KR102495562B1 - Measuring device and method of insulation resistance and capacitance of each phase in live wire state in main circuit of 3-phase 4-wire type electrical equipment - Google Patents

Abstract

The present invention relates to a method for measuring the insulation resistance and capacitance of each phase in a live wire state that includes: measuring the zero-phase current and phase voltage for each phase using a probe and one zero-phase current transformer (ZCT) while installed in the main circuit of a 3-phase 4-wire electrical equipment such as a distribution board; and analyzing three harmonic frequency components.

Description

Measuring device and method of insulation resistance and capacitance of each phase in live wire state in main circuit of 3-phase 4- wire type electrical equipment}

The present invention is installed in the main circuit of a 3-phase 4-wire electrical facility such as a distribution board, and measures the zero-phase current and phase voltage for each phase using a probe and one zero-phase current transformer (ZCT), and analyzes three harmonic frequency components. This relates to a device and method capable of calculating insulation resistance and capacitance for each phase in a live wire state.

Recently, a statistical result of a research institute has been announced that more than half of the fires and disasters related to electricity, which are increasing day by day, are caused by electric leakage. This is because insulation resistance is the main cause, and if these causes can be prevented in advance, social and economic losses due to fire can be significantly reduced.

The most frequent troubles in electric equipment for private vehicles are accidents caused by short circuits in low-voltage circuits, which develop into electrical fires, electric shocks, and expansion of the power outage range. do.

The uninterruptible insulation device has the advantage of not only securing the reliability of electricity supply by grasping the tendency of insulation deterioration for electrical facilities such as houses, factories, and buildings, but also significantly reducing expenses due to frequent inspections.

However, measurement of insulation resistance requires a power outage, making it impossible to measure insulation in the entire electrical system, and with the increase in computers and electronic devices, high-level device damage due to power outages may occur.

In addition, there are cases in which power outage is impossible due to computer-based systems and information management, so insulation resistance measurement cannot be performed. In addition, power outages can cause significant losses due to system outages or loss of critical information, adding to the chaos and complexity of the surrounding community.

So, recently, with the development of IT technology, technology is being developed to remotely manage electrical facilities, and in particular, in the case of three-phase facilities that mainly use power these days, uninterrupted inspection / inspection is required.

Therefore, methods for measuring the insulation resistance value of live-line facilities other than power failure have been proposed, and for this purpose, it is required to measure the zero-phase current.

However, since the zero-phase current includes resistive leakage current, which is an effective component, and capacitive leakage current, which is an ineffective component, accurate measurement of resistive leakage current, which is an effective component, is required.

As a method of measuring the resistive leakage current, there is a method of calculating the resistive leakage current by integrating voltage and current for a half cycle or measuring a voltage-leakage current phase difference. However, in the case of a three-phase electrical installation, since the vector sum of the leakage currents of each phase is measured for the measured zero-phase current, it is difficult to know which phase is leaking.

1 and 2 are diagrams showing circuits and graphs for measuring leakage current in single-phase electrical equipment presented in Korean Patent Registration No. 10-1303597 (published on September 26, 2013).

In the graph of FIG. 2 , a graph with a small amplitude may be an instantaneous voltage V, and a graph with a large amplitude may be a zero-phase current Ig. At this time, a phase difference T may occur according to the insulation resistance R_in and the ground capacity C_in of the load and facility. Therefore, the resistive leakage current Igr can be calculated by the following equation.

However, although the above method can be applied to single-phase branch circuits of each phase for general electricity customers who actually use three-phase, four-wire electrical equipment, it is difficult to apply in practice because it is uneconomical.

In addition, if you look at the “Method and Device for Measuring Live Insulation Resistance of 3-Phase 4-Wire Electrical Equipment” presented in Korean Patent No. 10-1986221 (published on September 30, 2019), The alarm message is transmitted according to the set value of the sum of the generated displacement vectors.

More specifically, in the electrical equipment, the power supply voltage is sequentially applied with a time difference for each phase, and the current change and leakage current change for each phase are measured to set the initial value of the resistive leakage current for each phase of the electrical equipment, Voltage, load current, and zero-phase current for each phase of the electrical installation are measured, and load power consumption for each phase is calculated based on the measured values.

In addition, hypothesis leakage power for each phase is calculated based on the measured value, and an earth leakage phase is extracted based on a preset phase selection criterion and the measured value.

Based on the extracted phase of leakage occurrence, the amount of change in leakage current for each phase is integrated using the hypothetical leakage power for each phase calculated above, and through this, in the live wire state of a three-phase, four-wire electrical installation, each phase and each component (active component, By extracting the leakage current as an ineffective component), a method of measuring the live wire insulation resistance of the electrical equipment is proposed.

This has the problem of adjusting the setting value for each device so that the condition of leakage current change with time difference is established. In order to know the magnitude of the current leakage current, the displacement vector measured by time must be integrated, but the integration error due to integration also occurs over time. Since it increases over time, there is a limit to estimating the current leakage current.

In other words, the current insulation value is estimated by integrating the changed value, but there is a disadvantage in that the value gradually becomes inaccurate because the error is also integrated.

3 is a circuit diagram for measuring leakage current in a conventional three-phase, four-wire electrical installation.

In other words, FIG. 3 is for detecting leakage current through a superimposed signal for measuring the insulation state of a conventional 3-phase 4-wire facility presented in Korean Registered Patent No. 10-1172918 (announced on August 31, 2012). presented in "Insulation Monitoring System"

As shown in FIG. 3, when another small transformer tr for sending a superimposed waveform to the secondary side neutral line type 2 ground wire for measurement is installed and a voltage waveform of low frequency f_r is applied, the voltage waveform of the transformer TR A low-frequency voltage is superimposed on the voltages of each phase S, T, R, and N. Therefore, when a leakage occurs in a load or a line, leakage current is generated according to the low-frequency (f_r) voltage, and the resistive leakage current can be calculated by filtering the frequency (f_r) in the zero-phase current meter (ZCT).

However, the above method also requires a separate device for the neutral wire on the secondary side of the transformer, and is difficult to apply to the facility because there is no private transformer in customer facilities using general three-phase electrical facilities. In addition, the above method has a problem in that the ground voltage of the conductor connected along the ground line increases by the overlapping voltage, resulting in an electric shock risk when the conductor is exposed to the human body.

In addition, the conventional neutral wire superposition signal method has a problem in that it is difficult to apply for measurement of leakage current because the neutral point of the secondary side of the transformer of electrical equipment is owned by KEPCO and several households share the neutral point with each other.

In other words, the method of measuring using a low-frequency superimposition signal is to apply a low-frequency signal to the circuit where leakage current is expected, that is, to the ground line of the neutral point of the secondary side of the transformer, through a signal superimposition transformer, and measure the leakage current according to the applied low frequency. , There is a problem in actual application because low-voltage general purpose electric facilities do not have private transformers for each facility, so the point to apply the low-frequency signal is ambiguous, and the place to install the device is cramped.

Patent Document 1: Domestic Patent No. 10-1303597 (Announced on September 26, 2013) Patent Document 2: Domestic Patent Registration No. 10-1986221 (Announced on September 30, 2019) Patent Document 3: Domestic Patent Registration No. 10-0219013 (published on September 01, 1999) Patent Document 4: Domestic Patent Registration No. 10-1172918 (published on August 31, 2012)

Therefore, the technical problem to be achieved by the present invention is to solve the conventional disadvantages, by configuring to calculate the insulation resistance and capacitance for each phase using harmonics flowing into the power supply side in the live state of the three-phase four-wire electrical equipment, The purpose of this study is to present a device and method for calculating insulation resistance and capacitance for each phase configured to reduce errors while being easy to install.

영상전류 연립방정식 솔루션을 통해 각 위상별 절연저항과 정전용량을 산출하는 산출부;를 포함하여 구성된 것을 특징으로 하는 3상4선식 전기설비 주회로에서 각상별 활선상태 절연저항과 정전용량의 측정장치를 제시한다.In order to achieve the above object, the present invention is a measuring device for measuring insulation resistance and capacitance for each phase in the main circuit of a three-phase four-wire electrical installation in a live wire state,
The measuring device is configured inside the distribution panel, and includes a power voltage measuring unit including a probe for acquiring a voltage signal for each phase of power supplied to the main circuit of the electrical equipment; a zero-phase current measuring unit including a zero-phase current transformer that acquires a zero-phase current signal of power supplied to the main circuit of the electrical equipment; A filtering unit comprising a band pass filter for passing and filtering only three arbitrary harmonic signals excluding the three-fold harmonic signal from the voltage signal for each phase obtained from the power supply voltage measurement unit and the zero-phase current signal obtained from the zero-phase current measurement unit, respectively. ; an ADC for digitally converting each of the harmonic signals of the filtered voltage signal for each phase and zero-phase current signal; a memory unit for storing a one-cycle signal for each harmonic of the digitally converted voltage signal for each phase and zero-phase current signal; an FFT conversion processing unit which separates each harmonic signal of the stored voltage signal for each phase and the zero-phase current signal into a real part and an imaginary part; and the following matrix is created through the real part and the imaginary part of each harmonic signal of the voltage signal and zero-phase current signal for each phase calculated above;

Calculation unit for calculating the insulation resistance and capacitance for each phase through the solution of the simultaneous zero-phase current equation presents

연립방정식 솔루션을 통해 각 위상별 절연저항과 정전용량을 산출하는 단계;를 포함하여 구성된 것을 특징으로 하는 3상4선식 전기설비 주회로에서 각상별 활선상태 절연저항과 정전용량의 측정 방법을 제시한다.In addition, in order to achieve the above object, the present invention provides a method for measuring insulation resistance and capacitance for each phase in the main circuit of a three-phase four-wire electrical equipment in a live wire state, (a) the main circuit of the electrical equipment Acquiring a voltage signal for each phase of power supplied to the circuit with a probe; (b) acquiring a zero-phase current signal of power supplied to the main circuit of the electrical equipment with a zero-phase current transformer; (c) filtering the acquired voltage signal and zero-phase current signal for each phase by passing three arbitrary harmonic signals using a band pass filter, respectively; (d) digitally converting each harmonic signal of the filtered phase voltage signal and phase current signal through an ADC; (e) storing one-cycle signals for each harmonic of the digitally converted voltage signal for each phase and zero-phase current signal; (f) separating each harmonic signal of the stored voltage signal for each phase and zero-phase current signal into a real part and an imaginary part through FFT conversion; and (g) preparing a matrix as shown below through the real part and imaginary part of each harmonic signal of the voltage signal and phase current signal for each phase calculated above,

Calculating insulation resistance and capacitance for each phase through a simultaneous equation solution; Suggests a method for measuring live-line insulation resistance and capacitance for each phase in a main circuit of a three-phase, four-wire electric facility comprising the steps of: .

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The present invention is installed in the main circuit of a 3-phase 4-wire facility, such as a distribution panel, and can be used as an IoT device that transmits status information through communication by measuring data on insulation resistance and capacitance in real time.

In addition, it can be used as a measuring device to monitor/measure the insulation state when electrical facility management and maintenance is needed in a live wire state, as uninterruptible inspection/inspection is currently required.

1 and 2 are diagrams showing circuits and graphs for measuring leakage current in conventional single-phase electrical equipment.
3 is a circuit diagram for measuring leakage current in a conventional three-phase, four-wire electrical installation.
Figure 4 is a schematic diagram of a system for measuring live wire state insulation for each phase in a main circuit of a three-phase, four-wire electric facility according to the present invention.
5 is a circuit diagram of a filtering unit comprising a band-pass filter used in the present invention, and FIG. 6 is a diagram showing voltage waveforms and zero-phase current waveforms for each phase of a waveform applied thereto.
7 is a diagram showing voltage waveforms and phase current waveforms for each phase converted through the ADC according to the present invention.
8 is a diagram showing voltage waveforms for each phase separated by harmonics through the FFT conversion processing unit according to the present invention.
9 is a diagram showing a zero-phase current waveform separated for each harmonic through the FFT conversion processing unit according to the present invention.
10 is a diagram showing a matrix created according to the simultaneous zero-phase current equation for calculating insulation resistance and capacitance according to the present invention.

Hereinafter, with reference to the accompanying drawings, the present inventors, an insulation resistance and capacitance measuring device and method in a live wire state for each phase in a main circuit of a three-phase four-wire electric facility will be described in detail.

Figure 4 is a schematic diagram of a system for measuring live wire state insulation for each phase in a main circuit of a three-phase, four-wire electric facility according to the present invention.

Referring to the figure, the present invention relates to a measuring device 10 for measuring insulation resistance and capacitance for each phase in a main circuit of a three-phase, four-wire electrical installation in a live wire state.

The measuring device 10 of the present invention may be configured inside the distribution board, and the measuring device 10 includes a probe for acquiring voltage signals for each phase (R, S, T) of power supplied to the main circuit of the electrical equipment. A power supply voltage measuring unit 100 including a is configured.

The probe is connected to each phase (R, S, T, N) to measure the power supply voltage for each phase.

The measuring device 10 of the present invention includes a zero-phase current measuring unit 200 including a zero-phase current transformer (ZCT) that acquires a zero-phase current signal of power supplied to the main circuit of the electrical equipment.

The leakage current of the power supply for each phase includes a resistance component related to effective leakage power and a capacitance component related to inactive leakage power. , the risk of leakage current is judged.

In the measuring device 10 of the present invention, the voltage signal for each phase obtained from the power supply voltage measurement unit 100 and the zero-phase current signal obtained from the zero-phase current measurement unit 200 are measured for three-fold harmonics (3, 6, 9), respectively. , ..., etc.) while excluding signals, the filtering unit 300 is configured with a band pass filter that passes and filters arbitrary three harmonic signals.

More specifically, the filtering unit 300 is configured to pass only the harmonics included in the voltage signal and zero-phase current signal for each phase.

5 is a circuit diagram of a filtering unit comprising a band-pass filter used in the present invention, and FIG. 6 is a diagram showing voltage waveforms and zero-phase current waveforms for each phase of a waveform applied thereto.

Referring to the drawing, the filtering unit 300 is configured to pass only the harmonics included in the voltage signal and zero-phase current signal for each phase while applying the same band pass filter (BFP). At this time, a three-phase four-wire live wire state When applying a band pass filter (BPF), it is desirable to set the frequency range to 100 ~ 1000HZ, and the frequency is a multiple of 60Hz, in other words, the frequency of a number of harmonics that are not harmonics such as 3, 6, 9, etc. Configure the filter so that it can pass through 3 or more.

However, in the measurement method of the present invention, if three harmonics, such as 5, 7, and 11 harmonics, are selected, insulation resistance and capacitance can be obtained. free

Also, iterative calculations can be performed by combining another three harmonics to improve accuracy.

In the case of triple harmonics, it is essential to exclude triple harmonics among harmonics to be selected, since they are harmonics that cannot be phase-distinguished.

7 is a diagram showing voltage waveforms and phase current waveforms for each phase converted through the ADC according to the present invention.

The measuring device 10 of the present invention includes an ADC 400 that digitally converts each harmonic signal of the filtered voltage signal for each phase and zero-phase current signal.

When an output signal applied with a band pass filter (BPF) is input to an analog to digital converter (ADC) and digitally converted, the waveform can be output to a computer in an interpretable state as shown.

In addition, the measuring device 10 of the present invention includes a memory unit 500 that stores one-cycle signals for each harmonic of the digitally converted voltage signal for each phase and zero-phase current signal.

In other words, the commercial frequency (60Hz) one-cycle signal measured after the signal is stabilized according to the response speed of the band pass filter (BPF) is stored in the memory unit 500.

V1: R-phase voltage sample storage memory

V2: S-phase voltage sample storage memory

V3: T-phase voltage sample storage memory

Ig: Zero phase current sample storage memory

8 is a diagram showing voltage waveforms for each phase separated by harmonics through the FFT conversion processing unit according to the present invention. 9 is a diagram showing a zero-phase current waveform separated for each harmonic through the FFT conversion processing unit according to the present invention.

The measurement device 10 of the present invention includes an FFT conversion processing unit 600 that separates each harmonic signal of the stored voltage signal for each phase and zero-phase current signal into a real part and an imaginary part.

Through FFT (Fast Fourier transform) processing, the voltage waveform for each phase and the 5th, 7th, and 11th harmonics are separated from the zero-phase current waveform, and the real part and imaginary part are calculated as follows.

8 is a waveform shown by dividing the voltage signal for each phase into 5th, 7th, and 11th harmonic components.

9 is a waveform shown by dividing the zero-phase current signal into 5th, 7th, and 11th harmonic components.

10 is a diagram showing a matrix created according to the simultaneous zero-phase current equation for calculating insulation resistance and capacitance according to the present invention.

In the measuring device 10 of the present invention, a matrix is created based on the simultaneous equation through the real part and the imaginary part of each harmonic signal of the voltage signal for each phase and the phase current signal calculated above, and through the simultaneous phase current equation solution. A calculator 700 is configured to calculate insulation resistance and capacitance for each phase.

The simultaneous equation based on the zero-phase current signal described above is as follows.

10 is a diagram in which a matrix based on the simultaneous equations is created, and the simultaneous equations are matrixed and expressed using the sample data described above.

The illustrated "y = Mx" is a matrix to which the simultaneous equations are applied,

For the y matrix value and the M matrix value, the values calculated through the formula stored in the memory unit 500 described above are applied as they are,

The x matrix value is a value related to insulation resistance and capacitance, and can be calculated using a matrix.

In other words, create a matrix according to the simultaneous equations, and calculate the insulation resistance and capacitance for each phase through the simultaneous equation solution.

In the method according to the present invention, the higher the harmonics, the higher the accuracy. Therefore, the larger the value of the harmonics, the larger the weight is given and the weighted average is calculated by repeating the measurement several times, and the user can see the weighted value, the repeated calculated value, and the weighted average value.

If we further explain the matrix transformation to which the simultaneous equations are applied,

Polar coordinates for each frequency are obtained for Ig (leakage current), V (voltage for each phase), and dV/dt, and through this, it is divided into a real part and an imaginary part.

Representing the real part as A and the imaginary part as B, and writing the expression for the frequency f,

A_Ig_f = Phase A_V_f_r * Phase G_r + Phase A_dVdt_f_r * Phase C_r

+ A_V_f_s phase * G_s phase + A_dVdt_f_s phase * C_s phase

+ A_V_f_t phase * G_t phase + A_dVdt_f_t phase * C_t phase

B_Ig_f = Phase B_V_f_r * Phase G_r + Phase B_dVdt_f_r * Phase C_r

+ B_V_f_s phase * G_s phase + B_dVdt_f_s phase * C_s phase

+ B_V_f_t phase * G_t phase + B_dVdt_f_t phase * C_t phase

Three harmonic signals of each phase voltage signal and phase current signal are applied, and two equations are created for one harmonic frequency.

The value to be calculated is a total of 6 values related to 1/insulation resistance and capacitance for each phase, that is, G_r phase, G_s phase, G_t phase, C_r phase, C_s phase, and C_t phase.

Therefore, the simultaneous equations can be solved for the three frequencies, the equations are created for the three frequencies, for example, f1, f2, and f3, and the three frequency waveforms are combined to calculate the following matrix.

[IG] = [M][X]

In the above formula, X is calculated, in such a way as to obtain an inverse matrix,

here,

IG = [A_Ig_f1; A_Ig_f2; A_Ig_f3; B_Ig_f1; B_Ig_f2; B_Ig_f3;]

M = [A_V_f1_r phase, A_dVdt_f1_r phase, A_V_f1_s phase, A_dVdt_f1_s phase, A_V_f1_t phase, A_dVdt_f1_t phase;

A_V_f2_r phase, A_dVdt_f2_r phase, A_V_f2_s phase, A_dVdt_f2_s phase, A_V_f2_t phase, A_dVdt_f2_t phase;

A_V_f3_r phase, A_dVdt_f3_r phase, A_V_f3_s phase, A_dVdt_f3_s phase, A_V_f3_t phase, A_dVdt_f3_t phase;

Phase B_V_f1_r, Phase B_dVdt_f1_r, Phase B_V_f1_s, Phase B_dVdt_f1_s, Phase B_V_f1_t, Phase B_dVdt_f1_t;

B_V_f2_r phase, B_dVdt_f2_r phase, B_V_f2_s phase, B_dVdt_f2_s phase, B_V_f2_t phase, B_dVdt_f2_t phase;

B_V_f3_r phase, B_dVdt_f3_r phase, B_V_f3_s phase, B_dVdt_f3_s phase, B_V_f3_t phase, B_dVdt_f3_t phase;]

X = [G_r phase; C_r phase; G_s prize; C_s phase; G_t phase; C_t phase;]

In this method, it is possible to improve the accuracy by changing the frequency of harmonics and making several attempts.

In summary, in order to calculate a total of 6 variables for insulation resistance and capacitance for each phase (R, S, T) of the main circuit of a 3-phase 4-wire facility, three random harmonics for each phase, such as , 6 equations can be created by dividing the simultaneous equations related to the zero-phase current into the real part and the imaginary part for the three frequencies through the data according to the 5th, 7th, and 11th harmonics and the zero-phase current data for each phase. Insulation resistance and capacitance for each phase can be calculated.

In the above, an embodiment of the present invention has been described with reference to the accompanying drawings.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above are illustrative in all respects and should not be understood as limiting, and all rights will be determined by the constitution of the claims.

100: power supply voltage measurement unit 200: phase current measurement unit
300: filtering unit 400: ADC
500: memory unit 600: FFT conversion processing unit
700: calculation unit (MPU)

Claims (3)

In the measuring device for measuring the insulation resistance and capacitance of each phase in the main circuit of a three-phase four-wire electrical installation in a live wire state,
The measuring device is configured inside the distribution board,
a power supply voltage measuring unit including a probe for obtaining a voltage signal for each phase of power supplied to the main circuit of the electrical equipment;
a zero-phase current measuring unit including a zero-phase current transformer that acquires a zero-phase current signal of power supplied to the main circuit of the electrical equipment;
A filtering unit comprising a band pass filter for passing and filtering only three arbitrary harmonic signals excluding the three-fold harmonic signal from the voltage signal for each phase obtained from the power supply voltage measurement unit and the zero-phase current signal obtained from the zero-phase current measurement unit, respectively. ;
an ADC for digitally converting each of the harmonic signals of the filtered voltage signal for each phase and zero-phase current signal;
a memory unit for storing a one-cycle signal for each harmonic of the digitally converted voltage signal for each phase and zero-phase current signal;
an FFT conversion processing unit which separates each harmonic signal of the stored voltage signal for each phase and the zero-phase current signal into a real part and an imaginary part; and
The following matrix is prepared through the real part and the imaginary part of each harmonic signal of the voltage signal for each phase and the zero phase current signal calculated above,

Calculation unit for calculating the insulation resistance and capacitance for each phase through the solution of the simultaneous zero-phase current equation . In the method of measuring the insulation resistance and capacitance of each phase in the main circuit of a three-phase four-wire electrical installation in a live wire state,
(a) obtaining a voltage signal for each phase of the power supplied to the main circuit of the electrical equipment with a probe;
(b) acquiring a zero-phase current signal of power supplied to the main circuit of the electrical equipment with a zero-phase current transformer;
(c) filtering the acquired voltage signal and zero-phase current signal for each phase by passing three arbitrary harmonic signals using a band pass filter, respectively;
(d) digitally converting each harmonic signal of the filtered phase voltage signal and phase current signal through an ADC;
(e) storing one-cycle signals for each harmonic of the digitally converted voltage signal for each phase and zero-phase current signal;
(f) separating each harmonic signal of the stored voltage signal for each phase and zero-phase current signal into a real part and an imaginary part through FFT conversion; and
(g) The following matrix is prepared through the real part and the imaginary part of each harmonic signal of the voltage signal and phase current signal for each phase calculated above,

Calculating insulation resistance and capacitance for each phase through a simultaneous equation solution; Method for measuring live-line insulation resistance and capacitance for each phase in a main circuit of a three-phase, four-wire electrical installation, characterized in that it comprises a. delete

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