JPS6115569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for replacing a tap-to-tap overvoltage protection element in a switching switch of an on-load tap switching device using a vacuum switch as a current switching element with a current switching element for tap switching. This relates to the circuit system of a switching switch.

FIG. 1 shows an example of a switching switch of a conventional on-load tap switching device. In the figure, 1 is a spark gap, R ₁ and R ₂ are resistors for limiting the bridging current that circulates between adjacent taps when switching taps, and 2 and 3 are adjacent taps such as a transformer. They are respectively connected to a pair of input terminals 5 and 6 of a switching switch via tap selectors (not shown). Reference numeral 4 designates an output terminal of the switching switch, which constitutes the neutral point of the transformer in the case of a load tap switching device connected to the neutral point of a star-connected transformer. A and B are main arc contacts connected in series to the input terminals 5 and 6 and the output terminal 4 of the switching switch, respectively, C and D are connected at one end to the resistors R ₁ and R ₂ , respectively, This is a resistance contact whose other end is connected to the output terminal 4.

Since the tap switching operation of the above circuit is already widely known, the explanation thereof will be omitted.

In the conventional circuit shown in FIG. 1, the load current of a transformer or the like is supplied through the main arc contact A in the state shown in the figure. In this circuit, if there is no spark gap 1, and an external current enters from the line end of a transformer or the output terminal 4 of a switching switch, and a discharge occurs at main arc contact B, which is currently open, tap 2 , 3, which can result in a very serious accident as is well known. As a countermeasure, conventionally, as shown in Fig. 1, terminals of resistors R ₁ and R ₂ other than those connected to input terminals 5 and 6, respectively, were connected to each other with a spark gap 1.
The discharge starting voltage of this spark gap is selected to be the lowest compared to the other inter-tap insulation structure parts of the switching switch, and the spark gap is first adjusted so that the discharge is changed between the gaps. Even if a discharge occurs, the short-circuit current between the taps is limited by resistors _R1 and _R2 , and the following current is cut off by the spark gap.
Changeover switches have prevented short circuits between taps due to the intrusion of external power surges, or dielectric breakdown in other solid insulation parts.

In the switching switch of the conventional on-load tap switching device as shown in Fig. 1, A, B, and C in the figure are
and D, etc., have been used as current switching elements such as oil-submerged contacts or air-borne magnetic blow-off contacts. However, recently, vacuum switches have begun to be used as these current switching elements. Even in on-load tap switching equipment using such a vacuum switch, there is a possibility that a short circuit between the taps may occur due to an external power surge that enters the switching switch, as in conventional switching switches. protection is needed.

As a countermeasure against this, by taking advantage of the extremely high shearing capacity of vacuum switches, for example, use a vacuum switch with a rated shearing capacity equal to or higher than the tap-to-tap short circuit capacity at the A and B contacts in Figure 1. It was proposed in Japanese Patent Publication No. 47-41686 with experimental results that even if a discharge occurs at the A or B contact due to an external electrical surge, the short-circuit current between the taps that continues to flow can be cut off at the first zero point. has been done.

However, this proposal is only effective for small capacity transformers with low tap-to-tap short circuit capacity.
Normally, in large capacity transformers in the 100MVA to 1000MVA class, the tap-to-tap short circuit capacity can be several tens to 100 times the rated tap-to-tap capacity.
The short circuit current value reaches several tens of KA or even 100 KA. Therefore, in an on-load tap switching device applied to a large-capacity transformer such as the one described above, the method proposed above is not practical because the short-circuit capacity between taps is large. As a second proposal, if there is a certain gap between the electrodes, as in the first proposal above, the vacuum switch can maintain a follow-on current nearly 20 times the rated current even when the electrodes are stationary. It has been proposed to insert a vacuum gap in place of the spark gap shown in Figure 1, taking advantage of its ability to break at the zero point (see Japanese Patent Laid-Open No. 52-96315). , has the advantages as described in that specification.

It is of course possible to use the second proposal above as a switching switch for an on-load tap switching device that uses a vacuum switch as a current switching element, but it is also possible to use a vacuum switch that already has follow-on and disconnection capabilities for tap switching. Because it is used as a current switching element for
It would be economical if this vacuum switch could also be used as a vacuum gap for overvoltage protection.

This invention is a switching switch for a load tap switching device that is used as a current switching element for switching the taps of a vacuum switch. This paper proposes a circuit system.

FIG. 2 shows a connection diagram for explaining the first principle for constructing this invention, and FIG. 3 shows a connection diagram for explaining the second principle for constructing this invention. In FIGS. 2 and 3, parts given the same reference numerals as in FIG. 1 indicate the same or equivalent parts as in FIG. 1. In the figure, a ₁ and a ₂ are a pair of fixed contacts connected to the line ends led out from both ends of the vacuum switch, and a can engage with a ₁ and a ₂ alone or bridge both fixed contacts. This is a bridging movable arm configured as follows.

FIG. 4 is an explanatory diagram of the means necessary to construct the present invention. h ₁ and h ₂ are a pair of fixed contacts connected to input terminals 5 and 6 of the switching switch, respectively;
h is a switching movable arm configured to engage only with either h ₁ or h ₂ . Also, A indicates a vacuum switch that functions as the main arc contact of the switching switch.

These vacuum switches are opened and closed by a drive device (not shown) in the order described below. In the figure, a vacuum switch with diagonal lines indicates a closed state, and a vacuum switch without diagonal lines indicates an open state. This display method is common to all figures in this specification. Vacuum switches C and D are constructed to discharge at the lowest voltage among the various insulated parts of the switching switch to which the tap-to-tap voltage is applied. Since the withstand voltage of a vacuum switch is determined by the distance between its electrodes, coordination with other insulating parts regarding discharge starting voltage can be adjusted relatively easily.

The first principle of this invention will be explained with reference to FIG. In FIG. 2, the load current of a transformer or the like is supplied from a tap 2 through a main arc contact vacuum switch A to an output terminal 4 of a switching switch to an external circuit (not shown). In this state, if an external power surge enters from the line end of a transformer (not shown) or the output terminal 4 of a switching switch, the external power surge voltage will be applied between the taps 2 and 3. When this voltage becomes higher than the withstand voltage of the vacuum switch C currently in operation, discharge begins and the electrodes of the vacuum switch C become electrically short-circuited. Due to the commercial frequency alternating voltage between the taps 2 and 3 and the external power surge voltage, a bridging current between the taps flows through the resistors R ₁ and R ₂ and the vacuum switch C. This current has a waveform similar to that shown in Figure 2 of the above-mentioned Japanese Patent Publication No. 47-41686, and usually has a waveform of several microseconds to several tens of microseconds between the external power surge current, the voltage value between the taps under normal conditions, and the resistance. A heavy commercial frequency alternating current determined by R ₁ and R ₂ flows. After that, only the latter current flows as a follow-on current. Since the values of R ₁ and R ₂ are normally selected so that this alternating current value is about the rated current of the transformer, it is similar to the experimental results described in Section 2 of the above-mentioned Japanese Patent Publication No. 47-41686. , the arc is easily extinguished at the first current zero point. In the circuit shown in FIG. 2, the operation when switching from tap 2 to tap 3 will be explained. In the state shown in FIG. 2, the load current of the transformer etc. is supplied from tap 2 as described above. To switch to tap 3, first the main arc contact vacuum switch A is opened and the load current is transferred to the electrical circuit consisting of resistor R ₁ - fixed contact a ₁ - bridging movable arm a - switching switch output terminal 4. Let it flow. Next, the vacuum switch C for the resistance contact is opened, and a circulating current between the taps begins to flow between the taps 2 and 3 via the resistor _R1 , the vacuum switch C, and the resistor _R2 . In addition, the load current is transmitted from taps 2 and 3 through resistor R ₁ , resistor R ₂ and vacuum switch C, respectively, according to the inverse ratio of the resistance values of resistors R ₁ and R ₂ , and then to fixed contact a _{1 .} and bridging movable arm a
is supplied to the output terminal 4 via. Subsequently, after the bridging movable arm a bridges the fixed contact _a1 and the fixed contact _a2 , it is inserted so as to engage only the fixed contact _a2 , as shown by the broken line in FIG. As a result of this operation, the load current supplied from tap 2 is
The load current that was being supplied from tap 3 now flows through resistor R ₁ , vacuum switch C, fixed contact a ₂ and bridging movable arm a, and now flows through resistor R ₂ ,
The flow begins to flow through the fixed contact _a2 and the bridging movable arm a. The bridging movable arm a operates without arcing because it simply bridges the vacuum switch C. Also, during this period, there is no change in the circuit for the inter-tap circulating current. Next, the vacuum switch C for resistance connection is opened to cut off the circulating current between the taps, and the load current to the tap 3.
Only from the resistor R ₂ - the fixed contact a ₂ - the bridging movable arm a is supplied. Next, the vacuum switch A for the main arc contact, which has already been opened and is in a non-current state, is reconnected by some method while remaining open at the position shown by the broken line in Fig. 2, and then the vacuum switch A is opened. Then, the load current can be supplied from the vacuum switch A to the external circuit of the transformer (not shown) via the output terminal 4, and the tap switching is completed.

In order to change the connection of the main arc contact vacuum switch A in the above-mentioned non-current state from tap 2 to tap 3, the means shown in FIG. 4 can be taken. That is, in FIG. 2, when the main arc contact vacuum switch A is opened and the load current has been completely transferred to the circuit including the resistor _R1 and the fixed contact _A1 , the switching movable arm h starts the switching operation, By the time the load current is conducted from tap 3 only through resistor R ₂ and fixed contact A ₂ , switch movable arm h has been applied to fixed contact H ₂ , and vacuum switch C has completely circulated current. The configuration may be such that the vacuum switch A is closed again after sufficient time has been allowed for the vacuum to be cut off.

Next, the second principle of the invention will be explained with reference to FIG. In FIG. 3, the load current of a transformer or the like is supplied from a tap 2 via a main arc contact vacuum switch A and an output terminal 4 to an external circuit such as a transformer (not shown). In this state,
If an external power surge enters from the line end of a transformer (not shown) or the output terminal 4 of a switching switch, the external power surge will be applied between the taps 2 and 3. If this external surge voltage becomes higher than the withstand voltage of the vacuum switch D currently in use,
Discharge begins and the electrodes of vacuum switch D become electrically short-circuited.

Due to the commercial frequency alternating voltage between the taps 2 and 3 and the external power surge voltage, a bridging current between the taps flows through the resistor _R2 and the vacuum switches D and A. The subsequent phenomenon is the same as the first principle,
The arc is extinguished at the first zero point of the alternating current, and serves as a protection against overvoltage. Next, the operation sequence when switching from tap 2 to tap 3 using the circuit shown in FIG. 3 will be explained. To switch to tap 3,
First, the main arc contact vacuum switch A is opened, commutating the load current to the electrical path consisting of the resistor R ₁ , the vacuum switch C, and the output terminal 4 of the switching switch.

Next, the vacuum switch D for the resistance contact is closed, and a circulating current between the taps begins to flow between the taps 2 and 3 via the resistor _R1 , the vacuum switch C, the vacuum switch D, and the resistor _R2 . Also, the load current is determined by the resistors R ₁ and R ₂
resistor _R1 and vacuum switch C from tap 2 and tap 3 in proportion to the inverse ratio of their respective resistance values.
and via resistor _R2 and vacuum switch D to output terminal 4. Next, the vacuum switch C is opened, cutting off the circulating current between the taps and supplying the load current from the tap 3 to an external circuit such as a transformer through only the resistor _R2 , the vacuum switch D, and the output terminal 4. Do it like this.

Next, the vacuum switch A for the main arc contact, which has already been opened and is in a non-current state, is reconnected by some method while it remains open at the position shown by the broken line in Figure 3, and the vacuum switch A is closed. Then, the load current will be supplied from the vacuum switch A via the output terminal 4, and the tap switching will be completed.

In order to change the connection of the vacuum switch A for the main arc contact in the above-mentioned no-current state from tap 2 to tap 3, the fourth principle, similar to the first principle shown in FIG.
The means shown in the figure may be used. The switching movable arm h shown _in FIG. By the time the current flows only through the circuit consisting of R ₂ and vacuum switch D, the fixed contact
It should be configured so that it is input into _h2 .

FIG. 5 shows an example of a switching switch of an actual on-load tap switching device constructed according to the above-mentioned first principle. Figures 6-1 show the tap switching order according to this embodiment. FIG. 7 is a sequence diagram representing the tap switching process from 1 to 1 in FIG. 6. Note that the solid line portion in FIG. 7 indicates the contact is closed. The overvoltage protection situation is the same as the explanation in FIG. 2. FIG. 8 shows another embodiment based on the above first principle. Figure 9 is the 8th
FIG. 6 is a diagram showing the operating order of each contact point according to the configuration shown in the figure.

Tap switching can be performed from tap 2 to tap 3 by advancing the sequence from left to right in this figure, and from tap 3 to tap 2 by advancing the sequence from right to left. The sequence indicated by the broken line in FIG. 9 is the order of operations when the sequence progresses from right to left in the figure. In the circuit shown in Fig. 8, if the main arc contact vacuum switch A commutates the load current to the resistor _R2 , by operating the movable switching contacts h and e at the opening and closing timing shown in Fig. 9. Even if it fails for some reason, the load current can be cut off because vacuum switches C and A are inserted in series in the load current circuit when the resistance contact vacuum switch C is subsequently opened. Another effect is that the reliability of operation of the switching switch is surely improved by increasing the probability. Also, the fact that overvoltage protection can be achieved in this circuit is similar to the explanation regarding FIG. 2.

FIG. 10 shows an embodiment in which the first principle and the second principle are combined. FIG. 11 is an operation sequence diagram of the circuit of FIG. 10.

The sequence in Figure 11 moves from tap 2 to tap 3 by proceeding from left to right as you move toward the page in the diagram.
By moving from right to left, the switch from tap 3 to tap 2 is completed. The ability to provide overvoltage protection in FIG. 10 is the same as the explanation regarding FIG. 3.

FIG. 12 shows an embodiment based on the second principle. FIG. 13 is an operation sequence diagram thereof. In the circuit of FIG. 12, as the operation sequence progresses from left to right as viewed from the page in FIG. 13, switching from tap 2 to tap 3 is completed, and as it progresses from right to left, switching from tap 3 to tap 2 is completed.

Also, the fact that overvoltage protection can be achieved in this circuit is the same as the explanation regarding FIG. 3.

FIG. 14 shows another embodiment based on the second principle. FIG. 15 shows an operation sequence diagram. The movable switching arms h and e perform switching operations at the timings shown by solid lines when the sequence progresses from left to right in FIG. 15, and perform switching operations at the timings shown by broken lines when the sequence is reversed. As the sequence progresses from left to right in FIG. 15, it switches from tap 2 to tap 3, and vice versa, as in the other embodiments described above. The overvoltage protection operation is the same as the explanation in FIG. 3. Furthermore, by operating the movable switching arms h and e in the sequence shown in FIG. 15, even if the main arc contact vacuum switch A fails to commutate the load current, as in the embodiment shown in FIG. Switch C
will be inserted in series with the load current circuit,
It is clear that the changeover switch has a very large practical effect by playing the role of backup protection in case of failure of vacuum switch A, etc., and its effects can be summarized as follows.

(a) Conventionally, a special spark gap or the like was required to protect the switching switch from overvoltage, but according to the present invention, a current switching element can be used for both purposes.

(b) Compared to conventional circuits, the number of current switching elements can be reduced, resulting in great economical effects.

(c) Furthermore, by devising the method of inserting the switching movable arms h and e into the circuit and the order of their operation, it becomes possible to use resistance contacts as backup protection against failure of the main arc contact.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram of a conventional switching switch, FIGS. 2 to 4 are connection diagrams for explaining the configuration of the present invention, and FIG. 5 is a connection diagram showing an embodiment of the present invention.
Figures 6-1 are connection diagrams showing the operating states of the configuration shown in Figure 5, Figure 7 is a diagram showing the operating order of the contacts in the operating process of Figure 6, and Figure 8 is another embodiment of the present invention. 9 is a diagram showing the operating order of the contacts in FIG. 8, FIG. 10 is a connection diagram showing still another embodiment of the present invention, and FIG. 11 is a diagram showing the operating order of the contacts in FIG. 10. FIG. 12 is a connection diagram showing still another embodiment of the invention, FIG. 13 is a diagram showing the operating order of the contacts in FIG. 12, and FIG. 14 is a diagram showing still another embodiment of the invention. The connection diagram shown in FIG. 15 is a diagram showing the operating order of the contacts in FIG. 14. Note that the same reference numerals in the figures indicate the same or corresponding parts. A and B are vacuum switches for main arc contacts, C and D
is a vacuum switch for resistance contacts, R ₁ and R ₂ are resistors for current limiting, 1 is a spark gap, h and e are switching movable arms of switching contacts, h ₁ , h ₂ , e ₁ and e ₂ are h and e is the fixed contact that is turned on, a is the bridge switching contact, a ₁
and a ₂ are fixed contacts to which a is turned on, 4 is the output terminal of the switching switch, 2 and 3 are adjacent taps such as a transformer, and 5 and 6 are the input terminals of the switching switch.

Claims (1)

[Scope of Claims] 1. In a device in which a vacuum switch is used as a current switching element of a switching switch of an on-load tap switching device, a pair of switching switches each connected to adjacent taps of a transformer or a reactor, etc. a resistor having an input terminal and inserted to limit the current flowing in an inter-tap bridging circuit formed during tap switching; and a switching switch inserted to cut off the bridging circuit. A vacuum switch that can be used as an overvoltage protection element and another resistor for current limiting different from the resistor are connected in series, and both ends of the circuit are connected to a pair of input terminals of the switching switch. , has a set of changeover switches that switch from one terminal to the other after short-circuiting both ends when the vacuum switch is in the closed state, and the movable arm of this changeover switch is used as the output terminal of the changeover switch. , characterized in that it has a switching contact configured so that one end of the vacuum switch for the main arc contact of the switching switch can be switched from the operating tap to the preselected tap in a no-current state. Switching switch for tap switching device. 2. In a vacuum switch used as a current switching element of a switching switch of an on-load tap switching device, the switching switch has a pair of input terminals each connected to adjacent taps of a transformer or reactor, etc. A resistor is inserted to limit the current flowing in the inter-tap bridging circuit formed during tap switching, and a resistor is opened and closed separately to cut off the bridging circuit and transfer the load current from the tap during operation. two vacuum switches connected in series, configured so that the vacuum switches inserted for commutating current to the preselection tap and open in the tap home position can be used as overvoltage protection elements of the switching switch; Both ends of an electric circuit formed by connecting in series a current limiting resistor different from the resistor are connected to a pair of input terminals of the switching switch, and both of the two vacuum switches are closed. The movable arm of a set of changeover switches, which short-circuits both ends of the series-connected electric circuit of the two vacuum switches and then switches from one terminal to the other terminal at both ends, is used as the output terminal of the changeover switch. , a tap switching under load, characterized in that it has a switching contact configured to be able to switch one point of the series-connected circuit of the two vacuum switches from the operating tap to the preselected tap without current. Equipment switching switch. 3. In a vacuum switch used as a current switching element of a switching switch of an on-load tap switching device, the switching switch has a pair of input terminals each connected to adjacent taps of a transformer or reactor, etc. A resistor is inserted to limit the current flowing in the inter-tap bridging circuit formed during tap switching, and a resistor is inserted to limit the current flowing in the inter-tap bridging circuit that is formed during tap switching. Two vacuum switches connected in series are configured so that the vacuum switch in the open state can be used as an overvoltage protection element of the switching switch, and another resistor for current limiting different from the resistor. Both ends of the electrical circuit connected in series are connected to a pair of input terminals of the switching switch, one point of the electrical circuit for connecting the two vacuum switches in series is set as an output terminal of the switching switch, and Switching of a tap switching device on load, characterized in that it has a switching contact configured so that a vacuum switch for the main arc contact of a switching switch can be switched from an operating tap to a preselected tap without current. switch.