WO2015189996A1 - デジタル保護リレー - Google Patents
デジタル保護リレー Download PDFInfo
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- WO2015189996A1 WO2015189996A1 PCT/JP2014/065781 JP2014065781W WO2015189996A1 WO 2015189996 A1 WO2015189996 A1 WO 2015189996A1 JP 2014065781 W JP2014065781 W JP 2014065781W WO 2015189996 A1 WO2015189996 A1 WO 2015189996A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
- G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
- G01R19/16547—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies voltage or current in AC supplies
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/15—Indicating that frequency of pulses is either above or below a predetermined value or within or outside a predetermined range of values, by making use of non-linear or digital elements (indicating that pulse width is above or below a certain limit)
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/05—Details with means for increasing reliability, e.g. redundancy arrangements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/262—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2513—Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
Definitions
- the present invention relates to a digital protection relay, and more particularly to a technique for appropriately correcting an error in input data caused by an analog element for acquiring at least current or voltage information as an analog signal from a power system.
- digital protection relays can be used to measure the amount of electricity such as voltage and current values of a system from a current transformer (CT (Current Transformer)), instrument transformer (PT (Potential Transformer), or VT (Voltage Transformer)). Is acquired as an analog signal by the analog input element.
- CT Current Transformer
- PT Temperatur Transformer
- VT Voltage Transformer
- the digital protection relay samples an analog signal at a predetermined cycle and converts it into digital data by an AD (Analog to Digital) converter.
- the digital protection relay determines the presence or absence of a system failure by performing a protection relay operation using this digital data.
- the digital protection relay when it detects a failure section, it performs a protection operation such as tripping a circuit breaker to disconnect the failure section from the system.
- a protection operation such as tripping a circuit breaker to disconnect the failure section from the system.
- the analog input circuit of such a digital protection relay is typically composed of a transformer, an analog filter, a sample hold circuit, a multiplexer, an AD converter, and the like.
- the transformer receives an input of an electric quantity such as a voltage value and a current value of the system, and converts it into a signal level suitable for the digital protection relay.
- the analog filter removes a high-frequency noise component or the like superimposed on the input component of the commercial frequency.
- the sample hold circuit holds the signal from which unnecessary frequency components have been removed by the analog filter.
- the analog input circuit may receive an input of an electric quantity through a plurality of channels. In this case, a plurality of sets of transformers, analog filters, and sample hold circuits may be arranged.
- the multiplexer time-division multiplexes the signals of a plurality of channels output from the sample hold circuit and outputs the signals to the AD converter.
- the AD converter converts the time-division multiplexed analog signal into a digital signal.
- the analog elements constituting such an analog input circuit have individual differences, and even if the input voltage is zero due to variations in the components of the amplifier constituting the analog elements, for example, a minute value of about several mV to several tens of mV.
- a DC voltage offset voltage
- the offset voltage is superimposed on the input signal in the process in which the digital protection relay converts the electric quantity input to the analog input circuit into digital data. Therefore, in order for the digital protection relay to perform the protection relay calculation with high accuracy, it is necessary to perform the calculation after removing the offset voltage.
- Patent Document 1 As a technique for removing such an offset voltage, for example, there is JP-A-1-198213 (Patent Document 1).
- Patent Document 1 focusing on the fact that the input data is a sine wave that vibrates with a certain voltage level as a reference, digital data output by the AD converter in a sufficiently long period compared to the frequency of the power system. And a technique for calculating an average value of integration results as an offset voltage value.
- the present disclosure provides a digital protection relay that performs calculation and updating of an offset value in a relatively short period even in a period in which a frequency from a low frequency of about 5 Hz to a rated frequency changes, for example.
- the purpose is to do.
- the digital protection relay includes, as an analog input circuit, an input conversion unit that receives a signal indicating the amount of electricity in the power system as an analog signal, and an analog / digital conversion unit that converts the analog signal into a digital signal.
- the digital protection relay performs a protection operation based on the digital signal converted by the analog / digital conversion unit by the control unit.
- the control unit includes a protection calculation unit that performs a protection calculation using the offset voltage value, an acquisition unit that sequentially acquires input data converted into a digital signal by the analog / digital conversion unit according to the sampling timing, and each sampling value And an offset value calculation unit that calculates an offset voltage value based on a sampling value within a period in which the polarity of the difference amount changes among input data within at least one cycle based on the difference amount between them. .
- the offset voltage value is calculated based on the sampling value within the period in which the polarity of the difference amount of each sampling value sampled within at least one cycle changes. Therefore, the digital protection relay can calculate the offset voltage value by using a sampling value of fewer cycles such as one cycle, for example, regardless of the frequency of the input signal compared to the conventional one. For example, it can be performed in a short period of about several seconds.
- FIG. 6 is a diagram illustrating a configuration of a digital protection relay 10-2 according to a second embodiment.
- FIG. 6 is a flowchart illustrating an operation of the digital protection relay 10-2 according to the second embodiment. It is a figure which shows the relationship between the magnitude
- the analog signal input to the digital protection relay is a sine wave that oscillates with a certain voltage level as a reference.
- the digital protection relay of the related art provides a sufficiently long period compared with the frequency of the power system, accumulates the digital data of the input data, and averages the accumulated result of the accumulated digital data to obtain the offset voltage value. calculate.
- the rated frequency is 50 Hz
- the sampling frequency is 600 Hz (the sample period is an electrical angle of the rated frequency of 30 °)
- the number of samples in the integration period is the number of samples “2 16 ”
- the related art digital protection relay calculates an offset voltage value about every 109 seconds.
- the integration time when the input frequency is gradually increased from the low frequency is estimated, for example, when the input frequency is 5 Hz, it is as follows.
- the rated frequency is 50 Hz.
- Vn is a rated voltage. Since the input frequency of 5 Hz is 1/10 of the rated frequency of 50 Hz, the output of the generator is also assumed to be 1/10 of the operation at the rated frequency. In this case, since the sampling interval is also 1/10 of the rated frequency, the electrical angle is every 3 °. When the input frequency deviates from the rated frequency, an average error of maximum half-wave occurs.
- the effect of the half-wave error is 1/10 or less of the error due to voltage.
- voltage input will be performed.
- the input frequency changes over several minutes to several tens of minutes from a low frequency of, for example, about 5 Hz to a commercial rated frequency (for example, 50 Hz). Even in this case, the offset voltage value is calculated and updated in a relatively short time of about several seconds.
- FIG. 1 is a block diagram showing a configuration of a digital protection relay according to the present embodiment.
- the digital protection relay 10 collects current information and voltage information of the power system, and performs a protection relay calculation based on the collected information.
- the digital protection relay 10 includes a plurality of transformers 11-1 to 11-N (hereinafter sometimes collectively referred to as “transformers 11”) and a plurality of analog filters 12-1 to 12-12. -N (hereinafter sometimes collectively referred to as “analog filter 12”) and a plurality of sample and hold circuits 13-1 to 13-N (hereinafter sometimes collectively referred to as “sample and hold circuit 13”).
- Transformers 11 hereinafter sometimes collectively referred to as “transformers 11”
- analog filters 12-1 to 12-12. -N hereinafter sometimes collectively referred to as “analog filter 12”
- sample and hold circuit 13 sample and hold circuit 13
- Multiplexer 14 AD converter 15, operation control unit 16, D / O 17, sampling cycle control circuit 18, alarm circuit 19, trip circuit 20, ROM 21, and RAM 22.
- the power transmission line 2 is provided with a circuit breaker 9 and a current transformer (CT) 7 and an instrument transformer (PT / Voltage Transformer: VT) 8.
- CT current transformer
- VT Instrument Transformer
- the current transformer 7 measures information (current waveform) of the current flowing through the power transmission line 2.
- the instrument transformer 8 measures voltage information (voltage waveform) generated in the power transmission line 2.
- an instrument transformer may be provided for each phase in the case of three-phase alternating current.
- Information measured by each of the current transformer 7 and the instrument transformer 8 is input to the digital protection relay 10. That is, the digital protection relay 10 collects information on the current flowing through the power transmission line 2 and information on the voltage generated in the power transmission line 2.
- the digital protection relay 10 includes the transformer 11, the analog filter 12, and the sample hold circuit 13 to form an input conversion unit that receives a signal indicating the amount of electricity of the power system as an analog signal. Moreover, as shown in FIG. 1, the digital protection relay 10 receives the input of the electric quantity of a system
- the transformer 11 receives an analog signal such as current or voltage from the power system and converts it into a voltage signal suitable for the internal circuit of the digital protection relay 10.
- the analog filter 12 removes unnecessary frequency components such as a high-frequency noise component superimposed on the analog signal input from the transformer 11.
- the sample hold circuit 13 operates in accordance with the sampling control signal from the sampling cycle control circuit 18, receives and holds the signal input from the analog filter 12, and outputs the held signal to the multiplexer 14.
- the multiplexer 14 time-divides the N channel signals output from the sample hold circuit 13 and sequentially outputs them to the AD converter 15.
- the multiplexer 14 operates in accordance with the sampling control signal from the sampling period control circuit 18, selects signals extracted from the sample hold circuit 13 at a predetermined sampling period in order of channels, and outputs them to the AD converter 15.
- the AD converter 15 converts N analog input signals sequentially output in a time-division manner by the multiplexer 14 into digital data in order.
- the calculation control unit 16 is a processor for controlling the protection calculation by the digital protection relay 10, and is configured by a CPU (Central Processing Unit) or the like.
- the calculation control unit 16 operates as a protection calculation unit 61, an input data acquisition unit 62, a difference amount calculation unit 63, a maximum / minimum value selection unit 64, and an offset value calculation unit 65 by operating according to a program stored in the ROM 21 or the like. Demonstrate the function.
- the protection calculation unit 61 exhibits a function of executing a protection calculation based on information on the amount of electricity of the power transmission line 2 using the digital data output from the AD converter 15.
- the protection calculation unit 61 performs a protection calculation using the offset value 74.
- the input data acquisition unit 62 sequentially acquires the input data converted into a digital signal by the AD converter 15 according to the timing indicated by the sampling control signal output from the sampling cycle control circuit 18, and the acquired input data is input data.
- the function to be held in the RAM 22 as 71 is exhibited.
- the difference amount calculation unit 63 exhibits a function of calculating a difference amount of values (for example, voltage values) at each sampling timing based on the input data 71. For example, the difference amount calculation unit 63 calculates the difference amount of the value at each sampling timing by comparing the instantaneous value at each sampling timing with the instantaneous value before one sample. The difference amount calculation unit 63 exhibits a function of causing the RAM 22 to store the calculation result as difference data 72.
- a difference amount of values for example, voltage values
- the maximum value / minimum value selection unit 64 selects, based on the difference data 72, the instantaneous value that becomes the maximum value and the instantaneous value that becomes the minimum value among the input data of each cycle.
- the maximum value / minimum value selection unit 64 specifies an extreme point where the polarity of the input data changes based on the amount of change in the difference between the sampling values at each sampling timing, and determines the maximum value as the input data in one cycle.
- the minimum value is selected as the minimum value of the input data within one cycle.
- the maximum value / minimum value selection unit 64 stores the maximum value and the sampling value of the minimum value selected in each cycle in this manner in the RAM 22 as the maximum value / minimum value 73.
- the offset value calculation unit 65 calculates the offset voltage value based on the maximum value and the minimum value of the sampling values in each cycle. For example, the offset value calculation unit 65 uses the average value of the maximum value and the average value of the minimum value of each cycle of the sampling value to calculate the average of the average value of the maximum value and the average value of the minimum value as the offset voltage value. And the calculated value is stored in the RAM 22 as the offset value 74.
- the D / O 17 outputs the result of the protection calculation by the calculation control unit 16 to the outside of the digital protection relay 10.
- Protection relay such as operating the circuit breaker 9 by outputting a trip command from the D / O 17 to the trip circuit 20 when the operation control unit 16 monitors the state of the power system by a protection operation and detects the occurrence of an accident or the like. Perform the operation.
- the output relay of the alarm circuit 19 is operated from the D / O 17, and the device outside the digital protection relay 10 is Notifies the abnormality of the digital protection relay 10.
- the sampling cycle control circuit 18 outputs a sampling control signal to the sample hold circuit 13, the multiplexer 14, the AD converter 15 and the calculation control unit 16 according to the sampling cycle, and converts the analog signal into digital data and performs calculation control.
- the timing of the protection calculation by the unit 16 is controlled.
- the ROM 21 is a nonvolatile storage device and stores various programs such as a program for operating the digital protection relay 10 and data.
- the RAM 22 is a volatile storage device, and provides a work area for storing data necessary for the execution of the program in the arithmetic control unit 16.
- FIG. 2 is a diagram illustrating an AC input of current or voltage received by the digital protection relay 10 and a sampling timing.
- the AC input of the rated frequency and the sampling frequency being 12 times the rated frequency are shown.
- FIG. 2 the vertical broken line indicates the sampling timing. Further, FIG. 2 shows that there is an offset voltage on the plus voltage side from 0 V of the circuit of the digital protection relay 10.
- FIG. 3 shows a period in which the polarity of the difference value ⁇ V (t) of the input data changes at each sampling timing.
- an upward arrow is shown when the difference value ⁇ V (t) at each sampling timing of the input data is positive, and a downward arrow is shown when the difference value ⁇ V (t) is negative. Yes.
- the difference value ⁇ V (t) is defined as follows, for example.
- V (t) represents an instantaneous value at the sampling time t
- V (t ⁇ 1) represents an instantaneous value one sample before.
- the instantaneous value before one sample is used to calculate the difference value.
- the present invention is not limited to this, and the instantaneous value before a plurality of samples is used according to the input frequency or sampling frequency.
- the difference value ⁇ V (t) may be calculated.
- the digital protection relay 10 stops the determination of the maximum value and the minimum value of each sampling value, and continues to use the offset value used before the failure determination. use. Further, the digital protection relay 10 determines that the input is an abnormal input when the period during which the maximum value and the minimum value of the sampling value are not calculated continues for a certain period or longer, and the alarm circuit 19 issues an alarm outside the digital protection relay 10. Output to the device.
- FIG. 4 is a flowchart showing offset value correction processing by the digital protection relay 10.
- step S401 the arithmetic control unit 16 of the digital protection relay 10 reads input data (V (t), V (t-1),...) Converted into digital data by the AD converter 15.
- the difference value ⁇ V (t) of the sampling values is calculated using the instantaneous value one sample before, and input data of a plurality of cycles is read in step S401.
- step S411 the arithmetic control unit 16 calculates the change amount of the difference value ⁇ V (t) based on the calculation result of the difference value ⁇ V (t) at each sampling timing, and the change amount is from plus to minus or from minus. Identify sampling values that change to positive.
- the arithmetic control unit 16 detects the maximum value and the minimum value of the sampling value in one cycle by specifying the sampling value at the timing when the polarity of the difference amount changes. This process will be described later with reference to FIG.
- step S413 it is determined whether both the maximum value and the minimum value of the sampling values are detected. If both the maximum value and the minimum value are detected, the process proceeds to step S417 (YES in step S413). If not (NO in step S413), the process of step S405 is performed.
- step S417 the arithmetic control unit 16 stores the maximum value and the minimum value of the sampling values in each cycle in the RAM 22 as the maximum value / minimum value 73.
- step S421 the arithmetic control unit 16 determines whether or not both the maximum number of sampling values and the minimum number of accumulations are accumulated at a predetermined number (K) or more, and a predetermined number or more are accumulated. If so (YES in step S421), the process of step S425 is performed. If not (NO in step S421), the process of step S401 is performed.
- step S425 the arithmetic control unit 16 obtains the average of the maximum values of the sampling values and the average of the minimum values, adds the average of these maximum values and the average of the minimum values, and divides by 2 (averages). ) To calculate the offset value and store it in the RAM 22 as the offset value 74. This offset value is used for the protection calculation of the calculation control unit 16 until the next offset value is calculated.
- step S429 the arithmetic control unit 16 clears the maximum value and the minimum value of each cycle stored in 73, and performs the process of step S401.
- step S411 will be described in detail.
- FIG. 5 is a diagram showing a process for detecting the maximum value and the minimum value from the sampling value.
- the arithmetic control unit 16 When the logical product 101 of the condition C1 and the condition C2 is established for the input data read in step S401, the arithmetic control unit 16 indicates that the signal A indicates that the voltage value V (t ⁇ 3) is the maximum value. Is output.
- the arithmetic control unit 16 When the logical product 102 of the condition C3 and the condition C4 is established, the arithmetic control unit 16 outputs a signal B indicating that the voltage value V (t ⁇ 3) is the minimum value.
- the arithmetic control unit 16 When the logical product 103 of the condition C1 and the condition C5 is established, the arithmetic control unit 16 outputs a signal C indicating the maximum value when the AC signal as input data is minute or zero input.
- the arithmetic control unit 16 When the logical product 104 of the condition C3 and the condition C5 is established, the arithmetic control unit 16 outputs a signal D indicating the minimum value when the AC signal as input data is minute or zero input.
- the condition C5 indicates that the absolute value of the difference value of the sampling values is a constant value ⁇ 1 over a plurality of samples.
- This constant value ⁇ 1 is a data fluctuation when the input data is zero input. It is set to a value larger than the difference value of each sampling value by. By doing so, it is determined whether the AC signal as input data is minute or zero input.
- Condition C6 indicates that a system failure has been detected.
- the arithmetic control unit 16 determines the maximum value (voltage value V (t ⁇ 3 )) Is detected.
- the arithmetic control unit 16 determines the minimum value (voltage value V (t ⁇ 3 )) Is detected.
- FIG. 6 is a diagram showing an example of sampling in the case of a low frequency.
- the rated frequency is 50 Hz
- the frequency of the low-frequency AC input is 5 Hz.
- the arithmetic control unit 16 can detect the maximum value and the minimum value of the sampling value by the operation of FIG. 4 and FIG. 5, and calculates the offset value by using the maximum value and the minimum value. be able to.
- FIG. 7 is a diagram illustrating a configuration of the digital protection relay 10-2 according to the second embodiment.
- the arithmetic control unit 16 includes a frequency determination unit 66, and whether the frequency of the input data is the rated frequency or below a certain frequency lower than the rated frequency.
- the time interval between the sampling values for calculating the difference amount of the sampling values is controlled according to the determination result. For example, when it is determined that the frequency is a low frequency, the arithmetic control unit 16 calculates the change amount of the difference amount by increasing the time interval between the sampling values for calculating the difference amount.
- the sampling electrical angle is 3 ° when the AC input is 5 Hz, and the difference between the sampling values is small. For this reason, a highly accurate calculation is required. Therefore, when the frequency of the AC input is lowered, the sampling value for calculating the difference amount is set to a plurality of previous sampling values, thereby eliminating the need for highly accurate calculation.
- FIG. 8 is a flowchart showing the operation of the digital protection relay 10-2 of the second embodiment.
- ⁇ Vf (t) V (t) ⁇ V (t ⁇ 2) indicates that the difference value is calculated by comparing the sampling value with the sampling value two samples before.
- step S407 the arithmetic control unit 16 determines whether or not the frequency of the AC input is a low frequency depending on whether or not
- FIG. 9 is a diagram showing the relationship between the magnitude of the difference between sampling values and the electrical angle. As shown in FIG. 9, when the rated frequency is 50 Hz,
- step S409 in order to calculate the difference amount of the sampling value, the calculation control unit 16 calculates the difference amount by making the value g larger than 1 and comparing it with the sampling value before g samples.
- the maximum value that the value g can take is 3.
- the arithmetic control unit 16 uses ⁇ V (t) to ⁇ V (t ⁇ 5 ⁇ 3) as ⁇ V. Therefore, in the determination process of FIG. 10, V (t) to V (t ⁇ 6 ⁇ 3) are used as the input data V.
- the arithmetic control unit 16 uses the instantaneous value before 18 samples.
- the calculation control unit 16 calculates the difference from the data before the electrical angle 155 ° as a difference amount. ing. That is, the difference is calculated for data with an electrical angle within 180 °.
- step S411 the arithmetic control unit 16 detects the maximum value and the minimum value of the sampling values according to the conditions shown in FIG.
- FIG. 10 is a diagram illustrating a process for detecting the maximum value and the minimum value from the sampling values.
- Embodiment 2 As described above, when the frequency input to the digital protection relay 10-2 is a low frequency band, the time difference of the sampling data used for the difference calculation of the sampling value is widened, thereby improving the operation reliability in the low frequency band. Can be increased. In Embodiment 2, the frequency band close to the rated frequency and the low frequency band are separated, but the frequency band may be further separated. Thereby, the reliability of the operation of the digital protection relay 10-2 can be improved.
Abstract
Description
まず、本実施形態のデジタル保護リレーと比較するため、関連技術におけるデジタル保護リレーのオフセット値算出に要する期間の一例を説明する。
ここで、Vnは、定格電圧である。入力周波数5Hzは、定格周波数50Hzの1/10であるため、発電機の出力も定格周波数による運転時の1/10と仮定している。この場合、サンプリング間隔も、定格周波数の場合の1/10となるので、電気角3°ごととなる。入力周波数が定格周波数からずれることにより、最大半波の平均誤差が生じる。
交流電圧の半サイクルの積算値=(1/10)Vn√2(sin3 + sin6 +…+sin177)=5.39Vn (サンプリングのための電気角を、0°、3°、6°、・・・177°とする)
となる。
(交流電圧の半サイクルの積算値)/(積算されるデータ数)=0.00899Vn
となる。すなわち、1ビットにつき、上記の電圧に相当する誤差が生じる。この誤差を、回路電圧に換算すると、回路電圧を10V、アナログ回路のダイナミックレンジを2倍とすると、
1ビットの誤差に相当する電圧:(10V/2Vn)×0.00899Vn=45mV
となる。
AD変換後の1ビットの量子化誤差=10V/215=0.3mV
となる。この1ビットの誤差に相当する電圧(45mV)を、1ビットの量子化誤差(0.3mV)程度とするには、
積算期間=45mV/0.3mV=150秒
の積算期間を必要とする。したがって、上記の半波誤差を無視できる水準とするには、数分の長い積算期間を必要とする。
まず、実施の形態1に従うデジタル保護リレーの構成について説明する。
図2は、デジタル保護リレー10が受け付ける電流または電圧の交流入力とサンプリングのタイミングとを示す図である。図2の例では、定格周波数の交流入力と、サンプリング周波数が定格周波数の12倍であることとを示している。
ここで、V(t)は、サンプリングの時刻tにおける瞬時値を示し、V(t-1)は、1サンプル前の瞬時値を示す。なお、差分値を算出するため、この例では、1サンプル前の瞬時値を使用しているが、これに限らず、入力周波数やサンプリング周波数に応じて、複数サンプル前の瞬時値を使用して差分値ΔV(t)を算出してもよい。
また、V(t)が最小値の場合は、以下の条件が成立する。
また、交流入力が零の場合は、オフセット電圧のみの入力データとなる。この場合、入力データの最大値と最小値は、ほぼ同一の値となり、上記の条件は成立しない。この場合、入力データの各サンプリングのタイミングにおける差分値が一定値以内となる。
図4は、デジタル保護リレー10によるオフセット値の補正処理を示すフローチャートである。
実施の形態1のデジタル保護リレー10において、低周波の入力信号を受け付けた場合のサンプリングの例と、オフセット値の算出とを説明する。
次に、実施の形態2のデジタル保護リレー10-2について説明する。
図8は、実施の形態2のデジタル保護リレー10-2の動作を示すフローチャートである。
|ΔVf(t)|/|V(t)|=1
(2)低周波数の場合(周波数f=fn/h)(関係409):
|ΔVf(t)|/|V(t)|=2sin(30/h)
ここで、例えば、|ΔVf(t)|/|V(t)|=0.3の場合、h=3.5、すなわち定格周波数50Hzに対して低周波の周波数は14.4Hzとなる。
以上のように、デジタル保護リレー10-2に入力される周波数が低い周波数帯である場合は、サンプリング値の差分演算に用いるサンプリングデータの時間差を拡げ、これにより、低周波数帯における動作の信頼性を高めることができる。実施の形態2では、定格周波数に近い周波数帯と、低周波数帯との2つに分離しているが、さらに周波数帯を分離してもよい。これにより、デジタル保護リレー10-2の動作の信頼性を高めることができる。
Claims (7)
- デジタル保護リレーであって、
電力系統の電気量を示す信号をアナログ信号として受け付ける入力変換部と、
前記アナログ信号をデジタル信号に変換するアナログ/デジタル変換部と、
前記デジタル信号に基づいて保護演算を実行する制御部とを備え、
前記制御部は、
オフセット電圧値を用いて前記保護演算を実行する保護演算部と、
前記アナログ/デジタル変換部によりデジタル信号に変換される入力データを、サンプリングのタイミングに従って逐次取得する取得部と、
各サンプリング値間の差分量に基づいて、少なくとも1サイクル内の前記入力データのうち前記差分量の極性が変化する期間内のサンプリング値に基づいて前記オフセット電圧値を算出するオフセット値算出部とを含む、デジタル保護リレー。 - 制御部は、前記差分量の変化量に基づいて前記入力データの極値点を特定することで、前記少なくとも1サイクル内の入力データのうち最大値となるサンプリング値と、最小値となるサンプリング値とを選択する選択部を含み、
前記オフセット値算出部は、前記最大値となるサンプリング値と前記最小値となるサンプリング値とに基づいて前記オフセット電圧値を算出する、請求項1に記載のデジタル保護リレー。 - 前記オフセット値算出部は、前記最大値となるサンプリング値と前記最小値となるサンプリング値との平均値を前記オフセット電圧値として算出する、請求項2に記載のデジタル保護リレー。
- 前記選択部は、複数サイクルの前記入力データのうち、各サイクルについて前記最大値となるサンプリング値と前記最小値となるサンプリング値とを選択し、
前記オフセット電圧値は、前記各サイクルについての前記最大値となるサンプリング値の平均と、前記各サイクルについての前記最小値となるサンプリング値の平均とに基づき、前記オフセット電圧値を算出する、請求項2に記載のデジタル保護リレー。 - 前記制御部は、最大値となるサンプリング値の検出がない期間、および、最小値となるサンプリング値の検出がない期間の少なくともいずれかが一定期間に達する場合に、警報を出力するよう構成されている、請求項1に記載のデジタル保護リレー。
- 前記選択部は、前記入力データが零入力であることまたは微小な交流入力であることを、前記差分量の変化量の絶対値に基づいて検知し、前記零入力または前記微小な交流入力である場合に、サンプリングのタイミングそれぞれにおける前記サンプリング値の大小を比較することにより、前記最大値となるサンプリング値と前記最小値となるサンプリング値とを選択する、請求項2に記載のデジタル保護リレー。
- 前記制御部は、前記入力データの周波数が定格周波数であるか、前記定格周波数より低い周波数であるかを判定する周波数判定部と、
前記周波数の判定結果に応じて、前記サンプリング値間の差分量を算出するためのサンプリング値の時間間隔を制御して前記差分量の変化量を算出する差分量算出部とを含む、請求項1に記載のデジタル保護リレー。
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PCT/JP2014/065781 WO2015189996A1 (ja) | 2014-06-13 | 2014-06-13 | デジタル保護リレー |
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KR101886362B1 (ko) * | 2017-05-19 | 2018-08-09 | 주식회사 동운아나텍 | 카메라 모듈용 액츄에이터 이동감지 소자와 그들을 포함하는 카메라 모듈용 유연성 회로기판 |
EP3850375A4 (en) * | 2018-09-11 | 2022-06-15 | Nalu Scientific, LLC | SYSTEM AND METHOD FOR HIGH SAMPLING RATE TRANSIENT DATA ACQUISITION WITH PRE-CONVERSION ACTIVITY DETECTION |
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