JPH08285903A - Insulation monitoring system - Google Patents

Abstract

PURPOSE: To monitor the insulation deteriorated state by superimposing the measured voltage having different frequency from that of a power source in a circuit to be monitored, detecting the leakage current effective component of the same phase as that of the measured voltage from its unbalanced current, integrating it to a digital signal, and obtaining the insulation resistance. CONSTITUTION: The measured voltage Va of a single-phase AC is superposed by measured voltage superimposing means 50 connected in series with the ground line 5a of a power transformer 2. The leakage current to become an unbalanced component flowing from an equipment or a wiring to the ground flowing to the circuit to be monitored and the leakage current to become an unbalance component by a voltage Va are detected by unbalanced current detecting means 16. The means 16 detects the superimposed current of the current unbalanced component by the three-phase power source voltage and the leakage current Ig1 corresponding to the voltage Va , and the insulation resistance R1 of the simultaneously three phases indicating insulation deteriorated state is obtained by R1=Va /Ig1. Thus, the leakage current and the insulation resistance of the hot-line state can be monitored real time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation monitoring system for monitoring the insulation deterioration state of an electric circuit fed from a power source without stopping the operation of the electric circuit.

[0002]

2. Description of the Related Art A conventional insulation monitoring system for diagnosing an insulation deterioration state of an electric circuit fed from a power source is shown in FIG.
As shown in FIG. 1, a method of disconnecting an electric circuit from a power source and measuring an insulation resistance to make a diagnosis has been adopted. In FIG. 11, 1 is a high voltage system, 2 is a power transformer, 3 is a low voltage system main circuit, 4 is a main circuit switch that disconnects the low voltage system main circuit 3, and 5 is a low voltage system main circuit 3 that is grounded. It is a grounding resistance and is connected to one wire of the power transformer 2 through a grounding conductor 5a. Reference numeral 10 is a first load circuit connected to the low-voltage system main circuit 3, 11 is a load circuit switch that opens and closes the load circuit 10, 12 is a contactor that controls opening and closing of the load circuit 10, 13 is load circuit wiring, Reference numeral 14 is a load such as an electric motor, and 15 is a ground resistance for grounding the load circuit 10, which is connected to one line of the load circuit via a ground conductor 15a. Reference numeral 16 is an unbalanced current detecting means for detecting an unbalanced current of the load circuit 10, which is, for example, a zero-phase current transformer, and 8 is a circuit protection device for protecting the load 14 such as an electric motor. Two
0 is the second load circuit connected to the low-voltage system main circuit 3,
Reference numeral 30 denotes a third load circuit, which is the first load circuit 10 described above.
Is configured similarly to.

When diagnosing the insulation deterioration of the low voltage system of the electric circuit, it is necessary to distinguish the low voltage system main circuit 3 from the load circuit wiring 13 including the load 14 to measure the insulation resistance. When diagnosing insulation deterioration of the circuit wiring 13, the main circuit switch 4, the load circuit switch 11, and the contactor 12 of the load circuit 10 are opened to disconnect the low voltage system main circuit 3 and the load circuit wiring 13. Then, the insulation resistance tester 91 collectively collects the separated three phases of the load circuit wiring 13.
Insulation deterioration is diagnosed by measuring the insulation resistance with the ground. Similarly, the insulation resistance of the second load circuit 20 and the third load circuit 30 is also measured to diagnose insulation deterioration.
Next, when diagnosing the insulation deterioration of the low-voltage system main circuit 3,
The load circuit switches 11 of the load circuits 10, 20, 30 are opened, and the insulation resistance between the three phases of the low-voltage system main circuit 3 is measured together with the insulation resistance meter 92 to confirm that insulation deterioration has not occurred. Make a diagnosis.

[0004]

Since the conventional insulation monitoring system is to measure the insulation resistance after opening each switch as described above and disconnecting the monitored electric circuit from the system, a great deal of labor and labor is required. It requires experience, and there is also the risk of wiring mistakes after measurement. Further, in a continuously operating plant or the like, the plant cannot be stopped, and since there is no choice but to wait for a periodic inspection every 1 to 2 years, there is a problem that insulation deterioration diagnosis cannot be performed for a long period of time.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to perform insulation deterioration diagnosis in which the insulation resistance is constantly measured and the insulation deterioration state is grasped in real time without stopping the monitored electric circuit. The purpose is to provide an insulation monitoring system that can perform

[0006]

According to a first aspect of the present invention, there is provided an insulation monitoring system in which an electric voltage to be monitored is supplied from a power source through a grounding means through a grounding means to measure a single-phase AC voltage having a frequency different from a power source frequency. Is superimposed, and from the unbalanced current detected by the unbalanced current detection means provided in the monitored electric circuit, the component of the same frequency as the measured voltage by the leakage current detection means,
And the effective component of the leakage current having the same phase as the measured voltage is obtained, and this effective component of the leakage current is integrated and converted into a leakage current digital signal and transmitted to the monitoring control means,
The monitoring control means obtains the insulation resistance based on the leakage current digital signal to monitor and control the insulation deterioration state of the monitored electric circuit.

An insulation monitoring system according to a second aspect of the present invention detects a component having the same frequency as the measurement voltage from the leakage current effective component of the insulation monitoring system according to the first aspect, and synchronizes with a signal synchronized with the measurement voltage. It is detected and detected.

According to a third aspect of the present invention, the insulation monitoring system according to the first or second aspect of the invention has a frequency of the measured voltage that is lower than the power supply frequency.

An insulation monitoring system according to a fourth aspect of the present invention has a frequency of a measured voltage of the insulation monitoring system according to the first or second aspect of the invention, which is higher than the power supply frequency by 150 to 150.
It is an arbitrary frequency between 500 Hz.

An insulation monitoring system according to a fifth aspect of the present invention superimposes a single-phase alternating-current measurement voltage of two kinds of frequencies different from a power supply frequency on a monitored electric circuit fed from a power supply via a grounding means. , A component of the same frequency as each measured voltage is detected from the unbalanced current detected by the unbalanced current detection means provided in the monitored electric circuit, and the unbalanced current of the monitored electric circuit is detected from the unbalanced current corresponding to each measured voltage. The effective component of the leakage current is calculated by the leakage current detecting means, the effective component of the leakage current is integrated, converted into a leakage current digital signal and transmitted to the monitoring control means, and the leakage current digital signal is sent to the monitoring control means. The insulation resistance of the monitored electric circuit is monitored and controlled by obtaining the insulation resistance based on the above.

According to a sixth aspect of the present invention, in the insulation monitoring system according to the fifth aspect, the frequencies of the two types of measurement voltages are set to frequencies lower than the power supply frequency.

An insulation monitoring system according to a seventh aspect of the present invention has a frequency of two types of measurement voltages of the insulation monitoring system according to the fifth aspect, which is 150 to 500 higher than the power supply frequency.
It is an arbitrary frequency between Hz.

In the insulation monitoring system according to the eighth aspect of the present invention, the DC measurement voltage is superimposed on the monitored electric circuit fed from the power source through the grounding means, and the unbalanced current detection provided in the monitored electric circuit. The leakage current detection means removes the power supply frequency component and the high frequency component from the unbalanced current detected by the means to detect the leakage current, converts this to a leakage current digital signal, and transmits this signal to the monitoring control means, The monitoring control means obtains the insulation resistance based on the leakage current digital signal to monitor and control the insulation deterioration state of the monitored electric circuit.

In the insulation monitoring system according to claim 9 of the present invention, the measurement voltage superposing means and the leakage current detecting means of the insulation monitoring system according to claims 1 to 8 are controlled by the monitoring control means. It was done.

An insulation monitoring system according to a tenth aspect of the present invention stores a leakage current value for every fixed time in the monitoring control means of the insulation monitoring system according to any one of the first to ninth aspects. It is equipped with a function of constantly monitoring the change in the leakage current value and issuing an alarm when the preset limit value is exceeded.

According to an eleventh aspect of the present invention, the insulation monitoring system according to any one of the first to tenth aspects uses the leakage current detecting means of the insulation monitoring system for averaging the effective components of the leakage current for a certain period of time. It has a function to do.

According to a twelfth aspect of the present invention, the insulation monitoring system according to any one of the first to eleventh aspects is provided with a function of graphing the effective component of the leakage current in the monitoring control means of the insulation monitoring system. It is a thing.

According to a thirteenth aspect of the present invention, there is provided an insulation monitoring system according to any one of the first to twelfth aspects, wherein the insulation control system monitoring control means has a leakage current effective component and a leakage current reactive component. It is equipped with a function to make a graph.

The operation of each invention will be described below. The insulation monitoring system according to claim 1 superimposes a measurement voltage of a single-phase alternating current having a frequency different from a power supply frequency on a monitored electric circuit fed from a power source, and detects the unbalanced current detected by the unbalanced current detecting means. The component of the same frequency as the measured voltage, and the effective component of the leakage current having the same phase as the measured voltage is detected by the leakage current detection means, and this leakage current effective component is integrated and converted into a leakage current digital signal, This is transmitted to the monitoring control means, and the monitoring control means obtains the insulation resistance based on the leakage current digital signal to monitor and control the insulation deterioration state of the monitored electric circuit, so that the accurate leakage current can be monitored. It is transmitted to the control means, and the insulation deterioration status of the monitored electric circuit can be monitored in real time.

The insulation monitoring system according to a second aspect of the present invention detects a component having the same frequency as the measurement voltage in the insulation monitoring system according to the first aspect, and synchronously detects the component with a signal synchronized with the measurement voltage. The detection accuracy of the active ingredient is increased.

An insulation monitoring system according to a third aspect of the present invention is the insulation monitoring system according to the first or second aspect, wherein the frequency of the measured voltage is set to a frequency lower than the power supply frequency, and thus the monitored electric circuit. The leakage current can be detected in a state in which the influence of the high frequency component generated in is small.

An insulation monitoring system according to a fourth aspect of the present invention is an inverter monitoring system, since the frequency of the measurement voltage is 150 to 500 Hz higher than the power supply frequency in the insulation monitoring system according to the first or second aspect. Accurate leakage current is detected even in the monitored electric circuit,
Insulation deterioration status can be monitored in real time.

In the insulation monitoring system according to the fifth aspect of the present invention, the unbalanced current detection is performed by superposing the measurement voltage of the single-phase AC having two kinds of frequencies different from the power supply frequency on the monitored electric circuit fed from the power supply. Each component of the same frequency as each measured voltage is detected from the unbalanced current detected by the means,
From the unbalanced current corresponding to each measured voltage, the effective component of the leakage current of the monitored electric circuit is calculated by the leakage current detecting means, and this leakage current effective component is integrated and converted into a leakage current digital signal, This is transmitted to the monitoring control means, and the monitoring control means obtains the insulation resistance based on the leakage current digital signal to monitor and control the insulation deterioration status of the monitored electric circuit. It is possible to detect the effective component of the leakage current without performing the synchronous detection by and to obtain the insulation resistance by a simple calculation.

An insulation monitoring system according to a sixth aspect of the present invention is the insulation monitoring system according to the fifth aspect.
Since the frequency of each kind of measurement voltage is set to be lower than the power supply frequency, the influence of the high frequency component generated in the monitored electric circuit is reduced, and more accurate leakage current can be detected.

The insulation monitoring system according to a seventh aspect of the present invention is the same as the insulation monitoring system according to the fifth aspect.
The frequency of the measured voltage of each type is higher than the power frequency.
Since the frequency is set to an arbitrary value between ˜500 Hz, the leak current can be accurately detected even in the inverter-controlled monitored electric circuit.

In the insulation monitoring system according to claim 8 of the present invention, a DC measurement voltage is superimposed on the monitored electric circuit fed from the power source, and the leakage current detecting means supplies the power to the unbalanced current detected by the unbalanced current means. Leakage current is detected by removing the frequency component and high frequency component, this is converted into a leakage current digital signal, this leakage current digital signal is transmitted to the monitoring control means, and the monitoring control means insulates based on the leakage current digital signal. Since the resistance deterioration is sought to monitor and control the insulation deterioration status of the monitored electric circuit,
Accurate leakage current is transmitted to the monitoring control means, and the insulation deterioration status of the load circuit can be monitored in real time.

An insulation monitoring system according to a ninth aspect of the present invention is such that the measurement voltage superposing means and the leakage current detecting means are controlled by the monitoring control means in the insulation monitoring system according to any one of the first to eighth aspects. Since it has been set, it can be operated efficiently as an insulation monitoring system.

An insulation monitoring system according to a tenth aspect of the present invention stores the leakage current value for every fixed period in the monitoring control means of the insulation monitoring system according to any one of the first to ninth aspects. Since the change of the leakage current value is constantly monitored and the alarm is issued when the preset limit value is exceeded, the deterioration status of the load circuit can be monitored in real time.

In the insulation monitoring system according to claim 11 of the present invention, the leakage current detecting means of the insulation monitoring system according to any one of claims 1 to 10 averages the effective components of the leakage current for a certain period of time. Since it has a function to do so, it is possible to monitor the insulation deterioration state with high accuracy by removing the drift of the insulation resistance value.

According to a twelfth aspect of the present invention, the insulation monitoring system according to any one of the first to eleventh aspects is provided with a function of graphing the effective component of the leakage current in the monitoring control means of the insulation monitoring system. Therefore, it is possible to accurately grasp the progress of insulation deterioration.

According to a thirteenth aspect of the present invention, there is provided an insulation monitoring system according to any one of the first to twelfth aspects, in which the effective component of the leakage current and the reactive component of the leakage current are combined with the monitoring control means of the insulation monitoring system. Since it is equipped with a function to graph it, it is possible to grasp the trend of insulation deterioration with high accuracy.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Embodiment 1. FIG. 1 is a configuration diagram showing an embodiment of the present invention. In FIG. 1, 1-5, 5a, 10-1
5, 15a, 16, 20, and 30 are the same as or have the same functions as those of the conventional example shown in FIG. Reference numeral 6 is an unbalanced current detecting means, which is, for example, a zero-phase current transformer, for detecting an unbalanced current provided in the low voltage system main circuit 3 to which the load circuits 10, 20, 30 are connected, and 18 is a first
2 is a circuit protection device for protecting the load circuit 10 of FIG. Reference numeral 50 denotes a measurement voltage superimposing means for superimposing a measurement voltage of a single-phase alternating current having an arbitrary frequency different from the power supply frequency, 5
Reference numeral 1 is a measurement voltage synchronizing signal generating means for generating a signal in synchronization with the measurement voltage shown in detail in FIG.
8 is a circuit protection device 1 connected to the unbalanced current detection means 6
8 is a circuit protection device configured in the same manner.

The measurement voltage superimposing means 50 is connected in series to the ground conductor 5a of the power supply transformer 2, generates a single-phase AC measurement voltage Va of a frequency different from the power supply frequency, and outputs the low-voltage system main circuit 3, The load circuit 10, 20 and 30 are superposed on the monitored electric circuit. Measured voltage synchronization signal generation means 51
Is an unnecessary signal removing means 51a for removing frequency components other than the frequency of the measurement voltage Va superimposed as shown in FIG.
Measurement voltage synchronization signal Igrs having a cycle of the measurement voltage as a signal
And a zero-cross comparator 51b that outputs

The measuring voltage superimposing means 50 has a C in the ground circuit.
There are a method of connecting one winding such as T and PT in series and applying a measurement voltage from the other winding, and a method of flowing a current through a ground resistance through a capacitor to superimpose the measurement voltage.

The circuit protection device 18, as shown in FIG.
Unwanted signal removing means 18a for removing the frequency component other than the frequency of the measurement voltage Va from the unbalanced current Ig1 including the current by the measurement voltage Va detected by the unbalanced current detection means 16 and detecting the current Igla corresponding to the measurement voltage Va. And the measured voltage synchronization signal Igrs from the measured voltage synchronization signal generation means 51 received through the synchronization signal transmission line 61, Igl.
a is detected synchronously and the effective component Ig of the leakage current Igla is detected.
The synchronous detection means 18b for detecting r1, the integrating means 18c for integrating the leakage current effective component Igr1 and converting it into a DC signal proportional to the leakage current effective component Igr1, and the DC signal proportional to the leakage current effective component Igr1. While converting into a digital signal, this is compared with a preset alarm limit value and trip limit value, and when the alarm limit value is exceeded, an alarm signal is output by the alarm display means 18f, and when the trip limit value is exceeded, tripping is performed. It is composed of a computing means 18d for outputting a signal to the input / output means 18g and a transmission slave station 18e for outputting a leakage current digital signal to the monitoring control means 52 via the current signal transmission line 60.

The alarm display means 18f includes a fluorescent display tube, E
L, CRT, etc. that display by light emission, buzzer,
Some speakers make sounds.

The monitoring control means 52 is provided in an electric room or the like located away from the monitored electric circuit, and the leakage current digital signal from the circuit protection device 18 is transmitted through the transmission line 6.
It is composed of a transmission master station 52a for receiving through 0, and a monitoring control device 52b having a function of storing and displaying a leakage current digital signal and a function of outputting insulation deterioration characteristics.

Next, the operation will be described with reference to FIG. The measurement voltage superimposing means 50 connected in series to the ground wire 5a of the power transformer 2 superimposes the measurement voltage Va of the single-phase alternating current, and the monitored electric circuit measures the three-phase power supply voltage on each of the three-phase lines. A voltage on which the voltage Va is superimposed is applied. In the monitored electric circuit, a current due to the three-phase voltage from the power source and a current due to the measurement voltage Va are superimposed and flow. The superimposed current includes a load current in which three phases are balanced by a three-phase voltage, a leakage current that is an unbalanced component that flows from the equipment and wiring connected to the monitored electric circuit to the ground, and an unbalanced component due to the measurement voltage Va. However, the unbalanced component is detected by the unbalanced current detecting means 16. Since the three-phase balanced current is not detected by the unbalanced current detecting means 16, the unbalanced component of the current due to the three-phase power supply voltage and the measured voltage V of the single phase.
The leakage current corresponding to a is detected as a superimposed current. The insulation resistance Rg1 of the three-phase batch indicating the insulation deterioration state of the monitored electric circuit is the leakage current Ig1 due to the measurement voltage Va.
And Rg1 = Va / Ig1.

Measurement is performed by removing unnecessary current removing means 18a from the unbalanced current detected by the unbalanced current detecting means 16 to remove the current of the component having the same frequency as the power supply voltage and the noise noise current generated in the monitored electric circuit. A leakage current Igla corresponding to the voltage Va is obtained. This leakage current Ig
Needless to say, la is the sum of the charging current Igcl flowing through the ground capacitance of the first load circuit 10 and the leakage current effective component Igrl flowing through the insulation resistance Rgl, and this leakage current Igla is measured. By performing synchronous detection in accordance with the phase of the voltage Va, the leakage current effective component Igr
1 is required. In this synchronous detection, a highly accurate leak current effective component is obtained by synchronously detecting the measurement voltage Va by the zero-cross comparator 51b (see FIG. 3) and converting the measurement voltage synchronization signal Igrs into a square wave.

The leak current effective component Igr1 is integrated by the integrating means 18
It is integrated by c and A / D converted by the calculating means 18d to be converted into a digital signal proportional to the leakage current effective component Igr1, and this signal is transmitted from the transmission slave station 18e to the monitoring control means 52 via the transmission line 60. At the same time, the value is compared with a preset value, and if this value is exceeded, the alarm display means 18f displays an alarm. When the digital signal proportional to the effective leakage current component Igr1 exceeds a set value at which the load 14 cannot be operated, the contactor 12 is opened via the input / output means 18g.

The monitoring control means 52 is configured to detect the leakage current effective component I
Insulation resistance is obtained from a digital signal proportional to gr1 and is stored and displayed each time measurement is performed, so that the insulation deterioration status can be monitored in real time. Also,
It is also possible to output the insulation deterioration characteristic from the stored data.
Although the above description has described the diagnosis of the first load circuit 10, it will be apparent according to the above description that the second load circuit 20 and the third load circuit 30 can be similarly diagnosed. Further, when diagnosing the entire circuit including the low-voltage system main circuit 3 in a lump, the circuit protection device 58 having the same configuration as the circuit protection device 18 can be used in the same manner.

In the insulation monitoring system configured as described above, the leakage current of the monitored electric circuit is converted into a digital signal and continuously input to the monitoring control means 52, and the monitoring control means 52 is connected to the monitored electrical equipment on site. Since it is installed in the electrical room away from the circuit, it is possible to monitor the insulation resistance of the load circuit in real time in a concentrated manner in a wide range of monitored electrical circuits. Can be output to easily estimate the subsequent characteristics. Further, since the leakage current is converted into a digital signal and transmitted, there is an advantage that there is no influence of attenuation due to the transmission and accurate monitoring is possible. By the way, in the above configuration, the measurement voltage synchronization signal generating means 51 is provided separately from the circuit protection device 18 for the sake of convenience of description, but the measurement voltage synchronization signal generation means 51 may be incorporated in the circuit protection device 18 in the same manner. It can be operated.

Further, in the above configuration, the frequency of the measurement voltage is set to an arbitrary frequency different from the frequency of the power supply voltage. However, in general, a lot of noise voltage having a frequency higher than the power supply frequency is generated in the load circuit. If the frequency of the measurement voltage is set higher than the frequency of the power supply voltage, it becomes difficult to completely remove the noise voltage. Therefore, by selecting the frequency of the measurement voltage to be lower than the frequency of the power supply voltage, the noise voltage can be easily removed and the detection accuracy of the insulation resistance becomes higher.

As described above, it is desirable that the frequency of the measured voltage is lower than the power supply frequency. When a zero-phase current transformer is used as the unbalanced current detecting means 6 and 16, the sensitivity of the zero-phase current transformer is high. A frequency of about 10 to 30 Hz is practical, considering that the frequency does not decrease, and if CT is used for the measurement voltage superimposing means 50, CT must be increased as the frequency is lower. It is not limited to this

In the above configuration, the load side winding of the power transformer is described as grounding one of the triangular connection wires. However, when the load side winding is star connection, the ground wire connected to the neutral point is measured. The same operation can be performed by adding a voltage superimposing means. Further, in the above description, the case where the monitored electric circuit is the ground system has been exemplified, but even in the non-ground system, the same diagnosis can be performed by superimposing the measured voltage by the GTP (voltage transformer with a gap) or the like. it can.

Embodiment 2. In the first embodiment, the frequency of the measured voltage Va is set to an arbitrary frequency different from the frequency of the power supply voltage, and preferably set to be lower than the frequency of the power supply voltage to increase the detection accuracy of the leakage current. However, when the load circuit includes an electric motor whose frequency is controlled by an inverter, the frequency control range is often lower than the power supply frequency because the frequency control is performed by the inverter, and the frequency control range is often around 100 Hz at the highest. In such a case, if the frequency of the measured voltage is selected to be lower than the power supply frequency, it may be the same as the frequency of the noise voltage of the load circuit, making it difficult to detect only the frequency of the measured voltage. The frequency needs to be higher than the power supply frequency.

On the other hand, since the inverter has a carrier frequency and its frequency components are the fundamental wave of about 600 Hz to 10 kHz and its harmonic components, the upper limit of the frequency of the measured voltage must be 600 Hz or less. Further, considering the detection sensitivity of the zero-phase current transformer which is the unbalanced current detection means, 500 Hz or higher is not preferable. Therefore, in the monitored electric circuit including the load whose frequency is controlled by the inverter, the frequency of the measured voltage is preferably set to an arbitrary frequency within the range of 150 to 500 Hz, and particularly preferably around 200 Hz. If this frequency is selected, the leakage current detection accuracy can be secured even in an inverter-controlled load circuit. The circuit configuration may be the same as that of the first embodiment shown in FIG.

Embodiment 3. In the first and second embodiments, the configuration is such that the measurement voltage Va is always superimposed, but the leakage current does not have to be always measured, and it is sufficient to measure it at regular intervals. Measured voltage V
Only when measuring the leakage current of a, the measured voltage superimposing means 50 and the leakage current detecting means 18a, 1 in the circuit protection device 18
8b is operated, and its block diagram is shown in FIG. In FIG. 5, reference numeral 53 is a monitoring control means, which is a monitoring control apparatus 52b of FIG. 1 having a function of outputting operation command signals to the measured voltage superposition means 50 and the leakage current detection means 18a and 18b in the circuit protection device 18. Control device 5
3b and a transmission master station 53a for transmitting and receiving the operation command signal and the leak current effective component signal. 5
Reference numeral 4 denotes a transmission slave station that receives an operation command signal for the measurement voltage superimposing means 50 and transmits a measurement voltage synchronization signal Igrs, 62.
Is a signal transmission line for transmitting the operation command signal and the leakage current effective component signal.

In this embodiment, since the operation command, the measurement command, and the leakage current effective component signal are transmitted by the transmission line 62, a time difference may occur due to the difference from the signal transmission position to the reception position. This can be dealt with by adjusting the operating time on the sending side or the receiving side. With this configuration, as an insulation monitoring system,
Since the leakage current is measured at regular intervals according to the operation command from the monitoring control means 53, the system can be operated efficiently.

Fourth Embodiment In the above-described first and second embodiments, the frequency of the measured voltage Va is one kind of arbitrary frequency, but in the fourth embodiment, two kinds of frequencies f ₁ and f ₂ are selected, Each measured voltage Va
Has the same value, the unbalanced currents corresponding to the respective measured voltages Va are detected, and the effective leakage current component Igr1 is calculated from these two unbalanced current values.

FIG. 6 shows two arbitrary frequencies f ₁ and f _2.
FIG. 9 is a configuration diagram of a fourth embodiment in which the effective leakage current component Igr1 is detected by selecting (1). 1-5, 5a, 6, 10-1
5, 15a, 20, 30, and 50 are the same as those of the first embodiment shown in FIG. 19, 59 are the leakage current effective components I due to the measured voltages Va of two types of frequencies f ₁ and f _2.
It is a circuit protection device provided with a leakage current detection means for calculating gr1 by calculation. Reference numeral 53 is a monitoring control means, which has a function of storing and displaying the leakage current digital signal with the transmission master station 53a and a function of outputting the insulation deterioration characteristic, and leaks in the measurement voltage superimposing means 50 and the circuit protection devices 19 and 59. The monitor control device 53b also has a function of outputting an operation command signal to the current detection means. Reference numeral 54 is a transmission slave station that receives an operation command signal from the monitor control means 53 via the signal transmission line 62.

Next, the operation will be described. The insulation resistance of the monitored electric circuit is R, the ground capacitance is C, and the measurement voltage is V _a
When the current Ig ₁₀ when the frequency f _1, the frequency f ₂
At that time, the current Ig ₂₀ becomes as shown in (Equation 1) and (Equation 2). Ig ₁₀ = V _a / R + j2 πf ₁ CV _a ‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (Equation 1) Ig ₂₀ = V _a / R + j2 πf ₂ CV _a ‥‥‥‥‥‥‥‥‥‥ ‥‥‥‥‥‥‥‥‥‥ (Equation 2) V _a / R = Igrl and does not relate to the frequency. 2 πf ₁ CV _a = I
When gc ₁ and 2πf ₂ CV _a = Igc ₂ , the absolute values of (Equation 1) and (Equation 2) are expressed by the following (Equation 3) and (Equation 4). (Ig ₁₀ ) ² = (Igrl) ² + (Igc ₁ ) ² ‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (Equation 3) (Ig ₂₀ ) ² = (Igrl) ² + (Igc ₂ ) ² ‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (Equation 4) From (Equation 3) (Equation 4), the relationship of (Equation 5) is obtained. (Igrl) ² = (Ig ₁₀ ) ^2- (Igc ₁ ) ² (Igrl) ² = (Ig ₂₀ ) ^2- (Igc ₂ ) ² (Ig ₁₀ ) ^2- (Igc ₁ ) ² = (Ig ₂₀ ) ^2- (Igc ₂ ) ² ‥‥‥‥‥‥‥‥‥‥‥ (Equation 5) When the measured voltages Va at the frequencies f ₁ and f ₂ are the same, the relationship between the current flowing through the electrostatic capacitance C to the ground of the monitored electric circuit is as follows. (Formula 6) Igc ₁ = Igc ₂ · f ₁ / f ₂ ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ (Equation 6) Substituting the relationship of (Equation 6) into (Equation 5) and rearranging ( Equation 7) is obtained. (Ig ₂₀ ) ^2- (Ig ₁₀ ) ² = (Igc ₂ ) ² {1- (f ₁ / f ₂ ) ² } (Igc ₂ ) ² = {(Ig ₂₀ ) ^2- (Ig ₁₀ ) ² } / { 1- (f ₁ / f ₂ ) ² } (Equation 7) Substituting (Equation 7) into (Equation 4) and rearranging yields (Equation 8). (Igrl) ² = {(Ig10) ^2- (Ig ₂₀ ) ² (f ₁ / f ₂ ) ² } / {1- (f ₁ / f ₂ ) ² } Igrl = [{(Ig10) ^2- (Ig ₂₀ ) ² (f ₁ / f ₂ ) ² } / {1- (f ₁ / f ₂ ) ² }] ^0.5 (Equation 8) The leakage current effective component Igr can be obtained from the relationship of (Equation 8).

According to the present embodiment, in which the leak current effective component Igrl is detected by the two types of measurement voltages having different frequencies, the measurement voltage synchronizing signal generating means is different from the circuit configuration of the first embodiment. 51, unnecessary signal removing means 18a
Further, the synchronous detection means 18b is not required, and the circuit configuration becomes simple.

Also in this configuration, similarly to the third embodiment, the measurement voltage superposing means 50 and the circuit protection devices 19, 59 are provided.
If the leakage current detecting means therein is configured to operate only when measuring the leakage current, the insulation monitoring system can be efficiently operated.

Embodiment 5. In FIG. 7, the DC measurement voltage is superimposed. In FIG. 7, 1-4, 10-1
Reference numerals 5, 15a, 20, and 30 are the same as those in the first embodiment, and a description thereof will be omitted. Reference numeral 70 denotes a measurement voltage superimposing means for superimposing the DC measurement voltage Vd, and as shown in FIG.
DC voltage Vd across the resistor 70a connected in series with the
Is added and a DC current is caused to flow to superimpose a DC voltage. Reference numeral 71 denotes a current detection means provided in the load circuit 10, which detects a current in which alternating current and direct current are superimposed,
Specifically, it is composed of DCCT, Hall CT and the like.
Reference numeral 72 denotes a monitor control means, which is composed of a transmission master station 72a and a monitor control device 72b. Reference numeral 73 is a transmission slave station that receives an operation command signal for the measurement voltage superimposing means 70 sent from the monitoring control means 72. Reference numeral 78 denotes a circuit protection device shown in detail in FIG. 9, which includes an unnecessary signal removing means 78a for removing an unnecessary signal from the current detected by the current detecting means 71 to detect a leakage current, and the leakage current converted into a digital signal. , Compares the preset alarm limit value and trip limit value, outputs an alarm signal to the alarm display means 78f when the alarm limit value is exceeded, and outputs a trip control signal to the input / output means 78g when the trip limit value is exceeded. It is composed of a computing means 78d for outputting and a transmission slave station 78e for outputting the leakage current digital signal to the monitoring control means 72. Reference numeral 76 is a current detection means provided in the low voltage system main circuit 3, which has the same configuration as the current detection means 71, and 79 is a circuit protection device provided in the low voltage system main circuit 3. It has the same configuration as the protection device 78.

Although FIG. 7 shows the case where the current detection means 71 and the circuit protection device 78 are provided in the load circuit 10, the insulation deterioration of each load circuit is also provided by providing the other load circuits 20 and 30. Needless to say, it is possible to collectively monitor the situation, and if the current detection means 76 and the circuit protection device 79 provided in the low-voltage system main circuit 3 are used, the entire circuit including each load circuit can be collectively monitored. can do.

If the measured voltage is set to direct current as in this embodiment, it has nothing to do with the capacitance of the monitored electric circuit,
Since the current due to the measured voltage is only the leakage current, there is an advantage that the current detecting means can be simplified.

Sixth Embodiment In each of the above-described embodiments, the leakage current is measured and calculated in real time to perform insulation monitoring. Generally, the insulation resistance value of the electric circuit gradually decreases in the long term, but in the short term. If you look at it, it has drift characteristics. Therefore, by adding an averaging processing function to the leakage current detecting means and averaging the leakage current data over a fixed time, the detection accuracy can be further improved. The averaging time depends on the configuration of the monitored electrical circuit,
Any value may be set in consideration of conditions such as the environment and the type of load.

Embodiment 7. Further, in each of the above-described embodiments, by adding a graphing processing function to the monitoring control means 52, 53, 72 and graphing the leakage current which is the insulation monitoring data transmitted from the leakage current detection means at any time, It is possible to accurately grasp the progress of insulation deterioration. Furthermore, the cause of the insulation deterioration can be specified by providing a signal processing function of displaying the graph by changing the time axis of the graph.
As the method, the cause of deterioration may be, for example, water intrusion, natural deterioration, sudden accident, etc., but which deterioration pattern corresponds based on the respective deterioration curves of these deterioration causes stored in advance. Can be analogized. Further, regarding the specification of the deteriorated portion, if the deterioration pattern of the specified portion is stored in advance, the specified portion can be inferred.
Further, by printing out those results, it is not necessary to diagnose which part again when updating the parts due to insulation deterioration, and the labor can be reduced.

Embodiment 8. Furthermore, in each of the above-mentioned embodiments, the insulation deterioration status is diagnosed by the effective component of the leakage current, but the reactive component of the leakage current is derived, and this data is further graphed together with the effective component of the leakage current. Highly accurate trend of insulation deterioration can be grasped, analogy of the cause of deterioration, and special cases of deteriorated parts can be performed.

Ninth Embodiment In each of the above-described embodiments, a temperature sensor 80, a humidity sensor 81, and a barometric sensor for detecting an environmental condition provided outside as shown in FIG. 10 based on the calculated zero-phase current effective component Igr data. Correction is performed based on the output of 82.

With such a configuration, in the present embodiment, each sensor takes in and corrects such environmental conditions in consideration of the insulation resistance that changes depending on the environmental conditions such as temperature, humidity or atmospheric pressure. Therefore, the detection accuracy can be further improved. The output of each sensor may be input to the circuit protection device for correction.

Embodiment 10. In the fourth embodiment, any two kinds of frequencies are selected. However, if the low-voltage system main circuit contains a large amount of various harmonic components, it may cause an error. In the present embodiment, the circuit protection device 18 performs FFT operation on the system current in advance to detect a frequency band with a small noise component and use that frequency as the superposition frequency to enable highly accurate zero-phase current effective. The component Igr can be calculated. of course,
Even if the circuit protection device 18 does not have the FFT calculation function, the superposition frequency may be determined based on the value first measured by a person using an FFT analyzer or the like.

[0064]

The insulation monitoring system according to claim 1 of the present invention superimposes a single-phase alternating-current measurement voltage of a frequency different from the power supply frequency on the monitored electric circuit fed from the power supply, and the unbalanced current detecting means. The leak current effective component which has the same frequency component as the measurement voltage and the same phase as the measurement voltage is detected from the unbalanced current detected by, and the leak current effective component is integrated and converted into the leak current digital signal. Since the monitoring control means obtains the insulation resistance based on the digital signal to monitor and control the insulation deterioration status of the monitored electric circuit, the leakage current or the insulation resistance of the monitored electric circuit in the live line state is It can be monitored in real time, and the time of inspection and renewal can be easily predicted from the insulation deterioration status.

The insulation monitoring system according to claim 2 of the present invention detects the effective component of the leakage current in the insulation monitoring system according to claim 1 or 2 as a component having the same frequency as the measured voltage, and measures this as the measured voltage. Since the synchronous detection is performed by the signal synchronized with the detection, the leakage current detection accuracy is improved.

In the insulation monitoring system according to claim 3 of the present invention, the frequency of the measured voltage in the insulation monitoring system according to claim 1 or 2 is set to a frequency lower than the power supply frequency. The leak current is detected in a state where the influence of the harmonic component is small, and the leak current with high detection accuracy is obtained.

In the insulation monitoring system according to claim 4 of the present invention, the frequency of the measurement voltage in the insulation monitoring system according to claim 1 or 2 is set to 150 to higher than the power supply frequency.
Since an arbitrary frequency between 500 Hz is used, accurate leakage current or insulation resistance can be monitored in real time even when an inverter-controlled electric motor, which has many low-frequency components of noise voltage, is used as a load, and insulation deterioration can be prevented. inspection,
Renewal time can be easily predicted.

In the insulation monitoring system according to the fifth aspect of the present invention, the unbalanced current detection is performed by superimposing the measurement voltage of the single-phase AC of two kinds of frequencies different from the power supply frequency on the monitored electric circuit fed from the power supply. The component of the same frequency as each measured voltage is detected from the unbalanced current detected by the means, and the leakage current effective component of the monitored electric circuit is calculated from each unbalanced current corresponding to each measured voltage. It is integrated and converted into a leakage current digital signal, and based on this leakage current digital signal, the monitoring control means obtains the insulation resistance to monitor and control the insulation deterioration state of the monitored electric circuit. An insulation monitoring system that can easily detect effective components can be obtained, and an accurate leakage current or insulation resistance can be monitored in real time. It can be.

In the insulation monitoring system according to claim 6 of the present invention, the frequencies of the two types of measurement voltages in the insulation monitoring system according to claim 5 are set to frequencies lower than the power supply frequency. The leak current is detected in a state where the influence of the generated harmonic component is small, and the leak current with high detection accuracy is obtained.

According to a seventh aspect of the present invention, an insulation monitoring system according to the fifth aspect is configured so that the frequencies of the two types of measurement voltages in the insulation monitoring system are higher than the power supply frequency by 150.
Since the frequency is set to a different arbitrary value between .about.500 Hz, the accurate leakage current can be detected even when the inverter-controlled load is included.

The insulation monitoring system according to claim 8 of the present invention superimposes a direct current measurement voltage on a monitored electric circuit fed from a power source, and calculates the power frequency component from the unbalanced current detected by the unbalanced current detecting means. And the high-frequency component is removed to detect the leak current of the monitored electric circuit, the leak current is converted into a digital signal of the leak current, and the monitoring control means obtains the insulation resistance based on the leak current digital signal, and the monitored electric circuit Since the insulation deterioration situation is monitored and controlled, the accurate leakage current or insulation resistance can be monitored in real time, and the inspection and update timing can be easily predicted from the insulation deterioration situation.

According to the ninth aspect of the insulation monitoring system of the present invention, in the insulation monitoring system according to the first to eighth aspects, the measurement voltage superposing means and the leakage current detecting means are controlled by the monitoring control means. , It can be operated efficiently as an insulation monitoring system that can measure leakage current at regular intervals.

An insulation monitoring system according to a tenth aspect of the present invention stores the leakage current value for each fixed period in the monitoring control means of the insulation monitoring system according to any one of the first to ninth aspects. Since it is equipped with a function that constantly monitors changes in the leakage current value and issues an alarm when a preset limit value is exceeded, it is possible to output the insulation deterioration status on a regular basis, and it is easy to check and update the insulation deterioration status from this status. Can be predicted.

In the insulation monitoring system according to claim 11 of the present invention, the leakage current detecting means of the insulation monitoring system according to any one of claims 1 to 10 averages the effective components of the leakage current for a certain period of time. Since it has a function to do so, it is possible to avoid the influence of a short-term drift of the insulation resistance value, and it is possible to monitor the insulation deterioration state with high accuracy.

According to a twelfth aspect of the insulation monitoring system of the present invention, the monitoring control means of the insulation monitoring system according to any one of the first to eleventh aspects is provided with a function of graphing the effective component of the leakage current. Therefore, the progress of insulation deterioration from the past can be accurately grasped.

An insulation monitoring system according to a thirteenth aspect of the present invention includes a monitoring control means of the insulation monitoring system according to any one of the first to twelfth aspects, in which a leakage current effective component and a leakage current reactive component are combined. Since it is equipped with a function for graphing, it is possible to grasp the trend of insulation deterioration with higher accuracy including the ground capacitance.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a first embodiment of an insulation monitoring system according to the present invention.

FIG. 2 is a block diagram showing an internal configuration of the circuit protection device shown in FIG.

FIG. 3 is a block diagram showing a configuration of a measurement voltage superposing means shown in FIG.

FIG. 4 is an explanatory diagram for explaining the operation of the insulation monitoring system shown in FIG. 1.

FIG. 5 is a configuration diagram showing a configuration of a third embodiment of the insulation monitoring system according to the present invention.

FIG. 6 is a configuration diagram showing a configuration of a fourth embodiment of the insulation monitoring system according to the present invention.

FIG. 7 is a configuration diagram showing a configuration of a fifth embodiment of the insulation monitoring system according to the present invention.

8 is a configuration diagram showing a configuration of a measurement voltage superimposing means shown in FIG.

9 is a configuration diagram showing a configuration of a circuit protection device used in FIG. 7. FIG.

FIG. 10 is a block diagram showing an internal configuration of a circuit protection device shown in a ninth embodiment.

FIG. 11 is a configuration diagram showing a configuration of a conventional insulation monitoring system.

[Explanation of symbols]

2 power transformer 6 unbalanced current detection means 11 load circuit switch 12 contactor 13 load circuit wiring 14 load 15 earth resistance 16 unbalanced current detection means 18 circuit protection device 50 measurement voltage superposition means 51 measurement voltage synchronization signal generation means 52 monitoring Control means 52a Transmission master station 52b Monitoring control device 53 Monitoring control means 54 Transmission slave station 60 Current signal transmission line 61 Synchronous signal transmission line 62 Signal transmission line 70 Measured voltage superposing means 71 Current detection means 72 Monitoring control means 76 Current detection means 78 Load circuit protection device 79 Circuit protection device 80 Temperature sensor 81 Humidity sensor 82 Barometric pressure sensor

Claims (13)

[Claims] 1. A monitored electrical circuit fed from a power supply,
A measurement voltage superimposing means for superimposing a measurement voltage of a single-phase alternating current having a frequency different from the power supply frequency via a grounding means, an unbalanced current detecting means for detecting an unbalanced current flowing in the monitored electric circuit, and this unbalanced Leakage current detection means for detecting an effective component of the leakage current having the same frequency as the measurement voltage and having the same phase as the measurement voltage from the unbalanced current detected by the current detection means, and the leakage current effective component An insulation monitoring system comprising an arithmetic means for integrating and converting into a leakage current digital signal, and a monitoring control means for monitoring and controlling the monitored electric circuit based on the leakage current digital signal. 2. The leakage current detecting means comprises means for detecting a component having the same frequency as the measurement voltage, and means for synchronously detecting the output signal of the measurement voltage synchronization signal generating means for outputting a signal in synchronization with the measurement voltage. The insulation monitoring system according to claim 1, wherein: 3. The insulation monitoring system according to claim 1, wherein the frequency of the measurement voltage is lower than the power supply frequency. 4. The insulation monitoring system according to claim 1, wherein the frequency of the measured voltage is any frequency between 150 and 500 Hz higher than the power supply frequency. 5. A monitored electrical circuit fed from a power supply,
Measurement voltage superimposing means for superimposing single-phase alternating-current measurement voltages of two kinds of frequencies different from the power supply frequency via the grounding means,
An unbalanced current detecting means for detecting an unbalanced current flowing in the monitored electric circuit, and a component having the same frequency as each of the measured voltages is detected from the unbalanced current detected by the unbalanced current detecting means. Leakage current detection means for calculating the effective component of the leakage current of the monitored electric circuit from the unbalanced current corresponding to the voltage, and calculation means for integrating the leakage current effective component and converting it into a leakage current digital signal. ,
An insulation monitoring system comprising: monitoring control means for monitoring and controlling the monitored electric circuit based on the leakage current digital signal. 6. The insulation monitoring system according to claim 5, wherein the frequencies of the two types of measurement voltages are lower than the power supply frequency. 7. The insulation monitoring system according to claim 5, wherein the frequencies of the two types of measurement voltages are different frequencies between 150 and 500 Hz, which are higher than the power supply frequency. 8. A monitored electrical circuit fed from a power supply,
A measurement voltage superimposing means for superimposing a DC measurement voltage through the grounding means, an unbalanced current detecting means for detecting an unbalanced current flowing in the monitored electric circuit, and an unbalanced current detected by the unbalanced current detecting means. Based on the leakage current digital signal, a leakage current detection means for detecting the leakage current of the monitored electric circuit by removing the power source frequency component and the high frequency component from the leakage current, a calculation means for converting the leakage current into a leakage current digital signal, An insulation monitoring system comprising a monitoring control means for monitoring and controlling the monitored electric circuit. 9. The insulation monitoring system according to claim 1, wherein the measurement voltage superposing means and the leakage current detecting means are controlled by the monitoring control means. 10. The monitoring control means is provided with a function of storing a leakage current value for each fixed period, constantly monitoring a change in the leakage current value, and issuing an alarm when a preset limit value is exceeded. The insulation monitoring system according to any one of claims 1 to 9, wherein: 11. The insulation monitoring according to claim 1, wherein the leakage current detecting means is provided with an averaging processing function for averaging the effective components of the leakage current over a fixed period of time. system. 12. The insulation monitoring system according to claim 1, wherein the monitoring control means has a graphing function for graphing the effective component of the leakage current. 13. The monitoring control means is provided with a graphing function for graphing together the leakage current active component and the leakage current reactive component, according to any one of claims 1 to 12. Insulation monitoring system.