| A | $a_{\mathrm{0}}$ | Coefficient a for partial transient temp. rise | s² |
| $a_{\mathrm{12}}$ | Distance between phase 1 and 2 | mm |
| $a_{\mathrm{23}}$ | Distance between phase 2 and 3 | mm |
| $a_{\mathrm{31}}$ | Distance between phase 3 and 1 | mm |
| $A_{\mathrm{a}}$ | Cross-sectional area of armour | mm² |
| $A_{\mathrm{a_{\mathrm{1}}}}$ | Cross-sectional area of 1st armour | mm² |
| $A_{\mathrm{a_{\mathrm{2}}}}$ | Cross-sectional area of 2nd armour | mm² |
| $A_{\mathrm{ab_{\mathrm{1}}}}$ | Area of 1st armour bedding | mm² |
| $A_{\mathrm{ab_{\mathrm{2}}}}$ | Area of 2nd armour bedding | mm² |
| $A_{\mathrm{c}}$ | Conductor cross-section | mm² |
| $A_{\mathrm{comp}}$ | Cross-sectional area of gas compartment | m² |
| $a_{\mathrm{constr}}$ | Construction of armour | - |
| $A_{\mathrm{d}}$ | Area of duct material | mm² |
| $A_{\mathrm{d_{\mathrm{fill}}}}$ | Area of duct filling material | mm² |
| $A_{\mathrm{encl}}$ | Cross-sectional area of enclosure | mm² |
| $A_{\mathrm{f}}$ | Area of filler | mm² |
| $A_{\mathrm{i}}$ | Area of insulation | mm² |
| $A_{\mathrm{j}}$ | Area of jacket/oversheath | mm² |
| $A_{\mathrm{k}}$ | Thermal property constant A | (mm²/s)½ |
| $a_{\mathrm{m}}$ | Mean distance between the phases | mm |
| $A_{\mathrm{prot}}$ | Cross-sectional area of protective cover | mm² |
| $a_{\mathrm{S1}}$ | Length of 1st cable section | p.u. |
| $a_{\mathrm{S2}}$ | Length of 2nd cable section | p.u. |
| $a_{\mathrm{S3}}$ | Length of 3rd cable section | p.u. |
| $A_{\mathrm{sc}}$ | Cross-sectional area of screen | mm² |
| $A_{\mathrm{scb}}$ | Area of screen beddig | mm² |
| $A_{\mathrm{scs}}$ | Area of screen serving | mm² |
| $A_{\mathrm{sh}}$ | Cross-sectional area of sheath | mm² |
| $a_{\mathrm{T}}$ | Distance a of multilayer backfill | m |
| $A_{\mathrm{t}}$ | Cross-sectional area of the tunnel | m² |
| $\alpha_{\mathrm{ar}}$ | Temperature coefficient of armour material | 1/K |
| $\alpha_{\mathrm{c}}$ | Temp. coefficient of conductor material | 1/K |
| $\alpha_{\mathrm{f}}$ | Phase shifting | ° |
| $\alpha_{\mathrm{gas}}$ | Thermal diffusivity of gas | m2/s |
| $\alpha_{\mathrm{M}}$ | Factor αM | - |
| $\alpha_{\mathrm{sc}}$ | Temperature coefficient of screen material | 1/K |
| $\alpha_{\mathrm{sh}}$ | Temperature coefficient of sheath material | 1/K |
| $\alpha_{\mathrm{t}}$ | Conductor to cable surface attainment factor | - |
| B | $B$ | Susceptance | S/m |
| $b_{\mathrm{0}}$ | Coefficient b for partial transient temp. rise | 1/s |
| $B_{\mathrm{1_{\mathrm{1}}}}$ | Loss coefficient B1 of 1st armour | Ω/m |
| $B_{\mathrm{1_{\mathrm{2}}}}$ | Loss coefficient B1 of 2nd armour | Ω/m |
| $B_{\mathrm{2_{\mathrm{1}}}}$ | Loss coefficient B2 of 1st armour | Ω/m |
| $B_{\mathrm{2_{\mathrm{2}}}}$ | Loss coefficient B2 of 2nd armour | Ω/m |
| $B_{\mathrm{EMF}}$ | Magnetic field strength | µT |
| $B_{\mathrm{k}}$ | Thermal property constant B | mm²/s |
| $b_{\mathrm{T}}$ | Distance b of multilayer backfill | m |
| $b_{\mathrm{x}}$ | Shorter side of backfill | mm |
| $b_{\mathrm{y}}$ | Longer side of backfill | mm |
| $\beta_{\mathrm{1}}$ | Substitution coefficient β1 for eddy-currents | - |
| $\beta_{\mathrm{6}}$ | Factor |1 - β(6)| | - |
| $\beta_{\mathrm{a_{\mathrm{1}}}}$ | Angle armour/cable | rad |
| $\beta_{\mathrm{a_{\mathrm{2}}}}$ | Angle 2nd armour/cable | rad |
| $\beta_{\mathrm{ar}}$ | Reciprocal of temperature coefficient of armour | K |
| $\beta_{\mathrm{c}}$ | Reciprocal of temperature coefficient of conductor material | K |
| $\beta_{\mathrm{gas}}$ | Volumetric thermal expansion coefficient | 1/K |
| $\beta_{\mathrm{k}}$ | Reciprocal of temp. coefficient of resistance | K |
| $\beta_{\mathrm{M}}$ | Factor βM | - |
| $\beta_{\mathrm{sc}}$ | Values for reciprocal of temperature coefficient of screen material | K |
| $\beta_{\mathrm{sh}}$ | Reciprocal of temperature coefficient of screen material | K |
| $\beta_{\mathrm{t}}$ | Cable surface to ambient attainment factor | °C |
| $\beta_{\mathrm{X}}$ | Crossing angle | rad |
| $\beta_{\mathrm{xing}}$ | Crossing angle | ° |
| C | $C_{\mathrm{av}}$ | Heat capacity of the air flow | W/K |
| $C_{\mathrm{b}}$ | Capacitance of insulation | F/m |
| $c_{\mathrm{constr}}$ | Construction of conductor | - |
| $c_{\mathrm{ij}}$ | View factor coefficient | - |
| $C_{\mathrm{k1}}$ | Non-adiabatic constant C1 | mm/m |
| $C_{\mathrm{k2}}$ | Non-adiabatic constant C2 | K.m.mm²/J |
| $C_{\mathrm{Nu}}$ | Factor C | - |
| $c_{\mathrm{p_{\mathrm{gas}}}}$ | Specific heat capacity at constant pressure | J/kg.K |
| $C_{\mathrm{q}}$ | Constants multilayer backfill | - |
| $c_{\mathrm{SI}}$ | Surge velocity of propagation | km/s |
| $c_{\mathrm{T}}$ | Distance c of multilayer backfill | m |
| $c_{\mathrm{v_{\mathrm{gas}}}}$ | Specific heat capacity at constant volume | J/kg.K |
| $C_{\mathrm{vair}}$ | Volumetric heat capacity of air | J/K.m³ |
| $CC$ | Charging capacity | kvar/km |
| $CC_{\mathrm{p}}$ | Conduit clearance | % |
| $CF_{\mathrm{p}}$ | Conduit fill | % |
| $CR_{\mathrm{p}}$ | Conduit ratio | % |
| $cuw$ | Standard copper wires | mm |
| D | $D_{\mathrm{1}}$ | Diameter below screen | mm |
| $D_{\mathrm{2_{\mathrm{1}}}}$ | Diameter below 1st armour | mm |
| $D_{\mathrm{2_{\mathrm{2}}}}$ | Diameter below 2nd armour | mm |
| $d_{\mathrm{a}}$ | Mean diameter of armour | mm |
| $d_{\mathrm{a_{\mathrm{1}}}}$ | Mean diameter of 1st armour | mm |
| $D_{\mathrm{a_{\mathrm{1}}}}$ | External diameter of 1st armour | mm |
| $D_{\mathrm{a_{\mathrm{2}}}}$ | External diameter of 2nd armour | mm |
| $d_{\mathrm{a_{\mathrm{2}}}}$ | Mean diameter of 2nd armour | mm |
| $d_{\mathrm{b}}$ | Diameter of the backfill area | mm |
| $d_{\mathrm{c}}$ | External diameter of conductor | mm |
| $D_{\mathrm{c}}$ | Diameter of conductor | m |
| $d_{\mathrm{ci}}$ | Internal diameter of conductor | mm |
| $D_{\mathrm{comp}}$ | Diameter of gas compartment | m |
| $d_{\mathrm{ct}}$ | External diameter of conductor for transient calculations | mm |
| $d_{\mathrm{e}}$ | Diameter of sheath and armour | mm |
| $D_{\mathrm{e}}$ | External diameter of cable | mm |
| $D_{\mathrm{encl}}$ | Outer diameter of enclosure | mm |
| $D_{\mathrm{eq}}$ | Equivalent diameter of a group of cables | mm |
| $d_{\mathrm{f}}$ | Spacing from hottest cable | m |
| $D_{\mathrm{f}}$ | External diameter of the filler | mm |
| $d_{\mathrm{f_{\mathrm{1}}}}$ | Thickness of 1st armour | mm |
| $d_{\mathrm{f_{\mathrm{2}}}}$ | Thickness of 2nd armour | mm |
| $D_{\mathrm{hs}}$ | External diameter of heat source | mm |
| $D_{\mathrm{i}}$ | Diameter over insulation | mm |
| $d_{\mathrm{im}}$ | Imaginary layer of soil | m |
| $D_{\mathrm{it}}$ | Diameter below sheath | mm |
| $D_{\mathrm{o}}$ | Outside diameter of cylinder in air | m |
| $D_{\mathrm{oc}}$ | External diameter of sheath | mm |
| $d_{\mathrm{pk1}}$ | Distance to mirrored buried cable | mm |
| $d_{\mathrm{pk2}}$ | Distance between buried cables | mm |
| $D_{\mathrm{prot}}$ | Outer diameter of protective cover | mm |
| $D_{\mathrm{s}}$ | Mean external diameter of the sheath | mm |
| $d_{\mathrm{s}}$ | Mean diameter of sheath | mm |
| $D_{\mathrm{scm}}$ | Mean diameter of screen | mm |
| $d_{\mathrm{soil}}$ | Soil dry density | kg/m³ |
| $d_{\mathrm{T}}$ | Distance d of multilayer backfill | m |
| $d_{\mathrm{x}}$ | Equivalent diameter of a conductor | mm |
| $D_{\mathrm{x}}$ | Characteristic diameter | mm |
| $D_{\mathrm{x_{\mathrm{w}}}}$ | Characteristic diameter for weekly load | mm |
| $D_{\mathrm{x_{\mathrm{y}}}}$ | Characteristic diameter for yearly load | mm |
| $DC_{\mathrm{p}}$ | Diameter factor in duct | % |
| $\delta $ | Equivalent thickness of armour | mm |
| $\Delta _{\mathrm{1}}$ | Substitution coefficient Δ1 for eddy-currents | - |
| $\delta _{\mathrm{1}}$ | Thickness of screening layer | mm |
| $\Delta _{\mathrm{2}}$ | Substitution coefficient Δ2 for eddy-currents | - |
| $\delta _{\mathrm{k}}$ | Thickness of screen, sheath or armour | mm |
| $\delta _{\mathrm{soil}}$ | Soil thermal diffusivity | m²/s |
| $\Delta d_{\mathrm{sh}}$ | Depth of corrugation | mm |
| $\Delta H_{\mathrm{c}}$ | Heat of combustion coefficient | MJ/kg |
| $\Delta t$ | Length of time step | s |
| $\Delta T_{\mathrm{4}}$ | Thermal resistance rise | K./W |
| $\Delta \theta_{\mathrm{0t}}$ | Air temperature in tunnel increase | K |
| $\Delta \theta_{\mathrm{0x}}$ | Temperature rise of the conductor | K |
| $\Delta \theta_{\mathrm{0x_{\mathrm{1}}}}$ | Temperature rise of the conductor, first estimate | K |
| $\Delta \theta_{\mathrm{0x_{\mathrm{h}}}}$ | Temperature rise of the conductor by source h | K |
| $\Delta \theta_{\mathrm{a_{\mathrm{t}}}}$ | Corrected transient temp. rise of conductor | K |
| $\Delta \theta_{\mathrm{c}}$ | Temperature rise of conductor | K |
| $\delta \theta_{\mathrm{c}}$ | Ohmic steady-state temperature rise | K |
| $\Delta \theta_{\mathrm{c_{\mathrm{t}}}}$ | Transient ohmic temp. rise of conductor | K |
| $\Delta \theta_{\mathrm{d}}$ | Temperature rise by dielectric losses | K |
| $\Delta \theta_{\mathrm{d_{\mathrm{t}}}}$ | Transient temperature rise by dielectric losses | K |
| $\Delta \theta_{\mathrm{e_{\mathrm{t}}}}$ | Transient temperature rise of outer surface | K |
| $\Delta \theta_{\mathrm{kp}}$ | Temperature rise by buried cable k | K |
| $\Delta \theta_{\mathrm{max}}$ | Maximum permissible conductor temperature rise | K |
| $\Delta \theta_{\mathrm{p}}$ | Temperature rise by other buried cables | K |
| $\Delta \theta_{\mathrm{R}}$ | Conductor temp. rise above ambient | K |
| $\Delta \theta_{\mathrm{R_{\mathrm{\infty}}}}$ | Temperature rise in max. permissible | °C |
| $\Delta \theta_{\mathrm{R_{\mathrm{t}}}}$ | Temperature rise neglecting resistance change | °C |
| $\Delta \theta_{\mathrm{s}}$ | Difference surface temperature to ambient | K |
| $\delta \theta_{\mathrm{SPK}}$ | Peak cyclic temperature rise | K |
| $\Delta \theta_{\mathrm{sun}}$ | Temperature rise by solar radiation | K |
| $\Delta \theta_{\mathrm{t}}$ | Transient temp. rise of conductor | K |
| $\Delta \theta_{\mathrm{t_{\mathrm{\infty}}}}$ | Conductor steady-state temp. rise of conductor) | K |
| $\Delta \theta_{\mathrm{tr}}$ | Air temperature increase in trough | K |
| $\Delta \theta_{\mathrm{x}}$ | Critical soil temperature rise | K |
| $\Delta W$ | Incremental heat generated | W |
| $\Delta W_{\mathrm{0}}$ | Incremental heat generated | W |
| $\Delta z$ | Length of the interval | m |
| $DF_{\mathrm{X}}$ | Ratio of the permissible current | - |
| $Di_{\mathrm{d}}$ | Inside diameter of duct | mm |
| $Di_{\mathrm{t}}$ | Diameter of the tunnel (inner) | m |
| $Do_{\mathrm{d}}$ | Outside diameter of duct | mm |
| $Do_{\mathrm{t}}$ | Diameter of the tunnel (outer) | m |
| E | $E_{\mathrm{bs}}$ | Installation constant E | - |
| $e_{\mathrm{hor}}$ | Horizontal clearance | mm |
| $E_{\mathrm{stress}}$ | Electrical stress | kV/mm |
| $e_{\mathrm{ver}}$ | Vertical clearance | mm |
| $e_{\mathrm{wall}}$ | Clearance to wall | mm |
| $EEC$ | Embodied energy and carbon | kg/kg |
| $\epsilon_{\mathrm{0}}$ | Vacuum permittivity | F/m |
| $\epsilon_{\mathrm{c}}$ | Effective emissivity of conductor | - |
| $\epsilon_{\mathrm{comp}}$ | Dielectric constant of compartment gas | - |
| $\epsilon_{\mathrm{encl}}$ | Effective emissivity of enclosure | - |
| $\epsilon_{\mathrm{i}}$ | Relative permittivity of insulation | - |
| $\epsilon_{\mathrm{k}}$ | Heat loss allowance factor | - |
| $\eta_{\mathrm{gas}}$ | Gas dynamic viscosity | Pa.s |
| $\eta_{\mathrm{gas0}}$ | Gas reference dynamic viscosity | Pa.s |
| F | $f$ | System frequency | Hz |
| $F_{\mathrm{a_{\mathrm{1}}}}$ | Effective length per unit lay length of 1st armour | mm |
| $F_{\mathrm{a_{\mathrm{2}}}}$ | Effective length per unit lay length of 2nd armour | mm |
| $F_{\mathrm{cable}}$ | Maximum pulling force | N/m |
| $f_{\mathrm{cb}}$ | Factor for cross-bonded earthing | - |
| $F_{\mathrm{e}}$ | Factor for eddy-current losses | - |
| $F_{\mathrm{eq}}$ | Mutual heating coefficient | - |
| $F_{\mathrm{ij}}$ | View factor cable-cable | - |
| $F_{\mathrm{in}}$ | Pulling force beginning of section | daN |
| $F_{\mathrm{k}}$ | Imperfect thermal contact factor | - |
| $F_{\mathrm{m}}$ | Radiation coefficient mutual | - |
| $F_{\mathrm{out}}$ | Pulling force end of section | daN |
| $F_{\mathrm{ppc}}$ | Permissible pull force on cable | daN |
| $f_{\mathrm{ppc}}$ | Permissible pull factor | N/mm² |
| $F_{\mathrm{x}}$ | Geometrical distance factor for multi-core cables | - |
| G | $g$ | Standard acceleration of gravity | m/s² |
| $G$ | Conductance | S/m |
| $G_{\mathrm{1}}$ | Geometric factor | - |
| $G_{\mathrm{2}}$ | Geometric factor with separate sheaths | - |
| $G_{\mathrm{b}}$ | Geometric factor for backfill | - |
| $g_{\mathrm{bs}}$ | Installation constant g | - |
| $G_{\mathrm{encl}}$ | Factor to calculate Nusselt number | - |
| $g_{\mathrm{s}}$ | Substitution coefficient gs for eddy-currents | - |
| $G_{\mathrm{s00}}$ | Factor Gs0.0 | - |
| $G_{\mathrm{s05}}$ | Factor Gs 0.5 | - |
| $G_{\mathrm{s10}}$ | Factor Gs 1.0 | - |
| $\gamma_{\mathrm{a}}$ | Armour angle | rad |
| $\gamma_{\mathrm{t}}$ | Attainment factor for groups of cables | - |
| $\gamma_{\mathrm{X}}$ | Attenuation factor cable crossing | 1/m |
| $GMD$ | Geometric mean distance | mm |
| $GMR$ | Geometric mean radius | mm |
| $\mathrm{Gr}_{\mathrm{L}}$ | Grashof number | - |
| H | $h_{\mathrm{1}}$ | Factor h1 for emergency load | - |
| $H_{\mathrm{1}}$ | Component of inductance H1 | H/m |
| $H_{\mathrm{1_{\mathrm{2}}}}$ | Component of inductance H1.2 | H/m |
| $H_{\mathrm{2}}$ | Component of inductance H2 | H/m |
| $h_{\mathrm{2}}$ | Factor h2 for emergency load | - |
| $H_{\mathrm{2_{\mathrm{2}}}}$ | Component of inductance H2.2 | H/m |
| $H_{\mathrm{3}}$ | Component of inductance H3 | H/m |
| $H_{\mathrm{3_{\mathrm{2}}}}$ | Component of inductance H3.2 | H/m |
| $h_{\mathrm{b}}$ | Height of the backfill area | mm |
| $h_{\mathrm{bs}}$ | Heat dissipation coefficient for black surfaces in free air | W/m²/K5/4 |
| $H_{\mathrm{c}}$ | Heat energy content | MJ/m |
| $h_{\mathrm{c}}$ | Convective heat transfer coefficient conductor-gas | - |
| $h_{\mathrm{encl}}$ | Convective heat transfer coefficient gas to enclosure | - |
| $h_{\mathrm{lg}}$ | Ratio of heat dissipation coefficients | - |
| $h_{\mathrm{prot}}$ | Convective heat transfer coefficient GIL-air | - |
| $h_{\mathrm{roll}}$ | Height of roller above bottom | m |
| $H_{\mathrm{s}}$ | Sheath conductance | H/m |
| $H_{\mathrm{sun}}$ | Intensity of solar radiation | W/m² |
| $h_{\mathrm{t}}$ | Inner height | m |
| $H_{\mathrm{T}}$ | Trench depth | m |
| $h_{\mathrm{T4}}$ | Ratio of thermal resistance | - |
| $H_{\mathrm{tc}}$ | Parameter for trough | - |
| $h_{\mathrm{tr}}$ | Heat transfer coefficient | W/K.m2 |
| $H_{\mathrm{ts}}$ | Parameter depending on air velocity | - |
| $H_{\mathrm{x}}$ | Magnetic field x-component | mH |
| $H_{\mathrm{y}}$ | Magnetic field y-component | mH |
| I | $I_{\mathrm{1}}$ | Steady-state current before transient | A |
| $I_{\mathrm{2}}$ | Emergency load current | A |
| $I_{\mathrm{c}}$ | Permissible current rating | A |
| $I_{\mathrm{C}}$ | Capacitive load current | A/km |
| $I_{\mathrm{c_{\mathrm{peak}}}}$ | Permissible peak cyclic load current | A |
| $I_{\mathrm{Ce}}$ | Capacitive earth short-circuit current | A/km |
| $I_{\mathrm{EMF}}$ | Phase current for EMF calculation | A |
| $I_{\mathrm{k}}$ | Permissible short-circuit current | kA |
| $I_{\mathrm{kAD}}$ | Short-circuit current (adiabatic basis) | kA |
| $I_{\mathrm{kSC}}$ | Known short-circuit current | kA |
| $I_{\mathrm{R}}$ | Conductor transient current, step value | A |
| $inst_{\mathrm{air}}$ | Installation of cables in air | - |
| $inst_{\mathrm{sea}}$ | Installation of cables in sea | - |
| $inst_{\mathrm{t}}$ | Installation of cables in air | - |
| J | $j_{\mathrm{max}}$ | Phase angle range | ° |
| $JR_{\mathrm{p}}$ | Jam ratio in duct | % |
| K | $K$ | Screening factor | - |
| $K_{\mathrm{02}}$ | Factor K0.2 | - |
| $K_{\mathrm{06}}$ | Factor K0.6 | - |
| $k_{\mathrm{1}}$ | Thermal conductivity top backfill layer | W/K.m |
| $K_{\mathrm{10}}$ | Factor K1.0 | - |
| $k_{\mathrm{2}}$ | Temperature rise ratio δθSPK/δθc | p.u. |
| $k_{\mathrm{3}}$ | Thermal conductivity cable bedding | W/K.m |
| $K_{\mathrm{A}}$ | Coefficient calculate cables in air | - |
| $k_{\mathrm{air}}$ | Thermal conductivity of air | W/m.K |
| $K_{\mathrm{BICC}}$ | Constant relating to conductor formation | - |
| $k_{\mathrm{Boltzmann}}$ | Boltzmann constant | J/K |
| $k_{\mathrm{c}}$ | Thermal conductivity of conductor material | K.m/W |
| $k_{\mathrm{comp}}$ | Thermal conductivity of gas compartment | mW/m.K |
| $K_{\mathrm{cv}}$ | Convection factor | - |
| $K_{\mathrm{E}}$ | Surface conductance | W/m² |
| $k_{\mathrm{encl}}$ | Thermal conductivity of enclosure | W/m.K |
| $k_{\mathrm{gas}}$ | Thermal conductivity of gas | W/m.K |
| $K_{\mathrm{GMR}}$ | Geometric mean radius factor | - |
| $K_{\mathrm{k}}$ | Constant depending on the material | A.s½/mm² |
| $k_{\mathrm{l}}$ | Temperature rise factor in air | - |
| $k_{\mathrm{LF}}$ | Load loss constant coefficient | p.u. |
| $k_{\mathrm{p}}$ | Proximity effect coefficient of conductor | - |
| $k_{\mathrm{prot}}$ | Thermal conductivity of protective cover | W/m.K |
| $K_{\mathrm{r}}$ | Radiation shape factor | - |
| $k_{\mathrm{s}}$ | Skin effect coefficient of conductor | - |
| $k_{\mathrm{t}}$ | Temperature rise ratio | p.u. |
| $K_{\mathrm{t}}$ | Effective emissivity | - |
| $k_{\mathrm{X}}$ | Number of heat sources crossing | - |
| $K_{\mathrm{x}}$ | Factor for fictitious diameter by Neher | - |
| L | $L_{\mathrm{0}}$ | Reference length of the tunnel | m |
| $L_{\mathrm{1}}$ | Inductance of phase 1 | H/m |
| $L_{\mathrm{2}}$ | Inductance of phase 2 | H/m |
| $L_{\mathrm{3}}$ | Inductance of phase 3 | H/m |
| $L_{\mathrm{b}}$ | Vertical center position of backfill | mm |
| $L_{\mathrm{c}}$ | Depth of laying of sources | mm |
| $L_{\mathrm{char}}$ | Characteristic length | - |
| $L_{\mathrm{cm}}$ | Depth of laying | m |
| $L_{\mathrm{cni}}$ | Imaginary laying depth with non-isothermal earth surface | m |
| $L_{\mathrm{deep}}$ | Equivalent depth for deep burial | m |
| $L_{\mathrm{h}}$ | Depth of laying of crossing element | mm |
| $L_{\mathrm{m}}$ | Mean inductance of the phases | H/m |
| $L_{\mathrm{p}}$ | Length of section | m |
| $L_{\mathrm{psc}}$ | Point source correction | m |
| $L_{\mathrm{r}}$ | Depth of laying of the rated cable | mm |
| $L_{\mathrm{sys}}$ | System length | km |
| $L_{\mathrm{T}}$ | Length of the tunnel | m |
| $\lambda_{\mathrm{0}}$ | Substitution coefficient λ0 for eddy-currents | - |
| $\lambda_{\mathrm{1}}$ | Loss factor for sheath and screen | - |
| $\lambda_{\mathrm{1c}}$ | Loss factor by circulating currents | - |
| $\lambda_{\mathrm{1cb}}$ | Loss factor for solid bonding | - |
| $\lambda_{\mathrm{1e}}$ | Loss factor by eddy currents | - |
| $\lambda_{\mathrm{1es}}$ | Loss factor for single point bonding | - |
| $\lambda_{\mathrm{2}}$ | Loss factor for armour | - |
| $\lambda_{\mathrm{3}}$ | Loss factor for steel pipes | - |
| $\lambda_{\mathrm{d}}$ | Factor for dielectric losses | - |
| $\lambda_{\mathrm{gas}}$ | Ratio c_p/c_v | - |
| $\lambda_{\mathrm{t}}$ | Relaxation parameter | - |
| $LF$ | Load factor | p.u. |
| $LF_{\mathrm{w}}$ | Weekly load factor | p.u. |
| $LF_{\mathrm{y}}$ | Yearly load factor | p.u. |
| $LME$ | London Metal Exchange | USD/mt |
| M | $m$ | Mass of cable | kg/m |
| $M$ | Cyclic rating factor | p.u. |
| $M_{\mathrm{0}}$ | Coefficient M for partial transient temp. rise | s |
| $m_{\mathrm{0}}$ | Substitution coefficient m0 for eddy-currents | Hz.m/Ω |
| $M_{\mathrm{1}}$ | Corrected cyclic rating factor | K |
| $M_{\mathrm{ab}}$ | Material of armour bedding | - |
| $M_{\mathrm{c}}$ | Material of conductor | - |
| $M_{\mathrm{cable}}$ | List of materials in a cable | |
| $M_{\mathrm{comp}}$ | Insulating gas material | - |
| $M_{\mathrm{d}}$ | Material of duct pipe | - |
| $M_{\mathrm{e}}$ | Substitution coefficient to calculate factor $F_e$ | - |
| $m_{\mathrm{EMF}}$ | Number of time steps | - |
| $M_{\mathrm{encl}}$ | Material of enclosure | - |
| $M_{\mathrm{f}}$ | Material of filler | - |
| $M_{\mathrm{gas}}$ | Gas and gas-mixtures | |
| $M_{\mathrm{i}}$ | Material of insulation | - |
| $M_{\mathrm{IEEE}}$ | Materials acc. IEEE 442 | - |
| $M_{\mathrm{j}}$ | Material of jacket | - |
| $M_{\mathrm{k}}$ | Thermal contact factor | s½ |
| $M_{\mathrm{m}}$ | Mean mutual inductance of sheath | H/m |
| $M_{\mathrm{mol}}$ | Molecular mass | mol |
| $m_{\mathrm{Nu}}$ | Factor m | - |
| $M_{\mathrm{prot}}$ | Material of protective cover | - |
| $M_{\mathrm{s}}$ | Factor Ms | - |
| $M_{\mathrm{sc}}$ | Material of screen | - |
| $M_{\mathrm{sh}}$ | Material of sheath | - |
| $M_{\mathrm{soil}}$ | Type of soils | - |
| $\mu$ | Loss factor | p.u. |
| $\mu_{\mathrm{0}}$ | Vacuum permeability | H/m |
| $\mu_{\mathrm{e}}$ | Longitudinal rel. permeability | - |
| $\mu_{\mathrm{IEC}}$ | Loss factor | p.u. |
| $\mu_{\mathrm{p}}$ | Friction coefficient | - |
| $\mu_{\mathrm{s}}$ | Rel. permeability | - |
| $\mu_{\mathrm{t}}$ | Traverse relative permeability of steel wires | - |
| $\mu_{\mathrm{w}}$ | Loss factor for weekly load variation | p.u. |
| $\mu_{\mathrm{y}}$ | Loss factor for yearly load variation | p.u. |
| N | $N_{\mathrm{0}}$ | Coefficient N for partial transient temp. rise | s² |
| $n_{\mathrm{a_{\mathrm{1}}}}$ | Number of wires of 1st armour | - |
| $n_{\mathrm{a_{\mathrm{2}}}}$ | Number of wires of 2nd armour | - |
| $N_{\mathrm{Avogrado}}$ | Avogadro constant | 1/mol |
| $N_{\mathrm{b}}$ | Number of loaded cables in backfill | - |
| $n_{\mathrm{c}}$ | Number of conductors in cable | - |
| $N_{\mathrm{c}}$ | Number of cables in system | - |
| $n_{\mathrm{cc}}$ | Number of conductors combined | - |
| $n_{\mathrm{cg}}$ | Number of conductors in GIL | - |
| $n_{\mathrm{cw}}$ | Number of wires in conductor | - |
| $N_{\mathrm{e}}$ | Substitution coefficient to calculate factor $F_e$ | - |
| $n_{\mathrm{ppc}}$ | Conductors/Cables pulled | - |
| $N_{\mathrm{sea}}$ | Number of subsea cables | - |
| $n_{\mathrm{sw}}$ | Number of screen wires | - |
| $N_{\mathrm{X}}$ | Number of intervals | - |
| $\nu$ | Summation step 1 to $N_X$ | - |
| $\nu_{\mathrm{air}}$ | Kinematic viscosity for air | m²/s |
| $\mathrm{Nu}_{\mathrm{c}}$ | Nusselt number conductor to gas | - |
| $\mathrm{Nu}_{\mathrm{encl}}$ | Nusselt number gas-enclosure | - |
| $\nu_{\mathrm{gas}}$ | Kinematic viscosity | - |
| $\mathrm{Nu}_{\mathrm{L}}$ | Nusselt number | - |
| $\mathrm{Nu}_{\mathrm{prot}}$ | Nusselt number GIL-air | - |
| $\nu_{\mathrm{soil}}$ | Soil moisture content | % |
| O | $\omega$ | Angular frequency | rad/s |
| P | $p_{\mathrm{a_{\mathrm{1}}}}$ | Length of lay of 1st armour | mm |
| $p_{\mathrm{a_{\mathrm{2}}}}$ | Length of lay of 2nd armour | mm |
| $p_{\mathrm{ab1}}$ | Factor apportioning 1st armour bedding | - |
| $p_{\mathrm{ab2}}$ | Factor apportioning 2nd armour bedding | - |
| $p_{\mathrm{cb}}$ | Minor ratio of cable section lengths | - |
| $P_{\mathrm{cc}}$ | Substitution coefficient to calculate loss factor by circulating currents | - |
| $p_{\mathrm{gas}}$ | Gas pressure | Pa |
| $p_{\mathrm{i}}$ | Factor apportioning insulation | - |
| $p_{\mathrm{j}}$ | Factor apportioning jacket/oversheath | - |
| $P_{\mathrm{L}}$ | Active power at load receptor | kVA |
| $p_{\mathrm{soil}}$ | Depth of image source | - |
| $p_{\mathrm{tr}}$ | Effective perimeter of trough | m |
| $\phi_{\mathrm{b}}$ | Parameter for trough | - |
| $\phi_{\mathrm{p}}$ | Bend section angle | rad |
| $\pi$ | Archimedes' constant π | - |
| $\mathrm{Pr}_{\mathrm{air}}$ | Prandtl number for air | - |
| $\mathrm{Pr}_{\mathrm{gas}}$ | Prandtl number for gas | - |
| Q | $q_{\mathrm{1}}$ | Ratio of losses affecting screen bedding/serving | - |
| $q_{\mathrm{2_{\mathrm{1}}}}$ | Ratio of losses affecting 1st armour bedding | - |
| $q_{\mathrm{2_{\mathrm{2}}}}$ | Ratio of losses affecting 2nd armour bedding | - |
| $q_{\mathrm{3}}$ | Ratio of losses affecting jacket | - |
| $q_{\mathrm{4}}$ | Ratio of losses affecting environment | - |
| $Q_{\mathrm{A}}$ | Element A of two-part thermal circuit | J/m.K |
| $Q_{\mathrm{a_{\mathrm{1}}}}$ | Thermal capacitance of 1st armour | J/m.K |
| $Q_{\mathrm{a_{\mathrm{2}}}}$ | Thermal capacitance of 2nd armour | J/m.K |
| $Q_{\mathrm{ab_{\mathrm{1}}}}$ | Thermal capacitance of 1st armour bedding | J/m.K |
| $Q_{\mathrm{ab_{\mathrm{2}}}}$ | Thermal capacitance of 2nd armour bedding | J/m.K |
| $Q_{\mathrm{B}}$ | Element B of two-part thermal circuit | J/m.K |
| $Q_{\mathrm{B_{\mathrm{ab1}}}}$ | Element B of two-part thermal circuit, 1st armour bedding | J/m.K |
| $Q_{\mathrm{B_{\mathrm{ab2}}}}$ | Element B of two-part thermal circuit, 2nd armour bedding | J/m.K |
| $Q_{\mathrm{B_{\mathrm{d}}}}$ | Element B of two-part thermal circuit, duct | J/m.K |
| $Q_{\mathrm{B_{\mathrm{f}}}}$ | Element B of two-part thermal circuit, filler | J/m.K |
| $Q_{\mathrm{B_{\mathrm{i}}}}$ | Element B of two-part thermal circuit, insulation | J/m.K |
| $Q_{\mathrm{B_{\mathrm{j}}}}$ | Element B of two-part thermal circuit, jacket | J/m.K |
| $Q_{\mathrm{B_{\mathrm{s}}}}$ | Element B of two-part thermal circuit, screen/sheath | J/m.K |
| $Q_{\mathrm{c}}$ | Thermal capacitance of conductor | J/m.K |
| $q_{\mathrm{cb}}$ | Major ratio of cable section lengths | - |
| $Q_{\mathrm{cc}}$ | Substitution coefficient to calculate loss factor by circulating currents | - |
| $Q_{\mathrm{d}}$ | Thermal capacitance of duct | J/m.K |
| $Q_{\mathrm{d_{\mathrm{fill}}}}$ | Thermal capacitance of duct filling | J/m.K |
| $q_{\mathrm{f}}$ | Ratio of losses affecting the filler | - |
| $Q_{\mathrm{f}}$ | Thermal capacitance of filler | J/m.K |
| $Q_{\mathrm{i}}$ | Thermal capacitance of insulation | J/m.K |
| $Q_{\mathrm{i1}}$ | Thermal capacitance of insulation, 1st portion | J/m.K |
| $Q_{\mathrm{i2}}$ | Thermal capacitance of insulation, 2nd portion | J/m.K |
| $Q_{\mathrm{j}}$ | Thermal capacitance of jacket | J/m.K |
| $Q_{\mathrm{p}}$ | Quantity of lubricant | l/m |
| $Q_{\mathrm{sc}}$ | Thermal capacitance of screen | J/m.K |
| $Q_{\mathrm{scb}}$ | Thermal capacitance of screen bedding | J/m.K |
| $Q_{\mathrm{scs}}$ | Thermal capacitance of screen serving | J/m.K |
| $Q_{\mathrm{sh}}$ | Thermal capacitance of sheath | J/m.K |
| $Q_{\mathrm{t}}$ | Total thermal capacitance, transient | J/m.K |
| $q_{\mathrm{x}}$ | Factor for characteristic diameter | - |
| R | $R$ | AC resistance of conductor | Ω/m |
| $R_{\mathrm{0}}$ | Zero sequence resistance | Ω/m |
| $R_{\mathrm{1}}$ | Resistance of conductor before emergency rating | Ω/m |
| $R_{\mathrm{A}}$ | Electrical resistance of armour | Ω/m |
| $R_{\mathrm{A_{\mathrm{1}}}}$ | Electrical resistance of 1st armour layer | Ω/m |
| $R_{\mathrm{A_{\mathrm{2}}}}$ | Electrical resistance of 2nd armour layer | Ω/m |
| $R_{\mathrm{Ao}}$ | Resistance of armour at 20°C | Ω/m |
| $r_{\mathrm{b}}$ | Equivalent radius of backfill | mm |
| $R_{\mathrm{c}}$ | DC resistance of conductor | Ω/m |
| $r_{\mathrm{c}}$ | Radius of conductor | mm |
| $R_{\mathrm{CG}}$ | Resistance multilayer backfill | K.m/W |
| $R_{\mathrm{co}}$ | DC resistance of conductor at 20°C | Ω/m |
| $R_{\mathrm{e}}$ | Resistance of sheath and armour | Ω/m |
| $R_{\mathrm{e_{\mathrm{1}}}}$ | Resistance of sheath and 1st armour | Ω/m |
| $R_{\mathrm{e_{\mathrm{2}}}}$ | Resistance of sheath and 2nd armour | Ω/m |
| $r_{\mathrm{F}}$ | Radius below the insulation | mm |
| $R_{\mathrm{gas}}$ | Specific gas constant | - |
| $R_{\mathrm{gas0}}$ | Universal molar gas constant | - |
| $r_{\mathrm{I}}$ | Radius of the insulation | mm |
| $r_{\mathrm{ij}}$ | View factor coefficient | - |
| $R_{\mathrm{max}}$ | Resistance of conductor of emergency rating | Ω/m |
| $r_{\mathrm{mbi}}$ | Minimal bending radius for installation | m |
| $r_{\mathrm{mbif}}$ | Minimal installation bending radius factor | - |
| $r_{\mathrm{mbp}}$ | Minimal bending radius during cable pulling | m |
| $r_{\mathrm{mbpf}}$ | Minimal pulling bending radius factor | - |
| $R_{\mathrm{p}}$ | Radius of bend | m |
| $R_{\mathrm{q1}}$ | Resistance 1 | K.m/W |
| $R_{\mathrm{q11}}$ | Resistance 11 | K.m/W |
| $R_{\mathrm{q12}}$ | Resistance 12 | K.m/W |
| $R_{\mathrm{q13}}$ | Resistance 13 | K.m/W |
| $R_{\mathrm{q2}}$ | Resistance 2 | K.m/W |
| $R_{\mathrm{q21}}$ | Resistance 21 | K.m/W |
| $R_{\mathrm{q22}}$ | Resistance 22 | K.m/W |
| $R_{\mathrm{q23}}$ | Resistance 23 | K.m/W |
| $R_{\mathrm{q24}}$ | Resistance 24 | K.m/W |
| $R_{\mathrm{q3}}$ | Resistance 3 | K.m/W |
| $R_{\mathrm{q31}}$ | Resistance 31 | K.m/W |
| $R_{\mathrm{q32}}$ | Resistance 32 | K.m/W |
| $R_{\mathrm{q33}}$ | Resistance 33 | K.m/W |
| $R_{\mathrm{q34}}$ | Resistance 34 | K.m/W |
| $R_{\mathrm{R}}$ | Resistance of conductor in steady-state | Ω/m |
| $R_{\mathrm{s}}$ | Electrical resistance of screen||sheath | Ω/m |
| $R_{\mathrm{sc}}$ | Electrical resistance of screen at operating temp. | Ω/m |
| $R_{\mathrm{sh}}$ | Electrical resistance of sheath | Ω/m |
| $R_{\mathrm{so}}$ | Resistance of screen and sheath at 20°C | Ω/m |
| $r_{\mathrm{\theta}}$ | Factor r for emergency load current | - |
| $r_{\mathrm{x}}$ | Radius to point x in insulation | mm |
| $\mathrm{Ra}_{\mathrm{c}}$ | Rayleigh number conductor-gas | - |
| $\mathrm{Ra}_{\mathrm{encl}}$ | Rayleigh number gas-enclosure | - |
| $\mathrm{Ra}_{\mathrm{L}}$ | Rayleigh number | - |
| $\mathrm{Ra}_{\mathrm{prot}}$ | Rayleigh number GIL-air | - |
| $\mathrm{Re}_{\mathrm{air}}$ | Reynolds number for air | - |
| $RF$ | Reduction factor | - |
| $\rho_{\mathrm{4}}$ | Thermal resistivity of soil | K.m/W |
| $\rho_{\mathrm{4d}}$ | Thermal resistivity of dry soil | K.m/W |
| $\rho_{\mathrm{ab}}$ | Thermal resistivity of armour bedding | K.m/W |
| $\rho_{\mathrm{ab_{\mathrm{2}}}}$ | Thermal resistivity of bedding between armour layers | K.m/W |
| $\rho_{\mathrm{ar}}$ | Specific electrical resistivity of armour material | Ω.m |
| $\rho_{\mathrm{b}}$ | Thermal resistivity backfill | K.m/W |
| $\rho_{\mathrm{b1}}$ | Thermal resistivity top backfill layer | K.m/W |
| $\rho_{\mathrm{b2}}$ | Thermal resistivity mid backfill layer | K.m/W |
| $\rho_{\mathrm{c}}$ | El. resistivity of conductor material | Ω.m |
| $\rho_{\mathrm{corr}}$ | Thermal resistivity of corrugation filling | K.m/W |
| $\rho_{\mathrm{cr}}$ | Thermal resistivity of conductor material | K.m/W |
| $\rho_{\mathrm{d}}$ | Thermal resistivity of duct material | K.m/W |
| $\rho_{\mathrm{f}}$ | Thermal resistivity of filler | K.m/W |
| $\rho_{\mathrm{gas}}$ | Gas density at 1.013 bar | kg/m³ |
| $\rho_{\mathrm{i}}$ | Thermal resistivity of insulation | K.m/W |
| $\rho_{\mathrm{j}}$ | Thermal resistivity of jacket | K.m/W |
| $\rho_{\mathrm{k2}}$ | Thermal resistivity of the media above | K.m/W |
| $\rho_{\mathrm{k20}}$ | Electrical resistivity of metallic component | Ω.m |
| $\rho_{\mathrm{k3}}$ | Thermal resistivity of the media below | K.m/W |
| $\rho_{\mathrm{ki}}$ | Thermal resistivity of adjacent material | K.m/W |
| $\rho_{\mathrm{m}}$ | Thermal resistivity of the screen | K.m/W |
| $\rho_{\mathrm{sc}}$ | Specific electrical resistivity of screen material | Ω.m |
| $\rho_{\mathrm{sh}}$ | Specific electrical resistivity of sheath material | Ω.m |
| $\rho_{\mathrm{soil}}$ | Electrical resistivity of soil | Ω |
| $\rho_{\mathrm{t}}$ | Thermal resistivity of concrete wall | K.m/W |
| S | $s_{\mathrm{1}}$ | Thickness of the upper backfilling layer | m; |
| $s_{\mathrm{2}}$ | Thickness of the lower backfilling layer | m² |
| $s_{\mathrm{3}}$ | Thickness of the cable bedding | m² |
| $s_{\mathrm{4}}$ | Thickness of the cable bedding | m² |
| $s_{\mathrm{air}}$ | Axial spacing between cables | m |
| $s_{\mathrm{c}}$ | Separation of conductors in a system | mm |
| $s_{\mathrm{c2}}$ | Separation of cables | mm |
| $S_{\mathrm{G}}$ | Apparent power at injecting point | kW |
| $S_{\mathrm{gas}}$ | Sutherland's constant | K |
| $s_{\mathrm{ij}}$ | Spacing between cable i and j | - |
| $S_{\mathrm{k}}$ | Area of current carrying component | mm² |
| $s_{\mathrm{roll}}$ | Roller distance | m |
| $s_{\mathrm{S1}}$ | Variation of spacing in 1st cable section | p.u. |
| $s_{\mathrm{S2}}$ | Variation of spacing in 2nd cable section | p.u. |
| $s_{\mathrm{S3}}$ | Variation of spacing in 3rd cable section | p.u. |
| $s_{\mathrm{T}}$ | Distance to closer side of backfill | m |
| $s_{\mathrm{x}}$ | Separation of conductors in a cable | mm |
| $SI$ | Surge Impedance | Ω |
| $\sigma$ | Stefan Boltzmann constant | W/m²K4 |
| $\sigma_{\mathrm{ab}}$ | Specific heat capacity of armour bedding | J/K.m³ |
| $\sigma_{\mathrm{ar}}$ | Specific heat capacity of armour material | J/K.m³ |
| $\sigma_{\mathrm{c}}$ | Specific heat capacity of conductor material | J/K.m³ |
| $\sigma_{\mathrm{d}}$ | Specific heat capacity of duct material | J/K.m³ |
| $\sigma_{\mathrm{d_{\mathrm{fill}}}}$ | Specific heat capacity of duct filling | J/K.m³ |
| $\sigma_{\mathrm{f}}$ | Specific heat capacity of filler | J/K.m³ |
| $\sigma_{\mathrm{i}}$ | Specific heat capacity of insulation material | J/K.m³ |
| $\sigma_{\mathrm{j}}$ | Specific heat capacity of jacket material | J/K.m³ |
| $\sigma_{\mathrm{k2}}$ | Specific heat of media below | J/K.m³ |
| $\sigma_{\mathrm{k3}}$ | Specific heat of media above | J/K.m³ |
| $\sigma_{\mathrm{kc}}$ | Specific heat of metallic component | J/K.m³ |
| $\sigma_{\mathrm{ki}}$ | Specific heat of adjacent material | J/K.m³ |
| $\sigma_{\mathrm{sc}}$ | Specific heat capacity of screen material | J/K.m³ |
| $\sigma_{\mathrm{scb}}$ | Specific heat capacity of screen bedding | J/K.m³ |
| $\sigma_{\mathrm{scs}}$ | Specific heat capacity of screen serving | J/K.m³ |
| $\sigma_{\mathrm{sh}}$ | Specific heat capacity of sheath material | J/K.m³ |
| $\sigma_{\mathrm{sun}}$ | Absorption coefficient of solar radiation | - |
| $\sigma_{\mathrm{y}}$ | Yield strength of metals for armour | MPa |
| $SP_{\mathrm{p}}$ | Sidewall pressure | N/m |
| T | $t$ | Insulation thickness between conductors | mm |
| $t_{\mathrm{1}}$ | Thickness of insulation to sheath | mm |
| $T_{\mathrm{1}}$ | Thermal resistance between one conductor and sheath | K.m/W |
| $T_{\mathrm{1t}}$ | Thermal resistance between one conductor and sheath, transient | K.m/W |
| $t_{\mathrm{1t}}$ | Thickness of insulation to sheath, transient | mm |
| $t_{\mathrm{2}}$ | Thickness of bedding under armour | mm |
| $T_{\mathrm{2}}$ | Thermal resistance between sheath and armour | K.m/W |
| $T_{\mathrm{2_{\mathrm{1}}}}$ | Thermal resistance between sheath and 1st armour layer | K.m/W |
| $T_{\mathrm{2_{\mathrm{2}}}}$ | Thermal resistance of separation between armour layers | K.m/W |
| $T_{\mathrm{2_{\mathrm{f}}}}$ | Thermal resistance between sheath and armour bedding | K.m/W |
| $t_{\mathrm{3}}$ | Thickness of serving over armour | mm |
| $T_{\mathrm{3}}$ | Thermal resistance of jacket | K.m/W |
| $T_{\mathrm{4}}$ | Thermal resistance isolated cable/duct | K.m/W |
| $T_{\mathrm{4d}}$ | Transient thermal resistance for daily load | K.m/W |
| $T_{\mathrm{4db}}$ | Correction for backfill | K.m/W |
| $T_{\mathrm{4et}}$ | Transient thermal resistance | K.m/W |
| $T_{\mathrm{4i}}$ | Thermal resistance of medium in the duct | K.m/W |
| $T_{\mathrm{4ii}}$ | Thermal resistance of the duct wall | K.m/W |
| $T_{\mathrm{4iii}}$ | Thermal resistance to ambient of cable/duct | K.m/W |
| $T_{\mathrm{4\mu}}$ | Thermal resistance to ambient | K.m/W |
| $T_{\mathrm{4ss}}$ | Steady-state thermal resistance | K.m/W |
| $T_{\mathrm{4t}}$ | Equivalent thermal resistance for tunnel | K.m/W |
| $T_{\mathrm{4w}}$ | Transient thermal resistance for weekly load | K.m/W |
| $T_{\mathrm{4y}}$ | Transient thermal resistance for yearly load | K.m/W |
| $T_{\mathrm{a}}$ | Star thermal resistance of air | K.m/W |
| $T_{\mathrm{A}}$ | Element A of equivalent thermal circuit | K.m/W |
| $T_{\mathrm{a0}}$ | Apparent thermal resistance a | 1/s |
| $t_{\mathrm{ab_{\mathrm{1}}}}$ | Thickness of 1st armour bedding | mm |
| $t_{\mathrm{ab_{\mathrm{2}}}}$ | Thickness of 2nd bedding between | mm |
| $T_{\mathrm{at}}$ | Convection thermal resistance air-tunnel | K.m/W |
| $T_{\mathrm{B}}$ | Element B of equivalent thermal circuit | K.m/W |
| $T_{\mathrm{b0}}$ | Apparent thermal resistance b | s² |
| $T_{\mathrm{C}}$ | Element C of equivalent thermal circuit | K.m/W |
| $t_{\mathrm{c}}$ | Thickness of hollow conductor | mm |
| $t_{\mathrm{comp}}$ | Thickness of compartment | m |
| $t_{\mathrm{corr}}$ | Thickness of corrugation filling | mm |
| $t_{\mathrm{cs}}$ | Thickness of conductor shield | mm |
| $t_{\mathrm{ct}}$ | Conductor tape thickness | mm |
| $T_{\mathrm{d}}$ | Internal thermal resistance for dielectric losses | K.m/W |
| $T_{\mathrm{e}}$ | External thermal resistance of tunnel | K.m/W |
| $t_{\mathrm{EMF}}$ | Time step to calculate current source | s |
| $t_{\mathrm{encl}}$ | Thickness of enclosure | mm |
| $T_{\mathrm{eq}}$ | Equivalent thermal resistance | K.m/W |
| $T_{\mathrm{f}}$ | Axial thermal resistance due to the movement of air through the tunnel | K.m/W |
| $t_{\mathrm{f}}$ | Thickness of filler/belt insulation | mm |
| $T_{\mathrm{gas}}$ | Gas temperature | K |
| $T_{\mathrm{gas0}}$ | Gas reference temperature | K |
| $T_{\mathrm{i}}$ | Internal thermal resistance for current losses | K.m/W |
| $t_{\mathrm{i}}$ | Thickness of core insulation | mm |
| $T_{\mathrm{\infty}}$ | Infinite bulk temperature (the ambient air temperature) | K |
| $t_{\mathrm{ins}}$ | Thickness of insulation | mm |
| $t_{\mathrm{is}}$ | Thickness of insulation screen | mm |
| $t_{\mathrm{j}}$ | Thickness of jacket | mm |
| $t_{\mathrm{jj}}$ | Thickness of additional layer over jacket | mm |
| $t_{\mathrm{k}}$ | Duration of short-circuit | s |
| $T_{\mathrm{L}}$ | Thermal longitudinal resistance | K.m/W |
| $T_{\mathrm{mh}}$ | Mutual thermal resistance cable - heat source | K.m/W |
| $T_{\mathrm{mh_{\mathrm{v}}}}$ | Mutual thermal resistance cable - heat source | K.m/W |
| $T_{\mathrm{o}}$ | Thermal resistance of the oil in the pipe | K.m/W |
| $t_{\mathrm{prot}}$ | Thickness of protective cover | mm |
| $T_{\mathrm{r}}$ | Total thermal resistance | K.m/W |
| $T_{\mathrm{s}}$ | Star thermal resistance of cable | K.m/W |
| $T_{\mathrm{sa}}$ | Convection thermal resistance surface-air | K.m/W |
| $t_{\mathrm{sc}}$ | Thickness of the screen | mm |
| $t_{\mathrm{scb}}$ | Thickness of screen bedding | mm |
| $t_{\mathrm{scs}}$ | Thickness of screen serving | mm |
| $t_{\mathrm{sh}}$ | Thickness of the sheath | mm |
| $T_{\mathrm{st}}$ | Radiation thermal resistance surface-tunnel | K.m/W |
| $T_{\mathrm{surf}}$ | Surface temperature | K |
| $T_{\mathrm{t}}$ | Star thermal resistance of tunnel | K.m/W |
| $t_{\mathrm{t}}$ | Thickness of the tunnel wall | m |
| $T_{\mathrm{tot}}$ | Total thermal resistance, transient | K.m/W |
| $T_{\mathrm{tr}}$ | Thermal resistance of trough | K |
| $T_{\mathrm{tw}}$ | Thermal resistance of the tunnel wall | K.m/W |
| $\mathrm{tan}\delta _{\mathrm{i}}$ | Loss factor of insulation | - |
| $\tau$ | Transient period | s |
| $\theta_{\mathrm{2K}}$ | Temperature rise for 2K criterion | °C |
| $\theta_{\mathrm{a}}$ | Ambient temperature | °C |
| $\theta_{\mathrm{abs}}$ | Absolute temperature | K |
| $\theta_{\mathrm{air}}$ | Ambient air temperature | °C |
| $\theta_{\mathrm{ar}}$ | Temperature of armour | °C |
| $\theta_{\mathrm{ar_{\mathrm{1}}}}$ | Temperature of 1st armour layer | °C |
| $\theta_{\mathrm{ar_{\mathrm{2}}}}$ | Temperature of 2nd armour layer | °C |
| $\theta_{\mathrm{at}}$ | Air temperature | °C |
| $\theta_{\mathrm{at_{\mathrm{0}}}}$ | Air temperature in tunnel at inlet | °C |
| $\theta_{\mathrm{at_{\mathrm{L}}}}$ | Air temperature in tunnel at outlet | °C |
| $\theta_{\mathrm{at_{\mathrm{z}}}}$ | Air temperature in tunnel at z | °C |
| $\theta_{\mathrm{c}}$ | Temperature of conductor | °C |
| $\theta_{\mathrm{c_{\mathrm{t}}}}$ | Temperature of conductor after transient | °C |
| $\theta_{\mathrm{c_{\mathrm{z}}}}$ | Conductor temperature at z | °C |
| $\theta_{\mathrm{cmax}}$ | Max. conductor temperature | °C |
| $\theta_{\mathrm{cmaxeo}}$ | Max. emergency overload temperature | °C |
| $\theta_{\mathrm{cmaxsc}}$ | Max. short-circuit temperature | °C |
| $\theta_{\mathrm{de}}$ | External temperature of duct | °C |
| $\theta_{\mathrm{di}}$ | Internal temperature of duct | °C |
| $\theta_{\mathrm{e}}$ | External temperature | °C |
| $\theta_{\mathrm{f}}$ | Temperature of filler for multi-core cables type SS with sheath | °C |
| $\theta_{\mathrm{gas}}$ | Surface temperature | °C |
| $\theta_{\mathrm{hs}}$ | Temperature of heat source | °C |
| $\theta_{\mathrm{kf}}$ | Final temperature | °C |
| $\theta_{\mathrm{ki}}$ | Initial temperature | °C |
| $\theta_{\mathrm{kmax}}$ | Max. temperature of non-insulation material | °C |
| $\theta_{\mathrm{m}}$ | Mean temperature of the medium in the duct | °C |
| $\theta_{\mathrm{max}}$ | Temperature of conductor at end of emergency loading | °C |
| $\theta_{\mathrm{o_{\mathrm{L}}}}$ | Temperature of cable surface at outlet | °C |
| $\theta_{\mathrm{o_{\mathrm{z}}}}$ | Temperature of cable surface at z | °C |
| $\theta_{\mathrm{p}}$ | Section angle from horizontal | rad |
| $\theta_{\mathrm{R}}$ | Rated current transient to steady-state ratio | - |
| $\theta_{\mathrm{s}}$ | Temperature of screen/sheath | °C |
| $\theta_{\mathrm{sc}}$ | Temperature of screen | °C |
| $\theta_{\mathrm{sh}}$ | Temperature of sheath | °C |
| $\theta_{\mathrm{surf}}$ | Surface temperature | °C |
| $\theta_{\mathrm{t}}$ | Temperature of inner tunnel wall | °C |
| $\theta_{\mathrm{t_{\mathrm{L}}}}$ | Temperature of tunnel wall at outlet | °C |
| $\theta_{\mathrm{t_{\mathrm{z}}}}$ | Temperature of tunnel wall at z | °C |
| $\theta_{\mathrm{to}}$ | Temperature of outer tunnel wall | °C |
| $\theta_{\mathrm{to_{\mathrm{z}}}}$ | Temperature of outer tunnel wall at z | °C |
| $\theta_{\mathrm{x}}$ | Critical soil temperature | °C |
| $TQ$ | Cable thermal time constant | s |
| U | $u$ | Substitution coefficient | - |
| $U_{\mathrm{0}}$ | Value of U0 for determination of test voltages | kV |
| $U_{\mathrm{d}}$ | Constant U for duct installations | K.m/W |
| $U_{\mathrm{e}}$ | Phase-to-ground voltage | kV |
| $U_{\mathrm{m}}$ | Highest voltage for equipment | kV |
| $U_{\mathrm{n}}$ | Cable rated voltage | kV |
| $U_{\mathrm{o}}$ | Operating voltage | kV |
| V | $v_{\mathrm{4}}$ | Ratio of the thermal resistivities of dry and moist soils | - |
| $V_{\mathrm{air}}$ | Air velocity | m/s |
| $V_{\mathrm{d}}$ | Constant V for duct installations | K.m/W |
| $V_{\mathrm{drop}}$ | Voltage drop | V/A/km |
| W | $W_{\mathrm{A}}$ | Armour losses | W/m |
| $W_{\mathrm{a_{\mathrm{L}}}}$ | Heat removed by air at outlet | W/m |
| $W_{\mathrm{a_{\mathrm{z}}}}$ | Heat removed by air at z | W/m |
| $w_{\mathrm{b}}$ | Width of the backfill area | mm |
| $W_{\mathrm{c}}$ | Conductor losses | W/m |
| $W_{\mathrm{conv}}$ | Convection heat transfer | W/m |
| $W_{\mathrm{d}}$ | Dielectric losses | W/m |
| $w_{\mathrm{f_{\mathrm{1}}}}$ | Width of flat wires of 1st armour | mm |
| $w_{\mathrm{f_{\mathrm{2}}}}$ | Width of flat wires of 2nd armour | mm |
| $W_{\mathrm{h}}$ | Heat generated by external heat source / cable | W/m |
| $W_{\mathrm{hs}}$ | Heat dissipation of heat source | W/m |
| $W_{\mathrm{I}}$ | Ohmic losses per phase | W/m |
| $w_{\mathrm{p}}$ | Weight correction factor | - |
| $W_{\mathrm{p}}$ | Losses in ferromagnetic steel pipe | W/m |
| $W_{\mathrm{rad}}$ | Radiation heat transfer | W/m |
| $W_{\mathrm{s}}$ | Screen and sheath losses | W/m |
| $W_{\mathrm{sA}}$ | Total loss in sheath and armour | W/m |
| $W_{\mathrm{sA_{\mathrm{1}}}}$ | Total loss in sheath and 1st armour | W/m |
| $W_{\mathrm{sA_{\mathrm{2}}}}$ | Total loss in sheath and 2nd armour | W/m |
| $w_{\mathrm{sc}}$ | Width of flat screen wire | mm |
| $W_{\mathrm{sh}}$ | Sheath losses | W/m |
| $W_{\mathrm{sum}}$ | Sum of total losses of all systems | W/m |
| $W_{\mathrm{sys}}$ | Total losses of system | W/m |
| $W_{\mathrm{t}}$ | Total losses per phase | W/m |
| $W_{\mathrm{T}}$ | Trench width | m |
| $w_{\mathrm{t}}$ | Inner width | m |
| $W_{\mathrm{tot}}$ | Total losses per object | W/m |
| X | $x$ | Horizontal cartesian coordinate | m |
| $X_{\mathrm{0}}$ | Zero sequence reactance | Ω/m |
| $x_{\mathrm{b}}$ | Horizontal center position of backfill | mm |
| $X_{\mathrm{c}}$ | Reactance of conductor | Ω/m |
| $X_{\mathrm{G}}$ | Factor XG | - |
| $X_{\mathrm{G2}}$ | Factor X_G2 | - |
| $X_{\mathrm{K}}$ | Factor XK | - |
| $X_{\mathrm{m}}$ | Mutual reactance | Ω/m |
| $x_{\mathrm{p}}$ | Factor of proximity effect on conductor | - |
| $x_{\mathrm{s}}$ | Factor of skin effect on conductor | - |
| $X_{\mathrm{s}}$ | Reactance of screen/sheath | Ω/m |
| $X_{\mathrm{S1}}$ | Reactance section 1 | Ω/m |
| $X_{\mathrm{S2}}$ | Reactance section 2 | Ω/m |
| $X_{\mathrm{S3}}$ | Reactance section 3 | Ω/m |
| Y | $Y$ | Admittance | S/m |
| $y$ | Vertical cartesian coordinate | m |
| $y_{\mathrm{2K}}$ | Depth for 2K criterion | mm |
| $Y_{\mathrm{d}}$ | Constant Y for duct installations | K.m/W |
| $Y_{\mathrm{G}}$ | Factor YG | - |
| $Y_{\mathrm{K}}$ | Factor YK | - |
| $y_{\mathrm{p}}$ | Proximity effect factor of conductors | - |
| $y_{\mathrm{s}}$ | Skin effect factor of conductor | - |
| Z | $Z_{\mathrm{0}}$ | Zero sequence impedance | Ω/m |
| $Z_{\mathrm{bs}}$ | Installation constant Z | - |
| $z_{\mathrm{h}}$ | Location of the heat source | m |
| $Z_{\mathrm{K}}$ | Factor ZK | - |
| $z_{\mathrm{max}}$ | Logitudinal thermal distance | m |
| $Z_{\mathrm{neg}}$ | Negative sequence impedance | Ω/m |
| $Z_{\mathrm{pos}}$ | Positive sequence impedance | Ω/m |
| $z_{\mathrm{r}}$ | Location of the hottest point | m |
| $\zeta_{\mathrm{M}}$ | Density of material | g/cm³ |
