DE19944409A1 - Method and device for error-type-dependent sensitive triggering of residual current protection installs this device with a triggering differential current between a mains power supply and a consumer installation. - Google Patents

Abstract

A mains power supply (G) earthed through an operational earthing resistor (RB) is designed as a single-phase and TT mains with an installation earthing resistor (RA). A residual current protection device (RCD) with a triggering differential current (I DELTA n1) is installed between the mains power supply and a consumer installation (A) to implement differential current protection for the installation.

Description

The invention relates to a method for triggering a dif residual current protection device - hereinafter referred to as RCD Current Protective Device) - after the generic term of Claim 1 and a residual current device according to the preamble of claim 4.

RCDs are designed to protect people, animals and things from the dangers of electric current from practice z. B. as RCCBs widely known. You are at all "active" Head, d. H. to everyone operationally from the power grid to consumption and live conductors connected and disconnected the consumer system from the network if an insufficient Isolation between the network and earth is given, or they give a signal to report such an error.

In residual current protection technology, a distinction is made between two protection goals for protection by switching off, whereby differently sensitive RCDs are used:

• 1. Protection in the event of direct contact: If the live conductor is touched directly, a current referred to below as the "touch fault current" flows back through the person or animal body to be protected back over the earth to the voltage source. This touch fault current is known as the residual current from the In this case, the RCD must be designed to be very sensitive, so that the shutdown takes place at the lowest body current that is dangerous for humans or animals Protection against direct contact Residual current protective devices with tripping or rated differential currents I _{Δ n} ≦ 30 mA are required.These RCDs must also switch off in a very short time so that no body current remains at a level and duration that is dangerous for humans or animals can.
• 2. Protection against indirect contact: With indirect contact For the most part, a fault current flows through the protective cable ter and the earth back to the voltage source, this one Partial current in the following referred to as "protective conductor fault current" is not. Only a small part of the stream flows over the Body of the living being to be protected. RCDs for protection with such indirect contact and for fire protection can therefore be realized if a sufficiently low Plant earth resistance much less sensitive be designed, d. H. the difference recorded by the RCD current that leads to the switch-off can be at least around the Factor 10 higher than for RCDs that are used to protect di right touch. With such indirect People or animals are usually touched se only the maximum permissible touch voltage of 25 or 50 volts continuously exposed.

The disadvantage of the second-mentioned RCDs is that they are un have adequate protection from direct contact as they react too insensitive to such errors. The use of highly sensitive RCDs that protect against direct contact would, however, often prohibits systems in which be drive leakage currents occur as protective conductor fault currents ten despite the insulation measures in devices and systems de flow, possibly continuously or in particular re switching operations in the network, so accordingly strong differential currents are detected by the RCD. When on  set of highly sensitive RCDs would these differential currents unwanted shutdowns. From operational green Therefore, often insensitive RCDs have to be used find that have the disadvantage that they are only inaccurate provide adequate personal protection in the event of direct contact.

The invention has for its object a generic Improve RCD in that these are different Sensitivities can occur depending on the occurrence the nature of the error.

This object on which the invention is based is achieved by a Method with the steps of claim 1 and by a RCD with the features of claim 4 solved.

In other words, the invention proposes protection conductor fault current designated current that over the Schutzlei ter also flows through the RCD in such a way that he the difference between what flows to the consumer Current and the current flowing back from the consumer wrestles and so the residual current detectable in the RCD to Part picks up, the negative feedback portion of the Schutzlei ter fault current is <1. Special applications can also be used be seen that the residual current detectable in the RCD is temporarily canceled entirely, with a negative feedback "Part" of the protective conductor fault current = 1.

In this way, for all protective conductor fault currents such. B. Leakage currents, the differential current that can be recorded in the RCD is reduced device and achieves an insensitive characteristic of the RCD. However, currents that occur, for example, as a result of direct contact voltage-carrying conductor as touch fault currents the body of a living being flows down to earth, does not flow over the protective conductor, are therefore not negative feedback and are therefore fully recognized by the RCD as Diffe limit current is detected, so that the RCD with such a touch  Residual current with its highest, design-related sensitivity responds and causes a quick shutdown.

Advantageous embodiments of the invention are the Unteran sayings removable.

The invention will now be described with reference to the drawings explained. It shows

Fig. 1 is a purely schematic schematic diagram of an RCD with different sensitivity depending on the type of error, and

Fig. 2 shows the circuit diagram of an embodiment of an RCD designed as a RCCB.

Fig. 1 serves to explain the general principle of the inven tion. In Fig. 1 is purely schematically a supply network G grounded via the operational earthing resistor R _B , which is designed as a single-phase network and as a TT network with the system earthing resistor R _A , the switching device, however, on any multiphase networks and network forms transferable and applicable to all types of RCDs.

An RCD with the tripping or rated residual current I _{Δ n1} is installed between the network G and a consumer system A in order to implement the residual current protection for this system.

In the consumer system A there is a consumer V in an earthed, conductive housing. In addition to the load current I _L in the main circuit (L1, N), the consumer V allows the discharge current I _{Δ PE} to flow off via the protective conductor shown in broken lines, so that this leakage current is referred to as the protective conductor fault current. The load current I _L and a differential current I _Δ flow through the RCD to the consumer, while only the load current I _L flows back through the RCD from the consumer. The differential current I _Δ corresponds to the previously erläuter O configuration Feh initially adopted the system and lerart the protective ground fault current I _{Δ PE.} If the differential _current I _Δ reaches or _exceeds the value I _{Δ n1} , the RCD trips.

Furthermore, however, a coupling element K is provided, which is referred to as a coupling quadrant due to its four connections and to which the protective conductor fault current I _{Δ PE is} supplied. Via this coupling element K, a compensation current I _{comp is} coupled into the RCD in such a way that it is also detected as the current flowing back from the consumer and thus counteracts the differential current I _Δ = I _{Δ PE} actually to be detected by the RCD. This compensation current corresponds to the protective conductor fault current I _{Δ PE} attenuated on the coupling factor k <1. As a result of the negative feedback, the RCD now only detects the (1-k) -fold part of the protective conductor fault current I _{Δ PE} as actually detectable differential current I _Δ , so that the protective conductor fault current is higher by a factor of 1 / (1-k) must be reached to trigger the RCD.

The increased response threshold of the RCD, designated as I _{Δ n2} , results from the low response threshold, referred to as I _{Δ n1} , of I _{Δ n2} = I _{Δ n1} / (1-k).

The negative feedback means that the RCD only becomes less sensitive when the differential current I _{Δ is} caused by a protective conductor fault current. This is the case if operational leakage currents arise in the consumer V, or if a protective conductor residual current arises due to a fault-related insulation fault in the consumer V, ie if protection must be provided with indirect contact.

When touched directly, no leakage current flows through the protective conductor, but such a current flows, as also shown in FIG. 1, as a touch fault current I _{Δ B} through the human or animal body and via the location resistance R _St , without into the coupling element K to arrive, so that there is accordingly no negative feedback. The Berühr-fault current I _{Δ B} is detected in vol lem scope of the RCD as a residual current I _Δ, and the RCD thus further comprises at direct contact their high responsiveness, which enables an optimal protection of living organisms.

The circuit shown in Fig. 1 thus creates a residual current circuit breaker that responds with different sensitivity depending on the location of the fault and thus on the type of fault, namely depending on a direct or indirect contact.

If the coupling element K ensures a galvanic separation between the input and the output, the output of the coupling element K can be connected in parallel to any current path through the RCD in order to couple the compensation current I _comp . It is then also possible to accommodate the coupling element K in its own housing in order to use the invention even with existing RCDs. If there is no electrical isolation, but in the RCD the residual current detection is carried out using a total current transformer, a further winding can be arranged on the core of the total current transformer, which is fed from the output of the coupling element K, so that the RCD is simple and Can be designed inexpensively according to the invention.

For the design of the coupling element K applies that this egg represents a current transformer with a coupling factor k ent speaking transmission ratio between the output current and the input current. In the simplest case, this is a generally known, work on the transformer principle the current transformer, whose output impedance is high against over the impedance of the current path it feeds RCD.  

However, the coupling element K can also be in the form of a current transformer of an electronic circuit can be realized, whereby further advantageous design options of the invention surrender. So the coupling element K z. B. as an AC converter be trained to be insensitive to AC / DC sensitive RCDs against leakage current in the form of smooth direct current to ma Chen, or with AC-sensitive RCDs with sums current transformer through a premagnetization of the transformer core to avoid smooth DC differential current.

Furthermore, it is possible to design the coupling element K with a transmission behavior that changes over time, so that it initially has the coupling factor k = 1 in the event of an erratic protective conductor fault current I _{Δ PE} , but then assumes a coupling factor k <1 after a defined time. This gives you an RCD that delays and reacts with low sensitivity to a differential current that flows through the protective conductor, but which, when touched directly, offers the high protection level of a highly sensitive, undelayed RCD.

Similar delayed RCDs are in the residual current protection technology z. B. in use as a "selective" RCCB to a selective shutdown of only the faulty system part to be achieved when systems consist of several parts that are connected in series, such as. B. with a main distribution downstream sub-distributions. A disadvantage of this selekti However, RCCBs are that they are relatively un are sensitive and always react with a delay, therefore none provide comprehensive protection when touched directly.

An embodiment of the invention, which in principle can be applied to all types of RCDs in accordance with FIG. 1, is explained in more detail below with reference to FIG. 2 for a widely used RCD, the RCCB.

Fig. 2 corresponds essentially to the design of the RCD of Fig. 1. The consumer V or the system A causes gurgles in addition to a load current I _L an operational leakage current as a protective conductor fault current I _{Δ PE} , which, for example, by electrical heating devices, electronic and inductive ballasts for gas discharge lamps or surge arresters can be caused stationary or briefly caused by switching operations.

As RCD, a residual current circuit breaker F is shown with components 1 to 6 : In detail, this is a sum current wall learning 1 with primary windings 2 and. 3, a secondary winding 4 , an electromagnetic comparator (the trigger relay) 5 and a mechanical energy storage unit 5 for actuating switch contacts 6 .

In order to give this highly sensitive residual current circuit breaker the desired reduced response sensitivity for protective conductor fault currents, part of the protective conductor fault current I _{Δ PE} is passed through the residual current protective switch with the aid of a coupling element K so that it has the effect of the initially occurring Differential _current I _Δ partially cancels. The coupling element K is a common current transformer, with a turns ratio of z. B. k = 9/10 between input and output side. If the RCCB F has a response or rated differential current I _{Δ n1} = 30 mA for a touch fault current, then its response differential current is I _{Δ n2} = 300 mA for a protective conductor fault current.

Claims (8)

1. A method for triggering a residual current device known as an RCD,
where a fault current referred to as a protective conductor fault current is derived via a protective conductor and returned to the voltage source,
and this protective conductor fault current as the difference between the currents flowing to the consumer and flowing back from the consumer, in terms of size, and this detected current is referred to as the differential current,
and wherein the RCD triggers a switching operation as soon as the differential current reaches a predetermined value, characterized in that a portion ≦ 1 of the protective conductor fault current referred to as the compensation current is coupled into the RCD in such a way that the differential current which can be detected by the RCD is less than the protective earth fault current. 2. The method according to claim 1, characterized in that the compensation current on any main current path of the residual current protective device is coupled becomes. 3. The method according to claim 1 or 2, characterized net that the protective conductor fault current is initially complete is coupled into the RCD, and that with a temporal Delay in the coupled portion of the protective conductor Fault current is reduced. 4. residual current protection device,
with one connection each to all active conductors of a power network and a consumer system,
and with a connection to a protective conductor, via which a protective conductor fault current can flow from the consumer system, characterized by a circuit having a coupling element K for coupling a portion ≦ 1 of the protective conductor fault current referred to as compensation current into the RCD. 5. Residual current protection device according to claim 4, ge characterized by an additional, the compensation current coupling winding on the core of a sum current transformer of the protective device. 6. Residual current protection device according to claim 4, characterized characterized in that the compensation current source too a winding on the core of a summation current transformer the residual current device is connected in parallel. 7. Residual current protection device according to one of the claims che 4 to 6, characterized in that the circuit the compensation current on any main current  Coupled path of the residual current protective device. 8. Residual current protection device according to one of the claims che 4 to 7, characterized in that the coupling link in one compared to the other residual current protection direction is arranged separate housing.