SU1660057A1 - Device for protection against overvoltage - Google Patents

Description

The invention relates to electrical engineering and can be used to protect high-voltage networks from overvoltages.

The purpose of the invention is to increase the service life of the device for surge protection by aligning the voltage distribution along the varistor column.

Figure 1 shows the design of a device for surge protection, a longitudinal section; figure 2 is a section aa in figure 1.

The device for overvoltage protection contains an insulating housing 1 with upper and lower end conductive flanges 2. Inside the housing 1, at least one column of series-connected varistors 3 is installed, each made in the form of a disk with electrodes 4 on the end surfaces. Attached to the upper flange of the housing 1 of the device by means of screen holders 5

2 · (57) The invention relates to electrical engineering. The purpose of the invention is to increase the service life by balancing the voltage along the varistors. The device comprises an insulating housing, inside which a column of varistors is installed, made in the form of disks with contact electrodes, the surface areas of which vary from top to bottom in proportion to the ratio of the actual voltage in the section of the varistor column with the same areas of contact electrodes to the voltage in this section of the column under conditional uniform voltage distribution along the column. 1 C.p. f-ls, 2 ill.

toroidal screen 6. On the side surface of the part of the varistors 3 adjacent to the upper flange 2, rods 7 of a heat-resistant ferroelectric material are installed close to it, which alternate with an insulating material 8 with high thermal conductivity. The ends of the rods 7 are covered with a metal oilcloth 9, which is in contact with the corresponding extreme electrodes of the varistors of the specified part of the column.

The surface areas of the contact electrodes 4, varistors 3 columns are selected sequentially varying in the direction from the upper flange to the lower flange in proportion to the ratio Δυ _Φ / Δϋ _Ρ , where ΔΐΙψ and Δυ _ρ are the voltages in the column section of the varistors with the same areas of the contact electrodes, respectively, with a practically uneven

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1660057 A1

And a conditionally uniform voltage distribution along the varistor column.

Device for surge protection works as follows.

In the normal operating mode of the power line, a small conductivity current flows through the varistors. When overvoltage in the network, the resistance of the varistors decreases sharply, which leads to an increase in the current through them, Varistors perceive the energy of the overvoltage and thereby protect the insulation of the rest of the electrical equipment. Porcelain case 1 with flanges 2 provides isolation of varistors from environmental influences and carries operational mechanical loads, Screen 6 with screen holders 5 is necessary for external voltage equalization, the presence of rods 7 made of ferroelectric equalizes the field strength values (removing possible inhomogeneities) near the upper varistor disks operating in the most adverse conditions, and the choice of surface areas of the electrodes and varistors 3 varying from top to bottom in proportion to the ratio Δυψ / ΔΐΙρ yes There is reliable voltage equalization on the varistors of the column.

The use of insulating material with high thermal conductivity between the housing and the varistors can reduce the influence of adverse processes on the surface of the housing by removing heat from overheated varistors and rods from a ferroelectric and thereby maintain their normal mode of operation.

Considering that the presence of an uneven voltage distribution along the varistors of the device leads to their accelerated aging and failure, especially in the region of increased inhomogeneous field strength, the introduction of dielectric rods in this region and the artificial change in the resistances of identical series-connected disks by changing the electrode surface areas allows us to further equalize voltage values on varistors and thereby increase their service life.

Claims (2)

Claim 1. Device for surge protection, comprising an insulating casing with upper and lower conductive flanges, inside of which is installed at least one column of varistors made in the form of disks with contact electrodes on the end surfaces, and a toroidal electrostatic screen located under the upper flange and reinforced on it using screen holders, characterized in that, in order to increase the service life by aligning the voltage distribution along the varistor column, the surface area of the contact ktnyh electrodes varistors said column successively measured in a direction away from the upper housing flange to the lower flange proportional relation ΔΐΙψ / Δ and _F gdeL and _F - the actual voltage on the varistor column portion with the same area of contact electrodes at the actual nepravnomernom distribution of stress along the varistor column, Δΐ) _Ρ - voltage in the same section of the varistor column with a conditional uniform distribution of voltage along the varistor column and the same area of the contact electrodes . 2. The device according to claim 1, characterized in that close to the lateral surface of the varistors of the column portion adjacent to the upper flange, additionally inserted rods of heat-resistant ferroelectric material are installed uniformly around the perimeter of the column, the upper and lower ends of the rods being metallized and connected to the electrodes extreme varistors of the specified part of the column, and the gaps between adjacent rods are filled with additionally introduced insulating material with high thermal conductivity.