JPS584446B2 - Fukaji Tatsupu Kirikaesouchinotameno Fukaki Rika Etsuchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a load changeover switch for an on-load tap changer of a voltage regulating transformer as described in the generic part of the claims.

This type of changeover switch is known, for example, from German Patent No. 88528.
No. 2, etc. 6 are publicly known.

However, such a changeover switch requires a zero-point switch that opens exactly six contacts at the instant when the current is zero.

This type of switch, which opens precisely at the moment the current passes through the zero point, requires high precision and is expensive to manufacture, so it has not been widely used in reality.

Furthermore, as a device for switching alternating current without arcing or with a small amount of arcing, an example using a semiconductor valve having parallel contacts and series contacts is known (ETZ-A Vol. 86, No. 15, 1965, 496-500). page).

This example also requires a synchronizing connection device that operates with high precision, and the responsibility of the arcing contact is only partially relieved by the parallel semiconductor elements.

The same holds true for known changeover switches for on-load tap-changing transformers using semiconductor devices (INeues aus der Technik, 1999).
961 No. 7.1-2 pages).

In this case, the contacts switching from one tap to another must carry out the switching process precisely and quickly within a half-wave period.

This means that this must be done within a half-wave period during which the semiconductor component connected in parallel to the continuous current contact can conduct.

In addition, in order to switch the taps of a load tap change transformer without arcing, a device is known that uses two sirisks on both load side branch paths (German Patent No. 163,847).
However, this device is not completely satisfactory.

That is, in this case, a short-circuit between the taps must be achieved by a contact with less chatter, and this short-circuit must also be used to ignite or interrupt the anti-parallel connected circuit in one of the load-side branches. Therefore, much cost is still required to control the risk and to switch the risk from one load-side branch to the other load-side branch.

It should be noted that the need for a short circuit between taps for switching is also not ideal.An object of the present invention is to increase the time interval for the operation of the changeover switch, that is, for the synchronous connection process. An object of the present invention is to provide an improved load changeover switch according to the generic part of the claims, such that the changeover switch can be manufactured at low cost.

This problem is solved by a load changeover switch according to the invention, which has the features described in the patent claims.

The use of a synchronously actuated transfer switch according to the invention makes it possible to achieve a switching process over two successive half-waves, and therefore does not require many requirements for its control and mechanical structure. becomes possible.

It is also sufficient to connect to each load branch only one controllable semiconductor element (Silisk) or only one set of series-connected controllable semiconductor elements.

Therefore, compared to other devices for load switching, there is no need to short-circuit between taps for load switching, and the cost of controllable semiconductor elements can be significantly reduced.

Semiconductor elements that can be fully controlled, ie, thyristors, are not too sly to conduct for only half a cycle at most, which increases the permissible current capacity and makes it possible to use the capacity effectively.

In a particularly advantageous embodiment, a diode is provided which is connected in anti-parallel to the additional current path, by which the impedance of the additional current path is matched to the respective sirisk branch and thus the additional current path is connected in antiparallel. In addition to improving the commutation of current from the to the silicate branch, a separate voltage sensor can be used to generate pulses for the synchronous switches and for the ignition of each silicate.

In addition, in order to improve commutation, and when the switching power is large, the contacts of the changeover switch operated synchronously can be configured such that each of the two contacts has two mutually insulated parts. .

In this case, one diode is connected to each part that remains in contact for a longer period of time.

In such a case, of course, the synchronous switch must be constructed so that the approximately 3-4 millisecond pulse required for switching arrives early.

Furthermore, in the unique configuration of the load transfer switch of the present invention, the switch, the diode, and the transfer switch are arranged together as one load transfer switch unit or assembly in a single cylindrical housing; The load changeover switch units are arranged rotatably around the periphery of the shape, in which case the load changeover switch unit is in sliding contact with six contact rings mounted on a cylindrical ring on the load side conductor on the one hand, and on the other hand with three sliding contacts arranged one after another at intervals. These contacts are made to slide along the elongated tap contacts provided around the cylinder when the load changeover switch unit rotates, and in that case,
The two external sliding contacts of the load changeover switch unit are configured as disconnecting contacts, the intermediate sliding contact is configured as a current-carrying contact, and in each drive position all three sliding contacts are configured as one tap contact. Let them face each other.

Hereinafter, specific examples of the present invention shown in the drawings will be explained.

As is clear from FIG. 1, the load changeover switch of the present invention essentially consists of two load branches A and B;
Each tap contact 1, I is connected to a lead-out conductor Y via these branches.

Each load branch A and B consists of a parallel connection of thyristors T1 and T2 with bypass switches 1 and 2.

Between the two load branches A and B there is a further current path C, which can be alternately connected in parallel with either branch A or B by means of a synchronously actuable changeover switch U.

As is clear from FIG. 2, the principle of operation of this load changeover switch is as follows.

Starting from the position shown in FIG. 1, disconnection contact 3 and current-carrying contact 1 are closed, and an additional current path C is connected in parallel to load-side branch A via a changeover switch connecting contact 5. has been done.

If the switching process is successful, first the current-carrying contact 1 is opened (the second
(see figure), whereby the current is diverted into an additional current path C.

As a preliminary step before the actual load switching, load side branch path B
The disconnection contact 4 of is closed.

Thereafter, the voltage sensor St located in parallel with the diodes D1 and D2 determines that the current has passed through the zero point, so that the thyristor T1 receives an ignition pulse and takes over the energization.

At the same time, a switching pulse for the synchronous switch U is generated.

This generation is expediently carried out by discharging the capacitor, and the electromagnet S of the changeover switch U responds to this pulse.

The changeover switch U then first leaves the contact 5, so that the partial current flowing in the additional current path C is then diverted to the now conducting thyristor T1.

The firing thyristor T1 becomes blocked on the next subsequent zero crossing and causes the firing of the thyristor T2 in the further load branch B.

Thus, at zero crossing, the current is switched from thyristor T1 to thyristor T2, and the load current is therefore switched from tap contact I to ■.

In the meantime, the changeover switch U is moved until it abuts the contact 6, during the same current half-wave period during which the thyristor T2 is taking up the current, so that the load current is immediately taken over again by the additional current path C. .

After 2-3 half waves, disconnection contact 3 is opened (see Figure 2).
From this point on, the load branch A, which was energized from the beginning, is de-energized.

Finally, the current-carrying contact 2 closes and the switching process ends.

As shown in Figure 3, the load changeover switch mentioned above has the following features:
They can be combined into one load changeover switch unit LU and rotatably disposed within a cylindrical housing, which is shown unfolded in FIG.

In this case, the cylindrical wall Z carries a ring-shaped sliding contact 7.

The load current drawing conductor Y of the load changeover switch unit or assembly is constantly in sliding contact with this contact point during rotation of the switch assembly.

The cylindrical wall has tap contacts I, n, I. It carries V, and these contacts are
Although not shown in detail, the sliding contacts 1 of the load transfer switch assembly are connected to the taps of the voltage regulating transformer and are configured as disconnecting and energizing contacts during rotation of the load transfer switch assembly. 3 and 4 are in sliding contact.

Sliding contact 1 that can be placed side by side with load changeover switch assembly
, 3.4, in this case the two outer contacts 3, 4 each act as a disconnecting contact, and the middle contact 1 acts as a current-carrying contact, in contrast to the double-carrying contacts 1, 2 in FIG. It is shaped to act as a contact point.

In the illustrated drive position, all three sliding contacts are
They are in contact with the same tap contact H.

Therefore, when switching to the next tap, for example tap contact 2, the load changeover switch assembly is swung along the cylindrical wall Z in the direction of the arrow.

In this case, the sliding contact 4 first leaves the tap contact ■,
Three tap contacts touch each other.

In the intermediate position, when the continuous contact 1 is located between the two tap contacts (2) and (2), the load switching from the two tap contacts (2) to (2) takes place as described in the example of FIG.

For clarity, Figure 3 shows the voltage sensor St.
Although not shown, its function is exactly the same as described in the main embodiment of FIG.

That is, at a suitable current zero crossing determined by the voltage sensor, the thyristor T1 is ignited and a pulse is generated to the change-over switch U, which passes through the change-over switch U for the same half-wave period of current that the thyristor T1 can carry. away from the hollow contact 5, so that at the next zero point passage of the current the current flows through the thyristor T1.
to thyristor T2.

That is, the tap contact ■ is switched to the tap contact ■.

During this half-wave period, during which the thyristor T2 is conducting, the changeover switch U has six contacts, so that the load current immediately passes through the additional current path C again.

Meanwhile, the rotational movement of the load changeover switch assembly continues such that first sliding contact 1 and finally sliding contact 3 contact tap contact 2.

The drive for the rotational movement of the load changeover assembly can in this case be constructed, as is customary, by means of a force storage device (spring device).

The smooth transition of the load transfer switch assembly from one tap contact to another is done slowly to ensure that the electronically controlled load transfer is accomplished at the correct time.

The changeover switch U is additionally provided with a mechanical changeover device, as shown in FIG. 4, whose role is to ensure that the changeover switch assumes the correct starting position immediately before each changeover. There are things to do.

Furthermore, the mechanical switching device makes it possible to complete the switching process even in current-free switching, for example when the transformer voltage has not increased.

The mechanical switching device consists of an activation force 8 mounted on the cylindrical wall Z, against which the control curve 9 runs against the rotation of the load changeover switch assembly.
As a result, the transfer switch is forced to another switch position.

According to the load changeover switch according to the present invention, each load branch path requires only one controllable semiconductor element or a group of series-connected controllable semiconductor elements, i.e., a group of anti-parallel elements. Costs are significantly reduced compared to conventional equipment.

Furthermore, since short-circuiting between taps is not required in the load switching process, there is less influence on the outside by circulating current, and control is simple.

Furthermore, since the thyristor is only energized during the half-wave period, it is possible to increase the allowable current.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the principle structure of the load changeover switch according to the present invention, Fig. 2 is a waveform diagram showing current changes in the load changeover switch in chronological order of operation, and Fig. 3 is a circuit diagram showing the basic structure of the load changeover switch according to the present invention. FIG. 4 is a diagram showing the details of the load changeover switch of FIG. 3, which is equipped with a forced operation mechanism for the changeover switch. The correspondence of the main reference symbols in the figure is as follows. 1, 2... Continuous current contact, St...
Ignition device, T1, T2... Cyrisk, A. B
...Current branch path, U...Synchronization changeover switch.

Claims (1)

[Claims] 1 A load changeover switch for an on-load tap changer for a voltage regulating transformer, including one energizing contact and having two load current branch paths connected between the transformer tap contact and the outgoing conductor. synchronous switching, in which the non-energized branch of the load current branch can be disconnected by means of a disconnection contact, and which can be selectively connected in parallel to any of these load current branches during the switching process; In a load changeover switch, an additional current branch comprising a switch is provided, and the load changeover switch is configured such that the opening and closing processes of the synchronous changeover switch take place within two successive half-waves; Thyristors T1 and T2 that can be controlled by the ignition pulses generated by the connected ignition device St are connected in parallel with the respective ignition contacts 1 and 2;
The thyristors T, T2 of both current branch paths A and B are connected in opposite directions, and the ignition device St is connected to the load current branch path connected by the synchronous changeover switch U. One of the thyristors T1 connected in parallel
; applying an ignition pulse to T2 at the beginning of a half-wave of the forward current of this thyristor, the ignition device St starting the switching process of the synchronous changeover switch U at the same time as the generation of the ignition pulse; Load change-over switch for an on-load tap changer, characterized in that the ignition device St gives a ignition pulse to the other thyristor T2; T1 at the beginning of the following half-wave.