JP2007273646A - On-load tap switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superior at-load tap switch which is simplified in configuration by suppressing consideration into electrical insulation to a minimum, which can monitor the switching operation state of a changeover switch during the operation of a transformer, and thereby which can accurately detect the sign of abnormality of the changeover switch due to defective point, and the cause for the defect. <P>SOLUTION: A current-limited resistor 4 is stored in a container 5 filled with an insulating liquid. The container 5 is equipped with an insulation tube 6a to cause the insulating liquid to flow into the container 5, and an insulation tube 6b to cause the insulating liquid to flow out of the container 5. The insulation tubes 6a and 6b are provided with a temperature sensor 7 for detecting temperature difference between the insulating liquid flowing into the container 5 and the insulating liquid flowing out of the container 5, and the temperature sensor 7 has a diagnostic processor 9 for determining the abnormal state of the changeover switch 3, by calculating the calorific value of the current-limited resistor 4, based on the detection results of the temperature sensor 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a load tap changer capable of determining an operation abnormality of a switching switch during operation of a transformer.

  In general, transformer load-type tap changers are used in power transmission and distribution systems in order to regulate and stabilize the voltage. The on-load tap changer includes a tap selector that selects a tap of the tap winding and a change-over switch having a current limiting resistor, and is housed in a gas-insulated tank. Here, a conventional example of the on-load tap changer will be specifically described with reference to FIGS.

  As shown in FIG. 2, the on-load tap changer is housed in the transformer tank 14, and the switching operation is performed by the electric operation mechanism 1 arranged outside the transformer tank 14. . The on-load tap changer comprises a tap selector 2 connected to the tap winding of the transformer, and a switching switch 3 having a current limiting resistor 4. Among these, the switching switch 3 is a device for switching circuits while opening and closing the contacts during operation of the transformer, and is disposed in the switching switch chamber 15.

  FIG. 3 shows a switching circuit and an operation diagram in the conventional switching switch 3. 3, reference numeral 10 denotes a tap winding, and a plurality of taps N−1, N, N + 1... Are drawn from the tap winding 10. Each tap..., N−1, N, N + 1... Is connected to the main contact 12 and the resistance contact 13 of the switching switch 3 via the tap selector 2. Further, the current limiting resistor 4 is provided on the resistance contact 13 side.

  Such a switching circuit of the switching switch 3 operates as follows. First, A of FIG. 3 represents the driving state at the tap N. FIG. 3B shows a state in which the tap selector 2 has selected the next tap N + 1. Subsequently, in FIG. 3C, the resistance contact 13 is closed. At this time, the taps are bridged via the current limiting resistor 4, and the circulating current IC flows through the current limiting resistor 4.

  Next, in FIG. 3D, the main contact 12 is opened. At this time, since only the circuit on the resistance contact 13 side through the current limiting resistor 4 is provided, the load current IL flows through the current limiting resistor 4. In E of FIG. 3, the changeover switch 11 moves from the tap N to the tap N + 1 (the circuit is changed to the next tap). Finally, in FIG. 3F, the main contact 12 is closed. At this time, the resistance value of the current limiting resistor 4 in the circuit on the resistance contact 13 side is sufficiently larger than the energization resistance value on the main contact 12 side. Therefore, the load current IL flows through the circuit on the main contact 12 side, and does not flow on the current limiting resistor 4 side.

  The above switching operation is usually performed in a short time of several tens of ms. Therefore, even when the circulating current IC and the load current IL are supplied to the current limiting resistor 4, the energizing time to the current limiting resistor 4 is very short, and the temperature rise is limited to the range of the normal value. It will be. However, when the switching operation becomes slow or stops halfway, the energization time to the current limiting resistor 4 becomes long. As a result, the temperature rise of the current limiting resistor 4 exceeds a normal value, and the current limiting resistor 4 may be abnormally overheated.

  Further, when the resistance value itself of the current limiting resistor 4 changes due to some abnormality, the amount of heat generated by the current limiting resistor 4 changes. The change of the resistance value is related to the duty of opening and closing the main contact 12 and the resistance contact 13. That is, a change in resistance value may cause abnormal interruption, causing a failure. Therefore, a failure is detected in advance by measuring the temperature of the on-load tap changer (see Patent Document 1) in which only the current limiting resistor 4 is housed in an airtight container filled with liquid refrigerant, or the current limiting resistor 4. A load tap changer provided with an abnormality detection device has been proposed (see Patent Document 2).

  The prior art described in Patent Document 2 is characterized in that a temperature detector 16 that directly detects the temperature of the current limiting resistor 4 is installed in the on-load tap changer shown in FIG. That is, a temperature detector 16 is attached to the current limiting resistor 4, and this temperature detector 16 is connected to a temperature-light converter 18. The temperature-light converter 18 is connected to the power supply circuit 17. The power supply circuit 17 obtains a voltage from the output of the current transformer that detects the current of the load tap changer.

According to the prior art described in Patent Document 2, the temperature signal of the current limiting resistor 4 output from the temperature detector 16 is converted into an optical signal by the temperature-light converter 18, and the switching switch chamber 15 is converted. It is possible to detect in advance a fault of the current limiting resistor 4 by drawing it out to the outside and monitoring this.
JP-A-3-112112 JP-A-1-243818

  However, since the temperature detector 16 directly detects the temperature of the current limiting resistor 4 in the prior art of Patent Document 2, it is necessary to consider electrical insulation with respect to the temperature detector 16. The overall structure including the size of the system was increased. Moreover, since the current limiting resistor 4 is usually housed in the switching switch chamber 15 together with the switching switch 3, it is installed in a place where it is easily affected by heat generated in the other part energization path. Therefore, it has been pointed out that the signal detected from the temperature detector 16 makes it difficult to estimate an abnormal location or cause.

  The present invention has been proposed in order to solve the above-described problems, and its purpose is to store a current limiting resistor in a container filled with an insulating fluid and to detect the temperature difference between the insulating fluid flowing into and out of the container. By accurately detecting the amount of heat generated by the current limiting resistor based on the above, it is possible to simplify the configuration while minimizing consideration for electrical insulation, and the switching operation state of the switching switch during transformer operation Therefore, it is possible to provide an excellent on-load tap changer capable of accurately detecting a failure point of a switching switch and an abnormality sign due to the cause of the failure.

  In order to achieve the above object, the present invention provides a tap selector for a load comprising a tap selector for selecting a tap of a tap winding and a switching switch having a current limiting resistor. A temperature that is housed in a container filled with insulating fluid and configured to flow a constant flow of insulating fluid through the container, and detects a temperature difference between the insulating fluid flowing into the container and the insulating fluid flowing out of the container. A sensor is provided, and a diagnostic processing unit is provided for determining an abnormal state of the switching switch based on a detection result of the temperature sensor.

  In the present invention, the temperature difference of the insulating fluid flowing into and out of the container containing the current limiting resistor is detected by the temperature sensor, and the calorific value of the current limiting resistor is calculated from the following Equation 1 based on this temperature difference. After the calculation, the determination processing unit determines the abnormal state of the switching switch. That is, when the current I (A) flows through the current limiting resistor having the resistance value R (Ω), the heat generation amount W (W) becomes I2R as is well known. When this is cooled by the flow rate fluid Q (m3 / s), the temperature rise ΔT (K) that rises due to the heat taken from the current limiting resistor is as follows.

[Equation 1]
ΔT = (I2R × R) / (Cp × ρ × Q)
Here, Cp is the specific heat (J / kgK) of the insulating fluid at the inlet / outlet average temperature, and ρ is the density (kg / m 3) of the insulating fluid at the inlet / outlet average temperature.

  That is, if the flow rate Q of the insulating fluid flowing into the container and the temperature difference ΔT between the insulating fluid flowing into and out of the container are given, the calorific value of the current limiting resistor can be calculated from Equation 1. Then, based on the heat generation amount of the current limiting resistor at the normal time, the heat generation amount of the current limiting resistor generated at each tap switching can be compared to diagnose the presence or absence of abnormality. Furthermore, the state of the switching switch can be continuously monitored from the diagnosis result, and the sign of abnormality can be detected quickly and accurately.

  In addition, since the flow of the insulating fluid is generated during the switching operation, heat transfer is promoted and the temperature rise of the current limiting resistor can be suppressed, and a compact current limiting resistor can be selected. In addition, since the current limiting resistor, which is the heating element at the time of switching, and the heating element that is always energized are separated, it is easy to estimate the location and cause of the abnormality, the accuracy of abnormality sign detection is increased, and the reliability is improved.

  According to the on-load tap changer of the present invention, it is possible to monitor the state of the switching switch during operation without stopping the transformer. Abnormal signs can be accurately detected.

  Hereinafter, a typical embodiment according to the present invention will be specifically described with reference to FIG. FIG. 1 is a block diagram of an embodiment according to the present invention. The same parts as those in the prior art shown in FIG.

(Constitution)
As shown in FIG. 1, the current limiting resistor 4 is housed in a container 5 filled with an insulating fluid. An insulating tube 6 a for allowing an insulating fluid to flow in is provided at the upper part of the container 5, and an insulating tube 6 b for allowing an insulating fluid to flow out is provided at the lower part of the container 5. Pumps 8 are installed at the ends of these insulating pipes 6 a and 6 b so that a constant flow of insulating fluid always flows through the container 5.

  Furthermore, a temperature sensor 7 that detects a temperature difference between the insulating fluid flowing into the container 5 and the insulating fluid flowing out from the container 5 is installed in the insulating pipes 6a and 6b. The temperature sensor 7 is provided with a diagnostic processing unit 9 that determines the abnormal state of the switching switch 3 by determining the amount of heat generated by the current limiting resistor 4 based on the detection result of the temperature sensor 7. The diagnosis processing unit 9 is configured to draw out the determination result to the outside of the transformer tank 14 and monitor it to diagnose an abnormal state of the switching switch 3.

  In the diagnosis processing unit 9, the normal heat generation amount range in the current limiting resistor 4 is set in advance from the tap number, the load factor, etc., and the actual current limiting resistor calculated based on the detection result of the temperature sensor 7. When the heat generation amount of 4 does not fall within the range, or when the heat generation continues even after the switching operation, the switching switch 3 is diagnosed as abnormal.

(Function)
The operation of the present embodiment having the above configuration is as follows. That is, the switching signal enters the pump 8 as a command for flowing the insulating fluid through the electric operation mechanism 1. In response to this command, the pump 8 operates, the insulating fluid passes through the insulating tube 6a, enters the container 5, cools the current limiting resistor 4, and flows out of the insulating tube 6b. The temperature difference ΔT at this time is detected by the temperature sensor 7. And after calculating | requiring the detected temperature difference (DELTA) T and the flow volume Q of the insulating fluid which flows in into the container 5, the emitted-heat amount of the current limiting resistor 4 is calculated based on the said Numerical formula 1. FIG. The diagnosis processing unit 9 can determine the abnormal state of the switching switch 3 from the calculation result.

  In the diagnosis processing unit 9, when the calculated calorific value of the current limiting resistor 4 exceeds the normal calorific value range as compared with the normal calorific value range preset from the tap number, load factor, etc. It is determined that the switching operation is slow or that the resistance value may have changed, and the switching switch 3 is diagnosed as being in a state of caution.

  Further, when the calculated heat generation amount of the current limiting resistor 4 is smaller than the preset heat generation amount range, the load of the interrupting unit may be much smaller than normal or the resistance value may have changed. Determine and diagnose that the switching switch 3 is abnormal. Further, when the heat generation of the current limiting resistor 4 continues even after the switching operation, it is determined that the stop is intermediate, and this is also diagnosed as an abnormality of the switching switch 3.

(effect)
According to the on-load tap changer according to the above embodiment, the flow rate Q of the insulating fluid flowing into the container 5 and the temperature difference ΔT between the insulating fluid flowing into and out of the container 5 are obtained. By calculating the calorific value of the current limiting resistor 4 and comparing it with the calorific value of the current limiting resistor 4 in a normal state, it is possible to diagnose whether the switching switch 3 is abnormal. And it is possible to monitor the state of the switching switch 3 continuously from the diagnosis result, and to detect the sign of abnormality quickly and accurately.

  In addition, since the flow of the insulating fluid is generated during the switching operation, heat transfer is promoted and the temperature rise of the current limiting resistor 4 can be suppressed, and the compact current limiting resistor 4 can be selected. Moreover, since the temperature detector 16 for directly detecting the temperature of the current limiting resistor 4 is not provided as in the conventional example, there is no need to consider electrical insulation. Therefore, the configuration of the sensor system can be simplified, and the device can be easily made compact.

  Furthermore, in this embodiment, the amount of heat generated by the current limiting resistor 4 that is a heat generating element during the switching operation is calculated from the temperature difference ΔT at the inlet and outlet of the insulating fluid. It is possible to eliminate the influence from other part energization paths. Thereby, it is easy and reliable to estimate the location and cause of the abnormality in the switching switch 3, the accuracy of abnormality sign detection is increased, and the reliability of diagnosis is further improved.

(Other embodiments)
The present invention is not limited to the above embodiment, and the normal range of the heat generation amount of the current limiting resistor set in the diagnostic processing unit can be selected as appropriate, and the arrangement and configuration of each member Can also be changed freely.

The block diagram of typical embodiment which concerns on this invention. The block diagram of the conventional load tap changer. The circuit diagram which shows the switching operation | movement in the switching switch of the conventional load tap switch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric operation mechanism 2 ... Tap selector 3 ... Switching switch 4 ... Current limiting resistor 5 ... Container 6a, 6b ... Insulating tube 7 ... Temperature sensor 8 ... Pump 9 ... Diagnosis processing part 10 ... Tap winding 11 ... Tap Selector 12 ... main contact 13 ... resistive contact 14 ... current limiting resistor 15 ... switch switch room 16 ... temperature detector 17 ... power supply circuit 18 ... temperature-light converter IL ... load current IC ... circulating current

Claims (2)

In a load tap changer consisting of a tap selector for selecting a tap of a tap winding and a switching switch having a current limiting resistor,
Storing the current limiting resistor in a container filled with an insulating fluid;
Configured to flow a constant flow of insulating fluid through the container;
Installing a temperature sensor for detecting a temperature difference between the insulating fluid flowing into the container and the insulating fluid flowing out from the container;
An on-load tap changer comprising a diagnostic processing unit for determining an abnormal state of the switching switch based on a detection result of the temperature sensor.   The diagnostic processing unit calculates a heat generation amount of the current limiting resistor based on a detection result of the temperature sensor, and sets a normal heat generation amount range in the current limiting resistor in advance. 2. The on-load tap changer according to claim 1, wherein the heat generation amount of the resistor is compared with a set normal heat generation amount range to diagnose an abnormality of the switching switch.

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