Home Practical problems Measuring, testing and protective measures RCD test with five times the rated residual currentIf we want to measure a four-pole RCD as part of a periodic test according to DIN VDE 0105-100, the following quote is included in the appendix to the standard: "The tripping of the RCD should be proven once for each circuit (...) this should, if possible, with a test current that corresponds to five times the rated differential current of the respective RCD.« Why should five times the rated differential current be taken and what does "proved once for each circuit" mean?MF, ThuringiaResponsible for standardization and testing as well as deputy head of development at Doepke Schaltgeräte, Norden.Lorem ipsum dolor sit amet, consectetur adipiscing elit.Nullam pellentesque malesuada arcu dignissim pellentesque.Vestibulum vitae ex in massa aliquam lobortis ac sit amet elit.Phasellus blandit lectus ac dui pharetra, ac faucibus diam commodo.Buy practice problem individually and access it directly**If you buy individual items, you accept the data protection regulations and terms and conditions.If there are problems with the download or if links do not work, please contact kontakt@elektro.netLorem ipsum dolor sit amet, consectetur adipiscing elit.Nullam pellentesque malesuada arcu dignissim pellentesque.Vestibulum vitae ex in massa aliquam lobortis ac sit amet elit.Phasellus blandit lectus ac dui pharetra, ac faucibus diam commodo.Phasellus blandit lectus ac dui pharetra, ac faucibus diam commodo.Phasellus blandit lectus ac dui pharetra, ac faucibus diam commodo.Nulla pharetra ultricies velit in fermentum.Sed et laoreet mi, nec egestas lorem.Mauris vel eros convallis, sollicitudin erat a, pulvinar turpis.Vestibulum vel orci et ligula sollicitudin aliquam.Curabitur quis massa porta, gravida eros eget, imperdiet ex.Ut eu vulputate tellus, quis fermentum nulla.Aenean fermentum nisl sed augue venenatis, a vulputate nunc iaculis.Nam ut lorem fringilla, venenatis libero vel, dignissim mi.Etiam vel enim eget erat congue eleifend.Morbi efficitur dolor ac blandit fermentum.It's nice when the "small print" in standards is read and people think about it.You also have to look at the history here.Before 2009, there was no indication of this in the installation and operating standards.In VDE 0100 - 610 : 2004 - 04 one reads in 612.6.1 a ) 2 ) "The effectiveness of the automatic shutdown of the power supply by residual current protective devices (RCD) must be proven by generating a residual current up to the level of Idn using suitable test devices a measurement of the switch-off time is not necessary."but further in note 6 on measurement of RCD type [S]... "This can be demonstrated by measuring the turn-off time."In VDE 0105 - 100 : 2009 : 10 in 5.3.101.02 in Note 2 you will find the sentence "The testing of the switch-off times for protection by automatic switch-off in the event of a fault in circuits with residual current devices (RCD) should be carried out in accordance with DIN VDE 0100-410 (VDE 0100- 410) with a test current of 5 x Idn."When testing RCDs, there is obviously the formal problem that RCD type [S] could collide with the switch-off times of VDE 0100 - 410.However, these types are generally available in the Idn 300 mA or 500 mA version.In the 2015 edition of the standard, this requirement was obviously weakened.A note in the text of the standard has now only become a national annex NC informative.So much for the importance of implementing this test step.The responsible K 224 tries to explain the problem in volume 13 of the VDE publication series 11th edition 2017 on page 103.I see it more as a bow to the manufacturers of RCDs instead of a safety-related explanation, which is hardly recognizable there, especially since there is an incorrect statement in the actually decisive sentence, p. 104 2nd paragraph penultimate sentence: "Because at 5 x idn switch these devices in less than 0.15 s."This is an incomplete and incorrect reference.The product standard for RCDs specifies a maximum switch-off time of 0.04 s for normal RCDs and 0.05 to 0.15 s for RCD type [S] at 5 x Idn.Furthermore, this standard requirement is in contradiction to VDE 0100 - 710, where the annual tripping of the RCD with rated differential current, i.e. 1 x idn, is rightly required.DGUV I 203-072 from 2017 https://publikationen.dguv.de/dguv/pdf/10002/203-072.pdf also refers to VDE 0105-100 but gives the practical tip: "In practice, only the Switch-off time checked with a current of 1 ⋅ IΔn. This results in standard values ​​between 20 and 50 ms. If the standard values ​​are exceeded, it must be checked again with 5 ⋅ IΔn. If the tripping time is then significantly higher than the standard value or close to the maximum permissible switch-off time according to Table 41.1 of VDE 0100-410 or the RCD does not trip, this usually indicates either a superimposed direct current or an unsuitable, defective or selectively acting RCD. The DGUV is thus doing justice to the protection goal with this practical tip."Obviously, there are also strong discussions among experts.The main protective aim of using RCDs is to protect people from electric shock.The fact that this also makes an excellent contribution to fire protection and that this has also been recognized in a note in VDE 0100 - 410 since 2009 should not be considered further here.Given the current state of development of the technology, which is openly discussed among experts https://www.diesteckdose.net/viewtopic.php?f=17&t=16350&p=197176&hilit=Biegelmeier&sid=b90d9d66e2c469a5b3d68e8c212e7dc0#p197176, one can assume that that in practice, when tripping with a rated differential current of 1 x Idn, 95% of all type A RCDs trip faster than 50 ms.General upward deviations are observed with RCD types B, B+, F etc.Furthermore, it is agreed that during the switch-off phase of an RCD with a fault current through a person of around 1000 ohms body resistance as a simplified calculation value with a peak value of the voltage of 328 V (rms value 230 V) with up to 328 mA at 50 ms is definitely reached 5 times .There are cases where, despite RCD, people died in the bathroom, for example in Magdeburg in 2012 with reanimation and in 2013 2 children in Kassel.The RCD does not limit the current, only the time.Despite many experiments on animals, there is a certain, accepted residual risk when using the parameters specified in the standards, for example the switch-off time of 0.2 s in the TT network and 0.4 s in the TN network.There is only one series of tests by Prof. Biegelmeier on an electric shock test, also available as a YOUTUBE video https://www.youtube.com/watch?v=08r27LnLHCM From this video there is the following key statement.Prof. Biegelmaier carries out approx. 500 tests and has survived them.This gives a survival probability of 99.8% under the given conditions.It is stated that the RCDs used always had a shorter switch-off time than 1.5 periods of a 50 Hz wave, ie 0.03 s, used voltages up to 200 V, measured currents up to more than 400 mA.The switch-off time therefore deviates significantly from the values ​​specified in VDE 0100 - 410, which also apply to normal circuit breakers and fuses.So if you want to check the safety of an RCD in terms of electric shock, you should rather orientate yourself on Biegelmeier's empirical values.The practical tip of the DGUVI comes pretty close.I myself also test in hospitals with 1 x Idn as required, but then use the usual values ​​of 50 ms determined from experience with more than 15,000 measurements on RCDs from several manufacturers, which has now also been adopted by the BG, and would recommend this procedure to anyone recommend to other examiners.Basically, with the aim of protecting against electric shock, this of course primarily makes sense in relation to RCDs with Idn 30 mA.In the case of RCDs with a different protection goal, e.g. fire protection, it must of course also be allowed to use the same criteria as a basis that are customary for fire tests, flaming times of several s. Then with 1 x Idn, 0.2 s or 0.4 s of the norm.The second question is easier to answer.A circuit in the sense of disconnection at the RCD is the sum of all circuits after the RCD.With a three-phase RCD, the test on one phase is sufficient, eg immediately after the RCD in the distribution, saves the movement to switch it on again.Then, depending on the type of installation of the individual phase outputs, via junction boxes or looping through from equipment to equipment, only the protection of the shutdown in the event of L / N errors at all or at the last BM in the circuit and the effectiveness of the presence of the protective conductor at all BMs must be proven.I recommend ALWAYS checking with 1x Idn.It will be noted that in practice >99% of all RCDs will trip within the required time.Furthermore, the test was "sharper" with 1x Idn than the standard requires.I would only switch to 5x Idn in special cases.I refer to this as troubleshooting rather than normal testing.When it comes to circuits, I agree with the previous speaker: Tripping time and current are checked once for each RCD.It doesn't matter which circuit or which socket.Even with the test prods directly on the RCD terminals, reliable verification of the function is possible.Only in exceptional cases do I test at several sockets.For example, if there is no documentation or labeling and it is not clear which circuits are on the RCD and which are not.Practical example: Distribution in the old stock, RCD only intended for the bathroom.Unfortunately, the cables for the bathroom and living room were swapped during construction ->therefore no personal protection in the most important area!The editorial team's response was published in paper form with DE 20/2019 in October.Something must therefore be said again, since the comment on question 1 is certainly not sufficient, as it is confusing.In the sections "Simple rated residual current" and "Fivefold rated residual current" it is stated "that "unfortunately there is no logical agreement in the standards." As members of the relevant standards committees, however, one should have a practicable opinion on what is correct and what is not and These are then represented. This is missing from the statement. The statement of the test with simple rated residual current is also in the international standard edition of VDE 0100 - 600, ie IEC 60364 Part 6 in the informative part under test method D.6.4.3.7.1 General "According to IEC 60364-4-41, where automatic disconnection of supply is provided by an RCD, the disconnecting times for RCDs relate to prospective residual fault currents significantly higher than the rated residual operating current (typically 5 IΔn).Testing at IΔn may be sufficient". It is shown here that the general prerequisites for automatic shutdown, see also the Bieglmaier film mentioned above, depend on the presence of a sufficiently grounded PE and thus a fault current greater than 5 x idn the point of error is assumed and mentions that the test with 1 x idn is sufficient. Therefore, in the context of the objection procedure, I had requested that either the original English text appear in the VDE 0105 - 100 or that this part not be included at all or due to different Possibilities, TT network or TN network then both variants must also be presented. Unfortunately, the responsible UK of the DKE did not follow this, so that the relevant purely German text in VDE 105 - 100 : 2015 - 10 was left as it is as early as 2009 in note 2 at the appropriate place, at that time still in the normative text, it said that the test "should be carried out" with 5 x idnIn the VDE 0105 - 100 / A1 : 2017 - 06 issue, the corresponding instruction has at least moved to the informative part with the confusing wording "should be made with 5 times that if possible".This shows how controversial this statement is among experts.Checking the author's note with 5 x idn is therefore not practical.In practice, it often happens that a large part of the RCD trips so quickly that the measuring devices can then no longer determine any measured values.Measured values ​​below 5 ms are usually no longer displayed.The required measured value is therefore missing.Therefore it is practically better and tried and tested to follow the instructions of DGUV 203-072.Then, based on the sequence of RCDs tested with 1 x idn and the tripping times determined over the years, it is also possible to identify any deterioration in safety and to make timely decisions on changing the RCD or estimating the next test date.The statement on testing the RCD with 5 times the rated differential current is still very undifferentiated, since there are also RCDs with 100 mA, 300 mA, 500 mA and 1000 mA.Everyone can probably calculate 5 times the values ​​themselves.What this has to do with protection against electric shock is very questionable.So there is no indication that RCD 30 mA could be meant and that this would be a possible application for TT networks.The release at switch-off times of the RCD type A(KV), F or B at 1 x idn with 0.2 s to 0.3 s cannot be confirmed either.Experience shows that these trigger somewhat higher at 1 x idn, but the values ​​are mostly around 0.1 s. The argument of the alleged higher availability of the system must be rejected.Here is really protective measure before function.In the case of an RCD that cannot do what the majority of other RCDs can do, I recommend replacing the RCD with a type from another manufacturer that has sufficiently short switch-off times, regardless of the manufacturer.I think in the case of electrocution, that can only be the only correct answer.Manufacturers with a different opinion should also consider this.Please complete all required fieldsYour questions to our industry expertsDo you have a technical problem in the field of electrical engineering standards and regulations?Then ask your technical question here free of charge.The answers are provided by experts in the electrical industry.You also have the option of commenting on questions.The latest from elektro.net straight to your inbox!