JPS6240022A - Testing transformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a test transformer.

(Prior Art) As is well known, a test transformer is used to transform a power supply voltage to obtain a test voltage to be applied to a load to be tested. Therefore, the secondary side of the transformer body constituting the test transformer is normally used while being connected to the load to be tested.

By the way, conventionally, the secondary side of the transformer main body is directly connected to the load. But if you do it this way,
During the test process, if a flash fault occurs on the load side for some reason, a sudden surge voltage may occur, which may directly enter the transformer body. If such a surge voltage enters, there is a risk that a voltage exceeding the allowable insulation strength will be applied to the insulating layer of the high voltage coil.

It is possible to use a resistor to suppress surge voltage, but this resistor should be 2 times the capacity of the transformer itself.
It is necessary to use one with a capacity of about 5%.

For example, for a 500KVA transformer, 10 to 25Kl
It is necessary to use an il resistor.

However, such a resistor generates a large amount of heat due to the load current under normal conditions, and if it is made into a gas-sealed type, a considerably large volume is required to dissipate the generated heat, making it large and expensive. Become.

(Problems to be Solved by the Invention) This invention aims to reduce the size of the resistor even when the main body of the transformer is protected by a resistor against the surge voltage generated from the load side during the test. The purpose is to make it possible.

(Means for Solving the Problems) This invention involves connecting a protection device consisting of a resistor and an inductance element connected in parallel between the secondary side of the transformer body and the load to be tested. Features.

According to this, the load current flows through the inductance element during steady state, so the resistor does not generate heat. When a steep surge voltage occurs on the load side, the inductance component of the inductance element becomes large, so the resistor shares part of the surge voltage and suppresses the wavefront steepness. The resistor only needs to be small because it shares part of the voltage only when a surge occurs.

(Example) An example of the present invention will be described with reference to the drawings. FIG. 5 shows the entire embodiment of the present invention, and 1 is a transformer body housed in a container 2, which is SF.

A gas insulated transformer is used by filling it with an insulating gas such as gas. 3 is an insulating spacer mounting container, 4, 5
is an insulating spacer attached to this, and 6 is an electrical device to be tested, for example, a gas insulated electrical device such as a gas insulated switchgear.

These configurations are not particularly different from conventional test equipment of this type. According to the present invention, a protection device 11 consisting of a parallel circuit of an inductance element 9 and a resistor 10 is connected between the secondary side terminal 8 of the transformer body 1 and the insulating spacer 4. In the example shown in FIG.
The container 12 is installed between the container 2 and the insulating spacer-attached container 3.

FIG. 1 shows an example of the protection device 11 in detail. The resistor 10 is manufactured in a cylindrical shape, and a metal oxide film or carbon film is formed on the surface of a cylindrical insulator such as ceramic. It consists of:

13 is a shield provided at both ends of the resistor 10 for relaxing the electric field.

The inductance element 9 is provided inside the cylinder of the resistor 10, and both ends thereof are connected to the shield 13.

Instead of this configuration, a linear conductor may be wound around the outer periphery of the cylinder of the resistor 10.

Moreover, the protective device 11 may be configured so that the rated voltage and rated capacity of the transformer main body 1 (
(KVA) to have an appropriate impedance value and insulation strength. For example, the rated voltage is 500KV,
In a transformer main body having a capacity of 250 KVA (30 minutes), the resistance value of the resistor 10 is selected to be 20 to 50 Ω, and the inductance of the inductance element 9 is selected to be around 1 (Low). FIG. 2 shows an equivalent circuit of the protection device 11, and L
C, RC is the inductance of the inductance element 9,
CC indicates the resistance value of the resistor 1o, and the stray capacitance of the protection device 11.

Note that an equivalent circuit as shown in FIG. 3 is established for a surge that rises very quickly. In the figure, LT and CT indicate the inductance and stray capacitance of the transformer body 1. Since the share of the surge voltage is determined by both stray capacitances CC and CT, the shape of the shield 13 is appropriately selected to set the stray capacitance CC, and thereby the initial voltage share of the protection device 11 is determined. In six or more configurations, which may be appropriate, the load current from the transformer main body 1 is supplied to the load via the inductance element 9 during steady state. Therefore, the resistor 10 does not generate heat.

During the test process, when a flash fault occurs on the load side and a steep surge voltage of, for example, 0.1 μs enters the transformer main body 1 side, the impedance of the inductance element 9 becomes large, so that the resistor 10 resists the surge voltage. The waveform steepness is moderated by sharing a part of the waveform with a low wavefront value.

FIG. 4 is a waveform diagram showing experimental results by the present inventor. The surge waveform when the resistor 10 is not connected is curve A, whereas when the resistor 10 is connected, the surge waveform is curved. It was confirmed that the wave front steepness was sufficiently suppressed as shown by I%B.

(Effects of the Invention) As detailed above, according to the present invention, a protection device consisting of a parallel circuit of an inductance element and a resistor is connected between the transformer body of a test transformer and the load to be tested. Therefore, even if a surge voltage were to be applied to the transformer body due to a flash fault occurring on the load side during the test process, it would be suppressed by the resistor, and therefore the transformer body would not suffer dielectric breakdown due to the surge voltage. This can easily be avoided, and the load current flows through the inductance element under normal conditions, so the resistor does not generate heat, making it a small resistor of this type. It has the advantage that it can be manufactured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view showing an embodiment of the present invention, Fig. 2 is its equivalent circuit diagram, Fig. 3 is an equivalent circuit diagram when a surge occurs, Fig. 4 is a waveform diagram for explaining operation, and Fig. 5 FIG. 1 is a front sectional view showing the overall configuration of the present invention. 1... Transformer main body, 6... Load to be tested, 8...
・Secondary side terminal, 9...Inductance element, 10...
·Resistor. 11...Protective device, Ikuwa Izu

Claims (1)

[Claims] Between the secondary terminal of the transformer main body and the load to be tested, an inductance element that has a high impedance against the surge voltage is connected in parallel to a resistor for suppressing the surge voltage from the load. A test transformer with a protective device connected.