Ohm Law :

R=U/I

Power (DC) :

P=U.I

Single - Phased power :

P=UI.cosÆ

Three - Phased power :

P=Ö3.U.I.cosÆ

Energy (heat) :

W=I².R.t

Inductive Reactance :

X=2.(3.14).f.a

Resistance of a Line :
(Feeding and Return)

R=(2.L)/(c.S)

Efficiency :

h=Poutput/

Voltage Drop

If Current is known

If Power is known

In D.C .Systems

DU=(2.I.L)/(c.S)--------- (V)

%e=(2.100.I.L)/(c.S.U)

DU=(2.L.P)/(c.S.U)---- (V)

%e=(2.100.L.P)/(c.S.U²)

In single-phased A.C. Systems

DU=(2.I.L.cosÆ)/(c.S)---- (V)

%e=(2.100.I.L.cosÆ)/(c.S.U)

DU=(2.L.P)/(c.S.U)---- (V)

%e=(2.100.L.P)/(c.S.U²)

In three-phased A.C. Systems

DU=(Ö3.I.L.cosÆ)/(c.S)---- (V)

%e=(Ö3.100.I.L.cosÆ)/(c.S.U)

DU=(L.P)/(c.S.U)(V)

%e=(100.L.P)/(c.S.U²)

U

Rated Voltage

I

Current

R

Resistance

h

Efficiency

t

Time (in seconds)

S

Cross-section (mm²)

L

Lenght of cable (m)

a

Inductance of cable

P

Power (in Watts)

cosÆ

Power in Factor

c

Conductivity (For Copper 58)

W

Energy (heat)

U

Voltage drop in V from sending to receiving end of line (V)

X

Inductive reactance

%e

Voltage drop in % from sending to receiving end of line (%)

f

Frequency of the line