JPS644411B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device that detects lightning strikes in distribution substations and causes disaster-prevention power outage of distribution lines. The zero-sequence voltage waveforms obtained from the zero-sequence transformers are similar and there is a certain relationship between the zero-sequence current obtained from the zero-sequence current transformer of the distribution line that has been induced by a lightning strike and the zero-sequence voltage. The purpose is to detect lightning surges using the output of conventional zero-phase transformers (GPTs) and zero-phase current transformers (ZCTs) without the need for special detection sensors. It lies in making it possible.

Conventional lightning warning devices include systems that receive aerial pulses generated by lightning discharges and measure ground electric field strength, but in both cases, antenna devices are required, so the device It was something special in itself. In addition, there are devices to measure the point of lightning strike, such as by calculating the ratio of the electric field and magnetic field, or by receiving lightning and air surges at each electrical station and calculating them based on the time difference between the arrival of the lightning and air surges. The device itself would be special, and there is no possibility that it would be possible to perform an emergency power outage on distribution lines near the lightning strike point.

The present invention has been made in view of this point,
Based on the conditions obtained from the existing equipment of the distribution substation, such as zero-phase transformers and zero-phase current transformers, it is possible to detect lightning strikes in the entire substation, and to detect nearby distribution lines that have been struck by lightning. We propose a device that has the ability to shut off power outage in case a failure is predicted. We also propose an induced lightning surge detection device that uses zero-sequence voltage and zero-sequence current as inputs, making it easy to add a directional ground fault detection function that detects ground faults in distribution lines from the same input. be.

The present invention will be described in detail below with reference to the drawings.

Figure 1 shows multiple lightning in the case of negative polarity thunderclouds and nearby lightning strikes at an arbitrary point on the line conductor at height h (P in the figure).
This figure shows the temporal changes in induced lightning surges that occur during the period. a in Figure 1B is the surge due to the main discharge,
b indicates a surge caused by a restrained charge caused by a thundercloud, L indicates a surge caused by a preceding discharge, R indicates a surge caused by superimposing a and b, and D indicates a surge caused by a cascading preceding discharge. As shown in the figure, when lightning strikes nearby, the induced lightning surge becomes a bipolar surge, and its magnitude differs depending on the position of point P.

FIG. 2 is a configuration example of a distribution substation conceptually illustrating the present invention, in which 1 is the main transformer, 2 ₁ to 2 _o+1 beams and disconnectors, 3 is the bus bar, and 4 ₁ to 4 _o is distribution line, 5 ₁ ~
5 _o is a zero-phase current transformer, 6 is a zero-phase transformer, and 7 is an induced lightning surge detection device of the present invention. Distribution line 4 ₁ ~ 4 _o
The waves run radially around the substation, and if a lightning strike occurs near any distribution line, the voltage of each phase will become a waveform in which bipolar surges are superimposed, including on the busbar, and the zero-sequence voltage will become a waveform in which bipolar surges are superimposed on each phase. Similar to bipolar surge. Therefore, in order to detect a lightning strike in a substation all at once, it is sufficient to detect that the zero-sequence voltage is a bipolar surge (including the waveform of a bipolar surge). The validity of the above will be shown below based on actual measurement results.

FIG. 3A shows the results of measuring the ground voltage of each phase, a phase, b phase, and c phase, at the outlet of the distribution line 4 _i in FIG. 2. This figure shows that induced lightning surges enter each phase of the distribution line at the same time, and the peak values and waveforms are almost the same. The induced lightning surge superimposed on the a-phase in this case is as shown in FIG. 3B, and is a bipolar surge. This occurs when a nearby lightning strike occurs at a point adjacent to a power distribution line. In addition, the results of observing induced lightning surges when the measurement line is out of power show that bipolar surges occur even when lightning strikes near the measurement line, and the negative polarity portion of the bipolar surge decreases as the lightning strike point becomes further away from the measurement line. It has been confirmed that when the surge is completely far away, it becomes a unipolar surge with only the positive polarity part and no negative polarity part.

In addition, the peak value of induced lightning surges tends to be lower than the shock insulation withstand voltage of the structures installed on the lines, but the reason for this is that the potential distribution of induced lightning surges that occur on distribution lines is Rather than being distributed, it shows a steep distribution centered around the lightning strike point, and it is thought that the induced lightning surge that enters the distribution line outlet will be low even if there is no flash fault on the line structure.

FIG. 3C shows a flashflash waveform of an induced lightning surge, and D shows a waveform that leads to an instantaneous failure due to a flashflash, and the flashflash occurs in the negative polarity portion of a bipolar surge. This flash fault is caused by structures installed on each pole of each distribution line.
It is thought that it depends on BIL (Basic Insulation Level).

Figures 4A and 4B show a comparison between the induced lightning surge waveforms shown in Figures 3B and D and the zero-sequence voltage (V ₀ surge) obtained from the zero-phase transformer 6 shown in Figure 2.
Figure A shows the case without flash faults, and B shows the case with flash faults, both of which are in good agreement. Therefore, induced lightning surge can be obtained from a zero-phase transformer.

Figure 5 shows the zero-sequence voltage obtained from the zero-phase transformer 6 during multiple lightning strikes in the vicinity of the distribution line 4 ₁ and the zero-phase current transformer 5 of each distribution line (4 ₁ to 4 ₅ , n=5). ₁ to ₅₅ shows the relationship between zero-sequence currents I ₀₁ to _{I 05} . Because of this relationship, the value of the zero-sequence current in the distribution line near the lightning strike point is large, and the polarity is opposite to that of other distribution lines. This can be considered similar to a normal ground fault. Therefore, on the condition that the zero-sequence voltage is an induced lightning surge, by comparing the absolute value or polarity of the zero-sequence current of each distribution line, it is possible to detect a distribution line near a lightning strike.

FIG. 6 shows an embodiment in which the induced lightning surge detection device 7 in FIG. 2 is constructed with a digital processing device in consideration of the above.

The inputs V ₀ , I ₀₁ to _{I 0o} are information obtained from the zero-phase transformer 6 and zero-phase current transformers 5 ₁ to 5 _o in FIG. ₀ to 8 _o , are sequentially A/D converted by a multiplexer (MPX) 9 and an A/D converter 10 to become digital data, and are DMAed to a memory 11 . The CPU 12 performs predetermined arithmetic processing using the data stored in the memory 11 and outputs the result through the I/O 13. The setting I/F 14 performs setting necessary for processing.

FIG. 7 shows the A/D converted input V ₀ or I ₀₁ ~
This shows how N samples of I _0o are DMAed at once, and the CPU processing is completed within NΔt. Note that Δt represents the sampling interval.

FIG. 8 is a block diagram showing the processing of the CPU 12.

In step S1, the instantaneous data of the DMA input information _V0 is fetched from the memory 11. Step S2 detects the level of the input information of step S1, step S3 processes whether V ₀ in a certain section T is a bipolar surge (including a flash waveform), and step S4 detects the level of the input information of step S1.
Based on the result, it is determined whether V ₀ is a bipolar surge, step S5 is to determine whether V ₀ has detected a bipolar surge N times within time T ₁ , and step S6 is to generate a lightning warning. Notify of lightning strikes near each power distribution line. Step S7 determines whether no bipolar surge has been detected within the time period _T2 since the last bipolar surge was recognized, and step S8 cancels the lightning warning and indicates that the thundercloud has moved away from the substation. Let them know what happened.

In step S9, the instantaneous data of the DMA input information _I0i is fetched from the memory. Step S10 detects the level of the input information of S9, and step S11 detects the level of the input information of S9.
The polarity of T _0i is determined, and step S12 determines whether there is a lightning strike near the distribution line 4i (Fig. 2) based on the result of S11, and step S13 determines whether or not the distribution line 4i will fail. Then, as an example, a continuity determination is made to determine whether or not it has been repeated M times, and a step S14 issues a trip command to the power distribution line 4i. In step S15, it is determined that i=n. Eventually step S9
Process A of ~S15 will be performed from i=1 to ~n.

In process B, step S16 adds the absolute value of the input information of step S9A, which is the same as step S9, step S17 adds the absolute value of _I0i in interval T, and step S18 adds the absolute value of the input information of step S9A, which is the same as step S9, and step S18 adds the absolute value of the input information of step S9A, which is the same as step S9. Based on this, it is determined in step S19 that there is a possibility of a lightning strike near the distribution line 4i. Step S20
compares the absolute values determined to be likely to be struck by nearby lightning in step S19, which went through the same S15A as S15, and determines the distribution line with the largest absolute value. step
No in S20 means that the process in S19 is not performed.
After the processing in step S20, a trip command is obtained through steps S13A and S14A similar to S13 and S14.

FIG. 9 shows the relationship between the input waveform diagram and the input in the flow of FIG. 8. This is a case where N=2 and M=3, and the distribution line 3i has broken down due to a lightning strike. In the figure, V ₀ , I _0i , and I _0j are input information,
The bipolar surge output is obtained from the judgment in step S4 in Figure 8, and the feeder output is obtained from step S12 or
Obtained from S20's judgment. The lightning warning output is processed in step S6, and the trip command is processed in step S6.
Due to processing of S14 and S14A.

FIG. 10 is a diagram for explaining the processing of steps S2 and S10 (level detection processing) in FIG.
As an example, V ₀ will be described. The time point at which DMA is performed is defined as the current time, and the level of the input information of the previous T interval is detected using certain slice levels V ₊ and V _- . When the input data v ₀ is v ₀ ≧V ₊ , it is positive, when v ₀ ≦−V ₋ , it is negative, and when −V ₋ < v ₀ < V ₊ , it is zero. n _OF is the number of samplings between the first (zero) circles in the T interval, n _- is the number of samplings in the first (negative) interval, n _pn is the number of samplings in the second (zero) interval, and n ₊ is the number of samplings in the first (negative) interval. The number of samples in the (correct) interval, n _OB indicates the number of samples in the last (zero) interval. Note that the current time changes every time interval NΔt.

FIG. 11 is a diagram for explaining the processing (polarity determination processing) in steps S3 and S11 in FIG. 8. As an example, v ₀ in FIG. 10 is a bipolar surge (not including a flash waveform). The flow of determining whether or not
In step SS1, it is determined that n _OF ≧N _OF (setting value), and it is confirmed that (zero) is continuous at the beginning of section T. In step SS2, it is determined that n _OB ≧N _OB and at the end of section T. Also check that (zero) is continuous.
SS3 determines that the first (zero) interval is followed by a (negative) interval, SS4 determines that n _- ≧ N _- and confirms that (negative) is continuous, and SS5 determines that this (negative) Interval followed by (zero) interval or (positive)
Confirm that the interval continues and use SS6 to find N _pn ≦N _OM
By determining whether there is a second (zero) interval,
Or make sure it's short, then by SS7, n ₊
Make a judgment of ≧N ₊ and confirm that (correct) results are continuous. If all the judgments from SS1 to SS7 are yeS, the waveform of this T interval is determined to be a bipolar surge by SS8, and if any of the judgments from SS1 to SS7 is n _p , the waveform of this T interval is determined by SS9. It is determined that it is not a bipolar surge. Incidentally, the flash waveform can also be detected in a similar manner.

Finally, we will discuss the case where a directional ground fault detection function is added. Figure 12A shows the case where the directional ground fault detection device 7 ₁ and the induced lightning surge detection device 7 ₂ are separate hardware, and the final output is determined by the logical sum of the trip command output of 7 ₁ and the trip command output of 7 ₂ . This is the case of the induced lightning surge detection device ₇₃ obtained.

FIG. 12B shows a case where a directional ground fault detection function is added while leaving the hardware configuration of FIG.
S23 is induced lightning surge detection processing, S24 is its output,
S25 is the case of an induced lightning surge detection device in which the final output is determined by the OR operation of S22 and S24.

The above explanation is for the case where the thundercloud has negative polarity, but when the thundercloud has positive polarity, the present invention can be applied by simply reversing the polarity of V ₀ and I _0i .

As described above, according to the present invention, it is possible to estimate from the zero-sequence voltage waveform and zero-sequence current waveform of the distribution line branching from the bus bar whether or not the distribution line will malfunction.
It is possible to prevent damage to distribution line equipment, disconnection, etc., and there is no need for special equipment to detect lightning strikes.

[Brief explanation of drawings]

Figure 1 is an induced lightning surge waveform diagram of multiple lightning when a thundercloud has negative polarity, Figure 2 is a single line diagram of a distribution substation, Figure 3 is a diagram showing an actual measurement example of an induced lightning surge waveform, and Figure 4 is a diagram showing an example of the induced lightning surge waveform. The figure is a comparison diagram of the induced lightning surge waveform and the V ₀ surge waveform, Figure 5 is a diagram showing an actual measurement example of the V ₀ surge waveform and the I ₀ surge waveform, and Figure 6 is a hardware configuration diagram of an embodiment of the present invention. Fig. 7 is a diagram showing the DMA method, Fig. 8 is a flowchart showing the processing contents of CPU, Fig. 9 is a diagram showing the input waveform and output relationship in the present invention, and Fig. 10 is for explaining level detection. 11 is a flowchart for detecting a bipolar surge, and FIG. 12 is a diagram showing another embodiment of the present invention in which a ground fault detection function is added. 2 ₁ ~ 2 _o+1 ...Shin breaker, 3...Bus bar, 4 ₁ ~
4 _o ... Distribution line, 5 ₁ ~ 5 _o ... Zero phase current transformer, 6 ...
…Zero-phase transformer, 7…Induced lightning surge detection device, 8
₀ to 8 _o ... Sample hold, 9... Multiplexer, 10... A/D converter, 11... Memory,
12... CPU, 13... I/O, 14... Setting I/F, 7 ₁ ... Directional ground fault detection device, 7 ₂ ... Induced lightning surge detection device.

Claims (1)

[Scope of Claims] 1. In a distribution substation in an electric power system, a zero-phase transformer connected to a bus bar from which a plurality of distribution lines branch and detects the zero-sequence voltage of the bus, and a zero-phase transformer for detecting the zero-phase voltage of each distribution line. a plurality of zero-phase current transformers each detecting current;
A memory that stores sampling data of the zero-sequence voltage waveform and sampling data of each zero-sequence current waveform, and a level change of the sampling data of the zero-sequence voltage waveform read from this memory is caused by a lightning strike to cause an imaginary linear conductor. Detecting a lightning strike near each distribution line when the waveform is similar to a bipolar surge waveform or a flashing waveform of a bipolar surge occurring in When the polarity of the waveform sampling data matches a bipolar surge and exceeds a predetermined level, or when the insulation value addition exceeds a predetermined value, it is detected for each distribution line that a lightning strike has occurred in the vicinity of the distribution line. An induced lightning surge detection device comprising: a data processing device that causes an emergency power outage of the distribution line when it is estimated that the distribution line will fail. 2. The induced lightning surge according to claim 1, wherein the data processing device includes processing means for detecting a directional ground fault from sampling data of the zero-sequence voltage waveform and each zero-sequence current waveform read from the memory. Detection device.