JP2012095464A - Transmission voltage selection method of electric power substation for power distribution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an influence caused by switching of a tap of a pole transformer.SOLUTION: A transmission voltage selection method comprises the steps of: generating first and second graphs indicating a maximum value and a minimum value of a voltage of a feeder at a point spaced away from an electric power substation for power distribution by a line length for each transmission voltage of the electric power substation for power distribution to an orthogonal coordinate system where a line length from the electric power substation for power distribution of the feeder in a power distribution system in which an electric power is supplied from a secondary side of a transformer for power distribution of the electric power substation for power distribution is defined as a first axis and the voltage of the feeder is defined as a second axis; generating a third graph indicating a range of the voltage of the feeder where a secondary side voltage of the pole transformer having a primary side connected to the feeder is in a range of a predetermined reference voltage at a point spaced away from the electric power substation for power distribution by a line length; superposing the first to third graphs on each transmission voltage; finding a deviation part where the first or second graph is deviated from the third graph; and selecting the transmission voltage based on the deviation part.

Description

  The present invention relates to a transmission voltage selection method for a distribution substation.

The voltage quality of the power supplied from the distribution system to consumers such as homes and offices needs to be maintained and ensured so that the electrical products (electrical products) used in the power system can operate stably. .
For this reason, in distribution substations, on-load tap switching transformers are generally used as distribution transformers, which are equipped with tap changers that can switch taps while a load is applied. The tap change transformer at the time of load can adjust the secondary side voltage (the transmission voltage of the distribution substation) without causing a power failure by the tap changer switching the tap according to the tap change command. For example, during the day when the power demand is large and the distribution system load is maximum, such as during the day, the transmission voltage is adjusted to be high, and at night the power demand is small and the distribution system load is minimum Is adjusted so as to lower the delivery voltage.

In addition, high voltage (for example, around 6.6 kV) power sent from the distribution substation is converted into low voltage (for example, around 100 V to 200 V) power supplied to consumers by a pole transformer. Here, the feeder voltage of the distribution system drops from the transmission voltage as the line length from the distribution substation increases, so the tap on the pole transformer has the secondary voltage (supply voltage to the customer) It is selected according to the voltage drop so as to be within a predetermined reference voltage range. For example, when the standard voltage is 100V, the pole transformer tap is selected so that the supply voltage is 101V ± 6V (95V to 107V).
Furthermore, for voltage drops that cannot be dealt with by adjusting the output voltage or selecting taps on pole transformers, a voltage regulator such as SVR (Step Voltage Regulator) is installed in the middle of the high-voltage distribution line. Installed to correct the dropped feeder voltage.
In this way, the supply voltage can be maintained within the reference voltage range by adjusting the transmission voltage, selecting the tap of the pole transformer, installing the voltage regulator, and the like.

By the way, in recent years, distributed (type) power sources such as small-scale power generation facilities using natural energy and cogeneration facilities are connected to the distribution system. Then, as the distributed power supply becomes widespread and the distributed power supply connected to the distribution system increases, the feeder voltage increases due to the reverse power flow, and thus the supply voltage may deviate from the reference voltage range. In this case, the supply voltage is maintained within the reference voltage range mainly by reviewing the installation and settling of the voltage regulator and reviewing the delivery voltage.
However, when more distributed power sources are connected to the power distribution system, tap selection for pole transformers may be reviewed and tap switching may be required. Therefore, for example, in Patent Document 1 and Patent Document 2, a tap changer on load that can be accommodated in a container of a pole transformer, or a pole that can switch taps of the pole transformer while a load is applied, An uninterruptible tap switching device that can be attached to an upper transformer is disclosed. By using these tap changers (devices), even if it is necessary to change the taps of the pole transformer, the taps can be changed without causing a power failure.

JP-A-10-275730 JP 2004-221394 A

However, it is necessary to replace the pole transformer provided with the tap changer (device) of Patent Document 1 or Patent Document 2 from the existing pole transformer provided with the no-voltage tap switch. Compared to the case where only the operation is performed, the cost is increased. In addition, although the tap can be switched without causing a power failure after the replacement, a power failure is accompanied at least during the replacement work. On the other hand, in the existing pole transformer, a power failure occurs at every tap switching work, which affects customers who are supplied with power from the pole transformer to be constructed.
Therefore, in any case, the greater the number of pole transformers that require tap switching, the greater the impact on construction costs and consumers.

  The main present invention for solving the above-mentioned problems is that the first axis is the line length from the distribution substation of the feeder of the distribution system to which power is supplied from the secondary side of the distribution transformer of the distribution substation. The first and second values indicating the maximum value and the minimum value of the feeder voltage at a point separated from the distribution substation by the line length in an orthogonal coordinate system having the feeder voltage as a second axis, respectively. A graph is created for each transmission voltage of the distribution substation, and the primary side is connected to the feeder at a point separated from the distribution substation by the line length in the same orthogonal coordinate system as the first and second graphs. A third graph indicating a voltage range of the feeder in which a secondary voltage of the connected pole transformer is within a predetermined reference voltage range is generated, and the first to third voltages are set for each of the transmission voltages. Overlay graphs A method for selecting a transmission voltage for a distribution substation, wherein the first or second graph finds a deviation portion outside the range of the third graph and selects the transmission voltage based on the deviation portion. It is.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  ADVANTAGE OF THE INVENTION According to this invention, the influence by switching of the tap of a pole transformer can be suppressed.

It is a figure explaining an example of the selection process of a transmission voltage among the transmission voltage selection methods of the distribution substation in one Embodiment of this invention. It is a block diagram which shows an example of a structure of the power distribution system with which the transmission voltage selection method of the distribution substation in one Embodiment of this invention is applied. It is a figure explaining an example of the creation process of a voltage drop curve among the transmission voltage selection methods of the distribution substation in one Embodiment of this invention. It is a figure explaining an example of the creation process of a tap selection figure among the sending voltage selection methods of the distribution substation in one Embodiment of this invention.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

=== Example of the configuration of the power distribution system ===
Hereinafter, with reference to FIG. 2, a configuration of a distribution system to which the transmission voltage selection method of the distribution substation in one embodiment of the present invention is applied will be described.
In the distribution system shown in FIG. 2, the distribution transformer 9 installed in the distribution substation has a high voltage (for example, several tens to hundreds of kV) receiving (primary side) voltage V1 ( For example, it is converted to a transmission (secondary side) voltage V2 of around 6.6 kV. Further, the distribution transformer 9 is, for example, a load tap change transformer, and controls the tap changer according to the tap change command to switch the tap of the primary winding so that the transmission voltage is not caused by power failure. V2 can be adjusted.

  A feeder (distribution line) to which electric power is supplied from the secondary side of the distribution transformer 9 is often branched into a plurality of parts, and FIG. 2 shows feeders 1 to 3 as a part thereof. Yes. As an example, the primary side of pole transformers 101 to 128 is connected to feeder 1, the primary side of pole transformers 201 to 224 is connected to feeder 2, and pole transformers 301 to 322 are connected to feeder 3. Are connected to the primary side. Each pole transformer converts the feeder (primary side) voltage at the connection point into a supply (secondary side) voltage of a low voltage (for example, around 100 V to 200 V).

  As described above, the feeder voltage drops from the sending voltage V2 as the line length from the distribution substation increases. Therefore, each pole transformer has a tap selected in advance so that the supply voltage is within a reference voltage range (for example, 95 V to 107 V) according to the voltage drop. In FIG. The status is shown. For example, each pole transformer includes taps 1 to 3, tap 1 is selected for pole transformers 101 to 104, tap 2 is selected for pole transformers 105 to 122, and pole transformer 123 is selected. In the case of 128, tap 3 is selected.

=== Step of Creating Voltage Drop Curve ===
The transmission voltage selection method for the distribution substation in this embodiment is roughly divided into a step of creating a voltage drop curve for each feeder, a step of creating a tap selection diagram for each feeder, and a step of selecting the transmission voltage V2. .
Hereinafter, with reference to FIG. 3, the process of creating a voltage drop curve (first and second graphs) for each feeder will be described. In addition, FIG. 3 has shown the preparation process of the voltage drop curve of the feeder 1 as an example.

First, at the time of light load, heavy load, and distributed voltage power generation, the feeder voltage at a point separated from the distribution substation by the line length x is measured. Here, the light load is a time zone (first time zone) set in advance as a time zone in which the load on the power distribution system is minimized, and is a time zone in which power demand is small such as at night. The heavy load time is a time zone (second time zone) set in advance as a time zone in which the load on the power distribution system is maximum, and is a time zone in which the power demand is large such as during the daytime. Furthermore, the time of distributed voltage generation is a time zone in which a reverse power flow from the distributed power source connected to the distribution system occurs.
It is desirable that the feeder voltage measurement points include the connection points of the pole transformers, and as the number of measurement points increases, the accuracy of the created voltage drop curve improves. In addition, it is desirable that the measurement points be the same during light load, heavy load, and distributed voltage power generation.

Next, the feeder voltage Vm [x] (solid line in the middle of FIG. 3) or dispersion is measured in a rectangular coordinate system with the line length x from the distribution substation as the horizontal axis and the feeder voltage as the vertical axis. The larger voltage is plotted among the feeder voltages Vm [x] (short broken line in the middle of FIG. 3) measured at the time of voltage power generation. The plotted graph becomes a voltage drop curve (first graph) indicating the maximum value of the feeder voltage.
Also, the feeder voltage Vm [x] (long broken line in the middle of FIG. 3) measured at the time of heavy load is plotted on the same orthogonal coordinate system. The plotted graph becomes a voltage drop curve (second graph) indicating the minimum value of the feeder voltage.

  In this way, two voltage drop curves (lower stage in FIG. 3) each showing the maximum value and the minimum value of the feeder voltage can be created. In the present embodiment, a voltage drop curve that approximately indicates the maximum value and the minimum value of the feeder voltage using the feeder voltage Vm [x] measured at the time of light load, heavy load, and distributed voltage generation. Have created. However, the feeder voltage may be constantly measured to obtain more accurate maximum and minimum values, and a voltage drop curve may be created.

  Further, the two voltage drop curves are created for each transmission voltage V2 corresponding to the tap of the distribution transformer 9. In the voltage drop curve, the sending voltage V2 is equal to the feeder voltage Vm [0] at the point where x = 0. Alternatively, an approximate voltage drop curve for each send voltage V2 may be created by translating a voltage drop curve from one send voltage V2 in the vertical axis direction.

=== Tap selection drawing creation process ===
Hereinafter, with reference to FIG. 4, the process of creating a tap selection diagram (third graph) for each feeder will be described. In addition, FIG. 4 has shown the preparation process of the tap selection figure of the feeder 1 as an example.
The tap selection diagram shows the range of the feeder voltage Vt [x] in which the supply voltage V3 of the pole transformer connected to the feeder is within the reference voltage range at a point away from the distribution substation by the line length x. It is a graph shown in the same orthogonal coordinate system as a curve.
Here, if the upper limit value and the lower limit value of the reference voltage range are VLmax and VLmin, respectively, the tap selection diagram indicates the range of the feeder voltage Vt [x] where VLmin ≦ V3 ≦ VLmax. Further, when the transformation ratio of the pole transformer at a point away from the distribution substation by the line length x is n [x], the range of the feeder voltage Vt [x] indicated by the tap selection diagram is VLmin × n [x ] ≦ Vt [x] ≦ VLmax × n [x]. Furthermore, since the transformation ratio n [x] of the pole transformer can be obtained based on the selection status of the tap of the pole transformer shown in FIG. 2, as shown in FIG. 4, the feeder voltage Vt [x] ] Can be created.
In this way, it is possible to create a tap selection diagram showing the feeder voltage range in which the supply voltage V3 falls within the reference voltage range.

=== Sending voltage selection process ===
Hereinafter, the process of selecting the delivery voltage V2 will be described with reference to FIG.
First, for each feeder, the voltage drop curve from one delivery voltage V2 and the tap selection chart are superimposed, and in the overlay chart, one of the two voltage drop curves is out of the range of the tap selection chart. Find the length of the horizontal axis of the part. For example, the middle part of FIG. 1 shows a superimposed diagram of the voltage drop curve from the transmission voltage V2 corresponding to the tap n of the distribution transformer 9 and the tap selection diagram in the feeder 1, and in the superimposed diagram, The length A1 of the deviation portion in the horizontal axis direction is obtained.
Next, the lengths in the horizontal axis direction of the deviation portions obtained for each feeder are summed, and the total value is obtained as an evaluation value for selecting the delivery voltage V2. For example, when power is supplied only to the feeders 1 to 3 from the secondary side of the distribution transformer 9, if the lengths in the horizontal direction of the deviation portions of the feeders 1 to 3 are A1 to A3, respectively, The value A is A = A1 + A2 + A3.

In this manner, the evaluation value for selecting the sending voltage V2 can be obtained by adding up the lengths of the deviation portions in the horizontal axis direction for each feeder.
Furthermore, the said evaluation value is calculated | required for every sending voltage V2 according to the tap of the distribution transformer 9. FIG. For example, the lower part of FIG. 1 shows a superimposed diagram of the voltage drop curve from the transmission voltage V2 corresponding to the tap n + 1 of the distribution transformer 9 and the tap selection diagram in the feeder 1, and the deviation in the feeders 1 to 3 If the lengths of the portions in the horizontal axis direction are B1 to B3, the evaluation value B is B = B1 + B2 + B3.
Finally, the sending voltage V2 is selected so that the evaluation value is minimized, and the tap changer is controlled according to the selected sending voltage V2.

  As described above, by performing the voltage drop curve creation step, the tap selection diagram creation step, and the transmission voltage selection step, the transmission voltage V2 based on the deviation portion where the voltage drop curve deviates from the range of the tap selection diagram. Can be selected. Moreover, the said deviation part has shown the range which needs switching of the tap of a pole transformer, and the influence by switching of the tap of a pole transformer is selected by selecting the sending voltage V2 based on a deviation part. Suppression can be achieved.

In this embodiment, the evaluation value obtained by totaling the lengths in the horizontal axis direction of the deviation portions determined for each feeder is minimized, but for each region including a point separated from the distribution substation by the line length x. The evaluation value may be obtained after weighting.
For example, as shown in FIG. 2, the intervals between the pole transformers connected to the feeder are usually not equal intervals. Therefore, the evaluation value is weighted according to the number of pole transformers per unit area connected to the feeder (density of pole transformers) with respect to the length of the deviation part in the horizontal axis direction. By doing so, the number of pole transformers that require tap switching can be minimized.

  In addition, for example, the number of consumers supplied with power from each pole transformer is usually not uniform. For this reason, the horizontal length of the deviating part was weighted according to the number of consumers (density of consumers) per unit area supplied with power from the pole transformer connected to the feeder. By minimizing the evaluation value, the number of consumers affected by the power outage can be minimized.

  In addition, for example, the cost required to switch taps varies depending on the model of the pole transformer and the installation location. Therefore, taps are minimized by minimizing the evaluation value weighted according to the switching cost of taps per unit area of the pole transformer connected to the feeder with respect to the length of the deviation portion in the horizontal axis direction. The cost of switching work can be minimized.

  As described above, for each transmission voltage V2, the voltage drop curve and the tap selection diagram are overlapped, and in the overlap diagram, one of the two voltage drop curves is in a deviated portion outside the range of the tap selection diagram. By selecting the transmission voltage V2 based on the above, it is possible to suppress the influence due to the switching of the tap of the pole transformer.

  In addition, by selecting the transmission voltage V2 so that the length of the deviating portion in the horizontal axis direction is minimized, it is possible to minimize the range that requires the switching of the pole transformer tap.

  In addition, by minimizing the evaluation value weighted according to the density of the pole transformer connected to the feeder with respect to the length of the deviating portion in the horizontal axis direction, the column requiring tap switching is minimized. The number of upper transformers can be minimized.

  In addition, by minimizing the evaluation value that is weighted according to the density of consumers supplied with power from the pole transformer connected to the feeder, with respect to the length in the horizontal axis direction of the deviation portion, It is possible to minimize the number of consumers affected by the power outage.

  In addition, by minimizing the evaluation value weighted according to the switching cost per unit area of the pole transformer connected to the feeder with respect to the length in the horizontal axis direction of the deviation portion, The cost of switching work can be minimized.

  In addition, by creating a voltage drop curve and tap selection diagram for each feeder that branches into multiple branches and minimizing the total evaluation value for each feeder, switching taps on pole transformers in the distribution system including branches The influence by can be suppressed.

  Moreover, the distribution transformer 9 is a load tap change transformer, and by controlling the tap changer and selecting the transmission voltage V2, the range affected by the power failure is limited to the pole transformer that performs the tap change. Can be limited to.

  In addition, by measuring the feeder voltage at the time of light load, heavy load, and distributed voltage generation, the feeder voltage Vm [x] is used to measure the maximum feeder voltage without constantly measuring the feeder voltage. A voltage drop curve can be generated that approximates the value and the minimum value.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

9 Distribution transformers 101-128, 201-224, 301-322 Pillar transformer

Claims (8)

The line length from the distribution substation of the feeder of the distribution system to which power is supplied from the secondary side of the distribution transformer of the distribution substation is the first axis, and the voltage of the feeder is the second axis. The first and second graphs showing the maximum and minimum values of the feeder voltage at points separated from the distribution substation by the line length are shown for each transmission voltage of the distribution substation. To create
In the same orthogonal coordinate system as the first and second graphs, a secondary side voltage of a pole transformer whose primary side is connected to the feeder at a point away from the distribution substation by the line length is predetermined. Create a third graph showing the voltage range of the feeder within the reference voltage range,
For each of the transmission voltages, the first to third graphs are overlapped to obtain a deviation portion where the first or second graph is out of the range of the third graph,
A method for selecting a transmission voltage of a distribution substation, wherein the transmission voltage is selected based on the deviation portion. Further obtaining an evaluation value according to the length of the deviating portion in the first axial direction;
The method for selecting a transmission voltage for a distribution substation according to claim 1, wherein the transmission voltage is selected so that the evaluation value is minimized.   According to the number of the pole transformers connected to the feeder in a region including a point away from the distribution substation by the line length with respect to the length of the deviation portion in the first axial direction. The method of selecting a transmission voltage for a distribution substation according to claim 2, wherein the evaluation value is obtained by weighting.   From the secondary side of the pole transformer connected to the feeder in a region including a point separated from the distribution substation by the line length with respect to the length in the first axial direction of the deviation portion The distribution voltage selection method for a distribution substation according to claim 2, wherein the evaluation value is obtained by performing weighting according to the number of consumers to whom electric power is supplied.   For switching the tap of the pole transformer connected to the feeder in a region including a point separated from the distribution substation by the line length with respect to the length in the first axial direction of the deviation portion. 3. The distribution voltage substation transmission voltage selection method according to claim 2, wherein the evaluation value is obtained by performing weighting according to a required cost. The power distribution system includes a plurality of the feeders,
Create the first through third graphs for each feeder,
6. The distribution voltage selection method for a distribution substation according to any one of claims 2 to 5, wherein the evaluation value summed for each feeder is obtained. The distribution transformer is an on-load tap switching transformer including a tap switching device that switches a tap according to a tap switching command.
The transmission voltage selection of the distribution substation according to any one of claims 2 to 6, wherein the transmission voltage is selected by controlling the tap changer so that the evaluation value is minimized. Method. The first graph shows the voltage of the feeder measured in a first time zone set as a time zone in which the load on the power distribution system is minimized at a point away from the distribution substation by the line length. Or the larger one of the feeder voltages measured in the time zone in which reverse power flow from a distributed power source connected to the distribution system occurs,
The second graph shows the voltage of the feeder measured in a second time zone set as a time zone in which the load of the power distribution system is maximized at a point away from the distribution substation by the line length. The method for selecting a transmission voltage for a distribution substation according to any one of claims 1 to 7, wherein:

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