JPS5939895B2 - Tap switching device under load - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a switching switch having a short-circuit prevention function between taps in an on-load tap switching device.

If the current-carrying contact suddenly fails during the switching operation of the on-load tap changer, it may cause a short circuit between the taps, which may cause an accident to spread not only to the on-load tap changer but also to the transformer itself.

In order to quickly cut off the short circuit current when such a short circuit occurs between taps, an overcurrent fast cut-off element (
(fuse, etc.) is inserted. A conventional device of this type has a wiring configuration shown in FIG. In the figure,
T is the adjustment winding of the transformer, 1 and 2 are the tap options of the tap selector that selects the odd and even side taps on T, respectively, and 3 and 4 are the switching switches connected to 1 and 2 above, respectively. These are the odd-numbered side input terminal and the even-numbered side input terminal.

B is a main arc contact, which is a current-carrying fixed contact 5 connected to the vacuum switch VS and the pair of input terminals 3 and 4, respectively;
6 and an energizing movable contact T that selectively engages with these 5 and 6, the current is cut off with VS and the electric path is changed with 5, 6, and T. Further, 8 is an output terminal of the switching switch, and A is a contact exclusively for energizing, which selectively engages fixed contacts 9 and 10 for energizing, which are connected to the pair of input terminals 3 and 4, respectively. It is composed of a dedicated movable contact 11.

13 and 14 are fixed contacts connected to the respective input terminals 3 and 4, and 15 is a fixed contact connected to the input terminal of the preselection tap among the input terminals of the switching switch, prior to the operation of any contact or switch of the switching switch. A pre-closing movable contact, R, is a current-limiting resistor, which is connected in advance to the connected fixed contact, and R is a current-limiting resistor, and 2 is a movable contact that closes before the vacuum switch opens, and opens after the vacuum switch closes. Resistance contacts IT, 18, which are connected to each other and inserted in series with the current-limiting resistor R1, are inserted in series between the switching switch input terminal 3 or 4 and the current-carrying fixed contact 5 or 6, respectively. This is an overcurrent fast-break element (hereinafter referred to as a fuse).

Figure 1 shows the current-carrying movable contact T) The current-carrying only contact 11 and the advance closing movable contact 15 are respectively closed to the current-carrying fixed contact 5, the current-carrying fixed contact 9, and the fixed contact 13, the vacuum switch VS is closed, and the resistance Contact No. 2 is open, and the load current flows from the regulating winding T of the transformer through the 1-3-9-11-8 circuit and the 1-3-17-5-T-VS-8 circuit. The state is shown in which the odd-numbered taps are energized.

From this state, switch to the even-numbered tap. The principle of tap switching operation will be explained according to the operation sequence shown in FIG. In addition,
Regarding the states of the contacts 3 to 15 in FIG. 2, the solid line arrows indicate a switching sequence from odd number side taps to even number side taps, and the broken line arrows indicate a switching sequence from even number side taps to odd number side taps. First, the advance closing movable contact 15 is switched from the odd-numbered fixed contact 13 to the even-numbered fixed contact 14 .

Next, the movable contact 11 for energization is connected to the fixed contact 9 for energization on the odd number side.
The load current is supplied through the electrical path of 1-3-17-5-J and 1-3-17-57-S-C- by opening the resistive contact and closing the resistive contact. R1-15-
An inter-tap circulating current flows through the 14-4-2-T circuit. Next, the vacuum switch S is opened, the current-carrying movable contact 7 is switched and connected from the current-carrying fixed contact 5 on the odd-numbered side to the current-carrying fixed contact 6 on the even-numbered side, the vacuum switch VS is closed, and the resistance contact C is opened. After that, the switching operation is completed by closing the energizing-only movable contact 11 to the even-numbered energizing-only fixed contact 10.

The switching operation to switch this to the even-numbered side tap is the complete opposite of the above switching operation process, except that the advance closing contact is switched and connected before all contacts or switch operation, and in the energization order, the above switching (This is called an electrically reversible relationship). As described above, in the conventional system shown in Figure 1, the switching from the odd side to the even side and the switching from the even side to the odd side are electrically reversible in the circuit switching process, and the resistance contact is The energizing contact closes after the contact is opened, and the circulating current between the taps flows only during a very short period from when the resistance contact q closes until the vacuum switch S opens. Since the switching is performed using a vacuum switch, the switching switch chamber is not contaminated. In the above switching process, if the vacuum switch VS fails to cut off the current due to a vacuum leak, for example, in the case of switching from an odd-numbered side tap to an even-numbered side tap, the next switching operation (I In other words, a space arc is generated when the current-carrying movable contact 7 opens and separates from the odd-number side fixed contact 5, and the current-carrying movable contact 7 is closed with the even-number side current-carrying fixed contact 6 (indicated by in Fig. 2). ), a short circuit occurs between the taps of 13-17-5-space arc-J and U-18-42-T via the space arc, causing an excessive current to flow.

Therefore, at least one of the fuses 17 and 18 is quickly blown to eliminate the short-circuit current between the taps. However, the conventional load tap switching device described above has the following drawbacks.

For example, if a short circuit occurs between the taps due to a failure in the current interruption of the vacuum switch S during switching operation from an odd-numbered tap to an even-numbered tap, and only the fuse 18 on the preselected tap side is blown, or the fuse 18 on the preselected tap side and the preselected tap side is blown. If fuses 17 and 18 on the selection tap side are both blown, the movable contact 1 for energizing
1 is applied to the energizing fixed contact 10 on the preselection tap side, only one load current circuit of 24-14-15-R1-q-8 is formed. However, before the energizing-only movable contact 11 closes the energizing-only fixed contact 10, the contact C
Since there is a process in which the contact point C is opened (as shown in FIG. 2), an arc is generated when the contact point C is opened, which has the disadvantage that there is a possibility of an accident spreading. During this arc generation period, that is, after the contact C is opened, the movable contact 11 for energization and the fixed contact 1 for energization
Although the period until the circuit closes to 0 is not long, it is a phenomenon in which the current-carrying circuit is temporarily disconnected, which is not at all preferable. In addition, when a fuse blows out due to a short circuit between taps, a very sudden restart voltage is generated when the fuse is extinguished, and the fuse cannot be extinguished or the generated restart voltage may cause other The purpose of this invention was to eliminate the above-mentioned drawbacks of the conventional method, which had the disadvantage that the insulation part could be damaged.By inserting a resistance element in parallel with the fuse, To provide an on-load tap switching device capable of surely removing fault current without fear of circuit breakage even when short-circuited between taps, and suppressing re-electromotive voltage when extinguishing a fuse.

An embodiment of the present invention will be described below with reference to the drawings.

In the circuit diagram of Fig. 3, 19 and 20 are fuses 17,
18 are respectively inserted in parallel with each other. The rest of the configuration is the same as that in FIG. 1, so the explanation will be omitted. The tap switching operation process of the circuit in FIG. 3 is similar to the operation sequence shown in FIG. 2, and during normal switching, the load current and the circulating current between the taps flow through the fuse and do not flow into the resistive element. The load current during normal switching and the circuit for circulating current between taps are also the same as in the conventional system. Therefore, the following is a case where the vacuum switch VS fails to cut the current and the fuse blows due to a short circuit between the taps, especially when only the fuse on the preselection tap side blows or when both fuses blow. I will explain about it. As shown in Fig. 3, for example, in the case of the fuse blowing in the above two ways when switching from odd-numbered taps to even-numbered taps, the short-circuit current between the taps is removed, and the load current is 2-414.
-15-R1-C-8 and the 2-4-20-67-S-8 path passing through the failed vacuum switch VS. Next, the vacuum switch S is closed, but the electrical circuit is the same as the electrical circuit described above. Subsequently, when contact C is opened, the load current is commutated to the path 2-4-20-6-J and r-8, and finally to the even-numbered fixed contact 10 for energization on the even-numbered movable contact 11 for energization. By closing, a 2-4-10-118 electric path is formed and the switching is completed. Therefore, the switching operation can be completed without momentarily disconnecting the load current circuit, regardless of where the fuse blows. Furthermore, since there is an electrically reversible relationship in the switching operation from the even-numbered tap to the odd-numbered tap, it can be easily inferred that a similar effect can be obtained.
Furthermore, the inserted resistance element reduces the re-electromotive voltage generated across the fuse when it blows, making it easier to extinguish the fuse and preventing damage to the insulating section from the re-electromotive voltage. It can be prevented. Furthermore, since the current conduction time when a load current flows through the resistance element is extremely short, the above effect can be expected even if the resistance element has a small heat capacity. The above explanation is based on a one-resistance type circuit configuration in which the resistance contact opens before the energization-only contact closes, but the resistance contact opens before the energization-only contact on the preselection tap side closes. Even in a multi-resistance type, as long as it opens,
Furthermore, the same effect can be obtained in a one-resistance type in which there is no resistance contact on the preselection tap side. Furthermore, it goes without saying that the main arc contact is not limited to the vacuum switch, but other switches may also be used. FIG. 4 shows another embodiment of the present invention, which is a two-resistance type circuit configuration having an operation sequence in which the resistance contact is opened before the current-carrying contact is closed.

In Fig. 4, "Oimata" and "h" are the energizing contacts on the odd and even side, "A" and "H" are the main arc contacts on the odd and even side,
Cl, C2 are odd and even side resistance contacts, 17,1
8 is a fuse, 19 and 20 are odd-numbered and even-numbered resistance elements inserted in parallel with the fuse, and Rl and R2 are current-limiting resistors. In Figure 4, when switching from the odd-numbered side to the even-numbered side, if the main arc contact B1 on the odd-numbered side fails to break and the arc connects, a short circuit is created by closing the main arc contact B2 on the even-numbered side. It is formed. When only the fuse 17 on the odd number side is blown by this short circuit current, the short circuit is immediately broken and the load current flows through the circuit passing through the fuse 18, and when the energizing contact Δ is closed, the fuse 18 and the energizing contact ▲ The switching is completed. In addition, due to short circuit current, only the even-numbered fuse 18 may be blown, or both fuses 17 and 1 may be blown.
8, the short circuit is immediately broken, and the current flows through the current limiting resistor R2 and the resistive element 20, and when the resistive contact S is opened, it is transferred to the resistive element 20, and finally the current-carrying contact A is opened. When the circuit is closed, the current passes through the circuit, and the switching is completed. During this switching period, the electrical circuit is not disconnected even for a moment, and the short circuit current can be reliably disconnected. Further, the same applies to switching from the even number side to the odd number side, so a description thereof will be omitted. The effects of inserting the other resistor elements 19 and 20 are no different from those of the one-resistance type described above. Next, another embodiment according to the present invention will be described with reference to FIG.
Prisoner in Figure 5! is the odd-numbered side and even-numbered side energizing-only contact, dan, dan is the odd-numbered side and even-numbered side main arc contact, C
is a resistance contact, R is a current limiting resistor, 17 and 18 are fuses, 1
9 and 20 are resistance elements inserted in parallel with the fuses 17 and 18. Next, the operation will be explained. If the main arc contact B1 fails to break when switching from the odd-number side tap to the even-number side tap (switching from the A1 side to the A2 side in the figure), the even-number side main arc contact B2 will close. A short circuit is formed between the taps. If only the fuse 17 blows out, the short circuit is immediately broken, and the load current is diverted to the electrical path passing through the fuse 18, and the even-numbered energizing contact A2
Switching is completed when the switch is closed. In addition, fuse 18 is caused by short circuit current.
If only or both fuses 17 and 18 are blown, a circuit is formed in which the current flows through the resistive element 20, and then the switching is completed by opening the resistive contact C and closing the even-numbered energizing contact A2. During this switching period, the short-circuit current can be reliably cut off without the electrical circuit being disconnected even for a moment. Other resistance elements 19
The effect of inserting 20 and 20 is the same as that of the one-resistance type described above, so a description thereof will be omitted. Furthermore, if a short circuit occurs between the taps when switching from an even-numbered tap to an odd-numbered tap, it is clear that the same effect as shown in the explanation of FIG. 4 will be obtained by the action of the resistive element 19 inserted on the odd-numbered side. Therefore, the explanation will be omitted. The explanation so far has been about the case where a fuse is inserted on each of the odd-numbered side and an even-numbered side and a resistance element is inserted in parallel with the fuse, but it is also possible to insert a fuse only on either the odd-numbered side or the even-numbered side in parallel with the resistance element. It is obvious from the above explanation that the above effects can be achieved even by inserting a circuit. However, in this circuit configuration, even if the parallel circuit of the fuse and the resistor element is switched to the preselected tap side, causing a short circuit between the taps and the fuse blowing out,
Depending on the circuit conditions, there is a possibility that the current that had been flowing through the main arc contact on the selected tap side that failed to break may continue to flow without being commutated to the resistive element or current limiting resistor. If the energizing contact closes in this state, the taps will be shorted again, so to prevent the worst case, insert a parallel circuit of fuses and resistive elements on both the odd and even sides, depending on the circuit conditions depending on the individual application. This is convenient because there is no need to consider By inserting a resistive element in parallel with the fuse as described above, even if a short circuit occurs between taps, the fault can be immediately removed by blowing the fuse, and the load current circuit will not be disconnected regardless of where the fuse blows. Switching is completed immediately, and furthermore, the re-electromotive voltage generated when the fuse blows can be reduced, resulting in the effect that damage can be kept to a minimum.

[Brief Description of the Drawings] Fig. 1 is a diagram showing the wiring configuration of a conventional device, Fig. 2 is an operation sequence diagram of the conventional device shown in Fig. 1, and Fig. 3 is a connection diagram showing an embodiment according to the present invention. , FIG. 4 is a connection diagram showing another embodiment according to the invention, and FIG. 5 is a connection diagram showing another embodiment according to the invention.

Claims (1)

[Claims] 1 A dedicated energizing contact inserted and connected between a pair of input terminals and output terminals selectively connected to the odd-numbered taps and even-numbered taps of the transformer winding, and a contact in series between each of the above input terminals and the above output terminal. The energizing contact on the preselection tap side is connected through a current limiting resistor between the inserted series body of the overcurrent fast disconnection element and the main arc contact, and at least one of the pair of input terminals and the output terminal. An on-load tap switching device characterized by comprising a resistive contact that opens before closing, and a resistive element connected in parallel to the overcurrent fast disconnection element.