JPS6015282Y2 - winding protection device - Google Patents

Description

[Detailed description of the invention] This invention relates to a winding protection device, and in particular, to protect the winding of a transformer or reactor from lightning impulse voltage or alternating current overvoltage. This invention relates to a winding protection device that allows the life deterioration of a non-linear resistor housed in a device to be monitored from outside the outer box.

An overvoltage higher than the normal operating voltage may be applied to a transformer or reactor used for electric power due to a lightning strike or circuit failure.

In particular, when a lightning impulse voltage is applied, a significant overvoltage is induced in a portion of the winding near the line end or a portion of the winding that has a tap.

When manufacturing transformers and accelerators, keep this in mind and create structures that can withstand overvoltage, for example by increasing the insulation thickness of the conductor at the end of the winding line, or by increasing the size of the insulation oil gap. I'm trying to do it.

However, this method has the disadvantage of increasing the dimensions of the transformer winding.

On the other hand, in order to suppress the overvoltage induced in the winding, a nonlinear resistor such as a zinc oxide resistor that responds to the magnitude of the voltage is connected to at least a part of the winding, so that the resistance value increases when overvoltage occurs. Structures that are small and suppress the voltage across the resistor may be used.

This nonlinear resistor generates heat due to the current flowing through the resistor, so it suffers thermal deterioration under constant voltage application, gradually increases the current, and may eventually cause thermal runaway and break down.

For this reason, it is desirable to periodically monitor the characteristics of the nonlinear resistor, but in conventional structures of this type, if the nonlinear resistor is housed inside the outer box of the transformer or reactor, it is difficult to monitor it from the outside. There was a drawback that the characteristics of the resistor could not be easily monitored.

This idea was made in view of the above points.The nonlinear resistor is housed inside an insulating cylinder, and a fixed contact is provided on the insulation circumferential side and a movable contact on the resistor side. The present invention provides a winding protection device in which the characteristics of the resistor can be monitored from outside the outer box by rotating the terminal and bringing it into contact with a fixed contact for measuring the electrical characteristics of the resistor.

FIG. 1 shows the schematic structure of this type of winding protection device, in which an iron core 2 and a winding 3 are housed inside an outer box 1, and the line end of the winding 3 is connected to a power transmission line through a high-voltage bushing 4. It is connected to the.

The non-linear resistor is housed inside the insulating tube 5 and mounted on the mounting plate 6.
is attached to.

The details of the inside of the insulating cylinder 5 will be explained with reference to FIGS. 2 to 4. The nonlinear resistor 11 has movable contacts 12 and 13 at both ends thereof, and is electrically connected in series with the resistor 11.

This resistor group is fixed to a rotating shaft 15 via an insulating rod 14, and has a structure in which it can be rotated circumferentially by gears 16 and 17 and a handle 18.

A seal 19 connects the outer box 1 between the mounting plate 6 and the rotating shaft 15.
Keeps the inside sealed.

Further, an insulating tube 25 and a stopper 26 are provided at the bottom of the resistor 11 to prevent lateral vibration during rotation.

First fixed contacts 7 and 8 (FIGS. 1, 2, and 4) and second fixed contacts 23 and 24 (FIGS. 3 and 4) are attached to the insulating cylinder 5. ing.

The first fixed contacts 7 and 8 are connected to a part of the winding 3 by connecting leads 9 and 10, respectively, and the second fixed contacts 23 and 24 are connected to the housing 22 by connecting leads 27 and 28, respectively. terminals 20 and 2 attached to
1 is connected.

FIG. 5 shows a side view of the third housing 22.

In the above configuration, when the transformer or reactor is in normal operation, the fixed contacts 12 and 13 are in contact with the first fixed contacts 7 and 8, respectively, and the resistor 11 is connected to the winding. At least some of them are connected in parallel.

FIG. 7 shows the voltage-current characteristics of the resistor 11, with the horizontal axis representing the current I and the vertical axis representing the voltage V.

In the unlikely event that an overvoltage higher than voltage Np enters the transformer or reactor due to a lightning strike or failure of the power transmission line, the current flowing through the resistor 11 due to the overvoltage induced inside the winding will increase rapidly as shown in Figure 7. However, the impedance of the winding portion connected in parallel with the resistor 11 is lowered, and overvoltage is suppressed.

However, since the resistor 11 is always connected to at least a part of the winding even during normal operation, voltage is always applied, and the current flowing through the resistor 11 generates heat and causes thermal deterioration. This may eventually lead to thermal runaway and destruction.

Therefore, in order to monitor the lifespan of the resistor, the movable contacts 12 and 13 are connected to the fixed contacts 23 and 24 by operating the handle 18 and rotating the rotating shaft while the transformer or reactor is not energized. bring into contact.

Then, an AC or DC power source, an ammeter, and a voltmeter are connected to the external terminals 20 and 21 as shown in FIG. 6, and the voltage-current characteristics of the resistor 11 are measured by changing the power supply voltage.

For example, by measuring whether the voltage when a current of 1 mA flows has changed from the initial value of the resistor 1,
1 can be monitored.

In short, this invention makes it possible to easily monitor the lifespan of a nonlinear resistor used to protect the windings of a transformer or reactor by externally measuring the characteristics of the resistor, for example during periodic inspections. The present invention provides a device as described above, which eliminates the drawback that maintenance and inspection of the resistor is difficult due to the conventional use of the resistor in a sealed outer box.

In the above description, the connection of the circuit is switched by rotating the movable contact, but it is of course possible to switch the connection by moving the movable contact up and down.

Further, it is preferable that the terminals 20 and 21 are respectively grounded during normal operation to prevent them from becoming floating electrodes that may cause partial discharge.

As described above, this invention makes it possible to easily monitor the characteristics of a nonlinear resistor from the outside when the nonlinear resistor is housed inside the outer box of a transformer or reactor. It has the effect of improving reliability when using the resistor, and also provides economic advantages such as eliminating the complicated work of taking the resistor outside for maintenance and inspection, making it easier to use the resistor.

[Brief explanation of the drawing]

Figure 1 is a structural diagram of a transformer or reactor, Figure 2 is a vertical sectional view of an insulating cylinder housing a nonlinear resistor according to this invention, Figure 3 is a side sectional view of Figure 2, and Figure 4 is a Figure 2 is a horizontal sectional view, Figure 5 is a partial side view of Figure 3, Figure 6 is a circuit diagram for measuring the deterioration characteristics of a non-linear resistor, and Figure 7 is a non-linear resistor. FIG. 2 is a graph diagram showing an example of voltage-current characteristics of FIG. In the figure, 1 is an outer box, 3 is a winding, 5 is an insulating cylinder, 7 and 8 are first fixed contacts, 11 is a non-linear resistor, 12
and 13 are movable contacts, 15 is a rotating shaft, 18 is a handle, 20 and 21 are terminals, and 23 and 24 are second fixed contacts.

Claims (1)

[Scope of utility model registration request] A winding protection device in which a winding and a non-linear resistor connected in parallel to at least a portion of the winding are hermetically housed in an outer box to protect the winding when overvoltage is applied. , a pair of movable contacts arranged and connected in series to both ends of the non-linear resistor, an insulating tube that accommodates the non-linear resistor in the outer box, and A pair of first fixed contacts provided on the side wall of the insulating tube for parallel connection with at least a portion of the wire, and a pair of terminals also provided on the side wall of the insulating tube and communicating with the outside of the outer box. and a pair of second fixed contacts connected to each other, and during normal operation of the winding, each of the pair of movable contacts is brought into contact with the pair of first fixed contacts, and the non-linearity When monitoring deterioration of the resistor, the pair of movable contacts are moved so that each of the pair of movable contacts contacts the second fixed contact of the pair, and the pair of movable contacts are moved from the pair of terminals of the outer box to the non-linear line. A winding protection device characterized in that it measures the deterioration characteristics of a magnetic resistor.