JP2009065794A - Apparatus for detecting isolated operation for distributed power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for detecting an isolated operation of a distributed power supply capable of surely detecting the isolated operation of the distributed power supply at high speed. <P>SOLUTION: This apparatus for detecting the isolated operation 30 comprises: a current injector 32; and an isolated operation monitor 34. The current injector 32 injects an injection current J<SB>m1</SB>which has a low-order injection degree less than four degrees and an injection current J<SB>m2</SB>which has a high-order injection degree of four or more degrees. Based on an AND condition between determination by admittance or susceptance of the low-order injection degree and determination by admittance or susceptance of the high-order injection degree by using the change amount prior to a predetermined time, the isolated operation monitor 34 detects the isolated operation of the distributed power supply 28. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is applied to a distribution system having a configuration in which a distribution line is connected to a host system via a substation, and a distributed power source holding facility having a distributed power source is connected to the distribution line. The present invention relates to an isolated operation detection device that detects an isolated operation.

  As an example of a device that detects the independent operation of a distributed power supply, it is applied to a power distribution system with a configuration in which a distribution line is connected to the upper system via a substation, and a distributed power supply facility with a distributed power supply is connected to this distribution line. A non-integer multiple injection order (for example, 2.4th order, 2nd order, 2nd order) larger than 1 time of the fundamental wave of the power distribution system. .5th order injection current injection device for injecting an injection current, and measuring the admittance or susceptance of the injection order of the distribution system as viewed from the power receiving point of the distributed power supply facility, and from the change of the admittance or susceptance An isolated operation detection device having an isolated operation monitoring device that detects that the distributed power source has been operated independently and outputs an isolated operation detection signal has already been proposed (for example, Patent reference 1).

  In addition, by increasing the detection speed of the isolated operation detection device (in other words, reducing the detection time. The same applies hereinafter), the isolated operation detection device can be used as an alternative to the ground fault overvoltage relay (OVGR) ( That is, it is described in Non-Patent Documents 1 and 2 that the ground fault overvoltage relay and the grounded instrument transformer (GPT) can be omitted. Has been.

  In particular, when the distribution system has an extra high voltage (hereinafter abbreviated as “extra high”), the grounding-type instrument transformer becomes large and expensive for electrical insulation, and thus the effect of omitting it is great. In this specification, as in the electrical equipment technical standard, a voltage exceeding 7 kV is called an extra high, and a voltage exceeding 600 V and 7 kV or less is called a high voltage.

  Further, in Non-Patent Document 2, for the purpose of shortening the detection time (for example, 50 ms or less, the reason for this will be described later), the isolated operation detection device as described in Patent Document 1 is improved, (A) Simultaneously injecting injection currents of a low-order injection order (for example, 2.25th order or 2.5th order) and a high-order injection order (for example, 15.75th order or 17.5th order) from the current injection device, (B) In the isolated operation detection device, the susceptance of the low-order injection order and the susceptance of the high-order injection order are compared with predetermined determination values, respectively, and the isolated operation is detected with the AND condition of both determination results. An islanding detection device has been proposed.

JP 2001-251767 (paragraphs 0009, 0035-0037, FIG. 1) Edited by the Grid Connection Special Committee, “Grid Connection Regulations (Electrical Technical Regulations Grid Connection Edition) JEAC 9701-2006”, 4th edition, NEC Corporation, August 30, 2006, pages 332-333 Fumio Yamamoto and four others “Verification test of high-speed detection type interharmonic injection method independent operation detection device”, Proceedings of National Conference of the Institute of Electrical Engineers of Japan, The Institute of Electrical Engineers of Japan, March 15, 2007, No. 1 6 volumes, pages 146-147

  As described above, in order to indirectly detect a ground fault by the isolated operation detection device, it is necessary to shorten the detection time of the isolated operation (for example, 50 ms or less as described above). One means for this is to shorten the measurement time in a discrete Fourier transformer that constitutes an isolated operation monitoring device and extracts the voltage and current of the injection order.

However, if the measurement time in the discrete Fourier transformer is shortened, the SN ratio of the voltage measurement of the low-order injection order is lowered, and the monitoring result of admittance and susceptance becomes unstable. In short, the injection order voltage V _m generated by the injection current J _m (the number m represents the injection order) is expressed by the following equation, and when the injection order m is small, the injection order voltage V _m. This is because the SN ratio decreases and the SN ratio decreases. ω is the angular frequency, and L is the inductance of the distribution system.

[Equation 1]
V _m = jωL · J _m ∝jmL · J _m

  As a result, admittance and susceptance fluctuations increase due to the effects of system transients (for example, instantaneous voltage drop, insertion of large capacity power factor correction capacitors, parallel / disconnection of large capacity motors, etc.) and unnecessary operation. (That is, erroneous detection even though it should not be detected originally) is likely to occur.

In contrast, as can be seen from Equation 1, the injection order voltage V _m generated by the injection current J _m of higher infusion orders, since the injection order m sentence increases greater, in the case of low-order infusion order Compared with the SN ratio. Therefore, it is effective to use a high-order injection order from the viewpoint of the S / N ratio, thereby preventing unnecessary operations during transient fluctuations.

  From such a point of view, the isolated operation detection device described in Non-Patent Document 2 has a low-order injection order determination result and a high-order injection order in order to prevent unnecessary operations that occur with a reduction in detection time. An isolated operation is detected based on an AND condition with the determination result.

  However, taking the extra high power distribution system as an example, the extra high power distribution system usually includes the transformer 44 of the substation for high voltage distribution and the high voltage consumer connected in series thereto, as in the example shown in FIG. The power factor improving capacitor (SC) 48 is provided, and both 44 and 48 may cause series resonance in the fourth or higher order (similar to this, for example, Japanese Patent No. 3367371). (It is also described in paragraphs 0022-0024 of the publication).

FIG. 1 is a circuit model showing a simplified distribution system similar to the distribution system shown in FIG. 5 (however, the isolated operation detection device 30 is specific to the embodiment of the present invention). The same or corresponding parts are denoted by the same reference numerals. An extra-high distribution line 10 is connected to the upper system 2 via a circuit breaker 8 of an extra high-voltage distribution substation, and a high-voltage consumer is connected to the distribution line 10 via a transformer 44 of the high-voltage distribution substation. A load 46 and a capacitor 48 for power factor improvement of a high voltage consumer are connected. An extra high customer load 12 is connected to the distribution line 10, and an injection current J _m is injected into the power receiving point P from the current injection device 32 a. The susceptance of the power distribution system viewed from the power receiving point P is B.

  In the circuit model of FIG. 1, the impedance of the upper system 2 (to be precise, the percentage impedance based on 10 MVA, the same applies hereinafter) is 0.1 + j2%, the impedance of the transformer 44 is 0.33 + j2.67%, and the high voltage consumer load When the impedance of 46 is 1000%, the impedance of the power factor improving capacitor 48 is -j166.7%, the impedance of the distribution line 10 is j 0.01%, and there is no power factor improving capacitor 48 (in other words, the power factor improving FIG. 2 shows the frequency characteristics of the susceptance B when there is no series resonance due to the capacitor 48 for use, and FIG. 3 shows the frequency characteristics of the susceptance B when there is the power factor improving capacitor 48 and there is series resonance.

  As can be seen from FIGS. 2 and 3, the susceptance B during single operation differs greatly between the case where there is no series resonance due to the power factor improving capacitor 48 (FIG. 2) and the case where there is (FIG. 3). Generally, the amount of the power factor improving capacitor of the high voltage consumer varies depending on the state of the high voltage consumer load 46 (for example, after the installation of the stand-alone operation detection device, the power factor improving capacitor 48 increases with the load. In many cases, the determination value for determining the isolated operation cannot be determined well.

That is, the low when the next injection orders example 2.5 order to low order infusion order determination value J _u3, with or without series resonance by the power factor improving capacitor 48, a predetermined value (e.g. -0.2S (Siemens)), and it is possible to detect the isolated operation of the distributed power source regardless of the presence or absence of series resonance by the power factor improving capacitor 48. This is because the susceptance B changes from the state indicated by the solid line to the state indicated by the alternate long and _short dash line in the capacitive direction (that is, the positive direction) exceeding the judgment value _Ju3 when the operation is switched from the interconnection operation to the single operation. This is because it can be determined by the determination value _Ju3 that the vehicle has started driving (see FIGS. 2 and 3).

However, when the high-order infusion orders example 17.5 order, higher injection order determination value J _u4 a predetermined value on the assumption that there is no series resonance by the power factor improving capacitor 48 (e.g. -0.03S (A) When there is no series resonance due to the power factor improving capacitor 48, the susceptance B exceeds the judgment value _Ju4 in the capacitive direction when shifting from the grid operation to the single operation. Therefore, it can be determined by the determination value _Ju4 (see FIG. 2) that, however, (b) when there is a series resonance by the power factor improving capacitor 48, from the interconnected operation Even after shifting to the single operation, the susceptance B changes in the capacitive direction, but does not exceed the determination value _Ju4. Therefore, it cannot be determined by the determination value _Ju4 that the single operation has been performed (see FIG. 3). .

Assuming that there is a series resonance due to the power factor improving capacitor 48, the determination value _Ju5 of the high-order injection order is set to a predetermined value (for example, about -0.1S). If there is a series resonance due to the capacitor 48 for improving the rate, the susceptance B changes in the capacitive direction beyond the judgment value _Ju5 when shifting from the interconnected operation to the isolated operation. Although it can be determined by the value J _u5 (see FIG. 3), (b) when there is no series resonance by the power factor improving capacitor 48, the susceptance B has already set the determination value J _u5 in the capacitive direction during the interconnected operation. Since it has exceeded, it is determined that the vehicle is operating alone, and since unnecessary detection has occurred from the beginning, it cannot be detected (see FIG. 2).

  Therefore, as described in Non-Patent Document 2, the susceptance of the low-order injection order and the susceptance of the high-order injection order are compared with the predetermined determination values, respectively, and the isolated operation is detected under the AND condition of both. Although isolated operation can be detected at high speed, there is still room for improvement in that it may not be detected reliably (that is, without non-detection or unnecessary detection). This is summarized in Table 1.

  In the above, the case of determining by susceptance has been described as an example. However, since most of the admittance of the power distribution system is susceptance, the same can be said for the case of determining by admittance.

  In view of this, the present invention provides an isolated operation detection device that further improves the isolated operation detection device described in Non-Patent Document 2 so that the isolated operation of a distributed power source can be detected at high speed and reliably. Is the main purpose.

  The islanding operation detection device according to the present invention injects an injection current having an injection order of a non-integer multiple larger than 1 times the fundamental wave of the distribution system into a lead-in line from the distribution line to the distributed power supply facility. Measures the admittance or susceptance of the injection order of the power distribution system as viewed from the power receiving point of the apparatus and the distributed power supply facility, and detects that the distributed power supply has become an independent operation from the change in the admittance or susceptance In the isolated operation detection device comprising the isolated operation monitoring device that outputs the isolated operation detection signal, (1) the current injection device includes an injection current of a low-order injection order less than the fourth order and a high value of the fourth order or higher. (2) The islanding operation monitoring device measures (a) the admittance or susceptance of the low-order injection order. And (b) comparing the admittance or susceptance measured by the low-order side measurement means with a predetermined low-order side determination value to detect that the distributed power supply is in an independent operation. A lower order determination means for outputting a lower order detection signal, (c) a higher order measurement means for measuring the admittance or susceptance of the higher order injection order, and (d) a measurement by the higher order measurement means. (E) a change in the admittance or susceptance detected by the change detection means is compared with a predetermined higher-order determination value. And (f) an output from the low-order side determination means and Logical product of taking the logical product of the outputs from the secondary determination means, and outputting the isolated operation detection signal when both the low-order detection signal and the high-order detection signal are output, It is characterized by that.

  When we examined the power distribution system, the amount of change in the admittance or susceptance of the power distribution system viewed from the receiving point of the facility with the distributed power supply from the predetermined time (for example, about 1 second) depends on the presence and amount of the power factor improvement capacitor. In other words, in other words, it was found that the power factor correction capacitor is stable without being affected by the series resonance.

  Therefore, as described above, the high-order injection order side can reliably detect the isolated operation of the distributed power supply without being affected by the series resonance caused by the power factor correction capacitor by measuring and judging the change in admittance or susceptance. can do.

  For transient fluctuations, as described above, the measurement result is stable by measuring and determining the change in admittance or susceptance of the higher order injection order with a high S / N ratio. Even if the detection speed is increased, unnecessary detection can be prevented.

  Furthermore, in the logical product means, the logical product (AND) of the output from the low order side determination means and the output from the high order side determination means is taken, and the isolated operation detection signal is output under the AND condition of both outputs. Therefore, it is possible to prevent unnecessary detection at the time of system switching for switching the system from one upper system to another upper system.

  As a result, it is possible to reliably detect a single operation of the distributed power supply at a high speed while preventing non-detection and unnecessary detection.

  According to the present invention, the determination based on the AND condition between the determination of the admittance or susceptance of the low-order injection order and the determination of the change in the admittance or susceptance of the high-order injection order is adopted. It can be detected at high speed and reliably.

  Therefore, for example, the isolated operation detection device according to the present invention can be used for indirect detection of a ground fault accident (in other words, replacement of the ground fault overvoltage relay by the isolated operation detection device). By using it, it is possible to prevent a decrease in the ground fault detection sensitivity of the substation. Moreover, the grounded overvoltage relay and the grounded instrument transformer for the grounded overvoltage relay can be omitted on the side of the distributed power supply facility, and the facility cost can be reduced.

  FIG. 5 is a single-line connection diagram showing an example of a distribution system including the distributed power supply isolated operation detection device according to the present invention. This distribution system is an example in the case where the distribution line 10 is an extraordinary distribution line, but is not limited thereto, and the distribution line 10 may be a high-voltage distribution line.

  This distribution system has a configuration in which an extra high distribution line 10 is connected to an upper system 2 via an extra high power distribution substation 4. The substation 4 includes a transformer 6 and a circuit breaker 8 that connects the secondary side of the transformer 6 and the distribution line 10. In addition, although the distribution line in the case of a special height whose voltage exceeds 7 kV is referred to as a special distribution line, in this specification, this case is also referred to as a distribution line.

  As described above, the distribution line 10 is a distribution line having a special height (that is, the voltage exceeds 7 kV), and the voltage is, for example, 11 kV, 22 kV, 33 kV, 66 kV, and 77 kV. However, the distribution line 10 may be a high-voltage distribution line (that is, a voltage of 7 kV or less), and the voltages in this case are, for example, 3.3 kV and 6.6 kV.

  In this example, the distribution line 10 is connected to an extra-high customer load 12, a distributed power supply facility 14 having a distributed power supply 28, and a high-voltage distribution substation 42.

  As described above, the high voltage distribution substation 42 includes the transformer 44 and the circuit breaker 45. As described above, the high voltage distribution substation 42 is connected to the high voltage consumer load 46 and the power factor improving capacitor 48.

  In this example, an isolated operation detection device 30 as described below is provided in the distributed power supply facility 14 connected to the distribution line 10 at the power receiving point P.

  In the distributed power supply facility 14, a local bus 22 is connected to the power receiving point P via a lead-in line 18 and a transformer 19. A distributed power source 28 is connected to the local bus 22 via a circuit breaker 20 and a transformer 26, and power synchronized with the fundamental wave of the distribution system is supplied from the distributed power source 28 to the local bus 22. . This is called “interconnection operation”.

  In the event of a grid fault or the like, the circuit breaker 8 of the extra high-voltage distribution substation 4 is opened. At that time, as described above, when the distributed power source 28 is operating (ie, isolated operation), an electric shock accident or the like may occur. It is necessary to disconnect (disconnect) the distributed power source 28 from the distribution system by opening 20.

  Therefore, in this embodiment, an isolated operation detection device 30 for detecting the isolated operation of the distributed power supply 28 is provided in the distributed power supply facility 14. The isolated operation detection device 30 includes a current injection device 32 and an isolated operation monitoring device 34.

A current transformer 40 for measuring the current flowing through the lead-in line 18 is connected to the lead-in line 18, and an instrument transformer 38 for measuring the voltage is connected to the local bus 22. measurement voltage V _t and obtained by measuring at 40 measuring current I _t is supplied to the independent operation monitoring device 34. The instrument current transformer 40 may be provided on the secondary side (low voltage side) of the transformer 19. The instrument transformer 38 is preferably provided on the secondary side of the transformer 19 as in this example because insulation is simplified.

In this example, the current injection device 32 is supplied to the lead-in wire 18 and the power receiving point P and the distribution line 10 via a voltage matching transformer 36 and the like, which is a non-integer multiple (that is, greater than 1 times the fundamental wave of the distribution system). An injection current having an injection order of a fractional number is injected. More specifically, the current injection device 32 simultaneously injects both an injection current J _{m1 having} an injection order m1 of less than the fourth order and an injection current J _{m2 having} an injection order m2 of the fourth order or more. The subscripts m1 and m2 attached to the injection currents J _m1 and J _m2 , voltage V and current I, which will be described later, represent the above injection orders.

A more specific example of the current injection device 32 is shown in FIG. The current injection device 32 includes a square wave power supply 50 for generating a square wave voltage RV _m1 of the injection order m1 (for example, 2.3 order, 2.5 order, etc.), and two in series inserted in its output line. Series resonance circuits (series LC resonance circuits) 52 and 54 are provided. The square wave power supply 50 is an inverter, for example. The series resonance circuit 52 has a resonance frequency of the low-order injection order m1, and the series resonance circuit 54 has a resonance frequency of the high-order injection order m2. The high-order injection order m2 is, for example, an order that is an odd number (ie, 3, 5, 7,...) Times 3 or more times the low-order injection order m1. More specifically, the low-order injection order m1 is 2.5th, and the high-order injection order m2 is 17.5th. However, it is not limited to these.

With such a single current injection device 32, the two injection orders m1 and m2 of sinusoidal injection currents J _m1 and J _m2 can be injected simultaneously. In other words, an injection current including these two injection currents J _m1 and J _m2 can be injected. Accordingly, the configuration of the current injection device 32 can be simplified and downsized.

A more specific example of the isolated operation monitoring device 34 is shown in FIG. The upper side from the one-dot chain line 110 is a circuit for the lower order injection order m1, and the lower side is a circuit for the higher order injection order m2. The isolated operation monitoring device 34, analog the measurement voltage V _t, it receives a measured current I _t, the filter 60 to 63 to remove the fundamental and harmonics of an integral multiple orders of the distribution system, which is output therefrom AD converters 66 to 69 for converting the voltages and currents into digital signals and outputting voltages V _d1 and V _d2 and currents I _d1 and I _d2 , respectively. When a digital filter is used, an AD converter may be provided in the preceding stage. The voltage V _d1 , current I _d1 , voltage V _d2 , and current I _d2 are supplied to discrete Fourier transformers 70 to 73, respectively.

The discrete Fourier transformer 70 performs a discrete Fourier transform on the voltage V _d1 to extract and output the voltage V _m1 of the low-order injection order m1.

The discrete Fourier transformer 71 performs a discrete Fourier transform on the current I _d1 to extract and output the current I _m1 of the low-order injection order m1.

The discrete Fourier transformer 72 performs discrete Fourier transform on the voltage V _d2 to extract and output the voltage V _m2 of the higher order injection order m2.

The discrete Fourier transformer 73 performs a discrete Fourier transform on the current I _d2 to extract and output the current I _m2 of the higher-order injection order m2.

The voltage V _m1 and the current I _m1 are supplied to the calculator 76. The calculator 76 uses the supplied voltage V _m1 and current I _m1 to calculate the admittance Y _m1 of the low-order injection order m1 according to the following equation, and further extracts the susceptance B _m1 that is the imaginary part of the admittance Y _m1. Output.

[Equation 2]
Y _m1 = I _m1 / V _m1

The voltages V _m1 and V _m2 , currents I _m1 and I _m2 , susceptances B _m1 and B _m2 , which will be described later, and admittances Y _m1 and Y _m2 are all expressed in complex numbers.

The voltage V _m2 and the current I _m2 are supplied to the calculator 78. The calculator 78 uses the supplied voltage V _m2 and current I _m2 to calculate the admittance Y _m2 of the higher-order injection order m2 according to the following equation, and further extracts the susceptance B _m2 that is the imaginary part of the admittance Y _m2 Output.

[Equation 3]
Y _m2 = I _m2 / V _m2

  The filters 60 and 61, the AD converters 66 and 67, the discrete Fourier transformers 70 and 71, and the arithmetic unit 76 constitute a low-order measurement unit. The filters 62 and 63, the AD converters 68 and 69, the discrete The Fourier transformers 72 and 73 and the computing unit 78 constitute a higher-order measurement unit.

The susceptance B _m1 is supplied to the determination device 80. The determiner 80 compares the susceptance B _m1 with a predetermined lower-order determination value _{Ju 1} to detect that the distributed power source 28 (see FIG. 5) has become an independent operation, and detects the lower-order detection signal S. ₁ is output. The determiner 80 constitutes a low-order determination unit.

Determiner 80, and more specifically in this example, as in the example shown in FIG. 9A, when the susceptance B _m1 is changed beyond the low-order side determination value J _u1 capacitive direction (or positive direction) , and outputs the low-order side detection signal S _1. FIG. 9 shows an example when an isolated operation occurs at time t ₁ . Low-order side decision value J _u1, for example, it is sufficient to set to about 50% of the susceptance B _m1 during interconnected operation, in the example of FIG. 9A is so.

Referring to FIG. 7 again, the susceptance B _m2 is supplied to the change detection circuit 90. The change detection circuit 90 detects a change ΔB _m2 of the susceptance B _m2 from a predetermined time before. This change detection circuit 90 constitutes a change detection means.

Variation detecting circuit 90, in this example, a delay circuit 92 to a susceptance B _{m @ 2} for a predetermined time T delay outputs from the arithmetic unit 78, the susceptance B _{m @ 2} from the delay circuit 92 from the susceptance B _{m @ 2} from the calculator 78 and a subtracter 94 for outputting a variation .DELTA.B _{m @ 2} susceptance B _{m @ 2} by subtracting. The predetermined time T is, for example, 1 second or 2 seconds, but is not limited thereto.

  As described above, when the distribution system is examined, the change in the admittance or susceptance of the distribution system viewed from the power receiving point P of the distributed power holding facility 14 from the predetermined time T (for example, about 1 second) is the power factor. It has been found that, regardless of the presence / absence and amount of the improvement capacitor 48, in other words, without being affected by the series resonance caused by the power factor improvement capacitor 48, it is stable.

  The reason for this will be described by taking susceptance as an example. Even if a factor that changes susceptance occurs, for example, even if there is a change in the presence or amount of power factor improving capacitor 48, the amount of change in susceptance ΔB changes. Since the susceptance change factor is already settled and the susceptance is stable after the predetermined time T has elapsed, the susceptance change ΔB returns to a substantially zero state. It is.

  Even when the single operation occurs, the susceptance change ΔB is not zero for the predetermined time T. FIG. 4 illustrates the change ΔB during the predetermined time T. Although the change ΔB returns to 0 after the lapse of the predetermined time T, there is no problem if the isolated operation is detected during the predetermined time T. For example, even if the predetermined time T is set to 1 second, the isolated operation can be detected within 50 milliseconds as described later, so that there is no problem. Of course, the predetermined time T may be longer than 1 second.

FIG. 4 shows the frequency characteristics of the change ΔB of the susceptance B shown in FIGS. The susceptance change ΔB is the same regardless of the presence or absence of the power factor improving capacitor 48 in any order, not only during the continuous operation indicated by the solid line but also when the single operation indicated by the alternate long and short dash line occurs. It turns out that it is stable without being influenced by the series resonance by the capacitor 48 for improving the rate. Therefore, for example, focusing on the high-order injection order m2, a high-order side determination value _Ju2 to be described later for the high-order injection order m2 is set to a constant value regardless of the presence / absence or amount of the power factor improving capacitor 48. be able to.

The change detection circuit 90 is not limited to the example shown in FIG. 7, and may include a moving average calculation circuit 96 instead of the delay circuit 92, as in the example shown in FIG. 8, for example. The moving average calculation circuit 96 delays and outputs the susceptance B _m2 for a first predetermined time T ₁ (for example, 1 second), and outputs the susceptance B _m2 for a second predetermined time T ₂ (for example, 2 seconds). ) A delay circuit 100 that outputs after delay, an adder 102 that adds outputs from both delay circuits 98 and 100, and an amplifier 104 that halves the output from the adder 102. Further, instead of the delay circuit 92 and the moving average calculation circuit 96, a low-pass filter having a very long time constant (for example, about 10 seconds) may be provided.

Referring to FIG. 7 again, the susceptance change ΔB _m2 output from the change detection circuit 90 is supplied to the determiner 82.

The determiner 82 detects that the distributed power source 28 (see FIG. 5) has become an independent operation by comparing the change ΔB _m2 with a predetermined higher-order determination value J _u2 and detects a higher-order detection signal. and it outputs the S _2. This determination device 82 constitutes higher-order determination means.

More specifically, in this example, the determiner 82 changes the susceptance change ΔB _m2 in the capacitive direction (that is, the positive direction) exceeding the higher-order determination value _Ju2 as in the example shown in FIG. 9B. when, and outputs the high-order side detection signal S _2. Higher side decision value J _u2, for example, it is sufficient to set to about 50% of the interconnected operation change of susceptance component when the transition to the single operation from .DELTA.B _{m @ 2,} in the example of FIG. 9B are that way .

Note that the determination values J _u1 and J _u2 can be determined relatively easily in advance by, for example, performing simulation or measurement test of the distribution system to be applied. What is necessary is just to set to the container 80,82.

The low order detection signal S ₁ and the high order detection signal S ₂ are supplied to the AND circuit 84. AND circuit 84 calculates the logical product of the two detection signals _{S 1, S 2 (AND)} , and outputs a detection signal S ₃ when both detection signals S _1, S ₂ are output together. The AND circuit 84 constitutes a logical product means.

Rather than outputting the detection signal S ₃ as an isolated operation detection signal from the isolated operation monitoring device 34 as it is, the detection signal S ₃ is continued for a predetermined continuation confirmation time T ₃ by the duration determination unit 86 as in this example. and it is preferable to outputs a islanding detection signal S ₄ when continuing to determine the are. In so doing, it is possible to prevent erroneous detection due to instantaneous variation such as voltage V _t from any cause other than the isolated operation. The continuation confirmation time T ₃ is the longer it, correspondingly, since the islanding detection becomes slow, for example may be about 30m sec. In this example, by the output of the isolated operation detection signal S ₄ , the isolated operation monitoring device 34 finally confirms that the distributed power supply 28 in the distributed power supply facility 14 in which the isolated operation monitoring device 34 is provided has been operated independently. It will be detected.

Islanding To do disconnecting the islanding detection after dispersing power source 28 by the monitoring device 34, for example, as in the example shown in FIG. 5 may be opened breaker 20 by the independent operation detecting signal S _4.

According to this isolated operation detection device 30, the high-order injection order m2 side measures and determines the susceptance change ΔB _m2 , so that it is not affected by the series resonance by the power factor correction capacitor 48 and is distributed. Can be reliably detected.

For transient fluctuations, as described above, the measurement result is stable by measuring and determining the susceptance change ΔB _m2 of the high-order injection order m2 having a high S / N ratio. Even if the measurement time in 70 to 73 is shortened to increase the detection speed, unnecessary detection can be prevented.

Further, the AND circuit 84 takes the low-order side of the output S ₁ and the higher side of the output S ₂ of the logical product from the decision unit 82 from the judging unit 80 (AND), AND between the output S _1, S ₂ by which is adapted to output a detection signal S ₃ thus islanding detection signal S ₄ under the condition, it is possible to prevent an unnecessary detection of the time of system switching to switch the system from one of the top line to the other higher strains.

  This system switching will be described. As shown in FIG. 10, there are two higher systems, 2a and 2b, to which the distribution line 10 is connected via the circuit breakers 8a and 8b of the extra high-voltage distribution substation, respectively. Further, consider a case where a distributed power supply facility 14 having an isolated operation detection device 30 is connected.

  When the system is switched from the upper system 2a to the upper system 2b, the circuit breakers 8a and 8b are opened and closed according to the procedure shown in Table 2. When switching in the reverse direction, the reverse procedure is used. The reason for creating a loop state is to prevent a power outage.

FIG. 11 shows a simplified state of changes in the change ΔB _m2 of the susceptance B _m1 of the low-order injection order m1 and the susceptance of the high-order injection order m2 at the time of system switching shown in Table 2.

As shown in FIG. 11A, the susceptance B _m1 of the low-order injection order m1 increases in the negative direction (that is, in the inductive direction) in the loop state. This is because the impedances of the two higher systems 2a and 2b are in parallel. However, since the lower order determination value _Ju1 is not exceeded, unnecessary detection does not occur.

On the other hand, as shown in FIG. 11B, the susceptance change ΔB _m2 of the higher-order injection order m2 increases in the negative direction for a predetermined time (the predetermined time T) immediately after the transition to the loop state (time t ₂ ). Furthermore, (b) it increases in the positive direction only for a predetermined time (the predetermined time T) immediately after the transition to the system 2b interconnection (time t ₃ ). In any case, when the predetermined time T elapses, the change ΔB _m returns to 0 as described above.

The increase in (a) is because the impedances of the two higher systems 2a and 2b are in parallel, and the increase in (b) is because the two parallel impedances become one impedance. Accordingly, the increasing directions are opposite to each other. In the increase in (a), the change ΔB _m2 does not exceed the higher-order determination value J _u2 , but in the increase in (b), the change ΔB _m2 exceeds the higher-order determination value J _u2 . Therefore, unnecessary detection occurs. However, as described above (see FIG. 11A), unnecessary detection does not occur on the low-order injection order m1 side. Therefore, by employing the determination based on the AND condition, unnecessary detection at the time of system switching can be prevented. .

  Table 3 summarizes the phenomena in the power distribution system and the determination results in the isolated operation detection device 30.

As is apparent from comparison between Table 3 and Table 1 above, according to the single operation detection device 30, the determination of the susceptance B _m1 of the low-order injection order and the change ΔB of the susceptance of the high-order injection order. _Since the determination based on the AND condition with the determination of _m2 is adopted, the isolated operation of the distributed power source 28 can be detected reliably at high speed while preventing non-detection and unnecessary detection.

  Therefore, for example, this isolated operation detection device 30 can be used for indirect detection of a ground fault accident (in other words, replacement of the ground fault overvoltage relay by the isolated operation detection device 30). By using it, the fall of the ground fault detection sensitivity of the substation 4 can be prevented. In addition, the ground fault overvoltage relay (OVGR) and the grounded instrument transformer (GPT) for the ground fault overvoltage relay (OVGR) can be omitted on the distributed power supply facility 14 side, and the equipment cost can be reduced. In particular, when the distribution line 10 is an extra high distribution line, as described above, the extra high-voltage grounding type instrument transformer is large and expensive, so that it is possible to omit this and the economic effect is great. .

  Next, the example of the result of having performed the simulation of isolated operation detection using the model of the extra high distribution system will be described.

FIG. 12 shows an example in which an isolated operation is generated at time t ₄ . As shown in FIG. 12A, the susceptance B _m1 lower order infusion order m1 is greater than a low-order side determination value J _u1 at time t ₅ after about 5m seconds from time t _4. As shown in FIG. 12B, variation .DELTA.B _m2 of susceptance of higher infusion order m2 is exceeded higher side determination value J _u2 at time t ₆ of about 20m seconds after the time t _4. Since independent operation detecting apparatus 30 is determined by both the AND condition, the detection signal S ₃ is output at time t ₆ after approximately 20m seconds isolated operation occurrence time t _4. The final isolated operation detection, that is, the output of the isolated operation detection signal S ₄ was performed after the lapse of the duration T ₃ set to 30 milliseconds.

Since the time T ₄ from the occurrence of the isolated operation until the final detected independent operation is expressed by the following equation, high-speed detection of about 50 milliseconds or less could be performed.

[Equation 4]
T ₄ = (t ₆ −t ₄ ) + T ₃
≒ 20 + 30
≒ 50 [msec]

  The reason for setting the isolated operation detection time target within 50 milliseconds is as follows. As described in Non-Patent Document 1 above, in an extra high or high voltage distribution system, within one second from the occurrence of a ground fault, a distributed power source is disconnected by a ground fault overvoltage relay or by an independent operation detection device. Disaggregation of distributed power sources is required. It usually takes about 0.9 seconds from the occurrence of a ground fault to the time when the circuit breaker 8 of the extra high-voltage distribution substation 4 is opened and the single operation occurs. Normally, it takes about 50 milliseconds to open the circuit breaker 20 in the distributed power supply facility 14 and disconnect the distributed power supply 28 after detecting the isolated operation. Accordingly, since the time remaining for the isolated operation detection is about 50 milliseconds, the time less than that is the detection time target.

FIG. 13 shows an example in which the power factor improving capacitor 48 is turned on at time t ₇ to generate a transient fluctuation. As shown in FIG. 13A, the susceptance B _m1 lower order infusion order m1 is about 20m seconds between time t ₈ ~t ₉ exceeds the low-order side decision value J _u1, during which occurs unnecessary detection . However, as shown in FIG. 13B, the susceptance change ΔB _m2 of the higher-order injection order m2 does not exceed the higher-order determination value _Ju2, and therefore unnecessary detection does not occur. Since the independent operation detection device 30 makes a determination based on the AND condition of both, unnecessary detection can be prevented.

  In the above description, the case of determining by susceptance has been described as an example. However, since most of the admittances of the distribution system are susceptances and they are similar, the determination may be made by using admittance instead of susceptance.

For example, the computing unit 76 shown in FIG. 7 obtains the admittance Y _m1 of the low-order injection order m1, the computing unit 78 obtains the admittance Y _m2 of the high-order injection order m2, and the change detection circuit 90 changes the admittance Y _m2 . ΔY _m2 is obtained and compared with the lower-order determination value J _u1 for the admittance Y _m1 in the determiner 80, and compared with the higher-order determination value J _u2 for the admittance change ΔY _m2 in the determiner 82. Also good.

  Alternatively, one of the low-order injection order m1 side and the high-order injection order m2 side may be determined by susceptance, and the other may be determined by admittance.

It is a figure which shows an example of the circuit model which simplified the extra high power distribution system. FIG. 2 is a diagram illustrating an example of frequency characteristics of susceptance viewed from a power receiving point when there is no series resonance due to a power factor correction capacitor in the circuit of FIG. 1. It is a figure which shows an example of the frequency characteristic of a susceptance seen from the receiving point in the case of the series resonance by the capacitor for power factor improvement in the circuit of FIG. It is a figure which shows an example of the frequency characteristic for the change of a susceptance. It is a single line connection figure which shows an example of a power distribution system provided with the isolated operation detection apparatus of the distributed power source which concerns on this invention. It is a circuit diagram which shows an example of the current injection apparatus in FIG. It is a block diagram which shows an example of the independent operation monitoring apparatus in FIG. It is a block diagram which shows the other example of the variation detection circuit of a susceptance. It is a figure which simplifies and shows the mode of the change of the susceptance of the low order injection order and the susceptance of the high order injection order at the time of single operation generation | occurrence | production. It is a figure which shows an example of the circuit model for demonstrating system | strain switching. It is a figure which simplifies and shows the mode of the change of the susceptance of the low order injection order at the time of system | strain change, and the susceptance of a high order injection order. It is a figure which shows an example of the result of having simulated the change of the susceptance of the low order injection order and the susceptance of the high order injection order at the time of single operation generation | occurrence | production. It is a figure which shows an example of the result of having simulated the change of the susceptance of the low order injection order and the susceptance of the high order injection order at the time of transient fluctuation generation | occurrence | production.

Explanation of symbols

2 Upper system 4 Substation for extra high distribution 10 Distribution line 14 Distributed power supply equipment 18 Service line 28 Distributed power supply 30 Isolated operation detection device 32 Current injection device 34 Isolated operation monitoring device 70 to 73 Discrete Fourier Transform 76, 78 Calculator 80 , 82 determiner 84 the AND circuit 90 variation detecting circuit m1 lower order infusion orders m2 higher infusion orders J _m1, J _m2 injected current B _m1 susceptance .DELTA.B _m2 susceptance variation S ₄ islanding detection signal

Claims (1)

A distribution line is connected to a host system via a substation, and this distribution line is applied to a distribution system having a configuration in which a distributed power supply facility having a distributed power source is connected,
A current injection device for injecting an injection current of a non-integer multiple greater than 1 times the fundamental wave of the distribution system into a lead-in line from the distribution line to the distributed power supply holding facility;
Measures the admittance or susceptance of the injection order of the power distribution system as viewed from the power receiving point of the distributed power supply facility, and detects that the distributed power supply is in an independent operation from the change in the admittance or susceptance. In an isolated operation detection device comprising an isolated operation monitoring device that outputs an operation detection signal,
(1) The current injection device injects an injection current of a low-order injection order lower than the fourth order and an injection current of a higher-order injection order of the fourth order or higher,
(2) The isolated operation monitoring device
(A) low-order measurement means for measuring the admittance or susceptance of the low-order injection order;
(B) By comparing the admittance or susceptance measured by the low-order side measurement means with a predetermined low-order side determination value, it is detected that the distributed power source has become an independent operation, and a low-order detection signal is output. Lower order side determination means to
(C) high-order measuring means for measuring the admittance or susceptance of the high-order injection order;
(D) a change detection unit that detects a change in admittance or susceptance measured by the higher-order measurement unit from a predetermined time;
(E) By comparing the change in admittance or susceptance detected by the change detection means with a predetermined higher-order determination value, it is detected that the distributed power source has become an independent operation, and a higher-order detection signal Higher-order side determination means for outputting
(F) The logical product of the output from the low-order side determination means and the output from the high-order side determination means is taken, and when both the low-order detection signal and the high-order detection signal are output, the single An isolated operation detection device for a distributed power source, comprising: AND means for outputting an operation detection signal.

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