Special Insert. Everything you wanted to know about Type B residual current circuit breakers but never dared to ask

Transcription

1 Special Inser Everyhing you waned o know abou Type B residual curren circui breakers bu never dared o ask

2 Claudio Amadori: R&D ABB 1 Figure 1 - Marking of he Type B residual curren circui breakers Type AC or Type A RCDs, complian wih he Sandards IEC/ EN and IEC/ EN ), are suiable for mos ypes of household and similar applicaions. However, he increasing use of power elecronics echnologies in Consumer appliances wih earh connecion can resul in leakage currens having waveforms wih a high DC componen and/or high frequency, in boh faul and faul-free condiions. These currens, no inended for Type A or Type AC residual curren circui breakers, could affec heir proper operaion. I mus be said ha Type A RCDs, as a rule, are immune o he residual curren overlap of a direc curren up o 6 ma. In case of direc curren leakage over 6 ma, he proper operaion of Type A circui breakers is no guaraneed. Depending on he case, he Type A or Type AC residual curren circui breaker could herefore presen he following drawbacks: desensiizaion of he residual curren circui breaker which may no rip properly in he even of a ground faul of equipmen ha generaes currens wih a high DC componen or high frequency (failed ripping, delayed or excessive residual curren values); desensiizaion of he residual curren circui breaker which may no rip properly in he even of a faul on anoher circui powered from he same RCD (even if his faul curren has a sinusoidal alernaing shape); nuisance ripping wih no faul. To solve hese problems, Type B residual curren circui breakers were inroduced in he 1990s, whose Firs Ediion of he IEC produc sandard daes back o 2007 (and in more recen years, Type F RCDs were inroduced, wih inermediae characerisics beween Type A and Type B RCDs). Pending an acual produc sandard for Type B residual curren circui breakers, one referred o he IEC Technical Repor (General Requiremens for Residual Curren Operaed Proecive Devices), which conains he general characerisics of RCDs, including hose for Type B. Wih he issuance in 2013 of he Second Ediion of he Sandard IEC EN/62423 (Type F and B RCDs wih and wihou inegral overcurren proecion for household and similar insallaions), derived wih a few minor changes from he corresponding Second Ediion of he inernaional Sandard IEC 62423, he regulaory evoluion of Type B RCDs for household and similar use came o a conclusion. This Second Ediion conains some small changes in he requiremens for Type B circui breakers. In addiion, i inroduces he bipolar Type B RCDs and he Type F RCDs previously no conemplaed by he sandard. Type B RCDs ha comply wih he laes ediion of IEC/EN can be idenified by he marking of Figure 1, whose graphic represenaion recalls he various residual curren forms for which he Type B circui breaker is designed. The Sandard IEC/EN mus be used in conjuncion wih he Sandard IEC/EN or he Sandard IEC/EN as i conains only he requiremens and ess in addiion o hose laid down in he cied sandards for Type A RCDs. To hese sandards, only for indusrial applicaions, mus be added he Sandard IEC/EN ) The Sandard IEC/EN covers pure RCDs; he IEC/EN covers RCDs wih inegral overcurren proecion, including hose obained by adding a residual curren block o an overcurren circui breaker. 2 Day by DIN 1 15

3 Residual curren waveforms for Type B residual curren circui breakers The new ediion of IEC/EN furher enriches he se of residual curren waveforms wih which he Type B circui breakers mus be esed. The vas number of waveforms conemplaed - which include various unidirecional forms, direc curren wihou ripple, high-frequency currens and differen combinaions of hese - allows i o be said ha a Type B RCD guaranees proper ripping wih every possible faul curren, no maer how srange and complex he device ha generaed i. Therefore, he aribue universal by which he RCD ype B 2) is someimes denoed is fully jusified. The es residual curren waveforms now conemplaed for Type B circui breakers are 3) : sinusoidal alernaing curren a raed frequency; pulsaing unidirecional curren, wih or wihou phase angle delay; unidirecional curren generaed by wo or hree-phase recifiers; sinusoidal alernaing curren up o a frequency of 1 khz; direc curren wihou ripple curren obained by overlapping direc curren on alernaing curren; curren obained by overlapping direc curren on pulsaing unidirecional curren; curren obained by he overlap of several frequencies. alernaing unidirecional pulsaing unidirecional pulsaing wih phase angle delay alernaing overlapped on direc unidirecional pulsaing overlapped on direc muli-frequency wo-phase recified hree-phase recified direc wihou ripple alernaing up o 1 khz Residual curren form Tripping curren limi values IΔn IΔn Cuing angle 90 : from 0.25 o 1.4 IΔn Cuing angle 135 : from 0.11 o 1.4 IΔn max. 1.4 IΔn IΔn DC max. 1.4 IΔn IΔn DC from 0.5 o 1.4 IΔn from 0.5 o 2.0 IΔn Curren frequency 150 Hz from 0.5 o 2.4 IΔn Curren frequency 400 Hz from 0.5 o 6 IΔn Curren frequency 1000 Hz from 0.5 o 14 IΔn 2 Figure 2 - Tripping waveforms for all Type B 2) This erminology should no mislead: Type B RCDs are inended for use on AC volage mains neworks (nonsinusoidal waveforms are hose of residual curren). RCDs for DC mains neworks are being sudied (he so-called Type DC circui breakers). 3) See also he aricle Residual curren proecion devices on Day by DIN 2 14 and he ABB Technical Guide Proecion agains ground fauls wih residual curren circui breakers. Day by DIN

4 The ess on RCDs are performed wih boh polariies, posiive and negaive, wih he residual curren applied boh slowly and suddenly. Differen ripping and non-ripping values are conemplaed for he various waveforms, expressed as a muliple of he raed ripping residual curren I Δn, which is always referred o he AC mains frequency. The limi values of he ripping residual curren ake ino accoun he differen ypes of hazard for people of he various waveforms, and, a he same ime, allow for an increase in service coninuiy while reducing he risk of nuisance ripping in he absence of faul (noise is filered). For example, a Type B RCD wih I Δn = 30 ma, when direc residual curren wihou ripple is applied, has a maximum ripping hreshold of up o 60 ma o ake ino accoun he lesser danger of DC curren. For he same reason, for a 400 Hz frequency residual curren, he maximum ripping value allowed is 180 ma Applicaion of Type B RCDs Type B RCDs are suiable for nonlinear circuis capable of generaing ground faul curren wih a high direc componen (more han 6 ma 4) ) and/or high frequency; he main ones are shown in Table 1. Table 1 - Power circuis ha require Type B residual curren breakers 1 2 Non-linear circui L1 L2 L3 N I B I B Faul waveform L1 L2 L3 N 3 L1 L2 I B I 4 I B L N 5 L N I B I 6 L N 7 4) Type A RCDs are suiable o deec pulsaing residual currens ha, for a period of a leas 8.33 ms in each 20 ms period of he mains frequency (equal o 150 elecrical degrees a 50 Hz), ake on a null value or one no greaer han 6 ma. L1 L2 L3 I B M 4 Day by DIN 1 15

5 These are essenially: recifiers, in general hree-phase or wo-phase (cases 1, 2, 3); half-wave recifiers wih high smoohing capaciy (4); recifiers wih acive power facor correcion (PFC) (5); direc volage generaors permanenly conneced wihou galvanic separaion o alernaing curren neworks (e.g. solar panels) (6); variable frequency drives (7). The main ypes of equipmen ha conain hese circui configuraions are: variable frequency moor drives wih hree-phase power supply (indusrial machinery, elevaors, ec.) (see fig. 5); phoovolaic plans (fig. 6 5) ); saic ransfer sysems (STS) and uninerrupible power sysems (UPS) (see Fig. 3); charging sysems for elecric vehicles powered by alernaing curren (see Fig. 4 6) ); drives in direc curren; frequency converers; medical diagnosic imaging equipmen (CAT, MRI, ec.); and ohers. Please noe ha he mos ypical applicaions of Type B RCDs are hreephase, bu also single-phase applicaions are no excluded, especially hose wih higher power. Figure 3 - The Type B residual curren circui breaker wih use of UPS devices Figure 4 - The Type B residual curren circui breaker for charging elecric vehicles Wh Wh 3 4 5) In case of ground faul on he direc curren side, he RCD locaed downsream of he inverer would be passed hrough, based on he characerisics of he inverer, by a non-alernaing curren, conaining a high direc componen and high frequency. See he ABB Technical Applicaion Paper N 10 Phoovolaic Plans. 6) See Power supply for elecric vehicles in Day by DIN 2 12 and Day by DIN Day by DIN

6 Wh Wh 230 V 230 V M 5 6 Figure 5 - Applicaion o moors powered by variable frequency Figure 6 - PV sysems wihou isolaion ransformer Immuniy o nuisance ripping of Type B RCDs For Type B RCDs, sringen ess of immuniy o nuisance ripping were added in addiion o hose already provided for Type A RCDs. These ess are 7) : normalized surge curren wihsand 8/20 µs up o he value of 3000 A (Fig. 7); insensiiviy o residual currens of duraion up o 10 ms of ampliude up o 10 I Δn (Fig. 8). Wih hese properies, Type B RCDs urn ou o be RCDs wih high immuniy o nuisance ripping caused by grid surges, elecronic loads and EMC filers. Therefore, Type B circui breakers are he ideal soluion for all difficul loads, no only from he poin of view of proecion, bu also in erms of service coninuiy. Where regulaions require Type B RCDs For phoovolaic sysems - in he case of sysems wihou a leas a simple separaion beween he AC side and he DC side - if he converer is no exemp by consrucion design from injecing direc faul currens ino he elecrical sysem, one mus insall a Type B RCD on he AC side (see IEC Ar ). In group 1 and group 2 rooms for medical use, only Type A or Type B RCDs mus be used, according o he ype of possible faul curren (see IEC Ar ). For STSs and UPSs, if heir design conemplaes he possibiliy of ground faul curren wih direc curren componens, heir insallaion insrucions mus sae ha he building s residual curren circui breakers mus be Type B for he UPSs and he hree-phase STSs, and Type A for he single-phase STSs (see IEC/EN Ar and IEC/EN Ar ). 7) This is essenially he same ype of es passed by ABB s Type A APR series RCDs, which feaure high resisance o nuisance ripping. See Coninuiy of supply in Day by DIN Day by DIN 1 15

7 l (A) l max 90% l max (s) % l max % l max ,01 s 0 8μs 20 (μs) l n 2 l n 5 l n 10 l n l shor duraion non-ripping currens maximum ripping ime allowed by he sandard for non- delayed circui breakers 7 8 As for he charging of elecric vehicles, where he charging saion is equipped wih a socke-oule or vehicle connecor complying wih he IEC series, one mus ake proecion measures agains DC faul curren, for example Type B RCDs (see IEC Ar ) 8). More generally, as o he correc choice of he residual curren circui breaker for power elecronics equipmen no included in he previous cases, see IEC 62103/EN (Elecronic equipmen for use in power insallaions), according o which (Aricle ): mobile elecronic equipmen wih raed inpu power 4 kva mus always be designed o be compaible wih Type A RCDs; mobile elecronic equipmen wih raed inpu power > 4 kva or fixed a any power, which are no compaible wih Type A RCDs, mus be provided wih a warning on he device and in he operaing manual o require he use of a Type B RCD or anoher proecion mehod (e.g. isolaion ransformer). How does a Type B RCD work? Type B residual curren circui breakers manufacured according o he Sandard IEC/EN are equipped wih wo ferromagneic oroids in series: one is inended o deec alernaing and pulsaing residual currens, he oher is for direc currens. All live conducors pass hrough boh oroids (phases and neural) so as o form a primary winding of a ransformer on which he residual curren circulaes. The firs oroid works in elecromechanical mode like in a convenional Type A or Type AC circui breaker: a residual curren oscillaing a he mains frequency generaes by elecromagneic inducion a volage across he secondary winding, which, if i reaches a prese hreshold value, causes he release of a demagneizaion acuaor ha acs on he opening mechanism of he conacs. Figure 7 - Surge curren 8/20 µs Figure 8 - Insensiiviy o shor duraion residual currens 8) Proecion device agains DC faul curren can eiher provided by EV charging saion or be par of he upsream insallaions. Day by DIN

8 T1- Toroid Core for Deecion of AC Sinusoidal and Plusaing DC residual curren T2 - Toroid Core for deecing pure DC residual Curren M - Mechanical Trip Uni A - Acuaor E - Elecronics for ripping incase of pure DC leakage Curren T 1 L1 L2 L3 N M A T 2 G E 9 Figure 9 - Schemaic diagram of a Type B circui breaker Figure 10 - Examples of he proper insallaion of a Type B circui breaker Figure 11 - Example of he improper insallaion of a Type B circui The second oroid is used by aking advanage of he magneic sauraion of he ferromagneic maerial. To is secondary winding is permanenly applied an alernaing volage ha magneizes he maerial. An elecronic circui is capable of deecing he inducance across he secondary winding. The appearance of a direc residual curren brings he maerial o sauraion and, consequenly, changes is magneic permeabiliy. This variaion, suiably processed, is he signal ha deermines he release acuaor command. As required by he currenly applicable European sandards, he operaion as a Type A RCD, i.e. he deecion of fauls wih alernaing or pulsaing waveform, is guaraneed even in he oal absence of volage beween he acive conducors (phases and neural). The operaion as Type B, however, requires he presence of a minimum volage on a leas any wo acive conducors. Proper insallaion of Type B RCDs Since Type B residual curren circui breakers are used in he presence of loads ha are able o generae also earh curren wih DC componen, when designing he elecrical sysem i is necessary for any oher RCD insalled upsream of a Type B RCD, passed hrough by he same faul curren, also be of Type B 9). Any direc leakage could impair he proper operaion of he upsream Type AC, A or F residual curren circui breakers, which are no suiable in he case of direc residual currens. In fac, even if he Type B RCD proecs agains direc faul currens, he ripping value (for example 60 ma for a circui breaker wih I Δn = 30 ma) is high enough o compromise he regular operaion of anoher non-type B RCD. I is herefore necessary o derive he power supply of he Type B RCD upsream of any non-type B RCDs, or, if an upsream RCD is required, choose a Type B also for his one. 9) See he Sandard IEC 62103/EN Elecronic equipmen for use in power insallaions, Ar Day by DIN 1 15

9 Wh Wh S n = 300 ma S n = 300 ma n = 30 ma n = 30 ma n = 30 ma n = 30 ma n = 30 ma n = 30 ma 10 Wh S n = 300 ma n = 30 ma n = 30 ma n = 30 ma 11 Day by DIN

10 Proecion agains indirec conac (faul proecion) a high frequencies The maximum ripping values for Type B RCDs wih I Δn no exceeding 30 ma, for he purposes of addiional proecion agains direc conacs, are below he limi curve of he venricular fibrillaion hreshold esablished in Publicaion IEC/TS also in he case of direc or high-frequency curren. To provide faul proecion (proecion agains indirec conac in TT sysems, he circui breaker mus be coordinaed wih he resisance of he grounding sysem wih he cusomary raio: R E n 50 V Wih his coordinaion raio he proecion agains indirec conac is auomaically checked in he case of direc curren fauls, since he permissible limi conac volage in direc curren is 120 V, which corresponds o 50 V in alernaing curren. In he case of high-frequency fauls, however, a permissible limi conac volage has no ye been esablished a he regulaory level. Alhough he risks for he human body decrease as he frequency increases, unil he sandards have se hese values, he Sandard IEC/EN recommends as a precauionary measure o mainain unchanged he value of 50 V also a higher frequencies. To do his, i is necessary o ake ino accoun he acual ripping value of a possible faul frequency. For example, in he case of a ype B circui breaker whose ripping characerisic is ha shown in Figure 12, a 1000 Hz ripping is guaraneed wih a residual curren of 300 ma (lower han he regulaory limi of 420 ma). Therefore, if he consuming equipmen can generae a faul curren a 1000 Hz, he ground resisance mus saisfy he raio i.e. R E 0,3 A 50 V R E 166 Ω 10 Day by DIN 1 15

11 Raed sensiiviy (ma) Frequency (Hz) 12 Figure 12 - Tripping curve in he frequency of a given circui breaker Day by DIN

12 Sysem pro M compac, new F200 B Series Buil o make he difference ABB s echnological excellence has creaed he new F200 B residual curren circui breaker: compac, safe and perfecly inegraed ino he range of modular producs and accessories of Sysem pro M compac. The F200 B residual curren circui breaker guaranees maximum proecion and service coninuiy in any faul condiion. Because ABB s research and echnological innovaion always srives for your safey. Make he righ choice for your safey; choose ABB. For furher informaion: