Load increment switch

FIELD: electricity.

SUBSTANCE: switch comprises selector to select winding tap to be reswitched and load switch with at least one tap of current circuit and at least two auxiliary current taps; in each of them in load switch operating both with vacuum circuit breakers and switching cells, besides selector contacts, there are auxiliary switches connected in series with them and the respective winding tap, and in stationary mode the above auxiliary switches perform complete galvanic interruption of vacuum circuit breakers.

EFFECT: providing required dielectric strength to the load switch without increase in dimensions of vacuum circuit breakers.

5 cl, 3 dwg

 

The invention relates to a switch of load steps for a seamless switching of the winding branches of a stepped transformer.

Speed transformers known for many years; previously, they had to switch of load steps were mechanical contacts who worked in oil, nowadays many newer devices have vacuum switches.

The use of vacuum switches for switching of load steps prevents the occurrence of electric arcs in oil, and thus the pollution load switch oil. This ensures that maintenance needs to be done less often.

Switches of load steps with vacuum switches is known in many different schemes with 2, 3, 4, or also with a large number of commuting vacuum switches per phase.

The typical pattern, in this case with three vacuum switches, per phase, is described in DE 10 2007 004 530 A1.

However, in many applications such known switches of load steps with vacuum switches for control of power transformers high strength in relation to the pulse voltage up to 100 kV and above.

Such undesirable impulse voltages, the magnitude of which is in large PT�penalties due to the device step transformer and winding parts between the different levels of branches, are, on the one hand, the impulse voltage lightning that occur in the network after a lightning strike. On the other hand, there may be also switching impulse voltage caused by unforeseen switching pulses in the controlled network.

In case of insufficient resistance switch of load steps in relation to the pulse voltage in the load branch not conducting the load current, can occur speed intermittent short circuit or undesirable breakdown of ceramics or steam protective screen vacuum switches that not only can cause permanent damage, but, in General, is undesirable.

In many cases, in the calculation of discontinuous intervals, and thus, in particular, and vacuum switches, this leads to an increase of their size, they are guaranteed to be able to withstand the load voltage. Increasing the size is a disadvantage as due to the small installation space, which now have modern instruments, and because of the economy and the availability of such vacuum switches.

From DE 2357209 A and DE 2604334 already know that to combat excessive loads tension load between the branches should provide a protective spark gaps, or varistors, or something, � other; however, these tools in different cases are insufficient and cannot be deleted or not completely prevent the harmful action of loads the voltage pulse.

Therefore, object of the invention is to prevent increase in the size of the vacuum switches and at the same time to provide a switch of load steps according to the invention the necessary dielectric (breakdown) strength.

This task is solved through the switch of load steps with signs of the first paragraph of the claims. The dependent claims relate to preferred improved embodiments of the invention.

The General inventive idea is to offset describes the load voltage vacuum switches on contact device installed in series with them. After a successful shutdown or switch - depending on the scheme - with the help of vacuum switches additional contact device according to the invention immediately after that provide through the no-current switching full isolation on potential. Before the next switching of the load, i.e., before the vacuum switches in reverse order through the contact device according to the invention first is on again�connections to potential.

Contact device according to the invention can be in the form of mechanical contacts directly in insulating oil, they can also be implemented in the form of additional vacuum switches or performed by semiconductor technology.

Below the invention is illustrated in more detail in the exemplary embodiments shown in the drawings, which show:

Fig. 1 - scheme of the first switch of load steps according to the invention,

Fig. 2 - the process of switching,

Fig. 3 is a diagram of another switch of load steps according to the invention.

Fig. 1 shows a switch of load steps, load switch which seamless switches between two branches And, In the winding. In the middle shows the electrical circuit conducting steady state load current. It contains the first vacuum switching element MSV and connected in series with it mechanical contact MTF, depending on the switch can connect each of the two branches A or b with the first vacuum switching element MSV. Left and right of it shows both the auxiliary circuit, performing a seamless switching of the load current; they are made with the possibility of including for a short time when switching from�ellenemi and outlet LA load and short time loop current. They consist, respectively, of an additional vacuum switch TTVAor TTVVand connected in series with them intermediate resistor R.

According to the invention between the connected branches A, b and vacuum switches TTVATTVBthe auxiliary current circuits in series with them included respectively contact SCVAor respectively SCVBthat in a stationary mode as a no-current auxiliary changeover contacts fully electrically disconnects the vacuum switches TTVAor TTVVand performs isolation on potential.

Thus, a simple and effective way to provide reliable protection of these vacuum switches from overvoltage such as surge voltage.

Fig. 2 shows the sequence of action of the load switch according to the invention. It is shown that the SCV contactsAand SCVVprior to the switch install the necessary galvanic connection of the vacuum switches TTVAand TTVVin a corresponding conductive auxiliary branches, and after switching again provide isolation capability in another subsidiary branches.

Fig. 3 shows a modified embodiment of the stipulated�the invention switch load switch load steps. With no mechanical contacts SCVAand SCVVaccording to the invention is made not as a separate people, and as a relay with changeover contact. Such an arrangement provides a preferred actuation of these contacts, their operation and effect changes nothing.

It should be mentioned that the function of contacts serially connected according to the invention in auxiliary electrical circuit with each vacuum switch, designated in the examples of execution as SCVAor SCVVnot tied to a particular scheme or a number of vacuum switches. In the framework of the invention are possible and recommended many other schemes.

1. Switch of load steps for a seamless switching of the winding branches of a stepped transformer that contains
a selector to select without consuming power of the new winding branches that you want to switch,
and a load switch for the seamless switching of the load
wherein the load switch comprises at least one main branch of the circuit, which in the stationary regime is conducting a load current from winding connected to the branch before discharge of the load at least one vacuum switch, and
moreover, the load switch further contains at IU�Isha least two auxiliary circuit, which, respectively, represent the successive inclusion of additional vacuum switch and at least one intermediate resistor and installed, respectively, between one of the winding branches and allotment of the load
wherein
that, in addition to contacts of the selector, each of the at least two auxiliary branches of the current in the load switch between the corresponding branch (A, b) winding and the corresponding additional vacuum switch (TTVATTVIn) sequentially installed driven separately additional contact (SCVA, SCVB).

2. Switch of load steps according to claim 1, characterized in that
additional contacts (SCVA, SCVBmade in the form of mechanical contacts in the oil.

3. Switch of load steps according to claim 1 or 2, characterized in that
additional contacts (SCVA, SCVBmade in the form of a relay with changeover contacts.

4. Switch of load steps according to claim 1, characterized in that
additional contacts (SCVA, SCVBmade in the form of additional vacuum switches.

5. Switch of load steps according to claim 1, characterized in that
additional contacts (SCVA, SCVBmade in the form of semiconductor �Hemi or semiconductor circuits.



 

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