EP0220215A1

EP0220215A1 - Fault-current protection switch for a.c. and d.c. fault currents without energy storage

Info

Publication number: EP0220215A1
Application number: EP19860902330
Authority: EP
Inventors: Gottfried Biegelmeier
Original assignee: Brown Boveri und Cie AG Germany; BBC Brown Boveri AG Germany
Current assignee: BBC Brown Boveri AG Germany
Priority date: 1985-05-02
Filing date: 1986-04-12
Publication date: 1987-05-06
Also published as: GB8610625D0; AU5774586A; GB2177560A; WO1986006563A1; GR860990B; ES8707384A1; ES554413A0

Abstract

Un disjoncteur de protection contre des courants de défaut, comprenant un transformateur de courant totalisateur (10), à l'enroulement secondaire (11) duquel est reliée la bobine d'excitation (26) à la fois directement et par l'intermédiaire d'un circuit électronique (13), de sorte que les courants de défaut alternatifs et continus aussi bien que les courants de défaut alternatifs ayant des composantes de courant continu peuvent être détectés et utilisés pour déconnecter un circuit de courant secteur.A circuit breaker for protection against fault currents, comprising a totalizing current transformer (10), to the secondary winding (11) of which the excitation coil (26) is connected both directly and by means of an electronic circuit (13), so that alternating and direct fault currents as well as alternating fault currents having direct current components can be detected and used to disconnect a mains current circuit.

Description

Residual current circuit breaker for fault alternating and residual direct currents without EnereiesDeicherune

The invention relates to a residual current circuit breaker according to the preamble of claim 1.

The impetus for the invention is given by the experience which has been gained in the use of the residual current circuit and which requires new technical solutions in order to close the gaps which have become known in the scope of this protective measure which is used in many countries today.

The three basic circuits that were possible for the construction of residual current circuit breakers (shortly called circuit breakers) were specified twenty years ago (1). As circuits which are independent of the mains voltage as an auxiliary voltage source, either the secondary winding of the summation current transformer is connected directly to the residual current release, or the energy storage circuit - a trend-setting Austrian invention (AT-PS 197.468) - is used. V ^*

A modern concept of a residual current circuit breaker must also master the triggering of residual currents which can occur in the form of pulsating or smoothed direct currents. It has always been known that FI circuit breakers can only be effective in the case of alternating fault currents. If the fault current has direct current components, the tripping sensitivity of the circuit breakers is adversely affected. As more and more electronic components are used in household appliances, the DC problem must also be solved. It has long been believed that in the circuits used in practice in electrical household appliances, in the event of a ground fault, the flowing fault current can still occur in the form of a pulsating direct current. For fault currents such as those e.g. In the case of one-way rectification without a smoothing capacitor, it is possible to build residual current circuit breakers independently of the mains voltage using the classic circuits, that is to say also with the energy storage release (GB-PS 2 082 408 B). However, it was found that it is hardly possible to impose restrictions on the manufacturers of electronic devices because of the Fl circuit breaker in the selection of electronic circuits necessary for their devices. In particular, the one-way rectifiers with smoothing capacitors and the three-phase rectifiers must be mentioned in this context.

Circuits independent of the mains voltage cannot detect fault currents in the form of smoothed direct currents due to the principle of tripping. In this case, it is necessary to use electronic circuits that naturally depend on the mains voltage. gen and can process residual DC currents in all forms via summation current transformers. For example, US Pat. No. 3,768,011 and published patent application DE-OS 27 30 874 describe such circuits. The question thus arises which dangers can arise from the use of the network as an auxiliary voltage supply for triggering fault protection switches. If the auxiliary voltage is only taken from one outer conductor and the neutral conductor, the switch can fail if the corresponding outer conductor or the neutral conductor fails (for example when a fuse of the outer conductor responds or if the neutral conductor breaks) and fault voltages caused by ground faults of the two other outer conductors can no longer be recognized. But even if all three outer conductors of a three-phase network are used for the auxiliary voltage supply, the neutral conductor break still remains. An attempt was therefore made to remedy this by triggering the Fl switch when the neutral conductor breaks (DE-OS 28 25 881). If an additional connection, for example the protective conductor, is used for this, then this has the disadvantage that the installation is complicated and the earth potential is brought into the switch. However, this makes the circuit more sensitive to overvoltages, which occur above all to earth. Mains-dependent tripping has the disadvantage, however, that in the event of a ground fault in the protected system, the level of the voltage for the auxiliary voltage supply depends on the ratio of the network loop resistance between the transformer and the connection points of the auxiliary voltage supply to the overall resistance of the fault loop. This is shown in FIG. 1 for the case of a short to ground in a zeroed system.

^' Is referred to as:

ZL line impedance of the outer conductor from the transformer to the residual current circuit breaker

ZpEN line impedance of the PEN conductor from the transformer to the residual current circuit breaker

Z-j line impedance of the outer conductor after the fault current circuit breaker to the point of failure

∑2 Line impedance of the protective conductor from the fault location to the PEN conductor

1 Mains voltage - outer conductor PEN conductor

U _a supply voltage of the mains voltage-dependent electronic circuit

then the following applies to the level of the supply voltage:

U _a = Ü _N x Z1 + Zp

^Z L ^{+ Z} PEN + Z ₁ + Z ₂

If there is a short to ground near the installation position of the Fl switch, the auxiliary voltage can become zero, making tripping impossible. In these cases, the overcurrent protection devices have to disconnect the earth circuit, the Fi switch has become inoperative. For this reason, in countries that use switches with line-voltage-dependent tripping systems,

REPLACEMENT LEAF only the so-called additional protection is achieved due to Fl protection and corresponding restrictions are planned in international regulations (2, 3).

It is also of no use if - as stated in DE-OS 28 25 881 - the voltage of the neutral conductor is monitored against the protective conductor. The circuit fails if a short circuit occurs at the same time as the short to ground. As can be seen from FIG. 2, in this case the output terminals of the Fl switch are short-circuited together with the protective conductor, the switch cannot trip and the protected system parts nevertheless take an error voltage of e.g. 110 V on.

This can be seen in Figure 2 with the designations:

ZL 'line impedance of the outer conductor from the transformer to the residual current circuit breaker

ZN 'line impedance of the neutral conductor from the transformer to the residual current circuit breaker

ZL ¹ 'Line impedance of the outer conductor from the residual current circuit breaker to the short circuit point

ZJJ ¹ 'Line impedance of the neutral conductor from the residual current circuit breaker to the short circuit point

ÜJJ mains voltage outer conductor neutral conductor

ü _a supply voltage of the mains voltage-dependent electronic circuit

Ers l PE connection terminal for the protective part in the residual current circuit breaker

Ik short-circuit current

IA. Fault current

R _A Earth resistance of the protected system

Rg earth resistance of the neutral conductor in the transformer station (operating earth)

U _a = U _N x ZT. "+ Zw"

Z _L ^« + Z _L " + Z _N '+ Z _N "

If the short circuit occurs close to the residual current circuit breaker, the supply voltage breaks down and the PE terminal also assumes the potential of the short circuit point. The switch can therefore never trip. The short-circuit current 1 ^ flows through the outer conductor and neutral conductor and the voltage drop in the neutral conductor caused by it becomes effective as a fault voltage in the ratio of the system earth R ^ to the operational earth Rß. The fault current 1 ^ flowing as a result of the fault voltage cannot trigger the switch due to the absence of the auxiliary voltage U ^. In order to be able to use a residual current circuit breaker for protection against indirect contact (error protection), the following conditions must be met:

1) With normal mains voltage supply, the switch must be activated when fault changes and / or faults occur. trigger direct currents. Dissolves it at Fehlerwechsel- of the tripping fault current strδmen at the nominal value I _on, then it is sufficient for physiological reasons (4) when the triggering pulsating Fehlergleichströ¬ men examples in disposable sliding Ehrich Tung / ^"2 x I _{Δ n,} wherein Voll¬ weggleichrichtung at 2 x I _{Δ n} and 2.8 x I ^ n in the case of smoothed fault direct current. To achieve this, mains voltage-dependent electronic circuits are required. Other auxiliary voltage sources, for example batteries, are ruled out for this purpose for practical reasons.

2) The switch must also trip in the event of a failure of the outer conductor and / or the neutral conductor as well as in the event of short-circuit and earth faults in the event of fault AC currents. In these cases, it does not need to remain functional in the case of DC faults because, firstly, the simultaneous occurrence of a network fault and a DC fault current represents a negligible safety risk, and secondly, in the event of short circuits, the fault voltage as a result of the voltage division between the phase conductor and neutral conductor in networks up to 240 V against Earth remains below 120 V and therefore the conventional contact voltage limit, which is 120 V for direct current, is not exceeded.

As explained, circuits which are independent of the mains voltage cannot detect smoothed direct currents; constructions which are dependent on the mains voltage fail again when the outer conductor and / or the neutral conductor fail and in the event of short-circuits occurring at the same time with ground faults. The technical requirements regarding protection zes with indirect contact thus exclude both mains-independent circuits and mains-voltage-dependent circuits.

These apparently contradictory requirements for a residual current circuit breaker for protection against indirect contact (fault protection) naturally lead to new technical solutions. For example, the older EP-OS, which is based on the Austrian patent application A 11 37/85, describes a solution that also uses the residual current release, preferably in the form of a permanent magnet release, for the energy storage circuit, which is independent of the mains voltage, to be triggered by the Mains voltage-dependent electronic circuit used. Energy storage circuits have the advantage that they work with a short delay and are therefore surge current-resistant and selective. This is of great advantage for protection in the event of indirect contact. On the other hand, for protection against direct contact, it is important that the device is switched off as quickly as possible and the tripping current is below 30 mA. Tripping with pulsating or smooth DC fault currents is of little importance for additional protection, but it is conceivable that triggering with DC fault currents is required for special applications.

The object of the invention is to provide residual current circuit breakers of the type mentioned at the outset, which can be used without great effort both with AC residual currents and with DC residual currents or AC residual currents with DC residual current components. This object is achieved according to the invention by the characterizing features of claim 1.

Further advantageous embodiments of the invention can be found in claims 2 to 4.

The residual current release is actuated with alternating or direct current with the energy drawn from the network via the electronic circuit and the release coil. The secondary winding of the summation current transformer is connected directly to the residual current release and is used for triggering in the event of residual AC currents or pulsating residual DC currents.

One can also use a tertiary winding for controlling the electronic circuit according to the invention, with which smooth fault currents, or else fault currents with DC components, are detected. If the fault current release has two partial trip coils, then according to the invention the circuit for the direct triggering can be galvanically separated from the electronic circuit.

It is known that state of the art that a Fehlauslö- _S s of residual current circuit breakers due to Stoßströ¬ men with lightening can thereby be avoided that the secondary winding or Tertiär¬ winding of the summation current transformer voltage-dependent Wi¬ resistances for example anti-parallel diodes are tet geschal- parallel. Voltage peaks are thereby cut off and thus trigger pulses on the residual current release are avoided. According to the invention, the winding which is dependent on the oscillator current of the electronics Circuit is used to achieve the immunity of the residual current circuit breaker to surge currents. For this purpose, as described above, voltage-dependent resistors of this winding are connected in parallel. Not only is the shock resistance achieved, but also the overvoltage protection and the electronic circuit.

The invention and further advantageous refinements are to be explained and described in more detail with reference to the drawings, in which the prior art and two exemplary embodiments of the invention are shown.

It shows:

Fig. 1 u. 2 each two configurations that the state of the

Technology and which have already been explained in more detail above,

Fig. 3 shows a residual current circuit breaker according to the invention and

Fig. 4 shows a further embodiment of a fault current circuit breaker according to the invention.

As already mentioned, Figures 1 and 2 have already been described and explained above in the assessment of the prior art.

Reference is now made to FIG. 3. This figure shows a residual current circuit breaker with a summation current transformer 10 whose primary windings are connected through the the phase current conductor L ^< , L ₂ and L3 and the neutral conductor are formed. The secondary winding of the summation current transformer 10 is connected to a first tripping coil 12 of a fault current release, designated in its entirety by the reference number 25, and triggers the triggering when fault alternating currents or pulsating fault direct currents occur.

An electronic circuit 13, which contains an oscillator, is connected in parallel with the secondary winding 11. The electronic circuit 13 is supplied with mains voltage from the phase conductor L- | and the neutral conductor N. On the output side, the electronic circuit 13 is connected to a second tripping coil 16 of the residual current release 25. This electronics circuit 13 is used to detect fault DC currents or fault AC currents with DC components in such a way that the total current transformer 10 is premagnetized via the oscillator in the electronics circuit; in the event of a fault direct current or a fault alternating current with direct current components, the operating point of the total current transformer is shifted, which is detected by the electronic circuit 13 and leads to the output of a signal to the trigger coil 16, whereby the trigger 25 triggers a switching lock 17 which triggers Contacts 18 in the phase conductors Lj to L3 and the neutral conductor N opens. In other words: with fault direct currents or fault alternating currents with

DC components is generated in the summation current transformer 10 by the oscillator of the electronic circuit 13 in the secondary winding 11 of the summation current converter 10 Voltage so changed by asymmetry or displacement of the working point, that via the Elektronik¬ circuit 13 _'the verbun¬ parallel with the secondary winding 11 with the trip coil 16 of the residual current device 25 to, these obligations with the aid of the mains power (via the Lei¬ 14 and 15 ) excited via the electronic circuit 13 and thus triggers the residual current circuit breaker. Parallel to the input of the electronic circuit 13 and thus also parallel to the secondary winding 11, a diode circuit consisting of two antiparallel connected diodes 19 is provided as voltage-dependent resistors, which serve to achieve the surge current resistance and the overvoltage resistance.

The residual current circuit breaker according to FIG. 4 has only one summation current transformer 10, the secondary winding 11 of which is connected directly to the first trip coil 12. The fault current circuit breaker is thus triggered when fault alternating currents or pulsating fault direct currents occur. In addition to the secondary winding 11, a tertiary winding 20 is wound on the summation current transformer 10, which is connected to the diode circuit 19 in parallel and the outputs of which are connected to the electronic circuit 13. The output of the electronic circuit 13 is again connected to the trip coil 16 of the residual current release 25.

It can be seen from FIGS. 3 and 4 that the residual current release 25 has two release coils 12 and 16, as a result of which the two release circuits are electrically isolated from one another. The diode circuit 19 also serves to achieve the surge current resistance and the overvoltage strength and it is connected in parallel to the oscillator circuit in the output circuit of the tertiary winding 20. It can be seen that an actuating button 26 or switching knob 26 is arranged on the switching lock 17, with which the fault current circuit breaker can be switched on or off again.

Literature:

(1) Biegelmeier, G .: Modern residual current protection. E.u.M.,

75th vol. (1958), H.8, pp. 157-164

(2) Biegelmeier, G .: Thoughts about zeroing (TN system) as optimal error protection (protective measure with indirect contact) in electrical systems. ÖZE 37th vol. (1984), H.12, p. 483

(3) IEG 64 (Central Office): 151, January 1985, IEC

Publ. 364 Part 5, Chapter 53 switchgear and controlgear

(4) IEC Report 479, second edition: Effects of electric shock on the human body, Part 2, Chapter 5

\ T ~. ~ - f;! _ Λ ~ - * ^'

Claims

1. Residual current circuit breaker consisting of a contact apparatus arranged in a suitable housing with connecting terminals for the installation lines with associated switch lock, test device and actuator, a residual current release with one or two trip coils, a summation current transformer and a mains voltage-dependent electronic circuit, with the secondary winding of the Total current transformer is directly connected to the tripping coil of the residual current release, and as a result the residual current circuit breaker is triggered when fault alternating currents occur and possibly also with pulsating fault direct currents, on the other hand this resolution is also caused by the voltage-dependent electronic circuit when fault direct currents occur and possibly also in the event of faults - AC currents with direct current components is effected in that the direct current or the direct current component in the total current transformer voltage generated by an oscillator of the electronic circuit in a winding of the converter due to asymmetry or by shifting the operating point so that a switching process is effected via the electronic circuit by means of which a residual current release is actuated with the aid of the mains energy, characterized in that just one Total current transformer (10) and only one residual current release (25), preferably in the form of a permanent magnet release, both for triggering independent of the mains voltage by the direct connection of the trigger coil of the residual current trigger with the secondary winding (11) of the total current transformer (10) as can also be used for triggering with the electronic circuit (13) as a function of the mains voltage (FIG. 3).

2. Residual current circuit breaker according to claim 1, da¬ characterized in that the secondary winding (11) of the summation current transformer (10) is directly connected and a tertiary winding (20) via an electronic circuit (13) with the release coil of the residual current release (25).

3. Residual current circuit breaker according to claims 1 or 2, characterized in that the residual current trigger (26) has only one trigger coil, which with the secondary winding (11) of the summation current transformer (10) directly as well as with the tertiary winding (20) of the sum ¬ current transformer (10) is connected via the electronic circuit (13).

4. Residual current circuit breaker according to claim 2, da¬ characterized in that the trigger coil comprises two Teilaus¬ release coils (12, 16), each dimensioned for tripping, and that the secondary winding (11) with a Teilauslδsespule (12) and the tertiary winding (20) is connected to the other partial trip coil (16) via the electronic circuit (13).

5. Residual current circuit breaker according to one of Ansprü¬ che 1 to 4, characterized in that parallel to the secondary or tertiary windings of the total current transformer (10) through which the oscillator current flows, voltage-dependent resistors, for example diodes (19) connected in parallel, are connected.