JPS58175813A - On-load tap changer - Google Patents

Abstract

PURPOSE:To equalize the consumption of an arc contact by using a variable resistor as a current-limiting one and adjusting resistance value in response to load currents. CONSTITUTION:Taps T1, T2, T3 set up into tap winding are mounted to the primary winding PW of a transformer. The on-load tap changer 1 is connected to the taps, and constituted by a tap selector 2 and a changeover switch 3. The changeover switch 3 has main contacts A (for the even taps) and D (for odd taps) and resistance contacts B, C connected to the variable type current-limiting resistors R. An arithmetical processor 5 emits commands changing the variable resistance of the current-limiting resistors in response to the magnitude of currents IL detected by a current transformer 4. A driving device 6 responds to the commands from the arithmetical processor 5, and changes variable resistance value. A variable resistor 7 is driven by the driving device, has the same value as the variable resistance value of the current-limiting resistors R, and is fed back to the arithmetical processor.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to improvements in on-load tap changers used in on-load tag switching transformers.

[Technical background of the invention]

In recent years, in order to increase electricity demand and improve the quality of electricity,
On-load tap change transformers are used regardless of power generation or substations. Conventional load ta, which is applied to these transformers! Resistive load switching devices are most popular because they have high performance, long life, and can be manufactured at relatively low cost.

This resistance type is a well-known method that adds resistance to the current-limiting impedance required to suppress the circulating current that flows when the tags are bridged during tag switching to within the arc extinguishing ability of the arc contact of the Tatsuzo switch when loaded. It has nine uses. The resistance value of this resistor is selected so that the interruption responsibility of the plurality of arcing contacts is kept within the interruption capability of each contact, and at the same time, so that the wear of each arcing contact is uniform. selected as the value.

[Problems with background technology] - However, in the conventional on-load tap changer,
Because a fixed resistor was used as the current limiting resistor, only one arbitrary point could satisfy the above conditions.1For example, 100
If the resistance value is determined so that the valley arc contact wears out uniformly under the ts load condition, when the load decreases, the resistance contact that depends on the galvanic current at the time of bridging between tags will wear out first, and conversely, the load will decrease. If the load current increases, the main contacts, which depend on the load current, will wear out in advance.If operating under such conditions, there will naturally be a difference in wear between the main and resistance contacts, resulting in an imbalance, and the conventional load When switching time tags, there were the following problems.

(1) Changes occur in the switching time between each contact, and in the region where the resistive contacts wear out in advance, the time between the resistive contacts is shortened. As a result, there was a possibility of a short circuit between T and F, which could lead to a serious accident.

(2) On the other hand, in the case where the main contact wears out in advance, the switching time of the resistance contact is extended, resulting in a longer energization time of the current limiting resistor, which may cause the resistance m (band) to melt.
As with item (1) above, there was a risk of causing a serious accident.

(3) In order to prevent items (1) and (2) above, K is
It was necessary to periodically conduct internal inspections and measure the state of wear and tear on each contact, which required maintenance costs.

(4) When unbalanced wear occurs, it becomes necessary to replace each contact before the wear limit is reached, which is a factor that requires maintenance costs as in the above item (3).

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an on-load tap changer that solves the problems of the prior art described above and can evenly wear out the arc contacts.

[Summary of the invention]

For this reason, the present invention is characterized in that a variable resistor is used as the current limiting resistor, and the resistance value is adjusted by spreading it to the load current at that time.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In Fig. 1, sw indicates the primary and secondary windings of the transformer, and TI, T, and Ts indicate the tags of the tapped Itk wires provided in the above-mentioned and secondary windings. 1 is the tag winding. This is an on-load tap changer connected to the tag, and is composed of a tap selector 2 and a switching switch 3. The switching switch 3 has main contacts large (for even tags) and D (for odd tags and f), and resistance contacts B and C connected to a variable current limiting resistor RVc.
, and are connected through each other as shown in the figure. 4 is a current transformer that detects the current of the transformer-secondary winding. P indicates a power supply, 5 indicates a processing unit, which issues a command to change the variable resistance of the current limiting resistor according to the magnitude of the current IL detected by the current transformer 4; 6 indicates the processing unit 5; This drive device changes the variable resistance value in response to a command, and is connected to the variable current limiting resistor R via an insulated shaft. A variable resistor 7 is driven by the driving device 6, has the same variable resistance value as the current limiting resistor R, and is fed back to the arithmetic processing device 5.

With the above configuration, as shown in the flowchart of FIG. 2, first, the load current IL of the transformer's next winding is detected by the current transformer 4 and input to the arithmetic processing unit 5. Depending on this input value, the processing unit 5 calculates the load current IL and the cross current (2) that flows through the variable current limiting resistor R when there is a bridge between the taps. A target resistance value R. that makes the interruption responsibility uniform for each resistance contact is calculated. Next, input the value of the variable resistor 7 and check whether the resistance value R' of the variable current limiting resistor R is equal to the target resistance value R, and if it is set properly, finish the calculation geography. do. On the other hand, if they are not equal, the resistance value R' of the variable current limiting resistor R and the target resistance value R.

Also, when R' (R), an increase command is output to the drive device 6. According to these commands, the drive device 6 changes the resistance values of the variable current limiting resistor R and the variable resistor 7 to reach the target resistance. By matching the value R, the command from the arithmetic processing device 5 is made to be f.

By adjusting the resistance value R' of the variable current limiting resistor R in this way, the following advantages and disadvantages can be obtained.

(1) As a result of uniform interruption duties of the main and resistive contacts, contact wear becomes uniform and a substantially constant switching time is obtained.

Therefore, performance equivalent to that at the time of shipment can always be maintained.

(2) Periodic inspections mainly involve inspections of other mechanical parts, so
The inspection cycle will be extended. Furthermore, since there is no need to replace contacts regardless of load conditions, maintenance costs are greatly reduced.

(3) Since the transformer can always be operated in a state of uniform consumption, highly reliable tap switching is performed under load.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an on-load tap changer that saves each arcing contact.

[Brief explanation of drawings]

Fig. 1 is a wiring diagram showing one embodiment of the present invention, and Fig. 2 is a wiring diagram showing an embodiment of the present invention.
It is a flowchart for explaining the operation of the figure. 1...Tag switcher on load, 2-Tap selector, 3
... switching switch, 4... current transformer, 5... arithmetic processing unit, 6... drive device, 7... movable resistor. Figure 1 wsw

Claims (1)

[Claims] In an on-load tap changer using a current limiting resistor as the current limiting impedance at the time of bridging between taps, a detection device that makes the current limiting resistor variable and detects one load current, and a detection device that detects one load current according to the detection output. A load tap characterized by being provided with an arithmetic processing device that performs a calculation to equalize the consumption of each arc contact, and a drive device that changes the resistance value of the current limiting resistor that has the variable voltage based on the result of the calculation. Switch.