JP4841511B2 - Frequency change rate protection relay device - Google Patents

Description

  The present invention relates to a system stabilizing device, and particularly to a frequency change rate protection relay device.

  In the system stabilization device, when the cutoff command is issued from the central control device to the load control terminal, the load control terminal requires that the frequency change rate of its own end exceed a certain threshold (referred to as 95D) condition (FS). As widely used.

JP 2004-361124 A (frequency measuring device)

  Moreover, in the frequency change rate protection relay device generally incorporated in the system stabilization device, the zero cross method is used as a frequency change rate measurement method. The zero cross method is a method of detecting the time width between two adjacent zero crosses that cross the zero level in the same direction as one period of the fundamental frequency. However, this zero cross method has a drawback that it is easily affected by harmonic components and noise components. In particular, when a sudden voltage phase change (voltage flicker) occurs, a large fluctuation occurs in the frequency change rate detection value, so that 95D malfunctions tend to occur frequently. Therefore, the development of a frequency change rate protection relay device that monitors the frequency change rate without being affected by the sudden phase change (voltage flicker) that appears in real time in the power system and protects the electric system has been a problem.

  The present invention has been made in view of the above, and has a frequency change rate protection relay that protects a power system with high accuracy and stability without being affected by a sudden phase change (voltage flicker) that appears in real time in the power system. The object is to obtain a device.

  In order to achieve the above-described object, the frequency change rate protection relay device according to the present invention is the instantaneous voltage of the power system acquired at each sample timing obtained by equally dividing one period of the reference wave by 4N (N is a positive integer). A voltage amplitude calculation unit that calculates an amplitude value of a voltage rotation vector expressed on a complex plane using value sampling data by an integration operation using voltage instantaneous value sampling data in one cycle of the reference wave; and the voltage amplitude calculation This is an interval between the voltage amplitude average value calculation unit that averages the voltage amplitude value calculated by the unit by performing a moving average process over a period of one cycle or more of the reference wave, and the tip of two adjacent voltage rotation vectors. A chord length calculation unit that calculates a chord length by an integration operation using sampling voltage instantaneous value voltage data in one cycle of the reference wave, and a chord length calculated by the chord length calculation unit is equal to or less than one cycle of the reference wave. A chord length average value calculating unit that averages by performing a moving average process over a period of time, a voltage amplitude average value calculated by the voltage amplitude average value calculating unit, and a chord length average value calculated by the chord length average value calculating unit The rotation phase angle calculation unit that calculates the rotation phase angle of the voltage rotation vector using the and the rotation phase angle calculated by the rotation phase angle calculation unit performs a moving average process over a period of one cycle or more of the reference wave A rotation phase angle average value calculation unit that averages the frequency, a frequency calculation unit that calculates the frequency of the system using the frequency of the reference wave and the rotation phase angle average value calculated by the rotation phase angle average value calculation unit, A frequency change instantaneous value calculation unit that calculates an instantaneous value of a frequency change that is a difference between two frequencies at each of two sample timings separated by a certain period, and the frequency change is divided by the time between sample timings. A frequency change rate instantaneous value calculation unit for obtaining an instantaneous value of the frequency change rate and a frequency acceleration mode in which the instantaneous value of the frequency change is compared with a predetermined first threshold and the frequency change is in an increasing state. A frequency change mode determination unit for determining whether the frequency change mode is in a state where the frequency change is decreasing, and whether the frequency change mode is a latch mode that does not correspond to either the frequency acceleration mode or the frequency reduction mode, and the frequency change According to the determination result of the mode determination unit, the instantaneous value of the frequency change rate is compared with a predetermined second threshold value to determine whether the frequency change rate in the frequency acceleration mode is in an increasing state or not. Whether or not the rate of change is in a decreasing state and whether it falls under any of these states are determined, and information on the determination result is quantified. And a protection command for the power system is output based on a comparison result obtained by comparing the count value quantified by the counter unit with a predetermined third threshold value. To do.

  According to the present invention, the amplitude value of the voltage rotation vector is calculated by the integration method, and is averaged. In addition, the chord length between adjacent voltage rotation vector tips is calculated by an integration method and is averaged. Then, the rotational phase angle is obtained from the voltage amplitude average value and the chord length average value, and is subjected to a moving average, and the frequency is calculated using the moving averaged rotational phase angle average value and the frequency of the reference wave. For the frequency thus determined, the instantaneous value of the frequency change is compared with a predetermined first threshold value, and the frequency change mode in which the frequency change is in the increasing state or the frequency in which the frequency change is in the decreasing state It is determined whether the mode is a deceleration mode and whether the latch mode does not correspond to either the frequency acceleration mode or the frequency deceleration mode. Further, according to these determination results, the instantaneous value of the frequency change rate is compared with a predetermined second threshold value to determine whether the frequency change rate in the frequency acceleration mode is in an increasing state or not. It is determined whether or not the rate is in a decreasing state and whether it falls into any of these states. Furthermore, it is determined whether or not to output a protection command for the power system based on a comparison result obtained by comparing the count value counted for quantifying the information of these determination results with a predetermined third threshold value. As a result, it is possible to obtain a frequency change rate protection relay device that protects the power system with high accuracy and stability without being affected by a sudden phase change (voltage flicker) that appears in real time in the power system. .

  The present inventor previously called a “frequency measurement device” (see the invention of the above “Patent Document 1”, hereinafter referred to as “conventional invention”), which can measure the frequency of the power system at high speed in a power system with a lot of noise or the like before A “frequency change measuring device, frequency change rate measuring device, and power system control protection device” that can obtain a frequency change and frequency change rate detection method that is not affected by sudden phase change (voltage flicker) has been proposed. On the other hand, in this specification, a part of the frequency measurement method in the proposed “frequency change measuring device, frequency change rate measuring device, and power system control protection device” is used, and the frequency change rate and the threshold are compared. A frequency change rate protection relay device incorporating a probabilistic method in part is disclosed. Therefore, an outline of “frequency measuring device” and “frequency change measuring device, frequency change rate measuring device and power system control protection device” (hereinafter referred to as “prior application invention”) will be described first.

  The conventional invention expresses an AC voltage as a voltage vector that rotates counterclockwise on a complex plane. The voltage vector on the complex plane where the voltage value at the preceding measurement point of the two measurement points is the imaginary part of the complex coordinates and the voltage value at the subsequent measurement point is the real part of the complex coordinates is At the same time, it rotates counterclockwise on the complex plane. In the conventional invention, the chord length, which is the distance between the tips of two adjacent voltage rotation vectors, is calculated, and one period is added. Further, the effective voltage value is obtained from the measured voltage at each measurement point in one cycle. Then, the phase angle of the voltage vector is calculated from the effective values of both voltages at one measurement point around one cycle and the added value of the chord length, and the frequency of the power system is obtained. The present inventors refer to the frequency thus obtained as a static frequency. This static frequency measurement method is a highly accurate and stable measurement method that can eliminate the effects of system noise and harmonics, but it cannot completely prevent 95D malfunction due to voltage flicker accompanied by large phase fluctuations. There were drawbacks.

  On the other hand, the power system control protection device according to the invention of the prior application expresses the AC voltage as a voltage vector that rotates counterclockwise on the complex plane in the same way as the AC voltage expression method according to the conventional invention. The amplitude value of the voltage rotation vector is calculated by an integration method, and is averaged by moving. In addition, the chord length between adjacent voltage rotation vector tips is calculated using an integration method, and is averaged. Then, the rotational phase angle is obtained from the voltage amplitude average value and the chord length average value, and is subjected to moving average, and the frequency that is not affected by the sudden phase change is obtained by using the moving average rotational phase angle average value and the reference wave frequency. calculate.

  The frequency change calculated by taking the difference between the frequency and the frequency several steps before is also moving averaged to obtain the frequency change average value. Then, the frequency change average value is divided by the elapsed time to obtain the frequency change rate average value. Furthermore, this frequency change rate average value is compared with a certain threshold value, and when the frequency change rate average value exceeds the threshold value, a command for protecting the electrical system is output. With respect to this apparatus, a voltage frequency of 60 Hz was input, and a phase fluctuation of 0.5 degrees (0.00872655 radians) simulating voltage flicker was inserted when 0.168055556 seconds passed, and the simulation results are shown in FIGS. As shown in FIG.

  FIG. 9 shows the measured frequency. This shows that the frequency fluctuates greatly due to voltage flicker. FIG. 10 is a diagram showing the frequency change average value 14 and the frequency change instantaneous value 15. The fluctuation range of the frequency change average value 14 is smaller than the fluctuation range of the frequency change instantaneous value 15. Yes. FIG. 11 shows an average frequency change rate value 17 and an instantaneous value 18 of the frequency change rate. The positive frequency change rate starting threshold value 16a is set to +0.5 Hz / s, and the negative frequency change rate is set. When the activation threshold value 16b is set to -0.5 Hz / s, the fluctuation range of the frequency change rate average value 17 is small enough to be within the range of the frequency change rate activation threshold value. This indicates that there is no 95D malfunction due to a sudden phase change simulating the current voltage flicker. The frequency change rate instantaneous value 18 shown in FIG. 11 is calculated for comparison, but fluctuates greatly exceeding the frequency change rate starting threshold value. This indicates that there is a 95D malfunction due to a sudden phase change simulating voltage flicker. As described above, in the conventional invention, by improving the method of measuring the static frequency and calculating the frequency change and the frequency change rate, the effect of removing the influence of noise and harmonics can be obtained. The effect of avoiding 95D malfunction due to voltage flicker was obtained.

  By the way, even when the frequency measurement method according to the invention of the prior application is used, the inventor has greatly improved the measurement accuracy as compared with the case where the conventionally used zero cross method is used. I found a phenomenon that the measured value was not obtained. Actual frequency measurements varied with a certain degree of randomness. This phenomenon is partly due to the uncertainty principle.

  The present invention treats a frequency measurement value in which variation (noise) occurs with a certain randomness as described above, not a method of moving and averaging the frequency change amount and the frequency change rate with a threshold value, but probabilistically. The frequency change rate protection relay device eliminates the influence on the frequency change rate measurement result due to noise generated in the frequency measurement value by adopting a method of comparing with the threshold value. Hereinafter, specific embodiments will be described. Note that the present invention is not limited to the embodiments.

  First, the configuration of the frequency change rate protection relay device according to the present invention will be described. FIG. 1 is a configuration diagram of a frequency change rate protection relay device according to the present embodiment. In FIG. 1, a frequency change rate protection relay device 1 according to this embodiment includes a voltage / current measurement unit 2, an A / D conversion unit 3, a voltage amplitude and moving average value calculation unit 4, a chord length and The moving average value calculation unit 5, the rotational phase angle and moving average value calculation unit 6, the frequency calculation unit 7, the frequency change rate instantaneous value calculation unit 8, the frequency change mode determination unit 9, and the frequency acceleration / deceleration A counter unit 10, an interface 11, a power system protection command output unit 12, and a storage unit 13 are provided.

  Next, the function of each component of the frequency change rate protection relay device according to the present invention will be described.

  The voltage / current measuring unit 2 measures a system voltage using a PT (instrument transformer) attached to the transmission line of the power system 14 or a CT (not shown) attached to the transmission line of the power system 14. System current is measured using a current transformer and converted to system voltage.

  The A / D conversion unit 3 samples the system voltage signal from the voltage / current measurement unit 2 at each sample timing obtained by equally dividing one period of the reference wave by 4N (N is a positive integer), and time-series digital data Convert to (Voltage instantaneous value data). Time-series voltage instantaneous value data converted over a plurality of cycles of the reference wave is stored in the storage unit 13.

  The voltage amplitude and moving average value calculation unit 4 first takes out voltage instantaneous value data for one cycle from the storage unit 13, and uses the voltage instantaneous value data to calculate the amplitude value of the voltage rotation vector represented on the complex plane. Then, the integration calculation using the voltage instantaneous value data for one period is performed, and the calculation is stored in the storage unit 13 one by one. Then, a voltage amplitude calculation result of one cycle or more is taken out from the storage unit 13, a moving average process is performed, the voltage amplitude value is averaged, and stored in the storage unit 13 one by one.

  The chord length and its moving average value calculation unit 5 first integrates the chord length, which is the interval between the tips of two adjacent voltage rotation vectors, using the voltage instantaneous value data for one cycle extracted from the storage unit 13. Calculations are made by performing calculations and stored in the storage unit 13 one by one. Then, a chord length calculation result of one period or more is taken out from the storage unit 13, a moving average process is performed, the chord lengths are averaged, and stored in the storage unit 13 one by one.

  The rotation phase angle and its moving average value calculation unit 6 first takes out the averaged voltage amplitude value and chord length from the storage unit 13 to calculate the rotation phase angle, and stores it in the storage unit 13 one by one. Then, a rotational phase angle calculation result of one cycle or more is extracted from the storage unit 13, a moving average process is performed, the rotational phase angle is averaged, and stored in the storage unit 13 one by one.

  The frequency calculation unit 7 extracts the rotation phase angle average value from the storage unit 13, calculates the frequency, and stores it in the storage unit 13 one by one. Here, when there is an influence such as sudden phase change (voltage flicker), there is a certain error in the static frequency calculated using the rotational phase angle. Thus, the error is reduced by avoiding the influence of a sudden phase change (voltage flicker) or the like.

  The frequency change rate instantaneous value calculation unit 8 extracts the current frequency and the frequency before a certain time (mT: m is a specified positive integer, T is a sampling interval) from the storage unit 13, and divides the difference by the time interval. The calculated frequency change rate instantaneous value is stored in the storage unit 13 one by one.

  The frequency change mode determination unit 9 extracts a past frequency including the current frequency, the frequency one step before, and the frequency two steps before from the storage unit 13, takes the difference, and compares it with a certain threshold value. Thus, it is determined whether the frequency change mode, that is, the change in the system frequency is an increase state, a decrease state, or a state in which neither the increase state nor the decrease deceleration state is present, and the determined frequency change mode is stored in the storage unit 13 one by one.

  The frequency acceleration / deceleration counter unit 10 takes out the instantaneous value of the frequency change mode and the frequency change rate from the storage unit 13 and determines the threshold value of the instantaneous value of the frequency change rate according to the frequency change mode. It is determined whether the state is an increase state, a decrease state, or a state that is neither an increase state nor a decrease state, and an acceleration counter provided in the frequency acceleration / deceleration counter unit 10 is added or subtracted according to the state of these determination results. Alternatively, a deceleration counter provided in the frequency acceleration / deceleration counter unit 10 is added or subtracted. Each count value by the acceleration / deceleration counter is stored in the storage unit 13 one by one.

  The interface 11 takes out the frequency, the frequency change rate instantaneous value, and the acceleration / deceleration counter or some of them from the storage unit 13 and displays them.

  The power system protection command output unit 12 extracts each count value by the acceleration / deceleration counter from the storage unit 13 and compares it with a certain threshold value. When the count value of the acceleration counter or the count value of the deceleration counter reaches any one of the threshold values, a cutoff command is output to the circuit breaker shown in FIG.

  The storage unit 13 is realized by the CPU, for example, the voltage amplitude and the moving average value calculation unit 4, the chord length and the moving average value calculation unit 5, the rotation phase angle and the moving average value calculation unit 6, and the frequency calculation unit. 7. Frequency change rate instantaneous value calculation unit 8, frequency change mode determination unit 9, frequency acceleration / deceleration counter unit 10, interface 11, ROM for storing each program of power system protection command output unit 12, instantaneous voltage of power system It is composed of a RAM that stores value time-series digital data and the calculation results of the above-described units.

  Although FIG. 1 shows a configuration in which the voltage instantaneous value time-series digital data of the power system is acquired using the voltage / current measuring unit 2 and the A / D conversion unit 3 and stored in the storage unit 13, When the value time-series digital data can be obtained from another route and stored in the storage unit 13, the voltage / current measurement unit 2 and the A / D conversion unit 3 can be omitted.

  Next, the operation of the frequency change rate protection relay device according to the embodiment of the present invention will be described. FIG. 2 shows a flowchart for explaining the operation of the frequency change rate protection relay device. The calculation formulas for the following steps will be described.

  In FIG. 2, in step 101, the voltage / current measurement unit 2 and the A / D conversion unit 3 acquire voltage instantaneous value time-series digital data of the power system. The input voltage for frequency measurement includes a phase voltage (A phase voltage, B phase voltage, or C phase voltage), or a line voltage (AB line voltage, BC line voltage, AC line) Any one of the line voltages) can be used. That is, the input voltage for frequency measurement used here is a one-phase voltage or one line voltage. The instantaneous voltage v of the AC circuit can be expressed by the following equation (1) according to Fourier transform.

  Where V is the fundamental wave voltage amplitude, ω is the fundamental wave angular velocity, φ is the fundamental wave voltage initial phase, Vk is the kth harmonic voltage amplitude, ωk is the kth harmonic voltage angular velocity, and φk is the kth harmonic voltage initial. The phase M is a positive integer having an arbitrary size. That is, the voltage instantaneous value is composed of a voltage fundamental wave component and a plurality of voltage harmonic components. In the following formula expansion, voltage harmonic components are omitted for the sake of simplicity. This does not mean that the voltage harmonic component is ignored. In the present invention, the influence of the harmonic can be removed by the integral calculation method.

The voltage rotation vector is a complex in which the preceding voltage instantaneous value is expressed as an imaginary part of complex coordinates and the subsequent voltage instantaneous value is expressed as a real part of complex coordinates among the voltage instantaneous values obtained at two adjacent sample points. It is a voltage vector on the plane, and rotates counterclockwise on the complex plane with the passage of time of the sample points. The real part v _re and the imaginary part vim of this voltage rotation vector can be expressed by the following equation (2). Note that the voltage instantaneous value v used in the following equations indicates the real part v _re of this voltage rotation vector.

In step 102, the voltage amplitude and its moving average value calculation unit 4 calculates the voltage amplitude value of the voltage rotation vector and its moving average value. First, the voltage amplitude value V (t) of the theoretical voltage rotation vector is obtained by dividing one cycle T ₀ of the reference wave into 4N (N is a positive integer) equally in the following equation (3) using an integration method. It can be obtained by applying each voltage instantaneous value v (t) measured at the sample point. One cycle T ₀ is, for example, T ₀ = 1/60 = 0.0166667 seconds in a power system with a reference frequency of 60 Hz.

  However, in this embodiment, in order to improve the calculation accuracy at the system frequency that may deviate from the reference frequency, the frequency fluctuation is affected by the following expression (4) using an integration method instead of the expression (3). The voltage amplitude value V (t) not to be calculated is calculated.

  Next, the voltage amplitude value V (t) obtained by the equation (4) is averaged using the following equation (5) by the moving average method. Equation (5) represents a moving average of one cycle, but the fluctuation also decreases as the number of cycles for moving average increases.

In step 103, the chord length and its moving average value calculation unit 5 calculates a chord length V2 (t) between adjacent voltage rotation vector tips and its moving average value _V2ave . The chord length V2 (t) between adjacent voltage rotation vector tips is theoretically obtained by calculating the following equation (6) using an integration method.

  However, in this embodiment, in order to improve the calculation accuracy at the system frequency that may deviate from the reference frequency, the frequency fluctuation is affected by the following equation (7) using an integration method instead of the equation (6). The chord length V2 (t) not calculated is calculated.

  Here, v2 = v (t) −v (t−T). Next, the chord length V2 (t) obtained by the equation (7) is averaged using the following equation (8) by the moving average method. Equation (8) represents a moving average of one cycle, but as the number of cycles taking the moving average increases, the fluctuation also decreases.

In step 104, the rotation phase angle and its moving average value calculation unit 6 determines the rotation phase angle δ (t) that is an electrical angle at which the voltage rotation vector rotates in one cycle of the reference wave and its moving average value δ _ave (t). And calculate. The rotational phase angle δ (t) is obtained by the following equation (9), and the moving average value δ _ave (t) is obtained by the following equation (10). In addition, although Formula (10) shows the moving average of 1 period, a fluctuation | variation also becomes small as the number of periods which take a moving average increases.

In step 105, the frequency calculation unit 7 calculates the frequency f (t) of the system. The voltage rotation vector of the system is rotated by the phase angle Ψ (t) == 4N × δ (t) in the counterclockwise direction on the complex plane during one period of the reference wave, that is, t = _{0 to} t = T _0. To do. Therefore, the system frequency f (t) is expressed as f (t) = (Ψ (t) / 2π) × f0 = 4N × δ (t) from the proportional relationship between the phase angle Ψ (t) and the reference frequency f0. I can express. The frequency obtained in this way is the “static frequency” as referred to by the inventor. In the present invention, in order to avoid the influence of a sudden phase change (voltage flicker) and the like and reduce the error, the equation (9) The frequency f (t) is obtained by the following equation (11) using the rotational phase angle average value δ _ave (t) shown in equation (10) instead of the phase angle δ (t) shown in FIG. .

  In step 106, the frequency change rate instantaneous value calculation unit 8 calculates the instantaneous frequency change rate using equation (12) based on the frequency f (t) calculated by the frequency calculation unit 7 and the frequency several cycles before. To do. Here, N = 3, that is, sampling for one cycle of the reference wave is completed by sampling of 12 steps, and the difference from the frequency three cycles before is calculated as the instantaneous frequency change rate. That is, f (t-36T) is used. When implemented, the frequency before another cycle number may be used.

  In step 107, the frequency change mode determination unit 9 determines whether the frequency change mode is the frequency acceleration mode, the frequency deceleration mode, or none of these modes based on the frequency difference information. Determine whether. In step 108, the frequency acceleration / deceleration counter unit 10 determines whether the instantaneous value of the rate of change of the system frequency is an increase state, a decrease state, an increase state or a decrease state, depending on the frequency change mode determined in step 107. It is determined whether it is not applicable. Further, the frequency acceleration / deceleration counter unit 10 performs count processing of the frequency acceleration counter and the frequency deceleration counter based on these determination results.

  Here, the process of step S107 will be described with reference to FIGS. FIG. 3 is a diagram showing an example of a frequency change with the horizontal axis when the change in the system frequency is in an increasing state as a time axis. FIG. 4 shows the horizontal axis when the change in the system frequency is in a decreasing state. It is a figure which shows an example of the frequency change on the time axis.

3 and 4, T is a sampling one step time. For example, in this embodiment where N = 3, in a system with a reference frequency of 60 Hz, the sampling one step time is T = 1/60/12 = 0.0138888889 seconds. Note that one cycle time of the reference wave is represented by T ₀ = 1/60 = 0.0166666667 seconds. f (t) is the frequency measured at the present time. f (t−T) is a frequency measured before one step. f (t−2T) is a frequency measured at a time point two steps before. f (t−36T) is a frequency measured at the time point 36 steps before (3 cycles before). f (t−37T) is a frequency measured at a point before 37 steps (3 cycles + 1 step before). f (t−38T) is a frequency measured at the time point 38 steps before (3 cycles + 2 steps before).

  Next, the definition of the frequency acceleration mode will be described with reference to FIG. The conditions for the frequency acceleration mode are as follows.

  However, ε is a small positive real number (for example, 0.00001 Hz). When the equations (14) to (18) are simultaneously established, the frequency change mode is determined as the frequency acceleration mode. Thus, it can be seen that the frequency acceleration mode accelerates in both a small range (formula (14) and formula (15), formula (16) and formula (17)), and a wide range (formula (18)).

  Next, the definition of the frequency deceleration mode will be described with reference to FIG. The conditions for the frequency deceleration mode are as follows.

  However, ε is a small positive real number (for example, 0.00001 Hz). When the equations (19) to (23) are simultaneously established, the frequency change mode is determined as the frequency deceleration mode. Thus, it can be seen that the frequency deceleration mode decelerates in both a small range (formula (19) and formula (20), formula (21) and formula (22)), and a wide range (formula (23)).

  When neither the frequency acceleration mode nor the frequency deceleration mode is selected, the frequency change mode is determined as the frequency latch mode. The frequency latch mode is a state where it cannot be determined whether the frequency is accelerating or decelerating.

  It should be noted that the threshold values (ε) shown in the equations (14) to (18) for determining whether the frequency acceleration mode is set and the equations (19) to (23) for determining whether the frequency deceleration mode is set. ) Are represented by the same ε, but they do not have to be the same value, and different values may be used.

  The addition formula and subtraction formula of the frequency acceleration counter Nfp and the addition formula and subtraction formula of the frequency deceleration counter Nfn are as follows. However, the maximum value is the threshold value Nf.

  Next, details of the processing flow of step 108 will be described with reference to FIG. FIG. 5 is a flowchart showing details of the frequency change mode and the counter processing of the frequency acceleration / deceleration counter.

  When the process of the frequency change mode determination unit 9 is executed, a sub-flow of the counter process (step S108) of the frequency acceleration / deceleration counter is started. In FIG. 5, in step 201, it is determined whether or not the current frequency change mode is the frequency acceleration mode. When the current frequency change mode is the frequency acceleration mode (Yes in step S201), the process proceeds to step 202. On the other hand, when the current frequency change mode is not the frequency acceleration mode (No in step S201), the process proceeds to step 203.

  In step 202, the frequency acceleration / deceleration counter unit 10 determines whether or not the instantaneous frequency change rate is larger than a certain threshold based on the following equation (28).

Here, df _SET is a frequency change rate activation threshold value, for example, 0.5 Hz / s. When Expression (28) is satisfied (step 202, Yes), the process proceeds to step 208. In step 208, the frequency acceleration counter is incremented according to the addition formula of equation (24), and at the same time, the frequency deceleration counter is decremented by 1 according to equation (27). When Expression (28) is not satisfied (No at Step 202), the process proceeds to Step 206, and 1 is subtracted from the frequency acceleration counter and the frequency deceleration counter according to Expression (25) and Expression (27), respectively.

  In step 203, it is determined whether or not the current frequency change mode is the frequency deceleration mode. When the current frequency change mode is the frequency deceleration mode (step S203, Yes), the process proceeds to step 204. On the other hand, when the current frequency change mode is not the frequency deceleration mode (No in step S203), the process proceeds to step 205.

  In step 204, the frequency acceleration / deceleration counter unit 10 determines whether or not the instantaneous frequency change rate is smaller than a certain threshold based on the following equation (29).

Here, df _SET is a frequency change rate activation threshold value, for example, 0.5 Hz / s. When Expression (29) is satisfied (step 204, Yes), the process proceeds to step 207. In step 207, the frequency deceleration counter is incremented by 1 according to equation (26), and at the same time, the frequency acceleration counter is decremented by 1 according to equation (25). If Expression (24) is not satisfied, the process proceeds to Step 206, and 1 is subtracted from the frequency acceleration counter and the frequency deceleration counter according to Expression (25) and Expression (27), respectively.

  Further, in the state transferred to step 205, the current frequency change mode is neither the frequency acceleration mode nor the frequency deceleration mode, and this state is called a latch mode. In step 206, the frequency acceleration / deceleration counter unit 10 subtracts 1 from the frequency acceleration counter and the frequency deceleration counter according to the equations (25) and (27), respectively.

  In step 206, the frequency acceleration / deceleration counter unit 10 subtracts 1 from the frequency acceleration counter and the frequency deceleration counter according to the equations (25) and (27), respectively. In step 207, the frequency acceleration / deceleration counter unit 10 adds 1 to the frequency deceleration counter according to equation (26), and simultaneously subtracts 1 from the frequency acceleration counter according to equation (25). In step 208, the frequency acceleration / deceleration counter unit 10 adds the frequency acceleration counter according to the addition formula of equation (24), and simultaneously subtracts 1 from the frequency deceleration counter according to equation (27).

  Returning to FIG. 2, in step 108, the frequency acceleration counter and the frequency deceleration counter are compared with a certain threshold value. When the frequency acceleration counter is equal to a threshold value (for example, 36, 12 points for one cycle in the case of 30-degree sampling of the reference wave, and 36 corresponds to three-cycle verification) as shown in the following equation (30), FIG. A shut-off command is output to the circuit breaker shown.

  When the frequency deceleration counter is equal to the threshold value as shown in the following equation (31), it similarly outputs a cutoff command to the circuit breaker.

  Next, the routine proceeds to step 109, where it is determined whether or not there is an end instruction. If there is an end instruction (step 109, Yes), the series of operations is ended. If there is no end instruction (step 109, No), the process proceeds to step 101.

  As a result of simulating the frequency, frequency change rate, and frequency acceleration counter calculated and measured as described above, the results shown in FIGS. 6 to 8 were obtained. The set value of the voltage waveform input frequency is 60 Hz. Furthermore, in order to simulate voltage flicker, the phase of the voltage waveform was suddenly changed by 30 degrees (0.52359877 radians) when 0.15 seconds had elapsed. FIG. 6 shows the measurement frequency. According to this, when 0.15 seconds passed, a large fluctuation was observed in the measurement frequency due to the sudden phase change simulating voltage flicker.

  FIG. 7 shows the measurement result of the frequency change rate. Even in this case, a large fluctuation was observed when 0.15 seconds passed.

  FIG. 8 shows the measurement result of the frequency acceleration counter. According to this, the frequency acceleration counter remains zero even though large fluctuations in frequency and frequency change rate are observed in FIGS. Although the result was not displayed for the frequency deceleration counter, the frequency deceleration counter remained zero. As a result, even though a sudden phase change simulating voltage flicker was input, a shutoff command for the power system was not output. That is, this indicates that 95D malfunction due to voltage flicker was avoided.

  As described above, the frequency change rate protection relay device according to the present invention is suitable for application to the frequency change rate protection relay device of the power system stabilization device.

It is a figure explaining the structure of the frequency change rate protection relay apparatus in embodiment of this invention. It is a flowchart explaining operation | movement of the frequency change rate protection relay apparatus in embodiment of this invention. It is a figure which shows an example of the frequency change which made the horizontal axis the time axis | shaft in case the change of a system | strain frequency is in an increase state. It is a figure which shows an example of the frequency change which made the horizontal axis the time axis | shaft in case the change of a system | strain frequency is in a decreasing state. It is a flowchart explaining the calculation method of the frequency change mode and the frequency acceleration / deceleration counter of the frequency change rate protection relay device in the embodiment of the present invention. It is a graph which shows an example of the measurement result of the frequency in the simulation of this Embodiment. It is a graph which shows an example of the measurement result of the frequency change rate in the simulation of this Embodiment. It is a graph which shows an example (when there exists a phase sudden change (voltage flicker)) of the measurement result of the frequency acceleration counter in the simulation of this Embodiment. It is a graph which shows an example of the measurement result of the frequency in this inventor's prior application invention. It is a graph which shows an example of the measurement result for the frequency change in the present invention of the present inventor. It is a graph which shows an example (when there exists a phase sudden change (voltage flicker)) of the measurement result of the frequency change rate in the prior invention of this inventor.

Explanation of symbols

1 Frequency change rate protection relay device 2 Voltage / current measurement unit 3 A / D conversion unit
4 Voltage amplitude and moving average value calculating unit 5 String length and moving average value calculating unit 6 Rotating phase angle and moving average value calculating unit 7 Frequency calculating unit 8 Frequency change rate instantaneous value calculating unit 9 Frequency change mode determining unit 10 Frequency acceleration / deceleration counter unit 11 Interface 12 Power system protection command output unit 13 Storage unit 14 Frequency change average value 15 Frequency change instantaneous value 16a Frequency change rate start threshold 16b Frequency change rate start threshold 17 Frequency change rate Average value 18 Frequency change rate instantaneous value

Claims (2)

The amplitude value of the voltage rotation vector expressed on the complex plane using the instantaneous voltage value sampling data of the power system obtained at each sample timing obtained by equally dividing one period of the reference wave by 4N (N is a positive integer) A voltage amplitude calculation unit for calculating by integral operation using voltage instantaneous value sampling data in one cycle of the wave;
A voltage amplitude average value calculation unit that averages the voltage amplitude value calculated by the voltage amplitude calculation unit by performing a moving average process over a period of one cycle or more of the reference wave;
A chord length calculation unit that calculates a chord length, which is an interval between the tips of two adjacent voltage rotation vectors, by an integral operation using voltage instantaneous value sampling data in one cycle of the reference wave;
A chord length average value calculation unit that averages the chord length calculated by the chord length calculation unit by performing a moving average process over a period of one cycle or more of the reference wave;
A rotation phase angle calculation unit that calculates a rotation phase angle of a voltage rotation vector using the voltage amplitude average value calculated by the voltage amplitude average value calculation unit and the string length average value calculated by the string length average value calculation unit;
A rotation phase angle average value calculation unit that averages the rotation phase angle calculated by the rotation phase angle calculation unit by performing a moving average process over a period of one cycle or more of the reference wave;
A frequency calculation unit that calculates a frequency of the system using the frequency of the reference wave and the rotation phase angle average value calculated by the rotation phase angle average value calculation unit;
A frequency change instantaneous value calculation unit that calculates an instantaneous value of a frequency change that is a difference between two frequencies at each of two sample timings separated by a certain period;
A frequency change rate instantaneous value calculation unit for obtaining an instantaneous value of the frequency change rate obtained by dividing the frequency change by the time between sample timings;
Comparing the instantaneous value of the frequency change with a predetermined first threshold, whether the frequency change mode is in an increasing state, whether the frequency change is in a decreasing state, A frequency change mode determination unit that determines whether the latch mode does not correspond to either the frequency acceleration mode or the frequency deceleration mode;
According to the determination result of the frequency change mode determination unit, the instantaneous value of the frequency change rate is compared with a predetermined second threshold value to determine whether the frequency change rate in the frequency acceleration mode is in an increasing state or not. A counter for determining whether the frequency change rate in the mode is in a decreasing state and not corresponding to any of these states, and quantifying information of the determination result;
With
The frequency change rate protection relay device, wherein a protection command for the power system is output based on a comparison result obtained by comparing the count value quantified by the counter unit with a predetermined third threshold value. The counter unit is
The determination result of the frequency change mode determination unit is the frequency acceleration mode, and is added when the instantaneous value of the frequency change rate exceeds the predetermined second threshold,
Subtracted when the determination result of the frequency change mode determination unit is the frequency acceleration mode and is equal to or less than the predetermined second threshold,
An acceleration counter to be subtracted when the determination result of the frequency change mode determination unit is the latch mode;
The determination result of the frequency change mode determination unit is a frequency deceleration mode, and is added when the instantaneous value of the frequency change rate is less than the predetermined second threshold,
Subtracted when the determination result of the frequency change mode determination unit is a frequency deceleration mode and is equal to or greater than the predetermined second threshold,
A subtraction counter to be subtracted when the determination result of the frequency change mode determination unit is the latch mode;
With
2. The frequency according to claim 1, wherein the protection command for the power system is output when a count value of any one of the acceleration counter and the deceleration counter is equal to or greater than the predetermined third threshold value. Change rate protection relay device.

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