JPS5836486B2 - Regulation transformer shock voltage protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a regulating transformer having an on-load tap changer.
The present invention relates to an impact voltage protection device used for protection against impact voltages.

In on-load tap-changing devices and at least regulating transformers with tap windings, large impulse voltages can be generated between a selected tap and a previously selected tap in the tap winding if an impulse voltage enters from the line. appears.

Not only the windings but also the on-load tap changer must withstand this voltage.

It is also possible to reduce the said impulse voltage fraction appearing in the tap winding by a suitable formation of the winding, for example by adding a resistance when the voltage rises between the selected tap and the previously selected tap of the tap winding. Simply installing voltage suppression means, such as voltage-dependent resistors whose values drop significantly, often brings the impulse voltage burden of the tap winding and connected on-load tap changer within economically acceptable limits. has been successfully suppressed.

Each leg or each phase (hereinafter referred to as each phase) of a large current transformer
The windings are often divided into multiple parallel electrically isolated branches.

Due to impulse voltage limitations, previously a voltage dependent resistor had to be provided for each branch between the selected tap and the previously selected tap.

That is, for example, if the winding is divided into two parallel branches for each phase, a total of six voltage-dependent resistors must be installed in a three-phase regulating transformer with an on-load tap changer.

Voltage-dependent resistors usually consist of a stack of about 10 to 20 individual resistor strips, which are pressed together by spring bodies and fixed in a holder, with which they can be directly connected to an on-load tap changer. can be attached to.

The individual resistor pieces are made from a powdered voltage-dependent material obtained by a special method, pressed into a predetermined shape and sintered at high temperatures.

Resistance pieces made from such materials have the characteristic that their resistance value decreases significantly when the voltage increases.
Thereby, potential rise can be suppressed.

In the case of a transformer having multiple parallel divided branches for each intervening phase, the cost of the resistor pieces themselves stacked to form the laminate, as well as the cost of fixing and assembling them, becomes considerably large; Moreover, the space for mounting the stack on the on-load tap changer is limited.

The present invention minimizes as much as possible the shock voltage protection devices necessary in transformers with multiple parallel electrically isolated branches, but whose dimensions are relatively large and economically expensive, thereby making it possible to The purpose is to reduce the number of resistor strips that are stacked on top of each other by means of special structures and connections, in order to allow them to be installed without taking up space.

According to the invention, each leg is also electrically isolated for each phase and has n parallel branch windings each having a tapped winding. In the case where an on-load tap changer is connected to each,
A resistor consisting of a laminate of voltage-dependent resistor pieces whose resistance value decreases significantly when the voltage increases, and a resistor consisting of the voltage-dependent resistor pieces or a laminate thereof connected in series to both ends of this resistor (n- 1) form a series resistor with additional resistors, and 10,000 (n-1) of the additional resistors are selected by the on-load tap changer of the n parallel branch windings; The other (n-1) additional resistors are connected between the taps selected by the on-load tap changer and adjacent taps of the n parallel branch windings. This can be achieved by

Circulation caused by the slight difference in impedance of the winding between the two taps in the closed circuit constructed between the selected tap of the parallel branch winding connected by this additional resistor and the previously selected tap Current can be suppressed.

The length of the series resistor is increased by the arrangement of additional resistors, for example in the already mentioned regulated three-phase AC transformer with split windings in two parallel, electrically isolated branches for each phase. In this case, a total of six resistor pieces were required in this case, but now only three laminates consisting of resistor pieces are required.

A new shock voltage protector made from a small number of laminates
In particular, it is installed above or below the selector of the on-load tap changer so as to be located directly within the range of the connection conductor of the selector, and is connected to the connection conductor.

The impact voltage protection device according to the present invention will be explained in more detail with reference to the drawings.

The drawing shows a single-phase winding of a regulating transformer with on-load tap changer, in this case two electrically separated windings (n=
2) is divided into parallel current branches.

Tap windings 1, 1 with taps, change-over contacts 2, 2' of the on-load tap changer and taps 4, 3 and it/, 3
It is connected at /.

Now, the upper switching contacts 2, 2 are in contact with the taps 4, 4' and current is being supplied to the load from the tap windings 1, 1', and the lower switching contacts 2, 2 are now in contact with the taps 4, 4'. It is assumed that the connection is made from the upper tap in the figure to taps 3 and 3.

At this time, a resistance value increases when the voltage increases between the selected tap 3' and the previously selected tap 4, which are located diagonally in both electrically separated parallel current branches of the tap windings 1, 1. Since the voltage-dependent resistor strip laminate 5 is connected, in which the voltage is significantly reduced, a rise in potential can be suppressed even if an impact voltage enters.

Furthermore, a switching switch (not shown) installed in the electrical path through which current flows from the taps 4, 4 through the upper contacts 2, 2 is opened, and current flows from the taps 3, 3 through the lower contacts 2, 2. A switching switch (not shown) provided in the electric line closes the circuit, and power is supplied to the load via this electric line.

One additional resistor 6 and 6 are connected to both ends of the laminate 5! Both ends of these resistors 6, 6 are connected to tap winding 1, respectively.
, 1 to the selected taps 3 and 3 (and the previously selected taps 4 and 4) and between the selected tap and the previously selected tap of each parallel winding as described above. Circulating current caused by a slight difference in impedance between the windings between both taps is suppressed in the closed circuit constructed as follows.

The circuit structure of this shock voltage protection device saves three stacks of resistor strips, which preserves the protection effect against shock voltages in the housing, and also reduces the overall cost of the device.

In this example, IrJ. Although the case of (n=2), that is, two parallel branch windings has been shown, the following procedure can also be performed for the case of three parallel branch windings, that is, (n=3).

That is, additional resistors similar to the additional resistors 6 and 6 are inserted in series between the button 6 and 5 and between the button 6' and 5, respectively, and this additional resistor is connected to the third parallel resistor. The taps of the branch windings may be connected, for example, between 3'' and 3' or between 4'' and 4'.

By doing so, the resistor 5 can be shared.

[Brief explanation of drawings]

The white page of the figure is a connection diagram of one embodiment of the present invention. 1, 1'...Tap winding, 2,2'-...Switching contact of tap changer on load, 3,3',4,4'...Tap, 5...Laminated body of resistor pieces , 6, 6'...additional resistor.

Claims (1)

[Claims] 1 Each leg or each phase is electrically separated and has n parallel branch windings each having a tap winding, and each of these parallel branch windings is connected to an on-load tap changer. In this case, a resistor consisting of a laminate of voltage-dependent resistor pieces whose resistance value decreases significantly when the voltage increases, and a resistor made of a laminate of voltage-dependent resistor pieces or the laminate thereof connected in series to both ends of this resistor, respectively. Become (n-1)
10,000 (n-1) additional resistors form a series resistor, and the 10,000 (n-1) additional resistors are connected between the taps selected by the on-load tap changer of the n parallel branch windings. and the other (n-1) of the additional resistors are connected between the tap selected by the on-load tap changer and the adjacent tap of the n parallel branch windings. An impact voltage protection device for a regulating transformer, characterized in that: