Cahier technique no. 114 - studiecd.dk

1 Cahier technique no. 114 Residual current devices in LVJ. SchonekCollection TechniqueBuilding a New Electric World Cahiers Techniques is a collection of documents intended for engineersand technicians, people in the industry who are looking for more in-depthinformation in order to complement that given in product , these Cahiers Techniques are often considered as helpful tools for training provide knowledge on new technical and technological developmentsin the electrotechnical field and electronics. They also provide betterunderstanding of various phenomena observed in electrical installations,systems and equipments. Each Cahier technique provides an in-depth studyof a precise subject in the fields of electrical networks, protection devices,monitoring and control and industrial automation constantly updated collection can be downloaded from: contact your Schneider Electric representative if you want either a" Cahier technique " or the list of available "Cahiers Techniques" collection is part of the Schneider Electric s "Col-lection technique ".

2 ForewordThe author disclaims all responsibility subsequent to incorrect use of infor-mation or diagrams reproduced in this document, and cannot be heldresponsible for any errors or oversights, or for the consequences of usinginformation and diagrams contained in this of all or part of a " Cahier technique " is authorised with thecompulsory mention:"Extracted from Schneider Electric " Cahier technique " no.." (please specify).no. 114 Residual current devices in LVECT 114 first issue, february 2006 Jacques SchonekA graduate of the ENSEEIHT engineering school with a doctorate inengineering from the University of Toulouse, J. Schonek was involvedin the design of Telemecanique variable-speed drives from 1980 then went on to manage the harmonic-filtering is currently working as an expert in Electrical DistributionApplications in the Architectures and Systems group of technique Schneider Electric no.

3 114 / mode disturbanceAny continuous or transient electromagneticphenomenon occurring between a live part of apower system and earth. May be a transientovervoltage, a continuous voltage, anovercurrent or an electrostatic mode disturbanceAny phenomenon between different live parts ofa power system, an contactContact of a person with the live parts ofelectrical devices (normally energised parts andconductors).Earth-leakage currentCurrent that flows from the live parts to earth, inthe absence of an insulation of voltage between two parts of thebody of a living resulting in conductive part (ECP)Conductive part likely to be touched and which,although normally insulated from live parts, maybe energised up to a dangerous voltage leveldue to an insulation current IdCurrent resulting from an insulation contactContact of a person with accidentally energisedexposed conductive parts (ECP), usually due toan insulation preventing transmission of voltage(and current flow) between a normally energisedpart and an exposed conductive part (ECP)

4 FaultBreak in insulation causing an earth-fault currentor a short-circuit via the protective leakage currentCurrent that flows to earth via the intentionallyinstalled components (resistors or capacitors), inthe absence of an insulation conductorsSet of conductors for electrical powertransmission, including the neutral, with theexception of the PEN conductor for which the protective conductor (PE) function takes priorityover the neutral leakage currentCurrent that flows to earth via the insulation, inthe absence of an insulation systemSee "System earthing arrangement".Protective conductors (PE or PEN)Conductors which, according to specifications,connect the exposed conductive parts (ECP) ofelectrical equipment and certain other conductiveparts to the earth residual operating current I nValue of the residual operating current assignedby the device manufacturer at which the devicemust operate under the specified to construction standards, at 20 C,low voltage residual current devices mustoperate at residual currents between I n/2 andI nResidual currentAlgebraic sum of the instantaneous values of thecurrents flowing through all live conductors in acircuit at a point of the electrical current device (RCD)

5 Device whose decisive quantity is the residualcurrent. It is normally associated with orincorporated in a breaking operating currentValue of the residual current causing a residualcurrent device to earthing arrangement (SEA)Also referred to as the neutral system, earthingsystem or earthing IEC 60364 stipulates three main typesof earthing arrangements that define the possibleconnections of the source neutral to earth and ofthe exposed conductive parts (ECP) to earth orthe neutral. The electrical protection devices arethen defined for each voltage limit (UL)Voltage UL below which there is no risk fibrillationA malfunctioning of the heart corresponding toloss of synchronism of the activity of its walls(diastole and systole).

6 The flow of AC currentthrough the body may be responsible for this dueto the periodic excitation that it generates. Theultimate consequence is stoppage of blood technique Schneider Electric no. 114 / current devices in LVContents1 Introductionp. 42 The risks of electrical Electrisation of personsp. Fire hazardsp. Damage to equipmentp. 73 Protection against the Installation rulesp. 8of electrical Detection of insulation faultsp. 94 RCD operating principle and Operating principlep. Applicationsp. Main characteristicsp. Technologyp. Constraints due to the current sensorp. Special applicationsp. 175 Conclusionp. 22 Appendix 1: Calculation of touch voltagesp.

7 23 Appendix 2: Types of converters and fault-current waveformsp. 25 Appendix 3: Leakage currents for different system earthing arrangementsp. 28 Appendix 4: RCD thresholds and power system voltagesp. 30 Bibliographyp. 31 Today, residual current devices (RCD) are recognised as the most effectivemeans of protecting life and property against electrical hazards in low-voltage selection and optimum use require sound knowledge of the principlesand rules governing electrical installations and in particular system earthingarrangements as well as existing technologies and their these aspects are dealt with in this " Cahier technique ", with in additionnumerous answers provided by Schneider Electric technical andmaintenance departments to frequently asked technique Schneider Electric no.

8 114 / IntroductionCompared to other energy sources, electricityhas many advantages, but also many risks. It isused on a daily basis by the general public andmany accidents still occur, resulting in burns,fires and installation rules have been set up byinternational (IEC, CENELEC) and national( NFPA in the USA and UTE in France,) protective devices have beendesigned by carefully analysing the risks andconsequences of equipment failures or incorrectuse. Among these devices, RCDs (residual2 The risks of electrical Electrisation of personsA person subjected to an electrical voltage iselectrised. Depending on the level ofelectrisation, the person may be subjected todifferent pathophysiological effects:c disagreeable sensation,c involuntary muscular contraction,c burns,c cardiac arrest (electrocution).)

9 These effects depend on various factors,including the physiological characteristics of theperson, the environment ( wet or dryconditions) and the characteristics of the currentflowing through the person may be subjected to an electricalshock in two manners:c direct contact, the person touches anenergised, bare conductor,c indirect contact, the person touches ametal part of an electrical machine or device withan insulation dangerous aspect is the current (magnitudeand duration) flowing through the human bodyand particularly near the 1 : Direct and indirect ) Direct contactb) Indirect contactcurrent devices) are recognised by internationalstandardisation organisations as an effectivemeans to protect life and document will present the subject in threesteps:c a description of the risks related to electricalcurrents,c an overview of the protection techniquesemployed to limit those risks,c an in-depth presentation of how technique Schneider Electric no.

10 114 / 2 sums up the work of the InternationalElectrotechnical Commission on the subject(standard IEC 60479-1, , 2005, Effects ofcurrent on human beings and livestock - Part aspects). It indicates the consequencesof AC current flowing through the human body,from the left hand to the feet, depending on thecurrent and its is especially important to consider zones AC-3and AC-4 where there is real Zone AC-3 (between curves B and C1)Usually no organic damage, but there is alikelihood of muscular contractions and difficultyin breathing, with reversible disturbances in theformation and conduction of impulses in Zone AC-4 (located to the right of curve C1)In addition to the effects noted for zone AC-3,the probability of ventricular fibrillation.