Published On: Sat, Nov 14th, 2020

Nešto o strujama curenja i FID sklopka

Nešto o strujama curenja i FID sklopka

Obradio Radoje Jankovic. prema katalogu proizvođača

Stalne neželjene struje “Struje curenja (leakage current)” frekvencije 50/60Hz

Struje curenja su one struje koje najčešće nastaju zbog oslabljene izolacije vodiča, prisutnosti filtera odnosno kapaciteta između linijskih vodiča i zemlje.

Ukupna struja curenja je zbroj svih tih struja curenja koje kroz uzemljenje prolaze prema zemlji.
Norma IEC 61140 propisuje najviše dopuštene vrijednosti neželjenih struja curenja za stalno priključene terete kao i za terete priključene preko utikača/utičnica (do 32 A).

Dopuštene vrijednosti neželjenih struja curenja (ovisno o nazivnoj struji uređaja) za uređaje spojene preko 1-fazne ili 3-fazne utičnice iznose:
• Za uređaje nazivne struje do 4 A maksimalna dopuštena struja curenja je 2mA
• Za uređaje nazivne struje od 4 – 10 A maksimalna dopuštena struja curenja je 0,5mA / A (npr. za uređaj od 5 A ta struja bi bila 2,5 mA)
• Za uređaje nazivne struje od 10 – 32 A maksimalna dopuštena struja curenja je 5mA
Neke karakteristične vrijednosti struja curenja kod uređaja su:
• Računala: 1 do 2 mA
• Printeri: 0,5 do 1 mA
• Mali prijenosni uređaji (mikser, fen,…): 0,5 do 0,75 mA
• Frekventni pretvarači sa ugrađenim B filterom: 5 do 25 mA

Ove neželjene struje mogu dovesti i do neželjenih okidanja FID sklopke.

Ako imamo npr. 10 PC-ja na istom strujnom krugu kako je to prikazano na prvoj slici i ako svaki PC ima curenje (leakage current) od 2mA => 10×2=20mA što znači da FID sklopka od 30mA već smije isklopiti (jer prema normi RCD sklopka smije isklopiti od 50-100% nazivne diferencijalne struje). U strujnim krugovima sa većim brojem računala poželjno je da jedna FID sklopka od 30mA ne štiti više od 4 računala.

Sl. 1.

Preporuka je da struje curenja u jednom strujnom krugu ne prelaze 35% nazivne proradne struje FID sklopke.

U slučaju kada ta vrijednost prijeđe 35% preporuča se razdijeliti strujni krug na više podkrugova, te svaki od podkrugova ponovo štititi odgovarajućom FID sklopkom.

Preporuka je također da se na dovodu cijeli strujni krug opet štiti sa (glavnom) FID sklopkom. Ta glavna FID sklopka mora biti selektivna (Tip S) odnosno imati vremensko zatezanje reakcije.

Druga slika prikazuje sklopku V-BCPo 63/4/03-S/A.
Serija PRIORI, Tip A (osjetljiva na pulsne struje), Izvedba Selektivna (tip S), Norma EN 61008

Sl. 2.

Treća slika prikazuje FID skloku 63-4-01/A, S izvedba
Serija BC serija, Tip A (osjetljiva na pulsne struje), Izvedba Selektivna (tip S), Norma EN 61008

Sl. 3.

Četvrta slika prikazuje FID sklopku BCFO 63/4/01-5/A

Sl. 4.

Sve FID sklopke imaju mogućnost za postavljanje signalnih kontakata (Sl. 5) i pomoćnog kontakta (Sl. 6)prema potrebi I zahtevu projektanta ili procesa rada.

Author is used factory documentation of Schrack.

About the Author

- Radoje - Rade Jankovic Electrician, Electrical Technician, Electrical Engineer, PhD, Ecologist, Environmentalist, Designer, Educator, Investigator... Today PROFESSIONAL TECHNICAL WRITER AND DOCUMENTATOR Massive practical experience in almost all fields of electrical engineering over 40 years. My International education group in Facebook: EEEW - ELECTRICAL & ELECTRONIC EDUCATION WORLD where published more than 8000 small or bigger articles, lessons, technical advice, projects, technical calculations, test questions with and without answers, illustrated test questions with and without answers; all my original works and few thousands of may original photos from practice, drawings, circuit diagrams, environmental lessons and examples from everyday practice etc., etc.

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Nešto o strujama curenja i FID sklopka