## 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 |

d_{s} |
mean diameter of |

I_{2} |
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 |

I, _{1}I, _{2}I_{3} |
conductor phase current of L, _{1}L and _{2}L, A_{3} |

I, _{s1}I, _{s2}I_{s3} |
sheath phase current of L, _{1}L and _{2}L, A_{3} |

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 |

R |
cable resistance [Ω, Ω.m^{-1}] |

R_{20} |
resistance of conductor at 20 °C |

Rac |
a.c. ^{-1} |

R_{armou}_{r} |
resistance of armour, Ω.m^{-1} |

Rdc |
d.c. ^{-1} |

R_{s} |
resistance of the sheath, Ω.m^{-1} |

R_{t} |
resistance of conductor at t °C |

S |
distance between cable centres, m |

S_{12} |
distance of cable centres between L and _{1}L, m_{2} |

S_{23} |
distance of cable centres between L and _{2}L, m_{3} |

S_{31} |
distance of cable centres between Land _{3}L, m_{1} |

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}] |

X, _{1}X, _{3}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 |

U, _{1}U, _{2}U_{3} |
phase voltage o f L, _{1}L and _{2}L, V_{3} |

U, _{s1}U, _{s2}U_{s3} |
sheath inductive phase voltage o f L, _{1}L and _{2}L, V_{3} |

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 |