JP2842895B2 - Low-side load switching method of transformer between different banks - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for switching a low-voltage load of a distribution transformer such as a pole transformer.

[Prior Art] With the development of a highly information-oriented society, demands for a stable supply of electric power are increasing. In addition, it is becoming difficult year after year for the power outage of the construction, and it is proposed and implemented that the construction be performed without causing the power outage of the customer. For example, as shown in FIG. 2, when the pole transformer Trb of one of the banks B of the banks A and B is replaced, the load LB of the bank B is switched to the bank A and the construction of the bank B is performed. Also, power is supplied from the bank A to the load LB of the bank B, and after the construction is completed, the load LB is switched back to the bank B.

As a method of switching the load LB of the B bank to the A bank, the low voltage switch LS connected to the low voltage side of the B bank automatically switches (within 10 msec) when the load side becomes no voltage. There is a method in which a switching switch S2 having a closing action is connected in parallel, a switching switch S2 having the same configuration as described above is connected to a branch point of both banks A and B, and switching is performed according to the following operation.

The switching switch S1 is turned on manually. Turn off the low-voltage switch LS by manual operation. The switching switch S1 is turned off by manual operation. Switching switch S
2 detects that the load LB side has become no voltage, and
(within sec), the current IA flows from the bank A to the load LB side.

There is also a method of switching the load LB switched to the bank A back to the bank B according to the following operation.

The switching switch S2 is turned off by manual operation.
The switching switch S1 detects that the load LB side has become no voltage, and is instantly turned on (within 10 msec), and the switch LB is switched to the load LB side.
The current IB flows from the bank. Low pressure switch LS
Is turned ON by manual operation. The switching switch S1 is turned off by manual operation. Remove the switching switches S1 and S2.

[Problems to be Solved by the Invention] However, in the above method, the secondary side (low voltage side) of the transformer is used.
Therefore, there is a problem that this method cannot be performed in a system without a low-voltage switch (low-voltage branch box) on the low-voltage side of the transformer. Also,
There is a problem in that two switching switches are required, and it takes time to connect the switching switches and to remove them after the construction is completed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to implement the present invention even in a system without a low-voltage switch (low-voltage branch box) on the low-voltage side of a distribution transformer. A low-side load switching method for a distribution transformer that prevents voltage drop, transformer overload and loop current increase when both banks are closed loop, and suppresses load-side voltage drop. Is to do.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides one low voltage distribution line connected to a high voltage wiring via a transformer, and another low voltage distribution line connected to a high voltage distribution line via another transformer. When switching the load of one distribution system to another wiring system by using a bypass cable connected to another low-voltage distribution line that is connected by a switching switch that can be opened for each phase, A switch that switches between the low-voltage side of the system and a saturated reactance circuit that has the characteristic of suppressing the increase in loop current and the voltage drop on the load side by reducing the reactance due to magnetic saturation of the iron core in a region above a certain current value. The gist of the present invention is to open the primary cutout of the one power distribution system after connecting via a series circuit and turning on the switching switch.

[Operation] Therefore, in order to switch the load of one bank to the other bank, the load is switched by turning on the switching switch and then sequentially opening the primary cutout of one bank.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, one of the banks A and B
When switching the load of the bank to bank A, the transformer Tra, Tr
The switching switch S and the saturation reactor circuit L are connected in series by using a bypass cable K between the low voltage sides of both the A and B banks to which the primary cutout PCs are connected for each of the phases U, V and W on the high voltage side of b. The circuit is connected.

The switching switch S is provided with three-phase switching units SU, SV, and SW corresponding to the three-phase distribution lines U, V, and W on the power supply side, and is configured to be manually turned on and off.

The three-phase power distribution lines U, V,
Three-phase cored coils LU, LV, LW are provided corresponding to W. When the current flowing through these coils LU, LV, LW increases, the inductance of the coils LU, LV, LW decreases due to magnetic saturation of the iron core. Is set in advance.

Next, in order to switch the load LB of the B bank to the A bank, the switching units of each phase of the switching switch S are manually operated from the standby state in which the switching units SU, SV, SW of the switching switch S are opened. SU, SV, and SW are sequentially input. At this time, the switching switch S constitutes a closed loop passing through the transformers Tra and Trb, but the inductance of the saturation reactor circuit L prevents the transformers Tra and Trb from overloading and increasing the loop current.

And the primary cutout PCU, PC of Bank B
V and PCW are sequentially released by manual operation. Then the load LB
, The switching switch S and the saturation reactor circuit L from the transformer Tra
, And the switching of the load LB of the bank B to the bank A is completed. Further, although the current flowing through the saturation reactor circuit L increases, the reactance of the saturation reactor circuit L decreases due to this current, so that the voltage drop by the switching switch S is limited. As a result, the effect on the load LB is reduced.

Next, when the load LB of the bank B is switched back from the bank A, the primary cutout PCU, PCU of each phase of the bank B is used.
Input V and PCW to make both A and B banks a closed loop circuit. At this time, the overload of the transformers Tra and Trb and an increase in the loop current are prevented by the saturation reactor circuit L at the same time as the switching. Thereafter, the switching switch S is opened manually. Thus, power is supplied to the load LB of the B bank from the transformer Trb of the B bank.

As described above, unlike the related art, there is no need to provide a low-voltage switch, and the number of switching switches S can be reduced to one.

Further, by providing the saturation reactor circuit L, A, B
When both banks are closed loop circuits, an increase in loop current and an overload of the transformers Tra and Trb can be prevented.
Further, even when the primary cutout PCU, PCV, PCW of each phase is opened at the time of switching, the voltage drop can be prevented by the coils LU, LV, LW.

Furthermore, compared to the method of looping through both low-voltage transformers with tap switching to both A and B banks, the saturation reactor circuit L
Is small.

The closer the inductance of the coils LU, LV, LW of the saturation reactor circuit L to 0 by increasing the current, the closer the load L
The voltage drop to A and LB can be reduced.

Note that the present invention is not limited to the above-described embodiment, and can be arbitrarily changed without departing from the spirit of the present invention.

[Effects of the Invention] As described above in detail, according to the present invention, even in a system without a low-voltage switch (low-voltage branch box) on the low-voltage side of the distribution transformer, the load of one bank can be switched to the other bank. it can. In addition, since only one switching switch is required during the switching operation, the labor for connecting the switching switch and removing it after the construction is reduced.

Further, the reactor circuit can prevent an increase in loop current, an overload of the transformer, and the opening of the primary cutout, thereby preventing a voltage drop on the load side.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment embodying the present invention, and FIG. 2 is an electric circuit diagram showing a conventional method. PC, PCU, PCV, PCW …… Primary cutout, S ……
Switching switch, L: Saturated reactor circuit, LA, LB: Load.

Continuing from the front page (72) Inventor Hiroshi Watanabe 1st character, Inariyama-shi, Aichi Prefecture Energy Support Co., Ltd. (56) References JP-A-57-34731 (JP, A) Jpn. U) Japanese Utility Model Showa 50-15336 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02J 3/00-5/00

Claims (1)

(57) [Claims] 1. Each phase between one low-voltage distribution line connected to high-voltage wiring via a transformer and another low-voltage distribution line connected to another high-voltage distribution line via another transformer. When switching the load of one distribution system to another distribution system by using a bypass cable connected by a switching switch that can be opened to the switch, the switching switch between the low-voltage side of both distribution systems and a certain current value or more In the region, the reactance is reduced due to the magnetic saturation of the iron core, and the loop switch is connected through a series circuit with a saturated reactance circuit having a characteristic of suppressing an increase in the loop current and a voltage drop on the load side, and the switching switch is turned on. Then, a low-voltage side load switching method of a transformer between different banks to open a primary cutout of the one distribution system.