JPH10270266A - On-load tap switcher - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress uneven consumption of a contactor of a switching open/ close device by changing a resistance value of a limited current resistance of an on-load tap switcher. SOLUTION: Sensors 2, 3 and 4 detecting temperature change due to the fluctuations of a load of a transformer are provided, and a resistance value of limited current resistor Ra and Rb used for suppressing inter-tap short circuit current in a tap switching process of a switching open/close device DS can be changed with measurement values of the sensors 2, 3 and 4 and a judgement circuit 5. Thereby the amount of consumption of main contactors Ha and Hb and resistant contactors Wa and Wb of the switching open/close device DS are made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a current limiting resistance of a load tap changer which prevents uneven contact wear of a switching switch contact of the load tap changer.

[0002]

2. Description of the Related Art An on-load tap changer is a device that can change taps during operation of a transformer. At the time of tap change, a current tap and an adjacent tap are bridged via a current limiting resistor. The taps are switched by a switching switch. In this tap switching process, a current-limiting resistor used to suppress a short-circuit current generated in a state where a current tap and an adjacent tap are bridged, that is, in a bridging state between taps, generally has a current-limiting resistance during the load. In the specification of the voltage value between the adjacent taps of the in-phase winding and the maximum current value flowing to the external circuit through the load tap changer of the transformer in which the tap changer is mounted, the load change tap request is required. ,
A resistance value that satisfies the electrical switching capability is selected.

[0003] This conventional apparatus will be described with reference to FIG. DS is a switching switch provided with main contacts Ha, Hb and resistance contacts Wa, Wb for current switching, and TS selects taps T1 to Tn drawn from tap winding 1 of a transformer.
It is a tap selector to connect. The tap selector TS includes a plurality of taps T1 to Tn drawn from the tap winding 1.
The contact TSb of the tap selector TS is connected to a tap position corresponding to the load condition of the transformer, and a tap adjacent to the currently connected tap for performing tap switching during operation of the transformer is connected to the tap TS. The other contact T of the tap selector TS
Sa is connected. The contacts TSa and TSb of these tap selectors TS are respectively connected to main contacts Ha and Hb for switching the current of the switching switch DS. From the intermediate position where the contacts TSa and TSb of the tap selector TS and the main contacts Ha and Hb of the switching switch DS are connected, the resistance contact Wa of the switching switch DS is connected via current limiting resistors Ra and Rb. , Wb.

The operation sequence of the circuit thus configured will be described with reference to the sequence diagrams of FIGS. The main contact Ha is on or closed, and is connected to the tap T2 to operate the transformer. First, the resistance contact Wa is closed, and the load current is changed to the main contact Ha, the resistance contact Wa, and the current limiting resistance Ra.
And flows through. Next, the main contact Ha is turned off or opened, and the load current flows through the resistance contact Wa and the current limiting resistor Ra. Next, the resistance contact Wb is closed, a bridge state is established between the tap T2 and the tap T3, and a short-circuit current flows. Next, the resistive contact Wa opens, then the main contact Hb closes, and the load current moves to the tap T3. Next, the resistance contact Wb opens,
The switching operation for one tap is completed. As described above, the on-load tap changer performs the tap change while the transformer is in operation, so that the main contacts Ha and Hb are in resistance contact with the main contacts Ha and Hb during the tap change process so that the transformer does not open. Child W
The switching operation is performed by opening and closing a and Wb so as to overlap each other.

[0005]

The problem with the on-load tap changer in the prior art is that the tap change process during the tap change process is difficult.
The value of the current-limiting resistor used to suppress the short-circuit current that occurs when the current tap and the adjacent tap are bridged, that is, when the tap is bridged, is transformed by the transformer with the on-load tap changer attached. Of the voltage between the adjacent taps of the in-phase winding and the maximum current flowing to the external circuit through the on-load tap changer, the required electrical switching capacity of the on-load tap changer However, if the transformer equipped with the on-load tap changer is operated for a long period of time at light load, the current of the changeover switch DS is changed at the time of tap change. The current value I interrupted by the main contacts Ha and Hb is given by I = IL, where IL is the load current value at the time of tap switching. As the load current value IL decreases, the transformer is operated with a light load. The main contact Ha, Hb is decreased the current value I to block, main contactor ha, whereas decreases consumption of Hb, resistance contact Wa of diverter switch DS, W
The current value I cut off by b is I = (IL / 2) ± Ic, where IL is the load current value at the time of tap switching and Ic is the short-circuit current value at the time of bridging between taps. The sign of Ic means that the short-circuit current value Ic and the load current IL are in the direction of the sum or difference. The short-circuit current value Ic is given by Ic = Vs / (2 × R), where Vs is the voltage value between adjacent taps of the in-phase winding of the transformer and R is the current-limiting resistance value. From the above description, the breaking current value I of the resistance contacts Wa and Wb is determined by the load current value IL when the transformer is operated under a light load.
The short-circuit current value Ic does not change even if the voltage decreases, and the decrease value of the breaking current value I of the resistive contacts Wa and Wb with respect to the decreasing value of the breaking current value I of the main contacts Ha and Hb depends on the load of the transformer. The load current value during operation is Iheavy, the load current value during light load operation of the transformer is Ilight, the short-circuit current value during bridging between taps is Ic, and the main contacts Ha, Hb and the resistance contacts Wa, Wb. The difference in the breaking current value between the heavy load operation and the light load operation, that is, the decrease value during the heavy load operation and the light load operation is IH,
Assuming that IW, IH = Iheavy-Ilight IW = {(Iheavy / 2) ± Ic} − {(Ilight / 2) ± Ic} = (Iheavy−Ilight) / 2, and tap switching in the transformer light load operation state The cut-off current reduction value IW of the resistive contacts Wa and Wb at the time is the main contact H
Since the cut-off current reduction values IH of a and Hb are １ ／, the amounts of consumption of the main contacts Ha or Hb and the resistance contacts Wa or Wb become uneven, and FIG. As shown in the figure, the predetermined switching sequence cannot be satisfied, that is, in the tap switching process, the main contacts Ha, Hb and the resistive contacts Wa, Wb do not overlap with each other. A power outage occurs.

In the present invention, the operating condition of a transformer equipped with a load tap changer is detected, and the non-uniform consumption of the main contact and the resistance contact of the changeover switch in the tap change is suppressed, thereby improving the efficiency. An object of the present invention is to provide a load tap changer that can be operated well.

[0007]

In the load tap changer according to the present invention, a sensor for detecting a temperature change due to a change in transformer load at the time of tap change is provided, and a short-circuit current between taps in a tap change process of the changeover switch is provided. The structure is such that the resistance value of the current limiting resistor used for suppression can be changed according to the measurement value of the sensor, so that the contact wear of the switching switch is made uniform.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of the present invention, showing a switching switch DS having main contacts Ha, Hb and resistance contacts Wa, Wb for current switching, and taps drawn from a tap winding 1 of a transformer. In the on-load tap changer constituted by a tap selector TS for selecting and connecting T1 to Tn, the tap changer TS is connected to a plurality of taps T1 to Tn drawn from the tap winding 1 to load the transformer. The contact TSb of the tap selector TS is connected to the corresponding tap position, and the other contact of the tap selector TS is connected to the tap adjacent to the currently connected tap to perform tap switching during operation of the transformer. TSa is connected.
The contacts TSa and TSb of these tap selectors TS are used as main contacts Ha and Hb for switching the current of the switching switch DS.
Connected to each other. Further, the contacts TSa and TSb of the tap selector TS and the main contacts Ha and
From the intermediate position where Hb is connected, the limiting current source resistance Ra,
A circuit is provided for connection to the resistance contacts Wa, Wb of the switching switch DS via Rb, and a switch 6 is provided so that the resistance values of the current limiting resistors Ra, Rb can be changed.
b is a two-stage structure such as Ra1, Ra2 and Rb1, Rb2. And a sensor 2 attached at an arbitrary line end position to measure the conductor temperature, a sensor 3 attached inside the transformer to measure the insulating oil temperature in the transformer,
A sensor 4 is provided outside the transformer to measure the outside air temperature. A determination circuit 5 for operating the switch 6 based on the values measured by these sensors 2, 3, 4 is provided between the sensors 2, 3, 4 and the switch 6. Further, in order to detect the operation of the on-load tap changer, a strain sensor 7 for detecting a distortion generated in the power transmission section is provided at an arbitrary position of the power transmission section of the on-load tap changer.

Next, the operation of the present invention will be described with reference to the block diagrams of FIG. 1, FIG. 3 and FIG. The data of the temperature change due to the transformer load fluctuation measured by the sensors 2, 3, and 4 and the temperature change due to the transformer ambient environment change are input to the input unit 11 of the judgment circuit 5, and the calculation unit 12 of the judgment circuit 5 outputs the data to the transformer load. Calculate the transformer load factor by comparing the oil temperature change with respect to the conductor temperature change due to fluctuations and the oil temperature change with respect to the outside air temperature change. The optimum current-limiting resistance value when tap switching is performed in the state of the transformer load ratio Is compared with the current-limiting resistance value by the determination unit 13 of the determination circuit 5,
When it is not necessary to change the current limiting resistance, that is, in a state where the contacts Ha, Hb and Wa, Wb of the switching switch DS are evenly consumed, for example, when the transformer is operated under heavy load, the current limiting resistance is small (Ra1). , Rb1), the current limiting resistance is large when the transformer is in heavy load operation (Ra1 + Ra2, Rb1 + Rb).
2) In the case of the state, the process returns to the input unit 11 to be in a state of waiting for input of new transformer load current data. Further, when it is necessary to change the current limiting resistance, that is, in a state where the contacts Ha, Hb and Wa, Wb of the switching switch DS are not evenly consumed, for example, when the transformer has a large current limiting resistance during heavy load operation ( Ra1 + Ra2, Rb1 + Rb2), and when the transformer is in a state of low current limiting resistance (Ra1, Rb1) during light load operation, distortion is detected by the distortion sensor 7 provided in the power transmission section of the on-load tap changer. The determination unit 14 of the determination circuit 5 determines whether or not the load tap changer operates, and changes the current-limiting resistance value when the load tap changer operates, that is, when the load tap changer is operating. Switch 6
When the operation of the switch and the tap switching of the switching switch DS are simultaneously performed,
Since there is a possibility that the transformer is opened during the operation of the switch 6, the operation returns to the input unit 11 without performing the operation of the switch 6, and the apparatus enters a data input standby state of a new temperature change. Further, when the on-load tap changer does not operate, that is, when the on-load tap changer is stopped, the switch 6 operates according to the instruction of the determination circuit 5, and the resistance values of the current limiting resistors Ra and Rb are Ra1 respectively. , Rb1 to Ra1 + Ra2, Rb1 + Rb2 or Ra1 + Ra2, Rb1 + Rb2 to Ra1, R
It is changed to b1. After performing the above operations, FIG.
Is performed, and the one-tap switching operation is completed.

[0010]

As described above, the on-load tap changer of the present invention can change the resistance values of the current limiting resistors Ra and Rb in accordance with the transformer load condition at the time of tap change. , It is possible to adjust the short-circuit current generated at the time of bridging between taps in the tap switching process, and the switching switch DS
By suppressing uneven wear of the main contacts Ha and Hb and the resistance contacts Wa and Wb, the on-load tap changer can be operated efficiently.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a load tap changer of the present invention.

FIG. 2 is a block diagram showing an embodiment of a determination circuit used to change the current limiting resistance of the on-load tap changer of the present invention.

FIG. 3 is a sequence diagram showing the operation of the on-load tap changer.

FIG. 4 is a circuit configuration diagram of a conventional on-load tap changer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transformer tap winding 2, 3, 4 Sensor 5 Judgment circuit 6 Resistance changeover switch 7 Power transmission unit distortion sensor DS switching switch TS Tap selector Ha, Hb Main contact Wa, Wb Resistance contact TS1, TS2 Contact Ra1, Ra2, Rb1, Rb2, Ra, Rb Current-limiting resistors T1, T2, T3, Tn Transformer tap winding taps

Claims (1)

[Claims] 1. A load tap changer having a switching switch for interrupting a transformer load current and performing tap change,
A sensor for detecting a temperature change due to a transformer load change at the time of tap switching is provided, and a resistance value of a current limiting resistor used for preventing a short circuit between taps in a tap switching process of the switching switch,
The load tap changer according to claim 1, wherein the changeover switch has a structure that can be varied according to the measurement value of the sensor, so that the contact wear of the changeover switch becomes uniform.