WO2009090889A1

WO2009090889A1 - Three-phase four-cable power distribution system and method for installing balancer in the system

Info

Publication number: WO2009090889A1
Application number: PCT/JP2009/000158
Authority: WO
Inventors: Sadatsugu Toribami
Original assignee: Sadatsugu Toribami
Priority date: 2008-01-17
Filing date: 2009-01-16
Publication date: 2009-07-23
Also published as: JPWO2009090889A1; CN101557109A

Abstract

Provided is a method for appropriately installing a balancer in a three-phase four-cable power distribution system, thereby effectively obtaining energy at a low cost. A balance transformer (1) for reducing an unbalanced current flowing in a neutral conductor into a three-phase power line is installed in a line of the three-phase four-cable power distribution system having a three-phase power line and a neutral conductor as follows. A neutral line current in the line connecting the balance transformer (1) is measured. A capacity of the balance transformer (1) connected to the end of the line is calculated from a maximum value of the measured neutral conductor current and a maximum use voltage of the line. A balance transformer (1) having the calculated capacity is connected to the end of the line.

Description

Three-phase four-wire power distribution system and method of arranging balancer in the system

The present invention relates to a balancer disposition method that effectively utilizes an unbalanced current flowing in a neutral wire in a three-phase four-wire distribution system.

In developing countries, a three-phase four-wire system that supplies three-phase AC power using four wires is used as a power distribution method. FIG. 13 shows a configuration example of a three-phase four-wire power distribution system. As shown in FIG. 13, the three-phase four-wire distribution system is composed of four electric wires of three-phase power lines U, V, W and a neutral line N. For example, when using a device with relatively high power, such as a motor, as a load, use three-phase power lines U, V, W (three-phase, three wire) and using a device with relatively low power, such as a light, as a load. Can be used by using the neutral line N and the power lines U, V, and W of the respective phases (single-phase two lines).

As shown in FIG. 13, the three-phase power lines U, V, W and the neutral line N are electrically connected to the U-phase, V-phase, W-phase and N-phase of the three-phase four-wire transformer, respectively. Has been. Further, the power lines U, V, W and the neutral line N are electrically connected to the distribution board 10. Symbols r _U , r _V , r _W , r _N in the figure indicate the electric resistances of the power lines U, V, W and the neutral line N, respectively. The motor M is electrically connected to the three-phase power lines R, S, and T connected to the distribution board 10. An electric lamp (not shown) is electrically connected to one of the three-phase power lines R, S, T and the neutral line N. As described above, when the motor M is in operation, electric power is supplied to the motor M through the three-phase power lines U, V, and W. When the lamp is turned on, power is supplied to the lamp through one of the three-phase power lines R, S, T and the neutral line N.

Thus, in the three-phase four-wire distribution system, two types of power can be used in the same wiring equipment, so the merit of equipment cost is great, and it is often adopted in power supply facilities in developing countries. On the other hand, in this three-phase four-wire distribution system, each customer's equipment is connected between the neutral line N and the three-phase power lines U, V, and W, so the load state of each phase Are always different and an imbalance occurs. When an unbalance occurs, surplus power in a phase with a small load flows through the neutral line N as an unbalanced current, and power is consumed wastefully.

Therefore, the present inventor has reduced the unbalanced current to the power lines U, V, and W, thereby effectively utilizing the unbalanced current that has been wasted. (See Patent Document 1). This three-phase four-wire power-saving transformer is a three-phase four-wire low-voltage distribution circuit composed of R-phase, S-phase, and T-phase power lines and neutral wires, and is composed of U-phase, V-phase, and W-phase. The first forward winding coil and the first reverse winding coil having the same number of coil windings and different electrical winding directions are provided, and the number of coil windings is equal and the electrical winding direction is the same. Different second forward winding coils and second reverse winding coils are wound around the long sides of the U phase, V phase, and W phase, and one end of the first forward winding coil of each phase is connected to the first reverse winding coil of the next phase. Connect to one end to form three first absorption coils, connect one end of the second forward winding coil of each phase to one end of the second reverse winding coil of the next phase to form three second absorption coils, Connect the other end of the first reverse winding coil of each phase and the other end of the second forward winding coil of the previous phase, and combine the first absorption coil and the second absorption coil The first absorption coil side ends are connected to the corresponding power lines, the second absorption coil side ends are connected to the neutral lines, and the unbalanced current flowing through the neutral lines is reduced to the power lines. It is.

JP 2007-48859 A

According to the three-phase four-wire power saving transformer, the first absorption coil and the second absorption coil can absorb the unbalanced current generated in the neutral line due to the unbalanced load and reduce it to the power line. Although it is possible to effectively use the unbalanced current that has been consumed in vain, a method for arranging this three-phase four-wire power-saving transformer on an actual power distribution system has not been established.

Therefore, in the present invention, a three-phase four-wire system capable of appropriately arranging a balancer as described in Patent Document 1 in a three-phase four-wire power distribution system and efficiently achieving energy efficiency at low cost. An object is to provide a power distribution system and a method of arranging a balancer in the system.

In the three-phase four-wire distribution system according to the present invention, the balancer is arranged in such a way that an unbalanced current flowing in the neutral line is applied to the three-phase four-wire distribution system consisting of a three-phase power line and a neutral line. The balancer is arranged to provide a balancer that returns to the power line of the balancer, measuring the neutral line current of the line connecting the balancer, the maximum value of the measured neutral line current and the maximum working voltage of the line Calculating the capacity of the balancer connected to the end of the line from the line, and connecting the balancer having the calculated capacity to the end of the line.

According to the balancer disposition method in the three-phase four-wire distribution system of the present invention, the capacity of the balancer connected to the end of the line from the maximum value of the neutral current of the line connecting the balancer and the maximum working voltage of the line. By connecting the balancer having the calculated capacity to the end of the line, it is possible to efficiently reduce the unbalanced current by the balancer.

The balancer arrangement method in the three-phase four-wire distribution system of the present invention further includes measuring the power at a plurality of locations including a line branched from the line, and connecting the balancer to the line where the measured power is maximum. It is desirable to include a line to be used. As a result, even when the power of the line branched from the line is large, the balancer can be connected to the end of the line where the power is the largest among the branched lines, thereby reducing the unbalanced current efficiently by the balancer. Can be done.

In addition, the method of arranging the balancer in the three-phase four-wire distribution system according to the present invention is such that the balancer is connected via a switch that opens and closes intermittently at a predetermined time interval, and the switch is opened and closed intermittently at a predetermined time interval. Thus, it is desirable to measure the power amount of the line connected to the balancer to obtain a comparative daily load curve, and to calculate the power saving amount from the comparative daily load curve.

As a result, even if there is no daily load curve, a comparison daily load curve between the switch being closed, that is, the state where the balancer is connected, and the state where the switch is open, that is, the state where the balancer is not connected, is obtained. By obtaining and calculating the power saving amount, it is possible to confirm the power saving effect by the balancer.

Here, the time interval for opening and closing the switch is preferably 5 to 30 minutes. Thereby, it becomes difficult to be influenced by the change of the power usage state according to the time zone, and it becomes possible to calculate a more accurate power saving amount. If it is less than 5 minutes, there is a possibility that the amount of time during which the action of reducing the unbalanced current by the balancer works is too short to calculate the power saving amount accurately. In addition, if it exceeds 30 minutes, the influence of the change in the usage state of the power due to the time zone becomes large, and it becomes difficult to calculate an accurate power saving amount.

The three-phase four-wire power distribution system of the present invention includes a three-phase power line, a neutral line, and a balancer that reduces unbalanced current flowing through the neutral line to the three-phase power line. It has a capacity determined by the maximum value of the neutral current flowing through the line to which the balancer is connected and the maximum voltage applied to the power line, and the balancer is connected to the end of the line.
Preferably, the balancer is connected to a line to which the maximum power is applied among powers measured at a plurality of locations including a line branched from the line.

The three-phase four-wire distribution system opens and closes intermittently at predetermined time intervals for measuring the power applied to the line to which the balancer is connected in order to obtain a comparative day load curve. It further includes a switch, and the balancer is connected to the termination via the switch, and the power saving power is calculated from the comparative daily load curve.
The time interval for opening and closing the switch is preferably 5 to 30 minutes.
The balancer is composed of, for example, a zigzag star connection transformer.

(1) Measure the neutral current of the line connecting the balancer, calculate the capacity of the balancer connected to the end of the line from the measured maximum value of the neutral current and the maximum voltage used for the line, By connecting the balancer having the capacity to the end of the line, the balancer can be appropriately arranged in the three-phase four-wire distribution system, and energy efficiency can be improved efficiently at low cost. Further, in the present invention, greenhouse gas emissions can be reduced by improving energy efficiency, so that it is possible to apply a clean development mechanism (CDM: Clean Development Mechanism).

(2) Further, a line branched from the line by measuring power at a plurality of locations including the line branched from the line, and including a line connecting the balancer as the line having the maximum measured power. Even when the power of the balancer is large, it is possible to efficiently reduce the unbalanced current by the balancer by connecting the balancer to the end of the line where the power is maximum among the branched lines.

(3) A balancer is connected via a switch that opens and closes intermittently at a predetermined time interval, and the switch is intermittently opened and closed at a predetermined time interval, and the amount of power on the line to which the balancer is connected is measured. Even if there is no daily load curve by obtaining a load curve and calculating the power saving amount from the comparative daily load curve, the switch is closed, that is, the balancer is connected and the switch is open That is, it is possible to confirm the power saving effect by the balancer by obtaining the comparative daily load curve with the state where the balancer is not connected and calculating the power saving amount.

(4) Since the time interval for opening and closing the switch is 5 to 30 minutes, it is less affected by the change in the power usage state depending on the time zone, and a more accurate power saving amount can be calculated.

1 is a schematic configuration diagram of a three-phase four-wire power distribution system in an embodiment of the present invention. It is a figure which shows the connection location and measured value of an integrating watt-hour meter. It is a figure which shows the zigzag star connection transformer as a balance transformer. It is a figure which shows the example of a daily load curve. It is a figure which shows the relationship between the power consumption and the apparent power saving amount in the state without a balance transformer and the state with a balance transformer. It is a figure which shows the positional relationship of a measurement point. It is a figure which shows the graph of the average value of the electric current of each phase of R phase, S phase, T phase, and N phase at the time of the switch opening and closing of the balance transformer in the measurement point A of FIG. It is a figure which shows the graph of the average value of the voltage of each phase of R phase, S phase, T phase, and N phase at the time of the switch opening and closing of the balance transformer in the measurement point A of FIG. It is a figure which shows the graph of the average value of the electric current of each phase of R phase, S phase, T phase, and N phase at the time of the switch opening and closing of the balance transformer 1 in the measurement point B of FIG. It is a figure which shows the graph of the average value of the voltage of each phase of R phase, S phase, T phase, and N phase at the time of the switch opening and closing of the balance transformer 1 in the measurement point B of FIG. It is a figure which shows a simulation test circuit. It is a figure which shows the test result by the simulation test circuit shown in FIG. It is a schematic block diagram of the conventional three-phase four-wire type power distribution system.

FIG. 1 is a schematic configuration diagram of a three-phase four-wire power distribution system according to an embodiment of the present invention.
As shown in FIG. 1, the balancer disposition method of the three-phase four-wire distribution system in the embodiment of the present invention includes three-phase power lines (U phase, V phase, W phase) and neutral wires (N phase). A three-phase four-wire power-saving transformer (hereinafter referred to as “balance transformer”) 1 serving as a balancer is disposed at an appropriate location on a main line, a branch line, or the like of a three-phase four-wire distribution system comprising: Thus, the unbalanced current flowing in the neutral line is reduced to the three-phase power line, and the energy efficiency is efficiently achieved at a low cost. As the balance transformer 1, for example, a three-phase four-wire power saving transformer described in Japanese Patent Application Laid-Open No. 2007-48859 can be used.

As shown in FIG. 1, the three-phase power lines U, V, W and the neutral line N are electrically connected to the U-phase, V-phase, W-phase and N-phase of the three-phase four-wire transformer, respectively. Has been. Further, the power lines U, V, W and the neutral line N are electrically connected to the distribution board 10. Symbols r _U , r _V , r _W , and r _N in the figure indicate the electric resistances of the power lines U, V, W and the neutral line N, respectively.

Also, the motor M is electrically connected to the three-phase power lines R, S, T connected to the distribution board 10. An electric lamp (not shown) is electrically connected to one of the three-phase power lines R, S, T and the neutral line N. When the motor M is in operation, electric power is supplied to the motor M through the three-phase power lines U, V, and W. When the lamp is turned on, power is supplied to the lamp through one of the three-phase power lines R, S, T and the neutral line N.

FIG. 2 is a diagram illustrating an arrangement example of the balance transformer 1. In the balancer disposition method in the present embodiment, the balance transformer 1 is connected to the end of the line. In the example of FIG. 2, the balance transformer 1 is connected to the end of the trunk line. However, when the power of the branch line is maximum, the branch line having the maximum power is used as the line connecting the balance transformer 1. The balance transformer 1 is connected to the end.

Here, the principle of reducing the unbalanced current by the balance transformer 1 will be described. In the three-phase four-wire distribution system, a certain degree of unbalance is inevitable as described above. The voltage drop and the line loss increase as the load unbalance becomes more serious. However, the voltage drop and the line loss generated in the neutral line due to the zero phase occupy a large part. If the phase is removed, the load imbalance can be removed.

The zigzag star connection (staggered connection) transformer shown in FIG. 3 is used for the balance transformer 1 in the present embodiment. In a zigzag star-connected transformer, the magnetomotive force due to the zero-phase current cancels out at each leg of the transformer core, so no zero-phase magnetic flux is generated and the zero-phase impedance is very small. In the zigzag star connection transformer, the zero phase portion of the terminal voltage is short-circuited, and a zero phase current equal to each phase flows, thereby acting as a balancer.

Here, the secondary winding impedance, balancer impedance, and balancer circuit reactance components of the transformer (TR) of the substation shown at the left end of FIG. 2 are small and ignored. The line resistance R _{L of} each phase and the line resistance R _n of the neutral line are canceled by the current (balancer current) I _B from the balance transformer 1, and the power saving amount P ′ is expressed by the following equation.
P ′ = 3R _L × (I _B ) ² + R _n × (3I _B ) ² ... Formula (1)
The balancer current I _B that cancels the zero-phase current of each phase is

It becomes. here,
Z _T: transformer impedance Z _L: low-voltage distribution line impedance Z _n: neutral wire impedance Z _B: Balancer impedance Z _L ': the balancer connecting line impedance Z _n': balancer neutral point connecting line impedance I _n: zero-phase current It is. If Z _B , Z _L ′ and Z _n ′ are small and can be ignored,
I _B = 1/3 × (I _n )
It becomes.

Therefore, the capacity of the balance transformer 1 to be installed measures the neutral current of the line connecting the balance transformer 1 (zero-phase current I _n), the maximum operating voltage of the maximum value and the line of the measured neutral current From the above, the following formula can be used.
Balance transformer capacity = maximum neutral wire current x maximum operating voltage (3)

Therefore, when installing the balance transformer 1, first, an integrated watt-hour meter (WHM) 2 as a measuring instrument capable of measuring the electric energy (WH) is connected to a plurality of locations on the line to which the balance transformer 1 is connected. In the example shown in FIG. 2, the integrated watt-hour meter 2 is connected to several points on the main line including the point immediately before the balance transformer 1, the transmission point from the substation to the main line, and the intermediate point of the main line. As the integrated watt-hour meter 2, for example, a clamp wattmeter (model number: 3169) manufactured by Hioki Electric Co., Ltd. can be used. This integrated watt-hour meter 2 can measure voltage, current, active / reactive / apparent power, active / reactive power, power factor, frequency, and harmonics. Via a computer (not shown).

Thus, the balance transformer 1 whose capacity is determined by measuring the neutral line current is connected to the end of the line of the three-phase four-wire distribution system.

Then, the switch of the balance transformer 1 is intermittently opened and closed at predetermined time intervals, and the power amount, each phase current, and each phase voltage of the line to which the balance transformer 1 is connected are measured and compared as shown in FIG. Obtain a daily load curve. The measurement is performed for at least about one week. As shown in FIG. 4, the comparative day load curve shows that the wattmeter reading in the state where the switch of the balance transformer 1 is opened, that is, the state where the balance transformer 1 is not used is a continuous line, and the switch of the balance transformer 1 is closed In this state, the accumulator reading in the state with the balance transformer 1 is a continuous line.

The apparent power saving amount B is calculated on the computer from the difference between these two daily load curves. FIG. 5 shows the relationship between the power consumption and the apparent power saving amount when the balance transformer 1 is not present and when it is present. As shown in FIG. 5, when the balance transformer 1 is not provided, the reading of the power meter represents the sum of the consumed power [1] of the consumer and the line loss [2]. On the other hand, when the balance transformer 1 is provided, the reading of the wattmeter is the sum of the power used by the customer (1) (the power used increases by voltage compensation), the line loss (2), and the balancer loss (3). To express.

Based on the number of power distribution networks in the target area, the power saving amount of the entire target area is estimated from this power saving amount, and the power consumption per substation is calculated from the power consumption (kWH) and power saving amount (kWH) of the substation. The power saving amount (kWH / kWH) is calculated. Also, the annual power saving amount is calculated from the daily total power amount of the substation, and the connection location of the balance transformer 1 is determined from the power saving amount.

The power saving amount was measured using the balance transformer 1. FIG. 6 is a diagram showing the positional relationship of measurement points. As shown in FIG. 6, the measurement is performed at the distribution line terminal position, that is, the position of the final power pole (measurement point A) and the position of the balance transformer 1 (measurement point B) connected by extending 8 m wiring from the final power pole. Connected the vessel.

FIG. 7 is a graph showing an average value of currents in the R phase, S phase, T phase, and N phase when the balance transformer 1 is opened and closed at the measurement point A in FIG. 6, and FIG. 8 is an average voltage value. FIG. 9 is a diagram showing a graph of average values of currents in the R phase, S phase, T phase and N phase when the switch of the balance transformer 1 is opened and closed at the measurement point B in FIG. 10 is a graph showing an average value of voltage.

As can be seen from FIG. 9, when the switch of the balance transformer 1 is closed (CB ON), the N-phase current is divided and returned to the R-phase, S-phase, and T-phase. As a result, as shown in FIG. 8, when the switch is opened (CB OFF), the voltages of the R phase, S phase, and T phase, which are greatly unbalanced from 190V to 270V, are close to each other and around 230V. It can be seen that it is stable and the unbalanced state is improved.

Next, the optimal mounting position and appropriate capacity of the balance transformer 1 were verified.
As a result of an experiment using a theoretical calculation simulation circuit, it was found that the balance transformer 1 is installed at the optimum position when the distribution line system has the same trunk line size and when the distribution system is an evenly distributed load circuit. In the case of a concentrated load circuit at the end, the end installation was optimal. FIG. 12 shows the result of analyzing a simulation test on the optimum mounting position of the balance transformer 1 using the circuit shown in FIG. 11 and analyzing the measured data. In FIG. 11, B is a balance transformer 1. As can be seen from FIG. 12, the power saving amount is maximized when the balance transformer 1 is installed at the end.

The method of arranging the balancer in the three-phase four-wire distribution system of the present invention is useful as a method for saving power and energy in the three-phase four-wire distribution system.
The three-phase four-wire power distribution system of the present invention is also useful for power saving and energy saving.
The present application claims priority based on Japanese Patent Application No. 2008-007888 filed on Jan. 17, 2008, and the entire disclosure of the specification, claims, drawings and abstract is incorporated by reference in its entirety. Incorporated in the description.
Although the invention has been described with reference to particular embodiments, it is to be understood that the subject matter of the invention is not limited to those particular embodiments. On the contrary, the subject matter of the present invention is intended to include all alternatives, modifications and equivalents within the spirit and scope of the appended claims.

Explanation of symbols

1 Balance transformer 2 Integrated watt-hour meter (WHM)

Claims

A balancer disposing method comprising disposing a balancer for reducing an unbalanced current flowing in the neutral line to the three-phase power line on a line of a three-phase four-wire distribution system including a three-phase power line and a neutral line. There,
Measuring the neutral current of the line connecting the balancers;
Calculating the capacity of the balancer connected to the end of the line from the measured maximum value of the neutral line current and the maximum working voltage of the line;
A balancer disposition method in a three-phase four-wire power distribution system including connecting the balancer having the calculated capacity to the end of the line.
Measuring power at multiple locations including a line that branches off from the line;
The balancer disposing method in the three-phase four-wire power distribution system according to claim 1, wherein the line having the maximum measured power is a line connecting a balancer.
Connecting the balancer via a switch that opens and closes intermittently at predetermined time intervals;
Intermittently opening and closing the switch at a predetermined time interval, and measuring a power amount of a line connected to the balancer to obtain a comparative day load curve;
The balancer disposition method in the three-phase four-wire distribution system according to claim 1, comprising calculating a power saving amount from the comparative daily load curve.
Connecting the balancer via a switch that opens and closes intermittently at predetermined time intervals;
Intermittently opening and closing the switch at a predetermined time interval, and measuring a power amount of a line connected to the balancer to obtain a comparative day load curve;
The balancer disposition method in the three-phase four-wire power distribution system according to claim 2, comprising calculating a power saving amount from the comparative daily load curve.
The method of arranging a balancer in a three-phase four-wire power distribution system according to claim 3, wherein the time interval for opening and closing the switch is 5 to 30 minutes.
The method of arranging a balancer in a three-phase four-wire distribution system according to claim 4, wherein the time interval for opening and closing the switch is 5 to 30 minutes.
Three-phase power lines,
Neutral line,
A balancer that reduces the unbalanced current flowing through the neutral line to the three-phase power line;
The balancer has a capacity determined by the maximum value of the neutral current flowing through the line to which the balancer is connected and the maximum voltage applied to the power line,
The three-phase four-wire power distribution system including the balancer being connected to the end of the line.
The three-phase four-wire distribution system according to claim 7, wherein the balancer is connected to a line to which maximum power is applied among power measured at a plurality of locations including a line branched from the line.
In order to obtain a comparative day load curve, further comprising a switch that opens and closes intermittently at a predetermined time interval for measuring the power applied to the line to which the balancer is connected,
The balancer is connected to the termination via the switch;
The three-phase four-wire power distribution system according to claim 7, wherein power saving power is calculated from the comparative daily load curve.
In order to obtain a comparative day load curve, further comprising a switch that opens and closes intermittently at a predetermined time interval for measuring the power applied to the line to which the balancer is connected,
The balancer is connected to the termination via the switch;
The three-phase four-wire power distribution system according to claim 8, wherein power saving power is calculated from the comparative daily load curve.
The three-phase four-wire power distribution system according to claim 9, wherein the time interval for opening and closing the switch is 5 to 30 minutes.
The three-phase four-wire distribution system according to claim 10, wherein the time interval for opening and closing the switch is 5 to 30 minutes.
The three-phase four-wire distribution system according to claim 7, wherein the balancer comprises a zigzag star connection transformer.
The three-phase four-wire power distribution system according to claim 8, wherein the balancer comprises a zigzag star connection transformer.
The three-phase four-wire power distribution system according to claim 9, wherein the balancer comprises a zigzag star connection transformer.
The three-phase four-wire distribution system according to claim 10, wherein the balancer comprises a zigzag star connection transformer.
The three-phase four-wire distribution system according to claim 11, wherein the balancer comprises a zigzag star connection transformer.
The three-phase four-wire power distribution system according to claim 12, wherein the balancer comprises a zigzag star connection transformer.