Page 25 - IZOELEKTRO catalogue 06-2020

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SN odvodniki prenapetosti MV surge arresters

2.5 Razred DH - izračun in izbira 2.5 Class DH - calculation and selection

2.5.1 Izračun 2.5.1 Calculation

Podatki omrežja distributerja Data of electric network
• Um – maksimalna napetost • Um – maximum voltage
• t – čas trajanja kratkega stika • t – short circuit duration time
• kz – faktor zemeljskega stika • kz – factor of earthing
kz = 1,40 – neposredno ozemljeno kz = 1,40 – directly earthed
kz = 1,40 – 1,7 z malim uporom kz = 1,40 – 1,7 with little resistance
kz = 1,73 – 1,8 z izolirano nevtralno točko kz = 1,73 – 1,8 with a neutral insulated spot

Podatki odvodnikov SNO Data for surge arresters types SNO
• k0 = 0,8 • k0 = 0,8
• k t = faktor nazivne napetosti za časno • k t = factor of rated voltage for temporary over
prenapetost. voltage duration time.

Karakteristike za tip SNO Characteristics for type SNO

1,2
1,15

1,1
Legenda: 1,05 Legend:
Krivulja T1: U r (p.u.) Curve T1:
brez predhodne 1 without prior
energije energy
0,95
Krivulja T2: 0,9 Curve T2:
T2 T1
2 x 34 kA, 8/20 μs 0,85 2 x 34 kA, 8/20
predhodna energija 0,1 1 10 100 1000 10000 prior energy
t [s]

Izračun Calculation
• Nazivna napetost sistema: • Rated voltage of system:

x 1,25 [kV] x 1,25 [kV]

• Predhodna nazivna napetost odvodnika: • Preliminary rated voltage of surge arrester:

[kV] [kV]

• Najvišja pričakovana časna prenapetost odvodnika: • Highest expected transient over voltage of surge arrester:

[kV] [kV]

• Nazivna obratovalna napetost odvodnika: • Rated voltage of surge arrester:

[kV] [kV]

2.5.2 Izbira 2.5.2 Selection

Ustrezen odvodnik prenapetosti izberemo iz tabel s We choose a suitable surge arrester from tables with data
podatki, na podlagi višje izračunane vrednosti med Ur1 based on higher calculated value between Ur1 and Ur2 so,
in Ur2 tako, da izberemo prvo višjo nazivno napetost Ur, that we choose the first higher value of rated voltage Ur
ki je podana v tabeli. specified in the table.

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