JP6609984B2 - Insulation resistance measuring method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring an insulation resistance of a power feeding circuit in an operating state of a system, that is, in a live line state. For example, in an electric propulsion ship using a DC power source, from the viewpoint of safety confirmation during operation, the power supply circuit is required to be always in a live state and continuously monitor the insulation resistance. It is suitable for use in such applications.

  As an apparatus for measuring the insulation resistance of an ungrounded power supply path, an apparatus disclosed in Patent Document 1 is known. This conventional insulation resistance measuring apparatus is shown in FIG.

  The conventional insulation resistance measuring apparatus shown in FIG. 6 constitutes a T-type detection circuit by the detection resistors 101 to 105, and signals 106 (voltage V1), 108 (voltage V2) and 107 ( Each voltage V3) is obtained. These signals 106 to 108 are input to the primary sides of the isolation converters 109, 110, and 111, respectively, and are converted to secondary signals 112 to 114, respectively.

  Harmonic components are removed from the secondary signals 112 to 114 by the low-pass filters 115, 116, and 118 to become signals 119 to 121, of which the signals 119 and 120 are the positive divider 125, and the signals 120 and 121 are the negative electrodes. Input to the side divider 126 and division is performed. The polarity discriminator 122 discriminates the polarity of the signal 120 and generates an output that turns on the signal 123 when the signal 120 is in the (+) direction, that is, when the voltage VR3 is in the (+) direction. When the direction is the direction, an output that turns on the signal 124 is generated.

  When the polarity discriminator 122 (PC) outputs the signal 123 in the (+) direction, the positive side calculators 125 and 131, the display device 135, and the alarm device 136 are operated to lock the negative side. Similarly, when the polarity discriminator 122 outputs a signal 124 in the (−) direction, the negative side calculators 126 and 132, the display device 135, and the alarm device 136 are operated to lock the positive side.

Hereinafter, the polarity discriminator 122 (PC) is (+) outputs a direction signal 123, it will be described for measuring the insulation resistance of the positive electrode sheet path.

Referring to measure operation explanatory diagram of the insulation resistance of FIG. 7 will be described for measuring the insulation resistance of the positive electrode sheet path.

  Here, the ratio of the resistance value R11 of the positive-side resistor 101 to the resistance value R12 of the resistor 102 or the resistance value R21 of the negative-side resistor 103 to the resistance value R22 of the resistor 104 is 1: 1/100, respectively. Although it is about ˜1: 1/25, an optimum value is selected depending on the voltage value of the circuit to be measured or the range of the insulation resistance value to be measured.

For example, when measuring the insulation resistance of a DC voltage 500V circuit, when the resistance values R11 and R21 of the detection resistors 101 and 103 are set to 1 MΩ and the resistance values R12 and R22 of the detection resistors 102 and 104 are set to 10 KΩ, the insulation resistance is infinite. If RPx = ∞ in the large case, the current IPX flowing through the insulation resistance RPx shown in FIG. 7 does not flow. As a result, the voltages V1, V2 across the detection resistors 102, 104 are V1 = V2, and the current IS flowing through the detection resistors 101, 102, 103, 104 is
IS≈V / (R11 + R12 + R21 + R22)
Since the M potential is VP = VN = 250V and the resistance ratio of the resistors 101 and 102 is 1: 1/100, a voltage of 250V / 100≈2.5V is generated in the resistors 102 and 104. become.

Now, the insulation resistance RPx of positive feed path P of the feed circuit and decreases, ground current IPX = V ÷ (RPx + R3 + R21 + R22) flows in the grounding circuit, at both ends of the detection resistor 105 V3 = IPX × R3
Is generated. At this time, the voltage V1 across the detection resistor 102 is determined by the current IS, and the voltage V3 across the detection resistor 105 is determined by the current IPX. That is, when the resistance values of the resistor 101 and the insulation resistor RPx are sufficiently larger than the resistance values of the resistors 102 and 105, respectively, if R12 = R3, the ratio of the voltage values of V1 and V3 is the resistance value R11 of the detection resistor 101. Therefore, the voltage ratio n (= V1 / V3) of V1 and V3 is obtained, and the ratio n is multiplied by the resistance value R11 of the detection resistor 101, that is, The insulation resistance value RPx can be obtained from n × R11 = RPx.

  The above is performed as follows in the circuit of FIG.

  That is, the signal 106 of the voltage V1 across the detection resistor 102 becomes the signal 119 via the insulation converter 109 → the signal 112 → the low pass filter 115 and is input to one of the dividers 125. Further, the signal 107 of the voltage V3 across the detection resistor 105 generated by the current IPX becomes the signal 120 through the isolation converter 110 → the signal 113 → the low pass filter 116, and is input to the other of the divider 25, and the polarity is discriminated. Input to the instrument 122.

  At this time, since the signal 120 is in the positive (+) direction, the polarity discriminator 122 discriminates the (+) direction and outputs a signal 123 that is turned on, and the divider 125 and the multiplier 131 are set in the calculation state. The display device 135 and the alarm device 136 are switched to the positive electrode side. Further, the signal 124 that is turned off causes the divider 126 and the multiplier 132 to be in a non-computation state, and locks the operations of the display device 135 and the alarm device 136 on the negative electrode side.

  By the above switching, the divider 125 outputs a signal 127 indicating V1 / V3, which is the ratio n of the signal 119 and the signal 120, and inputs the signal 127 to one of the multipliers 131. The constant setter 129 outputs a signal 130 for setting the set value K to the same value as the detection resistors R11 and R21, and inputs the signal 130 to the other of the multiplier 131. Therefore, the multiplier 131 multiplies the output signal 127 from the divider 125 and the signal 130 indicating the constant K from the constant setter 129 and outputs a signal 133.

Signal 133 is
RPx = n × K = (V1 / V3) × R11 (1)
And the insulation resistance value RPx to be obtained.

  In this equation, n is V1 / V3, and K is a constant having a value equal to the resistance value of the resistor 101.

  While this is given and displayed on the display device 135, the alarm device 136 issues an alarm when the insulation resistance value falls below a preset insulation resistance value, and records the output signal 137 in time series to time-series the insulation resistance value. Process changes for safety management, such as recording changes. As shown in FIG. 6, a measurement power source 138 and a power switch 139 are provided, and by using these, measurement of the insulation resistance of a power supply circuit, device, or apparatus in a non-energized state, that is, in a state not in a live line state. Is possible.

Next, the case where the insulation resistance is measured of the negative electrode sheet path.

In this case, the insulation resistance to be measured is RNx, and when the current INX flows therethrough, the insulation resistance value RNx to be obtained from the relationship similar to the above by replacing the resistor 102 with the resistor 104 is
RNx = n × K = (V2 / V3) × R21 (2)
Can be obtained as In this equation, n is V2 / V3, and K is a constant having a value equal to the resistance value R21 of the resistor 103.

In the circuit of FIG. 6, the signals 106, 112, 119, 127, and 133 are converted to the signals 108, 114, 121, 128, and 134, the arithmetic circuits 125 and 131 are switched to the arithmetic circuits 126 and 132, the signal 123 is turned OFF, and the signal 124 is switched off. the by replacing each to oN, it is possible to measure the insulation resistance RNx of the negative electrode sheet path in the same manner as the case of measuring the insulation resistance RPx of the positive electrode sheet path.

Assuming that the resistance value RPx = 1 MΩ of the insulation resistance, R11 = RPx = 1 MΩ, and R12 = R3 = 10 KΩ, from FIG. 7, V1 = V3 is approximately 1.65 V, and the ratio n between the two voltages is V1 / V3. since = the 1.65 / 1.65 = 1, as the insulation resistance RPx of the positive electrode sheet path, from the equation (1), can be obtained 1 M.OMEGA.

  Similarly, at the voltage ratio n = V1 / V3 = 10, RPx = (K = 1 MΩ) × (n = 10) = 10 MΩ is obtained from the equation (1) as the insulation resistance RPx. Similarly, when the voltage ratio n = V1 / V3 = 100, RPx = (K = 1 MΩ) × (n = 100) = 100 MΩ, and when the voltage ratio n = 0.1, RPx = (K = 1 MΩ) × (n = 0.1) = 0.1 MΩ can be obtained.

  When the voltage of the power supply 100 of the power feeding circuit varies, the currents IS, IPX and INX vary in proportion to this, and V1, V2 and V3 also vary, but the voltage ratios n = V1 / V3 and n = V2 / V3 does not change. Therefore, according to this conventional apparatus, even if the voltage of the power supply circuit to be measured fluctuates, the measurement value is not affected by this, and the advantage that the insulation resistance can be measured stably is obtained.

JP 2007-198330 A

However, the conventional apparatus described in Patent Document 1, when the time difference between the insulation resistance of the positive electrode sheet path and the negative supply path is large, the measurement error is small, the difference between the insulation resistance of the poles is small, the measurement error becomes large, there is a problem that the insulation resistance of the bipolar supply path becomes unmeasurable if the same value.

Shows the detection characteristics due to a change in the insulation resistance of the resistance ratio of the bipolar supply path in the conventional apparatus in FIG.

The horizontal axis of the detection characteristic diagram of FIG. 8 shows the ratio RNx / RPx or RPx / RNx insulation resistance RNx insulation resistance RPx and N-pole feeding path of the P-pole feed path and the vertical axis, due to T-type detecting circuit The ratio between the measured insulation resistance value and the actual insulation resistance value (measured resistance value of RPx / actual resistance value of RPx) and (measured resistance value of RNx / actual resistance value of RNx) are shown.

  If the positive-side insulation resistance RPx = 1, the negative-side insulation resistance RNx = 1, and the bipolar insulation resistances have the same value, the ground currents IPX and INX are equal, so the ground currents IPX and INX flowing through the detection resistor R3 cancel each other. Thus, the detection voltage V3 becomes 0, and the insulation resistance value obtained thereby becomes infinite, and the insulation resistances RPx and RNx cannot be measured.

  As is clear from FIG. 8, if the ratio between the insulation resistances RPx and RNx is 2, the ratio between the measured resistance value and the actual resistance value is 2, and the measurement error is doubled. However, when the ratio of the insulation resistances RPx and RNx is increased to 20, the ratio of the measured resistance value to the actual resistance value is 1.05, and the measurement error is reduced to 1.05 times.

  Therefore, an object of the present invention is to solve the problems in the conventional apparatus as described above, and to insulate the insulation resistance continuously without complicated measurement operation and without being affected by fluctuations in the power supply voltage. An object of the present invention is to provide an insulation resistance measurement method and measurement apparatus that can measure resistance stably and can perform high-accuracy measurement even when the difference in insulation resistance between both electrodes is small.

In order to solve such a problem, the invention according to claim 1 is the first resistor and the second resistor having the same high resistance between the positive electrode feeding path and the negative electrode feeding path of the ungrounded DC feeding circuit. Are connected in series to a low resistance third resistor, and a neutral point where these two resistance circuits are connected to each other is connected to a low resistance fourth resistor. T-type detection circuits that are grounded through each of them, and variable resistance means for adjusting the resistance values of the first resistor and the second resistor are provided in each pair of resistance circuits of the T-type detection circuit, respectively. The voltage generated at both ends of the third resistor of the two sets of resistor circuits and the voltage generated at both ends of the fourth resistor while adjusting the resistance value of each set of resistor circuits by the variable resistance means And the voltage ratio between the third resistor and the fourth resistor of one of the resistor circuits, Calculates the voltage ratio between the third resistor and the fourth resistor of the other set of resistor circuits, and either of these voltage ratios has the same value as the first resistor or the second resistor. A constant K value is multiplied to obtain the insulation resistance value of the two electrodes.

  In the first aspect of the invention, when one of the resistance values of each of the resistance circuits is increased by the resistance variable means, the resistance values of the other resistance circuit are complementarily complemented. It is preferable to measure the insulation resistance of both poles by alternately adjusting (invention of claim 2).

According to a third aspect of the present invention, a high-resistance first resistor and a second resistor having an equal value and a low-resistance third resistor are provided between a positive electrode feeding path and a negative electrode feeding path of a non-grounded DC feeding circuit. A T-type detection circuit in which two resistance circuits configured in series are connected in series, and a neutral point where the two resistance circuits are connected to each other is grounded via a fourth resistor having a low resistance; ,
Variable resistance means for adjusting the resistance value of the first resistor and the second resistor of each pair of resistance circuits of the T-type detection circuit;
Means for selectively giving each of the resistance variable means an operation command and selecting a measurement position;
Voltage detection means for detecting voltages generated at both ends of each of the third resistors and at both ends of the fourth resistor of each set of resistor circuits;
Wherein the first calculating means for calculating a voltage ratio of the voltage of the third resistor of the resistor of the positive feed line side and the fourth resistor, and the voltage of the third resistor of the resistor of the negative electrode feed line side first Second computing means for computing the voltage ratio of the four resistors;
A third arithmetic means for multiplying the first resistor or a constant K value equal to the resistance of the second resistor of the positive supply path side of the resistor circuit to a voltage ratio from the first calculating means, the second a fourth computing means for multiplying the first resistor or a constant K value equal to the resistance of the second resistor of the resistor of the negative electrode feed line side voltage ratio from the calculating means,
And display means for displaying each output of the third or fourth arithmetic means as an insulation resistance value.

  According to a third aspect of the present invention, when the resistance value of one set of resistance circuits is increased by the variable means of each set of resistance circuits, the resistance value of the other set of resistance circuits is complementarily reduced. It is preferable to provide a function of adjusting alternately (invention of claim 4).

  Polarity discrimination means for discriminating the polarity of the voltage generated in the fourth resistor is provided. When the polarity is positive, the calculation and display on the positive side can be performed and the calculation and display on the negative side are locked. When the polarity is negative, the polarity is negative. The calculation and display on the positive side can be performed and the calculation and display on the positive electrode side can be locked (invention of claim 5).

  Further, an alarm means for issuing an alarm upon determining that the insulation resistance value has fallen below a preset value may be provided (invention of claim 6).

According to the present invention, by the resistance variable means provided in the two resistance circuits of the T-type detection circuit for measuring the insulation resistance, one of the resistance values of each resistance circuit is increased and the other is decreased. a by adjusting complementary, since it is possible to measure with a great difference apparent to the resistance value of the insulation resistance of the bipolar supply path, the measurement error is reduced, it is possible to improve the measurement accuracy.

The circuit block diagram which shows the Example of this invention. Explanatory drawing of the measurement operation | movement of the insulation resistance in this invention. The figure which shows the relationship between the selection position of the measurement position selection switch in this invention, and the open / close state of the switch for resistance short circuits. Illustration of measurement operation of the insulation resistance of the positive electrode sheet path according to the present invention. Illustration of measurement operation of the insulation resistance of the negative electrode sheet path according to the present invention. The circuit block diagram which shows the conventional insulation resistance measuring apparatus. Explanatory drawing of the measurement operation | movement of the conventional insulation resistance measuring apparatus. The figure which shows the measurement characteristic of the conventional insulation resistance measuring apparatus.

  Embodiments of the present invention will be described with reference to the embodiments shown in the drawings.

  FIG. 1 is a block diagram showing an embodiment of the present invention.

  In FIG. 1, 1 is a DC power source, P is a positive electrode feeding path drawn from the positive electrode of the DC power source 1, N is a negative electrode feeding path, and RP is a series connection of detection resistors 3 (R1A) to 5 (R1C). A first resistance circuit (sometimes referred to as a positive resistance circuit) and RN are a second resistance circuit (also referred to as a negative resistance circuit) in which detection resistors 7 (R2A) to 9 (R2C) are connected in series. The two sets of resistance circuits RP and RN are arranged symmetrically so that the resistors 5 and 9 face each other, and are connected in series between the positive electrode feeding path P and the negative electrode feeding path N connected to the DC power source 1. The Furthermore, a T-type detection circuit is configured by connecting one end of the detection resistor 11 (R3) to a neutral point M where two sets of resistance circuits RP and RN are connected to each other and grounding the other end.

The resistance circuits RP and RN are provided in parallel with first switches PS1 and NS1 that short-circuit two resistors connected in series and second switches PS2 and NS2 that short-circuit one resistor, respectively. First switches PS1 and NS1 are connected in parallel to resistors 3, 4 and 7, 8 of each resistance circuit, respectively, and second switches PS2 and NS2 are connected in parallel to resistors 4 and 8, respectively. Such first switches PS1, NS1 and second switches PS2, NS2 serve as resistance variable means for adjusting the resistance values of the resistance circuits RP and RN by opening and closing .
A measurement position selection switch (sometimes simply referred to as a selection switch) 2 is used to select an electric circuit for measuring insulation resistance by rotating operation. Depending on the selection position, the first switch PS1 and NS1 and the second switch PS2 and NS2 are selected. Controls the opening and closing of.

Positive feed path P of the negative electrode poles, when measuring the insulation resistance of the N at the same time, placed in the normal measuring position selection switch 2 is indicated by "normally". When measuring the insulation resistance of the positive electrode sheet path P is placed in the positive electrode measurement position shown select switch 2 in the "P", and when measuring the insulation resistance of the negative electrode sheet path N is a selection switch 2 "N" Is placed at the negative electrode measurement position indicated by.

  FIG. 3 shows the relationship between the selection position of the selection switch 2 and the open / closed states of the switches PS1, NS1, PS2, and NS2. The selected positions “P”, “always”, and “N” in the horizontal direction in FIG. 3 indicate the switches PS1, PS2, NS1, and NS2 in the vertical direction. It indicates that it is (closed), and no mark indicates that the switch is off (open).

  As shown in FIG. 3, when the normal measurement position indicated by “always” is selected by the selection switch 2, the second switches PS2 and NS2 are turned on. As a result, the resistors 4 and 8 of the bipolar resistor circuits RP and RN are short-circuited.

  When the position “P” for measuring the insulation resistance of the positive electrode feeding path P is selected by the selection switch 2, the first switch NS1 of the negative resistance circuit RN is turned on (closed), and the two resistances of the negative resistance circuit RN are selected. 7 and 8 are short-circuited. When the position “N” for measuring the insulation resistance of the negative electrode feeding path N is selected by the selection switch 2, the first switch PS1 of the positive resistance circuit RP is turned on (closed), and the positive resistance circuit RP The two resistors 3 and 4 are short-circuited.

  Insulated voltage detectors 6, 10 and 12 are connected to both ends of each of the detection resistors 5 (R1C), 9 (R2C) and 11 (R31), and voltage detection signals V1, which are insulated from the primary side, respectively. V2 and V3 are obtained.

The detection resistor 11 is configured such that three resistors are connected in parallel via a contact that is opened and closed by the measurement range selector 13, and the resistance value R3 of the detection resistor 11 can be changed. The terminal voltage V3 can be changed according to the ranges 1, 2, and 3.

  These voltage detection signals V1 to V3 have their harmonic components removed by the low-pass filters 14 to 16, among which the signals V1 and V3 are supplied to the positive divider 17 and the signals V2 and V3 are supplied to the negative divider 18. And division is performed.

  Output signals SP1 and SN1 indicating the voltage ratios (n) V1 / V3 and V2 / V3 respectively output from the dividers 17 and 18 are applied to the multipliers 19 and 20, respectively, and set in the constant setter 21. It is multiplied by a constant SK indicating a resistance value equal to the resistance value R1A or R2A of the detection resistor 3 or 7. Output signals SP <b> 2 and SN <b> 2 of the multipliers 19 and 20 are processed by the monitoring recording device 22 and applied to the display device 23 and the alarm device 24.

  The polarity discriminator 25 discriminates the polarity of the signal V3 and generates an output that turns on the signal VP when the signal V3 is in the (+) direction, and an output that turns on the signal VN when the signal V3 is in the (−) direction. Is generated.

  When the polarity discriminator 25 outputs the signal VP in the (+) direction, the calculators 17 and 19 on the positive electrode side, the display device 23 and the alarm device 24 are operated to lock the negative electrode side. Similarly, when the polarity discriminator 25 outputs the signal VN in the (−) direction, the negative side calculators 18 and 20, the display device 23, and the alarm device 24 are operated to lock the positive side.

  FIG. 2 is an explanatory diagram for measuring the insulation resistance. With reference to this figure, the measuring method of insulation resistance is demonstrated.

  Here, the resistors 3 (R1A) and 4 (R1B) of the positive-side resistor circuit RP and the resistors 7 (R2A) and 8 (R2B) of the negative-side resistor circuit RN are selected to have the same resistance value. Resistors 5 (R1C) and 9 (R2C) are also selected to have the same resistance value. The resistance values of the resistors 3, 4, 7, and 8 are about 25 to 100 times as high as the resistors 5 and 9 having low resistance values. Select the optimum value according to the voltage value or the range of the insulation resistance value to be measured.

  For example, when measuring the insulation resistance of a feeding circuit with a DC voltage of 500 V, the resistance values (R1A, R1B, R2A, R2B) of the resistors 3, 4, 7, 8 are 33 kΩ and the resistance values of the resistors 5, 9 (R1C, R2C). ) Is selected to be 330Ω, and the resistor 11 is a resistor whose resistance value can be varied in the range of 1 to 10 kΩ in order to change the measurement range.

Place the selection switch 2 to the normal position indicated by "normal", the positive feed path P of the negative polarities, when selecting the measurement position of N second switches PS2 and NS2 of each resistor circuit is turned on, the high-resistance Value resistors 4 and 8 are short-circuited. Since RPx = RNx = ∞ when the insulation resistance is infinite, the currents IPX and INX flowing through the insulation resistances RPx and RNx shown in FIG. 2 do not flow. As a result, the voltages V1, V2 across the detection resistors 5, 9 are V1 = V2, and the current IS flowing through both resistance circuits RP and RN is
IS = V ÷ (R1A + R1C + R2A + R2C) ≈V ÷ (R1A + R2A)
It becomes.

  The potential of the neutral point M is VP = VN = 250V, and the resistance ratio between the resistors 3, 5 (R1C) and the resistors 3, 9 (R2C) is 1: 1/100. A voltage of 250V / 100≈2.5V is generated.

Now, the insulation resistance RPx of the positive electrode sheet path P of the power supply circuit is to have decreased, the ground circuit,
IPX = V ÷ (RPx + R31 + R2A + R2C)
A ground current IPX flows, and both ends of the detection resistor 11
V3 = IPX × R31
Is generated. At this time, the voltage V1 across the detection resistor 5 is determined by the current IS, and the voltage V3 across the detection resistor 11 is determined by the ground current IPX. That is, here, since the resistance value R1A of the resistor 3 and the resistance value RPx of the ground resistance are sufficiently larger than the resistance value R1C of the resistor 5 and the resistance value R31 of the resistor 11, respectively, the ratio of the detection voltages V1 and V3 is the resistance 3 Therefore, the voltage ratio n of the voltages V1 and V3 is obtained, and the ratio n is multiplied by the resistance value R1A of the detection resistor 3, that is, RPx = n * R1A = (V1 / V3) * R1A
From this, the insulation resistance value can be obtained.

  The above is performed as follows in the circuit of FIG.

  That is, the voltage V1 across the detection resistor 5 is input to one of the dividers 17 via the insulation detector 6 → the low pass filter 14. Further, the voltage V3 across the detection resistor 11 generated by the current IPX is input to the other of the divider 17 via the insulation detector 12 → low pass filter 16 and to the polarity discriminator 25.

  At this time, since the voltage V3 is in the positive (+) direction, the polarity discriminator 25 discriminates the (+) direction, turns on and outputs the signal VP, puts the divider 17 and the multiplier 19 in the calculation state, The display device 23 and the alarm device 24 are switched to the positive electrode side. Further, when the signal VN is turned off, the divider 18 and the multiplier 20 are put into a non-calculation state, and the operations on the negative side of the display device 23 and the alarm device 24 are locked.

  By the switching, the divider 17 outputs a signal SP1 indicating V1 / V3, which is a ratio n between the signal V1 and the signal V3, and inputs the signal SP1 to one of the multipliers 19. The constant setter 21 outputs a signal SK that makes the set value K the same as the resistance values R1A and R2A of the detection resistors 3 and 7, and inputs the signal SK to the other side of the multiplier 19. Accordingly, the multiplier 19 multiplies the output signal SP1 from the divider 17 and the signal SK indicating the constant K from the constant setter 21 and outputs a signal SP2.

The signal SP2 is an insulation resistance value RPx to be obtained, that is,
RPx = n × K = (V1 / V3) × R1A (3)
This is given to and displayed on the display device 23 via the monitoring and recording control device 22, while the alarm device 24 warns when this measured insulation resistance value falls below a preset insulation resistance value. The monitoring and recording control device 22 performs a process for safety management such as recording an insulation resistance value that changes in time series with the output signal SP2.

  As shown in FIG. 1, a power supply for measurement 38 and a power switch 39 are provided, and by using these, the electric circuit in a non-energized state in which the DC power source 1 of the power feeding circuit is cut off, that is, in a state where it is not in a live line state , It is possible to measure the insulation resistance of equipment or equipment.

When the negative-side insulation resistance RNx decreases, the current INX flows through the negative-side insulation resistance RNx, so that the insulation resistance value RNx to be obtained from the relationship similar to the above by replacing the resistor 3 with the resistor 7 is
RNx = n × K = (V2 / V3) × R2A (4)
Can be obtained as

  The circuit of FIG. 1 also replaces the signals V1, SP1, and SP2 with the signals V2, SN1, and SN2, the arithmetic circuits 17 and 19 with the arithmetic circuits 18 and 20, the signal VP off, and the signal VN on. The negative electrode side insulation resistance can be measured in exactly the same manner as when measuring the positive electrode side insulation resistance.

  In the circuit of FIG. 2, when the voltage of the power supply circuit fluctuates, the currents IS and IPX fluctuate proportionally and V1 and V3 also fluctuate, but the voltage ratio n = V1 / V3 does not change. Therefore, according to the present invention, even if the voltage of the power supply circuit to be measured fluctuates, the measurement value is not affected by this, so that there is an advantage that stable insulation resistance can be measured.

  Next, selection of the resistance values R1A to R2C of the resistors 3 to 5 and 7 to 9 will be described.

  In the above description, a case where a circuit having a voltage of 500 V is measured by setting the resistance values of the resistors 3, 4, 7, and 8 to 33 kΩ and the resistance values of the resistors 5 and 9 to 330Ω. At this time, when the insulation resistances RPx and RNx are infinite, the potential of the neutral point M is 250V, and the detection voltage V1 = V2≈2.5V.

  Here, when the voltage of 500V fluctuates in the range of 600V (+ 20%) to 400V (−20%), if the insulation resistances RPx and RNx are infinite, the detection voltage V1 = V2≈ fluctuates in the range of 3V to 2V. To do. However, since the detection voltage ratio n does not change, there is no influence on the measured value. When measuring the insulation resistance of a circuit with a voltage of 1000 V, the potential at the neutral point M is 500 V, and the detection voltage VR12 = VR22 = 500 / 100≈5 V. However, in this case as well, the detection voltage ratio n does not change. There is no effect on the measured value.

  Further, each resistance value is set to 1 MΩ for R1A, R1B, R2A, and R2B, the resistance ratio 1: 1/100 for the resistors R1C, R2C is set to 1: 1/100, that is, the resistance R1C, R2C is set to 20 KΩ. For example, if V1 and V2 are 2.5V to 5V, the resistance ratio is 1: 1/25, and the resistance RC and R2C = 40KΩ, the detection voltages of V1 and V2 are changed from 2.5V to 10V. Since the voltage ratio is unchanged, there is no effect on the measurement.

  In the above, the resistance values R1A, R1B, R2A and R2B are fixed and the resistance values R1C and R2C are changed. However, the resistance values R1C and R2C are fixed, and the resistance values R1A, R1B, R2A and R2B are changed. It goes without saying. That is, the resistance values R1A, R1B, R2A, R2B and R1C, R2C of the resistors 3, 4, 7, 8 and 5 and 9 can be selected to be optimum values in order to obtain the voltage of the measurement circuit and the optimum detection voltage. it can.

  Note that the present invention is intended for a non-grounded circuit, and cannot be applied to a one-wire grounded circuit because the insulation resistance to be measured is short-circuited, and the measurement position selection switch 2 is normally measured at the “normal” position. Since the set resistance measurement method at the position is the same as the conventional measurement method disclosed in Patent Document 1, if both the positive-side insulation resistance and the negative-side insulation resistance decrease to the same extent, a ground circuit (detection resistor) 11) It cannot be measured because no current flows.

  In the present invention, the measurement position selection switch 2 is set to the “P” position or “N” in order to accurately measure the insulation resistance even when both the positive side insulation resistance and the negative side insulation resistance of the power supply circuit are reduced to the same extent. Switch to position and perform measurement.

  Next, the method will be described.

When measuring the insulation resistance RPx of the positive electrode sheet path P side switches the measurement position selection switch 2 to the "P" position. Thereby, as shown in FIG. 3, only the first switch NS1 of the negative-side resistor circuit RN is turned on, and the other switches are turned off. As a result, in the negative resistance circuit RN, the two resistors 7 and 8 having a high resistance value are short-circuited, and only the resistor 9 having a low resistance value remains in the circuit. On the other hand, three resistors 3 to 5 connected in series remain in the positive-side resistor circuit RP.

  An equivalent circuit configuration in this state is shown in FIG.

At this time, the sheet path P, the resistance of the connected resistor circuit between N, the two high-resistance 3,4 and two next lower resistance 5,9, current IS flowing through the resistor circuit, the measurement described above This is the same as when the position selection switch 2 is switched to the normal measurement position indicated by “normal”. If the circuit voltage and the circuit constant are the same as described above, the voltages V1 and V2 generated in the detection resistors 5 and 9 are approximately 2.5 V, which is the same as the above case.

  However, the ground current IPX flowing through the positive-side insulation resistance RPx flows through the two low-resistance resistors 11 and 9, and the ground current INX flowing through the negative-side insulation resistance RNx is the two high-resistance resistors 3 and 4. Since the current flows through the two low resistance resistors 5 and 11, even if the insulation resistances RPx and RNx are equal, the ground current becomes IPX> INX, and the detection resistor 11 in the (+) direction according to the current difference between the two currents. A voltage V3 is generated. As a result, the polarity discriminator 25 of FIG. 1 generates an output that turns on the positive output VP.

Thereby, the divider 17 obtains the ratio n between the voltage V1 of the detection resistor 5 and the voltage V3 of the detection resistor 11, and the resistance value R1A of the resistor 3 or 4 set in the constant setter 21 or by multiplying the R1B equal constant K, it is possible to determine the insulation resistance RPx of the positive electrode sheet path P.

  In the state of FIG. 4, even if the insulation resistances RPx and RNx of both positive and negative electrodes are equal, the total resistance value of the two high resistance resistors 3 and 4 is added to RNx, and one low resistance is added to RPx. The resistance value of the value resistor 9 is added. For this reason, it is the same as the insulation resistance RPx is reduced by the resistance value of two resistances higher than RNx, and the apparent ratio RNx / RPx of both insulation resistances is increased.

  In this way, when there is a difference between the two insulation resistances and the ratio between the two increases, the measurement error decreases as can be understood from the measurement characteristics shown in FIG. 8, so that the measurement accuracy of the insulation resistance can be increased.

Next, the measurement position selection switch 2 by switching to the "N" position, it is possible to measure the insulation resistance RNx the negative supply path N.

  In this case, since the measurement position selection switch 2 is switched to the “N” position, only the first switch PS1 of the positive resistance circuit RP is turned on and the switch is turned off as shown in FIG.

  An equivalent circuit configuration in this state is shown in FIG.

  As is apparent from FIG. 5, the current IS flowing through the resistance circuit flows through the two low resistance resistors 5 and 9 and the two high resistance resistors 7 and 8. The current INX that flows through the negative-side insulation resistance RNx flows through the two low-resistance resistors 11 and 5, while the current IPX that flows through the positive-side insulation resistance RPx includes the two low-resistance resistors 11, 9 And two high resistance resistors 8 and 7.

  Accordingly, the resistance value of the insulation resistance RNx is relatively smaller than that of RPx, the ground current is INX> IPX, and the voltage V3 in the (−) direction is generated in the detection resistor 11. As a result, the polarity discriminator 25 of FIG. 1 generates an output that turns on the negative output VN.

Thereby, the divider 18 determines the ratio n of the voltage V1 of the detection resistor 5 and the voltage V3 of the detection resistor 11, and the multiplier 20 sets the ratio 7 to the resistance 7 or 8 set in the constant setting unit 21. by multiplying the resistance value R2A or R2B equal constant K, it is possible to determine the insulation resistance RNx the negative supply path N.

  Also in this case, since the ratio RPx / RNx of the positive insulation resistance RPx and the negative insulation resistance RNx can be apparently increased, the insulation resistance can be measured with high accuracy.

  In the above description, it is assumed that the measurement position selection switch 2 is manually switched. However, the first switches PS1 and NS1 and the second switches PS2 and NS2 for short-circuiting the resistance circuits RP and RN are automatically switched. May be.

In this case, by providing means for controlling the opening and closing of the first switch PS1 and NS1 regularly alternately at predetermined time intervals, accurate continuous positive and insulation resistance RPx and RNx the negative supply path alternately Can be measured and can be constantly monitored.

  In the present invention, as shown in FIG. 1, a plurality of resistors R32 and R33 are connected to the detection resistor 11 so that they can be switched in parallel, and the resistance value of the detection resistor 11 can be varied to adjust the measurement magnification. can do.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Measurement position selection switch 3, 4, 7, 8 High resistance detection resistors 5, 9, 11 Low resistance detection resistors 6, 10, 12 Insulation voltage detector 13 Measurement range selectors 14, 15, 16 Filters 17 and 18 Dividers 19 and 20 Multiplier 21 Constant setter 22 Monitoring and recording control device 23 Display device 24 Alarm device 25 Polarity discriminator 38 Power supply for measurement 39 Power switch PS1, NS1 First switch PS2 for resistance short circuit, NS2 Second switch for resistance short circuit

Claims (6)

A structure in which a high-resistance first resistor and a second resistor having the same value and a low-resistance third resistor are connected in series between a positive electrode supply path and a negative electrode supply path of a non-grounded DC power supply circuit. T-type formed by connecting two resistance circuits in series and grounding a neutral point where these two resistance circuits are connected to each other via a fourth resistor whose resistance value can be changed within a low resistance range A detection circuit, and variable resistance means for adjusting the resistance value of the first resistor and the second resistor in each set of resistance circuits of the T-type detection circuit,
When simultaneously measuring the insulation resistance of the positive electrode feeding path and the negative electrode feeding path using these resistance variable means, the first resistor or the second resistor of the two sets of resistance circuits are short-circuited, and the positive electrode feeding path or the negative electrode feeding is performed. When measuring the insulation resistance of the road , while short-circuiting the first resistor and the second resistor of either one of the resistor circuits,
Detecting each voltage generated at both ends of the third resistor of the two sets of resistor circuits, and voltage generated at both ends of the fourth resistor;
The voltage ratio between the third resistor and the fourth resistor in one set of resistor circuits, or the voltage ratio between the third resistor and the fourth resistor in the other set of resistor circuits is calculated. ,
A method of measuring an insulation resistance, wherein one of these voltage ratios is multiplied by a constant K value having the same value as that of the first resistor or the second resistor to obtain an insulation resistance value of the two electrodes.   When the resistance value of one set of resistance circuits of each set of resistance circuits is increased by the variable resistance means, the resistance values of the other set of resistance circuits are adjusted alternately and complementarily so as to be reduced. 2. The insulation resistance measuring method according to claim 1, wherein the insulation resistance of both electrodes is measured. A structure in which a high-resistance first resistor and a second resistor having the same value and a low-resistance third resistor are connected in series between a positive electrode supply path and a negative electrode supply path of a non-grounded DC power supply circuit. T-type detection circuit in which two sets of resistance circuits are connected in series and a neutral point where these two sets of resistance circuits are connected to each other is grounded via a fourth resistor whose resistance value can be changed within a low resistance range When,
Variable resistance means for adjusting the resistance value of the first resistor and the second resistor of each pair of resistance circuits of the T-type detection circuit;
When simultaneously measuring the insulation resistance of the positive electrode feeding path and the negative electrode feeding path , the first resistor or the second resistor of the two sets of resistance circuits is short-circuited, and the insulation resistance of the positive electrode feeding path or the negative electrode feeding path is measured. In this case, an electric path for measuring the insulation resistance by selectively giving an operation command to each of the resistance variable means is selected so that the first resistor and the second resistor of any one of the resistor circuits are short-circuited. Means to
Voltage detection means for detecting voltages generated at both ends of each of the third resistors and at both ends of the fourth resistor of each set of resistor circuits;
Wherein the first calculating means for calculating a voltage ratio of the voltage of the third resistor of the resistor of the positive feed line side and the fourth resistor, and the voltage of the third resistor of the resistor of the negative electrode feed line side first Second computing means for computing the voltage ratio of the four resistors;
A third arithmetic means for multiplying the first resistor or a constant K value equal to the resistance of the second resistor of the positive supply path side of the resistor circuit to a voltage ratio from the first calculating means, the second a fourth computing means for multiplying the first resistor or a constant K value equal to the resistance of the second resistor of the resistor of the negative electrode sheet path side voltage ratio from the calculating means,
Insulation resistance measuring apparatus comprising display means for displaying respective outputs of the third or fourth arithmetic means as insulation resistance values.   When the resistance variable means of each set of resistance circuits increases the resistance value of one set of resistance circuits from the resistance variable means by increasing the resistance value of each set of resistance circuits, the resistance value of the other set of resistance circuits The insulation resistance measuring apparatus according to claim 3, further comprising a function of alternately adjusting in a complementary manner so as to be reduced.   Polarity discrimination means for discriminating the polarity of the voltage generated in the fourth resistor is provided. When the polarity is positive, the calculation and display on the positive side can be performed and the calculation and display on the negative side are locked. When the polarity is negative, the polarity is negative. 5. The insulation resistance measuring device according to claim 3, wherein the calculation and display on the positive side are enabled and the calculation and display on the positive electrode side are locked.   6. The insulation resistance measuring device according to claim 3, further comprising alarm means for issuing an alarm upon determining that the insulation resistance value has fallen below a preset value.

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