KR20120002291A - Power quality monitoring system and method thereof - Google Patents

Abstract

PURPOSE: A power quality monitoring system and a monitoring method thereof are provided to improve speed calculation speed for evaluating the harmonic wave of an electric power system by reducing sampling data. CONSTITUTION: A power quality monitoring system(10) comprises a power measuring quality apparatus(100) and a server(200). The power measuring quality apparatus obtains a voltage waveform in a bus line and a distribution line at a preset time interval while being connected to the bus line and the distribution line of the electric power system. The power quality monitoring system samples and stores the voltage waveform and current waveform acquired at a fixed cycle. The power measuring quality apparatus superposes the voltage waveform and current waveform, which is sampled for a fixed measurement cycle, into one cycle and generates and stores a voltage representative waveform and a current representative waveform. A server monitors the abnormal occurrence of the electric power system by receiving the voltage representative waveform and the current representative waveform and decomposing a harmonic component with high speed Fourier transform.

Description

[0001] POWER QUALITY MONITORING SYSTEM AND METHOD [0002]

To a power quality monitoring system and method therefor of the present invention.

As the industrial equipment becomes larger, there is a case where a large amount of harmonics or flickers are generated. Therefore, in the case of a consumer using an electric device having a sensitive characteristic due to a momentary drop in voltage, There are frequent phenomena related to electric quality such as stopping of operation.

Currently, in Korea, electrical quality standards are established and amended based on the standards of the International Electrotechnical Commission (IEC). According to the IEC standard, measurements for electrical quality assessment should be made at the customer acceptance point (PCC). In this case, the electric power company must build a Power Quality Monitoring System (PQMS) at all the customer's entrance points in order to manage the electricity quality, and it is necessary to have very expensive equipments considering the operation speed and precision to acquire data suited to the related standard . Therefore, it is difficult to constantly monitor using PQMS in electric power companies because of high cost of installation and many places to be managed.

The present invention provides a power quality monitoring system and method capable of monitoring power quality by monitoring harmonics generated in a power system.

It is another object of the present invention to provide a power quality monitoring system and method capable of drastically improving a calculation speed for harmonic evaluation of a power system due to reduction of sampling data.

According to an aspect of the invention, a power quality monitoring system is provided.

The power quality monitoring system is connected to the bus and distribution line of the power system, acquires voltage waveforms at each of the bus and distribution lines at the set time intervals, samples and stores the acquired voltage waveform and current waveform at set intervals, A voltage representative waveform and a current representative waveform which are generated by superimposing the voltage waveform and the current waveform on a single cycle to generate and transmit a voltage representative waveform and a current representative waveform, and decompose harmonic components by fast Fourier transform, respectively, And a server for analyzing the harmonic components and monitoring an abnormality of the power system.

According to another aspect of the present invention, there is provided a power quality monitoring method.

The power quality monitoring method includes the steps of acquiring a voltage waveform and a current waveform at predetermined time intervals from each of a bus line and a distribution line of a power system, sampling each of the acquired voltage waveform and current waveform at a predetermined cycle and storing the sampled voltage waveform and current waveform, Generating a voltage representative waveform and a current representative waveform by superposing each of the voltage waveform and the current waveform in one cycle; and FFT-transforming and analyzing the voltage representative waveform and the current representative waveform.

The power quality monitoring system according to an embodiment of the present invention reduces the calculation period of the representative value. Here, the representative value means an RMS calculation value corresponding to a period designated by the user by performing an FFT operation in 12-cycle units defined by the IEC. In the conventional power quality monitoring system, the FFT is calculated in units of 12 cycles in order to calculate representative values. However, in the power quality monitoring system according to the embodiment of the present invention, the sampled waveforms of 12 cycles are successively superimposed Sampling and waveform superimposition is performed at 128 or 256 sampling rates per cycle for a period designated by the user, and a representative waveform is calculated according to a representative value cycle according to the policy of the power supplier. Accordingly, the power quality monitoring system according to an embodiment of the present invention improves the accuracy and reliability compared to the prior art.

In the power quality monitoring system according to an embodiment of the present invention, the calculation of the representative waveform and the FFT conversion operation of the representative waveform are performed separately in the power quality measuring apparatus and the server. The power quality measurement device can transmit the representative waveform only to the server, thereby reducing the load and the network load due to the calculation. Then, the server can perform FFT at a time desired by the user. Accordingly, the power quality monitoring system according to the embodiment of the present invention is easy to expand and the measurement stop is simplified.

In addition, the power quality monitoring system according to an embodiment of the present invention can separate the measurement items for the outgoing lines of the bus and distribution lines separately and measure the voltage waveform and the current waveform for each main transformer of the substation, And the number of channels for waveform measurement is reduced. Accordingly, the power quality monitoring system of the present invention greatly reduces the construction cost compared with the conventional power quality monitoring system.

1 is a diagram illustrating a power quality monitoring system in accordance with an embodiment of the present invention.
2 is a diagram illustrating a configuration of a power quality measuring apparatus according to an embodiment of the present invention.
3 is a diagram illustrating a representative waveform corresponding to a voltage waveform and a current waveform according to an embodiment of the present invention.
4 is a diagram illustrating a server according to an embodiment of the present invention.
5 is a flowchart illustrating a method of measuring power quality by a power quality measuring apparatus according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a power quality monitoring system in accordance with an embodiment of the present invention.

1, a power quality monitoring system 10 according to an embodiment of the present invention includes a power quality measuring apparatus 100 connected to a power system 20 and a representative waveform And a server 200 for performing an FFT (Fast Fourier Transform) calculation function.

The power system 20 is a three-phase four-wire system. The power system 20 includes a bus 50 and a power distribution line 60 that are connected to the main transformer (MTR) 40 of the substation 30. Here, a potentiometer (PT) 70 is installed on the bus bar 50 for each phase. In addition, a current transformer (CT) 80 is installed on the distribution line 60 for each phase.

The power quality measuring apparatus 100 may be installed in units of bank 50 buses connected to the main transformer 40 of the substation 30. [ The power quality measuring apparatus 100 is connected to the draw-out point of each of the bus 50 of the power system 20 and the power distribution line 60. The power quality measuring apparatus 100 acquires a voltage waveform and a current waveform at predetermined time intervals through three channels of three voltage levels of the bus 50 and four channels of currents of the respective power distribution lines 60. [ Further, the power quality measuring apparatus 100 samples the acquired waveform according to the set method. Also, the power quality measuring apparatus 100 generates a representative waveform using the sampled waveform and transmits the representative waveform to the server 200.

The server 200 receives the representative waveform from the power quality measuring apparatus 100 and stores the representative waveform. The server 200 analyzes a representative waveform according to a predetermined method-FFT conversion operation method and analyzes a voltage waveform and a current waveform of the power system 20. The server 200 performs various analyzes and evaluations on the power system 20 by performing decomposition of the waveforms by harmonic order. Thus, the server 200 can check whether or not the power system 20 is abnormal.

2 is a diagram illustrating a configuration of a power quality measuring apparatus according to an embodiment of the present invention. 3 is a diagram illustrating a representative waveform corresponding to a voltage waveform and a current waveform according to an embodiment of the present invention.

2, a power quality measuring apparatus 100 according to an embodiment of the present invention includes a pickup 110, a sampling unit 120, a waveform generating unit 130, a first storage unit 140, (150).

The pickup unit 110 acquires the voltage waveform and the current waveform of the power system 20 connected to the power quality measuring apparatus 100 at predetermined time intervals. For example, the pickup 110 acquires a voltage waveform and a current waveform of the power system in accordance with a time interval set at 1 second, 3 seconds, 10 minutes, 30 minutes, or the like. Here, the method of acquiring the voltage waveform and the current waveform of the power system will be obvious to those skilled in the art, and a separate description thereof will be omitted.

(n은 7 이상의 자연수) 주기로 픽업부(110)를 통해 취득된 전압 파형 및 전류 파형을 샘플링할 수 있다. 여기서는 샘플링부(120)에서 전압 파형 및 전류 파형을 샘플링하는 주기를 샘플링 주기라고 한다.The sampling unit 120 samples the voltage waveform and the current waveform acquired by the pickup unit 110 at a predetermined cycle and converts the sampling waveform into a digital waveform. Here, the sampling unit 120

(n is a natural number equal to or greater than 7) period, the voltage waveform and the current waveform acquired through the pickup unit 110 can be sampled. Here, a period for sampling the voltage waveform and the current waveform in the sampling unit 120 is referred to as a sampling period.

Since the harmonic voltage of the MV system specified by IEC is defined to manage up to 50 orders, a minimum of 128 cycles or 256 cycles is required for harmonic component decomposition. If the sampling unit 120 samples at a sampling period of less than 128 cycles, it may be difficult to obtain accurate harmonic information up to the 50th order. Accordingly, the present specification assumes that the sampling period is 128 cycles or more.

The sampling unit 120 stores the sampled voltage and current waveforms in the first storage unit 140 according to the designated sampling period.

The waveform generating unit 130 generates a representative waveform by superimposing and summing the sampled voltage waveform and the current waveform in one cycle for a predetermined measurement period. Here, the representative waveform can be generated as shown in FIG. For example, the waveform generating unit 130 may generate the sampled voltage waveform and the current waveform, such as the first sampling waveform 310, the second sampling waveform 320, and the third sampling waveform 330 shown in FIG. 3, And the values of the same sampling period are summed to generate a representative waveform.

In an embodiment of the present invention, in order to facilitate understanding and explanation, it is assumed that the measurement period is the maximum demand period. For example, if the maximum demand period is 15 minutes, the measurement period can be set to 15 minutes. Or the measurement period may be set to a period other than the maximum demand period, such as 3 minutes, 10 minutes, and so on.

For example, the waveform generating unit 130 may generate a representative waveform by superimposing and summing the sampled voltage and current waveforms in one cycle during the measurement period, and calculating the average value thereof. The waveform generating unit 130 may generate a representative waveform by superimposing / summing voltage and current waveforms having the same sampling period with respect to the sampled voltage and current waveforms during the measurement period.

In the case of one embodiment of the present invention, as illustrated in FIG. 3, each cycle of the sampled voltage and current waveforms of each of the power quality measuring apparatuses 100 is superimposed in one cycle to generate a representative waveform, The amount of data is drastically reduced.

Generally, voltage waveforms and current waveforms in the power system 20 do not change drastically unless internal and external events occur such as power failure, momentary voltage drop, lightning stroke due to an accident, malfunction, or surge due to opening of the switch.

In one embodiment of the present invention, the representative waveform for the voltage and current waveforms sampled during the measurement period in the power quality measuring apparatus 100 may be generated and transmitted to the server 200 at the remote site.

Accordingly, the server 200 can calculate the sample data corresponding to the half period of the representative waveform received by the power quality measuring apparatus 100, and evaluate the harmonics.

The first storage unit 140 stores the voltage and current waveform sampled through the sampling unit 120 during the measurement period. In addition, the first storage unit 140 stores algorithms necessary for operating the power quality measuring apparatus 100 according to an embodiment of the present invention.

The transmitting unit 150 transmits the representative waveform generated through the waveform generating unit 130 to the remote server 200.

4 is a diagram illustrating a server according to an embodiment of the present invention.

4, a server 200 according to an exemplary embodiment of the present invention includes a receiving unit 210, a second storing unit 220, and a calculating unit 230. [

The receiving unit 210 receives the representative waveform transmitted from the power quality measuring apparatus 100.

The second storage unit 220 stores the representative waveform transmitted from the power quality measuring apparatus 100. Here, the second storage unit 220 may be formed in the form of a database for storing representative waveforms.

The calculating unit 230 performs FFT transform of the representative waveform according to a predetermined method to analyze the voltage waveform and the current waveform of the power system 20. [ The arithmetic operation unit 230 performs decomposition of the waveform of each harmonic order to calculate a harmonic evaluation value. The calculation unit 230 performs various analyzes and evaluations on the power system 20 using the calculated evaluation values. Thus, the server 200 can check whether or not the power system 20 is abnormal.

Here, the operation unit 230 can perform FFT transform only when the user's instruction is input, and analyze the voltage waveform and the current waveform.

The power quality monitoring system according to an embodiment of the present invention reduces the calculation period of the representative value as compared with the conventional power quality monitoring system. Here, the representative value means an RMS calculation value corresponding to a period designated by the user by performing an FFT operation in 12-cycle units defined by the IEC. In the conventional power quality monitoring system, the FFT is calculated in units of 12 cycles in order to calculate representative values. However, in the power quality monitoring system according to the embodiment of the present invention, the sampled waveforms of 12 cycles are successively superimposed Sampling and waveform superimposition is performed at 128 or 256 sampling rates per cycle for a period designated by the user, and a representative waveform is calculated according to a representative value cycle according to the policy of the power supplier. Accordingly, the power quality monitoring system according to an embodiment of the present invention improves the accuracy and reliability compared to the prior art.

In the power quality monitoring system according to an embodiment of the present invention, the calculation of the representative waveform and the FFT conversion operation of the representative waveform are performed separately in the power quality measuring apparatus and the server. The power quality measurement device can transmit the representative waveform only to the server, thereby reducing the load and the network load due to the calculation. Then, the server can perform FFT at a time desired by the user. Accordingly, the power quality monitoring system according to the embodiment of the present invention is easy to expand and the measurement stop is simplified.

In addition, the power quality monitoring system according to an embodiment of the present invention can separate the measurement items for the outgoing lines of the bus and distribution lines separately and measure the voltage waveform and the current waveform for each main transformer of the substation, And the number of channels for waveform measurement is reduced. Accordingly, the power quality monitoring system of the present invention greatly reduces the construction cost compared with the conventional power quality monitoring system.

5 is a flowchart illustrating a method of measuring power quality by a power quality measuring apparatus according to an embodiment of the present invention.

Each step performed below is performed by the power quality measuring device included in the power quality monitoring system and the internal components of the server, but is collectively referred to as a power quality measuring device and a server in order to facilitate understanding and explanation .

In step S10, the power quality measuring apparatus is connected to the bus line and the power distribution line of the power system to acquire the three-channel voltage waveform of the bus line and the four channel current waveform of each power line at the set time. The power quality measuring device obtains the voltage waveform by receiving the three-channel voltage for each phase from the transformer for meters installed on the bus. Further, the power quality measuring apparatus receives the 4-channel current from the current transformer provided in each distribution line to acquire the current waveform.

In step S20, the power quality measuring apparatus samples the acquired voltage and current waveforms at a predetermined sampling period, and stores the sampled voltage and current waveforms. Since these are the same as those described above, an overlapping description thereof will be omitted.

In step S30, the power quality measuring apparatus generates a representative waveform by superimposing and summing the sampled voltage and current waveforms in one cycle in the measurement period. For example, the power quality measuring apparatus can superimpose sampled voltage and current waveforms in a single cycle, calculate a mean value thereof, and generate a representative waveform using the average value. Next, the power quality measuring apparatus transmits the generated representative waveform to the server.

In step S40, the server performs FFT conversion on the transmitted representative waveform to calculate it. The server then analyzes the representative waveform. The server calculates the harmonic evaluation value by performing decomposition of the waveform by the harmonic order. The server performs various analyzes and evaluations on the power system using the calculated evaluation values. Through this, the server confirms whether or not the power system is abnormal.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

10: Power quality monitoring system
20: Power system
50: Mothership
60: Distribution line
100: Power quality measuring device
200: Server

Claims (11)

An apparatus for monitoring a power quality of a power system,
A voltage waveform is acquired at each of the bus lines and the power distribution line at predetermined time intervals connected to a bus line and a distribution line of the power system, and the acquired voltage waveform and current waveform are sampled and stored at predetermined intervals, And a power quality measuring device for generating and transmitting a voltage representative waveform and a current representative waveform by superimposing the current waveform in one cycle; And
And a server for receiving the voltage representative waveform and the current representative waveform, decomposing harmonic components by fast Fourier transform respectively, and monitoring abnormalities of the power system by analyzing the harmonic components.
The method according to claim 1,
The power quality measuring device
A pickup unit for acquiring a voltage waveform and a current waveform from the power system at the set time intervals;
A sampling unit for sampling and storing the acquired voltage and current waveforms at the predetermined sampling period for harmonic component decomposition;
A waveform generating unit for generating the voltage representative waveform and the current representative waveform by superimposing the sampled voltage waveform and the current waveform in one cycle for the set measurement period; And
And a transmitter for transmitting the representative waveform to the server through a communication network.
3. The method of claim 2,
The pick-
Wherein the voltage waveforms of three channels are acquired from the transformer for meters provided in the bus and the current waveforms of four channels are obtained from the current transformers provided in the respective distribution lines.
3. The method of claim 2,
Wherein the waveform generating unit generates the voltage representative waveform and the current representative waveform with an average value of each of the voltage waveforms and the current waveforms superimposed in one cycle.
5. The method of claim 4,
Wherein each of the voltage representative waveform and the current representative waveform is a half period value of an entire period of the superimposed voltage waveform and the current waveform.
3. The method of claim 2,
Wherein the sampling unit samples each of the acquired voltage waveform and current waveform by 128 or more cycles.
The method according to claim 1,
Wherein the server further comprises a storage unit for storing the voltage representative waveform and the current representative waveform.
A method for monitoring power quality of a power system,
(a) acquiring a voltage waveform and a current waveform from a bus line and a distribution line of a power system at predetermined time intervals;
(b) sampling and storing the acquired voltage waveform and current waveform at predetermined intervals;
(c) generating a voltage representative waveform and a current representative waveform by superposing each of the voltage waveform and the current waveform sampled during a set measurement cycle in one cycle; And
(d) FFT-transforming and analyzing the voltage representative waveform and the current representative waveform.
9. The method of claim 8,
The step (a)
Obtains the voltage waveform from the bus line through three channels of different voltages,
And the current waveform is acquired through the current channel in the power distribution line.
9. The method of claim 8,
The step (c)
Wherein the voltage waveform and the current waveform of the same period of the voltage waveform and the current waveform sampled during the measurement period are overlapped with each other.
9. The method of claim 8,
The step (c)
Wherein the voltage representative waveform and the current representative waveform are generated by an average value of the voltage waveforms and the current waveforms superimposed on one cycle.

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