JP2842896B2 - 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 side of a 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, when the pole transformer Trb of one of the banks B of the banks A and B is replaced as shown in FIG. 3, the load LB of the bank B is switched to the bank A, and the load B of the bank B is also changed during the construction of the bank B. Power is supplied from the bank A to the load LB of the bank, and the load LB is switched back to the bank B after the construction is completed.

As a method of switching the load LB of the B bank to the A bank, a low voltage switch LS connected to the low voltage side of the B bank and capable of opening and closing all three phases collectively corresponds to the case where the load side becomes no voltage. Opening / closing part is automatic in three phases at once (10ms
(within ec) A method of connecting switching switches S1 that perform a closing action in parallel, connecting a switching switch S2 with the same configuration as above to the branch point of both A and B banks, and switching according to the following operation There is.

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.

The load LB that has been switched to the bank A is switched back to the bank B according to the following operation.

The switching switch S2 is turned off by manual operation.
The switch S1 detects that the load LB side has become non-voltage, and is instantly turned on (within 10 msec), and the switch LB side is switched to the load LB side.
A current IB flows from the bank. The low-voltage switch LS is turned on manually. Switching switch S1 by manual operation
Turn off. 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 the purpose of the present invention can be implemented even in a system without a low-voltage switch (low-voltage branch box) on the low-voltage side of a transformer, and only one switching device is required. Further, it is intended to provide a transformer low-voltage side load switching method that prevents overload of the transformer and an increase in loop current when both banks are closed loop, and performs switching and switching back by detecting a voltage drop. is there.

[Means for Solving the Problems] In order to achieve the above object, the invention of the present application separates the low voltage side distribution line of one bank connected to the high voltage side distribution line via a transformer into a high voltage side distribution line. A load switching method between both banks using a circuit connected to the low-voltage side distribution line of another bank connected via the transformer of the non-contact switch, the overload protection element, and the parallel circuit of the second switch. A switching circuit comprising a first switch connected in series to the parallel circuit and connected between the low-voltage distribution lines of each phase of both banks;
With the first switch closed, the primary cutouts connected to the high-voltage distribution lines of each phase of the one bank are sequentially opened, and the contactless switch of the switching circuit and the second The gist is to close the switch.

[Operation] Therefore, in the present invention, the switching device is connected between the low pressure sides of both banks, and the primary cutout of one bank is sequentially opened. When the voltage drop of the opened phase is detected, the non-contact switch and the normally open switch become conductive, and the load is switched. When the detecting means detects a voltage drop in one bank, the non-contact switch and the normally open switch are closed.

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

As shown in FIG. 1, a primary cutout PC is connected to each of the phases U, V, W of the distribution line L on the high voltage side of the transformers Tra, Trb provided in both banks A, B. A switching device S is connected between the low-voltage sides of both the A and B banks via a bypass cable K for each phase.

As shown in FIG. 2, the switching circuit Sa of the switching device S has a normally open relay contact S1U, S1V, S1W as a first switch corresponding to each phase of the distribution lines U, V, W and Overload prevention resistors RU, RV and RW are connected to bypass cables K for each phase.
Are connected in series. Also, triacs 1, 2, and 3 as non-contact switches and relay contacts S2U, S2V and S2W as second switches of normally open type are respectively connected in parallel to the respective overload prevention resistors RU, RV and RW. It is connected to the.

Each of the gate terminals G of the triacs 1, 2, and 3 is connected to a relay circuit 4, and the first relay contacts S1U, S1V, S1W and the second relay contacts S2U, S2V, S
A relay MC that turns on and opens 2 W is connected to the relay circuit 4.

Each of the phases U, V, W of the distribution line L on the low voltage side of both the A and B banks is provided with a current transformer CT as a detecting means, and is connected to the relay circuit 4. This current transformer CT always detects the current on the low voltage side of the transformers Tra and Trb.

Further, a relay circuit 4 is connected between both terminals of the resistors RU, RV, RW, and the relay circuit 4 detects a voltage drop of the resistors RU, RV, RW.

A procedure for switching the load LB of the B bank to the A bank will be described. First, the switching device S is connected between the low voltage sides of both the A and B banks via the bypass cable K.

Then, the relay circuit 4 is driven to control the relay MC,
The first relay contacts S1U, S1V, S1W are turned on. At this time,
The first relay contacts S1U, S1V, S1W in the switching circuit Sa, the resistor RU,
A closed loop passing through RV, RW and transformers Tra, Trb is configured,
The resistors RU, RV, RW prevent the transformers Tra, Trb from overloading and increasing the loop current.

Subsequently, among the primary cutout PCs of the B bank, the primary cutout PCU of the U phase is first released by manual operation. Then, the power between the U and V phases is supplied only from the A bank through the RU and RV, and the relay circuit 4 reduces the voltage drop between the U and V phases on the B bank by the resistors RU and R connected to the bypass cable K. Detect via RV. The relay circuit 4 sends a signal to the gate terminal G of the triacs 1 and 2 of the U and V phases to turn on the triacs 1 and 2 and, under the control of the relay MC, the second relay contact S2 of the U and V phases.
U, S2V is introduced.

Next, the V-phase primary cutout PCV is manually opened.

Then, the electric power between the V-W phases is RU, RW from only the A bank.
, And the relay circuit 4 detects the voltage drop of the W-phase on the bank B side via the resistor RW connected to the bypass cable K. And the relay circuit 4 is W
A signal is sent to the gate terminal G of the triac 3 of the phase to turn on the triac 3, and the W is controlled by the relay MC.
Turn on the second relay contact S2W of the phase.

And the remaining W-phase primary cutout PCW
Is manually released.

As a result, the first relay contact S1U, S1V, S1W of the switching circuit Sa and the second relay contact S2 of the switching circuit Sa are connected to the load LB by the transformer Tra.
Power is supplied via U, S2V, S2W, and the load LB of bank B is
To the A bank is completed.

Note that, unlike the above, the order of releasing from the W-phase primary cutout PCW is as follows.

Primary cutout PCW open → Second relay contact S2V, S2W input → Primary cutout PCV open → Second relay contact S2U input → Primary cutout PCU
Open.

Note that release from the primary cutout PCV is not performed because a loop having a large phase difference is formed.

Next, a case where the load LB of the B bank is switched from the A bank to the B bank will be described.

First, the primary cut-out PC for the U phase of Bank B
Input U. Next, the V-phase primary cutout P
Inject CV. Then, a closed loop passing through the U and V phases of both the A and B banks is formed by inputting the U and V phases. At this time, an overload current flows in at least one of the U and V phases. And
When the current transformers CT connected to the U and V phases of both the A and B banks detect an overload current flowing through the distribution line L, the rerouting circuit 4 controls the relay MC based on this detection signal to Open the first relay contact S1U.

Subsequently, the W-phase primary cutout PCW is input. Then, by this input, a closed loop passing through the V and W phases of both the A and B banks is formed. At this time, an overload current flows through at least one of the V and W phases. When the current transformer CT connected to the V and W phases of both the A and B banks detects an overload current flowing in the distribution line, the relay circuit 4 controls the relay MC based on this detection signal to control the V and V. W-phase first relay contact S1
Release V and S1W.

In addition, the order of loading when loading from the W-phase primary cutout PCW is as follows.

Primary cutout PCW, PCV input → First relay contact S1W open → Primary cutout PCU input → First relay contact S1V, S1W open.

As a result, the transformer Tr of the B bank is connected to the load LB of the B bank.
Power is supplied from b.

Therefore, unlike the related art, there is no need to provide two low-voltage switches, and the number of switching devices S can be reduced to one.

Also, by providing the resistors RU, RV, RW in the switching circuit Sa,
When a closed loop circuit is formed between the banks A and B, an increase in loop current and an overload of the transformers Tra and Trb can be prevented.

Further, the triacs 1, 2, and 3 are connected to the second relay contacts S2U, S
Since it turns on faster than the closing of 2V, S2W is completed, it is possible to compensate only until the closing of the second relay contacts S2U, S2V, S2W is completed, that is, until the switching for each phase is completed. Instead, the load switching time can be shortened.

In addition, since the load is switched and switched back by the voltage drop of each phase via the resistors RU, RV, and RW, an instantaneous power failure can be eliminated.

It should be noted that the present invention is not limited to the above-described embodiment. In the present embodiment, the resistor is provided in the switching circuit. However, it is possible to change to a reactor instead.

[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 device is required for the switching operation, the labor for connecting the switching device and removing it after the completion of the construction is reduced.

Further, by providing the overload prevention element, it is possible to prevent an increase in loop current and an overload of the transformer.

Furthermore, not only can the compensation until the switching of each phase is completed by the non-contact switch, but also the load switching time can be shortened.

In addition, since the load is switched and switched back by the voltage drop of each phase, an instantaneous power failure can be eliminated.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is an electric circuit diagram showing a state in which a switching device is connected between both banks, and FIG. 2 is a configuration of the switching device. FIG. 3 is an electric circuit diagram showing a conventional method. A, B ... bank, 1, 2, 3 ... triac as non-contact switch, S1U, S1V, S1W ... first relay contact as first switch, S2U, S2V, S2W ... second Second relay contact as a switch, PC, PCU, PCV, PCW ... primary cutout, S ... switching device, Sa ... switching circuit, R
U, RV, RW: Resistance, LA, LB: Load, CT: Current transformer as detection means.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masayoshi Ito 1st character small needle in Inuyama City, Aichi Prefecture Energy Support Co., Ltd. (72) Inventor Hiroshi Watanabe 1st character small needle in Inuyama City, Aichi Prefecture Energy Support Corporation ( 56) References JP-A 60-88411 (JP, U) JP-A 62-51927 (JP, U) JP-A 60-138388 (JP, U) (58) Fields studied (Int. Cl. ⁶ , (DB name) H02J 3/00-5/00

Claims (1)

(57) [Claims] 1. A low voltage side distribution line of one bank connected to a high voltage side distribution line via a transformer, and a low voltage side distribution line of another bank connected to another high voltage side distribution line via another transformer. In a load switching method between both banks using a circuit connected to an electric wire, a method includes a parallel circuit of a contactless switch, an overload protection element, and a second switch, and a first switch connected in series to the parallel circuit. Is connected between the low-voltage distribution lines of each phase of both banks, and the primary cutouts connected to the high-voltage distribution lines of each phase of the one bank are sequentially connected with the first switch closed. A low-voltage side load switching method for a transformer between different banks, which is opened and the non-contact switch and the second switch of the switching circuit are closed based on a subsequent voltage drop.