7/29/2019 630Short Circuit Current Calculation

http://slidepdf.com/reader/full/630short-circuit-current-calculation 1/1

Ra (mΩ) Xa(mΩ) Ra (mΩ) Xa(mΩ)

UN-LL  (kV) 11 = 0.1 x Xa = 0.995 x (U22o / Psc)

Psc ( MVA) 350 0,041 0,411

U20 (V) 380 Rtr  (mΩ) Xtr  (mΩ)

Pn (kVA) 630 =Pcu * 1000/3 * In =√ Z2tr - R

2tr 

Usc (%) 6 In = (Pn *1000)/(√3* U2o ) Ztr =U2

2o*Usc /( Pn * 100) RT = R + Ra XT = X + Xa

Pcu ( Watt ) 7.600

In (A) 957

Ztr (mΩ) 13,75

RL (mΩ) XL (mΩ)

= (22,5 /3) x (L/CSA) = 0,08 x LType XLPE

Length-L(m) 15,00

Number-n(nil) 3

Iscw(kA) 34,3

Short Circuit Current at Transformer Secondary (Terminals)

Main Cable

Csa(mm²)

240

Short Circuit Current at MDB

RT (mΩ) XT (mΩ) ISC ( kA ) =

U2o / ( √3 * √ ( R2T +X

2T))

2,765 13,472 2,806 13,882 15,5

For the downstream cables refer to Cable/Feeder sheets

Short circuit current of cable from manufacturer's data sheets,

which is valid for one core is higher than 15,5kAVERIFIED

From MDB to SMD Downstream circuits

RT (mΩ) XT (mΩ) ISC ( kA ) =

0,469 1,200 3,275 15,082 14,2

Short Circuit Current Calculation

INsc (kA) =

0,041 0,411

Psc (MVA) / √3 * UN-LL

18,4

Short Circuit Current at Transformer Primary (MV Network)

MDB-1

3x(4x240mm²)

Cu, XLPE/PVC

L=15m

ISC 

ISC 

SMDB-1

SMDB-2

MDB-2

ISC 

ISC 

INsc

TRA-1630kVA

Usc = % 611kV/380V

MV

Network 350MVA