*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 |

*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*_{2} and *L*_{3}, A |

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

*R*_{20} |
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 |

*S*_{12} |
distance of cable centres between *L*_{1} and *L*_{2}, m |

*S*_{23} |
distance of cable centres between *L*_{2} and *L*_{3}, m |

*S*_{31} |
distance of cable centres between *L*_{3}and *L*_{1}, 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}] |

*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*_{2} and *L*_{3}, V |

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