EP3696837A1 - Device for protecting against electric impact or protecting against overcurrent - Google Patents

Abstract

In a device for protection against electric shock or for protection in the event of overcurrent for at least one power line to be monitored with at least one inductive component arranged electrically in series with the power line to be monitored, which acts indirectly or directly on a switch lock which is mechanically connected to at least one electrical connection Monitoring power line is coupled in series switching contact, it is provided that at least one capacitance (14) is electrically connected in parallel to the inductive component (3). This device for protection against electric shock or for protection against overcurrent is particularly suitable for power lines to be monitored flowing currents with high-frequency components have a low electrical burden.

Description

The invention relates to a device for protection against electric shock or for protection against overcurrent for at least one power line to be monitored with at least one inductive component which is electrically arranged in series with the power line to be monitored and which acts directly or indirectly on a switch lock which is mechanically connected to at least one electrical is coupled to the power line to be monitored in series switching contact.

Devices for protection against electric shock and for protection against overcurrent are known from the prior art. The use of these devices is required by relevant international and national installation regulations. These devices can be, for example, residual current protective devices or overcurrent protective devices.

In DE 10 2011 011 983 a residual current protective device designed as a residual current circuit breaker is disclosed. Residual current protective devices are primarily used to protect against electric shock and to protect against electrically ignited fires in electrical systems. To record fault currents, they have a summation current transformer through which the power lines to be monitored are routed. The vectorial sum of the currents (load currents) in the power lines to be monitored is recorded by the summation current transformer and represents a measure of the fault current. In the error-free state, currents flowing to and from the summation current transformer (load currents) are zero. In the event of an insulation fault against Earth, the return flow occurs depending on the fault resistance, but not completely through the summation current transformer. Part of it flows as a fault current through the fault resistance to earth. In this case the total current in the summation current transformer is not zero. The fault current is recorded as a residual current in the summation current transformer. The summation current transformer is followed electrically by an evaluation circuit with an assigned trip relay, which, if a permissible residual current limit value is exceeded, causes the switching contacts in the power lines to be monitored to open, which in the event of a fault ensures reliable separation of a downstream electrical system from the supplying power grid.

The summation current transformer of a residual current protective device usually consists of a magnetic core, which is usually designed as a toroid and which has the same number of primary windings depending on the number of power lines to be monitored. In each case a primary winding is arranged electrically in series with a power line to be monitored, through which the load currents flow. In addition, the summation current transformer has at least one secondary winding. This secondary winding is electrically connected to the evaluation circuit.

The primary windings together with the magnetic core form an inductance. The level of inductance is determined by the number of turns of each primary winding and the magnetic permeability of the magnetic core material. As already mentioned above, the total current recorded by the summation current transformer is zero if there is no insulation fault in an electrical system and the current flowing to and fro (load current) are the same. Due to the opposite current direction of the current flowing there and back, the phase difference is 180 degrees and thus the sum of the current in the summation current transformer is zero. The inductance of the summation current transformer is not effective in this case and does not represent a burden for the load current in the forward and return conductors.

However, this physical condition only applies to currents with frequencies up to a few MHz. With currents with a higher frequency (> 1 MHz), line-related delay differences become noticeable, which are hardly or not at all relevant for currents with low frequencies. These differences in transit time are physically caused in a known manner by the line coatings (resistance coating, conductor coating, capacitance coating, inductance coating) of an electrical line. Due to these transit time differences, depending on the level of the frequency of the current, it is possible that locally in the summation current transformer the difference in phase of the respective current in the forward and return conductors is not 180 degrees. Although there is no insulation fault and therefore no fault current flows, the summation current transformer virtually detects a differential current due to the currents in the forward and return conductors that do not add up to zero. In this case, the inductance of the summation current transformer becomes effective and represents a negative burden for the higher-frequency load currents in the forward and return conductors. Disconnection of a residual current protective device is usually optimized for residual currents of the rated frequency. The rated frequency is usually 50 Hz or 60 Hz. With the above-mentioned currents of higher frequency (> 1 MHz), there is no shutdown due to the principle.

In DE 199 51 249 an overcurrent protective device designed as a line circuit breaker is disclosed. Overcurrent protective devices offer protection against overcurrents and short circuits as well as protection against electric shock. This protects electrical circuits and connected equipment as well as people.

Miniature circuit breakers usually have two trigger functions.

A short-circuit current release, usually designed as a magnetic release, switches off the line circuit breaker immediately after a defined current limit is exceeded. A Overload release, on the other hand, causes a delayed shutdown for currents in the overload range above a specified triggering current of 1.45 times the rated current. The time until shutdown depends on the level of the overload current. It is switched off by mechanically unlatching a key switch. Unlatching the switch lock leads to the opening of the switch contacts and thus to the interruption of the current flow in the power lines to be monitored. In this way, in the event of a short circuit or overload, a safe separation of a downstream electrical system from the supplying power grid is guaranteed.

The short-circuit current release is usually implemented by a fixed inductance designed as an air-core coil with several windings and a movable ferromagnetic component (armature). The air coil is arranged in series with the power line to be monitored. In the event of a short-circuit current in the power line to be monitored, a large magnetic field is generated in the air-core coil. This magnetic field causes the movably arranged ferromagnetic component to move. This movement causes the key switch to be released immediately in order to quickly switch off the short-circuit current.

The inductance, designed as an air-core coil with several windings, with its reactance permanently represents a burden for the electrical current flowing through it. With increasing frequency f, reactance X _L of inductance L increases according to the known equation X _L = 2 x Π xfx L. This air-core coil thus represents an undesirably high electrical burden, especially for higher-frequency currents.

The inductive components of residual current protective devices and overcurrent protective devices described above thus represent a negative electrical burden, especially for higher-frequency currents in the power lines to be monitored.

Known and widespread in the prior art is a technique called PowerLan which uses existing electrical power lines in the low-voltage network to set up a local network for data transmission. Special PowerLan adapters are used to modulate the data signal in the high-frequency range, usually between 2 and 68 MHz, onto the electrical power lines. If the above-mentioned residual current protective devices or overcurrent protective devices are arranged for protection in the electrical power lines, this is disadvantageous because the inductive components of residual current protective devices or overcurrent protective devices represent a considerable electrical burden for the high-frequency data signals in a negative way. Because of this burden, data transmission, for example, between several low-voltage distributions which contain residual current protective devices or overcurrent protective devices for protection purposes, is not possible or is only possible to a very limited extent.

For an uninfluenced reproduction and recording of music, it is necessary that electrical systems with circuits for supplying power to equipment for reproducing and recording music are designed with as low an impedance as possible. However, the inductive components of devices for protection against electric shock and for protection against overcurrent mentioned above represent an electrical burden for load currents with higher frequency components of equipment for playing and recording music in a sonically negative manner.

The invention is therefore based on the object of providing devices for protection against electric shock and for protection against overcurrent which have a low electrical burden, in particular for currents with high-frequency components flowing in power lines to be monitored.

According to the invention, this object is achieved in that at least one capacitance is connected electrically in parallel with the inductive component.

It is thus provided that at least one capacitance designed as a capacitor is electrically connected in parallel to the inductive component of a device for protection against electric shock or for protection against overcurrent. In particular, a capacitance C for currents with a high frequency f has a low reactance Xc according to the known equation X _C = 1 / (2 x Π xfx C). The higher the frequency f, the lower the reactance X _C and thus the burden. The capacitance electrically connected to the inductance thus represents a bypass for currents with a high frequency. This enables currents with a high frequency to flow without loss and unhindered.

This is particularly advantageous when using a technique known as PowerLan, because the capacitance that is electrically connected to the inductance creates a bypass to the inductance for currents with higher-frequency components. As a result, the high-frequency data signals modulated onto the electrical power lines can also be transmitted beyond the limits of several low-voltage distributions.

This is also advantageous for unaffected playback and recording of music. Due to the capacitance that is electrically connected to the inductance, a bypass is created for load currents with higher frequency components. As a result, the high-frequency components in the load current can flow and be diverted unhindered, also taking into account the aspect of electromagnetic compatibility.

In a first embodiment of the invention it is provided that the device according to the invention is a residual current protective device. At least one capacitance is electrically connected in parallel to at least one primary winding of the summation current transformer.

In a further development of the invention it is provided that an inductance is additionally connected electrically in series to the secondary winding of the summation current transformer. This inductivity has the effect that high-frequency components in the current coupled into the secondary winding of the summation current transformer are not negatively influenced by the evaluation circuit.

In a further embodiment, it is provided that the device according to the invention is an overcurrent protective device. The inductance, which is a component of the short-circuit current release and an air-core coil with several windings, is electrically connected in parallel to a capacitance. The short-circuit current release is therefore an inductive component. The capacitance, which is electrically connected to the inductance, thus represents a bypass for currents with a high frequency. This ensures that components in the current with a high frequency can flow without loss and unhindered.

The overcurrent protective device can be a circuit breaker which preferably has at least one short-circuit current release designed with an inductance, a capacitance being connected electrically in parallel with the short-circuit current release.

Figur 1:

ein Blockschaltbild einer Fehlerstrom-Schutzeinrichtung aus dem Stand der Technik;

Figur 2:

ein Blockschaltbild einer erfindungsgemäßen Fehlerstrom-Schutzeinrichtung;

Figur 3:

ein Blockschaltbild einer Weiterbildung der erfindungsgemäßen Fehlerstrom-Schutzeinrichtung;

Figur 4:

ein Blockschaltbild einer Überstrom-Schutzeinrichtung aus dem Stand der Technik; und

Figur 5:

ein Blockschaltbild einer erfindungsgemäßen Überstrom-Schutzeinrichtung.

A device according to the invention is shown in the drawings. Show it:

Figure 1:

a block diagram of a residual current protective device from the prior art;

Figure 2:

a block diagram of a residual current protective device according to the invention;

Figure 3:

a block diagram of a development of the residual current protective device according to the invention;

Figure 4:

a block diagram of an overcurrent protection device from the prior art; and

Figure 5:

a block diagram of an overcurrent protection device according to the invention.

A known device 1 designed from the prior art as a residual current protective device for protection against electric shock has a summation current transformer 2, which consists of at least two primary windings 3 and at least one secondary winding 4.

The primary windings 3 are electrically connected in series with the power lines 13 to be monitored. The secondary winding 4 is connected to an evaluation circuit 6. If a certain residual current limit value is exceeded, a voltage signal is generated at the output of the evaluation circuit 6 and causes the trigger relay 7 electrically connected to the output of the evaluation circuit 6 to unlatch the switch lock 8 mechanically coupled to the trigger relay 7. The unlatching of the switch lock 8 has the effect that the switch contacts 9, which are arranged electrically in series with the power lines 13 to be monitored, are opened, so that in the event of a fault, the current flow in the power lines 13 to be monitored is interrupted. To test the function, the device 1 has a test circuit 10 which consists of a series connection of a test resistor 11 and a test button 12.

The detailed functional principle of a residual current protective device is known in the prior art and is therefore not explained further.

Figure 2 shows a first embodiment of the inventive device 1 designed as a residual current protective device for protection against electric shock. Each primary winding 3 consists of at least one Turn, with all primary windings having the same number of turns. With the magnetic permeability of the magnetic core 5 of the summation current transformer 2, there is an inductance for each primary winding. According to the invention, each inductance consisting of at least one primary winding 3 of the summation current transformer 2 is electrically connected in parallel with a capacitance 14. This is advantageous because each capacitance 14 electrically connected to form a primary winding 3 represents a bypass for currents with a high frequency. This enables currents with a high frequency to flow through the power lines 13 to be monitored without loss and unhindered.

Figure 3 shows a further development of the inventive device. An inductance 15 is electrically connected in series to the secondary winding 4 of the summation current transformer 2 and the evaluation circuit 6. The inductance 15 advantageously has the effect that high-frequency components (> 1 MHz) in the current coupled into the secondary winding 4 of the summation current transformer from the primary windings 3 are not negatively influenced by the evaluation circuit 6. The evaluation circuit 6 usually has components for voltage limiting on the input side. These components have negative parasitic capacitances that have a low-impedance burden for currents with a high frequency (> 1 MHz). The inventive inductance 15, which is arranged electrically in series, again advantageously represents a high-resistance impedance for currents with a high frequency (> 1 MHz). High-frequency components (> 1 MHz) coupled into the current from the primary windings 3 to the secondary winding 4 of the summation current converter are now are advantageously not negatively influenced by the evaluation circuit 6.

Due to the inventive design of a residual current protective device, it is now advantageously possible, for example, for the PowerLan adapters mentioned above to be able to communicate between several low-voltage distributions.

Figure 4 shows a device 1, known from the prior art, designed as a line circuit breaker for protection against overcurrent. The device 1 has a short-circuit current release 3 and a thermal release 16, also referred to as an overload release, which are mechanically coupled to a switch lock 8. The short-circuit current release 3 and the thermal release 16 are arranged in series with the power line 13 to be monitored and the switching contact 9, which is mechanically coupled to the switching mechanism 8. The short-circuit current release 3 is usually implemented by a fixedly arranged inductance designed as an air-core coil with several windings and a movable ferromagnetic component (armature). The short-circuit current release 3 is thus an inductive component. In the event of a very high current, which is significantly greater than the rated current of the line circuit breaker, the short-circuit current release 3 causes the switching contact 9 to open immediately due to its magnetic principle and its mechanical coupling to the switch lock 8. A current flows in the power line 13 to be monitored that is somewhat is greater than the rated current of the circuit breaker, the thermal release 16 causes the switching contact 9 to open within a certain time. Depending on this overcurrent, the switching contact 9 can be opened within a few seconds or only after several minutes.

The detailed functional principle of a line circuit breaker is known in the prior art and is therefore not explained further.

Figure 5 shows a first embodiment of the inventive device 1 designed as an overcurrent protection device for protection against overcurrent. According to the invention, the short-circuit current release 3, which has an inductance due to its air-core coil, has a capacitance 14 connected electrically in parallel. This is advantageous because the capacitance 14, electrically connected in parallel with the short-circuit current release 3, for currents with a high frequency represents a bypass. This enables currents with a high frequency to flow through the power line 13 to be monitored without loss and unhindered.

Claims (7)

Device for protection against electric shock or for protection in the event of overcurrent for at least one power line to be monitored with at least one inductive component arranged electrically in series with the power line to be monitored, which acts indirectly or directly on a switch mechanism which is mechanically connected to at least one electrical connection with the power line to be monitored switching contact arranged in series is coupled,
characterized,
that at least one capacitance (14) is electrically connected in parallel to the inductive component (3). Device according to Claim 1, characterized in that the device (1) is a residual current protective device. Device according to Claim 2, characterized in that the residual current protective device has at least one summation current transformer (2) and that a capacitance (14) is connected electrically in parallel to at least one primary winding (3) of the summation current transformer (2). Device according to Claim 3, characterized in that in addition to the secondary winding (4) of the summation current transformer (2), an inductance (15) is electrically connected in series. Device according to Claim 1, characterized in that the device (1) is an overcurrent protective device. Device according to Claim 5, characterized in that the overcurrent protective device is a line circuit breaker. Device according to Claim 6, characterized in that the line circuit breaker is at least one designed with an inductance Short-circuit current release (3) and that a capacitance (14) is connected electrically in parallel with the short-circuit current release (3).

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