JPS5937470B2 - Insulation resistance measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the insulation resistance to ground of each phase and the capacitance to ground of each phase of an entire three-phase AC system under operating voltage (under live wires). A5.

The present inventor previously proposed a method and device that enables the measurement of the total insulation resistance value and total capacitance value of the entire three-phase AC system. It is now possible to measure the overall total insulation resistance value and total static capacitance value.

However, it has been impossible to measure the ground insulation resistance values of each of the A, B, and C phases, which are important data in insulation management of a three-phase AC system. Therefore, an object of the present invention is to provide a method for measuring each phase-to-ground insulation resistance value and each phase-to-ground capacitance value of the entire balanced three-phase AC system j, and to provide a method for measuring insulation resistance that is practical as an instrument. The purpose is to provide equipment.

The present invention will be explained below with reference to the drawings.

Note that the present invention can be applied only to balanced power sources, and to simplify the explanation, the description will mainly be given to a balanced three-phase AC neutral point resistance grounding system. FIG. 1 is a measurement circuit diagram for explaining the measurement principle of insulation resistance measurement of the present invention.

The left half of this measurement circuit (to the left of the dashed-dotted line in the figure) is an equivalent circuit of the three-phase AC power supply and ground impedance of the system to be connected, and the right half (to the right of the dashed-dotted line in the figure) is the equivalent circuit of the insulation resistance trace of the present invention. This is an equivalent circuit for explaining the Yodo principle. Symbols used in the figures and in the following description are specified in Table 1.

The equivalent circuit when SWO is on in the measurement circuit of Fig. 1 is shown in the second figure, and since the circuits are similar when SWl is on, SW2 is on, and SW3A is off, only the equivalent circuit when SWl is on is shown in Fig. 3. show.

These equivalent circuits have impedances YA, YB. ,YC
? and Y are defined as follows.

However, in three-phase AC, the following relational expression always holds. ●
●●● Each voltage AZVBi, VCL and VE! (However, i = 0, 1
, 2, and 3) have a phase difference from each other, so consider each voltage as a vector and take the voltage between any two phases, for example, EB-Ec as a reference vector, and calculate the voltage as shown in Figure 4. Each voltage vector At, VBz, Ci, i has a phase difference with the reference vector as θAt, θBi, θCt, θE・i
If the sizes are VAi, VBi, O2, and EL, then the following equation holds true.

for simplicity Put it as.

In order to obtain the total insulation resistance value R and the total capacitance value C, two formulas from the above middle 2), (3), (4), and (5) are necessary and sufficient, and how to select these two formulas is as follows. Since only equation (2) when SWO is on is different from the other three equations, equation (3),
The first selection method selects two equations from the three equations (4) and (5), and the second selection method selects equation (2) and one equation from the three equations (3), (4), and (6). There are ways to choose. For example, when formulas (4) and (5) are selected in the first selection method, Y can be typically expressed as follows by using formula (9).

In the second selection method, for example, when formulas (2) and (3) are selected, Y can typically be expressed as follows.

Since the power supply is now balanced, however, the absolute value of each phase voltage is established for VO, and since EB-Ec is taken as the reference vector, the line voltage BC between the B phase and C phase is as follows.

Therefore, when using equation (10), equation (13) can be changed to (10)
Comparing the real and imaginary parts of equation (14), we obtain the total insulation resistance value R and the total capacitance value C.
is obtained as shown below.

It is also possible to obtain R and C using equation (11), and by substituting equations (7), (8), and (12) into equation (11), the following equation is obtained, and this equation (7 ) and compare the real and imaginary parts of R<! :． C is required.

Next, the insulation resistance value for each phase, which is the object of the present invention, is determined using the relational expressions when SW2 is on and when SW3 is on.

Now, if we rearrange {(4)×B3−(5)XVB2 using equation (6), we get equation (20)'. is the formula (1), (
7) and (12) and divide it into real and imaginary parts and get the following.

Here, the ground capacitance of each phase is assumed to be equal, so it holds true, and if we set the right side of equation (21) as P + JQ, then (21) becomes, and from this equation (23), ωCO can be eliminated, so the following equation is obtained.

Therefore, the ground insulation resistance value RB of the B phase is expressed by equations (15) and (2
4), it can be obtained using the following formula.

Similarly, {(4)XVC3-(5)XVC2 is expressed as
), we get
By using (7) and (12) and dividing into real and imaginary parts, we obtain the following.

Since Equation (22) holds true, the right side of Equation (27) can be written as M
+JN, and since ωCO can be eliminated from this equation (28), the following equation can be obtained.Therefore, the ground insulation resistance value R of the C phase.

I can't stand it.

is the following formula.Finally, the ground insulation resistance value RA of group A is determined by formulas (25) and (30
) is determined by the following formula from RB and Rc.

As described above, the ground insulation resistance value of each phase is calculated by formula (15),
It is obtained from (25), (30), and (31).

Further, the ground capacitance of each phase can be obtained from equations (16) and (22) using the following equation. On the other hand, it is also possible to find the ground insulation resistance value of each phase using the relational expression when SWO is on and when SWl is on, and it is found using the same method as the above solution for when SW2 is on and SW3 is on. be able to.

In the end, in the insulation resistance measuring method of the present invention, the known numbers γ, γ0
, ω, and ρ, the minimum required detection values are as follows. 1) One line voltage value between any two of the three phases (e.g. JVO) 2) When SWO is on, when SWl is on, S
For any two times when W2 is on and when SW3 is on, any two of the four voltages to ground of each phase's voltage to ground A, 3, O, and voltage to ground E between NE 4 voltage values (
Example: B,,B3,゜! 2 ・VC3) 3) 4 phase differences between the line voltage in 1) and the ground voltage in 2) (Example: 52・53, θC2・θ03) Therefore, in the insulation resistance measurement method of the present invention, each phase is In order to measure the ground insulation resistance value and the ground capacitance value for each phase, the voltage balance of each phase is balanced by connecting or disconnecting a measurement resistor γ to at least one phase of each phase of group A, group B, and group C. and the four ground voltages (
A, B, C, and polar point ground voltages) are changed to at least two different values, and two of the four ground voltages at that time and a reference vector (e.g. VBC
) is necessary to detect the phase difference between the two.

The present invention can not only be used in the balanced power supply three-phase AC neutral point resistance grounding system described above, but also can be applied and modified as described below.

1) The present invention can be used not only for neutral point resistance grounding but also for ungrounded systems, in which case the neutral point grounding resistance γ.

Considering that is infinite, the above equation can be used as is by setting 1/γo=0. However, in the case of a non-grounded system, E cannot be used to measure the insulation resistance value of each phase. 2) The present invention can also be used in a neutral reactor grounding system, in which case the neutral grounding resistance γ.

It is sufficient to simply replace j(t)L with reactance j(t)L. 3
) The value of the measuring resistor γ connected to each phase of A, B, and C is the same value, but the purpose of connecting the measuring resistor is to measure the ground voltage of each phase and the neutral point. Since the purpose is to upset the balance of the ground voltage and change the ground voltage ratio to at least two different values, the values of the measurement resistors γ connected to each phase do not need to be the same value.

Therefore, for example, a method of connecting the measuring resistor as shown in FIG. 5 is possible. A, b, and c in Figure 5 are methods for connecting or disconnecting the measuring resistor to any one of the A, B, and C phases, and Figure 5 d is a method for connecting or disconnecting the measuring resistor to any one of the A, B, and C phases. This is a method when the values of the connected measurement resistors are different. 4) To the above description of the present invention}
In this case, the measurement resistance γ is a real resistance, but it can be replaced with an impedance element including reactance or capacitance, and R and C can be obtained in the same manner as in the above method.

5) In the above description of the present invention, voltmeters are connected to all of the A, B, and C phases, but it is sufficient to provide voltmeters to at least two phases, and it is not necessary to provide voltmeters to all phases.

If voltmeters are not installed on all phases A, B, and C, the above formula (
If the internal resistance ρ of the phase in which no voltmeter is installed in 1) is assumed to be infinite, analysis can be performed in the same manner as the above method. FIG. 6 shows a block diagram of an embodiment of the insulation resistance measuring device according to the present invention. Of the phase voltmeters 31, 32, and 33 provided for each phase of A, B, and C, two-phase voltmeter 3 for phase A and phase B
Choose 1,32. These phase voltmeters 31 and 32 output signals of A-phase and B-phase ground voltage values. The line voltmeter 34 that receives these output signals outputs signals of A-phase and B-phase line voltage values. The phase difference meter 35 receives the output signal of each phase voltmeter 31 and the output signal of the line voltmeter 34, and outputs a signal indicating the phase difference between the A-phase ground voltage and the line voltage (reference vector) between A and B. Output. The phase difference meter 36 receives the output signal of each phase voltmeter 32 and the output signal of the line voltmeter 34 and outputs a signal representing the phase difference between the B-phase ground voltage and the line voltage between A and B. These phase voltmeters 31, 32, line voltmeter 34,
The arithmetic unit 37 that receives the output signals of the phase difference meters 35 and 36 determines the ground insulation resistance settings RA, RB, and RA of each phase from these detected values.
Rc, and the ground capacitance C of each phase. is calculated and a signal of the calculated value is output. The display device 38 which received the output signal from the calculation device 37 displays the calculation value Re. , RBL, RC, and CO are expressed as equivalent resistance values, for example. Also, calculation device 3
The recording device 39 that receives the output signal from 7 continuously records the calculated values to show changes over time. For measuring various voltage values
and the ground capacitance CA, CB, CC of each phase of A, B, and C.
The discharge time of the battery should be considered, and it is desirable to measure the various voltage values after the voltage fluctuations have subsided. As explained above, according to the present invention, it is possible to measure the ground insulation resistance value of each fence and the ground capacitance value of each phase in the entire three-phase AC system by placing it under the live wire. It is now possible to manage the insulation of each phase of the system, and it is also possible to save labor in insulation measurements and inspections by continuously monitoring insulation values.

[Brief explanation of the drawing]

FIG. 1 is a measurement circuit diagram for explaining the principle of the present invention. Figure 2 is an equivalent circuit of the measurement circuit shown in Figure 1 when SWO is on. Figure 3 is an equivalent circuit of the measurement circuit in Figure 1 when SWl is on. FIG. 4 is a ground voltage vector diagram when EBEc is taken as a reference vector. FIG. 5 is a diagram showing the connection force method for Okiyodo resistance γ. FIG. 6 is a block diagram of an embodiment of the insulation resistance measuring device 0 according to the present invention. [Number explanation] 31, 32,
33...Each phase voltmeter, 34...Line voltmeter, 35,
36...Phase difference meter. 37... Arithmetic device, 38... Bale display device, 39... Recording device.

Claims (1)

[Claims] 1. A method for measuring each phase-to-ground insulation resistance value and each phase-to-ground capacitance value of a three-phase AC system, comprising: a) phase A, phase B, phase C, and power supply neutral; (b) changing the ratio between each of the ground voltages at the points to at least two different ratios, and (b) for each case when the ratio of the ground voltages is a first ratio and a second ratio Line voltage between two phases selected from three phases, A phase, B phase, C phase, and two ground voltages selected from four phases, A phase, B phase, C phase, and power supply neutral point, measuring the phase difference between the line voltage and the two ground voltages, and c) calculating each phase ground insulation resistance value and each phase ground capacitance value using the measured values. An insulation resistance measurement method consisting of steps. 2. At least one measuring impedance used to change the ratio between the A-phase, B-phase, C-phase and each ground voltage of the power supply neutral point of a three-phase AC system to at least two different ratios; The impedance for measurement is A phase, B phase, C
A switching device that connects or disconnects at least one of the phases, a line voltage measuring device that measures the line voltage between two selected phases out of the three phases, and a line voltage measuring device that measures the line voltage between the three phases and the power supply neutral point. a ground voltage measuring device that measures two ground voltages selected from among the ground voltages; a phase measuring device that measures a phase difference between the line voltage and the two ground voltages, and the voltage ratio is a first ratio. and the second ratio, each phase-to-ground insulation resistance value and each phase-to-ground insulation resistance value of the three-phase AC wiring are determined using the measured values obtained from the line voltage device, the ground voltage device, and the phase measuring device. An insulation resistance measuring device consisting of a device for calculating capacitance values.