JPS5840592Y2 - Resin molded instrument transformer - Google Patents

Description

[Detailed description of the invention] This invention relates to a dry resin mold instrument transformer manufactured using epoxy resin, etc., and in particular, to improving the corona discharge characteristics of the resin mold instrument transformer. be.

A typical conventional resin molded instrument transformer has a first
It is constructed as shown in FIG.

That is, the high voltage coil 2 and the low voltage coil 4 are connected via the main insulating layer 3.
are respectively wound, impregnated or cast with a synthetic resin such as epoxy resin using a mold, etc., and molded together with the outer peripheral insulating layer 10.

Then, the iron core 5 is attached to the resin molded coil thus formed.

In addition, when in use, it is fixed in a predetermined position with the mounting feet 7 attached to the iron core 5.

In the conventional resin-molded instrument transformer described above, due to the dimensional relationship between the resin-molded outer insulating layer 10 and the iron core 5 during assembly, an air layer 9 is formed between the outer insulating layer 10 and the iron core 5. Interventions were common.

Furthermore, since the mounting leg 7 of the instrument transformer is generally attached and fixed to the ground potential point, the iron core 9 was at the same potential as the ground potential.

Therefore, while the resin molded instrument transformer is in operation, the high voltage on the primary side applied to the high voltage coil 2 is the same as if it were insulated from the ground via the outer insulating layer 10 and the air layer 9. The electric potential applied between the high-voltage coil 2 and the iron core 5 has a small dielectric constant and the air layer 9, which is a minute gap, has a large potential share, and a partial discharge occurs in the air layer 9.

When this partial discharge accumulates, the outer peripheral insulating layer 10 deteriorates due to discharge, and eventually dielectric breakdown occurs, resulting in a short circuit between the high voltage coil 2 and the iron core 5, resulting in a major accident.

This idea was made in view of these points, and attempts to eliminate the above-mentioned drawbacks of the conventional method by providing an electric field relaxation layer having voltage non-linear resistance characteristics between the outer peripheral insulating layer and the iron core. It is.

Hereinafter, a basic embodiment of this invention will be described in detail with reference to the drawings.

3 and 4, a voltage non-linear resistance paint whose resistance changes non-linearly with respect to an electric field is applied to the surface of the outer insulating layer 10 between the outer insulating layer 10 and the iron core 5, for example.
An electric field relaxation layer 11 is provided, which is formed by applying a high-resistance paint containing a suitable amount of a mixture of silicon carbide powder and a binder, which is an adhesive.

The length of the electric field relaxation layer 11 is set to be longer than the length h of the iron core 5 by about 20 mm on each side.

The length depends on the rated voltage on the high voltage side of the resin molded instrument transformer or the resistance of the electric field relaxation layer 11 used.
It is determined as appropriate depending on the electric field strength characteristics.

According to such a configuration, in the electric field relaxation layer 11 on the surface of the outer peripheral insulating layer 10 facing the iron core 5, the resistance is small in parts where the applied electric field is high, and the resistance is large in parts where the electric field is low. The intensity is relaxed and partial discharges are less likely to occur.

Comparing this in terms of partial discharge inception voltage, the partial discharge inception was improved by about 180% compared to the conventional example.

As described above, this invention eliminates the occurrence of partial discharge between the iron core and the surface of the outer peripheral insulating layer facing it during operation, prevents discharge deterioration, and prevents short-circuit accidents. It is possible to provide a resin molded instrument transformer with an extremely long discharge life.

[Brief explanation of the drawing]

Figures 1 and 2 both show a conventional resin molded instrument transformer, with Figure 1 being a side view with a partially cross-sectional section, and Figure 2 being taken along line II-II in Figure 1. The sectional view, FIG. 3, and FIG. 4 all show one embodiment of this invention, and FIG. 3 is a side view with a partially sectional portion;
FIG. 4 is a sectional view taken along line IVIV in FIG. 3. In the figure, 2 is a high voltage coil, 4 is a low voltage coil, 5 is an iron core, 10 is an outer peripheral insulating layer, and 11 is an electric field relaxation layer. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] In a resin molded instrument transformer, which consists of a high-voltage coil and a low-voltage coil concentrically wound through a main insulating layer, and an iron core attached to a resin-molded coil impregnated or cast with synthetic resin. , a resin mold characterized in that an electric field relaxation layer having voltage nonlinear resistance characteristics is provided on the surface of the insulating layer over a range longer than the length of the iron core, between the outer peripheral insulating layer of the resin molded coil and the iron core. Type instrument transformer.