JPH0690245B2 - Insulation deterioration related quantity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a cable, an electric device (for example, a transformer).
Insulation resistance, dielectric loss tangent, etc., and insulation deterioration related quantities such as water tree current due to cable insulation deterioration are in a live state, that is, a state where power is being supplied to the cable or a state where power is being supplied to electrical equipment. The present invention relates to an improvement of an insulation deterioration related quantity measuring device capable of measuring.

(Prior Art) Conventionally, as a means for measuring the amount of insulation resistance and dielectric loss tangent related insulation deterioration of a circuit to be measured such as a cable or an electric device, power is supplied with the cable or the electric device in a non-energized state. There is known a method in which a high voltage of alternating current or direct current is applied to a circuit to be measured and the insulation deterioration related amount such as insulation resistance and dielectric loss tangent is measured.

Next, as a means of measuring the insulation deterioration related amount in a live state, for example, in order to measure the insulation resistance of the CV cable in a live state, superimpose a DC low voltage on the GPT neutral point, There is a method in which a direct current component current flowing through a ground wire between the shield copper and the ground is measured to measure an insulation resistance as an insulation deterioration related amount. Also, as an insulation deterioration related quantity measuring device that measures the water tree current of the CV cable as the insulation deterioration related quantity, an AC voltage is applied to detect the DC component current flowing in the ground wire between the shielded copper and the ground. There are some that are designed to be measured.

(Problems to be solved by the invention) By the way, as an insulation deterioration related amount measuring device, it is desirable to be able to measure a CV cable, an electric device, etc. in a live state, however, a conventional CV cable is used. In order to measure the insulation resistance of the GPT in a live state, superimpose a DC low voltage on the GPT neutral point, measure the DC current component flowing in the ground wire between the shielded copper of the CV cable and the ground, and check the insulation deterioration relationship. When measuring the insulation resistance (sheath resistance) as a quantity, if a stray current due to the battery action or a water tree current due to insulation deterioration occurs, the DC low voltage applied to the GPT neutral point Since the DC measurement current based on this is superposed with the stray current due to the battery action and the water tree current due to insulation deterioration, the measured insulation resistance value includes errors due to the stray current due to the battery action and the water tree current. There is a problem.

In addition, in order to measure the water tree current of the CV cable as an insulation deterioration related amount, in the case of detecting the DC component current flowing in the ground wire between the shield copper and the ground by applying an AC voltage, the stray current is If so, there is a problem described below.

As shown in FIGS. 1 and 2, for example, a CV cable 1
Covers the conductor 2 with the inner semiconductor layer 3 and the outer semiconductor layer 4
A cross-linked polyethylene 5 as an insulator is interposed between the inner semiconductor layer 3 and the inner semiconductor layer 3, the outer semiconductor layer 4 is covered with a shielding copper tape 6 to be shielded, and a pressing cloth 7 is wound around the shielding copper tape 6 and the pressing is performed. It is formed by covering the cloth 7 with an insulating vinyl sheath 8. As shown in FIG. 3, the CV cable 1 is provided with three structural bodies including the shielding copper tape 6, the shielding copper tapes 6 are brought into contact with each other, and the pressing cloth 7 is wound around the three structural bodies. The pressing cloth 7
Is a CV cable in which an insulating vinyl sheath 8 is covered. In addition, a so-called triplex type CV cable (CV
There is also T). Reference numeral 9 is an inclusion.

When the CV cable 1 is insulation deteriorated, a water tree current I _i is generated as shown in FIG. In the example shown in FIG. 4, the shielding copper tape 6 side is + potential, and the conductor 2 side is −potential. Moreover, it may flow in the opposite direction. In order to measure this water tree current I _i, as shown in FIG. 5, the shield copper tape 6 on the other side of the CV cable 1 having one side connected to the high voltage distribution line 10 and the other side connected to a load is grounded. A wire 11 is drawn out, and a measuring device 12 for measuring a water tree current I _i as an insulation deterioration related amount is connected in the middle of the ground wire 11. The measuring device 12 is roughly composed of a detection resistor 13, an amplifier 14 having a filter, and a recording device 15.

However, there is a battery acting electromotive force E _S between the insulating vinyl sheath 8 and the ground, and a commercial frequency electromotive force E _AC due to the unbalance of the system load between the ground wire 17 of the GPT 16 and the ground.
There is a battery action electromotive force E _{E in} the grounded part of PT16. FIG. 6 shows this state by an equivalent circuit. In FIG. 6, R _i is the insulation resistance including the crosslinked polyethylene 5 of the CV cable 1, R _S is the sheath resistance of the insulating vinyl sheath 8, and the electromotive force E _i and the insulation resistance R _i are connected in parallel with the capacitor C. _It is considered that there is _{i, and} that there is a capacitor C _{S in} parallel with the battery electromotive force E _S and the sheath resistance R _S. These electromotive forces
When E _S , E _E , and E _AC are present, stray currents I _S , I _E , and AC current I _AC are generated, and the stray currents I _S and I _E are DC current components I together with the water tree current I _i. Will flow to. The sixth
FIG. 7 shows an equivalent circuit rewritten by paying attention to only the direct current component I of the equivalent circuit shown in the figure.

The stray currents I _S and I _E as DC current components are shown in FIG.
Is shown flowing with the water tree current I _i . This stray current I _S , I _E is the resistance R _S , R _E
The stray current I _E can be removed by sharing the ground wire 11a between the measuring device 12 and the ground with the ground wire 17 of the GPT 16, which is determined by E _S and E _E. Therefore, considering the stray current I _S , the electromotive force E _i of the water tree current I _i is usually about several tens of volts or less, and the battery acting electromotive forces E _S , E _E are about 0.5 V or less. The insulation resistance R _i is less than several hundred thousand MΩ, the sheath resistance R _S is smaller than the normal insulation resistance, and the sheath resistance R _S is 20
When it is 0 MΩ or more, the stray current I _S is 2.5 nanoamps or less, whereas in the deteriorated CV cable, the water tree current I _i is several tens of nanoamps or more. _Although it is not necessary to consider _S , the sheath resistance R _S greatly varies depending on environmental conditions and the like, and when the sheath resistance R _S is 200 MΩ or less, the contribution of the stray current I _S becomes relatively large and the stray current I _S It becomes impossible to discriminate whether or not the water is being measured for the water tree current I _i . In such a case, if the sheath resistance R _S can be measured without being affected by the DC component current, the water tree current I _i can be accurately measured. It is desirable to be able to measure the insulation resistance (sheath resistance is also used in the sense of insulation resistance) as a quantity related to insulation deterioration without being affected.
In FIG. 5, 18 is a power source, 19 is a ground wire drawn from the shielded copper tape 6 on one side of the CV cable 1, and 20 is a switch opened at the time of measurement.

The present invention has been made in consideration of the above circumstances, and an object thereof is to reduce an insulation resistance to a DC component current without being affected even when a DC current component flows in a circuit to be measured. Another object of the present invention is to provide an insulation deterioration related quantity measuring device capable of measuring at the same time.

Configuration of the Invention (Means for Solving the Problems) In order to achieve the above-mentioned object, the insulation deterioration related quantity measuring device applies a low frequency voltage to a measurement target circuit whose insulation deterioration related quantity is measured. A low-frequency voltage applying section to apply, a low-frequency current detecting section to detect a low-frequency current flowing through the circuit to be measured based on the low-frequency voltage, and an insulation resistance in synchronization with the low-frequency voltage applying section. A low-frequency reactive current generator that generates a low-frequency reactive current that does not contribute to the input, the low-frequency current and the reactive current are input, the low-frequency current and the reactive current are superimposed to detect a difference, and insulation A differential circuit that controls the low-frequency reactive current generator so that the low-frequency current is minimized in order to extract the effective component current that contributes to resistance, and that outputs the effective component current toward the insulation resistance calculator. And the insulation resistance A recording unit that records the insulation resistance based on the output of the arithmetic unit; and an ultra-low frequency voltage applying unit that applies an ultra-low frequency voltage to the measurement target circuit that has a negligible effect on the AC impedance component of the measurement target circuit. , A DC component current detection unit that detects a DC component current flowing through the circuit to be measured based on the ultra low frequency voltage, and an insulation resistance and a DC component current based on the detection output of the DC component current detection unit And a timing control unit that controls the timing of the calculation unit, the ultra-low frequency voltage application unit, and the DC component current detection unit to obtain the DC component current and the insulation resistance. It was.

(Embodiment) Hereinafter, a first embodiment of the insulation deterioration related amount measuring device according to the present invention will be described with reference to FIGS. 8 to 12.

In FIGS. 8 and 9, reference numeral 30 denotes a circuit to be measured whose insulation deterioration related amount is measured. The circuit 30 to be measured is the CV cable 1 here, but it may be a transformer or other electrical equipment. Reference numeral 31 is an insulation deterioration related amount measuring device for measuring the insulation deterioration related amount of the measurement target circuit 30. The insulation deterioration related amount measuring device 31 can measure even when the measurement target circuit 30 is in a live state, and the insulation deterioration related amount measuring device 31 includes a low frequency voltage applying unit 32 and a low frequency current detecting unit 33. , Low frequency reactive current generator 34, differential circuit 35, insulation resistance calculator 3
6, insulation resistance recording unit 37, dielectric loss tangent calculation unit 38, dielectric loss tangent recording unit 39, DC current component detection unit 40, DC component recording unit 41,
Ultra-low frequency voltage application unit 70, DC component current detection unit 71, operation unit 72 and timing control unit 73, insulation resistance recording unit 74,
And a DC component current recording unit 75.

The low frequency voltage application unit 32 has a function of applying a sine wave voltage as a low frequency voltage to the measurement target circuit 30. Target circuit
When the sine wave voltage V _F is applied to 30, a sine wave current I _F as a low frequency current flows through the measurement target circuit 30. This sine wave current _IF is the insulation resistance as shown in Fig. 10 and Fig. 11.
It consists of an effective component current Iu that contributes to R _S and R _i and a reactive component current Im that does not contribute to insulation resistance. The low frequency current detector 33 has a resistance R _P
Is a schematic configuration of an amplifier 42 and filter 43 has a function of detecting a sinusoidal current I _F.

The amplifier 42 on the basis of the sinusoidal current I _F, the voltage V _T corresponding to the sinusoidal current I _F 'is input, the amplifier 42 is the voltage V _T'
Is amplified β times to output a voltage of βV _T ′ to the filter 43, and the filter 43 outputs a DC component voltage βV _T to a differential amplifier described later. Low-frequency reactive current generating section 34 has a function of generating a reactive current Im 'cancellation of sinusoidal current I _F in synchronization with the low-frequency voltage applying unit 32. The low frequency reactive current generator 34 is roughly composed of a resistor r, a capacitor c, an amplifier 44 and a gain control circuit 45. The amplifier 44 'is applied, the amplifier 44 alpha] V _C by multiplying the detected voltage alpha' detection voltage V _C based on the reactive current Im having a function of outputting a voltage of the gain control circuit 45. The differential circuit 35 is composed of a differential amplifier 46 and a partial circuit 36 'of the insulation resistance calculator 36. The output voltage βV _T of the filter 43 is applied to the differential amplifier 46.
And the voltage α V _C of the gain control circuit 45 are input, and it has a function of outputting the difference voltage V _x to the insulation resistance calculation unit 36 and the dielectric loss tangent calculation unit 38 via the partial circuit 36 ′.

A part of the differential voltage V _x is fed back to the gain control circuit 45, and the low frequency current and the reactive current are input to the differential circuit 35, and the low frequency current and the reactive current Im are superimposed to detect the difference. The low-frequency reactive current generator 34 is controlled so that V _x is minimized in order to extract the active component current Iu, and the active component current Iu is output to at least the insulation resistance calculator 36. According to the insulation deterioration related quantity measuring device of the present invention, the effective component current Iu is The reactive current Im is Insulation resistance R _i is Is required as.

The insulation resistance calculation unit 36 has a function of calculating an insulation resistance value and outputting the calculation result to the insulation resistance recording unit 37. The dielectric loss tangent calculation unit 38 calculates a dielectric loss tangent value and calculates the calculation result as a dielectric loss tangent. It has a function of outputting to the unit 39.

Since it is possible that a low frequency has already flowed in the measurement target circuit 30 before the low frequency voltage is applied, the effective current is measured in advance before the low frequency voltage is applied, and then the low frequency voltage is applied. It is preferable to measure the effective resistance current Iu by applying it and determine the insulation resistance value based on the difference between the effective resistance current Iu and the accurate measurement of the insulation resistance. Further, if the frequency of the low frequency is low, the AC impedance becomes large, so that the reactive component current Im becomes small and the difference from the size of the effective component current Iu based on the insulation resistance R _i becomes small, so that the measurement accuracy is improved. However, the low frequency is preferably 1 Hz to 10 Hz. Further, although the sine wave is used as the low frequency in this embodiment, a triangular wave or a rectangular wave may be used.

Below, the CV cable 1 using the low frequency according to the present invention
The results of the sheath resistance measurement and the results of the conventional insulation resistance measurement device are shown in the table.

The CV cable 1 has a total length of 40 meters and a cross-sectional area of 22 mm.
² was used, and the insulation resistance measuring instrument used was one for applying 1000 V, and the sheath resistance was measured while artificially changing. The unit is megohm.

The ultra low frequency voltage application unit 70 has a function of applying the rectangular wave voltage V as the ultra low frequency voltage to the measurement target circuit 30. Here, the frequency of the rectangular wave voltage V is set so that the influence on the AC impedance component of the measurement target circuit 30 can be ignored.
For example, a rectangular wave voltage having a frequency of about 0.02 Hz or less is used. When the rectangular wave voltage V is applied to the measurement target circuit 30, a DC component current flows through the measurement target circuit 30. The DC component current detection unit 71 has a function of detecting a DC component current flowing through the measurement target circuit 30, and the calculation unit 72 isolates the DC component current from the DC component current based on the detection output of the DC component current detection unit 71. It has a function to calculate the resistance and the timing control unit 73
Has a function of controlling the ultra low frequency voltage application unit 70, the DC component current detection unit 71, and the calculation unit 72.

Next, measurement using ultralow frequencies according to the present invention will be described with reference to FIG.

The DC component current originally flows in the measurement target circuit 30 in the live line state. First, in the section I before the rectangular wave voltage V is applied, the DC component current I flowing in the measurement target circuit 30 is measured. Measure ₁ . Next, in section II, a positive rectangular wave voltage V ₂ is applied. At this time, the DC component current flowing in the measurement target circuit 30 is I _2, and the resistance obtained by the measurement in this section II, for example, the sheath resistance is R _S2 .
At this time, the sheath resistance R _S2 , the DC component currents I ₁ and I ₂ , and the rectangular wave voltage V ₂ satisfy the following relational expression.

Then, the application of the rectangular wave voltage V is stopped in the section III, the DC component current I ₃ in the section III is measured, and then the negative rectangular wave voltage V ₄ is applied in the section IV. At this time, the DC component current flowing in the circuit under measurement 30 is I ₄ , and this section
Let R _S4 be the resistance obtained by the measurement of IV, for example, the sheath resistance. At this time, sheath resistance R _S4 and DC component current
The following relational expressions hold for I ₃ , I ₄ , and the rectangular wave voltage V ₄ .

Therefore, the average sheath resistance R _S is Is required as.

In addition, the section V is a section in which no ultra low frequency voltage is applied as in the sections I and III, the reference numeral 15 indicates a DC component current in this section when no ultra low frequency voltage is applied, and the section VI is a section. A case where an ultralow frequency voltage is applied is shown in the same manner as in II and section IV, and the symbol V6 indicates a positive rectangular wave voltage. Here, for the sections V and VI and thereafter, since the measurement is repeated only from the section I to the section IV, the detailed description thereof will be omitted. As the number of repetitions increases, the average sheath resistance R _S can be calculated more accurately.

The timing controller 73 controls the DC component currents I ₁ , I ₂ , I ₃ , I ₄ , the sheath resistances R _S2 , R _S4 in each section, and the average sheath resistance R _S.
In order to obtain the above, the ultra low frequency voltage applying unit 70, the DC component current detecting unit 71, and the calculating unit 72 are controlled. The sheath resistance R _S thus obtained is used as described below. For example, the sheath resistance R _S is artificially changed, at least three sets of the sheath resistance R _S and the corresponding DC component current I are obtained, and the obtained DC component current I and the sheath resistance are obtained.
Obtained relation curve shown in Figure 13 of a combination of R _S, when to estimate the DC component current I of extreme increasing side of the sheath resistor R _S, water is also in a state that includes the stray currents I _S The tree current I _i can be measured.

Further, the insulation deterioration related amount measuring device 31 according to the present invention can simultaneously and continuously measure the water tree current I _i , the cable insulation resistance R _i , and the sheath resistance R _S. FIG. water flows to the ground line 11 of the CV cable 1 with insulation degradation related quantity measuring device 31 according to the tree current I _i and the insulation resistance R _i
FIG. 11 shows a connection circuit diagram in the case where the sheath resistance R _S and the sheath resistance R _S are continuously measured. One side of the insulation deterioration related amount measuring device 31 is connected to the ground line 11, and the other side is connected to the ground line 17. ,
AC in the have and DC impedance characteristics of less than several tens of Ω is interposed a capacitor C having a high impedance characteristic of more than about 200MΩ in the middle of the ground line 17, the high-pressure distribution line sine wave current I _F 17 And the earth, and the current is returned to the insulation deterioration related quantity measuring device 31, and the current I ′ flowing based on the ultra-low frequency is also circulated via the high-voltage distribution line 10 and the earth. If the insulation deterioration related amount measuring device 31 is connected to, the total resistance of the measurement target circuit 30 measured based on the ultra-low frequency is R _a , and the total resistance measured by the low frequency is R _b. Resistance R _S , insulation resistance
R _i is obtained by solving the following equation.

Here, the resistance R is a DC resistance component of the capacitor C.

Further, the insulation deterioration related amount measuring device 31 according to the present invention,
It can also be used to simultaneously measure the water tree current I _i and the insulation resistance R _i flowing in the ground wire 11 of the CV cable 1 at two different frequencies, as shown in FIG. 32, only the ultra low frequency voltage applying unit 70 of the measurement target circuit 30
It is provided on the ground wire 17 of the GPT16, and the insulation deterioration related quantity measuring device 31 including the remaining circuit parts 33, 34, etc. is connected to the ground wire 11 as it is, that is, it is connected to the shielding copper tape 6 of the CV cable 1. Place, yet so that the capacitor C for cutting bypassed allowed and stray current I _S of the commercial frequency 'were configured interposing the ground line 17, the capacitor C' for cutting the stray current I _S by interposing a It is the one.
If only the insulation resistance R _i is measured, the capacitor C '
Is unnecessary.

Further, the insulation deterioration related quantity measuring device 31 according to the present invention is CV
It is also possible to continuously measure the insulation resistance R _i and the capacitance C _{i of the} cable 1 continuously, as shown in FIG.
A switch 51 is provided on the ground line 17 of the GPT 16, a connection line 52 is drawn from the high potential side of the switch 51, a connection line 53 is drawn from the low potential side of the switch 51, and a capacitor C ₄ and a variable resistor are connected in parallel with the switch 51. R ₄ is provided, and the resistor R ₁ and the low frequency voltage applying unit 32 are connected in the middle of the connecting line 52, and the resistor
R ₁ is connected to the shielding copper tape 6 via the ground wire 11, and a variable resistor R ₂ is connected between the connection wire 53 and the middle of the connection wire 52 connecting the low frequency voltage applying section 32 and the resistor R _1. and, by connecting the low-frequency current detector 33 in the connecting line 53 and the ground line 11, the bridge circuit shown in the equivalent circuit in FIG. 17 constitute a sinusoidal current I _F of the low-frequency current detector 33 is zero The following formula is established depending on the parallel condition of the bridge.

In this equation, assuming that the real part and the imaginary part are equal, the insulation resistance R _i and the electrostatic capacitance C _i of the CV cable 1 are respectively calculated by the following formulas.

The variable resistor R ₂ and the variable resistor R ₄ are, for example, the resistor R ₁
1MΩ, Capacitor C ₄ is 500μF, and the change range of R ₂ is 2
～1000Omu, When 200Ω~200MΩ range of change in R _4, the insulation resistance R _i is 100000MΩ from 100 M.OMEGA, the electrostatic capacitance C _i 0.001μ
It can be measured in the range of F to 1 μF.

When measuring the dielectric breakdown voltage, the DC voltage may be changed stepwise to measure the insulation resistance, and the voltage at the time when the insulation resistance changes rapidly may be obtained.

EFFECTS OF THE INVENTION Since the insulation deterioration related quantity measuring device according to the present invention uses the low frequency as described above, the insulation deterioration relationship relating to the insulation deterioration even when the DC component current flows in the circuit to be measured. This has the effect that the amount can be measured accurately.

In addition, even in the case of a circuit to be measured that is not energized, the insulation resistance can be measured at a very low frequency with a low frequency applied,
There is an effect that the insulation resistance value can be measured in a state substantially equivalent to the insulation resistance measurement by applying a DC voltage in the AC applied state.

Since different kinds of AC voltages can be simultaneously applied to measure the amount of insulation deterioration, it is possible to cancel out the defect at low frequency and the defect at very low frequency. For example, depending on the circuit characteristics of the measurement target circuit, Has a problem that it takes time to stabilize the ultra low frequency current based on the application of the ultra low frequency voltage,
In the case of applying an extremely low frequency, it is less likely to be affected by the AC impedance component due to the capacitance of the circuit to be measured, etc., and therefore, there is an effect that the insulation deterioration related amount can be measured more accurately than in the case of applying a low frequency.

On the other hand, when applying a low frequency, the magnitude of the capacitance of the measurement target circuit may affect the measurement accuracy, but it is more reliable with respect to the breakdown voltage of the CV cable, etc. It is possible to obtain the insulation deterioration related amount.

[Brief description of drawings]

1 is a sectional view of a CV cable according to the present invention, FIG. 2 is a side view thereof, FIG. 3 is a sectional view of a CV cable according to the present invention, and FIG. 4 is a water tree current generating mechanism according to the present invention. FIG. 5 is a connection diagram of a conventional measuring instrument to a CV cable, FIGS. 6 and 7 are equivalent circuits of the connection diagram shown in FIG. 5, and FIG. 8 is insulation deterioration according to the present invention. FIG. 9 is a block circuit diagram of the relational quantity measuring device, FIG. 9 is a main part configuration diagram of a circuit on the low frequency measurement side, FIG. 10 is an output waveform diagram in the case of measurement at the low frequency, and FIG. 11 is the low frequency measurement. Effective current in the case of
A vector diagram showing the relationship between the reactive current and the reactive current that cancels out, FIG. 12 is an output waveform diagram in the case of measurement at an ultralow frequency, and FIG. 13 is a sheath using the insulation deterioration related quantity measuring device according to the present invention. Simultaneously measuring resistance and DC component current, a relationship curve diagram for explaining an example of estimating and obtaining a water tree current, FIG. 14 is an insulation resistance using the insulation deterioration related amount measuring device according to the present invention. Circuit connection diagram for simultaneously measuring water tree current and sheath resistance, FIG. 15 is a connection diagram for explaining another measurement example using the insulation deterioration related amount measuring device according to the present invention, FIG. 16 FIG. 17 is a connection diagram when the insulation resistance and the capacitance are simultaneously measured using the insulation deterioration related amount measuring device according to the present invention, and FIG. 17 is an equivalent circuit of the circuit connection diagram shown in FIG. 32 …… Low frequency application section 33 …… Low frequency current detection section 34 …… Reactive current generation section 35 …… Differential circuit section 36 …… Insulation resistance calculation section 37 …… Insulation resistance recording section 40 …… DC component current detection Unit 70 …… Ultra low frequency voltage application unit 71 …… DC component current detection unit 72 …… Calculation unit 73 …… Timing control unit

Claims (1)

[Claims] 1. A low-frequency voltage applying section for applying a low-frequency voltage to a measurement target circuit whose insulation deterioration related amount is measured, and a low-frequency current flowing through the measurement target circuit based on the low frequency voltage. A low-frequency current detection unit for detecting, a low-frequency reactive current generation unit for generating a low-frequency reactive current that does not contribute to insulation resistance in synchronization with the low-frequency voltage application unit, and the low-frequency current and the reactive current are input. The low-frequency current is generated by superimposing the low-frequency current and the reactive current to detect a difference, and the low-frequency reactive current generating unit is minimized so that the low-frequency current is minimized in order to extract an effective component current that contributes to insulation resistance. A differential circuit unit that controls and outputs the effective component current to an insulation resistance calculation unit, a recording unit that records insulation resistance based on the output of the insulation resistance calculation unit, and the measurement target circuit that performs the measurement. AC impedance of target circuit And a DC component for detecting a DC component current flowing through the measurement target circuit based on the ultra-low frequency voltage applying unit for applying an ultra-low frequency voltage having an effect that can be ignored. A current detection unit, a calculation unit that calculates an insulation resistance and a DC component current based on the detection output of the DC component current detection unit, and the calculation unit and the super unit for obtaining the DC component current and the insulation resistance. An insulation deterioration related quantity measuring device, comprising: a low frequency voltage application section and a timing control section for timing control of the DC component current detection section.