JPH0793787B2 - Three-phase three-wire type low-voltage distribution line different phase live line switching system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention switches and connects a three-phase load connected to a low-voltage distribution line of a three-phase V-connection power transformer bank to a low-voltage distribution line of a different bank as a live line. As a result, the voltage difference between the left and right conductors facing the different bank butts can be connected by connecting them while eliminating the voltage difference by the interconnection transformer, and the left and right systems can be operated in parallel before switching. The present invention relates to a different-phase hot line switching system of a three-phase three-wire low-voltage distribution line in which a three-phase V-connection transformer on the side is disconnected.

[Background Art and Problems to be Solved by the Invention]

The three-phase three-wire type distribution line (usually 200V) that functions as a power source for electric power such as an electric motor is the same three-phase high-voltage distribution system (usually 600V).
Power is supplied from a three-phase V-connection power transformer that is properly connected to V). Furthermore, the abutting points of the low-voltage side line conductors of these adjacent banks are privately installed on the same utility pole in an open state, but the grounding-side electric wire described below is an aerial joint ground wire, and is a continuous distribution line grounding network over a wide area. I am configuring. Fig. 6 shows the connection between the three-phase three-wire high-voltage line and the three-phase V-connection power transformer (two pairs of pole transformers), and Fig. 4 shows the three-phase three-wire high-voltage line and the three-phase V-connection power. The connections with transformers (two pole transformers in one set) are classified and arranged based on the difference in phase connection, and L' _A , L' _B , L' _C are three-phase three-wire type. Line conductors that compose a high-voltage distribution line, T _i (i = 1,2,3,4,5,6)
Is a three-phase V-connection power transformer, and _i is a number that identifies the type of phase connection. In addition, X _i , Y _i , and N _i are line conductors that constitute a low-voltage three-phase three-wire distribution line, and N _i is called a medium-line conductor (ground-side electric wire) and is usually near the three-phase V-connection power transformer T _i . Grounded at. L' _AN , L' _BN , L' _CN are high-voltage side line conductors L' _A ,
L' _B , L' _C and the middle line connecting the high-voltage side (primary side) middle point of the V-connection transformer T _i , and L _AN , L _BN , L _CN are the low-voltage side middle lines corresponding to them. .

The line voltage of these low-voltage distribution lines is, of course, the same (normally 200V) in each bank, but when the high-voltage side middle line is connected to high-voltage line conductors of different phases, respectively. Therefore, the phases of the voltages of the line conductors of these banks are naturally different. Of the six types of phase connections shown in Fig. 6,
And are adjacent to each other, and each has a three-phase load (not shown)
Were connected. Where V-connection transformer T ₁
When it is necessary to replace or disconnect from the temporary distribution line system for maintenance or inspection, avoid interruption of power supply to the load shared by the transformer until the work is completed. Therefore, the same load (in other words, the three line conductors connected to the same load) is quickly connected to the V-connection transformer.
Switching connection to the T ₆ side is required. However, as described above, since there is a voltage vector difference between the line conductors of both banks, it is dangerous and difficult to process this work as a live line. Therefore, first, after disconnecting the switched V-connection transformer T ₁ from the system, the load (that is, the line conductor to which the load is connected) must be switched and connected to the bank of the switching-V connection transformer T _6. I won't. Therefore, it was inevitable that a temporary power failure would occur for the load.

On the other hand, it is possible to consider a method of arranging a transformer having the same rating as the V-connection transformer T _{1 in} parallel at the same place as the V-connection transformer, connecting the primary and secondary windings of both transformers in parallel, and then disconnecting T _1. .
However, in many cases, it is very difficult to secure a space by this method, and the possibility of practical use is poor. Further, it involves a dangerous connection work on the high-voltage side and requires a large number of man-hours, which is not preferable in terms of safety and economy.

The same problem occurs when the V-connection transformer T ₁ is replaced or maintenance inspection is completed and the original load is switched back to the same side.

[Means and Actions for Solving Problems]

The present invention has been made in view of the above, and takes the following means in order to solve the above problems. That is, at the points where different banks meet, the pair of conductors of the left and right banks are connected to both terminals of each winding of the same transformer while eliminating the voltage difference between the opposing left and right line conductors by the interconnection transformer. The magnitude of the line voltage between the left and right banks is 200V, and the phase of the line voltage between the conductor pairs of the left and right banks is in phase by properly selecting the conductor combination in the left and right banks, as described later. Alternatively, since it is possible to find the ones having the opposite phases, the above-described connection is always possible, which enables the parallel operation of both the left and right systems. After realizing this state, the switched three-phase V-connection power transformer is disconnected. After that, to the original three-phase load, the three-phase power is continuously supplied from the switching-side three-phase V-connection power transformer via the interconnection transformer. After replacement of the transformer to be switched or maintenance work is completed, reconnect the transformer to the original low-voltage distribution system, then disconnect the interconnection transformer from the left and right banks,
Operate both independently.

Hereinafter, the different phase active switching system of the three-phase three-wire low-voltage distribution line of the present invention will be described in detail.

〔Example〕

Prior to the description of the embodiments, the voltages of the left and right line conductors facing the different bank butting points will be considered. Now, as shown in FIG. 3 (a), the three-phase V-connection power transformers T ₁ and T ₆ are respectively high voltage distribution line conductors L' _A , L' _B , L in the manners shown in and of FIG. 'phase is connected to _C, and those that share respectively adjacent zone. The middle points of the high-voltage side (primary side) of the V-connection transformers T ₁ and T ₆ are connected to the high-voltage side line conductors L ′ _B and L ′ _C having different phases via the medium line conductors L ′ _BN and L ′ _CN. Each is connected. Also, the low voltage side (secondary side) of the V-connection transformer T ₁
In the winding, the leftmost and rightmost terminals are the low voltage line conductor X ₁
, And Y ₁ , and the midpoint is connected to the midline conductor N ₁ , respectively. Similarly, in the secondary winding of the V connection transformer T _6, the leftmost and rightmost terminal to conductor X ₆ and Y _6, midpoint is respectively connected to the mid-line conductors N _6. The low-voltage side middle conductors N ₁ and N ₆ are both V-connection transformers 2
In addition to being grounded along with the midpoint of the next winding, it is connected and interconnected over a wide area and is installed at key points of the line, functioning as an aerial joint ground wire.

Now, the ground potential (phase voltage) of the high-voltage side line conductor is V ′, respectively.
_A , V ′ _B , V ′ _C, and the phases rotate in this order,
Conductor AB, BC, C-A voltage, respectively the between _{V 'AB, V' BC,} V '
_{When represented by CA} , the vector diagram of these voltages forms a closed equilateral triangle as shown in FIG. 3 (b). on the other hand,
The voltage of the low-voltage side line conductors X ₁ , Y ₁ , N ₁ , X ₆ , Y ₆ , N ₆ (thus the voltage at the winding end of the V-connection transformer 2 to which these conductors are respectively connected) is V _A1 , If V _C1 , V _BN , V _B6 , V _A6 and V _{CN are used} , the vector diagram of these voltages is as shown in (c) from the circuit diagram of FIG. 3 (a) and the vector diagram of (b). It is clear that Since the conductors N ₁ and N ₆ are both grounded and V _BN = V _CN = 0, the origin of each vector diagram in FIG. 3 (c) is the ground potential (zero potential), and each vector is It can be seen that it represents the ground voltage of the conductor (and the terminals of the transformer winding to which it is connected). The magnitudes of these vectors are equal (200V) and their phase angles increase by 60 °. Considering the voltage between the left and right conductors facing the abutting point, for example, the voltage V _X1-Y6 between the conductors X ₁ -Y ₆ is V _X1-Y6 = V _A1 -V _A6 = 200e ^{j 60} ° (V) or less. , _VX1-X6 | = | V _Y1-Y6 | = 200 3 (V), | V _Y1-X6 | = 400 (V) if displayed using the same symbols. Therefore, the voltage between the left and right conductors is 20
There are three types, 0V, 200 3V, and 400V. Conversely, if you find a conductor combination that makes 200V, conductors X ₁ and Y ₆ , and if you find a conductor combination that makes 400V, conductors Y ₁ and X ₆ Each can be identified. On the other hand, considering the line voltage of each conductor in both the left and right banks, V _X1-N1 = V _A1 V _Y6-X6 = V _A6 -V _B6 = V _A1 Therefore, V _X1-N1 = V _Y6-X6 Further, it can be seen that V _Y1-N1 = V _C1 , V _X6-N6 = V _B6 = -V _C1 Therefore, V _Y1-N1 = -V _X6-N6 = -V _X6-N1 . In this way, it is possible to always find a conductor pair having an in-phase or anti-phase line voltage in the right bank with respect to a conductor pair arbitrarily selected in the left bank. The above is a discussion of between and in the figure. In the case where the midpoint of the V-connection transformer is connected to the high-voltage side line conductors of different phases (for example,-,-in FIG. 4).
,-,-,-,-, -...), and the vector diagrams of the low-voltage side line conductors of the adjacent banks all have the same pattern as FIG. 3 (C), and all the above properties are maintained. .

FIG. 4 (a) shows the case where the phase connections shown in and of FIG. 6 are made in the adjacent banks. Low-voltage side line conductor X ₁ , Y
₁ , N ₁ , X ₂ , Y ₂ , N ₂ voltages (thus voltage of transformer winding terminals connected to these conductors) are V _A1 , V _C1 , V _BN , V _C2 , V _A2 , V respectively
Assuming _bN , these voltages are shown in FIG. 4 (a),
From (b), the vector diagram of (c) is immediately obtained. That is, the conductor voltage vector diagrams of the left and right banks overlap. When the middle point of the high voltage side winding of the V-connection transformer is connected to the same high voltage side line conductor in the adjacent bank (for example, in the phase connection shown in FIG. 6, −, −, −
In the case of the combination), the vector diagram of the line conductor voltage on the low voltage side has the same pattern as in FIG. 4 (c). In this case, for example, the fourth embodiment
Figure as indicated by the broken line (a), the left and right conductors _{(X 1 -Y 2, Y 1} -X 2,) connected directly to the, then three-phase V connection power of the switching side in the same potential Switching connection is possible by disconnecting the transformer from the grid.

FIG. 1 shows an embodiment of the present invention, in which T ₁ and T ₆ are three-phase V-connection power transformers on the switched side and the switched side, respectively, and the respective phase connections are the same as in FIG. 3 (a). The medium conductors N ₁ and N ₆ are directly connected to form an integral conductor. Other than that, the functions of the components indicated by the same symbols as in FIG. 3 (a) are the same as those in FIG. M ₁ and M ₆ are three-phase loads, T _L1 and T, connected to the banks of transformers T ₁ and T ₆ , respectively.
_L2 is an insulation transformer with a winding ratio of 1 (200V / 200V), which plays a role in connecting the left and right systems, and in that sense it can be referred to as an interconnection transformer. The _{P 11, P 12, P 13} , P 14 is the transformer T _L1,
P ₂₁ , P ₂₂ , P ₂₃ , and P ₂₄ mean the winding terminals of the transformer T _L2 , respectively. The black circle mark attached to one end of each winding of these isolation transformers T _L1 and T _L2 means that the voltage of the terminal marked with this mark has the same polarity in the primary and secondary windings. .
S _A1 and S _C1 are low-voltage switches (hereinafter referred to as switches) that connect and disconnect continuity between the leftmost and rightmost winding terminals of the low-voltage side winding of the V-connection transformer T ₁ and the low-voltage side conductors X ₁ and Y ₁ , respectively. Abbreviated), S _A6 , S _B6
Are switches which perform the functions corresponding to S _A1 and S _C1 in the bank of the V-connection transformer T ₆ , respectively. In the isolation transformer T _L2 , the primary and secondary windings have the same number of windings as described above, and both windings are connected in series. That is, it can be said that the insulating transformer T _L2 has the same function as the single-winding transformer T _A having an intermediate tap at the midpoint of the winding, as shown in FIG. Terminals P _21, P ₂₄ of the transformer corresponds to the terminal of the winding ends of the respective equivalent autotransformer T _A, respectively Y _1, Y
₆ (400V voltage is applied between the two). The terminals P ₂₂ , (and P ₂₃ ) correspond to the center taps of the equivalent autotransformer T _A , and are connected to the medium conductor N ₁ (and N ₆ ). The left and right windings of the isolation transformer T _L1 are connected to the left bank conductor pair X ₁ -Y ₁ and the right bank conductor pair X ₆ -Y ₆ , respectively.

In order to reach the configuration of FIG. 1, first, as shown by the broken line in the figure, all the switches S _A1 , S _C1 , S _B6 , and S _A6 are turned on, and the left and right systems are independent. To drive. Next, as shown in the figure, each winding terminal of the insulation transformers T _L1 and T _L2 is connected to each line conductor. In this case, terminal P ₁₃
-Leave the connection between conductor Y ₆ and terminal P ₁₄ (and terminal P ₂₄ ) -conductor X _{6 at the} end, and confirm that these terminals and conductors are at the same potential after all other connections are completed. It is desirable to secure the safety after connecting each other.

As is clear from the vector diagrams of FIG. 1 and FIG. 3 (C), the conductor X ₁ -N is provided between the winding terminals P ₁₁ -P _{12 of} the insulating transformer T _L1 .
Voltage V _A1 between ₁ is applied, the terminal P the same voltage is another winding
It is induced between _{13 and} P ₁₄ . On the other hand, the voltage between the conductors X ₆ -Y ₆ in the right bank is given by V _A6 -V _B6, which is the apparent street from a vector diagram V _A1 = V _A6 -V _N6. Therefore, both voltages are balanced and no change in the current distribution in the system occurs before and after the connection of the transformer T _L1 . In addition, a conductor N ₁ -Y ₁ is placed between the winding terminals P ₂₂ -P _{21 of the} insulation transformer T _L2 .
A voltage -V _C1 between them is applied, and this voltage is induced as it is to the terminals P ₂₄ -P ₂₃ of the other winding (hence the terminal P ₂₄ -conductor N ₁ ). As is clear from the vector diagram of FIG. 3 (C), −V _C1 = V _B6 , the induced voltage at the terminal P ₂₄ is balanced with the voltage of the conductor X ₆ (V _B6 ), and the isolation transformer T _L2 is connected. Does not change the current distribution in the system. Therefore, both systems continue to operate in parallel but independently.

Next, the switch S _A1 on the V-connection transformer T ₁ side to be switched is opened. However, since the insulation transformer T _L1 is continuously supplied with power from the V-connection transformer T ₆ side via the winding terminals P ₁₃ -P ₁₄ , the voltage at the terminal P ₁₁ does not change and the switched side is changed. Three-phase load M ₁
Is supplied with a regular voltage and current via conductor X ₁ .
Then, the switch S _C1 is opened. In this case also does not change the voltage of the terminal P ₂₁ for the same reason, the three-phase load M ₁ conductors Y ₁
The regular voltage and current are continuously supplied via. That is, the switched V-connection transformer T ₁ is completely disconnected from the three-phase load M ₁ , and then the three-phase load M ₁ is connected to the transformer T ₆ side via the interconnection transformers T _L1 and T _L2. The regular power is supplied from, and the switching connection is completed. There is no difference in effect even if the order of opening the switches S _A1 and S _C1 is reversed.

If replacement of the the transfer side V connection transformer T _1, or work of maintenance is completed, put the switch S _A1, S _C1,
The transformer is again connected to the line conductors X ₁ , Y ₁ , N ₁ . Both left and right systems restart parallel and independent operation. Next, the interconnection transformers T _L1 and T _L2 are removed, and the work of switching back the load is completed.

In the configuration of FIG. 1 described above, after the switching connection of the load (disconnection of the switched V-connection transformer) is completed and before the switching back operation is started again, the interconnection transformers T _L1 , T Supplied via _L2 . Therefore, these transformers require continuous rated capacity corresponding to the load power. For this reason, the interconnection transformer needs to have the same rating as the V-connection transformers T ₁ and T _6, and the device becomes large, which is not a good measure from the viewpoint of handling and economy.

FIG. 2 shows another embodiment in which this has been improved. After the interconnection of the left and right systems by the isolation transformer and the disconnection of the V-connection transformer on the switched side are completed, both isolation transformers (interconnection transformer) are immediately started. One side winding is disconnected from the line conductor at the same time, and after a moment, the left and right insulated conductors are directly connected.

The configuration of FIG. 2 is basically the same as that of FIG. 1,
Since the meanings and functions of the constituent elements indicated by the same symbols as in FIG. 1 are not different from those in the case of FIG. 1, description thereof will be omitted. CO
S, 31, and 32 are newly added components in the present invention, and COS (Change Over Switch) operates in conjunction with each other. 2
A switching switch composed of a plurality of switches S ₁ and S ₂ , and 31 and 32 are AC voltmeters for ensuring work safety. Here, the switch S ₁ is composed of a blade b ₁ , a neutral terminal N _1, and terminals 11 and 12 connected to an external circuit. b
_2, N _2, 21, 22 are respectively, a configuration element corresponding to b ₁ -12 of the switch S _2.

At the time of load switching work, as shown by the broken line in FIG.
Set switches S _A1 , S _C1 , S _B6 , S _A6 to the ON state, and
The switches S _1, S ₂ of the inner, respectively the neutral Tenko N _1, N isolation transformer in a state of tilted _two connections (interconnection transformer) T _L1, T _L2 each line conductor as shown in FIG. To do. Then check the indications on voltmeters 31 and 32. If the indications are both zero, then 12−b ₁
During (terminal P ₁₄ - conductor X ₆ between) and between 22-b ₂ (terminal P ₁₃ - conductor
It becomes clear that (between Y ₆ ) is at the same potential, and it is possible to confirm that the work was done correctly. After that, if the blades b ₁ and b ₂ are interlocked with the terminals 12 and 22 side, respectively, they are brought down to the parallel and independent operating state of both left and right systems as in the case of FIG. Then, by opening the switch S _A1, S _C1 in the transfer side V connection transformer T ₁ side, detach from the conductors X _1, Y ₁ and T _1, then immediately switch S _1, the blade b ₁ of S _2, b ₂ Are switched to terminals 11 and 21 side instantly. As a result, the one-sided windings of the insulation transformers (interconnection transformers) T _L1 and T _L2 are separated from the line conductors X ₆ and Y _6, and the interconnection between the left and right systems is released. Furthermore,
Since the b ₁ -11 and b ₂ -21 is in direct contact, the conductor Y ₁ -X ₆ through these contacts, the X ₁ -Y ₆ is respectively connected to directly,
The regular voltage and current are supplied from the V-connection transformer T ₆ side to the three-phase load on the switched side, and the load switching connection work is completed.
While the blade b ₁ (b ₂ ) of the switch S ₁ (S ₂ ) switches from the terminal 12 (22) to the terminal 11 (21), the voltage supply to the three-phase load M ₁ is interrupted. The time is extremely short, and the three-phase load is often an electric motor, and due to its mechanical inertia, there is a residual effect of circuit voltage even for momentary loss of power supply. The above obstacles are extremely few. Further, the interconnection transformers T _L1 and T _L2 function only after the V-connection transformer T ₁ is disconnected and then the switching switch COS (switches S ₁ and S ₂ )
Since it takes a short time to complete the switching operation, the capacities of these transformers should be determined based on the short-time rating.
Compared to the case shown in the figure, it is possible to make it much smaller and more economical.

After replacement of the switched transformer T ₁ or maintenance work is completed, the blade b of switch S ₁ (S ₂ ) b
Switch ₁ (b ₂ ) to the terminal 12 (terminal 22) side. Both the left and right systems operate again via interconnection transformers T _L1 and T _L2 . Immediately thereafter, the switches S _A1 and S _C1 are turned on on the low voltage side of the V-connection transformer T ₁ . Thus, the left and right systems operate in parallel and independently. Then switch S
₁ side winding of (S ₂₎ of the blade b ₁ be switched (b ₂₎ a to the terminal N ₁ (N ₂₎ interconnection transformer T _L1, T _L2 is disconnected from the line conductor X _6, Y _6, left and right The interconnection of both systems is released, and the three-phase load M ₁
The switching back work is completed.

According to the configurations of FIGS. 1 and 2 described above, unlike the case of the hot-line switching method of the single-phase three-wire distribution line, the circuit is forcibly short-circuited, the interconnection operation of a large number of opening / closing means, the adjustment of the timing, etc. No complicated operation is required, and the hardware used can be remarkably simplified. Moreover, all work can be processed in the low-voltage system, which is excellent in terms of safety and speed.

Further, in FIG. 1 and FIG. 2, as the interconnection transformer T _L2 ,
Although an isolation transformer in which the secondary and secondary windings are connected in series is shown, it may be replaced by an autotransformer (for example, a balancer) as shown in FIG.

Further, in the adjacent banks, when the medium line on the high-voltage side of the V-connection transformer is connected to the high-voltage line conductors having different phases, the vector diagram of the low-voltage line conductors facing left and right of different banks is As described above, it is similar to that of FIG. 3 (C). Therefore, the configuration shown in FIG. 1 and FIG.
It can be applied to other combinations having different phase connections.

The switching switch (COS) is not limited to the movable type (electromagnetic type), but if a static type (triac, etc.) made of semiconductor is applied, the switching will be faster and more stable. Can be expected to work.

〔The invention's effect〕

As described above, according to the different-phase hot-line switching method of the three-phase three-wire low-voltage distribution line of the present invention, the voltage between the low-voltage side line conductors of the left and right systems facing the different bank abutment points is changed by the interconnection transformer. While eliminating these problems, after connecting these conductors to enable parallel operation of both left and right systems, the three-phase V on the switched side
Since the connection power transformer is separated from the grid, it is considered to be a method of hot line switching.Temporary installation of a low-voltage circuit breaker that bypasses the low-voltage switch to cut off the load from the switched-side transformer immediately before the interconnection point is turned on. It becomes possible to switch the three-phase load to the three-phase three-wire type distribution line of a different bank safely and promptly as a live line by using a relatively simple and inexpensive device.

Further, as described in the latter part of the specification, after disconnecting from the V-connection transformer on the switched side and switching to the state in which power is supplied to the load on the switched side via the interconnecting transformer, immediately the interconnecting transformer is switched by the switching switch. According to the method of disconnecting the transformers and connecting the conductors of the left and right banks directly after a moment, the time of power supply via the interconnection transformer is significantly shortened, so the capacity of the interconnection transformer is It suffices to set it based on the short-time rating. Therefore, the interconnection transformer can be downsized, and great improvement can be expected in terms of both economical efficiency and easy handling.

[Brief description of drawings]

FIG. 1 ... A diagram showing an embodiment of the present invention. Fig. 2 ... 1st
The figure which shows the Example which improved a part of thing of the figure. 3 (a) to 3 (c) ... Explanatory diagrams for considering the voltage of the low-voltage line conductors when the high-voltage side middle lines of the adjacent banks are connected to the high-voltage line conductors of different phases (a). Is the connection diagram,
(B) is a vector diagram of a high voltage line conductor voltage, (C) is a vector diagram of a low voltage line conductor. 4 (a) to (c) ...
It is explanatory drawing for considering the voltage of the low voltage | pressure line conductor in case the high voltage | pressure side center line conductor of an adjacent bank is connected to the high voltage | pressure line conductor of the same phase, (a), (b), (c) is a Same as Fig. 3 (a), (b), (c). FIG. 5: An explanatory diagram showing an equivalent circuit of the insulation transformer. FIG. 6 ... Explanatory diagram that classifies and arranges phase connections between the high-voltage line conductor and the primary side (high-voltage side) winding of the three-phase V-connection power transformer. Code table L' _A , L' _B , L' _C , ... High-voltage side line conductor, L' _AN , L' _BN ,
L _'CN ...... high voltage side in _{line, V' A, V 'B} , V' C ...... high side line conductor of the ground voltage (phase _{voltage), V 'AB, V'} BC, V 'AC ......
Line voltage of high voltage side line conductor, X _i , Y _i , N _i (i = 1,2,3,4,5,
6) ...... Low voltage side line conductor, N _i is medium line conductor, L _AN , L _BN , L _CN
… Low voltage side extensions, V _AI , V _BI , V _CI …… Low voltage side conductor ground voltage, V _AN , V _BN , V _CN …… Low voltage middle conductor ground voltage (voltage level), T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , T ₆ …… Three-phase V-connection power transformer, T _L1 , T _L2 …… Insulation transformer (coupling transformer) with a winding ratio of 1, T _A …… Equivalent Autotransformer, P ₁₁ ,, P ₁₂ ,, P ₁₃ ,, P ₁₄ ,, P ₂₁ ,, P
₂₂ , P ₂₃ , P ₂₄ …… Winding terminals of transformers T _L1 , T _L2 , M _i …… Three-phase load, S _AI , S _BI , S _CI …… Low voltage switch (switch), COS…
… Switching switch, S ₁ , S ₂ …… 3 circuit switches that compose COS, b ₁ , b ₂ …… Same blade, 11,12,21,22… Same terminal, N ₁ , N
₂ Neutral terminals, 31, 32 ... AC voltmeter.

Claims (3)

[Claims] 1. A three-phase three-wire load connected to a three-phase three-wire low-voltage distribution line of a three-phase V-connection power transformer bank belongs to the same high-voltage distribution system and has a different connection phase of the middle line. In the three-phase three-wire low-voltage distribution line of the three-phase three-wire low-voltage distribution line that is connected to the three-phase three-wire low-voltage distribution line of the power transformer bank as a live connection or switchback connection, the low-voltage middle line of the left and right banks Connect the conductor directly to ground,
The pair of left and right banks of conductors having the same phase and the same line voltage are connected to both terminals of the primary and secondary windings of an insulation transformer with a winding ratio of 1, respectively, and are connected to the ground of the same magnitude in the opposite phase. Connect the conductors of both left and right banks that have the potential to the terminals at both ends of the winding of the autotransformer, connect the midpoint of the winding to the midline conductor, and then connect the switched side or the switched side. The three-phase V
A different phase live line switching method for a three-phase three-wire low-voltage distribution line, characterized in that the connection power transformer is separated from the three-phase load. 2. The autotransformer is configured by connecting in series primary and secondary windings of an insulation transformer having a winding ratio of 1. A different phase live line switching method of the three-phase three-wire low-voltage distribution line described in the first term of the range. 3. The operation of disconnecting the three-phase V-connection power transformer from the three-phase load includes: when switching loads, disconnecting the insulation transformer and the single-winding transformer from the line conductor after switching, and immediately afterward The line conductors of the left and right banks corresponding to each other at the mating point are directly connected, and at the time of switching back the load, the line conductors corresponding to the phase at the butting point are disconnected, and immediately thereafter, the insulation transformer and the single winding are immediately disconnected. 3. The method according to claim 1, further comprising an operation of connecting the three-phase load to the switched three-phase V-connection power transformer after restoring the connection of the line transformer to the old one. Three-phase three-wire low-voltage distribution line different phase live line switching system.