CN103683182A - Circuit arrangement used for electric protective device - Google Patents

Abstract

Circuit arrangements for electrical protective devices. The invention relates to a circuit arrangement (10) for an electrical protection device, comprising: an electric line (12), an electromagnetic separation device (16), a switching device (T1), a control device (18), said electromagnetic separation device being constructed for In order to electrically separate the electrical lines (12) when a voltage (U) is applied, the switching device is designed to apply a voltage (U) to the electromagnetic disconnecting device (16) as a function of a trigger signal (trig), so that said control means for detecting the presence of fault currents and/or arcs in/on said electric line (12) and for generating, in the presence of fault currents and/or arcs, for said switching means (T1) Trigger signal (trig), wherein the control device (18) is designed to detect a zero crossing of the voltage (U) and to generate a trigger signal for the switching device (T1) as a function of the detected zero crossing (trig).

Description

Circuit devices for electrical protection devices

technical field

The invention relates to a circuit arrangement for an electrical protection device. Furthermore, the invention relates to a method for operating an electrical protective device.

Background technique

Electrical protection devices are commonly used in electrical installation systems. Examples of electrical protective devices are overcurrent protective devices and arc fault protective devices for protecting electrical installations from damage by arc faults, by means of which fault current protective devices can prevent fault currents from being grounded. Protective devices generally require circuit arrangements with analog and/or digital components, by means of which fault currents or arcs can be detected. Furthermore, a trigger signal for actuating the disconnecting device can be output by means of such a circuit arrangement, which triggers the electrical disconnection of the electrical circuit or line of the installation system in which a fault was detected from the power supply device.

If fault currents or arcs are present, an electromechanical coupling is required by means of which the circuit or line can be separated from the supply. A very cost-effective solution can be realized by means of an electromagnetic separation device according to the moving coil principle. Such an electromagnetic separating device has a coil by means of which a push rod can be moved. Through the movement of the push rod, the electrical contacts can be opened. Here, a sufficiently high electromagnetic force must be provided by means of the coil, so that the electrical contact can be separated from the plunger. The coil is usually connected to a voltage. Since in electrical systems supply voltages in the range of 50 V to 400 V are provided to operate the individual components, it must be ensured on the one hand that the electromagnetic disconnecting device also provides sufficient force for opening the contacts even at low voltages. On the other hand, the electromagnetic separating device must not be damaged at high voltages.

To meet these two requirements, three different solutions have been followed so far. On the one hand, it is possible to provide coils which can also be used for high voltages. In order for the coil not to be damaged even under the high energy or power conditions that occur here, a large number of windings and corresponding wire cross-sections are required. Another possibility is to use coils designed for lower voltages and to limit the electrical power in the coils by means of a voltage regulator. Finally, electromagnetic disconnection devices can be used, which are activated at very low electrical power. For this purpose, magnetic switches can be used, for example. All described embodiments require additional installation space in the electrical protective device and entail additional costs.

Contents of the invention

It is therefore the object of the present invention to provide a circuit arrangement of the type mentioned at the outset, with which a protective device can be operated more simply and cost-effectively.

The object is achieved by a circuit arrangement having the features of claim 1 and by a method having the features of claim 8 . Advantageous developments of the invention are specified in the dependent claims.

A circuit arrangement according to the invention for an electrical protective device comprises an electrical line, an electromagnetic disconnection device, a switching device, a control device, the electromagnetic disconnection device being designed to electrically disconnect the electrical circuit when a voltage is applied, the switching device Designed to apply a voltage to the electromagnetic separating device in dependence on a trigger signal, the control device is used to detect the presence of fault currents and/or arcs in/on electrical lines and for the presence of fault currents and/or arcs Next, a triggering signal for the switching device is generated, wherein the control device is designed to detect a zero crossing of the voltage and to generate a triggering signal for the switching device as a function of the detected zero crossing.

The circuit arrangement can be used in a current fault protective device and/or an arc fault protective device. The circuit arrangement can be arranged in a housing of the electrical protective device. The circuit arrangement comprises at least one electrical line, to which a voltage, in particular an alternating voltage, can be applied. The circuit arrangement can also be used in polyphase systems. Furthermore, the circuit arrangement includes an electromagnetic disconnecting device of the protective device, which can be designed according to the moving coil principle. The terminals of the electromagnetic separation device can be connected with electric lines. To operate the electromagnetic separating device, the electromagnetic separating device can be supplied with voltage. For this purpose, a switching device, for example in the form of a thyristor, can be used, by means of which the electromagnetic disconnecting device can be connected to an electrical line and to an additional ground. After the electromagnetic separators are connected to line and ground, voltage is applied to their terminals. This causes current to flow through the coil of the electromagnetic separation device. Due to the electromagnetic force of the coil, the movable plunger of the electromagnetic separating device is moved. Through the movement of the push rod, the contacts of the electrical lines can be separated.

Furthermore, the circuit arrangement includes a control device which is designed to detect a fault current and/or an arc in/on the electrical line or in a line connected to the electrical line. As an alternative thereto, the control device can receive signals from an external detection device by means of which fault currents and/or arcs are detected. If a fault current and/or an arc is detected, the control device can output a trigger signal to the switching device, as a result of which the switching device applies a voltage to the electromagnetic disconnecting device. By applying a voltage to the electromagnetic separating device, the electromagnetic separating device is activated and separates the electrical lines.

If the electromagnetic separating device or its coil is connected to a voltage at any moment, the current flows through the coil until the voltage reaches the next zero crossing. This means that the current flows through the coil at a maximum for the duration of the half-wave. The control device is additionally designed to detect a voltage zero crossing and to actuate the switching device as a function of the detected zero crossing. The energy absorption of the coil can thus be adjusted and reduced. This enables the use of electromagnetic separating devices with coils having a smaller number of windings and/or smaller wire cross-sections. Costs and installation space can thus be saved.

The control device is preferably designed to generate a trigger signal for the switching device temporally after a predetermined time period after the detected zero crossing. The duration of the current flow can thus be precisely adjusted by the coil of the electromagnetic separating device.

In another refinement, the control device is designed to generate the triggering signal for the switching device temporally after a predetermined lower threshold value and before a predetermined upper threshold value for the duration after the detected zero crossing. time. In other words, therefore, a time interval is predetermined in which the control device actuates the switching device. The threshold values can be stored in the memory of the control device. As a result, the electromagnetic disconnecting device of the electrical protective device can be actuated particularly precisely.

It is also advantageous if the control device is designed to determine a predetermined lower threshold value as a function of the current operating temperature of the electromagnetic separation device. The control device can be connected to a temperature sensor which is coupled to the electromagnetic separation device. As a result, the electromagnetic separating device can be actuated particularly reliably.

In one specific embodiment, the control device is designed to generate a triggering signal for the switching device as a function of the triggering time of the electromagnetic disconnecting device. The triggering time corresponds to the time period between the moment when the electromagnetic isolating device is connected to the voltage and the moment until the electrical line is electrically disconnected by means of the electromagnetic isolating device. By taking into account the triggering time of the disconnecting device, reliable operation of the electrical protective device can be guaranteed.

In one refinement, the control device is designed to determine the zero crossing as a function of an average value and/or an effective value of the voltage. In addition, the voltage can be rectified before detection by the control device. The control device can have an analog-digital converter which is connected to the computing device. The zero crossing of the voltage can thus be determined in a simple manner.

In another embodiment, a voltage divider is connected between the control device and the electrical line. It can thus be achieved that only a partial voltage of the voltage falls on the control device. This partial voltage, whose amplitude can be only a few percent of the voltage amplitude, can be detected simply by means of a calculation device in the control device or conventional electronic components.

A method according to the invention for operating an electrical protection device comprises providing an electrical circuit, providing an electromagnetic disconnection device configured to electrically separate the electrical circuit when a voltage is applied, providing an electromagnetic disconnection device configured to apply a voltage to the electromagnetic disconnection device in dependence on a trigger signal switchgear on, by means of a control device detecting the presence of a fault current and/or an arc in/on an electric line, by means of a control device generating a trigger signal for the switching device in the presence of a fault current and/or an arc, by means of a control device The zero crossing of the voltage is detected and a triggering signal for the switching device is generated by means of the control device as a function of the detected zero crossing.

The advantages and improvements previously described in connection with the circuit arrangement according to the invention can be transferred in the same way to the method according to the invention.

Preferably, the trigger signal for the switching device is generated by the control device temporally after a predetermined lower threshold value and before a predetermined upper threshold value for the time period after the detected zero crossing.

In one specific embodiment, a predetermined upper threshold value, before which the triggering signal for the switching device is generated, is ascertained by means of static and dynamic force measurements on the electromagnetic separating device. Corresponding measurements on the electromagnetic separation device can be carried out during the design of the circuit arrangement. The triggering time of the electromagnetic separating device can thus be reliably determined.

In another specific embodiment, a predetermined lower threshold value after which the triggering signal for the switching device is generated is ascertained on the basis of calculations and/or load tests carried out on the electromagnetic isolating device. Different values of the voltage amplitude or temperature influences can also be taken into account here. Depending on the ambient conditions, the electromagnetic separating device can thus be operated particularly reliably.

Description of drawings

The invention will now be explained in detail with reference to the drawings. In this case, the single figure shows the circuit arrangement in a schematic illustration.

The examples described in detail later are preferred embodiments of the present invention.

Detailed ways

The drawing shows a schematic diagram of a circuit arrangement 10 for an electrical protective device. This electrical protection device can be a fault current protection device (Residual Current Detector: residual current detector, RCD) or a fault arc protection device (Arc Fault Detection Device: arc fault detection device, AFDD). The circuit arrangement 10 has a first electrical line 12 and a second electrical line 14 . The electrical lines 12 , 14 are connected to an electrical supply (not shown here), for example to an energy supply network. A voltage U, in particular an alternating voltage, is applied between the two electrical lines 12 , 14 . In this case, the second electrical line is connected to the ground terminal 20 .

Furthermore, the circuit arrangement 10 has an electromagnetic isolating device 16 with a coil L1 and a push rod, not shown here. The electromagnetic separation device 16 is established according to the moving coil principle. If current flows through coil L1 , the plunger is moved and the corresponding contact in electrical line 12 is opened. The electrical line 12 is thus electrically separated from the supply or the voltage U.

Furthermore, the circuit arrangement 10 has a switching arrangement T1. The switching device T1 can be designed, for example, as a thyristor. The two electrical lines 12 and 14 can be connected by means of a switching device T1. This has the effect that current flows through coil L1 and electrical line 12 is disconnected. Furthermore, a first diode D1 is provided, which is connected in series with the coil L1. The current flowing through the coil L1 can be rectified by means of the diode D1. A second diode D2 parallel to the coil L1 in the blocking direction prevents the build-up of an overvoltage due to the current flowing into the coil L1.

Furthermore, the circuit arrangement 10 has a control device 18 . Depending on the application, fault currents or arcs in the electrical lines 12 , 14 can be detected by means of the control device 18 . In order to detect a fault current or to detect an arc, an external detection device can also be provided, which transmits a corresponding signal to the control device 18 in the event of a fault current or an arc. If a fault current and/or an arc is detected, a trigger signal trig is output by means of the control device 18 . This trigger signal trig is transmitted to the switching device T1. After receiving the trigger signal trig, the switching device 18 is closed, whereby the voltage U is applied to the coil L1 and current flows through the coil L1 . This causes the plunger to move and the electrical line 12 to be separated. If the switching device T1 is designed as a thyristor, the control signal trig can be transmitted as a current or a current pulse to the gate terminal of the thyristor, whereby the thyristor is ignited and switched into the conducting direction.

The control device 18 is connected to the electrical line 12 in the present exemplary embodiment. This makes it possible to monitor the voltage U by means of the control device 18 . For this purpose, the control device 18 is connected via a voltage divider 22 . The voltage divider 22 includes two resistors R1 and R2 connected in series. By means of the series connection of the two resistors R1 and R2 , the electrical power can be correspondingly distributed among the two resistors R1 and R2 . Instead of resistors R1 and R2, it is also possible to use only one resistor. In addition, voltage divider 22 includes a resistor R3 in series with resistors R1 and R2. Via the voltage divider 22 , only a partial voltage of the voltage U or of the voltage rectified by the diode D1 is transmitted to the control device 18 . For example, the resistors can be selected such that a partial voltage of 0.5% of the amplitude of voltage U falls on control device 18 .

Control device 18 is designed to detect a zero crossing of voltage U. For this purpose, the control device 18 has an analog-to-digital converter, by means of which a partial voltage of the voltage U can be digitized. Furthermore, the control device 18 can have a computing device in the form of a microcontroller, an ASIC or a comparator, by means of which the zero crossing of the voltage U is determined from the mean or effective value of the partial voltages falling on the control device 18 .

If the electromagnetic separating device 16 or the coil L1 is connected to the voltage U at any time, the current flows through the coil L1 until the voltage U reaches the next zero crossing. This means that the current flows through the coil L1 at a maximum for the duration of the half-wave. The duration of the half-wave is 10 ms for a voltage U with a frequency of 50 Hz. From the cycle duration T, the voltage U, the angular frequency ω, the time t and the resistance _RL of the coil L1, the maximum energy absorption E _max formed here can be calculated:

。

.

有关的能量吸收

： With the aid of the control device 18 , the switching device T1 can now be actuated as a function of the zero crossing of the voltage U. In particular, the switching device T1 can also be triggered temporally after a predetermined duration by means of the control device 18 . Instead of the duration, it is also possible to assign a phase angle α. Calculate the phase angle with

related energy absorption

:

。

.

、即在电压U的过零点之后5ms的持续时间的情况下触发开关装置T1，则能量吸收可以减少二分之一。如果在115°的相位角

或在过零点之后约6.3ms的持续时间的情况下借助控制装置18实现开关装置T1的触发，则能量吸收可以减少四分之三。 If the control device 18 is at a phase angle of 90°

, ie in the event of triggering of the switching device T1 for a duration of 5 ms after the zero crossing of the voltage U, the energy absorption can be reduced by a factor of two. If at a phase angle of 115°

Or in the event of a triggering of the switching device T1 by means of the control device 18 for a duration of approximately 6.3 ms after the zero crossing, the energy absorption can be reduced by three quarters.

Furthermore, it is also possible to predetermine a time interval after reaching the zero crossing of the voltage U in which the control device 18 activates the switching device T1 . The alternative time intervals can also predetermine angular intervals. That is to say a lower threshold value and an upper threshold value of predetermined duration, wherein the control device 18 triggers the switching device T1 in the time interval between the lower threshold value and the upper threshold value. In this case, the activation duration of the electromagnetic separating device 16 can also be taken into consideration. The threshold values can be stored in a memory of the control device 18 dedicated to the electromagnetic separation device 16 , eg in the form of a mathematical function or a table. The threshold value may have been ascertained previously by calculations and measurements carried out on the electromagnetic separation device 16 .

The upper threshold value for the duration can be ascertained in advance on the basis of static or dynamic force measurements on the electromagnetic separating device 16 . The upper threshold of the duration can be obtained through theoretical calculation or load test. Furthermore, the control device 18 can be designed to currently detect the temperature of the electromagnetic separating device 16 and adapt the lower time threshold value as a function of this temperature.

By controlling the triggering of the switching device T1 , it is possible to reduce the duration of the current flowing through the coil L1 and thus reduce the energy absorption of the coil L1 . This enables the use of an electromagnetic separating device 16 with a coil L1 having a smaller number of windings and/or a smaller wire cross section. Costs and installation space can thus be saved.

List of reference signs

10 circuit device

12 Lines

14 Lines

16 Separation device

18 control device

20 ground terminal

22 voltage divider

Dl diode

D2 diode

L1 Coil

R1 resistor

R2 resistor

R3 resistor

trig trigger signal

T1 switchgear

U voltage.

Claims (11)

1. A circuit arrangement (10) for an electrical protection device, having: - electrical lines (12), - an electromagnetic separating device (16) designed to electrically separate the electrical lines (12) when a voltage (U) is applied, - a switching device (T1) designed to apply the voltage (U) to the electromagnetic disconnecting device (16) as a function of a trigger signal (trig), - control means (18) for detecting the presence of fault currents and/or arcs in/on said electrical line (12) and for generating in the presence of fault currents and/or arcs for the trigger signal (trig) of the switching device (T1), It is characterized in that, - The control device (18) is designed to detect a zero crossing of the voltage (U) and to generate a trigger signal (trig) for the switching device (T1) as a function of the detected zero crossing. 2 . The circuit arrangement ( 10 ) as claimed in claim 1 , characterized in that the control device ( 18 ) is designed to generate a signal for The trigger signal (trig) of the switching device (T1). 3 . The circuit arrangement ( 10 ) as claimed in claim 1 , characterized in that the control device ( 18 ) is designed to be temporally after a predetermined lower threshold value and before a predetermined upper threshold value. 4 . A trigger signal (trig) for the switching device (T1) is generated for the duration after the detected zero crossing. 4 . The circuit arrangement ( 10 ) as claimed in claim 3 , characterized in that the control device ( 18 ) is designed to determine the predefined lower threshold of . 5 . The circuit arrangement ( 10 ) as recited in claim 1 , characterized in that the control device ( 18 ) is designed to generate an activation time for the electromagnetic isolating device ( 16 ) as a function of the triggering time. 6 . The trigger signal (trig) of the switching device (T1) described above. 6 . The circuit arrangement ( 10 ) as claimed in claim 1 , characterized in that the control device ( 18 ) is designed to determine the the zero crossing. 7. The circuit arrangement (10) as claimed in one of the preceding claims, characterized in that a voltage divider (22) is connected between the control device (18) and the electrical line (12). 8. Method for operating an electrical protective device by: - provision of electrical lines (12), - providing electromagnetic separating means (16) configured for electrically separating said electrical lines (12) upon application of a voltage (U), - providing switching means (T1) configured for applying a voltage (U) to said electromagnetic separating means (16) in dependence on a trigger signal (trig), - detecting the presence of fault currents and/or arcs in/on said electrical line (12) by means of the control device (18), and - generating a triggering signal for the switching device (T1) by means of the control device (18) in the presence of a fault current and/or an arc, It is characterized in that, - detection of zero crossings of said voltage (U) by means of said control means (18), and - Generating a trigger signal (trig) for the switching device (T1) by means of the control device (18) as a function of the detected zero crossing. 9 . The method according to claim 8 , characterized in that the switching device ( T1 ) is generated temporally after a predetermined lower threshold value and before a predetermined upper threshold value by means of a control device ( 18 ). The trigger signal (trig) lasts for the duration after the detected zero crossing. 10. The method according to claim 9, characterized in that the predetermined upper threshold value is determined by static and/or dynamic force measurement on the electromagnetic separation device (16), and in the predetermined A trigger signal (trig) for the switching device (T1) is generated before an upper threshold of the upper limit. 11. The method according to claim 9 or 10, characterized in that the predetermined lower threshold value is obtained according to the calculation and/or load test performed on the electromagnetic separation device (16), in the A trigger signal (trig) for the switching device ( T1 ) is generated after a predetermined lower threshold value.

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