Symbols - Cables

b	circuit factor (=2 for d.c. and single phase, = 1 for three phase)
C	cable capacitance [ F, μF, F.m^-1]
d_c	diameter of conductor, m
d_s	mean diameter of sheath, m
I₂	operating or tripping current of the protective device, A
I_b	cable design conductor current, A
I_c	cable charging current [A, A.m^-1]
I_n	rated current or current setting of the protective device, A
I₁, I₂, I₃	conductor phase current of L₁, L₂ and L₃, A
I_s1, I_s2, I_s3	sheath phase current of L₁, L₂ and L₃, A
I_t	tabulated current rating for a particular installation condition, A
I_z	sustained current rating of cable under particular installation conditions, A
L	cable inductance [H, mH, mH.m^-1]
L_s	inductance of sheath, H.m-¹
n	number of circuit in a group
R	cable resistance [Ω, Ω.m^-1]
R₂₀	resistance of conductor at 20 °C
Rac	a.c. resistance of cable, Ω.m^-1
R_armou_r	resistance of armour, Ω.m^-1
Rdc	d.c. resistance of cable, Ω.m^-1
R_s	resistance of the sheath, Ω.m^-1
R_t	resistance of conductor at t °C
S	distance between cable centres, m
S₁₂	distance of cable centres between L₁ and L₂, m
S₂₃	distance of cable centres between L₂ and L₃, m
S₃₁	distance of cable centres between L₃and L₁, m
t	conductor [cable] temperature, °C
T_a	ambient temperature, °C
T_c	conductor [insulation] limiting/design temperature, °C
X	cable reactance, general [Ω, Ω.m^-1]
X_c	cable capacitive reactance [Ω, Ω.m^-1]
X_L	cable inductive reactance [Ω, Ω.m^-1]
X₁, X₃, X_a, X_b	reactance formulas; sheath induced voltage, Ω.m^-1
X_m	mutual reactance between conductor and sheath, Ω/unit length
X_s	sheath reactance, Ω.m^-1
Uo	nominal voltage, V
U_s	sheath voltage, V
U₁, U₂, U₃	phase voltage o f L₁, L₂ and L₃, V
U_s1, U_s2, U_s3	sheath inductive phase voltage o f L₁, L₂ and L₃, V
Z	cable impedance [Ω, Ω.m^-1]
ΔU	voltage drop,
ϵ_o	permittivity of free space = 8.854187819x10^-12 F/m
ϵ_r	relative permittivity of a dielectric

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