Lightning and overvoltage protection device for data networks, telephony services, electroacoustic installations or bus systems

Abstract

The invention relates to a lightning and overvoltage protection device for data networks, telephony services, electroacoustic installations or bus systems having at least two grid-side input terminals and at least two output terminals, to which the load that is to be protected can be connected, furthermore having a gas-discharge surge arrester that connects the input terminals and an inductance located between the respective input and output terminal. According to the invention, the inductances are configured as current-compensated inductors having a core and a primary winding and a secondary winding, wherein the load current flows through the windings in different directions so that the respective magnetic fields cancel out. In the event of transient overvoltages, the arising surge current is bypassed by means of a switching device that then closes at one of the two windings, for example the secondary winding, in such a way that, owing to the winding through which current flows, for example the primary winding, the core reaches saturation and the coupling between the windings is released, with the result that no voltage is established across the load and the voltage applied to the winding through which current flows ignites the gas-discharge surge arrester.

Claims

1. Lightning and overvoltage protection device for data networks, telephony services, electroacoustic systems or bus systems, having at least two grid-side input terminals (1; 2) and at least two output terminals (3; 4) to which the load (L) to be protected can be connected, furthermore having a gas-discharge surge arrester (GDT) that connects the input terminals (1; 2) and an inductance located between the respective input and output terminals (1; 3/2; 4), characterized in that the inductances are designed as current-compensated inductors having a core and a primary winding (L.sub.1) and a secondary winding (L.sub.2), wherein the load current flows through the windings (L.sub.1; L.sub.2) in different directions, so that the respective magnetic fields cancel each other out and, in the event of transient overvoltages, the arising surge current is conducted past one of the two windings (L.sub.2) by means of a switching device (S.sub.1) which then closes, in such a way that the core reaches saturation through the current-carrying winding (L.sub.1) and the coupling (k) between the windings (L.sub.1; L.sub.2) is cancelled, with the result that no voltage is built up across the load (L) and the voltage applied to the current-carrying winding (L.sub.1) ignites the gas-discharge surge arrester (GDT).

2. Lightning and overvoltage protection device according to claim 1, characterized in that the switching device (S.sub.1) is designed as a semiconductor switch, wherein the base or gate thereof is connected to one of the input terminals (1).

3. Lightning and overvoltage protection device according to claim 2, characterized in that the semiconductor switch is designed as an IGBT.

4. Lightning and overvoltage protection device according to claim 2, characterized in that the base or the gate of the semiconductor switch is connected to the input terminal (1) via a TVS diode.

5. Lightning and overvoltage protection device according to claim 1, characterized in that the gas-discharge surge arrester (GDT) can be extinguished by opening the switching device (S.sub.1).

6. Lightning and overvoltage protection device according to claim 1, characterized in that the core of the current-compensated inductors is designed as a toroidal core.

7. Lightning and overvoltage protection device according to claim 1, characterized in that the respective protection level of the overall device can be predetermined via the response behavior of the switching device (S.sub.1).

8. Lightning and overvoltage protection device according to claim 1, characterized in that the winding (L.sub.1) through which current continues to flow in the case of the closed switching device (S.sub.1) has an effective inductance of ≥2 μH.

9. Lightning and overvoltage protection device according to claim 1, characterized in that the core of the current-carrying inductor has a small volume for achieving rapid saturation.

Description

(1) The invention will be explained in more detail below with reference to an embodiment example and the drawings, wherein:

(2) FIG. 1a shows a schematic diagram of the lightning and overvoltage protection device according to the invention in normal operation with open switching device S.sub.1;

(3) FIG. 1b shows an ideal equivalent circuit diagram in normal operation with open switching device S.sub.1;

(4) FIG. 2a shows a schematic diagram of the lightning and overvoltage protection device according to the invention with closed switching device S.sub.1; and

(5) FIG. 2b an equivalent circuit diagram in the event of overvoltage and given saturation of the primary winding L.sub.1.

(6) The lightning and overvoltage protection device according to the invention as shown in the figures is based on two input terminals 1 and 2, wherein a load is connected to output terminals 3, 4.

(7) In addition, a gas-discharge surge arrester GDT connecting input terminals 1; 2 is provided.

(8) The primary winding L.sub.1 of a current-compensated inductor with core is disposed between input terminal 1 and output terminal 3.

(9) The secondary winding L.sub.2 of the current compensated inductor is located between input terminal 2 and output terminal 4.

(10) Furthermore, a switching device S.sub.1 is connected to output terminal 3 and input terminal 2, which is open during normal operation.

(11) Due to the design of the primary winding L.sub.1 and the secondary winding L.sub.2 as current-compensated inductors with core, the inductances cancel each other out with the desired ideal coupling, so that the equivalent circuit diagram shown in FIG. 1b results. The relevant relationships to negative feedback and coupling k are explained in FIGS. 1a and 1b.

(12) In the event of overvoltage, as shown in FIGS. 2a and 2b, the switching device S.sub.1, which is preferably designed as a semiconductor switch and preferably as an IGBT, is closed. As a result, a high current flows through the primary winding L.sub.1, which drives the winding core into saturation. This removes the coupling k between the primary winding L.sub.1 and the secondary winding L.sub.2.

(13) In the case of saturation, no energy is transmitted from the primary side to the secondary side of the current-compensated inductor, i.e. no voltage is built up above the load.

(14) The remaining residual inductance from the primary winding L.sub.1 builds up a high voltage which ignites the gas-discharge surge arrester GDT in the desired manner.

(15) The corresponding ideal equivalent circuit diagram in the event of overvoltage at saturation is shown in FIG. 2b.

(16) The winding core of the current-compensated inductor is dimensioned so that the coupling k is close to 1 in normal operation and close to 0 in overvoltage conditions.

(17) In order to cancel the inductive coupling as quickly as possible in the event of an interference pulse, it is necessary to drive the core of the inductor into saturation as quickly as possible in the event of an overvoltage. In order to achieve this, the following dimensioning parameters have been developed on the basis of extensive investigations with different cores. On the one hand, the core volume must be kept as small as possible in order to achieve rapid saturation. When dimensioning the windings, it must also be ensured that they do not overlap, i.e. that in the case of saturation the secondary inductance is not interspersed by the field lines of the primary inductance. A low coupling in case of saturation is advantageous.

(18) Furthermore, an embodiment is advantageous in which the windings are rotated by 90° so that the field lines no longer intersect the secondary coil vertically when saturated. For this purpose, specially manufactured cores are used, which are turned in themselves.