EP0304456A1 - Overcurrent protection device for power generating plants for residential and industrial buildings and similar buildings - Google Patents

Abstract

Standard VDE 0100, section 732 / 03.83 is applied when establishing building entrances for installations (A) for supplying current to residential buildings. This standard provides, at the building entrance (E), protective devices (Ü) for power supply lines (1) against current overcurrents, such as fuses (Si), in the event of short -circuits in the consuming part of the installation. In order to protect the power supply line beyond the building entrance during short-circuits in the building connection line (1), an additional device (Ü ') for protection against overcurrents current is arranged in each current supply line or cable, just after their derivation (NA) from the distribution network (N). Each protection member (Ü ') has the form of a fuse switchable by a switch (L) for protection of electric lines actuated by a corresponding control unit (ST). The fuse disconnects excessive currents detected by an overcurrent detector (D) and reconnects the supply current by means of a monitoring device (O) which indicates the elimination of the causes of the overcurrent. The protection devices of a building connection line against current currents are arranged in a single protective housing (G). The switch (L) for protecting the current supply line has the form of an electromechanical contactor (Sch) for impedance-capacitance coupling (Dr), of a semiconductor coupling contactor with two antiparallel network thyristors (Th1, Th2) or a serial connection of these two possibilities, with control units appropriate for each case.

Description

 Overcurrent protection device for power supply systems of residential and commercial buildings and the like

The invention relates to an over-current protection device for power supply systems of residential and commercial buildings and similar buildings, in particular for power supply systems in residential buildings with an over-current protection device for protecting the power lines in the area of house introduction, which are connected to the distribution network by means of house connection line power lines branching off from its phason conductors.

Part 732 / 03.83 of the German standard, identified as VDE regulation, series DIN 57 100 VDE 0100, is used in connection with the corresponding other standards of this series for the establishment of so-called housings as part of high voltage systems with electrical voltages up to 1,000 volts. Accordingly, a house entry includes house entry line or house entry cable, both referred to below as lines that start at the entrance tunnel into the building, and the associated house terminal, which forms the transfer point to the consumer system. Each house entry contains in the house junction box the necessary overcurrent protection elements, mostly tire-shaped fuse pieces, the bare cross-section for current conductors of the house entry line is dimensioned according to the nominal current of the overcurrent protection elements, and the house entry solution is laid so that in the event of an arcing short the line leakage without risk of building expansion can. Does this also go with the line protection that is actually intended for the consumer bankruptcy on the house entry line and, if applicable, on the house connection line, it can only be effective if there is a short circuit or if an overcurrent is caused in the consumer system.

When developing development areas for new settlements on the periphery of large cities and municipalities as well as when building new urban and urban districts, the electrical distribution network for the power supply has been expanded to an appropriate extent, in some cases newly built. At present, in the larger municipalities that have a local power plant, not only has the distribution network been expanded with an increased number of main mains lines, which lead to different groups of consumer systems with partly different nominal voltages, but also the number of these main mains lines to the individual ones Building connection lines branching off from buildings is already considerably large, especially in residential areas. Here, the house connection lines, which are connected in parallel on a main network line, are located close to each other, similar to those in the streets of cities. In view of the development level that has been achieved in large numbers when the distribution networks for the power supply of buildings have grown, the possibility can no longer be excluded that, for example, the house connection lines laid as underground cables are at risk. When using shovel excavators for excavation work as well as other civil engineering tools, which are used for repairs to pipelines in the ground, which are frequently and frequently necessary, or when laying cables, the sheath of a house connection cable can be damaged or broken through, so that the electrical conductors are short-circuited. If, as a result of a cable fire or arcing short circuit, the main power line is short-circuited and the power supply to the houses connected to it is interrupted. The possibility of endangering house connections in overhead line networks, for example due to lightning strikes, storms on the roof stands on buildings and heat from a building fire, is also not excluded. As exceptional The cause of a risk or destruction, particularly of house connection lines, is the use of force on buildings, streets and paths.

By the invention characterized in the claims, an overcurrent protection device of the type specified for power supply systems, in particular residential buildings, is created with which a line contactor for house connection lines and also for main network lines is achieved, which is in the area between the distribution network and the Overcurrent protection devices of the house guides caused overcurrent or short circuit to come into effect quickly.

The invention consists essentially in the fact that an overcurrent protection element is additionally provided in each current conductor of a house connection line, and that shortly after the branching of the house entry line from the distribution network, which protection element contains a line circuit breaker which actuates this circuit breaker control unit, which can have a signal amplifier that can be used with Power is supplied from the distribution network, an overcurrent detector, from which the control unit receives a signal that controls the switch-off of the current (consumer current) by means of the circuit breaker if an overcurrent occurs in the relevant current conductor of the house connection line, and a monitoring device, from which the control unit receives a signal the signal controlling the reclosure of the current is supplied if the cause of the overcurrent has been eliminated.

This creates an overcurrent protection device with switchable protective devices that are controlled by overcurrent and overcurrents, short circuits in the house connection line or quickly switch off in the house entry line. A short-circuited ventilation system is thus protected in good time against the risk of high current loads and at the same time the power supply to the consumer systems connected to the distribution network via short-circuit-free lines is maintained without interruption. Likewise, the main power supply line is protected against overload in good time, so that an emergency shutdown of the affected network sector is avoided. For use in lines in overhead line networks as well as in lines in cable networks, the superutro protection devices of all current conductors of a house connection line are housed in a common protective housing. The same is designed to be shock and impact resistant, hermetically sealed and has an input and an output terminal for each current conductor and for the neutral conductor of the house connection line. In certain applications it may be appropriate to use a common protective housing for the overcurrent protection devices of two or even more chewing lines.

Embodiments of the invention are characterized by different versions of the switchable Uberstromocnutzorganes. characterized in the invention, which are explained in the description below using examples and are outlined as follows. 1 An electromechanical contactor serves as a circuit breaker for the overcurrent protection device. The associated control unit contains two relay current circuits connected to the distribution network as a current source for electromagnetic actuation, one for the separation and one for the closing of the contactor contacts, each with a semiconductor switching element and an excitation coil in series connection. The semiconductor switching element of the relay circuit for the separation of the Schsltachützkontakte is by a signal from the overcurrent detector and / or a Short circuit signal generated in the house connection line driven to switch on the excitation current. The semiconductor switching element of the relay circuit for closing the contactor contacts for reclosing the consumer current is activated by a signal from the monitoring element in order to switch on the excitation current, namely by the signal recurring after the cause of the overcurrent or the short circuit has been eliminated

For electromagnetic actuation with excitation direct current, the relay circuits are connected to the distribution network via a mains rectifier. In order to be able to separate the contactor contacts with shorter actuation times when the current is switched off, the relay circuit provided for this purpose is connected in a known manner to a current source with a DC voltage which is greater than the mains rectifier voltage. The same measure can be carried out for the relay circuit for the closing of the contactor contacts, in order to be able to close the same also with shorter actuation times than without this measure when the current is switched on. 2nd

A semiconductor contactor with two line thyristors connected in parallel in opposite directions serves as a line protection switch. The associated control unit contains a control pulse generator with an output common to both hetzthyristors, to which a semiconductor switch is connected in parallel. The control pulse generator is connected to the distribution network as a current source for the formation of control pulses, by means of which the network thyristors of the circuit breaker are controlled in a current-conducting manner for passage of the alternating current (consumer current). In the event of an overcurrent or short circuit in the house connection line, one of the two network thyristors causes the semiconductor switch mentioned to be turned off by a signal from the overcurrent detector or by a signal from a short-circuit detector, and the control output is thus kept short-circuited until a signal from the monitoring element is present, in order to switch off the consumer current by self-extinguishing is released to restart the consumption current, whereby the signal of the overcurrent detector is terminated.

3 In this embodiment of the switchable overcurrent protection device, the circuit breaker consists in the fact that the series connection of an electromechanical contactor and a choke is connected in parallel with a semiconductor contactor with two sensibly parallel line thyristors. The semiconductor contactor is used here as auxiliary switching means for, in particular, disconnecting the contactor contacts from one another when the current is switched off and is free from arcing. At the choke of the series connection mentioned, a pulse-shaped voltage is formed by the current rise when an overflow arises, which is applied to the semiconductor contactor and enables the ignition of a line thyristor, so that it is uno / or by a signal from a short-circuit detector, preferably of the monitoring body used as a soloner is turned on in a current-conducting manner. The same signal fed to the control unit of the semiconductor contactor is simultaneously fed to the control unit of the electro-mechanical contactor in order to control the semiconductor switching element of the rice circuit for the separation of the switching contactor contacts and to switch on the excitation current therefor. The control units of the Melbleirey contactors. This sigual must, in order to continuously control the line thyristors, be supplied for longer than the switch-off time of the electromechanical contactor, so that the line thyristors remain conductive for the current they are switched on and the arm contactor contacts are kept current physically until they are separated. The signal of the monitoring device that is emitted after the cause of an overcurrent or short circuit has been eliminated is fed to the control unit of the electromechanical contactor in order to control the semiconductor switching element of the relay current circuit for closing the switch protection contacts and to switch on the excitation current for this. The same signal can be fed to the control unit of the semiconductor contactor at the same time if the switch contacts of the electromechanical contactor are also to be closed without arcing. For this, the line thyristors of the semiconductor contactor must pass through the

Signal is kept conductive for longer than the switch-on time of the electromechanical contactor.

The invention is explained in more detail below by means of exemplary embodiments with reference to the drawing, from which one version of the overcurrent detector and one of the monitoring elements can be seen. It shows

1 shows a schematic representation of an overcurrent protection device according to the invention for a high-voltage system constructed in accordance with VDE 0100 Part 732 / 03-83. FIG. 2 shows the block diagram of an overcurrent protection device according to the invention in accordance with embodiment 1 and

3 shows the block diagram of an overcurrent protection device according to the invention in accordance with the embodiment 2 and

4 shows the block diagram of an overcurrent protection device according to the invention corresponding to embodiment 3 outlined above. In FIGS

Three-phase line shown. Identical elements and components of the different versions of the overcurrent protection are provided with the same reference symbols in the figures.

In FIG. 1, only the part provided with reference symbol E, namely the house entry, a high-voltage system for the power supply of a residential building is shown.It comprises the house entry line 1 starting at the entrance to the building H and the house junction box HK, which contains overcurrent protection elements Ü, which strip-shaped fuses are Si. The part of the installation in FIG. 1 to the right of the branch V of the house entry line to the individual consumer groups is called the consumer installation, it is indicated by the reference symbol A. In the house connection line 1 ', through which the house entry line 1 is connected to a main network of the distribution network N, additional cross-protection devices U' are inserted, which, in contrast to the visual protection devices U, can be activated. According to Figure 1, the overcurrent protection devices Ü 'are used immediately behind the branch line A _{N of} the line 1' from the main main line, namely an over-current protection device Ü 'in each conductor 1 _R ', 1 _S ', 1 _T ' of the house connection line 1 ', which also how the main network line of the distribution network N and the house entry line 1 is three-phase, that is to say contains three phase current conductors in addition to a phase conductor MP. Branches A _{N of} further three-phase house connection lines 1 'from the same main line are shown in FIG. 1 on the right. Each of these lines leads to a different building and contains the same switchable overcurrent protection devices Ü '.

An overcurrent protection device according to the invention can be switched by using a circuit breaker L as a component, which is opened by means of a control unit St, which may contain signal amplifiers, and thereby switches off the Stroit in the current conductor in which the overcurrent protection device is inserted as soon as this current conductor leads to overcurrent 1 and the line circuit breaker is closed and thereby switches the current in the conductor back on as soon as the cause of the overcurrent has been eliminated. Upper current is detected by a current detector D with a current sensor W _st and sent to one

Input I of the control unit St signals. A signal is formed by a monitoring device Ö as a criterion for eliminating the cause of the overcurrent, which is fed to an input II of the control unit. The circuit breaker is actuated in each case by means of an operative connection with the control output III from St in the corresponding sense.

The constituents L, St, O and D mentioned with w _st each form a switchable overcurrent protection device. The three switchable overcurrent protection devices in the current sensors 1 _R ', 1 _S ', 1 _T 'of the three-phase house connection line 1' are enclosed in a protective protective housing 0, the main features of which are given above, as can be seen from FIGS. 2 to 4 is where an overcurrent protection device Ü of three identical protection devices is shown each time.

The overcurrent protection device S _R ^' shown in FIG. 2 contains an electromechanical contactor Sch as a line circuit breaker with a switch contact pair K, K shown in the closing division, consisting of a fixed and a pivotable switch contact. The associated controller St consists of two relay circuits for electromagnetic actuation, each with an excitation coil e ₁ or e ₂ and one contactless relay switching element, namely thyristors T1 and T2, in series connection, which are connected in parallel at the output of a mains rectifier G1 feeding them. This is connected via a network transformer Tr to the network phase (here R), from which the current conductor to be protected (here 1 _R ') branches off.

The excitation poles are ignition windings, each with a rod-shaped actuating magnet m1 or m2 that can be moved in and along the coil axis, which is mechanically coupled with a plunger that strikes the pivotable gold contact K in the manner of an impact anchor. In the ϊ'ig. 2, the plunger is illustrated by an arrow head directed against K and the mechanical coupling by an action line. The excitation current in the coil e1 is switched on by an ignition current of the overcurrent detector described in more detail below, which is supplied to the control electrode of the thyristor T1, which forms the input I of St, and thereby triggers the actuation process for separating the switching contacts K by means of the associated plunger. An ignition signal of the monitoring device O described in more detail above is supplied to the control electrode of the thyristor T2, which forms the input II of St, in the coil e2 the excitation current is switched on, which triggers the actuation process for closing the switching contact contacts K by means of the assigned plunger. The lines of action mentioned each individually form an actuation output, designated III, of the St. unit St. According to FIG. 2, the two relay circuits with the thyrist. T1, T2 a push-pull circuit which is activated each time by a signal from the overcurrent detector when the excitation current is switched on in the coil e1, and then by a signal from the monitoring device 0 the excitation current in the coil e2 is switched on, with the disappearance of which the push-pull circuit is deactivated If it contains a quenching capacitor C _L in FIG. 2 and if the line rectifier G1 supplies a gap-free DC voltage or if the signal of the detector D is extended until the signal of the organ 0 is emitted, then the excitation current switched on by means of the thyristor T1 flows until the switch on .Excitation current by means of the thyristor T2, whereby T1 is forcibly extinguished, and this excitation current flows until the excitation current is switched on by means of the thyristor T1, which in turn forcibly extinguishes T2, and so on. This has the advantage that the switch protection contacts K, K are securely held by the above-mentioned actuating means, each in their own switching position, regardless of existing or non-existent means which are common in mechanical switching, and also switch over to each other switching position is accelerated by the mutually supportive actuating means.

The same advantages result if the thyristors T1 and T2 are replaced by switching transistors as semiconductor switching elements and the signals from D and O are extended for actuation until the next one (from 0 and D) is emitted, even if the DC voltage is not gap-free Relay circuits feeding the mains rectifier. The measures mentioned, with which an accelerated switching of the contactor contacts is achieved, are supplemented in the overcurrent protection device according to FIG. 2 by using the charging circuit shown on the left next to the figure with a controlled charging switch S _L for a capacitor C, the contactor contacts each with a shorter actuation time than be separated from each other without a charging circuit, so that a correspondingly lower response delay of the actuating means of the associated Helais circuit is achieved. The charging circuit is connected by a rectifier to an additional secondary winding wz of the Hetztransforαators Tr, which is designed for a voltage which is several times higher than the voltage supplied to the Hetz rectifier Gl. An increased power-to-weight ratio of the transformer is not necessary for this. The capacitor C is charged to a correspondingly high DC voltage via a resistor and the charging switch S _L , which is dimensioned for a desired short actuation time, for example 10 to 20 milliseconds. Both electric circuits are connected to the high DC voltage at output a of the charging circuit at the point labeled a.

The above-mentioned overcurrent detector D and, likewise, the monitoring device O also form the other main parts of the overcurrent protection element O 'shown in FIG. In this, as can be seen, the short line or cable section of the current conductor 1 _R 'between the contactor contact pair K, K and the output terminal Kl _{A of the} same serves as a current sensor w _st for detecting overflows occurring in the current conductor 1 _R '. There are two on the deca line section

Sensor lines f connected, which are connected via a discriminator or filter circuit F to the input of a rectifier bridge Gr according to Graetz. At the output of Gr a threshold level st is connected, which is arranged upstream of a flip-flop k with an amplifier. The components F, Gr, st, k together with W _{st form} the overcurrent detector D. Its output is the output of k, the is connected by signal lines once to the control input I of St, that is, to the control element e of the thyristor T1, and once to the control input b of the charging circuit mentioned. The filter circuit F is specially designed for passage of the inductive component of the voltage tapped at the line section of 1 _R 'and the threshold value of the stage st is dimensioned so high that it is not greater than the voltage value of the inductive component, which corresponds to the increase di / dt of Current in the house connection line 1 _R 'Dei corresponds to a short circuit. Lamit is only given a signal of the threshold level in the event of a short circuit, thereby generating the ignition signal at the output of the trigger circuit k for triggering the actuation process for separating the switching contacts from Sch and for switching on the charging current in the charging circuit for the capacitor C. The ignition signal is generated when a short circuit is cleared, so that the short-circuit current rises during the actuation process triggered thereby and is switched off by the separation of the switch contacts before it becomes so great that the voltage of the distribution network is inadmissible when the short-circuited house connection line is branched off sinks far. An overcurrent detector D, as described above, is additionally set up for the detection of overcurrents which do not occur as a result of a short circuit, for example with an additional threshold value stage, which is connected on the input side via an additional rectifier bridge to sensing lines which are connected to the filter circuit F by the Branch lines f, this is on the output side

Threshold stage connected to the input of flip-flop k. Their threshold value is dimensioned such that an ignition signal is only generated when an over-litter reaches a predetermined value. The monitoring device O of the overcurrent protection device according to FIG. 2 consists essentially of a voltage divider, which is formed by the two primary windings w1, 2 of two savings converters W1, W2 that have failed. This voltage divider connects inside the protective housing G of U _R 'the input terminal Kl _E dun Süroßleiters 1 _R ' with the output terminal Kl _{A of} the neutral conductor MP, it is thus connected to the existing phase voltage between the phase conductor K and Mi (star voltage) . Its voltage division point formed by the connection of the primary windings w1, w2 is connected to the output terminal of the current conductor 1 _R '. A signal converter is connected to the secondary winding w _{s of} the voltage converter W2, via the primary winding w2 of which the current conductors 1 _R 'and MF are connected to the output connecting terminals Kl _A. This contains at the input a Glelonrichterbrücke Gr and downstream a converter stage U, the output of which is connected to the control input II of the control unit St, that is to say the control electrode of the THYRISTOR I2. During the power supply to the house connection (switch ohütz Sch is closed), there is an alternating voltage on the secondary winding w _s with an excess ratio due to the excess W2 determined small amplitude value suitable for signal formation as part of the amplitude value of the line phase voltage. At the secondary winding w _a , the AC voltage disappears when a short circuit occurs in the house connection line 1 _R ', and it does not exist for a long time or is too small for signal generation when the house connection line is short-circuited or bridged with low resistance. The alternating voltage at w _s returns as soon as the short circuit or the cause of an overcurrent has been eliminated. Due to the components Gr and U of the signal converter mentioned, this alternating voltage is converted into a rectangular control signal for the thyristor T2 of the control unit St, by which the excitation current in the excitation coil e2 is switched on and the actuation process for closing the contactor contacts for reactivating the current is triggered. The length of the control signal can expediently be limited to a period of time, starting when the alternating voltage returns to w _s , that is not shorter than the actuation time for the closing of the Switching contact K, K is so that the excitation current is switched off after the same. Control signals with a limited period of time, formed by a monitoring device, as described above, as well as control signals with a limited period of time, formed by an overcurrent detector D, serve the purpose mentioned if transistors as semiconductor switching elements T1 and T2 are actuated instead of thyristors or if thyristors or thyristors with individual quenching that can be switched off are switched off an adapted control unit St can be used.

The signal converter of the monitoring device can finally contain a flip-flop for signal generation and an upstream threshold value stage instead of a converter stage U, so that by submitting a sufficiently high threshold value, the delivery of a control signal and thus closure of the contactor contacts K, E is correspondingly prevented if a short circuit or Cause of an overcurrent has not been completely eliminated. In the embodiment of an overcurrent protection element _R 'shown in FIG. 3, a semiconductor contactor with two line thyristors Th1, Th2 connected in parallel in opposite directions is used as line circuit breaker L instead of an electromechanical contactor, as described above on page 5 under point 2 and further explained. According to FIG. 3, the associated control unit St contains a control pulse generator, which is connected via the voltage converter W2 of the monitoring element 0 to the distribution network N, which serves as a current source for forming control pulses. For this purpose, the voltage converter for transferring the required power to the control pulse generator is designed like a mains transformer with a corresponding transmission ratio Depending on the design of the voltage converter W2, the monitoring device O is used in its intended function and at the same time as a short-circuit detector. An overcurrent detector D is therefore the one described here An overcurrent protection device is only provided if the consumer current is to be switched off when a specified overcurrent value is reached. FIG. 3 shows this overcurrent detector with its components f, Gr, st, k for the sake of completeness, but without connection to an ammeter w _st by means of the sensing lines f. A signal from this overcurrent detector D when an overcurrent occurs in the phase conductor 1 _R 'of the house connection line, the semiconductor switch T _k , which is parallel to the output III of the control unit St, here a switching transistor, is controlled in a current-conducting manner and the control output III is thereby short-circuited. The line thyristors Th1, Th2 of the line circuit breaker L are then no longer supplied with control pulses, so that their current conduction is ended by self-extinguishing and the consumer current is switched off. The switching transistor T _k can also be controlled in a current-conducting manner by a signal from a short-circuit detector. The signal from the monitoring device O for switching the consumer current on is branched off from D via a signal line r to the reset input of the multivibrator k, whereby T _{k is} blocked, so that the control pulses are then fed back to the line thyristors of the circuit breaker switch L. Controllable control pulses are generated by rectification and conversion of the down-converted phase alternating voltage u _R , which is transmitted to the secondary winding w of the voltage converter W2 and is fully connected to the consumer, generated by means of the rectifier bridge Gr and the converter stage U. These form the control pulse generator and, like in the embodiment of an overcurrent protection device shown in FIG. 2, are subordinate components of the monitoring device 0. Without further means and measures, the monitoring device is also designed as a short-circuit detector with the voltage converter V2 implemented as the mains transformer of the control pulse generator. A short circuit occurs in the house connection Line 1 'on, the phase change voltage u _R at the voltage converter W2 disappears, so that no more control pulses are generated. The line thyristors of the circuit breaker are automatically extinguished when the consumer current crosses zero and the consumer current is switched off. Even while the consumer current changes into the temporal current curve in the event of a short circuit, the amplitude of the phase alternating voltage across the voltage converter W2 becomes so small that no controllable control pulses are formed.

After the consumer current has been switched off, the full phase alternating voltage u _{R is applied to} the voltage converter W1 of the monitoring device 0, as long as the short circuit persists. After the short circuit has been eliminated, it is temporarily on the series circuit of the voltage transformer primary windings w1 and w2 which forms a voltage divider as long as the line thyristors of the circuit breaker L are not current-conducting. The number of turns ratio w2 / e1 of the voltage transformer primary windings is chosen so that the voltage component of u _R on the primary winding w2, taking into account the transmission ratio w2 / w _s , of the converter W2 is sufficiently large for the generation of ignitable control pulses. Finally, if the line thyristors Th1 Th2 conduct current, then the full phase AC voltage u _{R is} again on the primary winding of the converter V2.

In a further embodiment of an overcurrent protection element U _R 'according to the invention, shown in FIG. 4 and above, page 6, described under item 3 and explained in more detail, the line circuit breaker L consists in the combination of a semiconductor contactor

Figure 3 and an electromechanical contactor after

Figure 2 connected in series with a choke (series choke

Dr), which are connected in parallel to each other. In this embodiment, the consumer current is kept permanently closed via the electro which is kept closed for normal power supply Contactor supplied. The semiconductor contactor serves as auxiliary switching means so that in the event of a short circuit or an overcurrent in the house connection line, the contactor contacts K, K are separated from one another with the lowest possible current load or even without arcing.

In both cases, the semiconductor contactor is made conductive by the signal from the overcurrent detector D and / or the monitoring element O, the line thyristor being stressed in the forward direction by the voltage pulse existing at the inductor Dr when the Eurcurrent current i _k increases, is ignited and turned on to conduct electricity. Thereby, the choke is turned on is still closed contactor vision for the short-circuit current einjαiederohmiger shunt, so that on this side current branch and the (short-circuited) to the neutral conductor MP and the HausansSchlußleitung 1 _R 'of the largest portion of the rising Kurzsc & lußstromes flows during the current branch with Sch and Dr is burdened with a correspondingly small proportion, which also rises much more slowly. The signal from the overcurrent detector and / or the monitoring member is simultaneously fed to the control unit St of the electromechanical contactor in order to switch on the excitation current of the relay circuit for the separation of the contactor contacts. If at the end of the switch-off time of the contactor Seh its contacts are separated from each other and the small part of i _{k is} switched off, then flows. the portion of i _k commutated on the bypass branch continues and is switched off by self-extinguishing of the current-carrying network thyristor in the next current zero crossing.

Following the detailed description of the overcurrent protection device according to FIG. 4, as follows, dimensioning rules for a functionally correct design are made from the parallel connection of the current branch with sight and choke Dr and the current branch with the semiconductor contactor existing circuit breaker L in connection with an example (power supply system) explained. In the overcurrent protection device with the line circuit breaker L according to FIG. 4, the control unit St of the electromechanical contactor Seh is designed like that according to FIG. 2, specifically with thyristors T1 and T2 as semiconductor switching elements of the 2 relay circuits in push-pull circuit. The control unit can be assigned a charging circuit, as shown on the left in FIG. 2, for the purpose of additionally reducing the switch-off time of the contactor to 10 msec and shorter if necessary. The control unit for the network thyristors Th1, Th2 of the semiconductor contactor is a signal amplifier with a signal input I, to which signals derived from converter stage U of the monitoring element 0 are supplied, and a control output III to the network thyristors, which are in the same manner as in the corresponding control unit according to Figure 3 can be controlled. The control unit St according to FIG. 4, however, is supplied with current from the mains rectifier G1 via the connection of the 2 relay circuits. An overcurrent protection device according to FIG. 4 can, if necessary, contain an overcurrent detector and a monitoring device, which are then assigned to both contactors Sch and Th2, Th2 together. The overcurrent protection device shown in FIG. 4, on the other hand, contains only the monitoring device 0 and assigned together, which is also used as a short-circuit detector. For this purpose, the control function of the converter stage U is designed accordingly

Example with a signal output, which is connected via a negating flip-flop h, which has a predetermined time constant, to the input I of the control unit St for the semiconductor contactor, and a control output for the thyristors T1, T2 of the control unit St of the contactor Sch. At the control output of U there is a controllable continuous pulse on the secondary winding w _{s of} the voltage converter W2, rectangular with a step-like rear flank when the AC voltage falls below a predetermined value. The control output is once directly with the control input II of St (control electrode of T2) and once via a flip-flop k _u with the Control input I (control electrode of T1) connected. In case of short circuit in the service line 1 _R 'disappearance, the AC voltage at the secondary winding det f _s, so that at the control output of the control U capable pulse duration and the Sig- nalausgang the signal of the converter stage to cancel. As a result, a controllable continuous pulse is fed to the control electrode of T1 and the excitation current is switched on for the separation of the contactor contacts. At the same time, the control unit of the semiconductor contactor is supplied with a control signal for opening the respective ignitable network thyristor for a period of time which is longer than the switch-off time of the electromechanical contactor. After the control signal has ended, the commutation current switched on by means of the semiconductor contactor is switched off by self-extinguishing of the current-carrying line thyristor in the next zero crossing; its re-activation in opposite polarity by means of the second line thyristor does not occur. By eliminating the short circuit, the primary winding of the voltage converter W2 (part of the inductive voltage divider W1, W2) becomes live and the AC voltage on the secondary winding returns. At the control output of stage U, as described above, this results in the control pulses which are controllable for the semiconductor switching element T2 of the control unit Sjz, and at the same time the permanent pulse which receives the semiconductor switching element T1 in a current-conducting manner disappears, while the contactor contacts are separated from one another if the rectifier Gl is one supplying DC voltage.

The excitation current for closing the switching contactor contacts is switched on by the control pulse, which is now fed to the control electrode of the semiconductor switching element Ts2.

With the voltage divider W1, W2, as can be seen from FIG. 4 and FIG. 2, there is a switching means q, for example an electromagnetically remotely operated normally closed contact, which is normally held in the closed position by an excitation current by the contactor contacts, which separate from each other as a result of a short circuit, is brought into the open position, where the contact of q remains as long as the excitation current is interrupted. For this purpose, the excitation circuit is led from q in the form of a cable loop through terminal Kl _A out of the protective housing and laid together with the house connection line II to the house entrance E (see figure 1). This makes it possible, particularly in the case of an overcurrent protection device located in the ground with a mains and house connection line cable, that after repairing a house connection cable destroyed by a short circuit, the contact of the switching means q is restored by restoring the line loop interrupted when the house connection cable is destroyed, without endangering the network Voltage that can be brought into the closed position remotely. The voltage divider W1, W2 is thus connected to the mains voltage and the reclosure of the contactor contacts is initiated. The remote-controlled switching means can also be designed as a semiconductor relay, it can also be used in the embodiment shown in FIG. 3.

An example of a power supply system is that for a local outskirts with 10 house connections, which is supplied with power by a 0.5 km long main line of the distribution network, a low-voltage cable VPK. In the housing estate, 10 parallel wired building connection lines branch off from the main line and lead to individual apartment blocks and groups of apartment houses. Each house connection line is for a nominal current consumption of the connected consumers of 100 A with 220 V connection voltage. designed, and each contains 3 phase connection lines 1 _R ', 1 _S ', 1 _T 'and the neutral conductor MP. Taking into account that short circuits of a phase connection line alone and of the MP can also be caused, each phase connection line of the house connection line must have an overcurrent protection element U '. In the likely case that all three phase connection conductors and the neutral conductor MP become one of the ten by force Wired house connection lines, the phase currents i _R , i _s , i _T in the lines 1 _R ', 1 _s ', 1 _T ' in phase short-circuit currents i _{k) R} , i _{k) s} , i _{k) T} , which in Since the point of the short circuit, start to rise with the respective polarity of the phase currents. The earlier the time of the short-circuit lies during a half-oscillation of a phase current, the higher the phase short-circuit current in question can become during its same half-oscillation within its rise given by the time constant of the short-circuit circuit This means: R _M ohmic line resistance of a phase line ph of the distribution network N, L, the line inductance of ph (ph = R, S, T), 1 _s the inductance of the inductor Dr. If the short-circuit current in one of these lines no longer forms in the event of a short-circuit of the three phase connection lines, because the short-circuit occurs at a point in time too short, for example 30 el, before the end of the relevant half-oscillation of the phase current, it can occur in at least fully form one of the other phase connection lines. Its time profile i _k (t) can be approximated with the simplifying restriction that during the rise time of the short-circuit current the generator voltage E _{ph of} the phase ph of the distribution network has the effective value E _ph constant. It is so large that the effective value of each phase connection voltage affects u _ph for the consumer at the nominal load of the 3-phase network. The relationship

G The time course of the short-circuit current in the relevant phase connection line 1 _p ' _h and in the line of the mains phase again (i _ph (O) is the current value 100 A of the phase current at time t = 0).

In the relationship (1) the influence of capacitive currents and the leakage currents of the three-phase power line (R 3 T MP) as well as the negligibly small ohmic resistance r of the section of the phase connection line between Einanyskiemme Kl _E and output terminal KL _A (Figure 4) is not taken into account. However, it must be taken into account that the time course of the short-circuit current according to relationship (1) during its rise time is influenced by the inductance of the inductor Dr, which in the phase connection lines 1 _p ' _{h of} the nine other house lines connected in parallel from the ten branching from the three-phase mains main line 1 'in which, for example, no short circuits have occurred, with the. The course changed as a result can be data

R _M = 0, 12 Ω, L _M = 0, 125 mH of a 0.5 km long low-voltage cable for the three-phase main line N and with 1 _s =

Represent 0.05 mH as a particular solution for i _k (0) = 100 A. by (2) i _k (t) = (-9, 7E _ph + 95.1) exp-0.654t

+ (0.84E _ph + 4.9) exp-6.19t + 8.33E _ph A From relationship (2) the rate of current rise at the time of the short circuit is determined di _{k / dt (O)} = 0.77E _ph -92, 5 *

It follows that a voltage pulse with the height di, / dt (0) 1 is formed at the inductor Dr at the time of the short circuit. With the data of the present example E _ph = 34-0 V and 1 _s = 0.05 mH, the pulse height is 8.5 V. By the voltage pulse v.άrd biased in the forward direction of the thyristor of the semiconductor contactor, which is in the bypass branch of the electromechanical contactor and the inductor Dr of the short-circuited phase connection line 1 _R ', kept ready for activation of the short-circuit current in this bypass branch. At the same time, the ignition signal of the short-circuit detector 0 is fed to the network thyristors of the semiconductor contactor. The inductance of the inductor Dr is dimensioned according to the value di _k / dt (0) of the slew rate of i _k determined from relation (2), so that the voltage pulse has the pulse height required to open the fired line thyristor. In addition, the choke is designed so that the voltage pulse remains approximately 0.1 mrek long with the pulse height unchanged, so that delayed delays due to inhibition are possible with control times that are longer than the switch-on times of thyristors of 15μsec, for example. A suitable choke, which due to the change -

* A / msec field permeability of its magnetic core with a Glejchstromflutung of 100 A has an inductance of, for example, 0.05 mH, is for practical reasons as a so-called single-core choke mib cut ribbon cores Drk made of a soft magnetic material in a circular or preferably rectangular shape, which according to Figure 4 above the phase connection line 1 ' _R are stacked together. Such a choke can be produced, for example, with a small number of cut ribbon cores made of textured silicon sheet, each core having the dimensions 25 cm iron path length, 4 cm core height and 6.8 cm ² core cross section and each by means of

Tension locks are tightened. Four or twelve cutting tape cores are required for this, depending on the size (0, M mm or 0.1 mm) of the air gaps between their separating surfaces. A choke Dr with the same effect and suitability for the desired formation of the voltage pulse can also be produced, for example, with a number of cutting tape cores made of a cobalt-iron alloy with approximately 50% cobalt, which have the appropriate dimensions. Furthermore, toroidal cores made of a ferrite material come into consideration. Of such

Toroidal cores, which have an average iron path length of 25 cm, 1.5 cm core height and 2.5 cm ² core cross-section, for example, the number 40 is required to produce a choke with the specified suitability, but such toroidal cores do not have to be provided with air gaps, because they already have a reduced iron path length of a few 0.01 mm, and thus sufficient shear in their hysteresis loop. The inductance 1 _{s of} the inductor and the total length, that is the sum of the core heights of the stacked inductor cores, also determine the current value at the time when the contactor contacts are separated from Sch, to which the short-circuit partial current i ₂ in the current branch in which the contactor is located Seh and the inductor Dr lie, has risen after the large short-circuit partial current i ₁ in the secondary current branch has been switched on with the semiconductor contactor, the time profile of the partial currents i ₁ and i ₂ This results in the particular course i _k (t) determined according to the relationship (2). The second summand in relation (2) is already negligibly small at t = 0.5 msec and can be omitted therein, so that relation (2), like relation (1), only has an exponential expression with the same exponent contains, namely exp -0.654 t once. Thus, and especially with the above values for R _M , L _M and l _s = 0.05 mH in the relationship (2), the relationship for the time profile of the current ip in the inductor Dr is

Herein: r _B path resistance of a network thyristor Th in mΩ in m Ω r ₁ ohmic resistance of the branch circuit in which the semiconductor contactor is located, "r ₂ ohmic resistance of the current branch in which Seh and Dr lie, in volt U _s lock voltage one Netzthyristor Th, "Ε _ph RMS value of the generator voltage

Line phase ph, t Duration of the short-circuit current in msec.

The path resistance (equivalent resistance) of network thyristors is in the range 0.16 ... 0.2 mΩ, the lock voltage is 1.1 volts. The resistances r ₁ and r _{2 of} the two current branches, which can be, for example, ribbon-shaped current conductors, are now dimensioned so large that r _B + r ₁ = 0.3 mΩ and r ₂ = 0.6 mΩ. In order to; follows from relationship (3) that the partial flow i ₂ in Dr and the closed. Switch contacts K, K at t = 10 msec has risen from the initial value i _ph (0) = 100 A to 430 A. In this example, this is the largest value of the partial current i ₂ , which is only achieved if the point in time of the short circuit is very early in a

Half oscillation of the phase current i _ph is. Only in this case and when the switching time of the electromechanical contactor Seh is only 10 msec, its switching contacts are separated from each other with the greatest current load. In comparison, the data above does not result in the data shown here

Relationship for i ₁ (t) that the controlled partial current i ₁ reaches its maximum value of 2660 A at t = 5 msec and is still 2470 A at t = 10 msec. In general, it follows from the relationship (3) that the increase in the partial current i ₂ above the initial value i _ph (0) At the time of the short circuit, the inductor Dr is reduced, provided that the sum of the resistances r _B + r ₁ + r _{2 is} less than 0.1 mΩ. With, for example, 1 = 0.1 mH and with the otherwise unchanged data of the short-circuit circuit above, the partial current i ₂ at t = 10 msec rose by 175 A above the initial value i _ph (O). Another way to

Reduction of the partial current increase is seen in the use of thyristors Th with a lock voltage less than 1 volt (V). Thyristors are available for this

Compound semiconductor base. With, for example, 1 = 0.1 mH and U _s = 0.6 V and with otherwise unchanged data above, the partial current ip has increased by 127 A above the initial value at 10 msec. By reducing the current increase it is achieved that the switch contacts K, K can be separated from one another with a lower partial current i ₂ , that is to say with low current. In addition, it is more likely to prevent switching arcs from being able to form stably, or only switching sparks can occur during the contact separation, which are not harmful to the switching contacts.

In the described embodiments, a protective device according to the invention can be used without changes in principle from other than the public AC networks, for example from industrial industrial networks, from on-board networks and the like autonomous networks. For the power supply from direct current networks, the thyristors that are to be deleted or the power thyristors that can be switched off in the future, to which appropriate control means are assigned, are to be used as network thyristors.

Claims

 Claims

1) Protection device for the power supply of dwellings and similar buildings, in particular for residential systems (A), overcurrent protection device (Ü) to protect the electricity (1 _R , 1 ₆ , 1 _τ ) in the area of the house entry (E) , which are connected to the distribution network (N) by house connection line current conductors T ') branching from its phase conductors, indicates that an overcurrent protection in each current conductor (1' _R , 1 ' _s , 1' _T ) of a house connection ') shortly after its junction ( N _A ) is seen from the distribution board, which contains circuit breaker (L), n circuit breaker actuating circuit breaker, overcurrent detector (D), from which the control unit

Shutdown of the current by means of the line protection controlling signal is supplied if in an iter (1 ' _R , 1' _s , 1 ' _T ) the housing connection line has a protrusion, and monitoring device (O), from. 'which of the control unit

Reactivation of the current by means of the line switch controlling signal is supplied when the overcurrent has been eliminated.

device according to Claim 1, characterized in that the overcurrent protection devices (Ü ') current conductors (1' _R , 1 ' _s , 1' _T ) of a house connection line in a common protective housing-J; (G) are housed, which is designed to be shock and impact resistant and hermetically sealed and for every scrom conductor. (1 _R , 1 _s , 1 ' _T ) as well as an input and an output terminal (Kl _E or Kl _A ) for the neutral conductor (MP) of the house connection line. 3) Protection device according to claim 1, characterized in that the overcurrent detector (D) contains a flip-flop (k) with an upstream threshold level (st), which is connected to the output of a rectifier bridge (Gr) according to Graetz, the input of which is connected by sense lines (f) is connected to a current sensor (W _st ), and that the threshold value stage has a threshold value, which is dimensioned as a function of the sensitivity of the current sensor and a minimum value of the current rise to be determined, at which the shutdown of the current is to be controlled.

4) Protection device according to claim 3, characterized in that a choke (Dr), which is directly connected in series with the circuit breaker (L) (series choke), serves as a current sensor (W _st ). 5) Protection device according to claim 1, ά &dliϊ'όh characterized • that the monitoring device (0) with a voltage divider consisting of two primary windings (w1, w2) of two voltage converters (W1, W2) is connected in series, which is connected to the between the mains phase conductor (R, S , T), from which the conductor to be protected (1 _R ', 1 _s ', 1 _T ') branches off the house connection line, and the neutral conductor (MP) existing voltage is connected and the connection of the two primary windings (w1, w2) the output terminal (Kl _A ) of the conductor to be protected is connected, and that a signal controlling the reclosing of the current from a secondary winding (w _s ) of the voltage converter (W2) has its primary winding (w2) with one of its winding ends on the neutral conductor (MP) is connected, the control unit (St) for the circuit breaker (L) is fed via signal converters (Gr, U).

6) Protection device according to claim 1, 2 and 5 and one of the

Claims 3 or 4, characterized in that the circuit breaker (L) is an electromechanical contactor (Seh), and that the associated control unit (St) has two relay circuits for the electromagnetic actuation of the contactor contacts (K) has, of which a relay circuit for separating the same when the current is switched off with a semiconductor switching element (T1) controlled by the signal of the overcurrent detector (D) and / or by the disappearance of the signal of the monitoring device (0) in the event of a short circuit in the house connection line, and a relay current circuit to close the contactor contacts (K) when the current is switched on again with a semiconductor switching element (T2) controlled by the recurring signal of the monitoring element (C) after eliminating the cause of the overcurrent or short circuit, both relay circuits each have an excitation coil (e1, e2) for containing an actuating magnet and to one of the

Distribution network (N) powered DC power supply (Gl) connected. 7) Protection device according to claim 6, characterized in that at least the Seiaisstromkreis for electromechanical separation of the contactor contacts (K) when switching on the excitation current is connected to a DC voltage stored in a capacitor (C), which is greater than the voltage of the DC power source (G1) .

5) Protection device according to claims 1, 2 and 5 and one of claims 3 or 4, characterized in that the circuit breaker (L) is a semiconductor contactor with two oppositely parallel network thyristors (Th1, Th2), and that the associated control unit ( St) has a control pulse generator and a control output common to both line thyristors, which is short-circuited by a semiconductor switch (T _k ) connected in parallel when this is controlled in a current-conducting manner by a signal from the overcurrent detector (D) to switch off the current by self-extinguishing the line thyristors, which up to to emit a signal from the monitoring device (0) for switching on the current by opening the thyristors (Th1, Th2). 9) Protection device according to claims 1, 2, 4 to 7, characterized - that the circuit breaker (L) consists in that the series circuit of an electromechanical contactor and a series choke (Dr) Semiconductor contactor with two opposing parallel thyriators (Th1, Th2) is that the electromechanical contactor (Sch) has an associated control unit (St) and the Nalbleitar contactor has a control unit (St) with signal amplifier, but both contactors have an overcurrent detector (D) and have a monitoring element (O) in common, and the control unit of the semiconductor contactor that the signal of the overcurrent detector and / or a signal formed when the signal of the monitoring element disappears is fed in order to switch the network thyristors on, so that the current flows to the semiconductor contactor is commutated, and this signal or these signals are simultaneously fed to the control unit of the electromechanical contactor (Sch) and are supplied to both control units for longer than the switch-off time of the electromechanical contactor. that, on the other hand, the signal from the monitoring element (O) for switching the consumer current back on is at least fed to the calf conductor switching element (T2) of the relay circuit for the reclosure of the contactor contacts (K, K).