JP2001349914A - Method and device for measuring insulation resistance of line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for measuring the insulation resistance of a line which can measure the insulation resistance in real time without stopping the use of an actuating facility, and surely can detect insulating defects even when the electric potential is fluctuated at a contact point. SOLUTION: In this method for measuring the insulation resistance between the lines and the ground is measured by the resistance for measurement and the current Is for measurement flowing in the lines to be measured by applying the voltage for measurement between lines 1 and 2 to be measured and the ground via a resistance Rs for measurement connected in series and a power source Es for measurement, the resistance Rs for measurement can be changed over to a first state in which the resistance is connected in series to the power source Es for measurement and a second state the resistance is separated from the power source Es for measurement and directly connected to the ground, the difference between the current Is for measurement flowing in the first state and the current Is' for measurement flowing in the second state is calculated, and the propriety of the insulation resistance of the lines to be measured is judged from the current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the insulation resistance of a line used in a circuit including a line to be measured which has a relatively low voltage and has a single line not in contact with the ground, such as security equipment for railway traffic signals. It is about.

[0002]

2. Description of the Related Art Along a railway line, a signal cable is laid, for example, when a train arrives at a point where a warning should be started for a railroad crossing, that is, a control condition of a breaker of a railroad crossing is sent to a place where a railroad crossing is present. Thereby, signal conditions are transmitted and received. This signal cable is used for transmitting and receiving conditions,
Provide a connection box, equip it with a terminal block for connection,
From one terminal to a similar terminal board placed in a distant connection box, necessary pairs of signal cables are connected to exchange conditions. If the opposite terminals are connected in parallel with the connection box, the condition can be sent further away. In the signal cable having such a configuration, the insulation to the ground may be deteriorated in the connection box or the like, which hinders transmission and reception of conditions. For this reason, it is necessary to detect the deterioration of the insulation of the electric line (measured line) constituted by the signal cable and the like, and to perform early maintenance.

Conventionally, to measure the insulation deterioration, the use of a control circuit is stopped to measure the resistance between the line to be measured and the ground, and the line is measured independently with a megger or the condition is measured with a signal cable. The circuit of the signal to be sent to a distant place uses the fact that the line is floated from the ground, applies a voltage between the ground and the line to be measured at the measurement point, measures the current value, and determines the insulation resistance between the line and the ground. It has also been proposed to know

The method in which the use of the control circuit is stopped and the measurement is carried out by a megger with the line being independent has a problem that the use of the working equipment has to be stopped and it has to be performed at a time when the train is not operating such as at night. Atsuta. Therefore, in order to perform detection before time, nighttime work must be performed regularly, and measurement cannot be performed in real time. Therefore, a failure due to insulation deterioration may occur.

A method of determining the insulation resistance between the ground and the line by applying a voltage between the ground and the line to be measured at the measurement point and measuring the current value according to the following principle. FIG.
As shown in the figure, when the measuring power supply Es and the series measuring resistor Rs are connected to the lines 1 and 2 composed of the power supply voltage E and the load (often a relay) Rl under the control conditions, Since it floats on the ground, the parallel combined resistance of the insulation resistance rp on the plus side and the resistance rm on the minus side under the control condition is measured. FIG. 7 shows an equivalent circuit of this circuit together with its respective closing currents for studying the details. In this equivalent circuit, when the control condition, which is the original target function, is satisfied, the contact S is closed, and the relay R1 is operating, the currents i _{1 to} i ₅ of the circuit are as follows according to Kirchhoff's theorem. Is calculated. i ₁ = Es / Rs + rp i ₂ = E / Rl + rp + rm i ₃ = (Es−E) / Rs + Rl + rm i ₄ = E / Rli ₅ = Es / Rs + rm

Therefore, the measured current Is is Is = i ₁ + i ₃ + i ₅ = (Es / Rs + rp) + (Es
−E) / (Rs + Rl + rm) + Es / (Rs + rm) When Rl is smaller than the other resistances, the measured current Is becomes a function of R, rp, and rm, and the parallel combined resistance of rp and rm greatly contributes. I understand. When the contact S is not formed, the equivalent circuit is as shown in FIG. 8, i ₂ = i ₃ = i ₄ = 0, and the measurement current Is is Is = i ₁ + i ₅ = Es / (Rs + rp ) + Es / (Rs
+ Rm). If Rs is selected to be sufficiently smaller than rp and rm, then Is = Es / (1 / rp + 1 / rm), and the combined resistance of rp and rm is measured.

However, in practice, the potential is different between the ground points of rp and rm and the ground point of the measurement power supply Es. Assuming that the potentials at the ground points of rp and rm and the ground point of the measurement power supply Es are ep, em, and es with respect to the theoretical ground, the equivalent circuit is as shown in FIG. The current value is i ₁ = (Es + es + ep) / Rs + rp i ₂ = (E + ep + em) / Rl + rp + rm i ₃ = (Es−E + ep + em) / Rs + Rl + rm i ₄ = E / Rl i ₅ = (Es + ep / em is measured by (Es + ep / em) = I ₁ + i ₃ + i ₅ = (Es + es + ep) / (Rs + r
p) + (Es−E + ep + em) / (Rs + Rl + rm) +
(Es + ep + em) / (Rs + rm) and is affected by the potential between the ground points.

When the contact S is not formed, the equivalent circuit is as shown in FIG. 4 adopted in the present invention, i ₂ = i ₃ = i ₄ = 0, and the measurement current Is is Is = i _{1 + i 5 = (Es +} es + ep) / (Rs + r
p) + (Es + ep + em) / (Rs + rm), again being affected by the potential between the ground points. The potential at this ground point changes accordingly. The effect is directly added to the measured voltage, and the measured current and the value of the insulation resistance have a poor relationship, which makes it difficult to detect insulation failure.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and enables real-time measurement without stopping the use of actual equipment, and a grounding point. It is an object of the present invention to provide a method and an apparatus for measuring the insulation resistance of a line, which can reliably detect an insulation failure even if there is a change in the potential in the circuit.

[0010]

In order to achieve the above-mentioned object, as shown in FIGS. 1 to 5, the invention according to claim 1 is a method for measuring a series connection between a circuit under test 1, 2 and the ground. Resistance Rs
And a measurement power supply Es to apply a measurement voltage, and by applying the voltage, the insulation resistance of the line for measuring the insulation resistance between the measured line and the ground from the measuring resistance and the measuring current Is flowing through the measured line. In the measuring method, it is possible to switch between a first state in which the measuring resistor Rs is connected in series with the measuring power supply Es and a second state in which the measuring resistor Rs is disconnected from the measuring power supply Es and directly connected to the ground. Measurement current Is flowing
And measuring the difference between the measurement current Is' flowing in the second state and the insulation resistance of the line to be measured based on the calculated current value.

A second aspect of the present invention is to provide a measuring resistor Rs and a measuring power supply E connected in series between the lines under test 1 and 2 and the ground.
a measuring voltage applied through the s and a measuring current Is flowing through the measured circuit and the measuring current Is flowing through the measured circuit to measure the insulation resistance between the measured circuit and the ground. A switch SW is provided to enable switching between a first state in which the measurement resistor Rs is connected in series with the measurement power supply Es and a second state in which the measurement resistance Rs is disconnected from the measurement power supply Es and directly connected to the ground. In addition to having a control function, the measurement current Is flowing in the first state and the measurement current Is ′ flowing in the second state are read, the difference between the two currents is calculated, and the insulation resistance of the circuit to be measured is calculated from the current value. A line insulation resistance measuring device, characterized in that a processing device 3 having a function of judging the quality of the line is provided.

According to a third aspect of the present invention, in the second aspect, the processing device measures the measuring current Is flowing in the first state three times or more in a short time, and sets a time constant for the measuring current Is of the line. The measurement current Is 'flowing in the second state immediately after that is also measured three times or more, the time constant for the measurement current Is' of the line is obtained, and the capacitance of the line is equivalently determined from the plurality of measured values. And the time constant is obtained, whereby the measurement current Is flowing in the first state and the measurement current Is ′ flowing in the second state converge to the final values without having to wait for the circuit under test in a short time. A line insulation resistance measuring device characterized by judging the quality of insulation resistance.

As described above, the measuring current Is obtained by connecting the measuring resistor Rs in series with the measuring power source (measuring voltage) Es between the lines 1 and 2 and the ground is not applied to the measuring current Is. By taking the difference from the measurement Is' flowing when only the measurement resistor Rs is connected in series, the influence of the ground potential is eliminated, and the deterioration of the insulation resistance of the line can be determined from the result. .

When the control condition, which is the original intended function, is satisfied, the contact S is closed, and the relay Rl is operating, E
When only the series resistor Rs is connected without applying s (second
3) is as follows in FIG. Each current value _{i 1 = (es + ep)} / Rs + rp i 2 = (E + ep + em) / Rl + rp + rm i 3 = (- E + ep + em) / Rs + Rl + rm i 4 = E / Rl i 5 = (ep + em) / Rs + rm result Is 'is Is' = I ₁ + i ₃ + i ₅ = (es + ep) / (Rs + r
p) + (− E + ep + em) / (Rs + Rl + rm) +
(Ep + em) / (Rs + rm)

Therefore, if the difference between the measurement current Is flowing in the first state as shown in FIG. 2 and the measurement current Is ′ flowing in the second state shown in FIG. 3 is obtained, Is−Is ′ = ( Es + es + ep) / (Rs + rp)
− (Es + ep) / (Rs + rp) + (Es−E + ep
+ Em) / (Rs + Rl + rm)-(-E + ep + e
m) / (Rs + Rl + rm) + (Es + ep + em) /
(Rs + rm)-(ep + em) / (Rs + rm) = E
s / (Rs + rp) + Es / (Rs + R1 + rm) + E
s / (Rs + rm), and all the differences in the ground potentials are eliminated. Further, the term of the power supply E inserted in the target function circuit is also eliminated, and the ground insulation resistance, the series resistance of the measurement power supply, and the control are controlled. It becomes a function of the load resistance of the relay and the like, and the deterioration of the insulation resistance can be monitored stably.

Further, when the contact S is not formed and the measuring power supply Es is applied, the measuring current Is is obtained from FIG. 4 as: Is = i ₁ + i ₅ = (Es + es + ep) / (Rs + r
p) + (Es + ep + em) / (Rs + rm), and the measuring current I when the measuring power supply Es is not applied.
From FIG. 5, s ′ is: Is ′ = i ₁ + i ₅ = (es + ep) / (Rs + rp) +
(Ep + em) / (Rs + rm), and the difference between the measurement current Is flowing in the first state and the measurement current Is ′ flowing in the first state is Is−Is ′ = Es / (Rs + rp) + Es / ( Rs +
rm), in any case, any difference in ground potential is eliminated and becomes a function of the ground insulation resistance, the series resistance of the power supply for measurement, and the load resistance of the controlled relay, etc., and the insulation resistance deteriorates. Can be monitored stably.

[0017]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram including a circuit to be measured, wherein the circuits to be measured 1 and 2, a control power source E, a control condition S,
For a control line using a cable consisting of a condition receiving relay Rl, a measurement resistor Rs connected to the positive line of the control power supply E, a measurement power supply Es connected in series with the resistance Rs,
A switch SW that bypasses the measurement power supply Es and connects the measurement resistance Rs to the ground, controls the switch, and also measures a measured current Is when the power supply Es is connected (first state), Calculate the difference from the current Is' when the measurement resistor Rs is connected to the ground (second state), bypassing the measurement power supply Es, measure the insulation state of the circuit to be measured, and output an alarm. It comprises a processing device 3.

Here, rp and rm are insulation resistances between the positive and negative grounds of the line, respectively. The processing device 3 has a measurement resistor Rs and a measurement resistor Rs connected in series with the measurement resistor Rs at regular time intervals (can be arbitrarily set by inputting an instruction to the processing device 3) by a programmed control logic contained therein. The power supply Es is connected to the circuits 1 and 2 to be measured, and the measuring current Is flowing through the measuring resistor Rs is applied to the potential difference between both ends thereof.
Or read directly with the current measurement device. Thereafter, the measuring power supply Es is immediately disconnected, the measuring resistor Rs is directly connected to the ground, and the measuring current Is' flowing through the measuring resistor Rs is performed.
Is measured. Is-Is' is calculated from the measured result,
It has a function of judging whether the functional circuit is operating or not from the value and detecting deterioration of the insulation resistance.

For measurement, a measurement power supply E added to the line
The current flowing due to s may exponentially increase exponentially and take time to stabilize due to the effect of the ground capacitance of the line. In this case, it takes time until the measurement current Is ′ flowing when the measurement resistance Rs is directly connected to the ground is stabilized. In such a case, the logic of the processing device 3 is changed to Is
Is measured three times or more in a short time, and immediately thereafter, the measuring resistor Rs
Is directly connected to the ground, and the measurement current Is ′ flowing therethrough is also measured three times or more. From the plurality of measured values, the capacitance of the line capacitor can be calculated equivalently, the time constant can be determined, and the decrease in the actual insulation resistance can be detected without taking time until the line becomes stable.

[0020]

According to the first to third aspects of the present invention, the influence of the power supply voltage of the monitored circuit on the electric line (measured line) configured as described above is not affected by the ground potential at the measuring end. The insulation resistance is not affected by the ground potential, in other words, even if the potential at the ground point fluctuates, the insulation failure can be reliably detected. Further, there is an excellent effect that the deterioration of the insulation resistance can be measured in real time without stopping the function of the monitored circuit as measured by a megger.

[Brief description of the drawings]

FIG. 1 is a circuit diagram including a circuit to be measured according to an embodiment of the present invention.

FIG. 2 is a drawing showing an equivalent circuit including a potential difference between a measurement point ground and a ground of the insulation resistance of each of the positive and negative lines with respect to a theoretical ground.

FIG. 3 is a drawing showing an equivalent circuit (when a contact is formed) when directly grounded by a measuring resistor without a measuring power supply.

FIG. 4 is a drawing showing a value circuit when a contact is not formed, including a potential difference between a measurement point ground and a ground of insulation resistance of each of positive and negative lines with respect to a theoretical ground. .

FIG. 5 is a drawing showing an equivalent circuit (when no contact is formed) when directly grounded by a measuring resistor without a measuring power supply.

FIG. 6 is a conventional circuit configuration diagram corresponding to FIG.

7 is a drawing showing an equivalent circuit of FIG. 6 and respective closing currents thereof.

FIG. 8 is a drawing showing an equivalent circuit when no contact is formed.

[Explanation of symbols]

 1, 2 Circuit under test 3 Processing equipment E Control power supply S Control condition R1 Conditional reception relay (load) Rs Measurement resistance Es Measurement power supply Is Measurement current flowing in first state Is' Measurement flowing in second state Current SW switch rp, rm Insulation resistance

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G014 AA04 AB31 AC18 2G028 AA01 BF05 CG03 DH03 FK01 MS01 5H410 CC02 DD02 FF05 FF09 FF21 FF28

Claims (3)

[Claims] 1. A measuring voltage is applied between a circuit to be measured and ground via a measuring resistor and a measuring power supply connected in series,
In a method for measuring insulation resistance between a circuit to be measured and the ground from a measurement resistance and a measurement current flowing through the circuit to be measured by applying the voltage, the measurement resistance is connected in series with a power supply for measurement. The first state and the second state which is separated from the measurement power supply and directly connected to the ground can be switched, and the difference between the measurement current flowing in the first state and the measurement current flowing in the second state is determined. A method for measuring the insulation resistance of a line, comprising calculating and judging the insulation resistance of the line to be measured from the current value. 2. A voltage for measurement is applied between a circuit to be measured and the ground via a measuring resistor and a measuring power supply connected in series,
In an insulation resistance measuring device for measuring insulation resistance between a circuit to be measured and the ground from a resistance for measurement and a measurement current flowing through a circuit to be measured by applying the voltage, the measurement resistance is connected in series with a power supply for measurement. A switch that can be switched between the first state and the second state that is separated from the power supply for measurement and directly connected to the earth, has a function of controlling switching of the switch, and has a function of controlling the switch in the first state. A processing device having a function of reading the current and the measuring current flowing in the second state, calculating the difference between the two currents, and judging whether the insulation resistance of the line to be measured is good or not from the current value. Line insulation resistance measuring device. 3. The processing device measures the measuring current flowing in the first state three times or more in a short time, obtains a time constant for the measuring current of the line, and immediately after that, measures the measuring current flowing in the second state. The measurement current is also measured three or more times, the time constant of the line for the measurement current is determined, the capacitance of the line is equivalently calculated from the plurality of measured values, and the time constant is determined. 3. The circuit according to claim 2, wherein the quality of the insulation resistance of the circuit to be measured is determined in a short time without waiting for the flowing measurement current and the measurement current flowing in the second state to converge to the final value. Insulation resistance measuring device.