EP0978131B1 - Circuit arrangement for a load transfer switch - Google Patents

Abstract

The invention concerns a circuit for a load transfer switch comprising a regulating winding with a regulating stage (1) whose load current can be conducted via a lower or a higher winding tap (2, 3) and via at least two selector contacts (4, 5) and two permanent contacts (6, 7) with a common terminal lead (8). Switching from the lower to the higher winding tap or vice versa occurs via a first load transfer switch (9), wherein contact (10) is located in the connection of the selector contact (4) to the permanent contact (6) and the contact (11) is placed in the connection of the selector contact (5) to the permanent contact (7). The root contact of the first load transfer switch is connected via a transition resistor (13) and a bridging switch (14) in series to the common terminal lead (8). A second load transfer switch (15) is provided, wherein contact (16) is once again connected to the connection of the selector contact (4) to the permanent contact (6) and contact (17) is connected to the connection of selector contact (5) to permanent contact (7). The root contact (18) of said second load transfer switch (15) is connected to the connection of the transition resistor (13) and the bridging switch (14) by means of a thyristor circuit (19). The thyristor circuit (19) has antiparallel-connected thyristors.

Description

The invention relates to a method for a diverter switch of a tap changer for uninterrupted switching of the control winding of a transformer, whereby the load current via a lower or higher winding tap of a control stage a control winding and via a connection of at least two selector contacts and two permanent contacts with a common lead and for the Switching from the lower to the higher winding tapping or vice versa first and a second changeover switch are provided, each one of the two Contacts of each switch to connect a selector contact with one Permanent contact is established and the root contact of this first switch via one Overvoltage resistance and a bypass switch in series with the common derivative is connected and the root contact of this second Switch over a semiconductor circuit to the connection of Overvoltage resistance and bypass switch is placed, being used for switching the control winding the thyristors of the thyristor circuit before closing the Bypass switch and before opening a permanent contact, after the switching movement of the bypass switch and the permanent contact of the Thyristor circuit is extinguished or blocked, that the switch from one contact to the other contact is switched without power after that Switching the thyristor circuit is ignited again, then the switching movement of the other permanent contact and the opening of the bypass switch takes place after the Switching movement of the bypass switch and the permanent contact of the Thyristor circuit is deleted or locked again.

From FR-A-1 413 424 is a circuit arrangement and a method of the beginning described type known, using a controlled semiconductor converter finds. A disadvantage of this method is that the semiconductor circuit is always on There is tension. In addition, it is in this known method with the known circuit disadvantage that the root switch in the first algorithm is switched on when there is a voltage state. This is what happens a shutdown. The main contact also switches on when the Voltage drop of the resistor is also present at the main contact to be switched on. This also results in a switch-on burn-up.

Furthermore, EP 0 375 687 B2 describes a circuit arrangement in one Load switch known, which has a thyristor circuit. With this arrangement goes the load current briefly on a relief circuit that between the Root connection of this first switch and the common derivative arranged is. This relief circuit also has a thyristor circuit with anti-parallel connection Thyristors on. In addition, the relief circuit has a second switch on, which is in series with the thyristor circuit. From this second switch is the one changeover contact directly and the other changeover contact via the Overvoltage resistance connected to the root contact of the first switch.

A disadvantage of this circuit arrangement is that the contact erosion only when Switching off is avoided. Step when switching on the permanent contacts Contact bruises, which leads to brief arcing. This Arcing causes the contacts to burn and thus occurs a soot on the oil. It must therefore be used to ensure flawless Operating contacts and oil are changed after a certain number of operations, so that it due to the shutdown of the transformer Business interruptions come.

With the diverter switch according to the cited EP-PS, this is via the load switch shaft controlled movement in one direction only. Most However, tap changer types use diverter switches whose movement sequence from the Diverter switch shaft has a reciprocating movement. This is a additional mechanical motion converter necessary.

The object of the invention is a method in a diverter switch a tap changer for uninterrupted switching of the control winding To create transformers of the type mentioned, which have the disadvantages of known arrangements avoids and the life of the diverter switch elevated.

The object is achieved by the invention. The method according to the invention is characterized in that for the erosion-free opening and closing of the Permanent contacts, the changeover switch and the bypass switch Semiconductor circuit consisting of antiparallel connected thyristors Thyristor circuit has and that with a back and forth movement, the Switch position of the first switch either at the end of the switching process for the outgoing movement and at the beginning of the switching process for the outgoing Movement or at the beginning of the switching process for both movement sequences that are derived from the diverter switch shaft, is changed without current, so that by this switch position of the switch at the end of the switching process both Connections of the thyristor circuit are at the same potential.

With the invention it is possible for the first time, on the one hand, through the thyristor circuit Burn-free opening and closing of the permanent contacts, the changeover switch and the To ensure bypass switch and on the other hand by the switch positions against the thyristor circuit at the beginning and at the end of the switching process Protect surges. Especially with regard to both Movements that are derived from the diverter switch shaft. Through this Both switch positions are at the end of the switching process Connections of the thyristor circuit at the same potential.

Furthermore, the invention makes it possible to perform both movements without additional ones Realizing components. This invention also reduces the component expense to a to achieve arc-free switching from one control stage to another, not increased. In addition, the contact erosion, both when switching on as well prevented when switching off the permanent contacts.

The invention is a largely maintenance-free diverter switch for Step switch given.

On the basis of the usual switch-over time, those in the known Diverter switch used mechanical switching elements as well Overvoltage resistors are used. Even just an ignition device for that Thyristors are required.

The invention is based on exemplary embodiments shown in the drawing are explained in more detail. 1 shows the circuit arrangement in one Diverter switch and FIGS. 2, 3 and 4 the associated flow diagrams.

Fig. 1 shows a control stage 1 of a control winding, the load current over a lower or higher winding tapping 2, 3 and at least two Selector contacts 4, 5 and two permanent contacts 6, 7 of a common derivative 8 is feedable. Switching from the lower to the higher winding tap or vice versa via a first changeover switch 9. This changeover switch 9 has two Contacts 10, 11 for switching and a root contact 12. The contact 10 of the switch 9 is on the connection of the selector contact 4 with the permanent contact 6 and the contact 11 is on the connection of the selector contact 5 with the Permanent contact 7 placed. The root contact 12 of the first switch 9 is via a Overvoltage resistor 13 and a bypass switch 14 in series with the common derivative 8 connected. There is also a second changeover switch 15 provided the two contacts 16, 17 for switching and a root contact 18 has. The contact 16 of this switch 15 is again with the connection of the Selector contact 4 with the permanent contact 6 and the contact 17 is with the connection the selector contact 5 connected to the permanent contact 7. The root contact 18 this second switch 15 is connected via a thyristor circuit 19 to the connection of Overvoltage resistor 13 and bypass switch 14 placed. The thyristor circle 19 has anti-parallel connected thyristors.

According to FIG. 2, the changeover from a Step tap to another step tap of control level 1 one Control winding described in steps. The left-hand labels in Fig. 2 correspond to the switches or thyristors and contacts in FIG. 1.

Ausgangszustand: Dauerkontakt 6 geschlossen, Dauerkontakt 7 offen,

Endzustand: Dauerkontakt 6 offen, Dauerkontakt 7 geschlossen.

The following switching is described below:

Initial state: permanent contact 6 closed, permanent contact 7 open,

Final state: permanent contact 6 open, permanent contact 7 closed.

Intervals:

A:

Selector contacts 4, 5 and permanent contact 6 closed;

Permanent contact 7 and bypass switch 14 open;

Thyristors 19 not fired;

Switch 15 connects contact 16 with root contact 18;

Switch 9 connects contact 10 with root contact 12;

Load current flows through winding tapping 2 and via selector 4 and

Permanent contact 6 for common derivation 8;

B:

the thyristors of the thyrister circuit 19 are ignited;

C:

the bridging contact 14 is closed without burning (parallel to this Bridging contact 14 is the protective circuit: fired thyristor circuit 19, Contact 16 with root contact 18 closed, closed permanent contact 6 given)

D:

the permanent contact 6 opens without burning (parallel to this permanent contact 6 is the protection circuit: fired thyristor circuit 19, contact 16 with root contact 18 closed, closed bypass contact 14 given); Load current flows through changeover switch 15, thyristor circuit 19 and Bypass switch 14;

E:

Thyristor circuit 19 is no longer ignited and only leads the load current up to to the next zero crossing; then the load current flows through changeover switch 9, Overvoltage resistor 13 and bypass switch 14;

F:

Changeover switch 15 switches from contact 16 to contact 17 without current;

G:

Thyristor circuit 19 is ignited; this creates a compensating current across the Selector contact 4, changeover switch 9, transition resistor 13, thyristor circuit 19, Switch 15 for selector contact 5 flows;

H: Permanent contact 7 is closed without burning (parallel to this permanent contact 7 is the protective circuit: fired thyristor circuit 19, contact 17 with Root contact 18 closed, bridging contact 14 closed given); the circuit: thyristor circuit 19, changeover switch 15, permanent contact 7 and Bridging switch 14 has practically equivalent potential (the Voltage drop between any points in this circle is very small);

I:

Bridging switch 14 opens without burning (parallel to this Bridging contact 14 is the protective circuit: fired thyristor circuit 19, Contact 17 with root contact 18 closed, closed permanent contact 7 given); the load current flows through the permanent contact 7;

J:

Thyristor is no longer fired; and only leads the compensation current up to to the next zero crossing;

K:

the switch 9 changes the contact position from the contact 10 to the currentless Contact 11.

In the case of a movement sequence in one direction, the above sequence is analogous to next switchover from A to K repeated (initial state: permanent contact 7 closed, permanent contact 6 open, final state: permanent contact 7 open, permanent contact 6 closed).

Ausgangszustand: Dauerkontakt 7 geschlossen, Dauerkontakt 6 offen,

Endzustand: Dauerkontakt 7 offen, Dauerkontakt 6 geschlossen.

K:

Wählerkontakte 4, 5 und Dauerkontakt 7 geschlossen;

Dauerkontakt 6 und Überbrückungsschalter 14 offen;

Thyristoren 19 nicht gezündet;

Umschalter 15 verbindet Kontakt 17 mit Wurzelkontakt 18;

Umschalter 9 verbindet Kontakt 11 mit Wurzelkontakt 12;

Laststrom fließt über Wicklungsanzapfung 3 sowie über Wähler- 5 und

Dauerkontakt 7 zur gemeinsamen Ableitung 8;

J:

Umschalter 9 ändert stromlos seine Schaltstellung vom Kontakt 11 auf den Kontakt 10;

I:

die Thyristoren des Thyristerkreises 19 sind gezündet; dadurch entsteht ein Ausgleichstrom der über Wählerkontakt 4, Umschalter 9, Überschaltwiderstand 13, Thyristorkreis 19, Umschalter 15 zum Wählerkontakt 5 fließt; der Spannungsabfall am offenen Überbrückungskontakt 14 ist sehr klein;

H:

der Überbrückungskontakt 14 wird abbrandfrei geschlossen (parallel zu diesem Überbrückungskontakt 14 ist der Schutzkreis: gezündeter Thyristorkreis 19, Kontakt 17 mit Wurzelkontakt 18 geschlossen, geschlossener Dauerkontakt 7 gegeben); der Kreis: Thyristorkreis 19, Umschalter 15, Dauerkontakt 7 und Überbrückungsschalter 14 hat praktisch äquivalentes Potential (der Spannungsabfall zwischen beliebigen Punkten in diesem Kreis ist sehr klein);

G:

der Dauerkontakt 7 öffnet abbrandfrei (parallel zu diesem Dauerkontakt 7 ist der Schutzkreis: gezündeter Thyristorkreis 19, Kontakt 17 mit Wurzelkontakt 18 geschlossen, geschlossener Überbrückungskontakt 14 gegeben); Laststrom fließt über Umschalter 15, Thyristorkreis 19 und Überbrückungsschalter 14;

F:

Thyristorkreis 19 wird nicht mehr gezündet; und führt den Strom nur bis zum nächsten Nulldurchgang; Laststrom fließt über Wählerkontakt 4, Umschalter 9, Überschaltwiderstand 13 und Überbrückungsschalter 14;

E:

Umschalter 15 ändert stromlos seine Schaltstellung von Kontakt 17 auf Kontakt 16;

D:

Thyristorkreis 19 wird gezündet und übernimmt den Laststrom; der Spannungsabfall am offenen Dauerkontakt 6 ist sehr klein;

C:

Dauerkontakt 6 wird abbrandfrei geschlossen (parallel zu diesem Dauerkontakt 6 ist der Schutzkreis: gezündeter Thyristorkreis 19, Kontakt 16 mit Wurzelkontakt 18 geschlossen, geschlossener Überbrückungskontakt 14 gegeben);

B:

der Überbrückungsschalter 14 öffnet abbrandfrei (parallel zu diesem Überbrückungskontakt 14 ist der Schutzkreis: gezündeter Thyristorkreis 19, Kontakt 17 mit Wurzelkontakt 18 geschlossen, geschlossener Dauerkontakt 7 gegeben);

A:

der Thyristorkreis wird nicht mehr gezündet;

In the case of a to-and-fro motion sequence, the sequence from K to A is run through the next switchover. The following switching is described below:

Initial state: permanent contact 7 closed, permanent contact 6 open,

Final state: permanent contact 7 open, permanent contact 6 closed.

K:

Selector contacts 4, 5 and permanent contact 7 closed;

Permanent contact 6 and bypass switch 14 open;

Thyristors 19 not fired;

Switch 15 connects contact 17 with root contact 18;

Switch 9 connects contact 11 with root contact 12;

Load current flows via winding tapping 3 and via selector 5 and

Permanent contact 7 for common derivation 8;

J:

Switch 9 changes its current position from contact 11 to contact 10 without current;

I:

the thyristors of the thyrister circuit 19 are ignited; this creates a compensating current which flows via selector contact 4, changeover switch 9, contact resistor 13, thyristor circuit 19, changeover switch 15 to selector contact 5; the voltage drop at the open bypass contact 14 is very small;

H:

the bridging contact 14 is closed without burning (the protective circuit is parallel to this bridging contact 14: fired thyristor circuit 19, contact 17 closed with root contact 18, closed permanent contact 7 given); the circuit: thyristor circuit 19, changeover switch 15, permanent contact 7 and bypass switch 14 has practically equivalent potential (the voltage drop between any points in this circuit is very small);

G:

the permanent contact 7 opens without erosion (the protective circuit is parallel to this permanent contact 7: fired thyristor circuit 19, contact 17 closed with root contact 18, closed bypass contact 14 given); Load current flows through changeover switch 15, thyristor circuit 19 and bypass switch 14;

F:

Thyristor circuit 19 is no longer ignited; and only leads the current to the next zero crossing; Load current flows through selector contact 4, changeover switch 9, transition resistor 13 and bypass switch 14;

E:

Switch 15 changes its current position from contact 17 to contact 16 without current;

D:

Thyristor circuit 19 is ignited and takes over the load current; the voltage drop at the open permanent contact 6 is very small;

C:

Permanent contact 6 is closed without erosion (parallel to this permanent contact 6 is the protective circuit: fired thyristor circuit 19, contact 16 closed with root contact 18, closed bypass contact 14 given);

B:

the bypass switch 14 opens without burning (the protective circuit is parallel to this bypass contact 14: fired thyristor circuit 19, contact 17 closed with root contact 18, closed permanent contact 7 given);

A:

the thyristor circuit is no longer ignited;

If a to-and-fro movement is specified by the load switch shaft and steps A to K are carried out, the changeover switch 9 changes its state at the end of the changeover process. When the steps follow
K to A, the changeover switch 9 changes its state at the beginning of the changeover process. The current flows in the load switch are not changed either by the change in state of the changeover switch 9 at the beginning or at the end of the changeover process.

According to FIG. 3, the changeover from a Step tap to another step tap of control level 1 one Control winding described in steps. The left-hand labels in Fig. 3 correspond to the switches or thyristors and contacts in FIG. 1.

The difference to the processes shown above is that the switch 9 changes its switch position only at the end of the switching process for both movement sequences, that is to say both for specifying the movement in one direction and for a reciprocating movement by the diverter switch shaft is derived. Each changeover process in the diverter switch corresponds to the sequence A to K according to FIG.
According to FIG. 4, the changeover from one tap to another tap of control stage 1 of a control winding is described in steps by means of a flow chart. The left-hand designations in FIG. 4 correspond to the switches or thyristors and contacts in FIG. 1.

The difference to the processes shown above is that the Switch 9 changes its switch position only at the beginning of the switching process and for both movement sequences, i.e. both for the specification of the movement in one Direction as well as for a reciprocating movement by the Diverter switch shaft is derived. Every switching process in the diverter switch is analogously to the sequence K to A according to FIG. 2.

As shown above, both turn on and turn off the Permanent contacts 6 or 7 burn-free, as the protective circuit is always at the time of switching: Bridging switch 14 closed, thyristor circuit 19 ignited, changeover switch 15 closed accordingly, is given. The opening and closing of the Bypass switch 14 burn-free, since at the time of switching the protection circuit: ignited thyristor circuit 19, correspondingly closed switch 15, and Correspondingly closed permanent contact 6 or 7 is given. Switching the Switches 9 and 15 are de-energized since the thyristor circuit 19 is at this time is not ignited and is conductive. The contact erosion is both when switching on as also prevented when all contacts are switched off.

Reference list

1

Control level

2nd

Winding tapping

3rd

Winding tapping

4th

Voter contact

5

Voter contact

6

Permanent contact

7

Permanent contact

8th

Derivative

9

switch

10th

Contact

11

Contact

12th

Root contact

13

Overvoltage resistance

14

Bypass switch

15

Contact

16

Contact

17th

Contact

18th

Root contact

19th

Thyristor circuit

Claims (1)

1. Method for an on-load tap changer for a multiple-contact switch for uninterrupted inversion of the control coil of a transformer, whereby the on-load current runs via a lower or higher coil tap (2, 3) of a control level (1) of a control coil and via a connection with at least two selector contacts (4, 5) and two steady contacts (6, 7) with a mutual discharge (8), and for switching from the lower to the higher coil tap (2, 3) or vice-versa a first and a second tap changer (9 resp. 15) are provided, whereby one of the two contacts (10, 11 resp. 16, 17) of each tap changer (9, 15) is applied to the connection between a selector contact (4, 5) and a steady contact (6, 7) and the root contact (12) of this first tap changer (9) is connected to the mutual discharge (8) via a transition resistor (13) and a shorting switch (14) arranged in series, and the root contact (18) of this second tap changer (15) is applied to the connection between the transition resistor (13) and the shorting switch (14) via a semiconductor circuit, whereby to tap change the control coil the thyristors of the thyristor circuit (19) are fired before the shorting switch (14) is closed and before a steady contact (6 resp. 7) is opened, the thyristor circuit (19) is extinguished or blocked after switching of the shorting switch (14) and the steady contact (6 resp. 7), so that subsequently the tap changer (15) is switched from one contact (16 resp. 17) to the other (17 resp. 16) without current, so that after this tap change the thyristor circuit (19) is fired again, followed by switching of the other steady contact (7 resp. 6) and opening of the shorting switch (14), after switching of the shorting switch (14) and the steady contact (6 resp. 7) the thyristor circuit (19) is extinguished or blocked again, characterised by the fact that for erosion-free opening and closing of the steady contacts (6, 7) the tap changer (9, 15) and the shorting switch (14) of the semiconductor circuit has a thyristor circuit (19) consisting of thyristors switched so as to be anti-parallel, and that when switching back and forth the switch position of the first tap changer (9) is changed without current either at the end of the first switching process for switching in one direction and at the beginning of the switching process for switching in the other direction, or at the beginning of the switching process for switching in both directions, which are derived from the on-load tap changer shaft, so that with this switch position of the tap changer (9) both connections of the thyristor circuit (19) have the same potential at the end of the switching process.

Images