JP5140813B2 - Excitation current phenomenon identification method - Google Patents

Description

  The present invention relates to a method for specifying an inrush current phenomenon that specifies whether or not an instantaneous voltage drop is caused by an inrush current of a transformer when an instantaneous voltage drop occurs in a power system.

  When an instantaneous voltage drop occurs in the power system, various troubles such as equipment stoppage occur. For example, a mercury lamp is extinguished, or a large device using electric power as a power source is stopped. One of the causes of the instantaneous voltage drop is an overcurrent called an excitation inrush current due to magnetic saturation of the transformer core when the transformer is connected to the power system.

  In order to take measures against a failure due to an instantaneous voltage drop, it is fundamental to identify the cause of the instantaneous voltage drop. To determine whether the cause of the instantaneous voltage drop is due to the inrush current of the transformer, determine whether the primary current waveform of the transformer contains a lot of second and fourth harmonics, When many second harmonics and fourth harmonics are included, it is determined that the current is a magnetizing inrush current. In addition, focusing on the fact that the magnetizing inrush current phenomenon is due to magnetic saturation, it is possible to identify the magnetizing inrush current phenomenon by detecting a decrease in reactance value from the linkage flux and current, which is the integral value of the primary terminal voltage of the transformer. Some of them are designed to do this.

In order to determine the magnetizing inrush current, the magnetizing inrush current is judged based on the magnitude of the integrated detection voltage value when the magnitude of the detected current value exceeds a predetermined value. In some cases, an inrush current detection signal is output when the value is equal to or greater than a predetermined determination value (see, for example, Patent Document 1).
JP 2000-217246 A

  However, some exciting inrush currents include many other harmonics other than the second harmonic and the fourth harmonic, making it difficult to distinguish from general transients, and the second harmonic and the fourth harmonic. It is difficult to determine whether or not it is an excitation inrush current based on the content ratio. On the other hand, focusing on the fact that the magnetizing inrush current phenomenon is due to magnetic saturation, it is a current detection sensor that detects a decrease in reactance value from the flux linkage and current, which is the integral value of voltage, and identifies the magnetizing inrush current phenomenon. In some cases, an accurate current value cannot be obtained due to magnetic saturation due to overcurrent of the current transformer (CT) or overrange of the measurement system.

  In addition, we receive inquiries from customers who are suffering from instantaneous voltage drop, and in fact, there are many measurements of transformer primary current and voltage at customers affected by instantaneous voltage drop. It is often not measured by the customer. That is, when the transformer of the source of the excitation inrush current is unknown, not only the primary side current of the transformer of the source of the excitation inrush current can be measured, but also the connection method of the transformer is unknown. Therefore, the method for determining the inrush current phenomenon based on the detection of a decrease in reactance value cannot be applied.

  An object of the present invention is to provide an exciting inrush current phenomenon identifying method that can identify an exciting inrush current phenomenon even when the exciting inrush current cannot be measured, and can also identify a transformer connection method.

  The method for specifying an inrush current phenomenon according to the first aspect of the present invention is to obtain a magnetic saturation start time and a magnetic saturation end time of a transformer core when an instantaneous voltage drop occurs in a power system, and to determine a magnetic saturation start time and a magnetic saturation end time. The difference between the flux linkage of the transformer core at the magnetic saturation start time and the flux linkage of the transformer core at the magnetic saturation end time is obtained by integrating the terminal voltage of the transformer core with the time width of the magnetic saturation start time. When the interlinkage magnetic flux of the transformer core is equal to the interlinkage magnetic flux of the transformer core at the magnetic saturation end time, it is determined that the instantaneous voltage drop is caused by the magnetizing inrush current of the transformer.

  According to a second aspect of the present invention, there is provided a method for identifying an inrush current phenomenon according to the first aspect of the invention, wherein the primary current of the transformer before the occurrence of the instantaneous voltage drop is a base current and the primary current of the transformer after the occurrence of the instantaneous voltage drop is A difference from the base current is obtained as a fluctuation current, a fluctuation basic current obtained by cutting the influence of transient vibration from the fluctuation current is obtained, and the fluctuation basic current is one of the base currents after the occurrence of the instantaneous voltage drop. The zero point when the change from minus to plus or plus to minus is greatly changed between cycles is set as the magnetic saturation start time, and the zero point of the fluctuation basic current immediately after the magnetic saturation start time is set as the magnetic saturation end time. The magnetic saturation start time and magnetic saturation end time of the iron core are obtained.

  According to a third aspect of the present invention, there is provided a magnetizing inrush current phenomenon specifying method according to the first aspect, wherein the system voltage before the occurrence of the instantaneous voltage drop is a base voltage, and the system voltage and the base voltage after the occurrence of the instantaneous voltage drop are Is obtained as a fluctuation voltage, a fluctuation basic voltage obtained by cutting the influence of transient vibration from the fluctuation voltage is obtained, and the fluctuation basic voltage is calculated during one cycle of the base voltage after the occurrence of the instantaneous voltage drop. The zero point at the time of significant change from minus to plus or from plus to minus is used as the magnetic saturation start time, the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time is set as the magnetic saturation midpoint time, and the magnetic saturation start is performed. The magnetic saturation end time is obtained from the time and the magnetic saturation midpoint time.

  According to a fourth aspect of the present invention, there is provided a method for specifying an excitation inrush current phenomenon, wherein when an instantaneous voltage drop occurs in an electric power system, the system voltage before the occurrence of the instantaneous voltage drop is set as a base voltage and the base voltage after the occurrence of the instantaneous voltage drop and the base The difference from the voltage is obtained as a fluctuation voltage, a fluctuation basic voltage obtained by cutting the influence of transient vibration from the fluctuation voltage is obtained, and the fluctuation basic voltage is one cycle of the base voltage after the occurrence of the instantaneous voltage drop. The zero point when the change from minus to plus or plus to minus is greatly changed is defined as the magnetic saturation start time, and the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time is defined as the magnetic saturation midpoint time. The magnetic saturation end time is obtained from the saturation start time and the magnetic saturation midpoint time, while the time when the linkage flux of the transformer core becomes the same value as the saturation start magnetic flux is obtained. , And judging the difference between this time and the magnetic saturation end time and when within the predetermined range is a momentary voltage drop due to transformer inrush current of the transformer.

  According to a fifth aspect of the present invention, there is provided a method for specifying an inrush current phenomenon according to the third or fourth aspect of the invention, wherein the magnetic saturation midpoint time is the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time. Instead, the zero point of the base current in the saturation region of the transformer core is used.

  The method for specifying an inrush current phenomenon according to the invention of claim 6 is the magnetic saturation start time of the first cycle transformer core and the magnetic saturation start time of the second cycle transformer core when an instantaneous voltage drop occurs in the power system. Integration of the transformer core terminal voltage with the time width between the magnetic saturation start time of the first cycle and the magnetic saturation start time of the second cycle, and the linkage of the transformer core at the magnetic saturation start time of the first cycle The difference between the magnetic flux and the linkage magnetic flux of the transformer core at the magnetic saturation start time in the second cycle is obtained, and the linkage magnetic flux of the transformer core at the magnetic saturation start time of the first cycle and the magnetic saturation start time of the second cycle are calculated. When the difference from the interlinkage magnetic flux of the transformer core is equal to or less than a predetermined value, it is determined that the instantaneous voltage drop is caused by the magnetizing inrush current of the transformer.

  According to a seventh aspect of the present invention, there is provided a magnetizing inrush current phenomenon specifying method according to the sixth aspect, wherein the system voltage before the occurrence of the instantaneous voltage drop is set as a base voltage, and the system voltage and the base voltage after the occurrence of the instantaneous voltage drop are obtained. Is obtained as a fluctuation voltage, a fluctuation basic voltage obtained by cutting the influence of transient vibration from the fluctuation voltage is obtained, and the fluctuation basic voltage is calculated during one cycle of the base voltage after the occurrence of the instantaneous voltage drop. The zero point when there is a large change from minus to plus or from plus to minus is taken as the magnetic saturation start time of the first cycle, and the fluctuation basic voltage is changed from minus to plus during the two cycles of the base voltage after the instantaneous voltage drop occurs. Alternatively, the zero point at the time of significant change from plus to minus is the second cycle magnetic saturation start time, and the first cycle magnetic saturation start time is And obtaining a magnetic saturation start time of the Me cycle.

  The method for identifying an inrush current phenomenon according to an invention of claim 8 is the invention according to any one of claims 1 to 7, wherein the instantaneous voltage drop in the power system is determined to be an instantaneous voltage drop due to the magnetizing inrush current of the transformer. In this case, it is further characterized in that it is specified whether the primary side connection of the transformer is a Δ connection or a Y connection.

  The method for specifying an inrush current phenomenon according to the invention of claim 9 is the invention according to claim 8, wherein the identification of whether the primary side connection of the transformer is a Δ connection or a Y connection is determined by the system voltage after the occurrence of the instantaneous voltage drop. The fluctuation basic voltage obtained by cutting the influence of transient vibration from the fluctuation voltage that is the difference from the base voltage that is the system voltage before the occurrence of the instantaneous voltage drop is obtained, and αβ of each phase reference is obtained as the three-phase component of the fluctuation basic voltage. The conversion is performed to obtain the α phase fluctuation basic voltage and β phase fluctuation basic voltage of each phase reference, and α phase conversion of each phase reference is performed on the three phase components of the transformer core terminal voltage, and the α phase terminal voltage of each phase reference and Obtain the β phase terminal voltage, select the reference phase that maximizes the absolute value of each of the α phase fluctuation basic voltage and the β phase fluctuation basic voltage in one cycle of the base voltage after turning on the transformer. The voltage of the base voltage after the instantaneous voltage drop occurs The zero point when a large change from minus to plus or from plus to minus is made during one cycle is the magnetic saturation start time, and the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time is the magnetic saturation midpoint time. , When the absolute value at the magnetic saturation midpoint time of the β-phase terminal voltage in the reference phase having the maximum absolute value of the β-phase fluctuation component basic voltage is below the threshold value, the primary side connection of the transformer is determined to be the Δ connection, When the absolute value of the α phase terminal voltage in the reference phase with the maximum absolute value of the α phase fluctuation component at the magnetic saturation midpoint time is less than or equal to the threshold value, the primary side connection of the transformer is determined to be the Y connection. Features.

  According to a tenth aspect of the present invention, there is provided a method for specifying an excitation inrush current phenomenon according to the eighth aspect of the invention, wherein whether the primary side connection of the transformer is a Δ connection or a Y connection is determined by the system voltage after the occurrence of the instantaneous voltage drop. The fluctuation basic voltage obtained by cutting the influence of transient vibration from the fluctuation voltage that is the difference from the base voltage that is the system voltage before the occurrence of the instantaneous voltage drop is obtained, and αβ of each phase reference is obtained as the three-phase component of the fluctuation basic voltage. The α-phase fluctuation basic voltage and β-phase fluctuation basic voltage of each phase reference are obtained by conversion, and the α-phase fluctuation basic voltage and β-phase fluctuation basic voltage in one cycle of the base voltage after the transformer is turned on. The reference phase having the maximum absolute value of each is selected, and the zero point when the basic voltage of the fluctuation greatly changes from minus to plus or from plus to minus during one cycle of the base voltage after the occurrence of the instantaneous voltage drop is magnetized. Saturation The zero point of the fluctuation basic voltage immediately after the magnetic saturation start time as the start time is the magnetic saturation midpoint time, and the α phase fluctuation basic voltage and β phase fluctuation in the reference phase of the α phase fluctuation basic voltage The basic voltage is integrated by the time width between the magnetic saturation start time and the magnetic saturation midpoint time to obtain the α-phase flux fluctuation and β-phase flux fluctuation, and the β-phase flux fluctuation is divided by the α-phase flux fluctuation. When the value is less than the threshold value, the primary side connection of the transformer is determined to be the Y connection, and the α-phase fluctuation basic voltage and β-phase fluctuation basic voltage in the reference phase of the β-phase fluctuation basic voltage are magnetized. Integrate the time width between the saturation start time and the magnetic saturation midpoint time to obtain the α-phase flux fluctuation and β-phase flux fluctuation, and the value obtained by dividing the α-phase flux fluctuation by the β-phase flux fluctuation is below the threshold. In some cases, the primary side connection of the transformer is determined to be a Δ connection.

  According to the present invention, the interlinkage magnetic flux of the transformer core focuses on the fact that the saturation start magnetic flux at the magnetic saturation start time is equal to the saturation end magnetic flux at the magnetic saturation end time, and the magnetic saturation start time and the magnetic saturation end The terminal voltage of the transformer core is integrated with the time width of the time, and the difference between the linkage flux of the transformer core at the magnetic saturation start time and the linkage flux of the transformer core at the magnetic saturation end time is obtained, and the magnetic saturation When the linkage magnetic flux of the transformer core at the start time is equal to the linkage magnetic flux of the transformer core at the magnetic saturation end time, it is determined that there is an instantaneous voltage drop due to the transformer inrush current. Even if this is not possible, the instantaneous voltage drop due to the inrush current can be determined.

  Further, when the magnetic saturation center time is estimated using the system voltage to estimate the magnetic saturation end time, it is possible to determine an instantaneous voltage drop due to the excitation inrush current in one cycle. Also, the time when the interlinkage magnetic flux of the transformer core becomes the same value as the saturation start magnetic flux is obtained, and the difference between the estimated magnetic saturation end time and the time when the interlinkage magnetic flux becomes the same value as the saturation start magnetic flux. Is within the predetermined range, it is determined that there is an instantaneous voltage drop due to the transformer inrush current, so even if the magnetizing inrush current cannot be measured, the instantaneous voltage drop due to the magnetizing inrush current can be determined in one cycle.

Even if the inrush current cannot be measured, it is possible to specify whether the primary side connection of the transformer causing the instantaneous voltage drop due to the inrush current is a Δ connection or a Y connection. It becomes easy to determine whether the source transformer is a transformer of a consumer affected by an instantaneous voltage drop or a transformer of another consumer.

  FIG. 1 is a flowchart showing an example of a method for specifying an inrush current phenomenon according to an embodiment of the present invention. It is determined whether or not an instantaneous voltage drop has occurred in a power system connected to a customer who has suffered damage from the instantaneous voltage drop (S1). This is done by installing a voltmeter in the power system connected to the customer who is damaged by the instantaneous voltage drop and monitoring the voltage of the power system.

  Here, the magnetizing inrush current generated when the transformer is connected to the power system is generated at the time of magnetic saturation of the transformer core and causes an instantaneous voltage drop in the power system. Therefore, if magnetic saturation occurs at the time of voltage fluctuation, it can be understood that this is an excitation inrush current phenomenon.

However, with respect to magnetic saturation, two saturation start flux [Phi _s, the residual magnetic flux [Phi _r is an unknown problem. Therefore, magnetic saturation start time T _s, the flux linkage of the core in magnetic saturation end time T _e [Phi (t), by noting established relationship (1).

If the above equation (1) is modified, equation (2) is obtained, and it is not necessary to know the value of the saturation start magnetic flux Φ _s .

From the electromagnetic induction law, the interlinkage magnetic flux Φ (t) of the iron core is given by the integral of the terminal voltage v (t) of the transformer core, so that the equation (2) becomes a definite integral like the equation (3), The residual magnetic flux Φ _r corresponding to the initial value becomes unnecessary.

  However, since the terminal voltage v (t) of the transformer core is the terminal voltage of the primary winding of each core leg, the transformer primary side connection is a line voltage when the Δ connection is used, and the transformer primary connection Is the phase voltage in the Y connection.

From the above, in step S2, if the instantaneous voltage drop occurs in the power system, it identifies the magnetic saturation start time T _s and magnetic saturation end time T _e (S2). Then, at step S3, (3) as shown in equation integrates the transformer core of the terminal voltage v (t) from the time range of the magnetic saturation start time Ts and the magnetic saturation end time T _e, the magnetic saturation start flux linkage transformer core of time Ts obtaining the difference between flux linkage transformer core of (saturation start flux [Phi _s) and magnetic saturation end time T _e (S3).

Then, it is determined whether or not the absolute value of the difference obtained in step S3 is equal to or less than a predetermined value (S4). Is equal to the flux linkage transformer core flux linkage and magnetic saturation end time T _e of the transformer core magnetic saturation start time T _s, usually, the difference obtained in step S3 is whether the zero Although it will be determined, it is determined whether or not the absolute value of the difference is equal to or less than a predetermined value in consideration of the error. When the absolute value of the difference obtained in step S3 is equal to or less than a predetermined value, it is determined that the current is a transformer excitation inrush current phenomenon, and is determined to be an instantaneous voltage drop due to the transformer excitation inrush current phenomenon (S5). .

Next, a description will be given estimates of the magnetic saturation start time Ts and the magnetic saturation end time T _e in step S2. Figure 2 is a flow chart showing an example of a case of estimating a magnetic saturation start time T _s and magnetic saturation end time T _e with inrush current. In the following description, the case where the primary side of the transformer is Δ-connected and the VW phase is saturated will be described as an example.

For transformer is generating exciting Japanese input current, and estimates the magnetic saturation start time T _s and magnetic saturation end time T _e in advance by the past of the current measurement data. Measurement data of the current i (t) of the transformer generating the excitation special input current is prepared (S11).

FIG. 3 is a waveform diagram showing an example of a measured waveform of the magnetizing inrush current i (t). FIG. 3A is a U-phase current i _u of the three-phase current, and FIG. 3B is a V-phase current i. _v, FIG. 3 (c) is a W-phase current _{i w.} As shown in FIG. 3, if the transformer is turned on at time t (t = 0), high-order transient vibration of about 1.2 kHz occurs immediately after time t (t = 0), and the magnetic saturation start time It can be seen that the estimation of T _s is complicated, and the current after the transformer is turned on also includes the current before the transformer is turned on, so that the current before the transformer is turned on can be obtained accurately. Separation is necessary.

Therefore, introducing (4) current by one cycle of input immediately before is defined in formula as the base current i _b. However, _{f N} is the 50Hz of commercial frequency.

The use of a base current _{i b,} for example, obtains a transformer of the input fluctuation current in the first cycle immediately after Δi (t) of from (5) (S12). Even after the second cycle determining the variation current than the difference between similarly variation current i _b.

  Furthermore, a low-pass filter is applied to the fluctuation current Δi (t) to obtain the fluctuation basic current ΔI (t) from which the transient vibration has been removed (S13).

FIG. 4 is a waveform diagram showing an example of waveforms of the W-phase variation current Δi _w (t) and the variation basic current ΔI _w (t). The dotted line in FIG. 4 is the fluctuation current Δi _w (t), and the solid line is the fluctuation basic current ΔI _w (t). As can be seen from FIG. 4, it can be seen that the magnetic saturation start time T _s and the magnetic saturation end time T _e substantially coincide with the zero point of the fluctuation basic current ΔI _w (t). That is, the magnetic saturation start time T _s is changed from a negative value to a positive value among the zero points during one cycle (t = 0 to t = 20 ms) of the base current after the fluctuation basic current ΔI _w (t) occurs. It can be seen that this is the zero point when it changes greatly from plus to minus, and the magnetic saturation end time T _e is the zero point of the most recent fluctuation basic current ΔI _w (t) after the magnetic saturation start time T _s .

Therefore, when the fluctuation basic current ΔI _w (t) greatly changes from minus to plus or from plus to minus among the zero points during one cycle (t = 0 to t = 20 ms) of the base current after the instantaneous voltage drop occurs. and zero point of the magnetic saturation start time _{T s} (S14), the latest variation basic current [Delta] I _w (t) magnetic saturation end time zero of _{T e} after magnetic saturation start time _{T s} (S15).

FIG. 5 is a waveform diagram showing an example of waveforms of the fluctuation basic current ΔI _w (t) and the flux linkage Φ (t) of the transformer core. If the transformer primary side is Δ-connected and the VW phase is saturated, the magnetic flux at the time of _{turning on} the transformer is zero, so the saturation phase interlinkage flux Φ _vw can be obtained from equation (6). .

As shown in FIG. 5, the flux linkage [Phi _vw saturation phase began affected by magnetic saturation in the magnetic saturation start time T _s, indicating a characteristic which is free from the influence of magnetic saturation in the magnetic saturation end time T _e. Then, a flux linkage [Phi _vw magnetic saturation start time _{T s1 (T s1),} it shows that magnetic saturation end time _{T e} and in the core of the flux linkages Φ _{vw (T e1)} are equal, the magnetizing inrush current phenomenon It can be seen that the conditional expression (3) is satisfied. It can also be seen that the saturation start magnetic flux Φ _vw (T _s2 ) in the second cycle after the transformer is turned on has the same value as the flux linkage Φ _vw (T _s1 ) at the magnetic saturation start time T _{s1 in} the first cycle. Thus, it can be confirmed that the flux linkage of the transformer core Φ where (t) is equal in the variation basic current [Delta] I w magnetic saturation starting time determined by the zero point of the _(t) T _s and the magnetic saturation end time T _e.

In the above description, the estimation of the magnetic saturation start time T _s and magnetic saturation end time T _e is at step S2, have been so estimated that by using the magnetizing inrush current, transformer source of magnetizing inrush current unknown the case can not estimate can not rush current measurement magnetic saturation start time T _s and magnetic saturation end time T _e. Therefore, focusing on the voltage drop in the line due to the magnetizing inrush current, the case of estimation using only the system voltage will be described.

6 is a flow chart showing an example of a case of estimating a magnetic saturation start time T _s and magnetic saturation end time T _e with system voltage. The system voltage v (t) of the power system connected to the customer who is damaged by the instantaneous voltage drop is detected (S21). Then, similarly to the case of the current i (t), the base voltage v _b1 (t) is used, and the difference between the system voltage v (t) and the base voltage v _b (t) is obtained as the fluctuation voltage Δv (t) ( S22) A low-pass filter is applied to the variation voltage Δv (t) to remove the transient vibration component to obtain the variation basic voltage ΔV (t) (S23).

  FIG. 7 is a waveform diagram showing an example in which the waveform of the fluctuation basic voltage ΔV is compared with the waveform of the fluctuation basic current ΔI. In FIG. 7, the transformer primary side is Δ-connected, and the waveform when the VW phase is saturated is shown as an example.

As can be seen from FIG. 7, the fluctuation basic voltage ΔV _vw (t) is zero at the magnetic saturation start time T _s , as with the fluctuation basic current ΔI _w (t), but the magnetic saturation end time T _e. Then there is no clear feature. This is presumed to be because the line of the power system is an RL circuit and a phase difference occurs between the fluctuation basic current ΔI _w (t) and the fluctuation basic voltage ΔV _vw (t).

Therefore, attention has been paid to the fact that the zero points of the base voltages v _{b and vw in} the saturation region of the transformer core are near the center of the saturation region. As shown in FIG. 8, the fluctuation basic current ΔI _w represents the saturation region of the transformer core, the system voltage v _vw (t) represents a value near zero at the center of the saturation region of the transformer core, and the base voltage v _{b , Vw} are zeros near the center of the saturation region of the transformer core.

It is estimated as follows that the base voltages v _{b and vw} become zero near the center of the saturation region of the transformer core. If there is no magnetizing inrush current, the interlinkage magnetic flux _Φvw of the iron core becomes the maximum amount of interlinkage magnetic flux _{Φvw, max at} the time T ′ _{c when the} base voltage v _{b, vw} (t) = 0. Therefore, it is presumed that the _maximum flux linkage Φ _{vw, max} is near the time T ′ _c even during magnetic saturation. The maximum amount of interlinkage flux Φ _{vw, max} is close to the maximum value of the fluctuation basic current ΔI _w at the center of the saturation region of the transformer core. This property is considered to hold even when the maximum amount of flux linkage Φ _{vw, max} at the time of non-saturation _{, and} the saturation region zero point of the base voltages v _{b, vw} is considered to be near the center of the region of the transformer core.

Thus, the time T ′ _c is set as the magnetic saturation midpoint time T _c . Further _{, since} the zero points of the fluctuation basic voltage ΔV and the base voltages v _{b and vw} are close to each other, the zero point of the fluctuation basic voltage ΔV can be used as the magnetic saturation midpoint time _Tc . Then, from the magnetic saturation start time T _s and the magnetic saturation midpoint time T _c , an approximate value T _{e, b} of the magnetic saturation end time T _e is obtained by Equation (7).

From the above, the zero point when the fluctuation basic voltage ΔV (t) changes greatly from minus to plus or from plus to minus is defined as the magnetic saturation start time T _s (S24). On the other hand, the zero point of the fluctuation basic voltage ΔV (t) after the magnetic saturation start time T _s , or the zero points T ′ _c of the base voltages v _{b and vw in} the saturation region of the transformer core are _represented as the magnetic saturation midpoint time T _c. and then (S25), obtains the magnetic saturation end time _{T e} by the magnetic saturation start time _{T s} and the magnetic saturation midpoint time _{T c} (7) equation (S26).

Further, instead of the expression (7), as shown in FIG. 9, after the magnetic saturation start time T _s , the interlinkage magnetic flux Φ (t) of the transformer core has the same value as the saturation start magnetic flux Φ (T _s ). The time T _{e and Φ} that have become may be used as the magnetic saturation end time T _e . In this case, when the difference between the time T _{e, b} and the time T _{e, Φ} obtained by the equation (7) is within an allowable error, it can be estimated that the excitation inrush current is the cause.

FIG. 10 is a flowchart showing another example of the method for specifying the inrush current phenomenon according to the embodiment of the present invention. In the example shown in FIG. 1, the magnetizing inrush current phenomenon is determined in one cycle of the base current i _b (t) and the base voltage v _b (t), but in the example of FIG. 10, the base voltage v _b (t The inrush current phenomenon is determined in two cycles.

As shown in FIG. 5, the saturation start magnetic flux Φ _vw (T _s2 ) in the second cycle after the transformer is _{turned on} is the same as the flux linkage Φ _vw (T _s1 ) at the magnetic saturation start time T _{s1 in} the first cycle. Paying attention to the value, it is identified as the magnetizing inrush current phenomenon by the relationship of equation (8).

Here, subscript 1 and 2 of the magnetic saturation start time T _s denotes the number of cycles after turning of the transformer.

In FIG. 10, it is determined whether or not an instantaneous voltage drop has occurred in the power system (S31). When the instantaneous voltage drop has occurred in the power system, the magnetic saturation start time T of the first transformer core is determined. obtaining magnetic saturation start time _{T s2} of the transformer core of Me _s1 and 2 cycles (S32). Then, the terminal voltage v (t) of the transformer core is integrated with the time width between the magnetic saturation start time T _s1 in the first cycle and the magnetic saturation start time T _{s2 in the} second cycle, and the magnetic saturation start time in the first cycle. obtains a difference between the flux linkage transformer core Φ _{(T s2)} of the transformer core flux linkage Φ _{(T s1)} and a 2nd cycle magnetic saturation start time _{T s2} of T _s1 (S33), 1 cycle Absolute difference between the linkage flux Φ (T _s1 ) of the transformer core at the magnetic saturation start time T _{s1 and} the linkage flux Φ (T _s2 ) of the transformer core at the second cycle magnetic saturation start time T _s2 It is determined whether the value is equal to or less than a predetermined value (S34).

The linkage magnetic flux Φ (T _s1 ) of the transformer core at the magnetic saturation start time T _{s1 in} the first cycle is equal to the linkage magnetic flux Φ (T _s1 ) of the transformer core at the magnetic saturation start time T _{s2 in} the second cycle. Therefore, normally, it is determined whether or not the difference obtained in step S33 is zero, but the determination is made based on whether or not the absolute value of the difference is equal to or less than a predetermined value in consideration of the error. When the absolute value of the difference obtained in step S33 is less than or equal to a predetermined value, it is determined that the current is a transformer excitation inrush current phenomenon, and is determined to be an instantaneous voltage drop due to the transformer excitation inrush current phenomenon (S35). .

FIG. 11 is a flowchart showing an example of estimating the first cycle magnetic saturation start time T _s1 and the first cycle magnetic saturation start time T _s2 using the system voltage. The system voltage v (t) of the power system connected to the customer who is damaged by the instantaneous voltage drop is detected (S41). Then, using the base voltage _v b (t), we obtain the difference of the system voltage v (t) and the base voltage _v b (t) as the variation voltage Δv (t) (S42), fluctuation voltage Delta] v (t) Then, a low-pass filter is applied to remove the transient vibration and the fluctuation basic voltage ΔV (t) is obtained (S43). Then, the zero point when the fluctuation basic voltage ΔV (t) greatly changes from minus to plus or from plus to minus during one cycle of the base voltage v _b (t) after the occurrence of the instantaneous voltage drop is set to the first cycle of magnetism. When the saturation start time T _s1 is set (S44) and the fluctuation basic voltage ΔV (t) changes greatly from minus to plus or from plus to minus during two cycles of the base voltage v _b (t) after the occurrence of the instantaneous voltage drop. Is set as the magnetic saturation start time T _s2 in the second cycle (S45). In this case, measurement data for two cycles of the base voltage v _b (t) after turning on the transformer is required.

  Next, a description will be given of how to connect the primary side of the transformer that has generated the magnetizing inrush current. Actually, there are many voltage measurements at consumers affected by instantaneous voltage drop, and in that case, the method of connecting the transformer of the source of the excitation inrush current is unknown. Therefore, in order to determine whether the transformer of the source of the excitation inrush current is a consumer transformer affected by the instantaneous voltage drop or the transformer of another customer, the transformer of the source of the excitation inrush current is also determined. It is essential to specify the connection method. Below, the identification method of the transformer primary side connection method of the generation source of exciting inrush current is described.

FIG. 12 is a waveform diagram showing waveforms of the transformer terminal voltage v _vw , fluctuation basic voltage ΔV _vw , and linkage flux Φ _vw when the transformer primary side is Δ-connected and the saturation phase is VW-phase. As can be seen from FIG. 12, the magnetic saturation starts at the magnetic saturation start time T _s , the interlinkage magnetic flux Φ _vw value of the transformer core is suppressed, and the terminal voltage v _vw of the transformer core abruptly approaches zero voltage. The terminal voltage v _vw of the transformer core may overshoot somewhat. This tendency continues even at the zero point T _c (linkage magnetic flux maximum time T _c ) at the voltage basic component ΔV _vw , so if the terminal voltage v _vw of the transformer is less than the threshold at time t = T _c , It can be seen that the connection method is a Δ connection.

Here, αβ conversion is applied in order to cope with a method of determining a saturated phase and a method of determining a threshold value. As shown in the equation (9), αβ conversion is performed on the three-phase fluctuation basic voltages ΔV _u , ΔV _v , ΔV _w and α of each phase reference (U-phase reference, V-phase reference, W-phase reference) A phase fluctuation basic voltage ΔV _α and a β phase fluctuation basic voltage ΔV _β are obtained.

In this example, since the transformer primary side is Δ-connected and the saturation phase is the VW phase, the current i _i flows between the V phase and the W phase. Therefore, as in the case of the VW-phase short circuit (U-phase reference), the conditions of the variation basic voltages ΔV _u , ΔV _v , ΔV _w are determined as in the following equation (10).

From the equations (9) and (10), the following relationship is obtained.

From this equation (11), the absolute value of the β-phase fluctuation component basic voltages ΔV _{β, u} , ΔV _{β, v} , ΔV _{β, w} of each phase reference (U-phase reference, V-phase reference, W-phase reference) is The basic voltage | ΔV _{β, max} | corresponding to the largest β-phase fluctuation is selected. The absolute value maximum β-phase fluctuation component basic voltage | ΔV _{β, max} | (the maximum value is important, so the absolute value symbol is omitted in the following description) is the U-phase reference ΔV _{β, u} (= 2 / √3). is there. It can be seen that the VW phase is a saturated phase since the basic voltage ΔV _{β, max} for the β phase fluctuation is based on the U phase.

Furthermore, among the α-phase fluctuation basic voltages ΔV _{α, u} , ΔV _{α, v} , ΔV _{α, w} of each phase reference (U-phase reference, V-phase reference, W-phase reference), α-phase fluctuation having the largest absolute value Minute basic voltage ΔV _{α, max} is selected. The α-phase fluctuation component voltage ΔV _{α, max with the} maximum absolute value is ΔV _{α, v} (= 1) based on the V phase or ΔV _{α, w} (= 1) based on the W phase. Now, ΔV _{α, w} (= 1) based on the W phase is selected as the α-phase fluctuation basic voltage ΔV _{α, max} having the maximum absolute value.

Then, as shown in the equation (12), a comparison is made between the β-phase fluctuation basic voltage ΔV _{β, max} with the maximum absolute value and the α-phase fluctuation basic voltage ΔV _{α, max} with the maximum absolute value.

When equation (12) holds, it can be seen that the transformer connection method is Δ connection. In this case, ΔV _{β, max} (= 2 / √3) and ΔV _{α, max} (= 1), and the difference in the reference of the magnitude comparison is about 15%. In practice, there is an influence of noise or the like, so a quantitative margin of the difference between the size comparison standards is required.

Similarly, αβ conversion is also performed on the terminal voltage v (t) of the three-phase transformer. Therefore, as shown in FIG. 13, attention is focused on the β-phase terminal voltage v _{β, u} (subscript u is the reference phase) corresponding to the β-phase variation basic voltage ΔV _{β, max} having the maximum absolute value. FIG. 13 is a waveform diagram of the β phase fluctuation component ΔV _β and the terminal voltage v _{β, u} of the transformer when the transformer connection method is Δ connection, and FIG. 14 is a waveform diagram of the transformer connection method Δ FIG. 6 is a waveform diagram of a α-phase variation basic voltage ΔV _α and a transformer terminal voltage v _{α, w} in the case of connection.

As shown in FIG. 13, the β-phase terminal voltage v _{β, u} is near zero at the magnetic saturation midpoint time (the zero point of the fluctuation basic voltage ΔV) T _c . On the other hand, the α-phase terminal voltage v _{α, w with} respect to the α-phase fluctuation basic voltage ΔV _{α, max} is a voltage peak at the magnetic saturation midpoint time (zero point of the fluctuation basic voltage ΔV) T _c as shown in FIG. It is about 1/2 of the value.

This is because the variation basic voltage ΔV is only affected by the inrush current, and the α and β phase magnetic saturation midpoint times (zero point of the variation basic voltage ΔV) T _c are the same, and the transformer terminal voltage v This is because the value varies depending on the phase even at the same time.

FIG. 15 is a vector diagram when the reference phases of the α and β phase terminal voltages of the transformer terminal voltages v _u , v _v , and v _w at the three-phase equilibrium are the U phase and the W phase, and FIG. Is a vector diagram of transformer terminal voltages v _u , v _v , and v _w at three-phase equilibrium, and FIG. 15B is a vector diagram when the reference phases of α and β phase terminal voltages are U phase and W phase. is there.

As shown in FIG. 15B, the α-phase terminal voltage v _{α, w based} on the W phase is delayed by 150 ° (5π / 6) with respect to the β-phase terminal voltage v _{β, u based on} the U phase. Accordingly, the magnetic saturation midpoint time (the zero point of the fluctuation basic voltage ΔV) T _c when the U-phase reference β-phase terminal voltage v _{β, u} is substantially zero (v _{β, u} ≈0), Equation (13) Holds.

From the equation (13), the generality of the α-phase terminal voltage v _{α, w} (T _c ) based on the W-phase is about ½ of the voltage peak value V _m . As a result, the margin increases from 15% to 50%, improving the practicality.

Next, the case of Y connection will be described. FIG. 16 is a waveform diagram showing waveforms of the variation basic voltage ΔV and the transformer terminal voltage v obtained by αβ conversion when the transformer connection method is Y connection and the W phase is saturated, and FIG. Waveform diagram of β phase fluctuation basic voltage ΔV _β and terminal voltage v _{β, u} of transformer, FIG. 16B is a waveform of α phase fluctuation basic voltage ΔV _α and transformer terminal voltage v _{α, w} . FIG.

Comparing FIG. 13 and FIG. 14 when the transformer connection method is Δ connection with FIG. 16 (a) and FIG. 16 (b), it can be seen that only the α phase and the β phase are exchanged. In the illustrated case, since the current i _i flows into the W phase and flows out of the U and V phases, the conditions of the fluctuation basic voltages ΔV _u , ΔV _v , and ΔV _w are as shown in the following equation (14). .

From the equations (14) and (9), the relationship represented by the following equation (15) is obtained.

(15) from the equation, the maximum variation is the variation basic voltage [Delta] V _w of the W-phase is saturated phase, the maximum absolute value of the alpha phase fluctuation fundamental voltage [Delta] V _{alpha, max} is naturally alpha phase variation of W-phase reference The divided basic voltage V _{α, w} . On the other hand, the β-phase fluctuation basic voltage ΔV _{β, max} having the maximum absolute value is the U-phase reference β-phase fluctuation basic voltage ΔV _β including the W-phase fluctuation basic voltage ΔV _{w ,} or the β-phase reference β phase The variation basic voltage ΔV _{β, v} is an example of the U phase. From the vector diagram of FIG. 10, the β phase terminal voltage v _{β, u based on} the U phase is the α phase terminal voltage based on the W phase. Since it is advanced by 150 ° with respect to v _{α, w} , the following equation (16) is established in the same manner as equation (13) in the relation of Δ connection.

From the equation (16), the generality of the U-phase reference β-phase terminal voltage v _{β, u} (T _c ) is about ½ of the voltage peak value V _m . As a result, in the case of Y connection, the margin increases from 15% to 50%, as in the case of Δ connection, and the practicality is improved.

FIG. 17 is a flowchart showing an example of a method for specifying the transformer primary-side connection method that is the source of the excitation inrush current. Three-phase fluctuation basic voltages ΔV _u , ΔV _v , ΔV _w are obtained (S 51). As described above, the three-phase fluctuation basic voltages ΔV _u , ΔV _v , and ΔV _w are the three-phase system voltage v after the occurrence of the instantaneous voltage drop and the three-phase base voltage that is the system voltage before the occurrence of the instantaneous voltage drop. It is obtained by applying a low-pass filter from the fluctuation voltage Δv that is the difference from v _b to cut the influence of transient vibration.

The three-phase components of the three-phase fluctuation basic voltages ΔV _u , ΔV _v , and ΔV _w are subjected to αβ conversion of each phase reference by the equation (9), and each phase reference (U-phase reference, V-phase reference, W Phase reference) basic phase voltages ΔV _{α, u} , ΔV _{α, v} , ΔV _{α, w} and β phase variation basic voltages ΔV _{β, u} , ΔV _{β, v} , ΔV _{β, w} (S52) .

Similarly, αβ conversion of each phase reference is performed on the three-phase components of the terminal voltages v _u , v _v , v _w of the three-phase transformer core by the equation (9), and each phase reference (U-phase reference, Α phase terminal voltages v _{α, u} , v _{α, v} , v _{α, w} and β phase fluctuation basic voltages v _{β, u} , v _{β, v} , v _{β, w} are obtained. (S53).

Then, select the respective maximum absolute value becomes the reference phase of the base voltage v alpha phase fluctuation fundamental voltage in one cycle period of the _b [Delta] V _alpha and beta phase fluctuation fundamental voltage [Delta] V _beta after the transformer is turned (S54).

On the other hand, the zero point when the fluctuation basic voltage ΔV changes greatly from minus to plus or from plus to minus during one cycle of the base voltage v _b after the occurrence of the instantaneous voltage drop is defined as the magnetic saturation start time T _s. the last zero of fluctuation fundamental voltage ΔV after the start time T _s to the magnetic saturation midpoint time T _c (S55).

Then, the magnetic saturation midpoint time T _c of the β-phase terminal voltage v _{β, u} when the β-phase fluctuation basic voltage ΔV _β (for example, β-phase fluctuation basic voltage ΔV _{β, u} ) having the maximum absolute value is the reference phase. It is determined whether or not the absolute value v _{β, u} (T _c ) is equal to or less than a threshold value (S56). This corresponds to determining whether or not the β-phase terminal voltage v _{β, u} (T _c ) in FIG. 13 is near zero. If the β-phase terminal voltage v _{β, u} (T _c ) is less than or equal to the threshold value, it is determined that the connection of the transformer is a Δ connection (S57).

On the other hand, if it is determined in step S56 that the β-phase terminal voltage v _{β, u} (T _c ) is not less than or equal to the threshold value, the α-phase variation basic voltage ΔV _α (for example, the α-phase variation basic voltage ΔV _{α having the} maximum absolute value). _{, W} ) is a reference phase, it is determined whether or not the absolute value v _{α, w} (T _c ) at the magnetic saturation midpoint time T _c of the α-phase terminal voltage v _{α, w} is equal to or less than a threshold value (S58). This corresponds to determining whether or not the α-phase terminal voltage v _{α, w} (T _c ) in FIG. When the α-phase terminal voltage v _{α, w} (T _c ) is equal to or less than the threshold value, it is determined that the connection of the transformer is the Y connection (S59).

In the above description, as a method of wiring the transformer, the three-phase fluctuation basic voltage ΔV is αβ converted to obtain the α-phase fluctuation basic voltage ΔV _α and β-phase fluctuation basic voltage ΔV _β having the maximum absolute value. The values v _{α, w} (T _c ), v _{β, u} (T _c ) of the α-phase terminal voltage v _{α, w} and β-phase terminal voltage v _{β, u} corresponding to them at the magnetic saturation midpoint time T _c are obtained. Based on the above, it is determined whether the method is the Δ connection method or the Y connection method. As another index, the α phase fluctuation amount basic is _{calculated based on} the U phase reference of the β phase fluctuation basic voltage ΔV _{β, max in} the equation (11). Focusing on the voltage ΔV _{α, u} (= 0) and taking into account that the noise error is reduced in an integral manner, the index γ can be defined by the following equation (17).

If the index γ _β is less than or equal to the threshold value, it is estimated as Δ connection, and conversely if the index γ _α is less than or equal to the threshold value, it is estimated as Y connection. By the way, an index obtained based on the phase of the α-phase variation basic voltage ΔV _{α, max} with the maximum absolute value and the β-phase variation basic voltage ΔV _{β, max} with the maximum absolute value shown in FIG. The γ values are compared and displayed in Table 1.

FIG. 19 is a flowchart showing an example of specifying the transformer primary side connection method of the source of the inrush current by using the index defined by the equation (17). Three-phase fluctuation basic voltages ΔV _u , ΔV _v , ΔV _w are obtained (S 61). As described above, the three-phase fluctuation basic voltages ΔV _u , ΔV _v , and ΔV _w are the three-phase system voltage v after the occurrence of the instantaneous voltage drop and the three-phase base voltage that is the system voltage before the occurrence of the instantaneous voltage drop. It is obtained by applying a low-pass filter from the fluctuation voltage Δv that is the difference from v _b to cut the influence of transient vibration. The three-phase components of the three-phase fluctuation basic voltages ΔV _u , ΔV _v , and ΔV _w are subjected to αβ conversion of each phase reference by the equation (9), and each phase reference (U-phase reference, V-phase reference, W Phase reference) basic voltage ΔV _{α, u} , ΔV _{α, v} , ΔV _{α, w} and β phase fluctuation basic voltage ΔV _{β, u} , ΔV _{β, v} , ΔV _{β, w} (S62) .

Then, the reference phase having the maximum absolute value of each of the α-phase fluctuation basic voltage ΔV _α and the β-phase fluctuation basic voltage ΔV _β is selected in one cycle of the base voltage v _b after the transformer is turned on (S63). On the other hand, the zero point when the fluctuation basic voltage ΔV changes greatly from minus to plus or from plus to minus during one cycle of the base voltage v _b after the occurrence of the instantaneous voltage drop is defined as the magnetic saturation start time T _s. as recent variation basic voltage magnetic saturation midpoint time T _c of the zero point of ΔV after the start time T _s, determine the magnetic saturation start time T _s and magnetic saturation midpoint time T _c (S64).

Next, alpha-phase fluctuation fundamental voltage [Delta] V _alpha and alpha phase fluctuation fundamental voltage [Delta] V _alpha and beta phase fluctuation fundamental voltage [Delta] V _beta magnetic saturation start time T _s and the magnetic saturation midpoint time T _c of the reference phase The α phase magnetic flux fluctuation amount ΔΦ _α and the β phase magnetic flux fluctuation amount ΔΦ _β are obtained by integration with the time width (S65). It is determined whether or not the value obtained by dividing the β-phase magnetic flux variation ΔΦ _β by the α-phase magnetic flux variation ΔΦ _α is equal to or smaller than the threshold ε1 (S66). It determines with it being a connection (S67).

On the other hand, if it is not less than the threshold value ε1 in the determination of step S66, the α-phase variation basic voltage ΔV _α and the β-phase variation basic voltage ΔV _{β in} the reference phase of the β-phase variation basic voltage ΔV _β are set to the magnetic saturation start time T. _The α phase magnetic flux fluctuation amount ΔΦ _α and the β phase magnetic flux fluctuation amount ΔΦ _β are obtained by integrating with the time width between _s and the magnetic saturation midpoint time _Tc (S68). It is determined whether or not the value obtained by dividing the α-phase magnetic flux variation ΔΦ _α by the β-phase magnetic flux variation ΔΦ _β is equal to or smaller than the threshold ε2 (S69). It determines with it being a connection (S70).

According to the embodiment of the present invention, the flux linkage of the transformer core [Phi (t), it saturated End flux at saturation start flux and magnetic saturation end time T _e of the magnetic saturation start time T _s is equal to focusing on integrates the transformer core of the terminal voltage v (t) from the time range of the magnetic saturation start time T _s and the magnetic saturation end time T _e, the transformer core magnetic saturation start time T _s interlinkage It obtains a difference between the flux linkage transformer core flux and magnetic saturation end time T _e, so determining the difference between when the predetermined value or less is a momentary voltage drop due to transformer inrush current of the transformer, the transformer inrush Even when the current cannot be measured, the instantaneous voltage drop due to the inrush current can be determined.

  Using the difference between the base voltage, which is one cycle of the voltage just before the occurrence of the instantaneous voltage drop, and the voltage after the occurrence of the instantaneous voltage drop, and further, the basis of the fluctuation that cuts the influence of transient vibration caused by turning on the transformer with a low-pass filter When the voltage is obtained and the time of zero fluctuation of the basic voltage for the first cycle is the magnetic saturation start time, the flux linkage at that time and the value of the flux linkage at the second magnetic saturation start time are equal Since the cause of the instantaneous voltage drop is determined to be the inrush current, the instantaneous voltage drop due to the inrush current can be determined even when the inrush current cannot be measured.

Further, as a method for discriminating the instantaneous voltage drop due to the inrush current by only the voltage measurement data for one cycle, since the zero crossing time _Tc between the base voltage and the saturation region is near the center of the saturation region, T _e ≈T _s +2 (T c _{-T s)} and approximate, whereas, since the flux linkage [Phi (Ts) and the time the same value of [Phi also considered T _e, the difference between the two T _e values are within tolerance Sometimes it can be determined that the inrush current is the cause.

Furthermore, since the aspect of the phenomenon differs depending on the primary side connection (Δ winding, Y winding) of the transformer in which the magnetizing inrush current phenomenon has occurred, in order to identify the primary side connection, first, the three-phase component Αβ conversion of each phase is performed to obtain three types of ΔV _α and ΔV _β . Similarly, the system voltage v is also αβ converted to obtain three types of voltages v _α and v _β. To select the reference phase that maximizes the absolute value of the ΔV extreme value of each of the α-phase fluctuation basic voltage ΔV _α and β-phase fluctuation basic voltage ΔV _β . For example, ΔV _β in the reference phase having the maximum absolute value of ΔV _β , V _β , and Δ connection is made when the absolute value of v _β (T _c ) is less than or equal to the threshold value. On the other hand, the absolute value of v _α (T _c ) is less than the threshold value in the reference phase having the maximum absolute value of ΔV _α . In case of Y connection, the transformer of the source of the excitation inrush current is affected by the instantaneous voltage drop or other transformer It is easy to determine whether the transformer is a consumer.

The flowchart which shows an example of the magnetizing inrush current phenomenon identification method concerning embodiment of this invention. The flowchart which shows an example in the case of estimating a magnetic saturation start time and a magnetic saturation end time using an exciting inrush current by an example of the exciting inrush current phenomenon specific method concerning embodiment of this invention. The wave form diagram which shows an example of the measurement waveform of an excitation inrush current. The wave form diagram which shows an example of the waveform of the fluctuation | variation part current of a W phase of a magnetizing inrush current, and a fluctuation part basic current. The wave form diagram which shows an example of the waveform of the fluctuation | variation basic current for a fluctuation | variation of excitation inrush current, and the interlinkage magnetic flux of a transformer core. The flowchart which shows an example in the case of estimating a magnetic saturation start time and a magnetic saturation end time using a system | strain voltage by an example of the excitation inrush current phenomenon specific method concerning embodiment of this invention. The wave form diagram of an example which showed the waveform of the fluctuation | variation basic voltage for excitation inrush current compared with the waveform of fluctuation | variation basic current. The wave form diagram which shows an example of the waveform of the base current in the saturation area | region of a transformer iron core, the fluctuation | variation of a magnetizing inrush current, and a terminal voltage. The waveform figure of an example which showed the waveform of the fluctuation | variation basic voltage for the fluctuation | variation of excitation inrush current compared with the waveform of the interlinkage magnetic flux of a transformer core. The flowchart which shows another example of the magnetizing inrush current phenomenon specific method concerning embodiment of this invention. Another example of the method for specifying the magnetizing inrush current phenomenon according to the embodiment of the present invention shows an example of estimating the first cycle magnetic saturation start time and the first cycle magnetic saturation start time using the system voltage. flowchart. The wave form diagram which shows the waveform of the terminal voltage of a transformer, a fluctuation | variation basic voltage, and a linkage magnetic flux in case a transformer primary side is (DELTA) connection and a saturation phase is a VW phase. The wave form diagram of the fluctuation | variation basic voltage of a beta phase in case the connection method of a transformer is (DELTA) connection, and the terminal voltage of a transformer. The wave form diagram of the variation | change_quantity basic voltage of an alpha phase in case the connection method of a transformer is (DELTA) connection, and the terminal voltage of a transformer. The vector figure in case the reference phase of the alpha and beta phase terminal voltage of the transformer terminal voltage at the time of three-phase equilibrium is U phase and W phase. The wave form diagram which shows the waveform of the fluctuation | variation basic voltage which carried out (alpha) (beta) conversion, and the terminal voltage of a transformer when the connection method of a transformer is Y connection and a W phase is saturated. The flowchart which shows an example of the specific method of the transformer primary side connection method of the generation source of an excitation inrush current. The waveform diagram calculated | required on the basis of the phase of the (alpha) phase fluctuation | variation basic voltage with the largest absolute value, and the (beta) phase fluctuation | variation basic voltage with the largest absolute value. The flowchart which shows an example which specifies the transformer primary side connection method of the generation source of a magnetizing inrush current using the parameter | index defined by (17) Formula.

Explanation of symbols

T _s ... Magnetic saturation start time, T _e ... Magnetic saturation end time, f _N ... Commercial frequency, Φs ... Saturation start magnetic flux, v (t) ... Voltage, Φ (t) ... Interlinkage magnetic flux, i _b ... Base current, Δi, fluctuation current, ΔI, fluctuation basic current, v _b, base voltage, Δv, fluctuation voltage, ΔV fluctuation basic voltage, T _c, magnetic saturation midpoint time, ΔV _α, α phase fluctuation basic voltage, ΔV _β … Basic voltage for β phase fluctuation

Claims (10)

  When instantaneous voltage drop occurs in the power system, the magnetic saturation start time and magnetic saturation end time of the transformer core are obtained, and the terminal voltage of the transformer core is integrated by the time width between the magnetic saturation start time and the magnetic saturation end time. Find the difference between the linkage flux of the transformer core at the magnetic saturation start time and the linkage flux of the transformer core at the magnetic saturation end time, and transform the linkage flux of the transformer core at the magnetic saturation start time and the magnetic saturation end time. An inrush current phenomenon identification method for determining an inrush current phenomenon characterized by determining that the voltage drop is caused by an inrush current of a transformer when the interlinkage magnetic flux of the iron core is equal.   The transformer primary current before the occurrence of the instantaneous voltage drop is defined as a base current, the difference between the transformer primary current after the occurrence of the instantaneous voltage drop and the base current is obtained as a variation current, and the influence of transient vibration from the variation current The fluctuation basic current is calculated, and the magnetic saturation starts at the zero point when the fluctuation basic current changes greatly from minus to plus or from plus to minus during one cycle of the base current after the instantaneous voltage drop occurs. The magnetic saturation start time and the magnetic saturation end time of the transformer core are obtained by setting the time as the time, and the zero point of the fluctuation basic current immediately after the magnetic saturation start time as the magnetic saturation end time. The method for identifying the inrush current phenomenon described.   The system voltage before the occurrence of the instantaneous voltage drop is set as a base voltage, the difference between the system voltage after the occurrence of the instantaneous voltage drop and the base voltage is obtained as a fluctuation voltage, and the fluctuation obtained by cutting the influence of transient vibration from the fluctuation voltage And the zero point when the fluctuation basic voltage changes greatly from minus to plus or from plus to minus during one cycle of the base voltage after occurrence of the instantaneous voltage drop is defined as the magnetic saturation start time, The magnetic saturation end time is obtained from the magnetic saturation start time and the magnetic saturation midpoint time, with the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time as the magnetic saturation midpoint time. Item 2. A method for identifying an inrush current phenomenon according to Item 1.   When an instantaneous voltage drop occurs in the power system, a difference between the system voltage after the occurrence of the instantaneous voltage drop and the base voltage is obtained as a fluctuation voltage using the system voltage before the occurrence of the instantaneous voltage drop as a base voltage, and the fluctuation voltage The fluctuation basic voltage from which the influence of the transient vibration is cut is obtained from the fluctuation, and the fluctuation basic voltage greatly changes from minus to plus or from plus to minus during one cycle of the base voltage after the instantaneous voltage drop occurs. The zero point is the magnetic saturation start time, the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time is the magnetic saturation midpoint time, and the magnetic saturation ends from the magnetic saturation start time and the magnetic saturation midpoint time On the other hand, the time when the interlinkage magnetic flux of the transformer core becomes the same value as the saturation start magnetic flux is obtained, and the difference between this time and the magnetic saturation end time is within a predetermined range. Magnetizing inrush current phenomenon specific method characterized by determining a certain time is the instantaneous voltage drop due to transformer inrush current of the transformer.   The magnetic saturation midpoint time is set to the zero point of the base voltage in the saturation region of the transformer core, instead of being the zero point of the most recent fluctuation basic voltage after the magnetic saturation start time. 5. A method for identifying an inrush current phenomenon according to claim 3 or 4, characterized in that:   When an instantaneous voltage drop occurs in the power system, the magnetic saturation start time of the first transformer core and the magnetic saturation start time of the second transformer core are obtained, and the first magnetic saturation start time and the second cycle The terminal voltage of the transformer core is integrated with the time span of the magnetic saturation start time of the current and the linkage flux of the transformer core at the first cycle of magnetic saturation and the transformer core at the second cycle of magnetic saturation start time are integrated. The difference between the linkage magnetic flux is obtained, and the difference between the linkage flux of the transformer core at the first magnetic saturation start time and the linkage flux of the transformer core at the second magnetic saturation start time is less than a predetermined value. A method for identifying an inrush current phenomenon, characterized in that it is determined that an instantaneous voltage drop is caused by an inrush current of a transformer.   The system voltage before the occurrence of the instantaneous voltage drop is set as a base voltage, the difference between the system voltage after the occurrence of the instantaneous voltage drop and the base voltage is obtained as a fluctuation voltage, and the fluctuation obtained by cutting the influence of transient vibration from the fluctuation voltage The basic voltage is obtained, and when the fluctuation basic voltage changes greatly from minus to plus or from plus to minus during one cycle of the base voltage after the occurrence of the instantaneous voltage drop, the zero point starts magnetic saturation for the first cycle. Time, and the zero point when the basic voltage changes greatly from minus to plus or from plus to minus during two cycles of the base voltage after the occurrence of the instantaneous voltage drop is set as the second cycle magnetic saturation start time, 6. The excitation according to claim 5, wherein a magnetic saturation start time for the first cycle and a magnetic saturation start time for the second cycle are obtained. Input current phenomenon specific way.   When it is determined in the power system that the instantaneous voltage drop is an instantaneous voltage drop due to the inrush current of the transformer, it is further specified whether the primary connection of the transformer is a Δ connection or a Y connection. Item 8. The method for specifying an inrush current phenomenon according to any one of Items 1 to 7.   The identification of whether the primary side connection of the transformer is a Δ connection or a Y connection is based on a fluctuation voltage that is a difference between the system voltage after the occurrence of the instantaneous voltage drop and the base voltage that is the system voltage before the occurrence of the instantaneous voltage drop. Obtain the fluctuation basic voltage that eliminates the effects of transient vibration, and perform αβ conversion of each phase reference to the three-phase component of the fluctuation basic voltage to obtain the α phase fluctuation basic voltage and β phase fluctuation basic voltage of each phase reference. , Αβ conversion of each phase reference is performed on the three-phase component of the transformer core terminal voltage to obtain the α phase terminal voltage and β phase terminal voltage of each phase reference, and α in the section of one cycle of the base voltage after the transformer is turned on A reference phase having a maximum absolute value of each of the phase fluctuation basic voltage and the β phase fluctuation basic voltage is selected, and the fluctuation basic voltage is changed from minus to plus during one cycle of the base voltage after occurrence of the instantaneous voltage drop. Large change from positive to negative The zero point of time is the magnetic saturation start time, the zero point of the fluctuation basic voltage immediately after the magnetic saturation start time is the magnetic saturation midpoint time, and the β-phase fluctuation basic voltage is at the reference phase with the maximum absolute value. When the absolute value of the β-phase terminal voltage at the magnetic saturation midpoint time is less than or equal to the threshold value, the primary side connection of the transformer is determined to be a Δ connection, and the α-phase fluctuation component α is a reference phase having a maximum absolute value. 9. The method according to claim 8, wherein when the absolute value of the phase terminal voltage at the magnetic saturation midpoint time is equal to or less than a threshold value, the primary side connection of the transformer is determined as a Y connection.   The identification of whether the primary side connection of the transformer is a Δ connection or a Y connection is based on a fluctuation voltage that is a difference between the system voltage after the occurrence of the instantaneous voltage drop and the base voltage that is the system voltage before the occurrence of the instantaneous voltage drop. Obtain the fluctuation basic voltage that eliminates the effects of transient vibration, and perform αβ conversion of each phase reference to the three-phase component of the fluctuation basic voltage to obtain the α phase fluctuation basic voltage and β phase fluctuation basic voltage of each phase reference. The reference phase having the maximum absolute value of each of the α phase fluctuation basic voltage and the β phase fluctuation basic voltage is selected in one cycle of the base voltage after the transformer is turned on, and the fluctuation basic voltage decreases the instantaneous voltage. The zero point at which the base voltage changes greatly from minus to plus or from plus to minus during one cycle of the base voltage after generation is defined as the magnetic saturation start time, and the zero point of the most recent fluctuation basic voltage after the magnetic saturation start time. The magnet As the saturation midpoint time, the α phase fluctuation basic voltage and β phase fluctuation basic voltage in the reference phase of the α phase fluctuation basic voltage are integrated by the time width between the magnetic saturation start time and the magnetic saturation midpoint time, and α When the value obtained by dividing the phase flux fluctuation and the β phase flux fluctuation by dividing the β phase flux fluctuation by the α phase flux fluctuation is equal to or less than the threshold value, the transformer primary side connection is determined to be the Y connection. The β phase fluctuation basic voltage and the β phase fluctuation basic voltage in the reference phase of the β phase fluctuation basic voltage are integrated by the time width between the magnetic saturation start time and the magnetic saturation midpoint time, and the α phase magnetic flux fluctuation amount and The β-phase flux fluctuation is obtained, and when the value obtained by dividing the α-phase flux fluctuation by the β-phase flux fluctuation is equal to or less than the threshold value, it is determined that the primary side connection of the transformer is a Δ connection. The method for identifying an inrush current phenomenon according to claim 8.

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