JP4121979B2 - Non-grounded circuit insulation monitoring method and apparatus - Google Patents

Description

  The present invention relates to a monitoring method and a monitoring device for constantly monitoring the insulation state of a non-grounded circuit having a neutral point resistance on a grounding line such as a grounding transformer grounding circuit or a neutral point resistance grounding circuit.

  In the earthing transformer (EVT, GVT) earthing circuit or neutral resistance earthing circuit, the insulation state of the circuit is monitored, and when insulation deterioration occurs, measures are taken in advance to prevent the occurrence of accidents, When a tie-up accident occurs, it is promptly detected and a protective action is performed to prevent the spread of power outages.

  Conventionally, in order to check the insulation state of an electric circuit, a method of measuring the insulation resistance of the electric circuit by a mega ring at a regular inspection is taken. However, when measuring by this mega ring, it is necessary to make a measurement in a state where the power of the electric circuit is turned off and the power is temporarily cut off.

In recent years, there has been a demand for a method for examining the insulation state in a live state without causing a power failure, and various proposals have been made. As an example, the capacitance of the protection range is measured in advance, or the capacitance is calculated from the ground capacitance, the cross-sectional area of the power cable, the length of the cable, etc., and the zero-phase voltage generated at the time of the accident is loaded. There is one in which the current flowing through the side-to-ground capacitance is calculated, and the current at the fault point is obtained from the current flowing through the zero-phase current transformer by adding or subtracting this current (for example, Patent Document 1). .
JP 2000-324680 A.

  In this method, it is difficult to cope with a change in the ground capacitance due to load fluctuation of the electric circuit or interruption of the load electric circuit, and it is necessary to periodically collect and correct data due to aging of the electric circuit.

In addition, a method for diagnosing the insulation state of the electric circuit based on the insulation resistance value that is not affected by the system constant has been proposed. For example, a superposed signal having a low frequency different from the commercial frequency is injected from a GVT (grounding transformer) arranged in a non-grounded high-voltage distribution system, and this superposed signal is detected by a detection CT and a superposed voltage detection device. The CPU processes the information obtained by correcting the ratio error and the phase error of the superimposed current component in accordance with the phase difference of the superimposed voltage detector and the effective value of the superimposed current component in accordance with a program set in advance by the control device. The ground resistance component is separated by vector synthesis, and the data is monitored or output (for example, Patent Document 2).
Japanese Patent Application Laid-Open No. 9-222455.

  In this method, it is necessary to correct the superimposed error detection ratio error and the phase error according to the phase difference of the superimposed voltage detection and the effective value of the superimposed current component according to a preset program. In addition, a superposition signal transmitter, a coupling device for superimposing the signal, and a superposition voltage detection device for extracting the superposition signal are required. Particularly in the case of high piezoelectric paths, these devices are large in shape and expensive due to insulation.

  The method of checking the insulation state with the superimposed signal needs to reduce the superimposed signal as much as possible so as not to adversely affect the load device, and a filter for removing the system frequency signal included in the detection signal is required. It must be strengthened. Therefore, there is a problem that the measurement time becomes relatively long, it is difficult to provide a function as a relay device that requires high-speed operation, and the function is only for insulation monitoring.

  In view of the above points, the present invention monitors the insulation state of the electric circuit in a live line state, but measures or calculates the capacitance of the protection range in advance as in the prior art, or is different from the commercial frequency. Instead of superimposing the frequency signal and detecting it, it is possible to use a normally used zero-phase current transformer and zero-phase transformer, and only by adding phase voltage detection means to this, It is an object of the present invention to provide an insulation state monitoring method and a monitoring apparatus that can detect an insulation resistance, a current that flows during insulation deterioration, and a ground fault current.

  Means for solving the above problems in the present invention is to obtain an insulation deterioration resistance and a current flowing through the insulation deterioration resistance from the zero phase current, the zero phase voltage and the phase voltage of each charging phase, and to insulate the non-grounded circuit. It is intended to monitor the state.

  Usually, transformers for grounding (GVT or EVT) are installed in substations of power supply companies and customers receiving extra high voltage, and in the case of a low-voltage 400 V circuit, EVT is often ungrounded. Therefore, there is a neutral point resistance on the power source side, and the phase difference between the zero-phase voltage caused by insulation deterioration and the ground-to-ground voltage of the phase in which insulation is deteriorated at the time of insulation deterioration, and the phase difference between zero-phase voltage and zero-phase current The present invention has been made by paying attention to the fact that the current flowing through the insulation deterioration resistance can be calculated because the phase always has a phase of 90 degrees or more, and is determined by the zero-phase current detected by the conventional zero-phase current transformer. The current flowing through the fault point and the fault point resistance are detected, and the insulation of the ungrounded electric circuit is thereby monitored. The basic idea of the present invention will be described below with reference to FIG.

  FIG. 1 is an explanatory diagram of insulation deterioration or ground fault detection in a non-grounded electric circuit by a grounding transformer, and FIG. 2 is an explanatory diagram of insulation deterioration or ground fault detection in a neutral resistance ground circuit.

  Since the equivalent circuit of the neutral point resistance grounding circuit is the same as the non-grounding circuit by the grounding transformer, the grounding transformer grounding circuit will be described, and the grounding transformer has GVT or EVT depending on the capacity. However, since they are equivalent in terms of circuit, for the sake of simplification of description, hereinafter, they will be collectively referred to as EVT.

  In FIG. 1, 1 is a power transformer in which the primary side is star-connected and the secondary side is delta-connected, 2 is a monitored circuit, 3 is a zero-phase current transformer as zero-phase current detecting means, and 4 is an EVT (grounding transformer). The EVT includes a primary circuit 41 of a star connection in which a primary circuit is connected to a monitored circuit, a secondary circuit (not shown) of a delta connection, and a tertiary circuit 43 (broken delta circuit). The neutral point of the primary circuit is grounded by the ground line 44, and the tertiary circuit 43 is provided with a limiting resistor Ro (a neutral point resistor converted to primary).

  In the figure, C0 represents the power-side ground capacitance, and CL represents the load-side ground capacitance.

  When the circuit of FIG. 1 is rewritten to an equivalent circuit, it becomes as shown in FIG. 4 shows a vector diagram of each voltage and current when insulation deterioration occurs at point G in FIG. 1. FIG. 4A is a whole, and FIG. 4B is a portion surrounded by a dotted circle in FIG. FIG.

  If the insulation deterioration occurs at point G on the load side of the zero-phase current transformer 3 in FIG. 1, the current Ir0 flowing in the ground line 44 of the EVT 4 is neutral in the tertiary circuit 43 as shown in FIGS. 3 and 4. Since it is a current flowing through the point resistor Ro, it has the same phase as the zero-phase voltage V0, but the zero-phase current transformer has a relationship in which the zero-phase voltage V0 is viewed from the ground voltage E point to the neutral point N of the circuit. When viewed from 3, the phase is opposite, and the phase is 180 ° with respect to the zero-phase voltage V0.

  The current Ic0 that flows through the power supply side ground capacitance C0 is a current corresponding to the capacitance that flows due to the zero-phase voltage V0, and therefore is 90 ° ahead of the zero-phase voltage V0, but is viewed from the zero-phase current transformer 3. Sometimes the phase is reversed and the delay is 90 °. The current IcL flowing through the load-side ground capacitance CL once flows through the zero-phase current transformer 3, but the current IcL flowing back through the load-side ground capacitance CL and returning to the zero-phase current transformer 3 through the capacitance CL. Is offset.

  The current Ig flowing through the insulation deterioration point G is a vector sum of the current Ir0 flowing through the ground line 44, the current Ic0 flowing through the power supply side ground capacitance C0, and the current IcL flowing through the load side ground capacitance CL.

  It becomes.

  Since the ground fault phase voltage Vg (ground fault phase-ground voltage) at the time of insulation deterioration is the product of the insulation deterioration resistance Rg and the current Ig flowing through the Rg, the phase is in phase with the current Ig.

  The phase difference θ between the zero-phase voltage Vo and the ground-fault phase voltage Vg caused by the insulation deterioration is 90 ° when the current Ir0 flowing through the ground line 44 is zero when the neutral point resistance Ro is infinite. When C0 is zero, the current Ic0 flowing through the capacitance C0 is zero and 180 °.

  Therefore, if the neutral point resistance R0 of the EVT 4 is not infinite, 90 ° <θ ≦ 180 °.

  Since the current IcL flowing through the load side ground capacitance CL is canceled out by the zero phase current I0 detected by the zero phase current transformer 3, the zero phase current I0 detected by the zero phase current transformer 3 is As shown in the equation, it is the sum of the current Ir0 flowing in the ground line 44 and the current Ic0 flowing in the power supply side ground capacitance C0.

  4 exists in a phase between the current Ir0 flowing through the ground line 44 and the current Ig flowing through the insulation deterioration resistance Rg, like the zero-phase current I0 in FIG.

  From these relationships, if the neutral point resistance R0 is not infinite but 90 ° << θ, the absolute value and phase of the zero-phase voltage V0, the zero-phase current I0, and the ground fault phase voltage Vg are measured. The current Ir0 flowing through the ground line and the current Ig flowing through the insulation deterioration resistance are obtained as follows by the following calculation.

Ir0 = I0 × Cos (180 ° −φ) (3)
Ig = Ir0 ÷ Cos (180 ° −θ) (4)
Where φ is the phase difference between the zero-phase voltage V0 and the zero-phase current I0, and θ is the phase difference between the zero-phase voltage V0 and the ground fault phase voltage Vg.

  Further, the insulation deterioration resistance Rg is obtained from the ground fault phase voltage Vg and the current Ig flowing through the insulation deterioration resistance by the following equation.

Rg = Vg ÷ Ig (5)
The phase of the ground fault phase is determined by whether each phase voltage at the time of insulation deterioration is within a range of 90 ° to 180 ° with respect to the zero phase voltage V0. Is judged as an insulation deterioration phase.

  The phase voltage can be detected by detecting the voltage of each phase or by calculating the original phase voltage (phase voltage without insulation deterioration) from any one-phase voltage and zero-phase voltage using a calculation means. It may be obtained by calculation, and the original phase voltage of the remaining other phase may be obtained by giving a phase difference of 120 °, and the phase voltage of the other phase at the time of insulation deterioration may be obtained.

  As described above, when the neutral point resistance R0 is not infinite and the phase difference θ between the zero-phase voltage V0 and the ground fault voltage Vg is 90 ° << θ, the zero-phase voltage V0, the zero-phase current By measuring the absolute value and phase of I0 and the ground fault phase voltage Vg, the insulation degradation resistance Rg and the current Ig flowing through the resistance Rg can be obtained, so that the resistance value Rg and / or the current value Ig is displayed on a display or the like. By doing so, the insulation state of the monitored electric circuit can be constantly monitored.

  Further, a ground fault detection protection can be performed by providing a detection threshold value for the current Ig flowing through the insulation deterioration resistance and performing a protection operation such as outputting an alarm and / or a contact when the threshold value is exceeded to shut off the fault circuit.

  The above explanation is a case where a zero-phase current transformer is provided in the monitored circuit. However, if this zero-phase current transformer is provided in the ground line, all the monitored circuits are viewed from the zero-phase current transformer. It becomes the load side and can monitor the insulation deterioration state of the whole electric circuit. In this case, since the current Ir0 flowing through the ground line can be directly measured, the zero-phase current I0 detected by the zero-phase current transformer is equal to the current Ir0 flowing through the ground line. The current Ig flowing in the insulation deterioration resistance Rg from the phase difference θ between the phase of the ground and the ground fault voltage Vg is obtained by setting Ir0 in the above equation (4) to I0, and the insulation deterioration resistance Rg is obtained by the equation (5). be able to.

  In the EVT ground system circuit, the zero-phase current is detected from the EVT ground line, the interphase voltage is detected from the EVT secondary circuit, the zero-phase voltage is detected from the EVT tertiary circuit, and the EVT secondary circuit is detected. Each line voltage is converted into a phase voltage value and each phase voltage is obtained as a phase delayed by 30 °, or any one phase line voltage is converted into a phase voltage and a phase delayed by 30 °, and the other phases In the case of a three-phase three-wire voltage, the phase is shifted by 120 °, so each phase voltage is obtained by calculation. Further, by calculating a vector with zero phase voltage V0, each phase voltage at the time of insulation deterioration is obtained. It is possible to determine which phase is the insulation deterioration phase or the ground fault phase from each value of the phase voltage and the zero phase voltage V0 at the time of deterioration, and obtain the value and phase of the ground fault phase voltage Vg. Since the zero-phase current I0 detected from the ground line is equal to the current Ir0 flowing through the ground line as described above, its absolute value flows from the phase difference θ between the zero-phase voltage V0 and the ground fault voltage Vg to the insulation deterioration resistance. The current Ig can be obtained by setting Ir0 in the above equation (4) to I0.

  As described above, the present invention can determine the insulation deterioration resistance value and the current value flowing through the insulation deterioration resistance by the zero phase voltage, the zero phase current and the ground fault phase voltage which can be measured by the normal detection means. There are effects like this.

  (1) The insulation state of the monitored circuit can be constantly monitored in a live line state without requiring a power failure.

  (2) Zero-phase current detection means and zero-phase voltage detection means may be equivalent to zero-phase current transformers and zero-phase voltage detection devices normally used for directional ground fault relays, etc. Is detected by vector calculation from the zero-phase voltage and the original phase voltage, or only a phase voltage detecting means is added, and no special device is required.

  (3) In the EVT ground circuit, the ground fault phase voltage can be obtained by calculation from the secondary circuit and tertiary circuit of the EVT, so that the phase voltage detecting means can be dispensed with.

  (4) By attaching a plurality of units to each branch, it is possible to identify the location of insulation deterioration.

  (5) By detecting the zero-phase current flowing in the ground line, it is possible to monitor the insulation deterioration of the entire monitored electric circuit.

  (6) Even if the capacitance on the load side fluctuates, accurate insulation monitoring can always be performed without being affected by this.

  Embodiments of the present invention will be described below with reference to the drawings.

  5 and 6 are explanatory diagrams of the first embodiment of the present invention. FIG. 5 is an overall configuration diagram, and FIG. 6 is an internal configuration diagram of insulation monitoring means. In these drawings, the same or corresponding parts as those in FIG.

  Thus, 5 is a zero-phase voltage detection means, 6 is a phase voltage detection means, and both detection means use a capacitor, but other means may be used. Reference numeral 7 denotes an insulation monitoring means. The insulation monitoring means 7 is detected by the zero phase current signal detected by the zero phase current transformer 3, the zero phase voltage signal detected by the zero phase voltage detection means 5 and the phase voltage detection means 6. Input phase voltage signal (voltage between each charging phase and ground).

  The insulation monitoring means 7 has a configuration shown in FIG. 6. An input signal is an A / D converter for removing unnecessary noise by a filter F, amplifying by an amplifier A, and obtaining an absolute value of each signal. The analog-digital conversion is performed at 71 and the result is input to the computing unit 72. Each signal is waveform-shaped by the waveform shaping circuit P in order to determine the phase, and is input to the calculator 72. Reference numeral 73 denotes display means such as a display, 74 denotes a relay, and 75 denotes an alarm means, which are actuated by an output signal of the calculator 72.

  The phase voltage detection means 6 does not necessarily take signals from each of the three phases. The original phase voltage (phase voltage without insulation deterioration) is obtained from any one phase voltage and zero phase voltage. It may be obtained by a vector calculation by an arithmetic unit, and the original phase voltage of the remaining other phase may be obtained by giving a phase difference of 120 °, and the phase voltage of the other phase at the time of insulation deterioration may be obtained.

  The computing unit 72 first determines whether the insulation deterioration is on the power source side or on the load side from the phase of the input zero phase current signal I0 and zero phase voltage signal V0. In this direction determination, for example, a range of 45 ° to 225 ° phase with respect to the zero-phase voltage V0 is determined as a load-side accident or insulation deterioration.

  In addition, the phase voltage phase of the condition that is 90 ° to 180 ° behind the zero phase voltage from the phase voltage phase and the zero phase voltage phase obtained by the phase voltage detection means is the ground fault phase or the insulation deterioration phase. to decide.

If the power supply side of the insulation deterioration or accident does not perform the following processing, if the load side, the absolute value and the absolute phase and zero-phase voltage V0 of the zero-phase current I0 detected by the zero-phase current detecting means From the value and phase, the resistance component current Ir0 flowing to the ground line by the neutral point resistance R0 is obtained by the calculator 72 by the above equation (3).

  Next, the current Ig flowing through the insulation deterioration resistance Rg is obtained. This current Ig is a current obtained by synthesizing the current IcL flowing through the load-side ground capacitance and the zero-phase current I0, and is a current in phase with the ground-fault voltage Vg. Therefore, the zero-phase voltage V0 and the ground-fault voltage Vg When the phase difference is θ, it is obtained by the calculator according to the above equation (4).

  Next, since the value obtained by dividing the ground fault phase voltage Vg at the time of insulation deterioration by the current Ig flowing through the insulation deterioration resistance Rg is the insulation deterioration resistance Rg, Rg = Vg ÷ Ig is obtained.

  These current value Ig and resistance value Rg are displayed on the display means 73 of the insulation monitoring means 7 to monitor the insulation state, or when a detection threshold is set and the threshold is exceeded, the alarm means 75 and / or the relay 74 outputs the contact. Insulation status is monitored.

  Moreover, when functioning as a ground fault direction relay device or a directional leakage relay, an operation threshold is set for the value of the current Ig flowing through the insulation deterioration resistance, and when this threshold is exceeded, an alarm and / or contact is output to protect it. Make it work.

  7 and 8 are explanatory diagrams of the second embodiment of the present invention. FIG. 7 is an overall configuration diagram, FIG. 8 is a configuration diagram of the insulation monitoring means, and the difference from the first embodiment is as follows. The zero-phase current detection means detects the zero-phase current using a zero-phase current transformer provided on the EVT ground line, detects the line voltage from the secondary circuit of the EVT, and detects the zero-phase voltage of the EVT. This is a point performed by a tertiary circuit. Note that the same or corresponding parts as those in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof is omitted.

  The insulation monitoring means 7 receives the zero-phase current of the zero-phase current detection means 3, the zero-phase voltage signals of the EVT tertiary circuit 43, and the line voltage of the secondary circuit 42. Unnecessary noise is removed from each signal by the filter F, and the signal is amplified by the amplifier A. The signal is input to the A / D converter 71 and sent to the calculator 72 in order to obtain the absolute value of each signal. Further, the waveform is shaped by the waveform shaping circuit P and sent to the computing unit 72 for phase discrimination. An arbitrary one-phase line voltage of the secondary circuit 42 of the EVT is also possible.

  Each line voltage value of the EVT secondary circuit 42 is converted into a phase voltage value, and each phase voltage is obtained as a phase delayed by 30 °. Alternatively, it is known that the phase voltage of any one phase is converted into a phase voltage and the phase is delayed by 30 °, and in the case of the three-phase three-wire, the other phase voltages are known to be out of phase by 120 °. Find the voltage. Furthermore, each phase voltage at the time of insulation deterioration is obtained by vector calculation with zero phase voltage V0, and which phase is the insulation deterioration phase or ground fault phase from each value of each phase voltage and zero phase voltage V0 at the time of insulation deterioration Discriminate and obtain the value and phase of the ground fault phase voltage Vg.

  Since the zero-phase current I0 detected by the zero-phase current detection means 3 is equal to the current Ir0 flowing through the ground line, the absolute value is converted from the phase difference θ between the zero-phase voltage V0 and the ground fault phase voltage Vg to the insulation deterioration resistance. The flowing current Ig is obtained by setting Ir0 in the above equation (4) to I0.

  Next, since the value obtained by dividing the ground fault phase voltage Vg at the time of insulation deterioration by the current Ig flowing through the insulation deterioration resistance Rg is the insulation deterioration resistance Rg, it can be obtained by Rg = Vg ÷ Ig.

  In the case of insulation monitoring, the current value Ig and insulation deterioration resistance value Rg at the time of insulation deterioration are displayed on the display means, or when a detection threshold value is set and the threshold value is exceeded, an alarm and / or a contact is output to output the monitored circuit Monitor insulation degradation.

  When the function of the ground fault relay device or the earth leakage relay is provided, an operation threshold value of the current Ig at the time of insulation deterioration is provided, and when the threshold value is exceeded, an alarm and / or a contact is output to perform a predetermined protective operation.

  If the zero-phase current detection means 3 is provided on the ground fault wire 44 as in this embodiment, all the monitored electric circuits are on the load side when viewed from the zero-phase current detection means 3, and the insulation of the entire electric circuit can be monitored and the ground line It is possible to directly measure the current Ir0 flowing through the. Further, in the EVT ungrounded circuit, the ground fault phase voltage is obtained by calculation from the secondary circuit 42 and the tertiary circuit 43 of the EVT, and there is an advantage that the phase voltage detecting means 6 is not required.

  As described above, the present invention has been described in detail only with respect to the specific examples described above, but various methods such as applying a suitable combination of the zero-phase voltage zero-phase current and the phase voltage detection method within the scope of the technical idea of the present invention. It will be apparent to those skilled in the art that variations and modifications can be made, and it is obvious that such variations and modifications fall within the scope of the claims.

Explanatory drawing of the earthing transformer earthing circuit. Explanatory drawing of a neutral point resistance grounding circuit. The equivalent circuit diagram of FIG. Vector diagram of voltage and current during insulation degradation. 1 is an overall configuration diagram of a first embodiment of the present invention. The internal block diagram of the insulation monitoring means of FIG. The whole block diagram of 2nd embodiment of this invention. The internal block diagram of the insulation monitoring means of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power transformer 2 ... Monitored circuit 3 ... Zero phase current transformer 4 ... Grounding transformer 5 ... Zero phase voltage detection means 6 ... Phase voltage detection means 7 ... Insulation monitoring means

Claims (10)

In the insulation monitoring method of the non-grounded circuit that has the power source side neutral point resistance on the ground line, the zero-phase voltage of the circuit, the zero-phase current I0 of the circuit and the phase voltage between each charging phase and the ground are detected and detected. The phase of the zero-phase voltage value and the zero-phase current value are compared, and the fault point is on the power source side or the load side depending on whether the zero-phase current is within the range of 45 ° to 225 ° phase with respect to the zero-phase voltage. If it is within the range, it is determined that there is a load-side accident. If it is on the load side, the current Ir0 that flows through the ground line by vector calculation from the zero-phase voltage value and phase and the zero-phase current value and phase Is obtained from Ir0 = I0 × Cos (180 ° −Φ) (where Φ is the phase difference between the zero-phase voltage and the zero-phase current), and then the detected ground-phase voltage and zero The phase difference θ with respect to the phase voltage is obtained, and the insulation deterioration current Ig flowing through the insulation deterioration resistance Rg is expressed as Ig = Ir0 ÷ Cos ( Calculated by the vector calculation of 80 ° - [theta]), the land絡相voltage during insulation deterioration, divided by the insulation deterioration current value obtained previously to seek insulation deterioration resistance, the insulation deterioration current value and / or insulation deterioration An insulation monitoring method for an ungrounded electric circuit, wherein the insulation state of the electric circuit is monitored by a resistance value. In an insulation monitoring method for a grounding transformer system or a non-grounded circuit having a neutral point resistance in the grounding wire, the phase voltage between each charging phase and the ground flows through the grounding transformer or the grounding wire of the neutral point resistance. The zero-phase current I0 and the zero-phase voltage of the electric circuit are detected, respectively, the phase difference θ is obtained from the detected zero-phase voltage value and the phase of the ground fault phase voltage of each phase voltage, and then flows to the insulation degradation resistance The insulation deterioration current Ig is obtained by calculating Ig = I0 ÷ Cos (180 ° −θ) by vector calculation, the insulation deterioration resistance value is obtained from the insulation deterioration current value and the ground fault phase voltage value, and the insulation deterioration current value and / or An insulation monitoring method for an ungrounded electric circuit, wherein the insulation state of the electric circuit is monitored by an insulation deterioration resistance value. In a method for monitoring insulation of an ungrounded circuit by a grounding transformer having a primary circuit to a tertiary circuit, grounding a neutral point of the primary circuit, and having a limiting resistor in the tertiary circuit, the neutral circuit of the primary circuit is grounded Zero phase current I0 is detected, zero phase voltage is detected from the tertiary circuit, each line voltage value of the secondary circuit is converted into a phase voltage value, and each charge phase and ground are converted from this converted phase voltage and zero phase voltage. Is obtained by vector calculation, and the phase difference θ between the phase of the ground fault phase voltage and the phase of the zero phase voltage of each obtained phase voltage is obtained. Next, the insulation deterioration current Ig flowing through the insulation deterioration resistance is obtained. , Ig = I0 ÷ Cos (180 ° −θ) is obtained by calculation, the insulation deterioration resistance value is obtained from the insulation deterioration current value and the ground fault phase voltage value, and the electric circuit is determined by the insulation deterioration current value and / or the insulation deterioration resistance value. It is characterized by monitoring the insulation state of Insulation monitoring method for ungrounded circuit.   The insulation deterioration phase is determined by whether each phase voltage at the time of insulation deterioration is within the range of 90 ° to 180 ° with respect to the zero phase voltage, and the phase within the range is determined as the insulation deterioration phase. The insulation monitoring method for an ungrounded electric circuit according to any one of claims 1 to 3, wherein:   The insulation monitoring method for an ungrounded circuit according to any one of claims 1 to 4, wherein the insulation deterioration circuit is interrupted when the insulation deterioration current value exceeds a preset value. In an insulation monitoring device for a non-grounded circuit having a power-side neutral point resistance on the ground line, a zero-phase voltage detecting means for detecting a zero-phase voltage of the circuit, and a phase voltage detection for detecting a phase voltage between each charging phase and the ground And a zero phase current detecting means for detecting a zero phase current I0 of the electric circuit and an insulation monitoring means for monitoring the insulation state by inputting each signal detected by each of the detecting means. The phase of the zero-phase voltage and the zero-phase current are compared, and whether the fault point is on the power source side or the load side depending on whether the zero-phase current is within the range of 45 ° to 225 ° phase with respect to the zero-phase voltage When the load is on the load side, a zero-phase voltage value, a phase, a zero-phase current value, and a phase are used to calculate a current Ir0 flowing through the ground line, Ir0. = I0 × Cos (180 ° -Φ ) ( where, [Phi is zero-phase voltage and zero-phase Next, the phase difference θ between the ground fault phase voltage and the zero phase voltage among the detected phase voltages is obtained, and the insulation deterioration current Ig flowing through the insulation deterioration resistance Rg is determined as Ig = It is obtained by vector calculation of Ir0 ÷ Cos (180 ° −θ), and the insulation deterioration resistance value is obtained by dividing the ground fault phase voltage value at the time of insulation deterioration by the previously obtained insulation deterioration current value. And / or an insulation monitoring device for an ungrounded electrical circuit, wherein the insulation state of the electrical circuit is monitored by an insulation deterioration resistance value. In an insulation monitoring device for a non-grounded electric circuit having a neutral point resistance on the ground line, a zero-phase voltage detecting means for detecting a zero-phase voltage of the electric circuit, and a phase voltage detecting means for detecting a phase voltage between each charging phase and the ground A zero phase current detecting means for detecting the zero phase current I0 flowing through the ground line, and an insulation monitoring means for monitoring the insulation state by inputting each signal detected by each of the detecting means, the insulation detecting means, The phase difference θ between the detected zero-phase voltage and the ground fault phase voltage of each phase voltage is obtained. Next, the insulation deterioration current Ig flowing through the insulation deterioration resistance is calculated as follows: Ig = I0 ÷ Cos (180 ° −θ) It is obtained by vector calculation, the insulation deterioration resistance value is obtained from the insulation deterioration current value and the ground fault phase voltage value, and the insulation state of the electric circuit is monitored by the insulation deterioration current value and / or the insulation deterioration resistance value. An insulation monitoring device for ungrounded electrical circuits.   In an insulation monitoring device for a non-grounded electric circuit of a grounding transformer grounding system, phase voltage detecting means for detecting a phase voltage between each charging phase and the ground, and a zero-phase current I0 flowing in the grounding line of the grounding transformer are detected. Insulation monitoring means for monitoring the insulation state by inputting the zero-phase current detection means, and each signal detected by each of these detection means and the zero-phase voltage detected by the tertiary circuit of the grounding transformer is provided. The phase difference θ between the detected zero-phase voltage and the ground fault phase voltage of each phase voltage is obtained, and then the insulation deterioration current Ig flowing through the insulation deterioration resistance is calculated as follows: Ig = I0 ÷ Cos (180 ° −θ) Is obtained by vector calculation, the insulation deterioration resistance value is obtained from the insulation deterioration current value and the ground fault phase voltage value, and the insulation state of the electric circuit is monitored by the insulation deterioration current value and / or the insulation deterioration resistance value. An insulation monitoring device for ungrounded electrical circuits. In an insulation monitoring device for a non-grounded circuit by a grounding transformer having a primary circuit to a tertiary circuit, grounding a neutral point of the primary circuit, and having a limiting resistor in the tertiary circuit, the neutral circuit from the neutral point of the primary circuit A zero-phase current detecting means for detecting the zero-phase current I0; a zero-phase voltage detecting means for detecting the zero-phase voltage from the tertiary circuit; and a means for detecting each line voltage value of the secondary circuit. The insulation monitoring means converts the input line voltage value into a phase voltage value, and from each of the converted phase voltage and zero-phase voltage, the insulation monitoring means monitors the insulation state. The phase voltage between them is obtained by vector calculation, and the phase difference θ between the phase of the ground fault phase voltage and the phase of the zero phase voltage in each of the obtained phase voltages is obtained, and then the insulation degradation current flowing through the insulation degradation resistance Ig is calculated as follows: Ig = I0 ÷ Cos (180 ° −θ) The insulation degradation resistance value is obtained from the insulation degradation current value and the ground fault phase voltage, and the insulation state of the electric circuit is monitored by the insulation degradation current value and / or insulation degradation resistance value. An insulation monitoring device for ungrounded electrical circuits.   The detection of each phase voltage at the time of insulation deterioration is obtained by converting each line voltage value of the secondary circuit into a phase voltage value and obtaining each phase voltage as a phase delayed by 30 ° or by phase conversion of any one-phase line voltage. When converted into voltage, the phase is delayed by 30 °, and other phase voltages are shifted by 120 ° to obtain each phase voltage, and this phase voltage and the zero-phase voltage detected by the tertiary circuit are vector-calculated. The non-grounded circuit insulation monitoring device according to claim 9, wherein each phase voltage is obtained.

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