The invention belongs to the field of devices for energy overvoltage protection, more precisely to the field of modules provided with a varistor and a system for triggering short circuit upon occurrence of overvoltage in a network.

The technical problem solved by the present invention is a constructional solution to a reliable and rapid operation of an overvoltage protection module with a varistor that creates short circuit by overheating a triggering element. Despite lightning protection, electric installations in homes, schools, hospitals, industrial facilities, offices, power plants and similar places may be burdened with short-term surge voltages that can damage devices and apparatuses connected to a network. These devices can be protected by integrated overload modules that intercept high voltages and cut off the supply voltage.

Various forms of overvoltage modules based on varistor operation are known. EP 1 798 742 A1 discloses an overvoltage protection element including a wafer of a varistor and a meltable member bridging the wafer of the varistor in case of thermal overload. The solution is based on a solder arranged around an internal piston that gets heated in case of thermal overload of the varistor, the solder melts and flows from the piston to the bottom of a housing thus creating short circuit between the housing and the internal piston, which functions as a short-circuit bridge. This solution is closest to the solution of the invention in that the heating of the varistor in the solution from EP 1 798 742 A1 causes short circuit between the internal piston and the bottom of the module, whereas, according to the present invention, two blocking elements from a meltable material start melting, which releases a spring that pushes a plate against a wall of the housing thus causing short circuit.

The essence of the overvoltage protection module of the invention lies in a constructional shape of a section causing short circuit when a varistor gets heated due to the presence of overvoltage overload.

The overvoltage protection module of the invention will be described in more detail in the continuation by way of drawings representing in:

• Figure 1 - Overvoltage protection module assembly
• Figure 2 - Piston 31 with plate 41 and spring 51

An overvoltage protection module consists of a housing 1 shaped like a hollow cuboid with a cylindrical threaded pin 1a. The bottom of the housing 1 is provided with a varistor 2, above which there is a piston 3 with drilled holes 3a and 3b on both parallel sides, between which a movable side wall shaped like a plate 4 is arranged. The movable side wall 4 is provided at its upper edge with drilled holes 4a and 4b and at its side edge with two holes 4c. The internal side of the plate 4 is provided with a holder of a spring 5 compressed in a way that the external part of the plate 4 is level with the external edges of the piston 3. A meltable material is poured or inserted into said drilled holes 3a and 3b and the parallel drilled holes 4a and 4b. A plate 7, onto which a flexible wire 6 is fastened, is fastened with screws 7a and 7b in the drilled holes 4a and 4b. The piston 3 is closed by a piston 8 having a cylindrical pin 8a that simultaneously also functions as a second connection pin. The cylindrical pin 8a of the piston 8 is provided with a rectangular insulation body 9 with one cut-out wall that allows the plate 4 to come in contact with the wall of the housing 1 in case of overvoltage on the varistor 2. The body 9 together with the varistor 2, the piston 3 with the plate 4, the wire 6 on the plate 7 and with the piston 8 assembly are pushed towards the bottom of the housing 1 by a spring 10 that is compressed by a cover 11 with a round hole 11a for the pin 8a.

The piston 3 is provided with several drilled holes on two parallel side walls and with one or several drilled holes on the bottom section of the piston 3. The movable side wall 4 on the upper edge is provided with two or several drilled holes and with two or several holes on side edges and/or a hole in the bottom side.

In case of overvoltage or increased temperature in the network the varistor 2 gets heated, consequently the piston 3 and the material in the neighbouring drilled holes 3a and 4a and the drilled holes 3b and 4b get heated as well. The softened material in the neighbouring drilled holes 3a and 4b and in the drilled holes 3b and 4b can no longer withstand the force of the pre-stressed spring 5, which causes the pre-stressed spring 5 to release and push the short-circuit plate 4 into the wall of the housing 1. The short-circuit plate 4 is linked to the piston 3 with a flexible wire 6, through which current flows to the short-circuit plate and consequently to the wall of the housing 1 thus causing short circuit.

The overvoltage protection module functions as follows: in case of overvoltage or increased voltage the varistor 2 gets heated which causes heating of the meltable material in the piston 3, consequently the pre-stressed spring 5 releases and pushes the plate 4 against the wall of the housing 1 and thus short circuit occurs between the supply pins 1a and 8a.

The overvoltage protection module according to embodiment I is provided in the interior of the housing 1 with the varistor 2, above which a piston 31 with a movable plate 41 is arranged. A cylindrical pin 41a provided with a spring 51 is arranged perpendicularly to the plate 41. The plate 41 with the spring 51 is arranged in a wall 31a of the piston 31 and fixed with a meltable material 12. The material 12 blocks the spring 51.

In case of overvoltage or increased voltage in the network the module according to embodiment I gets heated due to the heating of the varistor 2, the piston 31 and the material 12 also get heated, which releases the pre-stressed spring 51 that pushes the short-circuit plate 41 against the wall of the housing and causes short circuit. The overvoltage protection module of the invention is suitable mostly for wind farms and solar power plants.