A three phase surge protection device is disclosed. In an embodiment a device include a stack comprising a first varistor, a second varistor and a third varistor, wherein the varistors are electrically connected to form a circuit and a first thermal disconnect configured to interrupt the circuit when a temperature of the first thermal disconnect exceeds a predefined temperature.

A varistor (50) comprising: a feed-through conductor (52) and a varistor disc (72) interposed between, and electrically connected to, conductor layers disposed on opposite surfaces of the varistor disc (72), the conductor layers being electrically isolated from one another; wherein the varistor disc (72) comprises a through aperture (60) through which the feed-through conductor extends; a first one of the conductor layers is electrically connected to the feed-through conductor; a second one of the conductor layers is, in normal use, permanently electrically connected to ground the varistor (50). This configuration enables one side of the disc (72) to be connected to the feed-through terminal, and the other side of the disc (72) to be connected to a ground plane, such as an earthed bulkhead of a wall or cabinet, via a metal plate forming part of the varistor (50) housing.

A varistor (50) comprising: a feed-through conductor (52) and a varistor disc (72) interposed between, and electrically connected to, conductor layers disposed on opposite surfaces of the varistor disc (72), the conductor layers being electrically isolated from one another; wherein the varistor disc (72) comprises a through aperture (60) through which the feed-through conductor extends; a first one of the conductor layers is electrically connected to the feed-through conductor; a second one of the conductor layers is, in normal use, permanently electrically connected to ground the varistor (50). This configuration enables one side of the disc (72) to be connected to the feed-through terminal, and the other side of the disc (72) to be connected to a ground plane, such as an earthed bulkhead of a wall or cabinet, via a metal plate forming part of the varistor (50) housing.

A thermally protected metal-oxide varistor is provided, including a disconnecting unit, a first varistor assembly and a second varistor assembly. The first varistor assembly and the second varistor assembly are connected in series through a low-melting-point alloy layer; wherein when the low-melting-point alloy layer is fused, the disconnecting unit acts to cut off the low-melting-point alloy. The two varistors are connected directly through solder joints without any transition connection member. The heat transfer path is reduced to the shortest path, and a faster response is realized compared to conventional products formed by a varistor and a disconnecting unit when abnormal over-current passes. Moreover, the slider functions as a physical separator capable of isolating the two varistors after the solder joints are fused, which further diminishes the risk of fire occurrence caused by the failure of instantly blocking current by the disconnecting unit when the varistor breaks down by over-current.

A surge protection device (14) comprises at least one disconnecting device (38) provided in a housing (50), a heat-conducting element (40), an actuating element (42) for actuating an indicating device (44), and a locking element (58), the heat-conducting element (40) being in contact with the housing (50). The actuating element (42) is fastened to the heat-conducting element (40) by means of the locking element (58), and the fastening is configured such that when a predetermined temperature at the locking element (58) is exceeded, the locking element (58) is detached from the heat-conducting element (40) and/or from the actuating element (42) and releases the actuating element (42)

A modular surge protection system (10) is furthermore shown.

A surge protection device (14) comprises at least one disconnecting device (38) provided in a housing (50), a heat-conducting element (40), an actuating element (42) for actuating an indicating device (44), and a locking element (58), the heat-conducting element (40) being in contact with the housing (50). The actuating element (42) is fastened to the heat-conducting element (40) by means of the locking element (58), and the fastening is configured such that when a predetermined temperature at the locking element (58) is exceeded, the locking element (58) is detached from the heat-conducting element (40) and/or from the actuating element (42) and releases the actuating element (42)

A modular surge protection system (10) is furthermore shown.

A surge protection device comprises at least one disconnecting device provided in a housing, a heat-conducting element, an actuating element for actuating an indicating device, and a locking element, the heat-conducting element being in contact with the housing. The actuating element is fastened to the heat-conducting element by means of the locking element, and the fastening is configured such that when a predetermined temperature at the locking element is exceeded, the locking element is detached from the heat-conducting element and/or from the actuating element and releases the actuating element.

A surge protection device comprises at least one disconnecting device provided in a housing, a heat-conducting element, an actuating element for actuating an indicating device, and a locking element, the heat-conducting element being in contact with the housing. The actuating element is fastened to the heat-conducting element by means of the locking element, and the fastening is configured such that when a predetermined temperature at the locking element is exceeded, the locking element is detached from the heat-conducting element and/or from the actuating element and releases the actuating element.

The invention relates to a surge protection device having a plurality of surge arresters and, in particular thermal, isolating apparatus which is respectively associated with them together with a fault and state display which is designed as a movable, spring force-prestressed displacement element (17) and has a display area and also an operating area for a telecommunications device, wherein tripping of the fault and state display is performed indirectly by means of a blocking element (1, 2, 3) of which the physical state can be changed. According to the invention, a blocking element is provided for each of the surge arresters, which blocking element is in each case arranged so as to block the movement path (4, 5, 6) of a mechanically prestressed wedge slide (7, 8, 9) with a wedge bevel (12). A rocker lever arrangement is also provided which has first lever arms (13, 14, 15) in accordance with the number of wedge slides and at least one second lever arm (16) for blocking, but also for releasing, the displacement element. Those ends of the first lever arms which are remote from the rotation axis (19) of the rocker lever arrangement each have an area (20) for sensing the respective wedge bevel of the respective wedge slide in such a way that, when the movement path of at least one of the wedge slides is cleared, its wedge bevel lifts the relevant first lever arm, as a result of which the second lever arm releases the displacement element.

An electrical connector provided with a varistor, and to a protection device for incorporation into an electrical connector and having a varistor comprising at least two pins including a first pin which is a live (502) or neutral (504) pin and a second pin which is an earth pin (506), the first and second pins (502, 504, 506) extending through respective apertures (512) in a varistor plate (514) which has first and second faces, wherein a first conductive layer on the first face of the varistor plate (514) connects electrically to the first pin (502, 504) and a second conductive region on the second face of the varistor plate connects electrically to the second pin (506), so that in response to an excessive voltage across the first (502, 504) and second (506) pins the varistor plate will conduct electricity between the first (502, 504) and second (506) pins. The arrangement can easily be adopted in connectors conforming to existing standards, such as existing mains electrical plugs (500).