| A | $a_0$ | Coefficient a partial transient temperature rise | 1/s |
| $a_{12}$ | Distance phase 1 — phase 2 | mm |
| $a_{1t}$ | Distance phase 1 — earth continuity conductor | mm |
| $a_{23}$ | Distance phase 2 — phase 3 | mm |
| $a_{2t}$ | Distance phase 2 — earth continuity conductor | mm |
| $a_{31}$ | Distance phase 3 — phase 1 | mm |
| $a_{3t}$ | Distance phase 3 — earth continuity conductor | mm |
| $A_{ab}$ | Cross-sectional area armour bedding | mm$^2$ |
| $A_{ar}$ | Cross-sectional area armour | mm$^2$ |
| $A_c$ | Cross-sectional area conductor | mm$^2$ |
| $a_c$ | Skin and proximity effect coefficient a PAC/GIL conductor | |
| $A_{comp}$ | Cross-sectional area compartment | m$^2$ |
| $A_d$ | Cross-sectional area duct wall | mm$^2$ |
| $A_{d,fill}$ | Free cross-sectional area inside duct | mm$^2$ |
| $A_{di}$ | Duct surface (inner) | m$^2$ |
| $A_{do}$ | Duct surface (outer) | m$^2$ |
| $A_e$ | Surface of object | m$^2$ |
| $A_{encl}$ | Cross-sectional area enclosure | mm$^2$ |
| $a_{encl}$ | Skin and proximity effect coefficient a PAC/GIL enclosure | |
| $A_{er}$ | Surface of object | m$^2$ |
| $A_f$ | Cross-sectional area filler | mm$^2$ |
| $A_{hsf}$ | Cross-sectional area fluid | mm$^2$ |
| $A_{hsi}$ | Cross-sectional area pipe insulation | mm$^2$ |
| $A_{hsj}$ | Cross-sectional area protective jacket | mm$^2$ |
| $A_{hsp}$ | Cross-sectional area fluid-filled pipe | mm$^2$ |
| $A_i$ | Cross-sectional area insulation | mm$^2$ |
| $a_i$ | Parameter a for radial derivative of dielectric losses | |
| $A_{it}$ | Cross-sectional area insulation (IEC 60853) | mm$^2$ |
| $A_j$ | Cross-sectional area jacket | mm$^2$ |
| $A_k$ | Thermal property constant A | mm/s$^{1/2}$ |
| $a_m$ | Mean distance between the phases | mm |
| $A_{prot}$ | Cross-sectional area protective cover | mm$^2$ |
| $a_{S1}$ | Length minor section 1 | p.u. |
| $a_{S2}$ | Length minor section 2 | p.u. |
| $a_{S3}$ | Length minor section 3 | p.u. |
| $A_{sc}$ | Cross-sectional area screen | mm$^2$ |
| $A_{scb}$ | Cross-sectional area screen bedding | mm$^2$ |
| $A_{scs}$ | Cross-sectional area screen serving | mm$^2$ |
| $A_{sh}$ | Cross-sectional area sheath | mm$^2$ |
| $A_{shj}$ | Cross-sectional area sheath jacket | mm$^2$ |
| $a_{shj}$ | Factor $a_{shj}$ for jacket around each core | |
| $A_{skid}$ | Cross-sectional area skid wires | mm$^2$ |
| $A_{sp}$ | Cross-sectional area steel pipe | mm$^2$ |
| $A_t$ | Cross-sectional area (inner) tunnel | m$^2$ |
| $A_{tape}$ | Cross-sectional area tapes | mm$^2$ |
| $a_{type}$ | Construction of armour | |
| $\alpha_0$ | Constant α burial depth | |
| $\alpha_{ar}$ | Temperature coefficient armour material | 1/K |
| $\alpha_{at}$ | Heat transfer coefficient to channel wall | W/(K.m$^2$) |
| $\alpha_c$ | Temperature coefficient conductor material | 1/K |
| $\alpha_{encl}$ | Temperature coefficient enclosure material | 1/K |
| $\alpha_f$ | Phase shift | ° |
| $\alpha_{gas}$ | Thermal diffusivity gas | m$^2$/s |
| $\alpha_i$ | Temperature coefficient of conductivity insulation material | 1/K |
| $\alpha_p$ | Factor $\alpha_p$ | |
| $\alpha_{sa}$ | Heat transfer coefficient convection | W/(K.m$^2$) |
| $\alpha_{sc}$ | Temperature coefficient screen material | 1/K |
| $\alpha_{sh}$ | Temperature coefficient sheath material | 1/K |
| $\alpha_{skid}$ | Temperature coefficient skid wire material | 1/K |
| $\alpha_{sp}$ | Temperature coefficient steel pipe material | 1/K |
| $\alpha_{st}$ | Heat transfer coefficient radiation | W/(K.m$^2$) |
| $\alpha_{sys}$ | Inclination angle | ° |
| $\alpha_t$ | Conductor to surface attainment factor | |
| B | $B$ | Susceptance | S/m |
| $b_0$ | Coefficient b partial transient temperature rise | 1/s |
| $B_1$ | Loss coefficient $B_1$ armour | $\Omega$/m |
| $B_2$ | Loss coefficient $B_2$ armour | $\Omega$/m |
| $b_c$ | Skin and proximity effect coefficient b PAC/GIL conductor | |
| $B_{EMF}$ | Magnetic field strength | $\mu$T |
| $b_{encl}$ | Skin and proximity effect coefficient b PAC/GIL enclosure | |
| $B_k$ | Thermal property constant B | mm$^2$/s |
| $b_{shj}$ | Factor $b_{shj}$ for jacket around each core | |
| $b_x$ | Shorter side backfill | mm |
| $b_y$ | Longer side backfill | mm |
| $\beta_0$ | Constant $\beta_0$ (Ovuworie) | |
| $\beta_1$ | Substitution coefficient $\beta_1$ for eddy-currents | |
| $\beta_6$ | Factor $|1-\beta(6)|$ | |
| $\beta_{ar}$ | Reciprocal of temperature coefficient armour material | K |
| $\beta_b$ | Angle of exposed wetted surface of pipe | rad |
| $\beta_c$ | Reciprocal of temperature coefficient conductor material | K |
| $\beta_{encl}$ | Reciprocal of temperature coefficient enclosure material | K |
| $\beta_{gas}$ | Volumetric thermal expansion coefficient gas | 1/K |
| $\beta_k$ | Reciprocal of temperature coefficient metallic component | K |
| $\beta_p$ | Factor $\beta_p$ | |
| $\beta_{sc}$ | Reciprocal of temperature coefficient screen material | K |
| $\beta_{sh}$ | Reciprocal of temperature coefficient sheath material | K |
| $\beta_{skid}$ | Reciprocal of temperature coefficient skid wire material | K |
| $\beta_{sp}$ | Reciprocal of temperature coefficient steel pipe material | K |
| $\beta_t$ | Attainment factor cable surface—ambient | |
| $\beta_X$ | Crossing angle [rad] | rad |
| $\beta_{xing}$ | Crossing angle [°] | ° |
| $\mathrm{Bi}_g$ | Biot number ground | |
| $\mathrm{Bi}_p$ | Biot number pipe | |
| C | $C_{ag}$ | Capacitance armour - ground | F/m |
| $C_{av}$ | Heat capacity of the air flow | W/K |
| $C_b$ | Capacitance insulation | F/m |
| $C_{bq}$ | Constants $C_1$ - $C_7$ multi-layer backfill | |
| $c_c$ | Distance axis of conductor—cable center | mm |
| $C_{c1}$ | Thermal capacitance part 1 | J/(m.K) |
| $C_{c2}$ | Thermal capacitance part 2 | J/(m.K) |
| $C_{c3}$ | Thermal capacitance part 3 | J/(m.K) |
| $C_{c4}$ | Thermal capacitance part 4 | J/(m.K) |
| $c_{color}$ | Wiring color code | |
| $C_{cs}$ | Capacitance conductor - shield | F/m |
| $C_E$ | Capacitance to earth | F/m |
| $C_{g1}$ | Factor C1 pipe | |
| $C_{g2}$ | Factor C2 pipe | |
| $C_{g3}$ | Factor C3 pipe | |
| $c_{gas}$ | Constant c gas (PAC/GIL) | |
| $c_{ij}$ | Coefficient c view factor | |
| $C_{k1}$ | Non-adiabatic constant $C_1$ | mm/m |
| $C_{k2}$ | Non-adiabatic constant $C_2$ | K.m.mm$^2$/J |
| $C_{Mie}$ | Factor $C$ (Mie1905) | |
| $C_{Nu,L}$ | Factor C | |
| $c_{Nu,r}$ | Factor c | |
| $C_{Nu,w}$ | Factor C | |
| $c_{p,gas}$ | Specific heat capacity gas, constant pressure | J/(kg.K) |
| $c_{p,soil}$ | Volumetric heat capacity soil material | J/(kg.K) |
| $c_{p,w}$ | Specific heat capacity water, constant pressure | J/(kg.K) |
| $C_{sa}$ | Capacitance shield - armour | F/m |
| $C_{sg}$ | Capacitance shield - ground | F/m |
| $c_{shj}$ | Factor $c_{shj}$ for jacket around each core | |
| $c_{type}$ | Construction conductor | |
| $c_{v,gas}$ | Specific heat capacity gas, constant volume | J/(kg.K) |
| $C_{v,soil}$ | Heat capacity of a unit volume of soil | J/(K.m$^3$) |
| $c_{v,w}$ | Specific heat capacity water, constant volume | J/(kg.K) |
| $C_{vair}$ | Volumetric heat capacity air | J/(K.m$^3$) |
| $CC_{pull}$ | Conduit clearance | mm |
| $CF_{pull}$ | Conduit fill | $\%$ |
| $CJ_{pull}$ | Conduit jamming ratio | |
| $\mathrm{cos}\varphi$ | Power factor | |
| $CR_{pull}$ | Conduit ratio | |
| $cuw_{sc}$ | Standard copper wire size | |
| D | $d$ | Geometric mean shield diameter | m |
| $D_{ab}$ | Diameter over armour bedding | mm |
| $D_{ar}$ | Diameter over armour | mm |
| $d_{ar}$ | Mean diameter armour | mm |
| $D_b$ | Diameter backfill | mm |
| $d_{b3}$ | Distance c multi-layer backfill | m |
| $d_{b4}$ | Distance d multi-layer backfill | m |
| $d_c$ | External diameter conductor | mm |
| $D_c$ | Diameter conductor (outer) | m |
| $d_{ci}$ | Internal diameter conductor | mm |
| $D_{ci}$ | Diameter conductor (inner) | m |
| $D_{comp}$ | Diameter compartment | m |
| $D_{core}$ | Diameter over core cable | mm |
| $D_{cs}$ | Diameter over conductor shield | mm |
| $d_{ct}$ | External diameter conductor, transient | mm |
| $d_{cw}$ | Diameter of wires conductor (average) | mm |
| $D_{di}$ | Inner diameter duct | m |
| $D_{do}$ | Outer diameter duct | m |
| $D_{dry}$ | Characteristic diameter drying zone | m |
| $D_e$ | External diameter object | mm |
| $d_e$ | Equivalent diameter of screen/sheath and armour | mm |
| $D_E$ | Equivalent depth of earth return path | m |
| $d_{ecc}$ | Diameter earth continuity conductor | mm |
| $D_{encl}$ | Diameter enclosure (outer) | m |
| $D_{eq}$ | Equivalent diameter of a group of round objects | mm |
| $D_{ext}$ | Diameter external | m |
| $D_f$ | Diameter over filler | mm |
| $d_f$ | Spacing from hottest object in group | m |
| $D_{hsi}$ | Diameter over pipe insulation | mm |
| $D_{hsj}$ | Diameter over protective jacket | mm |
| $D_i$ | Diameter over insulation incl. insulation screen | mm |
| $d_{im}$ | Non-isothermal earth surface imaginary layer of soil | m |
| $D_{in}$ | Diameter pipe (inner) | m |
| $D_{ins}$ | Diameter over insulation | mm |
| $D_{is}$ | Diameter over insulation screen | mm |
| $D_{it}$ | Diameter over insulation, transient | mm |
| $D_j$ | Diameter over jacket | mm |
| $D_{lay,3c}$ | Diameter of mechanical neutral line | mm |
| $D_o$ | Outer diameter | m |
| $d_{pk1}$ | Distance to mirrored object | mm |
| $d_{pk2}$ | Distance to buried objects | mm |
| $D_{prot}$ | Diameter protective cover | m |
| $d_{psc}$ | Point source correction | m |
| $D_{ref}$ | Diameter OHTC reference | m |
| $d_s$ | Equivalent diameter of screen and sheath | mm |
| $D_{sc}$ | Diameter over screen | mm |
| $d_{sc}$ | Mean diameter screen | mm |
| $D_{scb}$ | Diameter over screen bedding | mm |
| $D_{scs}$ | Diameter over screen serving | mm |
| $D_{sh}$ | Diameter over sheath | mm |
| $d_{sh}$ | Mean diameter sheath | mm |
| $D_{shb}$ | Diameter below sheath | mm |
| $D_{shj}$ | Diameter over sheath jacket | mm |
| $D_{soil}$ | Diameter soil layer | m |
| $d_{sw}$ | Diameter skywire | mm |
| $d_t$ | Channel covering | m |
| $d_w$ | Depth under water | m |
| $D_{wall}$ | Diameter pipe wall | m |
| $d_x$ | Equivalent diameter conductor | mm |
| $D_x$ | Characteristic diameter daily load | mm |
| $D_{x,w}$ | Characteristic diameter weekly load | mm |
| $D_{x,y}$ | Characteristic diameter yearly load | mm |
| $\Delta_1$ | Substitution coefficient $\Delta_1$ for eddy-currents | |
| $\delta_1$ | Thickness screening layer | mm |
| $\Delta_2$ | Substitution coefficient $\Delta_2$ for eddy-currents | |
| $\delta_{ar}$ | Equivalent thickness of armour | mm |
| $\delta_d$ | Distance cable—duct | m |
| $\delta_i$ | Electrical thickness of insulation material | m |
| $\delta_k$ | Thickness metallic component | mm |
| $\delta_{soil}$ | Thermal diffusivity soil | m$^2$/s |
| $\Delta d_{sh}$ | Depth of corrugation | mm |
| $\Delta H_c$ | Heat of combustion coefficient | MJ/kg |
| $\Delta t$ | Length of time step | s |
| $\Delta \theta_{0t}$ | Air temperature increase | K |
| $\Delta \theta_{0x}$ | Temperature rise by crossing heat sources | K |
| $\Delta \theta_{0x,h}$ | Temperature rise of the conductor by source h | K |
| $\Delta \theta_{air}$ | Temperature increase air | K |
| $\Delta \theta_c$ | Temperature rise conductor | K |
| $\delta \theta_c$ | Ohmic steady-state temperature rise | K |
| $\Delta \theta_{c,t}$ | Transient temperature rise conductor | K |
| $\Delta \theta_{c,t,corr}$ | Corrected transient temperature rise conductor | K |
| $\Delta \theta_{c,t,\infty}$ | Steady-state temperature rise conductor | K |
| $\Delta \theta_{c,t,o}$ | Transient temperature rise conductor by ohmic losses | K |
| $\Delta \theta_{ce}$ | Temperature difference conductor—surface | K |
| $\Delta \theta_d$ | Temperature rise dielectric losses | K |
| $\Delta \theta_{d,t}$ | Transient temperature rise by dielectric losses | K |
| $\Delta \theta_{duct}$ | Temperature rise duct (magnetic) | K |
| $\Delta \theta_{e,t}$ | Transient temperature rise outer surface | K |
| $\Delta \theta_{gas}$ | Temperature difference conductor—enclosure | °C |
| $\Delta \theta_i$ | Temperature difference insulation | K |
| $\Delta \theta_{i,max}$ | Limitation of temperature rise insulation material | K |
| $\Delta \theta_{kp}$ | Temperature rise by object k | K |
| $\Delta \theta_{kp,t}$ | Transient temperature rise outer surface by object k | K |
| $\Delta \theta_{max}$ | Maximum permissible conductor temperature rise | K |
| $\Delta \theta_p$ | Temperature rise by other buried objects | K |
| $\Delta \theta_{p,t}$ | Transient temperature rise outer surface by other buried objects | K |
| $\Delta \theta_R$ | Conductor temperature rise above ambient temperature | K |
| $\Delta \theta_{R,\infty}$ | Maximum permissible conductor temperature rise | °C |
| $\Delta \theta_s$ | Temperature difference surface—ambient | K |
| $\delta \theta_{SPK}$ | Peak cyclic temperature rise | K |
| $\Delta \theta_{sun}$ | Temperature difference conductor—enclosure | K |
| $\Delta \theta_{uh}$ | Temperature rise by crossing heat sources z | K |
| $\Delta \theta_x$ | Critical soil temperature rise | K |
| $\Delta \theta_{x0}$ | Critical soil temperature rise (VDE) | K |
| $\Delta W$ | Incremental heat generated | W |
| $\Delta w_d$ | Increment of volumetric density of dielectric losses in HVDC cables | W/m$^3$ |
| $\Delta z$ | Length of the interval | m |
| $Di_d$ | Inner diameter duct | mm |
| $Di_{hsp}$ | Inner diameter fluid-filled pipe | mm |
| $Di_p$ | Inner diameter enclosing pipe | m |
| $Di_{sp}$ | Inner diameter steel pipe | mm |
| $Di_t$ | Diameter (inner) tunnel | m |
| $Do_d$ | Outer diameter duct | mm |
| $Do_{hsp}$ | Outer diameter fluid-filled pipe | mm |
| $Do_p$ | Outer diameter enclosing pipe | m |
| $Do_{sp}$ | Outer diameter steel pipe | mm |
| $Do_t$ | Diameter (outer) tunnel | m |
| E | $E_a$ | Induced shield voltage phase a | V/m |
| $E_b$ | Induced shield voltage phase b | V/m |
| $E_{bs}$ | Installation constant E | |
| $E_c$ | Induced shield voltage phase c | V/m |
| $e_{hor}$ | Horizontal clearance | mm |
| $E_i$ | Electrical field strength | kV/mm |
| $e_{limit}$ | Limit of thickness of soil layer | m |
| $E_p$ | Induced shield voltage conductor p | V/m |
| $e_{soil}$ | Thickness soil layer | m |
| $e_{ver}$ | Vertical clearance | mm |
| $e_{wall}$ | Clearance to wall | mm |
| $EC$ | Embodied carbon | kgCO$_2$/kg |
| $EE$ | Embodied energy | MJ/kg |
| $\epsilon_0$ | Vacuum permittivity | F/m |
| $\epsilon_{ab}$ | Relative permittivity armour bedding | |
| $\epsilon_c$ | Effective emissivity conductor | |
| $\epsilon_{di}$ | Emissivity duct surface (inner) | |
| $\epsilon_{do}$ | Emissivity duct surface (outer) | |
| $\epsilon_e$ | Emissivity cable | |
| $\epsilon_{encl}$ | Effective emissivity enclosure | |
| $\epsilon_{gas}$ | Dielectric constant of gas in compartment | |
| $\epsilon_{hsj}$ | Effective emissivity protective jacket | |
| $\epsilon_i$ | Relative permittivity insulation material | |
| $\epsilon_j$ | Relative permittivity jacket | |
| $\epsilon_k$ | Heat loss allowance factor | |
| $\epsilon_{prot}$ | Effective emissivity protective cover | |
| $\epsilon_{rad}$ | Effective emissivity | |
| $\epsilon_{shj}$ | Relative permittivity sheath jacket material | |
| $\eta 0_{gas}$ | Reference dynamic viscosity gas | Pa.s |
| $\eta_{di}$ | Reflectivity duct surface (outer) | |
| $\eta_{do}$ | Reflectivity duct surface (outer) | |
| $\eta_e$ | Reflectivity cable | |
| $\eta_{gas}$ | Dynamic viscosity gas | Pa.s |
| $\eta_w$ | Dynamic viscosity water | Pa.s |
| F | $f$ | System frequency | Hz |
| $F_{\alpha}$ | Inclination derating factor | p.u. |
| $F_{ar}$ | Factor $F$ armour losses | |
| $f_{ar}$ | Factor between AC and DC resistance armour | $\Omega$/m |
| $f_{atm}$ | Relation atmospheric pressure to standard atmosphere | |
| $f_{cb}$ | Factor for cross-bonded earthing | |
| $F_e$ | Factor $F_e$ eddy-current losses | |
| $F_{eq}$ | Factor for envelope circle for a group of equal circles | |
| $F_{form}$ | Form factor | |
| $F_g$ | Gravitational force | N/m |
| $F_{ij}$ | View factor object—object | |
| $F_k$ | Imperfect contact thermal factor | |
| $F_{lay,3c}$ | Effective length per unit lay length twisted conductors | |
| $F_{lay,ar}$ | Effective length per unit lay length armour | |
| $F_{lay,c}$ | Effective length per unit lay length conductor strands | |
| $F_{lay,sc}$ | Effective length per unit lay length screen wires | |
| $F_m$ | Mutual radiation coefficient | |
| $F_{mh}$ | Mutual heating coefficient | |
| $f_{ppc}$ | Factor permissible pull force | N/mm$^2$ |
| $F_{ppc}$ | Permissible pull force | N |
| $F_{pt}$ | Function of pressure and temperature | |
| $F_{pull}$ | Pulling force | N |
| $f_{rad}$ | Factor sidewall bearing pressure | N/m |
| $F_{rad}$ | Sidewall bearing pressure | N/m |
| $F_{red}$ | Derating factor | |
| $F_{T10,1}$ | Table 10.1, VDE 0276-1000 | p.u. |
| $F_{T10,3}$ | Table 10.3, VDE 0276-1000 | p.u. |
| $F_{T11,s}$ | Table 11.1, VDE 0276-1000 | p.u. |
| $F_{T11,t}$ | Table 11.2, VDE 0276-1000 | p.u. |
| $F_{T12}$ | Table 12, VDE 0276-1000 | p.u. |
| $F_{T13}$ | Table 13, VDE 0276-1000 | p.u. |
| $f_{wc}$ | Weight correction factor | |
| $F_x$ | Geometrical distance factor for multi-core cables | |
| G | $g$ | Standard acceleration of gravity | m/s$^2$ |
| $G$ | Conductance | S/m |
| $G_1$ | Geometric factor $G_1$ | |
| $G_2$ | Geometric factor $G_2$ cables with separate sheaths | |
| $g_a$ | Substitution coefficient g | |
| $G_b$ | Geometric factor backfill | |
| $g_{bs}$ | Installation constant g | |
| $G_{corr}$ | Geometric factor $G_{corr}$ for jacket around each core | |
| $g_{dry}$ | Geometric constant of circle drying zone | p.u. |
| $G_{encl}$ | Factor G for the calculation of the Nusselt number | |
| $G_{FEA}$ | Geometric factor $G_{FEA}$ based on FEM fitting | |
| $G_{od}$ | Aspect ratio object/duct | |
| $g_s$ | Substitution coefficient $g_s$ for eddy-currents | |
| $G_{s00}$ | Factor $G_{s 0.0}$ | |
| $G_{s05}$ | Factor $G_{s 0.5}$ | |
| $G_{s10}$ | Factor $G_{s 1.0}$ | |
| $g_u$ | Geometric constant of circle buried | |
| $g_x$ | Geometric constant of circle characteristic diameter | p.u. |
| $\gamma_{bessel}$ | Bessel constant | p.u. |
| $\gamma_C$ | Propagation constant | |
| $\gamma_c$ | Skin and proximity effect factor $\gamma$ PAC/GIL conductor | |
| $\gamma_{encl}$ | Skin and proximity effect factor $\gamma$ PAC/GIL enclosure | |
| $\gamma_{euler}$ | Euler's constant | m/s$^2$ |
| $\gamma_i$ | Electrical field coefficient insulation material | mm/kV |
| $\gamma_{prop}$ | Cable propagation constant | |
| $\gamma_t$ | Attainment factor cables | |
| $\gamma_X$ | Attenuation factor for crossing | 1/m |
| $GMD$ | Geometric mean distance between phases of the same system | m |
| $GMD_t$ | Geometric mean distance between earth continuity conductor and the cables of the same system | m |
| $GMR_{ar}$ | Geometric mean radius armour | m |
| $GMR_c$ | Geometric mean radius conductor | m |
| $GMR_{cc}$ | Geometric mean radius conductor bundle | mm |
| $GMR_{sc}$ | Geometric mean radius screen | m |
| $GMR_{sp}$ | Geometric mean radius steel pipe | m |
| $\mathrm{Gr}_c$ | Grashof number conductor→gas | |
| $\mathrm{Gr}_{encl}$ | Grashof number gas→enclosure | |
| $\mathrm{Gr}_{ext}$ | Grashof number riser—air | |
| $\mathrm{Gr}_{gd}$ | Grashof number gas—duct | |
| $\mathrm{Gr}_L$ | Grashof number, ground—air | |
| $\mathrm{Gr}_{og}$ | Grashof number cable—gas | |
| $\mathrm{Gr}_{prot}$ | Grashof number surface→air | |
| H | $H$ | Distance pipe center—ground | m |
| $H_1$ | Inductance $H_1$ armour | H/m |
| $H_2$ | Inductance $H_2$ armour | H/m |
| $H_3$ | Inductance $H_3$ armour | H/m |
| $h_{amb}$ | Pseudo film coefficient of ambient fluid at ground level | W/(K.m$^2$) |
| $h_{atm}$ | Height above sea level | m |
| $h_b$ | Height backfill | mm |
| $h_{bs}$ | Heat dissipation coefficient for black surfaces in free air | W/m$^2$/K$^{5/4}$ |
| $h_{buried}$ | Heat transfer coefficient pipe fully buried | W/(K.m$^2$) |
| $H_c$ | Heat energy content | MJ/m |
| $h_{conv,c}$ | Heat transfer coefficient convection conductor—gas | W/(K.m$^2$) |
| $h_{conv,encl}$ | Heat transfer coefficient convection gas—enclosure | W/m2.K |
| $h_{conv,ext}$ | Heat transfer coefficient convection riser—air | W/(K.m$^2$) |
| $h_{conv,gd}$ | Heat transfer coefficient convection gas—duct | W/(K.m$^2$) |
| $h_{conv,int}$ | Heat transfer coefficient convection cable—riser | W/(K.m$^2$) |
| $h_{conv,og}$ | Heat transfer coefficient convection cable—gas | W/(K.m$^2$) |
| $h_{conv,sa}$ | Heat transfer coefficient convection surface—air | W/(K.m$^2$) |
| $h_{em}$ | Factor $h$ emergency overload | |
| $h_{era}$ | Heat transfer coefficient convection ERA | W/(K.m$^2$) |
| $h_{ext}$ | Heat transfer coefficient external | W/(K.m$^2$) |
| $h_{ground}$ | Heat transfer coefficient part of pipe in contact with ground | W/(K.m$^2$) |
| $h_{in}$ | Heat transfer coefficient internal | W/(K.m$^2$) |
| $h_{lg}$ | Ratio of heat dissipation coefficients | |
| $h_{rad,ce}$ | Heat transfer coefficient radiation conductor—enclosure | W/(K.m$^2$) |
| $h_{rad,ext}$ | Heat transfer coefficient radiation riser—air | W/(K.m$^2$) |
| $h_{rad,int}$ | Heat transfer coefficient radiation cable—riser | W/(K.m$^2$) |
| $h_{rad,sa}$ | Heat transfer coefficient radiation surface—air | W/(K.m$^2$) |
| $H_s$ | Conductance sheath | H/m |
| $h_{soil}$ | Heat transfer coefficient wall—soil | W/(K.m$^2$) |
| $H_{sun}$ | Intensity of solar radiation | W/m$^2$ |
| $h_t$ | Height (inner) | m |
| $h_{T4}$ | Ratio of thermal resistance to ambient | |
| $H_{tc}$ | Parameter Hc trough cover | |
| $h_{tr}$ | Heat transfer coefficient | W/(K.m$^2$) |
| $H_{ts}$ | Parameter Hs depending on air velocity | |
| $H_x$ | Magnetic field x | mH |
| $H_y$ | Magnetic field y | mH |
| I | $I_{ar}$ | Induced circulating current armour | A |
| $I_c$ | Conductor current | A |
| $I_C$ | Capacitive load current | A/m |
| $I_{c,LF}$ | Conductor root mean square current | A |
| $I_{c,max}$ | Highest current load of line | A |
| $I_{c,peak}$ | Permissible peak cyclic load current | A |
| $I_{c,sum}$ | Total current for all parallel systems | A |
| $I_{Ce}$ | Capacitive earth short-circuit current | A/m |
| $I_{em}$ | Emergency overload current | A |
| $I_{EMF}$ | Phase current for EMF calculation | A |
| $I_k$ | Complex conductor current | A |
| $I_{k0}$ | Phase-to-ground fault current | A |
| $I_{k1}$ | Phase-to-neutral fault current | A |
| $I_{k2}$ | Phase-to-phase fault current | A |
| $I_{k3}$ | Three-phase symmetrical fault current | A |
| $I_{k,per}$ | Short-circuit current, permissible | kA |
| $I_{ka}$ | Complex conductor current a | A |
| $I_{kAD}$ | Short-circuit current, adiabatic | kA |
| $I_{kb}$ | Complex conductor current a | A |
| $I_{kc}$ | Complex conductor current c | A |
| $I_{kSC}$ | Short-circuit current, effective | kA |
| $I_{kx}$ | Split fault current | A |
| $I_{method}$ | Current calculation method | |
| $I_R$ | Transient conductor current | A |
| $I_s$ | Induced circulating current shield | A |
| $I_{sp}$ | Induced circulating current pipe | A |
| $I_{ss}$ | Steady-state current before transient | A |
| $inst_{air}$ | Installation in air | |
| $inst_{buried}$ | Installation buried | |
| $inst_{elec}$ | Installation of cables for electrical calculations | |
| $inst_{riser}$ | Installation of cables in riser | |
| $inst_{sea}$ | Installation of subsea cables | |
| $inst_t$ | Installation in air inside a room | |
| J | $j_{max}$ | Phase angle range | ° |
| K | $K_0$ | Coefficient K gas (PAC/GIL) | |
| $K_{02}$ | Factor $K_{0.2}$ | |
| $K_{06}$ | Factor $K_{0.6}$ | |
| $K_1$ | Screening factor | |
| $K_{10}$ | Factor $K_{1.0}$ | |
| $k_4$ | Thermal conductivity soil | W/(m.K) |
| $K_A$ | Coefficient K in air | |
| $k_{air}$ | Thermal conductivity air | W/(m.K) |
| $k_{ar}$ | Thermal conductivity armour material | W/(m.K) |
| $K_{BICC}$ | Constant relating to conductor formation | |
| $k_{Boltz}$ | Boltzmann constant | J/K |
| $k_c$ | Thermal conductivity conductor material | W/(m.K) |
| $K_{ce}$ | Radiation shape factor conductor—enclosure | |
| $K_{cv}$ | Convection factor | |
| $K_{dyn}$ | Corrected dynamic friction coefficient | |
| $k_{encl}$ | Thermal conductivity enclosure | W/(m.K) |
| $K_G$ | Factor $K_G$ | |
| $k_{gas}$ | Thermal conductivity gas | W/(m.K) |
| $K_{GMR}$ | Factor geometric mean radius | |
| $k_H$ | Heinhold characteristic diameter coefficient | |
| $k_{hsf}$ | Thermal conductivity fluid | W/(m.K) |
| $k_{hsi}$ | Thermal conductivity pipe insulation material | W/(m.K) |
| $k_{hsj}$ | Thermal conductivity protective jacket material | W/(m.K) |
| $k_{hsp}$ | Thermal conductivity fluid-filled pipe material | W/(m.K) |
| $K_k$ | Specific short-circuit parameter | A.s$^{1/2}$/mm$^2$ |
| $k_l$ | Temperature rise factor in air | |
| $k_{LF}$ | Load loss coefficient | p.u. |
| $K_{od}$ | Diameter ratio object/duct | |
| $k_p$ | Proximity effect coefficient | |
| $K_{par}$ | Constant $K_{par}$ (Ovuworie) | |
| $k_{prot}$ | Thermal conductivity protective cover | W/(m.K) |
| $K_r$ | Radiation shape factor | |
| $k_{r2}$ | Temperature rise ratio $\delta\theta_{SPK}/\delta\theta_c$ | p.u. |
| $k_s$ | Skin effect coefficient | |
| $k_{sa}$ | Convection factor (Heinhold) | |
| $k_{sa,1}$ | Factor 1 heat transfer coefficient convection | |
| $k_{sa,2}$ | Factor 2 heat transfer coefficient convection | |
| $k_{sc}$ | Thermal conductivity screen material | W/(m.K) |
| $k_{sh}$ | Thermal conductivity sheath material | W/(m.K) |
| $k_{skid}$ | Thermal conductivity skid wires | |
| $k_{sp}$ | Thermal conductivity steel pipe material | W/(m.K) |
| $k_t$ | Temperature rise ratio | p.u. |
| $K_t$ | Effective emissivity object surface | |
| $K_{vermeer}$ | Vermeer constant for convection heat transfer | |
| $k_w$ | Thermal conductivity water | W/(m.K) |
| $K_x$ | Factor for fictitious diameter by Neher | |
| $k_X$ | Number of heat sources crossing | |
| $\kappa_i$ | Electrical conductivity insulation material | S/m |
| $\kappa_j$ | Electrical conductivity jacket material | S/m |
| L | $L$ | Inductance matrix | H/m |
| $L_0$ | Reference length of the tunnel | m |
| $L_a$ | Self inductance conductor | H/m |
| $L_b$ | Vertical center backfill | mm |
| $L_{b4}$ | Depth trench multi-layer backfill | m |
| $L_c$ | Depth of laying of sources | mm |
| $L_{char}$ | Characteristic length earth surface | |
| $L_{cm}$ | Depth of laying | m |
| $L_{crit}$ | Critical length | km |
| $L_d$ | Length duct | m |
| $L_{deep}$ | Deep burial thermal inertia equivalent depth | m |
| $L_{dry}$ | Depth characteristic diameter drying zone | m |
| $L_{dw}$ | Length of duct in water | m |
| $L_h$ | Depth of laying of crossing element | mm |
| $L_i$ | Inductance conductor i | H/m |
| $L_{lay,3c}$ | Length of lay twisted conductors | mm |
| $L_{lay,ar}$ | Length of lay armour | mm |
| $L_{lay,c}$ | Length of lay conductor strands | mm |
| $L_{lay,sc}$ | Length of lay screen wires | mm |
| $L_{leg}$ | Section length | m |
| $L_{link}$ | Span length | m |
| $L_m$ | Inductance (mean) | H/m |
| $L_r$ | Depth of laying of the rated object | mm |
| $L_{sys}$ | System length | m |
| $L_T$ | Length tunnel | m |
| $\lambda_0$ | Substitution coefficient $\lambda_0$ for eddy-currents | |
| $\lambda_1$ | Loss factor shield (screen/sheath) | |
| $\lambda_{11}$ | Loss factor shield, circulating currents | |
| $\lambda_{12}$ | Loss factor shield, eddy currents | |
| $\lambda_2$ | Loss factor armour | |
| $\lambda_{21}$ | Loss factor armour, circulating currents | |
| $\lambda_{22}$ | Loss factor shield, eddy currents | |
| $\lambda_3$ | Loss factor steel pipe pipe-type cable | |
| $\lambda_4$ | Loss factor magnetic duct | |
| $\lambda_d$ | Factor dielectric losses | |
| $\lambda_{gas}$ | Ratio $c_p/c_v$ | |
| $\lambda_i$ | Parameter $\lambda$ for linear density of dielectric losses | |
| $\lambda_t$ | Relaxation parameter | |
| $LF$ | Load factor, daily | p.u. |
| $LF_w$ | Load factor, weekly | p.u. |
| $LF_y$ | Load factor, yearly | p.u. |
| $LME$ | London Metal Exchange | USD/mt |
| M | $M$ | Cyclic rating factor | p.u. |
| $m_0$ | Substitution coefficient $m_0$ for eddy-currents | Hz.m/$\Omega$ |
| $M_0$ | Coefficient M partial transient temperature rise | s |
| $M_1$ | Corrected cyclic rating factor | K |
| $M_{ab}$ | Armour bedding material | |
| $m_{ab}$ | Mass armour bedding | kg/m |
| $M_{ar}$ | Armour material | |
| $m_{ar}$ | Mass armour | kg/m |
| $M_c$ | Conductor material | |
| $m_c$ | Mass conductor | kg/m |
| $M_{cable}$ | Cable material | |
| $M_{comp}$ | Insulating gas material | |
| $M_d$ | Duct material | |
| $M_e$ | Substitution coefficient $M_e$ to calculate factor $F_e$ | |
| $m_E$ | Parameter m earth return | |
| $m_{EMF}$ | Number of time steps | |
| $M_{encl}$ | Enclosure material | |
| $M_f$ | Filler material | |
| $m_f$ | Mass filler | kg/m |
| $M_{gas}$ | Gas and gas-mixtures | |
| $m_{hollow}$ | Mass hollow cable | kg/m |
| $M_{hsf}$ | Fluid material | |
| $M_{hsi}$ | Pipe insulation material | |
| $M_{hsj}$ | Protective jacket material | |
| $M_{hsp}$ | Fluid-filled pipe material | |
| $M_i$ | Insulation material | |
| $m_i$ | Mass insulation | kg/m |
| $M_{IEEE}$ | Soil material IEEE 442 | |
| $M_j$ | Jacket material | |
| $m_j$ | Mass jacket | kg/m |
| $M_k$ | Thermal contact factor | s$^{1/2}$ |
| $m_{metal}$ | Mass metallic parts | kg/m |
| $M_{mol}$ | Molar mass | g/mol |
| $m_{mol}$ | Molecular mass | mol |
| $m_{Nu,L}$ | Factor m | |
| $m_{Nu,w}$ | Factor m | |
| $M_p$ | Pipe material | |
| $M_{prot}$ | Protective cover material | |
| $M_{riser}$ | Riser material | |
| $M_{sc}$ | Screen material | |
| $m_{sc}$ | Mass metallic screen | kg/m |
| $M_{seabed}$ | Seabed material | |
| $M_{sh}$ | Sheath material | |
| $m_{sh}$ | Mass metallic sheath | kg/m |
| $M_{shj}$ | Sheath jacket material | |
| $m_{shj}$ | Mass jacket over each core | kg/m |
| $M_{skid}$ | Skid wire material | |
| $m_{skid}$ | Mass skid wires | kg/m |
| $M_{soil}$ | Soil material | |
| $M_{sp}$ | Steel pipe material | |
| $m_{sp}$ | Mass steel pipe | kg/m |
| $M_{spf}$ | Steel pipe filling medium | |
| $m_{tape}$ | Mass tapes | kg/m |
| $m_{tot}$ | Mass cable | kg/m |
| $m_{z,ar}$ | Parameter m armour | |
| $m_{z,c}$ | Parameter m conductor | |
| $m_{z,e}$ | Parameter m earth | |
| $m_{z,s}$ | Parameter m shield | |
| $m_{z,sc}$ | Parameter m screen | |
| $m_{z,sh}$ | Parameter m sheath | |
| $\mu$ | Loss factor daily load variation | p.u. |
| $\mu_0$ | Vacuum permeability | H/m |
| $\mu_{dyn}$ | Dynamic friction coefficient | |
| $\mu_e$ | Longitudinal relative permeability steel wires | |
| $\mu_E$ | Magnetic permeability of earth | H/m |
| $\mu_s$ | Relative permeability steel wires | |
| $\mu_t$ | Transverse relative permeability steel wires | |
| $\mu_w$ | Loss factor weekly load variation | p.u. |
| $\mu_y$ | Loss factor yearly load variation | p.u. |
| N | $N_0$ | Coefficient N partial transient temperature rise | s$^2$ |
| $n_{a,1}$ | Number of wires armour 1 | |
| $n_{a,2}$ | Number of wires armour 2 | |
| $n_{ar}$ | Number of wires armour | |
| $N_{Avogrado}$ | Avogadro constant | 1/mol |
| $N_b$ | Number of loaded objects in backfill | |
| $n_c$ | Number of conductors cable | |
| $N_c$ | Number of sources in system | |
| $n_{cc}$ | Number of conductors combined | |
| $n_{cg}$ | Number of conductors PAC/GIL | |
| $n_{cw}$ | Number of wires conductor | |
| $n_{cycle}$ | Number of load cycles | |
| $N_e$ | Substitution coefficient $N_e$ to calculate factor $F_e$ | |
| $N_{hor}$ | Number of cable groups beside each other | |
| $n_{Nu,r}$ | Factor n | |
| $N_{ph}$ | Number of phases in system | |
| $n_{ph}$ | Number of phases in a cable | |
| $N_{sea}$ | Number of subsea cables | |
| $n_{seg}$ | Number of segments in Milliken conductor | |
| $N_{sum}$ | Total number of objects in an air-filled space | |
| $n_{sw}$ | Number of wires screen | |
| $N_{sys}$ | Number of parallel systems in the same confinement | |
| $N_{ver}$ | Number of cable groups above each other | |
| $N_X$ | Number of intervals | |
| $\nu$ | Summation step 1 - $N_X$ | |
| $\nu_{air}$ | Kinematic viscosity air | m$^2$/s |
| $\mathrm{Nu}_c$ | Nusselt number conductor—gas | |
| $\mathrm{Nu}_{encl}$ | Nusselt number gas—enclosure | |
| $\mathrm{Nu}_{ext}$ | Nusselt number riser—air | |
| $\nu_{gas}$ | Kinematic viscosity gas | m$^2$/s |
| $\mathrm{Nu}_{gd}$ | Nusselt number gas—duct | |
| $\mathrm{Nu}_{int}$ | Nusselt number cable—riser | |
| $\mathrm{Nu}_L$ | Nusselt number, ground—air | |
| $\mathrm{Nu}_{og}$ | Nusselt number cable—gas | |
| $\mathrm{Nu}_{prot}$ | Nusselt number surface—air | |
| $\nu_{sc}$ | Elongation screen | $\%$ |
| $\nu_{soil}$ | Soil moisture content | $\%$ |
| $\mathrm{Nu}_w$ | Nusselt number surface—water | |
| $\nu_w$ | Kinematic viscosity water | m$^2$/s |
| O | $\omega$ | Angular frequency | rad/s |
| P | $p_{a,1}$ | Length of lay armour 1 | mm |
| $p_{a,2}$ | Length of lay armour 2 | mm |
| $p_{ab}$ | Apportioning factor armour bedding | |
| $p_{atm}$ | Atmospheric air pressure | hPa |
| $P_C$ | Charging capacity | var/m |
| $p_{cb}$ | Minor ratio of section lengths | |
| $p_{comp}$ | Gas pressure in compartment | bar |
| $P_G$ | Active power generator-side | kW |
| $p_{gas}$ | Pressure gas | Pa |
| $p_i$ | Apportioning factor insulation | |
| $p_j$ | Apportioning factor jacket | |
| $P_L$ | Active power load-side | kW |
| $p_{Mie}$ | Factor $p$ (Mie1905) | |
| $p_{Nu,r}$ | Factor p | |
| $p_{shj}$ | Apportioning factor sheath jacket | |
| $p_{soil}$ | Depth of image source | |
| $p_{tr}$ | Effective perimeter trough | m |
| $p_w$ | Pressure water | bar |
| $P_X$ | Substitution coefficient P to calculate loss factor by circulating currents | |
| $\phi$ | Angle of power factor | rad |
| $\Phi_{air}$ | Relative humidity air | $\%$ |
| $\phi_{ar}$ | Angle between armour and cable axis | rad |
| $\phi_{arc}$ | Bend angle | rad |
| $\phi_{el}$ | Angle to the plane of a section | rad |
| $\phi_{tr}$ | Parameter $\phi$ trough | |
| $\pi$ | Archimedes' constant $\pi$ | |
| $\mathrm{Pr}_{air}$ | Prandtl number air | |
| $\mathrm{Pr}_{gas}$ | Prandtl number gas | |
| $\mathrm{Pr}_w$ | Prandtl number water | |
| Q | $q_1$ | Ratio of losses screen bedding,screen serving | |
| $q_2$ | Ratio of losses armour bedding | |
| $q_3$ | Ratio of losses affecting jacket | |
| $q_4$ | Ratio of losses environment | |
| $Q_A$ | Thermal capacitance A transient thermal circuit | J/(m.K) |
| $Q_{ab}$ | Thermal capacitance armour bedding | J/(m.K) |
| $Q_{ar}$ | Thermal capacitance armour | J/(m.K) |
| $q_{ar}$ | Ratio of losses armour | |
| $Q_B$ | Thermal capacitance B transient thermal circuit | J/(m.K) |
| $Q_{B,ab}$ | Thermal capacitance B transient thermal circuit, armour bedding | J/(m.K) |
| $Q_{B,d}$ | Thermal capacitance B transient thermal circuit, duct | J/(m.K) |
| $Q_{B,f}$ | Thermal capacitance B transient thermal circuit, filler | J/(m.K) |
| $Q_{B,i}$ | Thermal capacitance B transient thermal circuit, insulation | J/(m.K) |
| $Q_{B,j}$ | Thermal capacitance B transient thermal circuit, jacket | J/(m.K) |
| $Q_{B,s}$ | Thermal capacitance B transient thermal circuit, screen/sheath | J/(m.K) |
| $Q_c$ | Thermal capacitance conductor | J/(m.K) |
| $q_{cb}$ | Major ratio of section lengths | |
| $Q_{ct}$ | Thermal capacitance conductor (IEC 60853) | J/(m.K) |
| $Q_d$ | Thermal capacitance duct wall | J/(m.K) |
| $Q_{d,fill}$ | Thermal capacitance duct filling | J/(m.K) |
| $Q_f$ | Thermal capacitance filler | J/(m.K) |
| $q_f$ | Ratio of losses filler | |
| $Q_G$ | Reactive power generator-side | kvar |
| $Q_i$ | Thermal capacitance insulation | J/(m.K) |
| $Q_{it}$ | Thermal capacitance insulation (IEC 60853) | J/(m.K) |
| $Q_{it1}$ | Thermal capacitance insulation, 1st portion (IEC 60853) | J/(m.K) |
| $Q_{it2}$ | Thermal capacitance insulation, 2nd portion (IEC 60853) | J/(m.K) |
| $Q_j$ | Thermal capacitance jacket | J/(m.K) |
| $Q_L$ | Reactive power load-side | kvar |
| $q_{Mie}$ | Factor $q$ (Mie1905) | |
| $Q_s$ | Thermal capacitance sheath+sheath | J/(m.K) |
| $q_s$ | Ratio of losses screen/sheath | |
| $Q_{sc}$ | Thermal capacitance screen | J/(m.K) |
| $Q_{scb}$ | Thermal capacitance screen bedding | J/(m.K) |
| $Q_{scs}$ | Thermal capacitance screen serving | J/(m.K) |
| $Q_{sh}$ | Thermal capacitance sheath | J/(m.K) |
| $Q_{shj}$ | Thermal capacitance sheath jacket | J/(m.K) |
| $Q_{sp}$ | Thermal capacitance steel pipe | J/(m.K) |
| $Q_{sr}$ | Reactive power shunt reactor | kvar |
| $Q_{tot}$ | Thermal capacitance, transient | J/(m.K) |
| $Q_X$ | Substitution coefficient Q to calculate loss factor by circulating currents | |
| $q_x$ | Factor characteristic diameter | |
| R | $r_1$ | Construction circle circumscribing the shaped conductors | mm |
| $R_1$ | Positive sequence resistance | $\Omega$/m |
| $R_{ar}$ | Electrical resistance armour | $\Omega$/m |
| $r_{arc}$ | Bend radius | m |
| $r_b$ | Equivalent radius backfill | mm |
| $r_c$ | Radius conductor | mm |
| $R_c$ | Electrical resistance conductor | $\Omega$/m |
| $R_{c1}$ | Thermal resistance part 1 | K.m/W |
| $R_{c2}$ | Thermal resistance part 2 | K.m/W |
| $R_{c20}$ | Electrical resistance DC conductor 20°C | $\Omega$/m |
| $R_{c3}$ | Thermal resistance part 3 | K.m/W |
| $R_{c4}$ | Thermal resistance part 4 | K.m/W |
| $R_{cDC}$ | Electrical resistance DC conductor | $\Omega$/m |
| $R_{CG}$ | Thermal resistance multi-layer backfill | K.m/W |
| $R_{co}$ | Standard DC resistance of conductor | $\Omega$/km |
| $r_{core}$ | Radius over core cable | mm |
| $R_{ct}$ | Resistance earth continuity conductor | $\Omega$/m |
| $R_e$ | Electrical resistance shield/armour | $\Omega$/m |
| $R_E$ | Equivalent resistance of earth return path | $\Omega$/m |
| $R_{encl}$ | Electrical resistance enclosure | $\Omega$/m |
| $R_{encl20}$ | Electrical resistance DC enclosure 20°C | $\Omega$/m |
| $R_{enclDC}$ | Electrical resistance DC enclosure | $\Omega$/m |
| $R_f$ | Tower footing impedance | $\Omega$ |
| $r_g$ | Geometric mean radius of the ground conductor | m |
| $R_{gas}$ | Specific gas constant | J/(kg.K) |
| $R_{gas0}$ | Universal molar gas constant | |
| $R_h$ | Resistance link | $\Omega$/m |
| $r_{ij}$ | Coefficient r view factor | |
| $r_{isc}$ | Radius above the inner semi-conducting layer | mm |
| $R_l$ | Ground resistance load | $\Omega$ |
| $R_{max}$ | Resistance of conductor at emergency rating | $\Omega$/m |
| $r_{mbi}$ | Minimal bending radius, installation | m |
| $r_{mbif}$ | Factor minimal bending radius, installation | |
| $r_{mbp}$ | Minimal bending radius, pulling | m |
| $r_{mbpf}$ | Factor minimal bending radius, pulling | |
| $r_o$ | Radius of object | m |
| $r_{osc}$ | Radius over capacitive insulation layers | mm |
| $R_{q11}$ | Thermal resistance 11 multi-layer backfill | K.m/W |
| $R_{q12}$ | Thermal resistance 12 multi-layer backfill | K.m/W |
| $R_{q13}$ | Thermal resistance 13 multi-layer backfill | K.m/W |
| $R_{q21}$ | Thermal resistance 21 multi-layer backfill | K.m/W |
| $R_{q22}$ | Thermal resistance 22 multi-layer backfill | K.m/W |
| $R_{q31}$ | Thermal resistance 31 multi-layer backfill | K.m/W |
| $R_{q32}$ | Thermal resistance 32 multi-layer backfill | K.m/W |
| $R_r$ | Ground resistance receiving end | $\Omega$ |
| $R_s$ | Electrical resistance shield | $\Omega$/m |
| $r_s$ | Mean radius shield | m |
| $R_{sc}$ | Electrical resistance screen | $\Omega$/m |
| $R_{sh}$ | Electrical resistance sheath | $\Omega$/m |
| $R_{skid}$ | Electrical resistance skid wires | $\Omega$/m |
| $R_{so}$ | Electrical resistance screen/sheath 20°C | $\Omega$/m |
| $r_{sp}$ | Mean radius steel pipe | mm |
| $R_{sp}$ | Electrical resistance steel pipe | $\Omega$/m |
| $R_{ss}$ | Resistance of conductor before emergency rating | $\Omega$/m |
| $R_{sw}$ | Resistance skywire | $\Omega$/m |
| $r_x$ | Radius to point x in insulation | mm |
| $r_{z1}$ | Radius conductor | m |
| $r_{z2}$ | Radius shield (inner) | m |
| $r_{z2,sc}$ | Radius screen (inner) | m |
| $r_{z2,sh}$ | Radius sheath (inner) | m |
| $r_{z3}$ | Radius shield (outer) | m |
| $r_{z3,sc}$ | Radius screen (outer) | m |
| $r_{z3,sh}$ | Radius sheath (outer) | m |
| $r_{z4}$ | Radius armour (inner) | m |
| $r_{z5}$ | Radius armour (outer) | m |
| $r_{z6}$ | Radius outersheath | m |
| $\mathrm{Ra}_c$ | Rayleigh number conductor→gas | |
| $\mathrm{Ra}_{encl}$ | Rayleigh number gas→enclosure | |
| $\mathrm{Ra}_{ext}$ | Rayleigh number riser—air | |
| $\mathrm{Ra}_{int}$ | Rayleigh number gas→riser | |
| $\mathrm{Ra}_L$ | Rayleigh number ground—air | |
| $\mathrm{Ra}_{prot}$ | Rayleigh number surface→air | |
| $\mathrm{Re}_{air}$ | Reynolds number air | |
| $\mathrm{Re}_w$ | Reynolds number water | |
| $RF$ | Reduction factor | |
| $\rho_4$ | Thermal resistivity soil | K.m/W |
| $\rho_{4d}$ | Thermal resistivity dry soil | K.m/W |
| $\rho_{ab}$ | Thermal resistivity armour bedding | K.m/W |
| $\rho_{ab,1}$ | Thermal resistivity armour bedding 1 | K.m/W |
| $\rho_{ab,2}$ | Thermal resistivity armour bedding 2 | K.m/W |
| $\rho_{ar}$ | Specific electrical resistivity armour material | $\Omega$.m |
| $\rho_b$ | Thermal resistivity backfill | K.m/W |
| $\rho_{b1}$ | Thermal resistivity surface layer | K.m/W |
| $\rho_{b2}$ | Thermal resistivity middle layer | K.m/W |
| $\rho_c$ | Electrical resistivity conductor material | $\Omega$.m |
| $\rho_{corr}$ | Thermal resistivity corrugation filling | K.m/W |
| $\rho_{cr}$ | Thermal resistivity conductor material | K.m/W |
| $\rho_{cs}$ | Thermal resistivity conductor shield | K.m/W |
| $\rho_{ct}$ | Thermal resistivity conductor tape | K.m/W |
| $\rho_d$ | Thermal resistivity duct material | K.m/W |
| $\rho_{d,fill}$ | Thermal resistivity duct filling | K.m/W |
| $\rho_E$ | Specific electrical resistivity of soil | $\Omega$.m |
| $\rho_{encl}$ | Specific electrical resistivity enclosure material | $\Omega$.m |
| $\rho_f$ | Thermal resistivity filler | K.m/W |
| $\rho_{gas}$ | Density gas | kg/m$^3$ |
| $\rho_i$ | Thermal resistivity insulation material | K.m/W |
| $\rho_{is}$ | Thermal resistivity insulation screen | K.m/W |
| $\rho_j$ | Thermal resistivity jacket material | K.m/W |
| $\rho_{k2}$ | Thermal resistivity layer below | K.m/W |
| $\rho_{k20}$ | Electrical resistivity metallic component | $\Omega$.m |
| $\rho_{k3}$ | Thermal resistivity layer above | K.m/W |
| $\rho_{ki}$ | Thermal resistivity adjacent non-metallic material | K.m/W |
| $\rho_p$ | Thermal resistivity pipe material | K.m/W |
| $\rho_s$ | Specific electrical resistivity shield (screen/sheath) | $\Omega$.m |
| $\rho_{sc}$ | Specific electrical resistivity screen material | $\Omega$.m |
| $\rho_{scb}$ | Thermal resistivity screen bedding | K.m/W |
| $\rho_{scs}$ | Thermal resistivity screen serving | K.m/W |
| $\rho_{sh}$ | Specific electrical resistivity sheath material | $\Omega$.m |
| $\rho_{shj}$ | Thermal resistivity sheath jacket material | K.m/W |
| $\rho_{skid}$ | Specific electrical resistivity skid wire material | $\Omega$.m |
| $\rho_{sp}$ | Specific electrical resistivity steel pipe material | $\Omega$.m |
| $\rho_t$ | Thermal resistivity wall | K.m/W |
| S | $S$ | Mean distance between the phases | m |
| $S_{ab}$ | Distance phases a — b | m |
| $S_{ac}$ | Distance phases a — c | m |
| $s_{air}$ | Axial spacing between objects | m |
| $S_{ap}$ | Distance phases a — p (ground) | m |
| $s_{b1}$ | Thickness surface layer | m |
| $s_{b2}$ | Thickness middle layer | m |
| $s_{b3}$ | Thickness from object to top of bedding layer | m |
| $s_{b4}$ | Thickness from object to bottom of bedding layer | m |
| $S_{bc}$ | Distance phases b — c | m |
| $S_{bp}$ | Distance phases b — p (ground) | m |
| $s_c$ | Separation of conductors in a system | mm |
| $S_{cp}$ | Distance phases c — p (ground) | m |
| $S_G$ | Apparent power generator-side | kVA |
| $S_{gas}$ | Sutherland's constant | K |
| $s_{ij}$ | Spacing object—object | |
| $S_k$ | Cross-sectional area metallic component | mm$^2$ |
| $S_m$ | Separation of conductors in a system | m |
| $s_{Nu,r}$ | Factor s | |
| $S_p$ | Distance between phases a/b/c + conductor p | m |
| $s_{S1}$ | Spacing between phases minor section 1 | p.u. |
| $s_{S2}$ | Spacing between phases minor section 2 | p.u. |
| $s_{S3}$ | Spacing between phases minor section 3 | p.u. |
| $S_{sp}$ | Mean distance between the phases, pipe-type cables | $\Omega$/m |
| $\sigma$ | Stefan Boltzmann constant | W/m$^2$K$^4$ |
| $\sigma_{ab}$ | Volumetric heat capacity armour bedding | J/(K.m$^3$) |
| $\sigma_{ab,1}$ | Volumetric heat capacity armour bedding 1 | J/(K.m$^3$) |
| $\sigma_{ab,2}$ | Volumetric heat capacity armour bedding 2 | J/(K.m$^3$) |
| $\sigma_{ar}$ | Volumetric heat capacity armour material | J/(K.m$^3$) |
| $\sigma_c$ | Volumetric heat capacity conductor material | J/(K.m$^3$) |
| $\sigma_d$ | Volumetric heat capacity duct material | J/(K.m$^3$) |
| $\sigma_{d,fill}$ | Volumetric heat capacity duct filling | J/(K.m$^3$) |
| $\sigma_{encl}$ | Volumetric heat capacity enclosure material | J/(K.m$^3$) |
| $\sigma_f$ | Volumetric heat capacity filler | J/(K.m$^3$) |
| $\sigma_i$ | Volumetric heat capacity insulation material | J/(K.m$^3$) |
| $\sigma_j$ | Volumetric heat capacity jacket material | J/(K.m$^3$) |
| $\sigma_{k2}$ | Volumetric heat capacity layer below | J/(K.m$^3$) |
| $\sigma_{k3}$ | Volumetric heat capacity layer above | J/(K.m$^3$) |
| $\sigma_{kc}$ | Volumetric heat capacity metallic component | J/(K.m$^3$) |
| $\sigma_{ki}$ | Volumetric heat capacity adjacent non-metallic material | J/(K.m$^3$) |
| $\sigma_{prot}$ | Volumetric heat capacity protective cover | J/(K.m$^3$) |
| $\sigma_{sc}$ | Volumetric heat capacity screen material | J/(K.m$^3$) |
| $\sigma_{scb}$ | Volumetric heat capacity screen bedding | J/(K.m$^3$) |
| $\sigma_{scs}$ | Volumetric heat capacity screen serving | J/(K.m$^3$) |
| $\sigma_{sh}$ | Volumetric heat capacity sheath material | J/(K.m$^3$) |
| $\sigma_{shj}$ | Volumetric heat capacity sheath jacket material | J/(K.m$^3$) |
| $\sigma_{skid}$ | Volumetric heat capacity skid wires | J/(K.m$^3$) |
| $\sigma_{sp}$ | Volumetric heat capacity steel pipe material | J/(K.m$^3$) |
| $\sigma_{sun}$ | Absorption coefficient solar radiation | |
| $SIL$ | Surge impedance loading | MW |
| T | $T0_{gas}$ | Gas reference temperature | K |
| $T_1$ | Thermal resistance conductor—sheath | K.m/W |
| $t_1$ | Thickness insulation—sheath | mm |
| $t_{1t}$ | Thickness insulation—sheath, transient | mm |
| $T_2$ | Thermal resistance armour bedding | K.m/W |
| $t_2$ | Thickness armour bedding | mm |
| $t_{2i}$ | Thickness of insulation between conductors | mm |
| $T_3$ | Thermal resistance jacket | K.m/W |
| $t_3$ | Thickness armour serving | mm |
| $T_{4d}$ | Thermal resistance daily load cycle | K.m/W |
| $T_{4db}$ | Thermal resistance backfill correction | K.m/W |
| $T_{4fem}$ | Thermal resistance finite element method | K.m/W |
| $T_{4i}$ | Thermal resistance medium in the duct | K.m/W |
| $T_{4ii}$ | Thermal resistance duct wall | K.m/W |
| $T_{4iii}$ | Thermal resistance ambient | K.m/W |
| $T_{4\mu}$ | Thermal resistance ambient | K.m/W |
| $T_{4pi}$ | Thermal resistance of medium in the air-filled pipe with objects | K.m/W |
| $T_{4pii}$ | Thermal resistance pipe wall | K.m/W |
| $T_{4piii}$ | Thermal resistance pipe—ambient | K.m/W |
| $T_{4ss}$ | Thermal resistance steady-state | K.m/W |
| $T_{4t}$ | Equivalent thermal resistance for tunnel | K.m/W |
| $T_{4w}$ | Thermal resistance weekly load cycle | K.m/W |
| $T_{4y}$ | Thermal resistance yearly load cycle | K.m/W |
| $T_A$ | Thermal resistance A transient thermal circuit | K.m/W |
| $T_a$ | Star thermal resistance air | K.m/W |
| $T_{a0}$ | Apparent thermal resistance a | K.m/W |
| $t_{a,1}$ | Thickness armour 1 | mm |
| $t_{a,2}$ | Thickness armour 2 | mm |
| $t_{ab}$ | Thickness armour bedding | mm |
| $T_{ab}$ | Thermal resistance armour bedding | K.m/W |
| $t_{ab,1}$ | Thickness armour bedding 1 | mm |
| $t_{ab,2}$ | Thickness armour bedding 2 | mm |
| $T_{air}$ | Absolute air temperature | K |
| $t_{ar}$ | Thickness armour | mm |
| $T_{at}$ | Thermal resistance convection air—tunnel | K.m/W |
| $T_{axial}$ | Axial thermal resistance due to the movement of air through the tunnel | K.m/W |
| $T_B$ | Thermal resistance B transient thermal circuit | K.m/W |
| $T_{b0}$ | Apparent thermal resistance b | K.m/W |
| $T_{bulk}$ | Bulk temperature | K |
| $t_c$ | Thickness of hollow conductor | mm |
| $T_C$ | Thermal resistance C transient thermal circuit | K.m/W |
| $t_{comp}$ | Thickness compartment | m |
| $T_{conv,ce}$ | Thermal resistance convection conductor—enclosure | K.m/W |
| $T_{conv,int}$ | Thermal resistance convection cable—riser | K.m/W |
| $T_{conv,sa}$ | Thermal resistance convection surface—air | K.m/W |
| $t_{corr}$ | Thickness corrugation filling | mm |
| $t_{cs}$ | Thickness conductor shield | mm |
| $T_{cs}$ | Thermal resistance conductor shield | K.m/W |
| $t_{ct}$ | Thickness conductor tape | mm |
| $T_{ct}$ | Thermal resistance conductor tape | K.m/W |
| $T_d$ | Internal thermal resistance for dielectric losses | K.m/W |
| $t_d$ | Thickness duct | mm |
| $T_{dsh}$ | Thermal resistance corrugation filling | K.m/W |
| $T_e$ | External thermal resistance of tunnel | K.m/W |
| $t_{EMF}$ | Time step to calculate current source | s |
| $t_{encl}$ | Thickness enclosure | m |
| $T_{eq}$ | Thermal resistance, equivalent | K.m/W |
| $t_f$ | Thickness of filler/belt insulation | mm |
| $T_{gas}$ | Absolute gas temperature | K |
| $T_{hs}$ | Thermal resistance heat source | K.m/W |
| $t_{hsi}$ | Thickness pipe insulation | mm |
| $T_{hsi}$ | Thermal resistance pipe insulation | K.m/W |
| $t_{hsj}$ | Thickness protective jacket | mm |
| $T_{hsj}$ | Thermal resistance protective jacket | K.m/W |
| $t_{hsp}$ | Thickness fluid-filled pipe | mm |
| $T_{hsp}$ | Thermal resistance fluid-filled pipe | K.m/W |
| $T_i$ | Thermal resistance insulation | K.m/W |
| $t_i$ | Thickness insulation | mm |
| $t_{icore}$ | Thickness core insulation | mm |
| $t_{ins}$ | Thickness insulation | mm |
| $T_{ins}$ | Thermal resistance insulation | K.m/W |
| $T_{int}$ | Internal thermal resistance for current losses | K.m/W |
| $t_{is}$ | Thickness insulation screen | mm |
| $T_{is}$ | Thermal resistance insulation screen | K.m/W |
| $t_j$ | Thickness jacket | mm |
| $T_j$ | Thermal resistance jacket | K.m/W |
| $t_{jj}$ | Thickness of additional layer over jacket | mm |
| $t_k$ | Duration of short-circuit | s |
| $T_L$ | Thermal resistance, longitudinal | K.m/W |
| $T_{mh}$ | Mutual thermal resistance between rated and crossing object(s) | K.m/W |
| $T_{mh,v}$ | Mutual thermal resistance between object(s) per slice | K.m/W |
| $T_o$ | Thermal resistance oil in the pipe | K.m/W |
| $t_p$ | Thickness enclosing pipe | mm |
| $t_{prot}$ | Thickness protective cover | m |
| $T_{prot}$ | Thermal resistance protective cover | K.m/W |
| $T_r$ | Thermal resistance, total | K.m/W |
| $T_{rad,ce}$ | Thermal resistance radiation conductor—enclosure | K.m/W |
| $T_{rad,int}$ | Thermal resistance radiation cable—riser | K.m/W |
| $T_{rad,sa}$ | Thermal resistance radiation surface—air | K.m/W |
| $T_{rad,sun}$ | Thermal resistance solar radiation air—surface | K.m/W |
| $T_{riser}$ | Thermal resistance riser | K.m/W |
| $T_s$ | Star thermal resistance object | K.m/W |
| $T_{sa}$ | Thermal resistance convection object—air | K.m/W |
| $t_{sc}$ | Thickness screen | mm |
| $t_{scb}$ | Thickness screen bedding | mm |
| $T_{scb}$ | Thermal resistance screen bedding | K.m/W |
| $t_{scs}$ | Thickness screen serving | mm |
| $T_{scs}$ | Thermal resistance screen serving | K.m/W |
| $t_{sh}$ | Thickness sheath | mm |
| $t_{sha}$ | Total thickness between separate sheath and armour | mm |
| $t_{shj}$ | Thickness sheath jacket | mm |
| $T_{shj}$ | Thermal resistance sheath jacket | K.m/W |
| $t_{skid}$ | Thickness skid wires | mm |
| $t_{sp}$ | Thickness steel pipe | mm |
| $T_{spf}$ | Thermal resistance steel pipe filling | K.m/W |
| $T_{st}$ | Thermal resistance radiation object—tunnel | K.m/W |
| $T_{surf}$ | Absolute surface temperature | K |
| $t_t$ | Thickness wall | m |
| $T_t$ | Star thermal resistance tunnel | K.m/W |
| $T_{tot}$ | Thermal resistance, transient | K.m/W |
| $T_{tr}$ | Thermal resistance trough | K.m/W |
| $T_{tw}$ | Thermal resistance wall | K.m/W |
| $T_{wall}$ | Thermal resistance pipe wall | K.m/W |
| $\mathrm{tan} \delta_i$ | Loss factor insulation material | |
| $\tau$ | Transient load period | s |
| $\tau_{ar}$ | Armour angle | rad |
| $\tau_L$ | Deep burial thermal inertia transient load period | s |
| $\theta_{2K}$ | Temperature rise 2K criterion | °C |
| $\theta_a$ | Ambient temperature | °C |
| $\theta_{abs}$ | Absolute temperature | K |
| $\theta_{air}$ | Ambient air temperature | °C |
| $\theta_{ar}$ | Temperature armour | °C |
| $\theta_{at}$ | Air temperature with load | °C |
| $\theta_{at,L}$ | Air temperature at outlet | °C |
| $\theta_{at,max}$ | Air temperature permissible | °C |
| $\theta_{at,z}$ | Air temperature z | °C |
| $\theta_c$ | Temperature conductor | °C |
| $\theta_{c,t,0}$ | Temperature of conductor at transient step | °C |
| $\theta_{c,z}$ | Temperature conductor z | °C |
| $\theta_{cmax}$ | Max. temperature conductor | °C |
| $\theta_{cmaxeo}$ | Max. temperature conductor, emergency overload | °C |
| $\theta_{cmaxsc}$ | Max. temperature conductor, short-circuit | °C |
| $\theta_{cs}$ | Temperature conductor shield | °C |
| $\theta_{de}$ | Temperature duct outer surface | °C |
| $\theta_{di}$ | Temperature duct inner surface | °C |
| $\theta_{dm}$ | Mean temperature medium in the duct | °C |
| $\theta_e$ | External temperature object | °C |
| $\theta_{encl}$ | Temperature enclosure | °C |
| $\theta_f$ | Temperature filler for multi-core cables type SS with sheath | °C |
| $\theta_{film}$ | Film temperature | °C |
| $\theta_{gas}$ | Gas temperature | °C |
| $\theta_{hs}$ | Temperature heat source | °C |
| $\theta_{hsf}$ | Temperature fluid | °C |
| $\theta_{hsi}$ | Temperature pipe insulation | °C |
| $\theta_{hsj}$ | Temperature protective jacket | °C |
| $\theta_{hsp}$ | Temperature fluid-filled pipe | °C |
| $\theta_i$ | Temperature of insulation | °C |
| $\theta_{init}$ | Air temperature without load | °C |
| $\theta_{iter}$ | Air temperature previous iteration | °C |
| $\theta_{kf}$ | Final temperature | °C |
| $\theta_{ki}$ | Initial temperature | °C |
| $\theta_{kmax}$ | Maximal temperature of non-insulation material | °C |
| $\theta_{max}$ | Temperature of conductor at end of emergency loading | °C |
| $\theta_o$ | Temperature outer surface | °C |
| $\theta_{o,L}$ | Temperature object surface at outlet | °C |
| $\theta_{o,z}$ | Temperature object surface z | °C |
| $\theta_{omax}$ | Max. temperature outer surface | °C |
| $\theta_R$ | Rated current transient to steady-state ratio | |
| $\theta_s$ | Temperature screen/sheath | °C |
| $\theta_{sc}$ | Temperature screen | °C |
| $\theta_{sh}$ | Temperature sheath | °C |
| $\theta_{sp}$ | Temperature steel pipe | °C |
| $\theta_{spf}$ | Mean temperature medium in the steel pipe | °C |
| $\theta_{surf}$ | Surface temperature | °C |
| $\theta_t$ | Temperature wall (inner) | °C |
| $\theta_{t,L}$ | Temperature wall at outlet | °C |
| $\theta_{t,z}$ | Temperature wall z | °C |
| $\theta_{tm}$ | Mean temperature between surface and air in tunnel or trough | °C |
| $\theta_{to}$ | Temperature wall (outer) | °C |
| $\theta_{to,z}$ | Temperature wall (outer) z | °C |
| $\theta_w$ | Temperature water | °C |
| $\theta_x$ | Critical soil temperature | °C |
| $TQ$ | Cable thermal time constant | s |
| U | $u$ | Substitution coefficient u | |
| $U_0$ | Base voltage for tests | kV |
| $u_b$ | Substitution coefficient u | |
| $U_{buried}$ | OHTC pipe fully buried | W/(K.m$^2$) |
| $U_d$ | Constant U for cables in ducts | K.m/W |
| $U_e$ | Line-to-ground voltage | V |
| $U_{exposed}$ | OHTC part of pipe in contact with water | W/(K.m$^2$) |
| $U_{ground}$ | OHTC part of pipe in contact with ground | W/(K.m$^2$) |
| $U_{inwall}$ | OHTC inside film + pipe wall | W/(K.m$^2$) |
| $U_k$ | Induced shield voltage | V/m |
| $U_m$ | Highest voltage for equipment | kV |
| $U_n$ | Rated line-to-line voltage | kV |
| $U_o$ | Operating voltage | kV |
| $U_{OHTC}$ | Overall heat transfer coefficient | W/(K.m$^2$) |
| $u_p$ | Substitution coefficient u | |
| $U_p$ | Constant U for air-filled pipe with objects | K.m/W |
| $U_{partially}$ | OHTC pipe partially buried | W/(K.m$^2$) |
| $U_{spf}$ | Constant U pipe-type cable | K.m/W |
| $U_{sr}$ | Reference voltage shunt reactor | kV |
| $U_{ti}$ | Circumference of inner rectangular tunnel wall | m |
| $U_{wall}$ | OHTC pipe wall | W/(K.m$^2$) |
| V | $v_4$ | Ratio thermal resistivity dry/moist soil | |
| $V_{ab}$ | Voltages between shields/sheaths at the cross-bonding points phases a — b | V |
| $V_{ac}$ | Voltages between shields/sheaths at the cross-bonding points phases a — c | V |
| $V_{air}$ | Air velocity | m/s |
| $V_{air,min}$ | Air velocity required to remove all heat by ventilation | m/s |
| $V_{bc}$ | Voltages between shields/sheaths at the cross-bonding points phases b — c | V |
| $V_{comp}$ | Gas volume | m$^3$ |
| $V_d$ | Constant V for cables in ducts | K.m/W |
| $V_{drop}$ | Voltage drop | V/(A.m) |
| $V_{fluid}$ | Velocity of fluid | cm/s |
| $V_{gas}$ | Volume percentage of second gas | $\%$ |
| $V_{mol}$ | Molar volume | m$^3$/mol |
| $V_p$ | Constant V for air-filled pipe with objects | K.m/W |
| $v_{prop}$ | Velocity of propagation | km/s |
| $V_{spf}$ | Constant V pipe-type cables | K.m/W |
| $V_w$ | Velocity water | cm/s |
| W | $w_{a,1}$ | Width of flat wires armour 1 | mm |
| $w_{a,2}$ | Width of flat wires armour 2 | mm |
| $W_{a,L}$ | Heat removed by air at outlet | W/m |
| $W_{a,z}$ | Heat removed by air z | W/m |
| $W_{ar}$ | Armour losses (phase) | W/m |
| $w_{ar}$ | Width armour | mm |
| $w_b$ | Width backfill | mm |
| $w_{b4}$ | Distance to lateral edge multi-layer backfill | m |
| $W_c$ | Conductor losses (phase) | W/m |
| $W_{conv,ce}$ | Convective heat transfer conductor→enclosure | W/m |
| $W_{conv,ext}$ | Convective heat transfer riser—air | W/m |
| $W_{conv,gd}$ | Convective heat transfer gas—duct | W/m |
| $W_{conv,int}$ | Convective heat transfer cable→riser | W/m |
| $W_{conv,og}$ | Convective heat transfer cable→gas | W/m |
| $W_{conv,sa}$ | Convective heat transfer, surface→air | W/m |
| $W_d$ | Dielectric losses (phase) | W/m |
| $w_d$ | Volumetric density of dielectric losses | W/m$^3$ |
| $W_{d,DC}$ | Dielectric losses in HVDC cables | W/m |
| $W_{de}$ | Losses outside of riser | W/m |
| $W_{di}$ | Losses between cable and riser | W/m |
| $W_{duct}$ | Duct losses | W/m |
| $W_{encl}$ | Ohmic losses enclosure | W/m |
| $W_h$ | Heat generated by external object | W/m |
| $W_{hs}$ | Heat dissipation heat source | W/m |
| $W_I$ | Ohmic losses (phase) | W/m |
| $W_{rad,ce}$ | Radiation heat transfer conductor→enclosure | W/m |
| $W_{rad,ext}$ | Radiation heat transfer riser—air | W/m |
| $W_{rad,int}$ | Radiation heat transfer cable—riser | W/m |
| $W_{rad,sa}$ | Radiation heat transfer surface—air | W/m |
| $W_s$ | Screen/sheath losses (phase) | W/m |
| $W_{sar}$ | Total loss in shield and magnetic armour (phase) | W/m |
| $w_{sc}$ | Width flat screen wires | mm |
| $W_{sp}$ | Steel pipe losses (phase) | W/m |
| $W_{sum}$ | Sum of total losses of all systems | W/m |
| $W_{sun}$ | Heat transfer solar radiation air→surface | W/m |
| $W_{sys}$ | Total losses (system) | W/m |
| $W_t$ | Total losses (phase) | W/m |
| $w_t$ | Width (inner) | m |
| $W_{tot}$ | Total losses (object) | W/m |
| X | $X$ | Reactance matrix | $\Omega$/m |
| $X_1$ | Positive sequence reactance | $\Omega$/m |
| $X_a$ | Self reactance conductor | $\Omega$/m |
| $X_{ap}$ | Equivalent mutual reactance between conductors | $\Omega$/m |
| $X_{ar}$ | Self reactance armour | $\Omega$/m |
| $x_b$ | Horizontal center backfill | mm |
| $X_c$ | Mutual reactance between middle and outer cables in flat formation with earth return | $\Omega$/m |
| $X_{cp}$ | Zero-sequence reactance steel pipe | $\Omega$/m |
| $X_d$ | Reactance steel pipe | $\Omega$/m |
| $X_e$ | Self reactance screen/sheath | $\Omega$/m |
| $X_G$ | Factor $X_G$ | |
| $X_{G2}$ | Factor $X_{G2}$ | |
| $X_h$ | Reactance link | $\Omega$/m |
| $X_{ij}$ | Mutual reactance between conductors i + j | $\Omega$/m |
| $X_K$ | Factor $X_K$ | |
| $X_L$ | Mutual reactance between outer cables in flat formation | $\Omega$/m |
| $X_m$ | Mutual reactance between conductors flat formation without transposition | $\Omega$/m |
| $X_{mut}$ | Mutual reactance | $\Omega$/m |
| $x_p$ | Factor for proximity effect of conductors | |
| $x_{pos}$ | Horizontal position x multi-layer backfill | m |
| $x_s$ | Factor for skin effect on conductor | |
| $X_s$ | Self reactance screen/sheath | $\Omega$/m |
| $X_{S1}$ | Reactance section 1 | $\Omega$/m |
| $X_{S2}$ | Reactance section 2 | $\Omega$/m |
| $X_{S3}$ | Reactance section 3 | $\Omega$/m |
| $X_{sw}$ | Reactance skywire | $\Omega$/m |
| $\xi_X$ | Parameter $\xi$ calculation of loss factor | |
| Y | $Y$ | Admittance matrix | S/m |
| $Y_1$ | Positive sequence admittance | S/m |
| $y_{2K}$ | Depth 2K criterion | mm |
| $Y_{ag}$ | Admittance armour - ground | S/m |
| $y_c$ | Skin and proximity effect factor y PAC/GIL conductor | |
| $Y_{cs}$ | Admittance conductor - shield | S/m |
| $Y_d$ | Constant Y for cables in ducts | K.m/W |
| $y_{encl}$ | Skin and proximity effect factor y PAC/GIL enclosure | |
| $Y_G$ | Factor $Y_G$ | |
| $Y_i$ | Ordinates of the loss-load cycle | p.u. |
| $Y_K$ | Factor $Y_K$ | |
| $y_p$ | Proximity effect factor conductor | |
| $Y_p$ | Constant Y for air-filled pipe with objects | K.m/W |
| $y_s$ | Skin effect factor conductor | |
| $Y_{sa}$ | Admittance shield - armour | S/m |
| $Y_{sg}$ | Admittance shield - ground | S/m |
| $Y_{spf}$ | Constant Y pipe-type cables | K.m/W |
| Z | $Z$ | Impedance matrix | $\Omega$/m |
| $Z_1$ | Positive sequence impedance | $\Omega$/m |
| $Z_2$ | Negative sequence impedance | $\Omega$/m |
| $Z_a$ | Self impedance of phase conductor with earth return | $\Omega$/m |
| $Z_{as}$ | Impedance at transition overhead line to underground cable | $\Omega$/m |
| $Z_{bs}$ | Installation constant Z | |
| $Z_c$ | Mutual inductance between middle and outer cables in flat formation with earth return | $\Omega$/m |
| $Z_C$ | Surge impedance | $\Omega$ |
| $z_c$ | Factor z to calculate skin effect coefficients for conductor | |
| $Z_{ch}$ | Surge impedance | $\Omega$ |
| $Z_{ct}$ | Self impedance earth continuity conductor | $\Omega$/m |
| $Z_d$ | Positive sequence impedance | $\Omega$/m |
| $z_{encl}$ | Factor z to calculate skin effect coefficients for enclosure | |
| $z_h$ | Location of the heat source | m |
| $Z_h$ | Zero-sequence impedance | $\Omega$/m |
| $Z_{ij}$ | Mutual impedance between cables with earth return | $\Omega$/m |
| $Z_K$ | Factor $Z_K$ | |
| $Z_{kp}$ | Impedance between cable k and p in ground | $\Omega$/m |
| $Z_L$ | Mutual inductance between outer cables in flat formation with earth return | $\Omega$/m |
| $Z_m$ | Mutual impedance between phase conductor and metal screen with earth return | $\Omega$/m |
| $z_{max}$ | Logitudinal thermal limit distance | m |
| $Z_{mt}$ | Equivalent mutual impedance between earth continuity conductor and any cable | $\Omega$/m |
| $Z_{oig}$ | Mutual impedance between shields/sheaths of inner and outer cables with ground return | $\Omega$/m |
| $Z_{oog}$ | Mutual impedance between shields/sheaths of outer cables with ground return | $\Omega$/m |
| $z_r$ | Location of the hottest point | m |
| $Z_s$ | Self impedance of metal screen with earth return | $\Omega$/m |
| $Z_{sg}$ | Mutual impedance of shield/sheath with ground return | $\Omega$/m |
| $Z_{ss}$ | Self impedance of the shield/sheath with ground return | $\Omega$/m |
| $Z_{sw}$ | Self impedance skywire | $\Omega$/m |
| $Z_x$ | Equivalent mutual impedance between cables with earth return | $\Omega$/m |
| $\zeta_{ab}$ | Density armour bedding material | g/cm$^3$ |
| $\zeta_{ar}$ | Density armour material | g/cm$^3$ |
| $\zeta_c$ | Density conductor material | g/cm$^3$ |
| $\zeta_{er}$ | Radiation shape factor touching cables | |
| $\zeta_f$ | Density filler material | g/cm$^3$ |
| $\zeta_i$ | Density insulation material | g/cm$^3$ |
| $\zeta_j$ | Density jacket material | g/cm$^3$ |
| $\zeta_M$ | Density cable material | g/cm$^3$ |
| $\zeta_{sc}$ | Density metallic screen material | g/cm$^3$ |
| $\zeta_{sh}$ | Density sheath material | g/cm$^3$ |
| $\zeta_{shj}$ | Density of jacket material over each core | g/cm$^3$ |
| $\zeta_{skid}$ | Density skid wire material | g/cm$^3$ |
| $\zeta_{soil}$ | Density soil material | kg/m$^3$ |
| $\zeta_{sp}$ | Density steel pipe material | g/cm$^3$ |
| $\zeta_{tape}$ | Density tape material | g/cm$^3$ |
| $\zeta_w$ | Density water | kg/m$^3$ |
| $\mathscr{z}_1$ | Impedance conductor outer surface | $\Omega$/m |
| $\mathscr{z}_2$ | Impedance insulation conductor—screen | $\Omega$/m |
| $\mathscr{z}_3$ | Impedance shield inner surface | $\Omega$/m |
| $\mathscr{z}_{34}$ | Impedance insulation shield—armour | $\Omega$/m |
| $\mathscr{z}_{3,s}$ | Impedance shield inner surface | $\Omega$/m |
| $\mathscr{z}_{3,sc}$ | Impedance screen inner surface | $\Omega$/m |
| $\mathscr{z}_{3,sh}$ | Impedance sheath inner surface | $\Omega$/m |
| $\mathscr{z}_4$ | Mutual impedance shield | $\Omega$/m |
| $\mathscr{z}_{4,s}$ | Mutual impedance shield | $\Omega$/m |
| $\mathscr{z}_{4,sc}$ | Mutual impedance screen | $\Omega$/m |
| $\mathscr{z}_{4,sh}$ | Mutual impedance sheath | $\Omega$/m |
| $\mathscr{z}_5$ | Impedance shield outer surface | $\Omega$/m |
| $\mathscr{z}_{56}$ | Impedance jacket | $\Omega$/m |
| $\mathscr{z}_{5,s}$ | Impedance shield outer surface | $\Omega$/m |
| $\mathscr{z}_{5,sc}$ | Impedance screen outer surface | $\Omega$/m |
| $\mathscr{z}_{5,sh}$ | Impedance sheath outer surface | $\Omega$/m |
| $\mathscr{z}_6$ | Impedance insulation screen—sheath | $\Omega$/m |
| $\mathscr{z}_{cc}$ | Impedance conductor | $\Omega$/m |
| $\mathscr{z}_{cs}$ | Impedance conductor—screen | $\Omega$/m |
| $\mathscr{z}_g$ | Impedance earth return in ground | $\Omega$/m |
| $\mathscr{z}_{gm}$ | Impedance mutual earth return in ground | $\Omega$/m |
| $\mathscr{z}_{int}$ | Impedance cable, internal | $\Omega$/m |
| $\mathscr{z}_{os}$ | Impedance outersheath | $\Omega$/m |
| $\mathscr{z}_{pin}$ | Impedance armour inner surface | $\Omega$/m |
| $\mathscr{z}_{pmut}$ | Mutual impedance armour | $\Omega$/m |
| $\mathscr{z}_{pout}$ | Impedance armour outer surface | $\Omega$/m |
| $\mathscr{z}_{ss}$ | Impedance cable, external | $\Omega$/m |
