JPH0795723A - Protective device for vacuum switch type on-load tap changer - Google Patents

Abstract

PURPOSE:To continue the operation of a transformer by connecting in parallel current limiting resistors and current transformers to the tap-side one of each two vacuum switches connected in series to each of the two taps of a tap winding and detecting an abnormal tap from the output signal of an AC device, and then, returning the abnormal tap to the state before starting operations when the abnormal tap is detected. CONSTITUTION:Main contact valves V1 and V3 and V2 and V4, each of which is composed of two vacuum switches, are connected in series to the taps I and II of a tap winding 1 and the valves V3 and V4 are conneced to the neutral point 9 of a transformer. In addition, serial circuits respectively composed of current-limiting resistors R1 and CT1 and R2 and CT2 are connected in parallel with the valves V1 and V3. The switching operation starting time and completing time of the valves V1 and V2 are inputted to an abnormality detector 15 together with the outputs of the resistors CT1 and CT2. When the detector 15 detects an abnormal tap from the inputted data, the detector 15 displays 16 the abnormal tap and returns the abnormal tap to the state before starting the operations by driving a motor 14 through a control board 13. Therefore, the operation of th transformer is continued.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching device protection device for preventing abnormalities from affecting the parts other than the switching device body when the vacuum switch in the vacuum switch type load tap switching device is abnormal. Regarding

[0002]

2. Description of the Related Art Recently, gas-insulated transformers using SF ₆ gas have been adopted in place of conventional oil-filled transformers because of the disaster prevention and environmental friendliness of substation facilities. Along with this, the load tap changer that adjusts the voltage of the transformer is also
A vacuum switch type load tap changer that does not use insulating oil is used. In addition, even in oil-filled transformers, compared to mechanical types that use insulating oil as an arc-extinguishing medium, the vacuum switch has excellent shutoff performance and there is no oil contamination, so it is often used in insulating oil for frequent switching. Vacuum valve that is the main body of the vacuum switch (high vacuum container with the main contact of the vacuum switch)
A vacuum switch type tap changer under load is also used. This vacuum switch opens and closes the current in a high vacuum container and has both excellent insulation and insulation properties. However, the vacuum switch may fail to shut off for some reason such as a vacuum leak. Also,
It is difficult to predict in advance the decrease in the breaking performance of the vacuum switch.

In the load tap changer provided with the four-valve type, that is, four vacuum switches, which is the object of the present invention, 2
Since the individual vacuum switches are connected in series, a one-tap short circuit cannot occur unless both of them fail to be shut off. However, once a one-tap short circuit occurs, a large current flows because the impedance of the winding is small, causing serious trouble such as damage to the tap winding. Therefore, as a conventional protection method,
A method has been adopted in which this short-circuit current is detected by a current transformer and the power is shut off to prevent the accident from further expanding.

FIG. 2 shows a tap for realizing this method.
3 shows a circuit configuration of a switching device including windings. The figure is
The case where the transformer is on the neutral side of the three-phase transformer is shown. Tat
Of the tap selector 2 to the two terminals derived from the winding 1.
The terminals at one end are connected to each other, and I of the tap selector 2 is connected.
Main contact valve at the other end of each side
V ₁, Current limiting resistor R in parallel with this₁, Resistance contact valve V
₃, And the main contact valve V ₂, Current limiting resistor in parallel with this
R₂, Resistance contact valve V_FourConnected and tap select again
Current transformer CT for detecting the I side current of the transformer 2₁, Tap selector
Current transformer CT that detects the II side current in the II side circuit of 2₂
Is equipped with. And the resistance contact valve V₃, V_FourWith
The connection point forms the neutral point of the three-phase transformer.

In this circuit configuration, the vacuum valve is abnormal.
When there is no switch, the switching operation of the switch changes as follows.
To do. That is, the switch uses the I side of the tap selector 2.
When operating with the
First, the main contact valve V₁Open, the transformer current will limit the current
Vessel (hereinafter referred to as resistance) R₁, Resistance contact valve V₃, Current
CT₁Flow to the neutral point 9 via
Please refer to the figure). In addition, CT in FIG.₁, CT₂Electric
Each flow has resistance R₁, R₂Shows only the current period through
ing). Resistance contact valve V_FourClose the transformer
Current is resistance R ₂, Resistance contact valve V_Four, Current transformer CT₂
Through the neutral point 9 and the tap winding 1
Resistance R between the two terminals derived from₁, R₂Is inserted
Therefore, depending on the tap winding voltage, tap winding 1
As a circulating current through the resistor R₁, R₂Due to the size
Limited current flows. In this state, the resistance contact valve V
₃Open the current transformer CT₁The current flowing through the transformer disappears
Current is resistance R₂, Resistance contact valve V_Four, Current transformer CT₂of
It flows into the neutral point 9 through the hole. So tap selector
II side main contact valve V₂Close the resistor R₂Pass through
When the current disappears, all the transformer current flowing into the neutral point 9
Main contact valve V₂, Resistance contact valve V_FourFlow through
Then, switching from the I side of the tap selector 2 to the II side is completed.
To do. Switching from the II side to the I side operates in the order symmetrical with the above.
It is possible by doing the work.

Therefore, if there is an abnormality in the vacuum switch in the switch and the main contact valve V ₁ fails to shut off, as shown in the diagram (when the main contact valve V ₁ fails to shut off) in FIG. Moreover, no current flows through the current transformer CT ₁ through the resistor R ₁ . The same applies when the resistance contact valve V ₄ is closed. However, a current begins to flow in the current transformer CT ₂ via the resistor R ₂ . Then open the resistance contact valve V ₃ ,
The switching from the I side to the II side is completed by closing the main contact valve V ₂ .

Further, when the main contact valve V ₁ is in an abnormal state, the user does not notice this and the tap selector is switched from the II side to the I side. Therefore, the II side main contact valve V ₂ is opened and the II side circuit is opened. When the resistance contact valve V ₃ on the I side is closed after inserting the resistance R ₂ into the, the main contact valve V ₁ on the I side immediately becomes conductive due to the terminal voltage of the resistance R ₁ .
No current flows through the resistor R ₁ . When the resistance contact valve V ₄ on the II side is subsequently opened, the current passing through the resistor R ₂ disappears, and the main contact valve V ₁ on the I side is closed to complete the switching from the II side to the I side.

As described above, even if the main contact valves V ₁ and V ₂ are abnormal, if only one of them is abnormal, a tap short circuit does not occur and the tap selector can be switched. Next, let us consider a case where there is an abnormality in the resistance contact valve V ₃ and the interruption fails. When switching from the I side to the II side, when V ₁ is opened and V ₄ is closed and then V ₃ is opened, V ₃
If it fails to shut off, the current passing through the resistor R ₁ will continue to flow due to the tap winding voltage even after V ₂ is closed, and R ₁ will be burned or melted. Then, the circuit breaker in series with the transformer operates and the operation of the transformer is stopped.

Also, V₃I didn't notice this when I got abnormal
When switching from I side to I side, V₂Open the resistance R₂，
R₁A circulating current begins to flow through the V₃Close
Same, V _FourOpen V₁Resistance R until closing₁Has no current
Keep flowing. The heat capacity that withstands heat generation during this current period is
Anti-R₁If you have one, you can switch from the II side to the I side.
Complete without any accident.

Thus, V₃, V_FourWhen an abnormality occurs,
When switching from I side to II side and II side to I side respectively
There is a risk of resistance burning or fusing. In addition,
As mentioned in₁, V₂When both are abnormal
I'm V₁, V₃, Or V ₂, V_FourEach at the same time
If something is wrong, depending on the direction of switching,
A tap short circuit occurs.

[0011]

A vacuum switch has a vacuum leakage.
This may indicate an abnormal condition such as a failure to shut off.
It Built in devices such as load tap changer
It is difficult to foresee this when it is in a closed state. However,
As mentioned above, the 4-valve load tap changer
In addition, even if the main contact valve is abnormal, I side, II
If there is no abnormality on both sides simultaneously, tap change as a 3-valve type
You can complete the picture. But of the vacuum switch
Abnormality is V₃, V_Four, Then from the I side respectively
When switching to the I side or from the II side to the I side
The current continues to flow. Generally, current limiting resistors have short-term capacity
Since it has only that, if current continues to flow, it will burn out or
There is a risk of fusing. Also, V₁, V₂, Or V
₁, V₃, Or V₂, V _Four2 valves each
If there is an abnormality at the same time, there is a danger of tap short circuit.
It Conventionally, even with this danger
Therefore, each vacuum switch is opened and closed, and tap short circuit occurs.
The transformer is disconnected from the power supply only when
This prevented damage to the switch. But,
If the transformer is disconnected from the power supply after the short circuit
The tap winding may be deformed due to
There was welding on the contacts of the vacuum switch that was there.
There is a problem that the occurrence of damage cannot be prevented. There
Therefore, in order to prevent the subsequent damage, tap short circuit may occur.
To detect accidents in advance and prevent accidents
As a protection device, for example, Japanese Patent Laid-Open No. 1-173613
The ones described in are proposed. This protector
Connect a current transformer in series with the main contact valve,
Connect the series circuit of the valve and current transformer in parallel with the current limiting resistor.
Continues to detect the current passing through the main contact valve
Enable and open the vacuum switch inside the changer
A cam switch that mechanically interlocks with the fast cutting drive shaft that drives
The position of the quick cut drive mechanism can be determined by attaching a contact to the quick cut drive shaft.
Positioning device is composed of output signal from current transformer and position determination device
Input the output signal from the
Normally, the current signal of the tap selector II side current transformer disappeared
Where the rear I side position determination signal is output, the I side position determination signal
The current signal of the II side current transformer is
If it does not disappear, in the comparison / determination circuit, press the II side vacuum switch
It is judged that the cutoff has failed and the subsequent operation progress is stopped.
Return each vacuum switch to the tap state before starting the switching operation.
It enables the operation to return. However, this
In the protection device, the vacuum switch opening / closing drive mechanism is connected to this.
Small mechanical parts such as moving cam switch contacts are attached
Therefore, the number of mechanical parts is increased, and the operation reliability of the opening / closing drive mechanism is increased.
May be damaged.

As another protection device capable of preventing tap short-circuiting, as disclosed in Japanese Patent Laid-Open No. 4-57085, the currents flowing in the current limiting resistors are respectively supplied to non-powered optical output currents. It is detected by the detector, and the optical output from this detector is input to the current energization time determination unit provided outside the load tap changer, and from the difference between the time set in the determination unit and the optical input duration time. There is one that detects the inability to shut off the vacuum switch. However, in this protection device, the unpowered optical output detection unit specifically includes a current transformer, a rectifying device, a light emitting diode, an optical fiber for guiding the light of the light emitting diode to the outside of the switch, and the like. Since many circuit components are incorporated in the switch main body, the inside of the switch becomes complicated, and there is a possibility that problems may occur in reliability in use.

An object of the present invention is to prevent the occurrence of an accident inside the switch due to an abnormality in the vacuum switch without incorporating many parts inside the switch and to prevent an accident such as a tap short circuit before it occurs. It is an object of the present invention to provide a protection device that enables at least immediate operation of the container.

[0014]

In order to solve the above-mentioned problems, in the present invention, a pair of tap selectors having a terminal connected to a tap winding at one end and a pair of tap selectors. 2 connected in series to the terminals at the other end of each
And a current limiting resistor connected in parallel to each of the two vacuum switches and one of the two vacuum switch middle tap selectors, and the anti-tap selector side end portions of the anti-tap selector side vacuum switches In the vacuum switch type load tap changer that connects the neutral point of the transformer or the line end of each phase transformer so that the abnormalities of the vacuum switch do not affect the parts other than the changer body. A protective device for each of the current limiting resistors connected in series to each current limiting resistor in parallel with the tap selector side vacuum switch in the state that the current limiting resistor has a current transformer in series. The connection is made, and it is judged which vacuum switch is abnormal from the current signal from each current transformer and the operation start signal to the load tap changer, and the abnormal signal is transmitted. Protector To.

Here, the protection device is controlled so that when any one of the vacuum switches is judged to be abnormal, each vacuum switch is restored to the tap state before the operation start signal, and each vacuum switch thereafter. It is more preferable to use a device that locks the operation.

[0016]

As described above, the purpose of the present invention is to reduce the power of the transformer after a tap short circuit occurs as in the prior art or to prevent the current limiting resistor from burning or melting. It is to avoid the influence of operation stop to the outside and to deal with the abnormality of itself by only the tap changer to enable at least the immediate operation of the transformer. Side and II side current detectors are installed to protect the tap short circuit from only the current of the current transformer and to prevent burnout or melting of the current limiting resistor. When it is in the accident possible state, it is not possible to immediately determine which abnormal switch combination is the cause of the accidentable state during the switching operation.Therefore, shut down the transformer power and stop the operation of the transformer. Inevitably Therefore, it is possible to determine which vacuum switch is abnormal each time the operation of each vacuum switch is performed, so that the operation stop of the transformer can be avoided. It was done. For this purpose, a current transformer is connected in series with the current limiting resistor, and the disappearance, generation, and size change of the current of the current limiting resistor are detected each time the vacuum switch operates to check whether there is an abnormality in the vacuum switch. I was able to distinguish. That is, if the current limiting resistor current is not detected even though the main contact valve is opened at the time of tap switching, it is judged that the main contact valve cannot be shut off. By performing the return operation and the operation lock of the remaining vacuum switches, it is possible to prevent a tap short circuit and an accident in the switch. If the resistance current continues to flow even if the resistance contact valve opens, it is determined that the resistance contact valve cannot be shut off (completion of operation of the resistance contact valve must be detected by the limit switch that detects the rotation angle of the electric operating device). If, for example, the restoration operation of the already operated vacuum switch and the operation lock of the remaining vacuum switches are performed based on this determination result, the occurrence of an accident in the switch can be prevented. Of course, such a determination as to whether or not there is an abnormality in the vacuum switch can also be made by connecting the current transformer in series with the main contact valve. However, in this case, even if the transformer current always flows in the current transformer and the accident prevention operation of the switching device is performed when the vacuum switch abnormality is detected, the current transformer must have the short circuit capacity specification. It is usually used. For this reason, the current transformer becomes large in size, which may hinder the downsizing of the switching device. As described above, in the protection device of the present invention, it is possible to easily determine whether or not there is an abnormality in the vacuum switch for each operation stage of the vacuum switch, and it is possible to operate the switcher without causing an accident. It is possible to continue operation at least for the time being.
The inability to shut off the vacuum valve is due to a vacuum leak in the valve container to a predetermined vacuum level or less, and it is normal to keep the high vacuum inside the valve container. Even if it continues, it takes a considerable time for the valve container to be damaged by the internal pressure, and the accident in the switching device is actually sufficient considering the burning or melting of the resistor.

Therefore, as a protection device, further, when any of the vacuum switches is judged to be abnormal, the respective vacuum switches are controlled so as to return to the tap state before the operation start signal, and the operation of each vacuum switch thereafter. If the protection device for locking the switch is configured, the operation of the transformer can be temporarily continued even when an abnormality occurs in the switch, and thereafter, it becomes possible to prevent the occurrence of an accident in the switch.

[0018]

FIG. 1 shows an embodiment of the present invention. Limiting resistor is connected in parallel to the main contacts valve _{V 1, V 2 R 1,} R 2
, And current transformers CT ₁ and CT ₂ are connected in series, respectively, and this series circuit is parallelized to the main contact valves V ₁ and V ₂ . If all the vacuum switches in the changer are healthy,
When switching the tap selector 2 from the I side to the II side, when the main contact valve V ₁ is opened, the transformer current flows through the current limiting resistor R ₁ and the current transformer CT ₁ detects this current. From this detected current and the operation start signal of the main contact valve V ₁ , it is judged that there is no abnormality in the main contact valve, and the resistance contact valve V ₄ on the tap selector II side is closed. Resistance contact valve V
By the operation of _4, the transformer current flows into the neutral point 9 through the current limiting resistor R ₂ and this current is detected by the current transformer CT ₂ . Since the main contact valve V ₂ is sound, the current limiting resistor R
_Since the terminal ₂ does not become conductive, the resistance contact valve V ₃ is opened and the current of the current limiting resistor R ₁ is cut off after a predetermined time has elapsed after the current detection of the current limiting resistor R ₂ . The current detected by the current transformer CT ₁ disappears, and the resistance contact valve V ₃ is judged to be sound from the disappearance of the detected current and the operation completion signal of the resistance contact valve V ₃ , whereby the main contact valve V ₂ is closed. The tap selector I is operated to complete the switching from the tap selector I side to the II side. Such judgment as to whether or not each vacuum switch is sound is made by detecting currents from the current transformers CT ₁ and CT ₂ and at the time of starting and ending the operation of each vacuum switch. It is performed in the device 15. If an abnormality of the vacuum switch is detected in each of the above judgment steps, which vacuum switch is abnormal is displayed on the display device 16, and the LTC (load tap) is received in response to the detection result. From the control panel 13 to the electric operating device 14, a return operation command is output so that the vacuum switch that has already operated returns to the tap state before the switching operation, and an operation lock command for the subsequent vacuum switch is output. .

[0019]

In the present invention, since the protective device for the vacuum switch type load tap changer is constructed as described above, the following effects can be obtained. In the protection device according to claim 1, a current transformer is connected in series to each current limiting resistor, and switching of the tap selector is performed such that the current limiting resistance current is generated, extinguished, or has a magnitude depending on the operation of each vacuum switch. Since it is performed while detecting whether there is a vacuum switch abnormality from the change, it is possible to operate the vacuum switch to prevent tap short circuits and accidents of the switching device itself, and even if there is a vacuum switch abnormality, tap short circuit It has become possible to prevent accidents such as above and continue operation of the transformer at least for the time being. This effect can be obtained without complicating the inside of the switch and without enlarging the switch.

In the protection device of the second aspect, there is an effect that the damage of the switching device itself is surely prevented.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a protection device configuration of a vacuum switch type load tap changer according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a vacuum switch type load tap changer targeted by the present invention and an example of a conventional protection device configuration.

FIG. 3 is a switching sequence diagram showing an operation sequence of each vacuum switch at the time of switching in the vacuum switch type load tap changer shown in FIG. 1 or 2.

FIG. 4 is a diagram showing a vacuum switch type load tap changer shown in FIG.
And an explanatory view showing a resistance current period flowing in the current transformers on both sides of the tap selector at the time of switching operation when any one of the vacuum switches is abnormal.

[Explanation of symbols]

 1 tap winding 2 tap selector 3 main contact valve 4 main contact valve 5 resistance contact valve 6 resistance contact valve 7 current limiting resistor 8 current limiting resistor 9 neutral point 11 current transformer 12 current transformer

Claims (2)

[Claims] 1. A pair of tap selectors each having a terminal connected to a tap winding at one end, and two vacuums connected in series to terminals at the other ends of the pair of tap selectors. A switch and one of the two vacuum switches on the tap selector side, and a current limiting resistor connected in parallel to each other, and connecting the end portions of the anti-tap selector side vacuum switch on the anti-tap selector side. In the vacuum switch type load tap changer that forms the neutral point of the transformer or the line end of each phase transformer, in order to prevent the abnormalities from affecting the parts other than the changer body when the vacuum switch is abnormal. Of the current limiting resistor, the current limiting device is connected in series, and the current limiting resistor is connected in parallel to the tap selector side vacuum switch with the current limiting device in series. And this is all The vacuum switch type characterized by determining which vacuum switch is abnormal from the current signal from the current transformer and the operation start signal to the load tap changer, and transmitting the abnormal signal. Protective device for tap changer during load. 2. The protection device according to claim 1, wherein:
A vacuum switch type characterized by controlling each vacuum switch to return to the tap state before the operation start signal when any vacuum switch is judged to be abnormal and locking the operation of each vacuum switch thereafter. Protective device for tap changer during load.