JP3952355B2 - Distribution system monitoring method - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention, the cause of the operational state or a failure of demand house equipment Te distribution system smell, the present invention relates to the method of monitoring the distribution system which enables estimating the failure facilities.
[0002]
[Prior art and problems to be solved by the invention]
In the power distribution system, when an abnormality occurs in power quality, a lot of experience and skill are required to understand the fault, analyze the cause, and identify the faulty equipment.
For example, even when measuring the voltage of a distribution system, conventional measuring instruments have only a function for measuring a fixed time interval or a simple voltage fault detection function such as instantaneous maximum value or effective voltage value. It is not possible to accurately measure instantaneous abnormalities such as
In addition, there are some measuring instruments that have a simple detection function that can be constantly monitored, but a lot of data measured under conditions that are not so narrowed tend to be collected. It was necessary to discriminate data from the viewpoint of whether there was a specific problem or whether the regulation value was violated. For this reason, it is necessary to store and calculate a large amount of data, which requires enormous memory capacity, calculation load, and great effort.
[0003]
In addition, conventionally, the operation status of equipment is recorded manually, or the approximate operating time is simply recorded by a wattmeter or the like that is simply measured at regular time intervals. It is impossible to perform simultaneous multipoint analysis because data cannot be synchronized.
[0004]
When estimating the cause of failure, a skilled and experienced analyst performs analysis based on experience and intuition based on the measured data, and a skilled analyst with systematic knowledge operates the equipment based on the data. He was teaching the method empirically.
Furthermore, in order to estimate the cause of a complex failure through a plurality of customers and systems, an analyst with system knowledge has analyzed based on measurement data based on experience and intuition.
On the other hand, when it is required to continuously monitor a failure that does not know when it occurs in the distribution system for each failure item, it is required to calculate and determine continuous data of complex alternating current electricity in real time.
[0005]
The present invention, in order to solve the above problems, without depending on the experience and intuition of ripe kneading's detected operational state of the customer equipment, failure cause, failure facilities in real time, can be estimated as the power distribution system It is intended to provide a monitoring method.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is a method for monitoring an operation state of a customer facility existing in a distribution system.
Calculating fundamental wave active power and fundamental wave reactive power from fundamental wave voltage and fundamental wave current supplied to customer equipment;
A determination step for determining presence or absence of fundamental wave active power fluctuation and fundamental wave reactive power fluctuation over a predetermined time interval estimated to be a transient state ;
A determination step for determining whether the fundamental wave active power fluctuation and the fundamental wave reactive power fluctuation are positive or negative;
Determining whether or not the fifth harmonic current is greater than the fundamental current when the fundamental reactive power fluctuation is positive,
To have use a result of the decision made by these judgments step is to estimate the operational state of the consumer equipment.
[0007]
The invention described in claim 2 is the distribution system monitoring method according to claim 1,
When it is determined that the fundamental wave active power fluctuation is positive, it is determined that the load is input to the customer,
When it is determined that the fundamental wave active power fluctuation is negative, it is determined that the customer's load is cut off,
When it is determined that there is no fundamental wave active power fluctuation and there is no fundamental wave reactive power fluctuation, it is determined that the abnormality is caused by noise or other customers,
When there is no fundamental wave active power fluctuation and it is judged that the fundamental reactive power fluctuation is negative, it is determined that the power factor improving capacitor of the consumer is inserted,
When it is determined that the fundamental wave reactive power fluctuation is not positive and the fundamental reactive power fluctuation is positive and the fifth harmonic current is larger than the fundamental current, it is determined that the protection relay operation for iron resonance is performed,
When it is determined that the fundamental wave reactive power fluctuation is not present and the fundamental reactive power fluctuation is positive and the fifth harmonic current is smaller than the fundamental current, it is determined that the power factor improving capacitor of the consumer is open. Thus, the operation state (input, stoppage, etc.) of the customer facility is estimated.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
First, as a reference technique of the present invention, it describes a method for monitoring the quality of the system voltage in the three-phase power distribution system.
[0011]
In the flowchart of FIG. 1, first, the instantaneous value of the system voltage is converted into a digital value for each phase, and this is sampled at a predetermined period. For example, the true voltage is obtained by the square root mean square value of 512 sampling values per period. The effective value (total effective value) is obtained. This effective value is an electric quantity including a fundamental wave and a harmonic.
[0012]
At the same time, a fundamental wave effective value is obtained by Fourier transform (S1).
For the calculation of the effective value of the fundamental wave by Fourier transform, for example, the “effective value measurement method” disclosed in Japanese Patent Application Laid-Open No. 8-262207 can be used. Briefly, the frequency waveform data is obtained by fast Fourier transform (FFT) of the digital waveform data of the system voltage, and further, the period T ₀ of the fundamental wave component of the system voltage is obtained from this frequency component data. those by the digital waveform data corresponding to T ₀ is read from the waveform memory to calculate for each data of each sampling point or interpolation point, the square root of the mean square of the duration direct calculation to the determine the fundamental wave RMS value It is .
[0013]
Next, in the effective value calculation in step S1, it is determined whether or not the instantaneous voltage value has exceeded the range due to an overvoltage such as an impulse voltage (S2). Here, the reference value for determining the range over is, for example, a value that is four times the effective value.
[0014]
When the voltage instantaneous value is determined to be over-range, it is determined whether or not the state continues for a certain period (S6). If the voltage instantaneous value continues, the worst data (the difference from the reference value is the maximum). And the duration of the worst data is measured by a timer (S7).
In step S6, if it does not continue for a certain period of time (when an abnormality is detected for the first time), an instantaneous value for a plurality of cycles before and after the current time (or only after one cycle). Is held as initial data to perform trigger processing (S8). This trigger processing refers to processing for taking in a voltage instantaneous value deviating from a reference value or a maximum value and a minimum value described later as trigger data. Here, by holding a very small number of initial data (trigger data) as instantaneous values, it is possible to save memory and to easily perform subsequent analysis work using a personal computer or the like.
[0015]
If the instantaneous voltage value is not over the range, it is determined whether or not the true voltage effective value of each phase deviates from the allowable range based on the minimum value and the maximum value (S3). If it deviates, the process jumps to step S6, and if it does not deviate, the process proceeds to the next step S4.
[0016]
Next, for each phase, the total distortion rate of the voltage is calculated and compared with the reference value (S4). Here, the total distortion rate is defined by the following Equation 1.
[Equation 1]
Total distortion factor = √ {(true voltage effective value) ² − (fundamental wave effective value) ² } / | fundamental wave effective value |
In Equation 1, the true voltage effective value is the square root mean square value of the instantaneous value, and the fundamental wave effective value is the fundamental wave effective value obtained by Fourier transform.
The reference value is set to 5%, for example.
[0017]
If the total distortion rate exceeds the reference value, it is determined that the quality abnormality has a high harmonic content, and the process jumps to step S6. If the total distortion rate does not exceed the reference value, the process proceeds to the next step S5.
Next, a voltage imbalance rate is calculated and compared with a reference value (S5). Here, the voltage imbalance rate is defined by the following Equation 2.
[Equation 2]
Voltage unbalance ratio = fundamental wave negative phase voltage effective value / fundamental wave positive phase voltage effective value The reference value to be compared with this voltage unbalance ratio is set to 3%, for example.
[0018]
If the voltage unbalance rate exceeds the reference value, it is determined that the quality is abnormal due to the three-phase unbalance, and the process jumps to step S6. If the voltage unbalance rate does not exceed the reference value, the process returns to the above step S1 again. A similar process is executed.
[0019]
According to the above method, the true rms value and the fundamental rms value are obtained simultaneously, and the monitoring of the magnitude of the voltage rms value, generation of impulse voltage, presence of harmonics, voltage imbalance monitoring, etc. are continuously performed. Can be executed.
Further, since the abnormality detection cycle is short, there is an advantage that the failure occurrence time can be detected accurately. Furthermore, the power quality can be continuously monitored with high accuracy by using a technique in which accuracy is not easily lowered even if partial thinning calculation is performed.
[0020]
Next, a first embodiment of the present invention will be described with reference to FIGS. This embodiment is mainly an embodiment of the invention described in claims 1 and 2, and for example, starting and stopping each equipment from the voltage and current of a customer equipment such as a load, a power factor improving capacitor (SC), a transformer, etc. It is for estimating the operational state.
[0021]
2, first, the measurement data of the three-phase system voltage scans at regular time intervals (S11), by the equation 2 by using the fundamental wave positive phase voltage effective value V ₁ and the fundamental wave negative phase voltage effective value V ₂ The calculated voltage imbalance rate is compared with a reference value (for example, 3%) (S12).
If the voltage imbalance rate does not exceed the reference value, the process jumps to step S14 described later.
If the voltage unbalance rate is greater than or equal to the reference value, for example, there is a risk that the three-phase motor will burn out, so this is output as an alarm, and the trend display of the voltage unbalance rate is performed (S13).
[0022]
Next, the total voltage distortion rate ε is calculated by the equation 1 and compared with a reference value (for example, 5%) (S14). If the total voltage distortion rate ε does not exceed the reference value, the process jumps to step S16 described later.
If the total voltage distortion rate ε is greater than or equal to the reference value, an alarm is output, and at the same time, the distortion rate ε is trend-displayed (S15).
[0023]
Furthermore, calculating a fifth harmonic voltage distortion factor epsilon _5, comparing this reference value (e.g. 3.5%) (S16). The fifth harmonic voltage distortion factor epsilon ₅ jumps to step S18 to be described later does not exceed the reference value.
When the fifth harmonic voltage distortion rate ε ₅ is equal to or higher than the reference value, an alarm is output, and at the same time, the distortion rate ε ₅ is trend-displayed (S17).
Note that steps S12 to S17 described above constitute stationary harmonic determination processing.
[0024]
Next, the current i _C of the power factor improving capacitor of the consumer is detected and compared with a reference value (for example, 120%) (S18). If the current i _C does not exceed the reference value, the process jumps to step S23 described later.
If the current i _C is greater than or equal to the reference value, an alarm is output, and at the same time, i _C is displayed as a trend, and the three-phase fundamental active power is calculated (S19).
[0025]
Next, the operator is inquired on the screen for the presence or absence of% L (% reactance) (S20), and if there is, it is determined that the cause of the capacitor current i _C exceeding the reference value is a harmonic (S21). . If% L is not present, it is determined that the cause of the capacitor current i _C exceeding the reference value is the commutation notch fluctuation (S22).
[0026]
Moving to FIG. 3, the presence / absence of the trigger process described in FIG. 1 (absence of occurrence of abnormality) is determined (S23).
If there is a trigger, it is determined whether or not there is a change ΔP in the active power (S24). Here, ΔP is a variation of the active power P obtained by a vector product of the fundamental wave voltage and the fundamental wave current, and refers to a variation of the active power P at a point separated by a plurality of cycles estimated as a transient state.
When there is a variation ΔP in active power (when ΔP exceeds a certain set value), the positive / negative is determined (S25). On the other hand, when there is no variation, the presence / absence of a variation ΔQ in reactive power is determined ( S28). The reactive power fluctuation ΔQ is the reactive power Q fluctuation obtained from the vector product of the fundamental wave voltage and the fundamental wave current, and the reactive power fluctuation at the time of multiple cycles that is estimated to be a transient state. Say.
[0027]
If ΔP is positive, it is determined that the load of the consumer is the cause (S26). If ΔP is negative, it is determined that the load is interrupted by the consumer (S27). In this case, the process proceeds to step S35.
When there is ΔQ (when ΔQ exceeds a certain set value), the positive / negative is determined (S30). On the other hand, when there is no ΔQ, it is determined that an abnormality has occurred due to noise or other customers. (S29) Then, the process proceeds to step S35.
[0028]
If ΔQ is positive, it is determined whether the fifth harmonic current i ₅ is larger than the fundamental current i ₁ (S31). On the other hand, if ΔQ is negative, the power factor of the consumer is improved. It is estimated that a capacitor has been inserted (S32), and the process proceeds to step S35.
When the fifth harmonic current i ₅ is larger than the fundamental wave current i ₁ shifts estimated that protection relay for ferroresonant is operated to (S33) step S35. If it is smaller, it is estimated that the power factor improving capacitor of the consumer has been opened (S34), and the process proceeds to step S35.
[0029]
In step S35, compares the voltage effective value V and the lower limit value _{V min,} the effective value V is shifted to step S37 if the lower limit _{V min.}
If the effective value V is less than or equal to the lower limit value _Vmin , the time of occurrence and its duration are displayed (S36) and the process proceeds to step S37.
In step S37, the time and the estimated cause (steps S26, S27, S29, S32, S33, S34) are displayed.
[0030]
A specific estimation example according to the present embodiment will be described with reference to FIGS.
FIG. 4 shows the values of the fundamental wave active power P, the reactive power Q, the voltage imbalance rate, and √3V ₁ for each measurement date and time for the first period and the third period. Shows the U-phase current and the current fluctuation ΔI in the data of 14:22:35 on December 1 (the part surrounded by a frame).
According to the present embodiment, since ΔP after two periods is greatly positive, an abnormality occurs due to the introduction of the load (in this case, the transformer) of the consumer in steps S25 and S26 of FIG. Is estimated to have fluctuated).
[0031]
FIG. 6 also shows the values of the fundamental wave active power P, the reactive power Q, the voltage imbalance rate, and √3V ₁ for the first period and the third period. FIG. This shows the W-phase current and current fluctuation ΔI in the data at 14:25:45 on December 1 (portion surrounded by a frame).
According to the present embodiment, ΔQ over a plurality of periods is greatly negative, and therefore an abnormality occurs due to the insertion of the power factor improving capacitor of the consumer in steps S30 and S32 of FIG. 3 (the reactive power fluctuates). It is estimated that In this example, ΔP is also a positive value. However, since its magnitude is less than the set value, it is processed as “no ΔP” in step S24 of FIG.
[0032]
In this embodiment, fluctuations ΔP and ΔQ before and after the transient state of the fundamental wave active power and fundamental wave reactive power in the consumer are detected, and the load on the consumer, the power factor improving capacitor, the transformer are detected based on the magnitudes thereof. It is possible to estimate the operation state such as the input / stop of the system.
[0033]
Next, a second embodiment of the present invention will be described. This embodiment decomposes the current when turned in demand house facilities into a frequency spectrum, the DC component of the current, the fundamental wave component, the harmonic component operation status and fault equipment consumer equipment based on the waveform pattern of Is estimated.
[0034]
FIG. 8 shows a current waveform when each customer facility is turned on. FIG. 8A shows a _DC component I _DC , a fundamental wave component I ₁ , and a second adjustment by decomposing the current of the power receiving transformer into a frequency spectrum. FIG. 8B shows a waveform pattern divided into a wave component I ₂ and other harmonic components I _x , and FIG. 8B shows the current of the induction motor as a direct current component I _DC , a fundamental wave component I ₁ , a fifth harmonic component I ₅ , FIG. 8 (c) shows a current pattern of a power factor improving capacitor without a reactor as a direct current component I _DC , a fundamental wave component I ₁ , a fifth harmonic component I ₅ , and a waveform pattern that is divided into other harmonic components I _x . The waveform pattern divided into other harmonic components I _x , FIG. 8 (d), shows the _DC component I _DC , fundamental component I ₁ , fourth harmonic Divided into wave component I ₄ and other harmonic components I _x Is a waveform pattern.
As is clear from FIGS. 8A to 8D, the ratios of the frequency components including the DC component are different for each facility and change with time. In this embodiment, these ratios and Estimate the equipment that has been input and the equipment that has failed using the change pattern.
[0035]
Since the rated current of various customer facilities is proportional to the fundamental wave component I ₁ , in this embodiment, the specific harmonics (transient harmonics) of typical orders are similar in proportion to I ₁ regardless of the rating of the facility. Is converted into a general monitoring parameter (reference monitoring parameter).
That is, I _DC / I ₁ : DC component monitoring parameter I ₂ / I ₁ : second harmonic component monitoring parameter I ₄ / I ₁ : fourth harmonic component monitoring parameter I ₅ / I ₁ : fifth harmonic component monitoring It is a parameter.
[0036]
Since the approximate waveform pattern when each customer facility is introduced is known as shown in FIG. 8, the above-mentioned reference monitoring parameter is calculated in advance for a plurality of cycles for each facility, and the change pattern is stored as a reference pattern. In addition, it is possible to estimate which equipment has been put in by comparing with a change pattern of the actually observed monitoring parameter. Moreover, it becomes possible to estimate a faulty facility by comparing and collating a reference pattern during normal operation of each facility with a change pattern during observation.
Note that a voltage waveform pattern may be used instead of the current waveform pattern of FIG.
[0037]
Further, based on the first embodiment or the second embodiment described above, the contract power amount of the consumer, the capacity of each transformer, the capacity of the power factor improving capacitor, the capacity of the power factor improving capacitor with the reactor, and the operation mode thereof , "Customer information" such as consumer industries based on the capacity ratio of household electric power and industrial electric power, back impedance that depends on the bank capacity of the system, overhead wire distance, etc., the vicinity obtained by multipoint simultaneous observation Combining “system information” such as time changes in voltage / current of the customer, the identification accuracy of the customer facility that has started / stopped or failed has been further increased based on the estimation according to the first embodiment or the second embodiment. It is possible to increase.
As a result, it becomes easy to attach a so-called trick about the operational state of the facility, and the practicality and convenience are greatly improved.
[0038]
Next, a third embodiment of the present invention will be described. This embodiment is to estimate the harmonic generation facilities and harmonic conducive facilities based on the correlation between the voltage distortion rate with respect to the change pattern of the basic wave active power and the reactive power.
[0039]
FIG. 9 is a configuration example of a power distribution system to which the present embodiment is applied. Assume that the customer 1 has a harmonic generation facility 10 and the customer 2 includes a power factor improving capacitor SC. In addition, instrumental current transformers VCT1 and VCT2 for watt hour meters (not shown) are connected between each facility and the distribution system. These VCT1 and VCT2 can simultaneously measure the system voltage and the consumer current.
[0040]
In the present embodiment, for example, temporal changes in the fundamental wave active power and the reactive power over a period of one day or longer are detected, and the correlation between these and the system voltage distortion rate is analyzed.
That is, the consumer's active power P detected via the VCT represents the operating state of the customer's equipment, so the consumer that is the harmonic generation source is estimated from the correlation between this active power and the system voltage distortion rate. Moreover, since the reactive power Q of the customer detected through the VCT represents the state of the power factor capacitor, the correlation between the reactive power and the system voltage distortion rate can be used as a harmonic promoting facility. A power factor improving capacitor (surplus capacitor) can be estimated.
[0041]
For example, it is assumed that the time change of the fundamental wave active power P measured by the VCT1 of a certain customer, for example, the customer 1 is as shown in FIG. 10A, and the time change of the system voltage distortion rate during this period is the same (b ), It is empirically known that the temporal change of the fundamental wave active power P corresponding to the operating state of the equipment and the temporal change of the system voltage distortion rate have a generally positive correlation. It can be estimated that the distortion of the system voltage, that is, the generation of harmonics is due to the customer 1 having the harmonic generation facility 10.
[0042]
As shown in FIG. 10 (a), although the active power P of the customer 1 is almost zero at night, a change in the system voltage distortion rate occurs as indicated by the symbol A in FIG. 10 (b). In this case, it can be estimated that this change is due to the operation of equipment at other consumers.
[0043]
Further, the time change of the fundamental wave reactive power Q measured by the VCT 2 of the customer 2 is as shown in FIG. 11A, and the time change of the system voltage distortion rate during this period is as shown in FIG. 11B. And It is empirically known that the change in reactive power (power factor advances) due to the insertion of the power factor correction capacitor and the time change in the system voltage distortion rate are almost opposite to each other. It can be estimated that the increase in the system voltage distortion rate at night, that is, the increase in harmonics, is due to the harmonics being promoted by the power factor improving capacitor SC of the customer 2.
Here, a consumer who does not have an automatic power factor adjustment function fixes the capacity of the capacitor SC so that the power factor of 1 is the daytime maximum power point (symbol B in FIG. 11A) so as not to become a delay power factor. Therefore, this embodiment is useful for the determination of the presence / absence of the automatic power factor adjustment function and the determination of the degree of excessive phase.
[0044]
According to this embodiment, it is possible to estimate a consumer having a harmonic generation facility and a harmonic enhancement facility without performing intricate and high-grade harmonic current inflow and outflow calculations.
[0046]
【The invention's effect】
As described above , according to the present invention, based on the magnitude of the active power fluctuation and reactive power fluctuation and the ratio of the current component or voltage component to the fundamental component of the direct current component or specific harmonic component, the operational state or failure of the customer facility Generation facilities can be estimated, and analysis can be easily performed even if the operator is not a skilled operator having specialized knowledge .
[0047]
Further, according to the present invention, disabilities cause or particular disorder facilities estimation harm is achieved efficiently, which contributes to labor saving. In addition, it is reasonable to create instruction explanation materials for consumers based on monitoring results and estimation results.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining a reference technique of the present invention.
FIG. 2 is a flowchart showing a first embodiment of the present invention.
FIG. 3 is a flowchart showing a first embodiment of the present invention.
Is a diagram illustrating an example of a cause estimation in the first embodiment of the present invention; FIG.
FIG. 5 is a waveform diagram showing a system current and its variation in the first embodiment of the present invention.
6 is a diagram showing an example of a cause estimation in the first embodiment of the present invention.
FIG. 7 is a waveform diagram showing a system current and its variation in the first embodiment of the present invention.
FIG. 8 is a waveform diagram showing temporal changes in current components for each customer facility in the second embodiment of the present invention.
FIG. 9 is a system configuration diagram according to a third embodiment of the present invention.
FIG. 10 is a waveform diagram showing a correlation between active power and system voltage distortion rate in the third embodiment of the present invention.
FIG. 11 is a waveform diagram showing a correlation between reactive power and system voltage distortion rate in the third embodiment of the present invention.
[Explanation of symbols]
10 Harmonic generation equipment SC Power factor improving capacitor VCT1, VCT2 Instrument transformer

Claims (2)

In the method of monitoring the operational status of customer equipment existing in the distribution system,
Calculating fundamental wave active power and fundamental wave reactive power from fundamental wave voltage and fundamental wave current supplied to customer equipment;
A determination step for determining presence or absence of fundamental wave active power fluctuation and fundamental wave reactive power fluctuation over a predetermined time interval estimated to be a transient state;
A determination step for determining whether the fundamental wave active power fluctuation and the fundamental wave reactive power fluctuation are positive or negative;
Determining whether or not the fifth harmonic current is greater than the fundamental current when the fundamental reactive power fluctuation is positive,
A method for monitoring a distribution system, characterized in that an operation state of a customer facility is estimated using a determination result obtained by these determination steps. In the distribution system monitoring method according to claim 1,
When it is determined that the fundamental wave active power fluctuation is positive, it is determined that the customer's load is input,
When it is determined that the fundamental wave active power fluctuation is negative, it is determined that the customer's load is cut off,
When it is determined that there is no fundamental wave active power fluctuation and there is no fundamental wave reactive power fluctuation, it is determined that the abnormality is caused by noise or other customers,
When there is no fundamental wave active power fluctuation and it is judged that the fundamental reactive power fluctuation is negative, it is judged that the power factor improving capacitor of the consumer is inserted,
When it is determined that there is no fundamental wave active power fluctuation and the fundamental wave reactive power fluctuation is positive and the fifth harmonic current is larger than the fundamental current, it is determined that the protection relay operation for iron resonance is performed,
When it is determined that the fundamental wave reactive power fluctuation is not positive and the fundamental wave reactive power fluctuation is positive and the fifth harmonic current is smaller than the fundamental current, it is determined that the power factor improving capacitor of the consumer is open. And the monitoring method of a power distribution system characterized by estimating the operation state of a consumer facility.

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