement terminal, 5...ground terminal,
6... Insulation resistance meter, 7... Battery, 8... Device of the present invention, 9, 10, 11, 12... Resistor, 13...
Power supply, 14, 15... Comparator, 16... OR circuit, 17, 18, 19... Output terminal, 20, 2
1, 22, 23, 24... Insulation resistance, 25, 26
...Power supply, 27, 28, 29, 30...Resistor,
31... Power supply, 32, 33... Comparator, 34...
OR circuit, 35, 36, 37, 38...Resistor, 39...Power supply, 40, 41...Comparator, 42
...Order circuit.

Claims (1)

[Claims] 1. A resistance circuit that sets the core wire to be monitored for insulation of a communication cable to a specific potential, and other circuits whose upper limit is the potential at which the core wire becomes insulated with respect to the ground, and whose core wire has a power source. The lower limit value is set as the potential at which insulation failure occurs between 1. A communication cable insulation monitoring device comprising: a comparator that outputs a signal indicating poor insulation when the cable deviates from a specified range.