DE2209500A1 - CIRCUIT ARRANGEMENT FOR UNINTERRUPTED LOAD SWITCHING IN STEPPED TRANSFORMERS - Google Patents

Description

TRANSFORMATOREN UNION AKTIENGESELLSCHAFT 7 Stuttgart-Bad Cannstatt, Deckerstr. 5

Erf.Nr. TU / PN 71/005

Kollrodt / ma. February 22, 1972

Circuit arrangement for interruption! Οsen load switching with step transformers.

The invention relates to a circuit arrangement for uninterrupted load switching in step transformers with two main vacuum switching elements, each one in series with a transition resistor lying auxiliary vacuum switches are connected in parallel, the outputs of all vacuum switches alternating via a changeover switch according to a predetermined program are verounden with a derivative.

The transformation ratios of step transformers are in operation without interrupting the load current adapted to the respective load conditions. In addition so-called diverter switches are used. By the German

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Offenlegungsschrift 1 901 105 is for diverter switches of tap changers a circuit with four vacuum switching elements has become known, which have a tap changer also with overcurrents or decomposition of the oil surrounding the tap changer is avoided, so that operation is largely maintenance-free is possible, furthermore with weight-wise small transition resistances due to the realizable timed switching sequence can be worked. In the known switching arrangement is for current and tension relief of the vacuum holding elements A diverter is provided in the basic position, which switches without power. The disadvantage of this arrangement is, however, that defects in the main vacuum switching elements are not detected when the diverter switch is in operation and can lead to incorrect switching.

The invention is therefore based on the object of providing a circuit arrangement for diverter switches of step transformers with a greater internal security than the known circuit arrangements and to keep the effort required for this as low as possible.

According to the invention, this object is achieved by that each main vacuum holding element is normally one actuated in the de-energized state, but also designed to switch the rated current of the circuit arrangement On-off switch is connected upstream, according to the specified switching program shortly before closing of the main vacuum switching element assigned to it

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closes and shortly after opening this main vacuum switching element opens.

The invention is very advantageous -.veil the on-off switch are designed so that if a main vacuum switching element fails in rated operation, the load current, take over, so that despite the failure of the main vacuum holding element emergency operation can initially be maintained without interrupting operations. The during this Gases developed in emergency mode during switching and / or the luminous inclination of the arc serve as a fault indicator. Any necessary network shifts can also be carried out during this emergency operation so that there is no interruption in the supply of electrical energy to the consumer.

According to an advantageous development of the invention it is provided that the outputs of the vacuum switching elements directly with the derivation to the network and the movable Contact of a simple changeover switch are connected, which is the closed main vacuum switching element in the basic position short-circuits and its contacts are all open during a switchover. This switch has a simpler structure than the changeover switch required for the already known circuit arrangement. This simplification is possible because the main vacuum switching elements are de-energized by the on-off switch. Relief of tension in the in A series of auxiliary vacuum closing elements with a resistor is not absolutely necessary, because after a possible breakdown of the opened contact path as a result of an overvoltage in the step transformer, the current is limited by the resistor and

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Experience has shown that it goes out by itself in the next current zero crossing.

According to another advantageous embodiment of the invention it is provided that the main vacuum holding elements upstream on-off switch together with all vacuum switching elements of the circuit arrangement and remote changeover switch are mechanically driven by a common shaft.

The invention is explained in more detail with the aid of two exemplary embodiments in a drawing.

Fig. 1 shows a circuit arrangement according to the invention with a hitherto customary changeover switch.

Fig. 2 shows a circuit arrangement with a simplified Toggle switch.

Selector arms W. and W ₂ are at positions η and n + 1 of a step winding U. a transformer not shown in detail. The Wählerarm W.-OFF switch S is connected via a ₁ to a main vacuum switch element ₁₁ and V through a resistor r .. with an auxiliary vacuum switching element V _12th The outputs of the main vacuum holding element V ₁₁ and the auxiliary vacuum switching element V ₁ ^ are routed via a common line to a fixed contact 10 of a changeover switch Uq. In parallel with this, a fixed contact 1 des.Umschalters U _{Q is} connected to de.n selector arm W ₁ via a connecting line L ₁ . Analogous to this, the selector arm W _{2 is} via an on-off switch Sp and a main vacuum switching element V ₂₁ as well

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r via a resistor ₂ and an auxiliary vacuum switching element _{V? 2} ^m it a fixed contact 20 of the changeover switch connected Uq. In addition, a direct connection line L _{2 is also led} from the selector arm W ₂ to a fixed contact 2 of the changeover switch Uq. The current flows from the oewegiichen contact of the changeover switch Uq into the network via a derivative I _T.

In Fig. 1, the basic position, in which the selector arm W. is live, is shown. A switchover of the load to the selector arm Wp is initiated by pivoting a _{bridge Br connected to the movable contact of the switch U Q} from the fixed contacts 1-10 to the fixed contacts 10-20. As a result, the connecting line L. has become de-energized and the current is routed via the element V ₁₁ . Now the main vacuum switching element V _{11 is} opened, shortly thereafter also the on-off switch S ₁ and the current from the series circuit from the resistor r. and the auxiliary vacuum holding element V ₁ P taken over. Now the auxiliary vacuum switch element V ₂₂ £ ^{esc is} closed ^and takes over half the load current from the selector arm Wp. In addition, while the intermediate position has now been reached, a compensating current flows from the selector arm Wp over the resistor r, the auxiliary vacuum holding element V ₂₂ , the fixed contact 20, the bridge Br, the fixed contact 10, the auxiliary vacuum switching element V ₁₂ and the resistor r .. to the selector arm W ..

The auxiliary vacuum switching element V ₁₂ is opened and shortly thereafter the on-off switch S ₂ and then the main vacuum switching element Vp _{1 is} closed, so that the load current is now via the on-off switch S ₂ and

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_ ₆ _ 220S500

the main vacuum switching element Vp _{1 flows} to the fixed contact 20 of the switch U _Q. Finally, by pivoting the bridge Br further to the fixed contact 2, the two last-mentioned switches are short-circuited _{via the connecting line L 2.}

When switching the load current from the selector arm Wp on the voter arm Wv become the individual Switching elements actuated in reverse order, so that a simple, form-fitting transmission is used Can be found.

If one of the main vacuum holding elements V ₁₁ or Vp ₁ becomes faulty and no longer interrupts the current, this interruption is carried out by the corresponding on-off switch S ₁ or Sp, so that the transformer is avoided. Since these on-off switches S ₁ and Sp are normal switches with contacts exposed in the oil, they will draw an arc when actuated under load. The light effect of these arcs or the resulting decomposition gases are used to indicate the fault on the relevant main vacuum switching element V ₁₁ or Vp ₁ . Since the on-off switches S ₁ and Sp are designed and arranged in such a way that they can switch the rated current, emergency operation is maintained for a certain time without interruption if one of the main vacuum switching elements fails. A fault in the auxiliary vacuum hold-up elements is noticeable through gases in the resistors r or through gas formation on the changeover contact clocks 10 or.

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In the circuit arrangement according to FIG. 2, the changeover switch Uq is replaced by a changeover switch U with fixed contacts 1 and 2. In this arrangement, the outputs of the two main vacuum holding elements V ₁₁ and Vp ₁ and the auxiliary vacuum switching elements V ₁ ρ and Vpo are with each other and with the. Derivative Ij. tied together. As a result, the changeover switch U can be much simpler than the changeover switch U _Q with its four fixed contacts.

To initiate the changeover in this arrangement, the movable contact of the changeover switch U, which is also connected to the lead I, is brought into the central position shown in dashed lines. After that, the switching proceeds as in the arrangement according to Fig. 1. Finally, the series connection of the on-off switch S ₂ and the main vacuum _{switching contact Vp 1} is short-circuited by applying the movable contact from the changeover switch U to the fixed contact 2, whereby the vacuum element is in the basic position is relieved in terms of current. Here, too, the on-off switches S ₁ and S ₂ indicate defects in the main vacuum switching elements V ₁₁ and V _{21 due} to arcs that may occur on them.

Step currents possibly triggered by flashovers over the opened contacts of the respectively opened auxiliary vacuum switching element V ₂ or Vp ₂ are determined in their magnitude by the resistors r .. or r _? limited and extinguish at the next current zero crossing.

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Claims (2)

TRANSFORMATOREN UNION AKTIENGESELLSCHAFT 7 Stuttgart-Bad Cannstatt, Deckerstr. 5 Erf.Nr. TU / FN 71/008 Kollrodt / ma. February 22, 1972 Claims ( 1. ) Circuit arrangement for uninterrupted load switching in step transformers with two main 'vacuum switching elements, both of which are connected in parallel to an auxiliary vacuum switching element in series with a transition resistor, with the outputs of all vacuum maintenance elements alternating with a derivative via a changeover switch according to a specified program are connected, characterized in that each main vacuum holding element (V ₁₁ , Vp _{1 ) is preceded by an on-off switch (S 1} , S ₂ ) which is normally operated in the de-energized state, but is also designed to switch the rated current of the circuit arrangement, which according to the specified switching program closes shortly before the main vacuum switching element (V ₁₁ , V ₂₁ ) assigned to it closes and opens shortly after this main vacuum holding element (V ₁₁ , V ₁ ) is opened. 309836/0691 2. Circuit arrangement according to claim 1, characterized in that the outputs of the main vacuum switching elements (V ..., V ₂₁ ) and the Hi If s vacuum chal telemente (Vi? '^ 22 ^ directly with the derivation (I-) to the network and the movable contact of a simple changeover switch (U) are connected, which in the basic position _{short-circuits the respectively closed main vacuum switching element (V ... or Vp 1} ) and whose contacts are all open during a changeover. Circuit arrangement according to Claim 1 or 2, characterized in that the on-off switches (S ₁ , S _{2 ) connected upstream of the main vacuum holding elements (V 11} , V ₂₁ ) together with all vacuum switching elements of the circuit arrangement and the changeover switch (U ₀ or U) are driven by a common shaft. 309836/0691