KR20210125313A - Fault recording device for monitoring power quality - Google Patents

Abstract

The present invention relates to a failure recording device having a power quality monitoring function and having a digital signaling device. The failure recording device comprises: a voltage fluctuation monitoring unit which measures whether a voltage magnitude exceeds the allowable standard and a holding time exceeding the allowable standard for the valid value of a received voltage to determine a failure due to short-time voltage fluctuation or a failure due to long-term voltage fluctuation; a harmonic monitoring unit that extracts harmonic components by performing discrete Fourier transform on the instantaneous value of a received voltage or current, and determines that it is a failure when a THD calculated using the extracted harmonic components exceeds a set reference THD; and a voltage unbalance monitoring unit that calculates a zero-phase voltage and a positive-component voltage by using the phasor value of a three-phase voltage converted from the instantaneous value of a received three-phase voltage, calculates an unbalance factor by using the calculated zero-phase voltage and the positive-sequence voltage, and determines a failure when one unbalance ratio exceeds a standard unbalance ratio.

Description

Fault recording device for monitoring power quality

The present invention relates to a power system monitoring technology, and to a failure recording device having a power quality monitoring function capable of evaluating and recording the degree of power quality.

In general, power quality is a measure of how stable or within the allowable standard of elements such as voltage magnitude, frequency, and waveform constituting electricity.

When the power quality in the power system deteriorates, the utilization rate of electrical equipment is lowered, and problems such as a decrease in output, an increase in the temperature of the power system, an increase in loss, a decrease in lifespan, a malfunction, and a failure occur. Regarding the power quality that causes these problems, the Ministry of Trade, Industry and Energy is concerned about power quality such as frequency (Hz), voltage magnitude (V), harmonic distortion factor (%), and allowable (standard) range of voltage unbalance factor (%). related standards, IEEE 1159, IEC 61000-4-30, EN50160, IEC 60050-615, etc. are established.

1. Domestic Registered Patent No. 10-2048429 (Registration Date: 2019.11.19.) (Name: Power quality diagnosis system and method using power frequency and output correlation) 2. Domestic Registered Patent No. 10-1978505 (Registration date: 2019.05.08.) (Name: Electricity quality monitoring device for power distribution system)

The problem to be solved by the present invention is to measure the power quality for all of the voltage magnitude (V), harmonic distortion ratio (%), and voltage unbalance ratio (%), which are factors related to power quality, and have a power quality monitoring function to record in case of failure. To provide a fault recorder.

It is not limited to the technical problems as described above, and other technical problems may be inferred from the following embodiments.

The present invention according to an embodiment for solving the above problem relates to a failure recording device for monitoring the power quality of a power system, which constantly measures the voltage and current of a transformer and a current transformer, filters the noise, and amplifies the output to a predetermined level An analog signal input circuit, a digital signal input circuit that insulates and noise-filters a contact signal input to a voltage level, and converts and amplifies the contact signal into a logic signal and outputs it, the analog signal input circuit and the digital signal input circuit An analog/digital conversion module that converts the signal output from the signal to digital code data (ADC; Analog to Digital Converter) and an output circuit, and a digital signal processing device having a built-in algorithm for acquiring, measuring, starting, and generating an event message of the input/output signal of the failure recording device, wherein the digital signal processing device includes an rms value of the received voltage. Voltage fluctuation monitoring unit that determines whether the voltage magnitude exceeds the allowable standard and the holding time exceeding the allowable standard for short-time voltage fluctuations or failures due to long-term voltage fluctuations. The harmonic monitoring unit that converts and extracts the harmonic component, and determines that it is a failure when the THD (Total Harmonic Distortion, unit %) calculated using the extracted harmonic component exceeds the set standard THD; The zero-phase voltage and the positive-sequence voltage are calculated using the phasor value of the three-phase voltage converted from the instantaneous value of the phase voltage. A voltage unbalance monitoring unit that determines a failure when exceeding this reference unbalance ratio is included.

The digital signal processing device monitors the rms value of the received voltage for a unit monitoring time, determines the number of times the rms value exceeds the set reference rms value, and determines that it is a failure when the number of excess exceeds the set number of arrivals. It may further include a voltage fluctuation monitoring unit.

The voltage fluctuation monitoring unit compares the magnitude of the effective value of the received voltage with at least one of a first reference value that is 1.1pu of the rated voltage, a second reference value that is 0.9pu, and a third reference value that is 0.1pu, and the first reference value is greater than or equal to the first reference value. When it falls within one of the range, the second range that is equal to or less than the second reference value and is greater than the third reference value, and the third range that is less than or equal to the third reference value, the holding time exceeding the allowable standard may be measured.

The harmonic monitoring unit performs discrete Fourier transform on the instantaneous value of the received voltage or current to extract harmonic components from the 1st to the 63rd, and the harmonic components from the 1st to the 63rd are THD using Equation 2 below can be calculated.

According to an embodiment of the present invention, the present invention measures the power quality with respect to all of the voltage magnitude (V), harmonic distortion ratio (%), and voltage unbalance ratio (%), which are factors related to power quality with one device, and records the power quality in case of failure. make it possible

1 is a power system diagram to which a failure recording device having a power quality monitoring function according to an embodiment of the present invention is applied.
2 is a hardware configuration diagram of a failure recording device having a power quality monitoring function according to an embodiment of the present invention.
3 is a software configuration diagram of a failure recording device having a power quality monitoring function according to an embodiment of the present invention.
4 is a block diagram of a main part of a failure recording apparatus having a power quality monitoring function according to an embodiment of the present invention.
5 is a flowchart of an operation of monitoring voltage fluctuations in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.
6 is a flowchart of an operation of monitoring harmonic analysis in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.
7 is a flowchart of an operation of monitoring voltage imbalance in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.
8 is a flowchart of an operation of monitoring voltage fluctuations in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.

Below, some embodiments will be described clearly and in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains (hereinafter, those skilled in the art) can easily practice the present invention. will be. Also, the term “unit” used in the specification may mean a hardware component or a circuit.

Hereinafter, a fault recording device having a power quality monitoring function according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a power system diagram to which a failure recording device having a power quality monitoring function according to an embodiment of the present invention is applied. Referring to FIG. 1 , a failure recording device 100 having a power quality monitoring function according to an embodiment of the present invention is applied to a single bus-3 line system, and is applied from a transformer 02 and a current transformer 03, 06, and 08, respectively. Acquire the contact signal indicating the operation of the power equipment input from the input power system voltage and current signals, the power supply 5 that collectively displays the receiving end including the generator or transformer, and the circuit breaker 7 for opening and closing the load , and measure the power quality for voltage magnitude (V), harmonic distortion (%), and voltage unbalance ratio (%) using instantaneous or rms values and waveforms of voltage and current.

And when the failure recording device 100 of the present invention detects a failure or abnormality in the power system as a result of the measurement of the power quality, it records and manages it. Of course, the failure recording apparatus 100 of the present invention can print the recorded failure history, reproduce the power system state by calling the failure history data, and analyze the electric power system state such as failure or abnormality.

2 is a hardware configuration diagram of a failure recording device having a power quality monitoring function according to an embodiment of the present invention. Referring to FIG. 2 , the failure recording device 100 of the present invention includes an input/output terminal 10 , a power supply circuit 101 , an analog input circuit 102 , a digital input circuit 103 , a digital output circuit 104 , and a power supply. Supply device 105, signal processing device (DSP: Digital Signal Processor, 106), A/D converter 107, DI controller 108, DO controller 109, MMI processing device (CPU, 110), semiconductor memory 111 and HDD/FDD 112 . In addition, the failure recording device 100 of the present invention includes a system state measuring unit 121a, a facility state measuring unit 121b, a key controller 113, a display driving unit 114, a printer controller 115 and a communication controller 116. ) may further include at least one of.

Referring to FIG. 2 , the input/output terminal 10 is a connection mechanism for connecting the device 100 of the present invention and an external device. The power supply circuit 101 is a power operation circuit composed of various circuit breakers, switchgear, and relays in order to safely control the incoming power through the input/output terminal 10 . The power supply device 105 converts the power flowing in through the power circuit 101 to supply DC power to each element of the present invention, comprising an AC/DC converter and an AC/AC converter. it is a device

Insulation and conditioning of the signal input to the device 100 of the present invention via the input/output terminal 10 is performed in the analog input circuit 102 and the digital input circuit 103 . The analog input circuit 102 is a circuit configured to include a transformer and a current transformer for insulating and converting analog voltage and current signals, a filter for removing noise, an amplifier circuit for adjusting the signal level, and the like, and the digital input circuit 103 is a circuit composed of a photoelectric element for insulating a contact signal input at a voltage level, a filter for removing noise, and an amplifier circuit for converting the contact signal into a logic signal.

The conversion of the outputs of the analog input circuit 102 and the digital input circuit 103 into digital code data in the form of data that the signal processing device 106 can recognize is an A/D (analog/digital) conversion device 107 and a DI (digital signal input) controller 108 . The A/D converter 107 simultaneously acquires the voltage level analog signals of all channels output from the analog input circuit 102 and converts them into digital code data. am. The DI controller 108 is a circuit configured including a semiconductor device for latching the logic signal output from the digital input circuit 103 until the signal processing device 106 reads it.

Digital code data output from the AD converter 107 and the DI controller 108 is processed in the signal processing device 106 via the signal processing device bus line A and written to the semiconductor memory 111 .

The signal processing device 106 is a semiconductor device dedicated to signal processing that manages each component related to signal processing from signal acquisition to output, and is equipped with software programs such as acquisition, measurement, and activation of signals. The signal processing device bus A is a line on a printed circuit board for sending and receiving commands and data between each component of the present invention, and the semiconductor memory 111 stores programs and processing data mounted on the signal processing device 106 . It is a semiconductor device for

When the system state evaluated by the signal processing device 106 is determined to be faulty or abnormal, an event signal for transmitting the state to the outside via the DO (digital signal output) controller 109 and the digital output circuit 104 is generated do.

Here, the DO controller 109 is a circuit for converting and latching an event signal of a digital code transmitted via the signal processing device bus A into a logic signal. And the digital output circuit 104 is an amplifier circuit for amplifying the logic signal commanded by the DO controller 109, and a relay circuit for outputting a contact (voltage/non-voltage contact) that generates an alarm or operation signal to a peripheral or external device. It is a circuit composed of

MMI (Man-Machine Interface) processing device 110 and various terminals to transmit system state information processed by the signal processing device 106 to a user and an external device (host system) or vice versa to receive a set value and an external command An MMI processing system including a device driving module is configured. Here, the MMI processing unit 110 exchanges commands and data with the signal processing unit 106 via the signal processing unit bus A, while recording, analyzing, setting, displaying, printing, etc. MMI (Multimedia Interface) It is a semiconductor device that is a general central processing unit (CPU) equipped with a software program for managing the components related to the .

The MMI processing device busbar B is a wire path of a printed circuit board for transmitting and receiving commands and data between the MMI processing device 110 and the MMI terminal element, and as the MMI terminal element, a key controller 113 and a display driver 114 ), a printer controller 116, a communication controller 116, and a hard disk drive 117 constitute the MMI processing system.

The key controller 113 is a driver for driving a key for inputting or modifying a set value and performing an operation operation, and the display driver 114 is a driver for driving a monitor for displaying the power system state and operation operation state, and a printer. The controller 115 is a printer driving driver for printing the power system status and operation operation status, and the communication controller 116 is a communication driver for communication with the remote monitoring and control device. The hard disk drive 112 is a driver for driving a hard disk, which is a recording medium for storing the power system state and operation operation state.

The system state measurement unit 121a is a software filter program for filtering the instantaneous voltage and current values of the power system that is the output of the analog signal acquisition unit 118, and the voltage, current, power, reactive power, frequency, etc. from the instantaneous voltage and current values. Various calculation algorithms such as voltage and current effective value measurement algorithm, voltage and current phasor measurement algorithm, power, phase and power factor measurement algorithm using voltage and current phasor, and frequency measurement algorithm to measure the power system operation function of It is a software module composed of a software measurement program for realization.

The equipment state measurement unit 121b is a logic program for evaluating the state of the power equipment expressed by the digital logic signal acquired by the digital signal acquisition unit 119 .

3 is a software configuration diagram of a failure recording device having a power quality monitoring function according to an embodiment of the present invention. Referring to FIG. 3, the power monitoring unit 117 is a software program that simultaneously samples the breaker operation indication contact and the power level detector output signal of the power circuit 12 of FIG. 2 and converts it into a logic value, chattering of the contact and It is a program composed of software filters to remove the effect of noise.

The analog signal acquisition unit 118 is a driving program of the A/D converter 107 that simultaneously samples the instantaneous voltage and current values of each analog signal channel input to the device 100 of the present invention and converts them into digital code values. . The digital signal acquisition unit 119 is a software program for driving the DI controller 108 that simultaneously samples the contact signals of each digital signal channel input to the device 100 of the present invention and converts them into logic values, contact chattering and noise It is a program consisting of a software filter to remove the influence of

The digital signal output unit 120 is a program module for driving the DO controller 109 that operates by issuing a start signal to generate an event signal according to the start mode, type, and cause of the start.

The memory unit 122 is a program loaded in the semiconductor memory 111 according to a file format set for the power system state and quality measurement data for a set time before and after the event by issuing a start signal.

The signal processing processor 123 is a main program that manages each signal processing software module of the present invention and schedules a processing sequence, and is mounted in the signal processing apparatus DSP 106 .

The power quality monitoring unit 124 receives the output of the signal processing processor 123, that is, instantaneous values, rms values, etc. of voltage and current, and uses the received instantaneous values or rms values to determine the voltage magnitude (V), harmonic distortion rate, and the like. This is a program that measures the power quality for both (%) and voltage unbalance ratio (%). At this time, however, the power quality monitoring unit 124 has an algorithm for measuring the voltage fluctuation phenomenon for a long time, an algorithm for measuring the voltage fluctuation phenomenon, an algorithm for measuring the harmonic distortion rate, and an algorithm for measuring the voltage unbalance rate, and the signal processing device ( DSP, 106).

The trigger module 124-1 receives the output of the power quality monitoring unit 124 as an input, evaluates the output of the power quality monitoring unit 124, and logs data and generates an event if there is a failure or abnormal condition. It is a software module for making a signal, and is mounted in the signal processing device (DSP, 106).

The recording unit 125 is a database program for continuously recording, preserving, and searching the power quality measurement data recorded in the memory unit 122 a predetermined number of times.

The MMI processor 126 is a sub-main program that manages each MMI software module of the present invention while exchanging data with the signal processing processor 123 and schedules a processing sequence, and is mounted in the MMI processing unit (CPU, 110).

The analysis unit 127 calls the data file stored in the recording unit 125 for the purpose of reproducing and analyzing the user's past power system operation state, setting contents, and power quality, and the instantaneous value, effective value or phasor data and Waveform and facility status and events are reproduced on the same time axis, and frequency spectrum analysis for power system failure cause identification and quality analysis, power fluctuation phenomenon and system stability evaluation, power system operation, quality such as power supply and demand, power planning, etc. It is a power system and quality regeneration and analysis program to obtain data for management.

The key scan unit 128, the display unit 129, the print module 130, and the communication module 131 are software program modules for driving peripheral devices that are MMI components, and the key scan unit 128 is a keyboard driving software program. ; The display unit 129 is composed of a monitor driving program and a screen display program, and displays instantaneous values, rms values, phasor data, waveforms, equipment status and events on the same time axis, or frequency spectrum of instantaneous values and frequency spectrum analysis results of rms values. Display data and waveforms. The printing unit 130 is composed of a printer driving program and a program such as a hard copy of the screen and a report output form. program.

Hereinafter, an operation of the failure recording apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. 4 to 8 .

4 is a block diagram of a main part of the failure recording device having a power quality monitoring function according to an embodiment of the present invention, and is an internal block diagram of the power quality monitoring unit 124. As shown in FIG. Referring to FIG. 4 , the power quality monitoring unit 124 includes a voltage fluctuation monitoring unit 124a, a harmonic monitoring unit 124b, a voltage imbalance monitoring unit 124c, and a voltage fluctuation monitoring unit 124d.

The voltage fluctuation monitoring unit 124a measures the magnitude of the effective value of the received voltage to determine whether the voltage exceeds the permissible standard and whether the voltage exceeds the permissible standard and determines whether the failure is due to short-time voltage fluctuations or long-term voltage fluctuations. do.

A detailed operation of the voltage fluctuation monitoring unit 124a will be described with reference to FIG. 5 . 5 is a flowchart of an operation of monitoring voltage fluctuations in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.

Referring to FIG. 5 , the voltage fluctuation monitoring unit 124a receives, from the signal processing device 106 , the time for which the RMS value of the voltage and the RMS value (unit, pu) of the received voltage are calculated in real time ( S501 ). Then, the voltage fluctuation monitoring unit 124a compares whether the effective value of the received voltage exceeds three set reference values, that is, the first reference value, the second reference value, and the third reference value (S502), and the effective value of the voltage at the time of exceeding the reference value It is determined to what extent the value belongs to a size range (S503). Here, the first reference value is 1.1pu of the rated voltage, the second reference value is 0.9pu, and the third reference value is 0.1pu.

Specifically, the voltage fluctuation monitoring unit 124a determines whether the received rms value is greater than or equal to the first reference value of 1.1pu, and if the rms value is less than 1.1pu, the rms value is greater than the third reference value of 0.1pu and the second reference value Determines whether it is smaller than 0.9pu. In addition, the voltage fluctuation monitoring unit 124a determines whether the effective value is 0.1pu or less, which is the third reference value. That is, the voltage fluctuation monitoring unit 124a identifies which size range the rms value belongs to among a first range greater than or equal to the first reference value, a second range that is less than or equal to the second reference value and greater than the third reference value, and a third range that is less than or equal to the third reference value. do.

Then, the voltage fluctuation monitoring unit 124a repeats the steps S501 to S503 with respect to the received effective value, and if the received effective value is continuously maintained within the first, second, and third ranges, the holding time is counted (S504). ).

While counting the holding time, the voltage fluctuation monitoring unit 124a determines whether the voltage rms value is greater than the second reference value and returned to a normal state smaller than the first reference value (S505), and the rms voltage of the voltage returns to the normal state. In this case, the counting of the holding time is stopped and the failure type is determined using the counted holding time and the magnitude of the rms value of the voltage at the time of initial detection of the failure (S506).

At this time, the determination of the failure type is determined as a short-time voltage fluctuation if the voltage at the time of initial detection of the received failure falls within one of the first to third ranges and the holding time is 1 minute or less, as shown in FIG. If the voltage at the time of initial detection of the failure falls within one of the first to third ranges and the holding time exceeds 1 minute, it is determined that the voltage fluctuates for a long time.

In the case of short-time voltage fluctuations, the voltage fluctuation detection unit 124a determines that the voltage is 'Instantaneous' if the holding time of the voltage is greater than 0.5 cycle (about 0.08 seconds) and less than or equal to 30 cycles (about 0.5 seconds), 30cycle (about 0.5 seconds) If it is greater than 3 seconds, it is judged as 'Momentary', and if it is greater than 3 seconds and less than 1 minute, it is judged as 'Temporary/'.

And the voltage fluctuation detection unit 124a determines that the voltage at the time of initial failure detection is within the first range as 'Swell', and if it falls within the second range, it is determined as 'Sag', and if it falls within the third range, It is judged as 'Interruption'.

In the process S506, the voltage fluctuation detection unit 124a has a voltage level at the initial detection time of the failure within the first range, and the holding time is greater than 0.5 cycle (about 0.08 seconds) and less than or equal to 30 cycles (about 0.5 seconds), the voltage fluctuation The detection unit 124a determines that the type of failure is 'Swell (Ins)'.

In the case of long-term voltage fluctuations, the voltage fluctuation detection unit 124a determines that the voltage at the time of initial detection of the failure is 'Interruption sustained' if the magnitude of the voltage is 0.0pu ~ 0.1pu, and 'Under-Voltages' if 0.1pu ~ 0.9pu If it is 1.1pu or higher, it is judged as 'Over-Voltages'.

When the voltage fluctuation monitoring unit 124a determines the failure type, it stores information about the failure type, that is, information on the failure type, and then repeats steps S501 to S507 (S507).

Next, the operation of the harmonic monitoring unit 124b will be described with reference to FIG. 6 . 6 is a flowchart of an operation of monitoring harmonic analysis in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.

Referring to FIG. 6 , the harmonic monitoring unit 124b receives an instantaneous value of one cycle of voltage or current (refer to FIG. 6B ) ( S601 ). Then, the harmonic monitoring unit 124b performs DTF (Discrete Fourier Transform, Discrete Fourier Transform) on the instantaneous value of one cycle of the received voltage or current as shown in Equation 1 below to obtain harmonic components (DC) from the 1st to the 63rd. component) and extracted (decomposed) (S602).

(Equation 1)

Then, the harmonic monitoring unit 124b calculates THD (Total Harmonic Distortion, total harmonic distortion, unit %) using the following Equation 2 for the 1st to 63rd harmonic components (S603), and calculates the calculated THD and The set reference THD is compared (S604).

(Equation 2)

The harmonic monitoring unit 124b determines whether the calculated THD exceeds the reference THD through the comparison of the process S604 (S605), and if it is determined that the calculated THD exceeds the reference THD, it is a failure in which the quality of harmonics exceeds the reference value. After determining and storing the fault data (eg, voltage and current waveforms) (S606), processes S601 to S605 are continuously performed.

Of course, if it is determined that the calculated THD does not exceed the reference THD, the harmonic monitoring unit 124b performs a normal processing operation without taking a separate action (S607), and then proceeds to the steps S601 to S605.

7 is a flowchart of an operation of monitoring voltage imbalance in a failure recording device having a power quality monitoring function according to an embodiment of the present invention. Referring to FIG. 7 , the failure recording apparatus 100 of the present invention sets three-phase voltages (U-phase voltage, V-phase voltage, and W-phase voltage) (S701). Then, the voltage imbalance monitoring unit 124c receives the instantaneous value of the three-phase voltage (S702, see FIG. 7B), and converts the received instantaneous value into a phasor (complex number) format (S703).

_{The voltage imbalance monitoring unit 124c calculates the zero-segment voltage (V o} ) using the following Equation 3 with respect to the phasor value of the converted three-phase voltage, and uses the following Equation 4 to calculate the normal-sequential voltage (V) ₁ ) is calculated, and the reverse-phase voltage (V ₂ ) is calculated using Equation 5 below (S704).

(Equation 3)

(Equation 4)

(Equation 5)

In Equations 3 to 5, V _A is the voltage of the U phase, V _B is the voltage on phase V, and V _C is the voltage on phase W.

Then, the voltage unbalance monitoring unit 124c applies the following Equation 6 to the positive-sequence _{voltage (V 1} ) and the negative-sequence voltage (V _{2 ) calculated using Equations 4 and 5 to the unbalance factor (} Unbalance Factor) is calculated (S705).

(Equation 6)

Then, the voltage unbalance monitoring unit 124c compares the calculated unbalance ratio with a preset reference unbalance ratio (S706), and determines whether the calculated unbalance ratio exceeds the reference unbalance ratio (S707).

When the voltage imbalance monitoring unit 124c determines that the unbalance ratio calculated through the process S707 exceeds the reference imbalance ratio, it is determined that there is a failure, stores the failure data (eg, voltage and current waveform data), and then processes S701 to S706. is repeatedly performed (S708).

On the other hand, if the voltage imbalance monitoring unit 124c determines that the unbalance ratio calculated through the process S707 does not exceed the reference unbalance ratio, it performs a normal processing operation without taking a separate action (S709), and processes S701 to S707. is performed repeatedly.

8 is a flowchart of an operation of monitoring voltage fluctuations in a failure recording device having a power quality monitoring function according to an embodiment of the present invention.

Referring to FIG. 8 , first, when the user designates a set period and number of times, the device 100 of the present invention registers the set time and number of times designated by the user ( S801 ). Here, the set time is the unit monitoring time performed by the voltage fluctuation monitoring unit 124d, and the number of times is the number of times the rms voltage measured during the unit monitoring time exceeds the reference rms value input in advance.

The voltage fluctuation monitoring unit 124d receives the unit rms value of one voltage cycle (S802).

The voltage fluctuation monitoring unit 124d detects the received unit RMS voltage and determines whether the detected voltage is equal to or greater than a set reference value (reference voltage). The voltage fluctuation monitoring unit 124d performs an operation of monitoring whether the unit rms voltage is equal to or greater than the reference value (reference voltage) or not, for a plurality of unit rms values received during the set unit monitoring time, and accordingly The number of times the effective value has reached the reference value is determined (S803).

Then, the voltage fluctuation monitoring unit 124d compares the determined number of arrivals with the preset number of arrivals (S804), and determines whether the determined number of arrivals exceeds the set number of arrivals (S805).

When the voltage fluctuation monitoring unit 124d determines that the number of arrivals determined through the process S805 exceeds the set number of arrivals, the voltage fluctuation monitoring unit 124d determines that it is a failure and stores the failure data (eg, voltage and current waveform data) (S806), the process S801 to S805 are repeatedly performed.

On the other hand, if the voltage fluctuation monitoring unit 124d determines that the number of arrivals identified through the process S805 does not exceed the set number of arrivals, the normal processing operation is performed without taking a separate action (S807), and the processes S801 to S805 are repeated. to do it

The above descriptions are intended to provide exemplary configurations and acts for implementing the present invention. The technical spirit of the present invention will include not only the embodiments described above, but also implementations that can be obtained by simply changing or modifying the above embodiments. In addition, the technical spirit of the present invention will include implementations that can be achieved by easily changing or modifying the embodiments described above in the future.

100: fault recorder 101: power circuit
102: analog input circuit 103: digital input circuit
104: digital output circuit 105: power supply
106: signal processing device (DSP) 107: A/D converter
108: DI controller 109: DO controller
110: MMI processing unit (CPU) 111: semiconductor memory
112: HDD/FDD 113: key controller
114: display driver 115: printer controller
116: communication controller 117: power monitoring unit
118: analog signal acquisition unit 119: digital signal acquisition unit
120: digital signal output unit 121a: system state measurement unit
121b: equipment state measurement unit 122: memory unit
123: signal processing processor 124: power quality monitoring unit
124-1: Starter 125: Recorder
126: MMI processor 127: analysis unit
128: key scan unit 129: display unit
130: printing unit 131: communication unit
124a: voltage fluctuation monitoring unit 124b: harmonic monitoring unit
124c: voltage imbalance monitoring unit 124d: voltage fluctuation monitoring unit

Claims (4)

In the fault recording device for monitoring the power quality of the power system,
An analog signal input circuit that constantly measures the voltage and current of the transformer and current transformer, filters the noise, and amplifies it to a predetermined level and outputs it;
A digital signal input circuit that insulates and noise-filters a contact signal input to a voltage level, converts and amplifies the contact signal into a logic signal, and outputs;
an analog/digital conversion module that converts signals output from the analog signal input circuit and the digital signal input circuit into digital code data (ADC; Analog to Digital Converter);
A digital output circuit that outputs a predetermined event message to an external device when it is determined that the power system is faulty/abnormal as a result of the power system monitoring, and
and a digital signal processing device having a built-in algorithm for acquiring, measuring, starting, and generating event messages of the input/output signal of the failure recording device,
The digital signal processing device,
A voltage fluctuation monitoring unit that measures whether the voltage magnitude exceeds the allowable standard and the holding time exceeding the allowable standard for the rms value of the received voltage to determine a failure due to a short-time voltage fluctuation or a failure due to a long-term voltage fluctuation;
In case the THD (Total Harmonic Distortion, unit %) calculated using the extracted harmonic component is extracted by discrete Fourier transform of the instantaneous value of the received voltage or current exceeds the set standard THD a harmonic monitoring unit that determines a failure; and
Using the phasor value of the three-phase voltage converted from the instantaneous value of the received three-phase voltage, the zero-phase voltage and the positive-sequence voltage are calculated, and the unbalance factor is calculated using the calculated zero-phase voltage and the positive-sequence voltage. A voltage unbalance monitoring unit that determines a failure when one unbalance ratio exceeds the standard unbalance ratio;
A fault recorder with a power quality monitoring function, including: In claim 1,
The digital signal processing device monitors the rms value of the received voltage for a unit monitoring time, determines the number of times the rms value exceeds the set reference rms value, and determines that it is a failure when the number of excess exceeds the set number of arrivals. A fault recording device having a power quality monitoring function further comprising a voltage fluctuation monitoring unit. In claim 1 or 2,
The voltage fluctuation monitoring unit compares the magnitude of the effective value of the received voltage with at least one of a first reference value that is 1.1pu of the rated voltage, a second reference value that is 0.9pu, and a third reference value that is 0.1pu of the rated voltage. A failure recording device having a power quality monitoring function for measuring a holding time exceeding an allowable standard when it falls within one of a range, a second range that is less than the second reference value and is greater than the third reference value, and a third range that is less than or equal to the third reference value. In claim 3,
The harmonic monitoring unit performs discrete Fourier transform on the instantaneous value of the received voltage or current to extract harmonic components from the 1st to the 63rd, and the harmonic components from the 1st to the 63rd are THD using the following equation A fault recorder with a power quality monitoring function that calculates

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