JPH0452604B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a two-resistance type on-load tap changer using a vacuum valve. This relates to an improvement that prevents short circuits between taps.

[Technical background of the invention and its problems] Vacuum valves have advantages such as excellent shutoff performance, long contact life, and because the arc is extinguished in the vacuum container, oil is not contaminated. Therefore, in recent years it has been used in switching switches for on-load tap changers. An example of the circuit of a conventional on-load tap changer using such a vacuum valve is shown in FIG. 6, and the opening/closing sequence of the vacuum valve is shown in FIG.

In the conventional on-load tap changer shown in FIG. 6, a tap winding W _T is provided in the low voltage or high voltage winding of a transformer. This tap winding W _T is provided with a plurality of taps, for example taps T ₁ and T ₂ are shown. Also, the tap changer on load has taps T ₁ and T ₂ .
It is provided with movable contact circuit parts 3a and 3b on the a side and the b side that are connected in contact with. That is, the movable contact circuit section 3a on the a side has a resistive contact vacuum valve (hereinafter abbreviated as valve Wa) in series with the movable contact _1a that is in sliding contact with the tap _T1 between the tap T1 and the neutral point N.
A main contact vacuum valve Ha (hereinafter abbreviated as valve Ha) is provided, and a connection point 5a between both valves Wa and Ha is provided.
For example, a current limiting resistor Ra is connected between the neutral point N and the neutral point N as a current limiting member. Similarly to the a side, the movable contact circuit section 3b on the b side is connected between the tap _T2 and the neutral point N.
It is constructed as shown in the part number and name code with the subscript b.

If we consider a case where the shutoff performance of the vacuum valve of such a conventional on-load tap changer deteriorates and the arc cannot be extinguished, the following will occur.

() If the switching progresses while the arcs of valves Ha and Hb are prolonged, the a side changes from closed to open, the b side changes from open to closed, according to the sequence shown in Figure 7. The a side is left open and moved to another tap (not shown). Also, valves Ha and Wa are connected in series on the a side, and valves Hb and Wa are connected in series on the b side.
Since Wb is connected in series, valves Ha,
When the vacuum level of the Hb becomes poor, the interrupting performance deteriorates, and the arc is prolonged, the valve
The current will be interrupted by Wa and Wb.

At this time, the duty of shutting off the valves Wa and Wb is more difficult than their normal duty, but because the shutoff ability of the vacuum valve is large, the shutoff is completed and a situation such as a direct tap-to-tap short circuit does not occur.

() When the breaking performance of valves Wa and Wb deteriorates and the arc is prolonged. When switching progresses in such a case, according to the sequence, valve Ha opens on side a, which is closed, and then valve Wa opens.
becomes open. Also, the b side that is open is a valve.
Wb is closed, and then valve Hb is closed. In this process, circulating currents determined by the step voltage and the values of the current limiting resistors Ra and Rb continue to flow through the valves Wa and Wb to the a side and the b side, respectively. Therefore, there is a risk that the current limiting resistors Ra and Rb may overheat and melt due to this circulating current. Since the circuit breaker can be tripped by detecting the pressure change within the switching switch container due to the expansion of the gas generated at that time, it is possible to prevent a short circuit between the taps.

() When the shutoff performance of both valves Ha, Hb and valves Wa, Wb deteriorates. i.e. the valve
If the breaking performance of both Ha, Hb and valves Wa, Wb decreases at the same time, a short circuit will occur between the taps.

As mentioned above, in the conventional on-load tap changer shown in Fig. 6, the valves Ha, Hb and valves Wa,
If the breaking performance of both Wb decreases at the same time, there is a risk of short circuit between taps. Also the valve
When the breaking performance of Wa and Wb decreases, the current limiting resistor
Circulating current flows through Ra and Rb, and current limiting resistors Ra and Rb
Since the circuit breaker is tripped by detecting the increase in gas pressure caused by heat generation and melting, there is a problem that needs to be solved in that it is not possible to detect the circuit breaker in a short period of time before the trip occurs.

[Purpose of the invention]

The present invention was made in consideration of the above differences, and
The purpose is to provide an on-load tap changer that prevents accidents such as short circuits between taps and overheating burnout of current limiting resistors due to deterioration in the shutoff performance of the main contact vacuum valve and resistance contact vacuum valve. It's about doing.

[Summary of the invention]

According to the present invention, in order to achieve such an objective,
An auxiliary contact is provided between the connection point between the first vacuum valve and the current limiting resistor and the second vacuum valve in each of the pair of movable contact circuit sections, and the contact point is provided in the vicinity of the current limiting resistor and the auxiliary contact. A plurality of photodetectors are provided in the load tap changer, an optical/electrical converter is provided outside the on-load tap changer container, and the photodetector and the optical/electrical converter are connected by an optical fiber via an infrared filter. This feature prevents short circuits between taps and overheating burnout of the current limiting resistor.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. The same parts as in FIGS. 6 and 7 are given the same reference numerals. In FIG. 1, the on-load tap changer is provided with a plurality of taps, for example, taps T ₁ and T ₂ in the illustration, on a tap winding W _T provided in a low-voltage or high-voltage winding of a transformer. Tap again
The movable contact circuit parts 6a and 6b on the a side and b side, which are connected by contacting _T1 and _T2 , are connected to a pair of taps _T1 and _T2.
and the neutral point N.

The movable contact circuit section 6a on the a side has a movable contact ₁ that is in _sliding contact with the tap T1 between the tap T1 and the neutral point N.
Resistance contact vacuum valve Wa (hereinafter referred to as valve) is connected in series with a
A main contact vacuum valve Ha (hereinafter abbreviated as valve Ha) is provided, and both valves Wa,
Auxiliary contact between connection point 5a between Ha and valve Ha
Set up Ka. Furthermore, a current limiting resistor Ra is connected between the connection point 5a and the neutral point N so as to be in parallel with the auxiliary contact Ka and the valve Ha, thereby forming a movable contact circuit section 6a.

Similarly to the a side, the movable contact circuit section 6b on the b side has a resistive contact vacuum valve Wb in series with the movable contact 1b which is in sliding contact with the tap _T2 between the tap _T2 and the neutral point N.
(hereinafter abbreviated as valve Wb) and a main contact vacuum valve Hb (hereinafter abbreviated as valve Hb) are provided, and an auxiliary contact Kb is provided between the connection point 5b between both valves Wb and Hb and valve Hb, and A movable contact circuit section 6b is configured by connecting a current limiting resistor Rb in parallel to an auxiliary contact Kb between the connection point 5b and the neutral point N and the valve Hb.

The a-side and b-side movable contact circuit parts 6a and 6b configured in this way are placed in a container 7 of a load tap changer.
Store inside. The taps T ₁ and T ₂ and the movable contacts 1a and 1b in sliding contact therewith are arranged on the outside of the container 7.

Inside this container 7, near the auxiliary contacts Ka and Kb and the current limiting resistors Ra and Rb, a photodetector 8 is arranged with one end of the optical fiber _F1 directed. Also container 7
The ends of a plurality of optical fibers _F1 opposite to the light detection part 8 are attached to the optical fiber connection part 10 attached to the lid 9 of
F ₂ is provided, and the container 7 is connected by this optical fiber F _{2 .}
A light-to-electricity conversion device 11 disposed outside is connected. As shown in FIG. 2, the optical fiber connection part 10 is located in the middle of a step-through mounting hole in the lid 9.
An infrared filter 13 is inserted through a packing 14 so as to partition this mounting hole, and a mounting plate 15 to which one ends of a plurality of optical fibers F ₁ are fixed is attached to the inside of the lid 9. A mounting plate 1 is fixed to the outside of the infrared filter 13, that is, on the opposite side to the mounting plate 15, through which one end of a plurality of optical fibers _F2 is fixed.
Install 6. The optical fibers F ₁ and F ₂ are arranged so as to face each other and align the optical axes. Further, although not shown, the optical/electrical converter 11 is constructed using a photodiode or a phototransistor as a main component.

Next, the effects of the present invention will be explained. In a load tap changer with such a configuration, if we consider the case where the arc is extended due to a decrease in the interrupting ability of the vacuum valve, in the case of valves Wa and Wb, as mentioned above, the circulating current is vessel
The current flows through the circuit in the order of Ra, valve Hb, and valve Wb, or valve Wb, current limiting resistor Rb, valve Hb, and valve Wa, and current limiting resistor Ra or Rb becomes red hot. Since the photodetector 8 is provided near the current limiting resistors Ra and Rb, it is possible to detect the light caused by the red heat of the current limiting resistors Ra or Rb. By the way, when the load tap changer switches normally, current flows through the current limiting resistors Ra, Rb and other current-carrying parts, and infrared rays are generated in the vicinity of the photodetector 8, but the optical fiber connection of the lid 9 The light is attenuated by an infrared filter 13 provided in the section 10. In other words, it is possible to distinguish between light from the accident and infrared light entering from other parts.

Next, when arc extension occurs in valves Ha and Hb, the auxiliary contacts Ka and Kb open and arc before valves Wa and Wb open, following valves Ha and Hb, as shown in Figure 3. do. As the switching progresses further, valves Wa and Wb open and cut off the current.
The arcs of the auxiliary contacts Ka, Kb and the valves Ha, Hb are also extinguished to complete switching, but the visible light caused by the arcing of the auxiliary contacts Ka, Kb is transmitted to the photodetector 8 and the optical fiber.
Since the firing of the auxiliary contacts Ka and Kb can be detected by being transmitted to the optical-electrical converter 11 via F ₁ and F ₂ , it is possible to know if there is an abnormality in the vacuum valve. Therefore, the transformer can be stopped, the tap changer can be inspected under load, and the vacuum valve can be replaced, thereby preventing short circuits between taps during the process described above.

Here, the auxiliary contacts Ka and Kb only need to perform the function of generating an arc and detecting an abnormality when arc extension occurs in the valves Ha and Hb, and are mechanically simple as they do not require any particular breaking ability. That's fine. In addition, the operation timing of auxiliary contacts Ka and Kb is synchronized with valves Wa and Wb in Fig. 3, but in reality, valves Wa and Wb are opened after the normal arc of valves Ha and Hb is extinguished. Just open it before it reaches its peak.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 and 5. The same parts or parts having the same functions as those in FIG. 2 are given the same reference numerals or symbols. In FIG. 4, the optical fiber connecting portion 10 combines the optical fibers F ₁ branched inside the lid 9 into one and is fixed to the mounting plate 15 by a connector 17 . A single optical fiber F ₂ is fixed to the mounting plate 16 by a connector 18 on the outside of the infrared filter 13 . By combining such a plurality of optical fibers into one, the production of this optical fiber connecting portion 10 becomes easy.

Still in FIG. 5, the optical fiber connection 10
is a connector body 19 that is attached to the lid 9 by penetrating it.
The infrared filter 13 is housed in the connector body 19, and the optical fibers F ₁ and F ₂ having the mounting fittings 20 are screwed into the connector body 19 from both sides.
This has the advantage that it is easier to manufacture.

In addition, auxiliary contacts Ka, Kb and current limiting resistors Ra,
Since the light detected near Rb is transmitted to the optical-to-electrical converter 11 by the optical fibers F ₁ and F ₂ , electrical induction from the transformer can be prevented.
In particular, if there is no risk of such induction, the optical fiber _F2 may be omitted and the optical-to-electrical converter 11 may be installed near the switching switch.

Furthermore, although the gas-insulated on-load tap changer has been described above, an oil-insulated one can also have the same effect as the embodiment of the present invention by providing an auxiliary contact and detecting the firing using visible light. can get.

〔Effect of the invention〕

As explained above, according to the present invention, a photodetector is disposed near the auxiliary contact and the current limiting resistor of each of the pair of movable contact circuits, and is inserted into the optical cable connection section provided in the container. By connecting the light detection section and the light-to-electricity conversion section provided on the outside of the container with an optical fiber via an infrared filter, it is possible to detect the visible light of the arc of the auxiliary contact and prevent short circuits between the taps. can. Furthermore, by detecting the light generated by the red heat of the current limiting resistor, it is possible to prevent blowout with higher sensitivity than by detecting the rise in gas pressure using a conventional melting stage caused by heat generation. Furthermore, the inside and outside of the container can be airtightly partitioned at the optical fiber connection part. Furthermore, an infrared filter provided at the optical fiber connection part attenuates infrared rays during normal switching, and visible light, that is, light that could lead to an accident, can be detected.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the on-load tap changer according to the present invention including a circuit diagram, Fig. 2 is an enlarged cross-sectional view of the optical fiber connection part of Fig. 1, and Fig. 3 is the sequence of operation of Fig. 1. 4 and 5 are enlarged sectional views of essential parts of other embodiments of the present invention, and FIGS. 6 and 7 are circuit diagrams and sequence diagrams of conventional on-load tap changers. 6a, 6b...movable contact circuit parts on the a side and b side, 7...container, 8...photodetection unit, 9...lid, 1
0...Optical fiber connection part, 11...Optical/electric conversion part, 13...Infrared filter, W _T ...Tap winding, _T1 , _T2 ...Tap, 1a, 1b...Movable contact, Ra , Rb... Current limiting resistor, Ka, Kb...
Auxiliary contact, Wa, Wb...resistance contact vacuum valve,
Ha, Hb...Main contact vacuum valve, _F1 , _F2 ...Optical fiber.

Claims (1)

[Claims] 1. First and second vacuum valves are connected in series between a pair of movable contacts that contact the tap of the tap winding and a neutral point, and a connection point between the first and second vacuum valves and the neutral point are connected in series. In the on-load tap changer comprising a pair of movable contact circuit sections each having a current limiting resistor connected in parallel with the second vacuum valve between the two terminals in a container, each of the pair of An auxiliary contact is provided between the connection point of the first vacuum valve and the current limiting resistor in the movable contact circuit section and the second vacuum valve, and the current limiting resistor and the auxiliary contact are connected to each other. A plurality of light detection sections are provided near the container, and the detection section is connected to the detection section via an optical fiber detection section provided with an optical/electric conversion section provided outside the container and an infrared filter provided in the container. An on-load tap changer characterized in that it is connected by.