Symbols

Last updated on 2019-04-15 1 mins. to read

Comments

Add comment

Symbols - Cable Construction

Last updated on 2019-04-15 3 mins. to read
CSA, S cross-sectional area of conductor, mm2
 CSAa cross-sectional area of armour, mm2
 ds conductor screen diameter, m 
 dsc  conductor semi-conducting layer diameter, m
 D, d  overall diameter of cable, m
 Da  armour diameter, m
 Db  bedding diameter, m
 Df cable laid up diameter (multicore), m 
 Di  insulation diameter, m 
 Dls  laid up screen diameter, m 
 Ds  insulation screen diameter, m
 Dsc  insulation semiconducting screen diameter, m
 dL  diameter of conductor, m
 maxT  maximum cable tension, N
 swP  maximum sidewall pressure, kg.m-1
 ti  thickness of armour, m
 ts  conductor screen thickness, m
 tsc  conductor semi-conducting layer thickness, m
 Ta  armour thickness, m
 Tb  bedding thickness, m
 Tis  laid up screen thickness, m
 Tos  sheath thickness, m
 Ts  insulation screen thickness, m
 Tsc  insulation semi-conducting screen thickness, m 
 Ti thickness of the insulation, m
 Tos  thickness of over sheath, m
 Wt  weight of cable kg.m-1

Comments

Add comment

Symbols - Cable Derating Factors

Last updated on 2019-04-15 2 mins. to read
Ca for ambient temperature
Cc for circuits buried in the ground
Cd for depth of burial
Cf for semi-enclosed fuse to BS 3036
Cg for grouping
Ci for thermal insulation
 Cs for thermal resistivity of soil
 Cu user defined derating factor

Comments

Add comment

Symbols - Cables

Last updated on 2019-04-15 9 mins. to read
 b circuit factor (=2 for d.c. and single phase, = 1 for three phase) 
C cable capacitance [ F, μF, F.m-1]
dc diameter of conductor, m
ds mean diameter of sheath, m
I2  operating or tripping current of the protective device, A
Ib cable design conductor current, A 
Ic cable charging current [A, A.m-1]
In   rated current or current setting of the protective device, A
I1, I2, I3 conductor phase current of L1, L2 and L3, A
Is1, Is2, Is3 sheath phase current of L1, L2 and L3, A
It  tabulated current rating for a particular installation condition, A
Iz sustained current rating of cable under particular installation conditions, A 
L cable inductance [H, mH, mH.m-1]
Ls inductance of sheath, H.m-1
n number of circuit in a group 
R cable resistance [Ω, Ω.m-1]
 R20  resistance of conductor at 20 °C
Rac a.c. resistance of cable, Ω.m-1
Rarmour resistance of armour, Ω.m-1
Rdc d.c. resistance of cable, Ω.m-1
Rs resistance of the sheath, Ω.m-1
 Rt resistance of conductor at t °C
S distance between cable centres, m
S12 distance of cable centres between L1 and L2, m
S23 distance of cable centres between L2 and L3, m
S31 distance of cable centres between L3and L1, m
 t conductor [cable]  temperature, °C
 Ta ambient temperature, °C 
 Tc conductor [insulation] limiting/design temperature, °C 
X cable reactance, general [Ω, Ω.m-1]
Xc cable capacitive reactance [Ω, Ω.m-1]
XL cable inductive reactance [Ω, Ω.m-1]
X1, X3, Xa, Xb reactance formulas; sheath induced voltage, Ω.m-1
Xm mutual reactance between conductor and sheath, Ω/unit length
Xs sheath reactance, Ω.m-1
Uo   nominal voltage, V
Us sheath voltage, V
U1, U2, U3 phase voltage o f L1, L2 and L3, V
Us1, Us2, Us3 sheath inductive phase voltage o f L1, L2 and L3, V
Z cable impedance [Ω, Ω.m-1]
 ΔU voltage drop,
ϵo permittivity of free space = 8.854187819x10-12 F/m
ϵr relative permittivity of a dielectric

Comments

Add comment

Symbols - Circuit Breakers

Last updated on 2019-04-15 1 mins. to read
Icm short-circuit breaking or making capacity [kA]
Ics serviceshort-circuit breaking capacity [kA]
Icu ultimate short-circuit breaking capacity [kA]
Icw rated short-time withstand current [kA]

Comments

Add comment

Symbols - Fault Calculations

Last updated on 2019-04-15 2 mins. to read
 C  voltage factor (IEC 60909)
 If  required through fault rating [kA]
 Ik

 steady state fault level [kA]
   Ik or Ik3                 - three phase fault
   Ik1                        - phase to earth (or phase to neutral) fault
   Ik2                        - phase to phase fault
   Ik2E or IkE2E          - phase to phase to earth fault
 I''k  initial symmetrical fault current kA
  I''k , I''k2 , I''k1 , I''k2 , I''k2E , I''kE2E        - as above
Irm  rated current of any motor A
 Isc min  minimum fault level [kA]
 Isc max  maximum fault level [kA]
 k  adiabatic equation factor
 pu

 per unit quantities
  Ibase         - per unit current base
  Pbase        - per unit power base
  Vbase        - per unit voltage base
  Ybase        - per unit admittance base
  Zbase        - per unit impedance base
  Zpu          - per unit impedance
  Z%          - per unit percentage impedance
 1,2, 3  symmetrical components
    Ua , Ub , Uc     - system voltages [V]
    U1 , U2 , U3     - symmetrical voltages [V]
    Z(1)                 - positive sequence impedance [Ω]
    Z(2)                 - negative sequence impedance [Ω]
    Z(0)                 - zero sequence impedance (Ω)
 t  earth fault duration [s]
 Z0  earth fault impedance [Ω]
 Zs  earth fault loop impedance [Ω]

 

Comments

Add comment

Symbols - General

Last updated on 2019-04-15 4 mins. to read
 C  capacitance [ F, μF]
 Cmin  minimim voltage factor ( = 0.95 )
 f  frequency [Hz]
 Ia  current causing operation of device in specified time, A
 In  nominal current [A]
 IΔn  rated current of an RCD, A
 L  inductance [ H, mH]
 R  resistance [Ω]
 RA  sum of resistance of earth electrode and protective condcutor, Ω 
 ULL , or VLL  line to line voltage [V, kV]
 ULN or VLN  line to neutral voltage [V, kV]
 Uo or Vo   nominal line to neutral voltage [V, kV]
 UN or VN  nominal  line to line voltage [V, kV]
 X  reactance, general [Ω]
 Xc  capacitive reactance [Ω]
 XL  inductive reactance [Ω]
 Z  impedance [Ω, Ω.m-1]
 Z1  line conductor impedance, Ω
 Z2  circuit protective conductor (CPC)  impedance, Ω 
 Ze  external earth fault impedance, Ω
 Zs  earth fault look impedance, Ω
 ω  angular frequency = 2πf, s-1

Comments

Add comment

Symbols - Materials

Last updated on 2019-04-15 2 mins. to read
 k  factor used in the adiabatic equation and dependant on cable type
 Qc  volumetric heat capacity of conductor at 20°C, J.K-1.mm-3
 α20  temperature coefficient of resistance of material at 20 °C
ß reciprocal of temperature coefficient of resistivity at 0 °C 
ρ20
  electrical resistivity of conductor material at 20 °C, Ω.m
ϴi  initial temperature of conductor, °C
ϴf final temperature of conductor, °C 

Comments

Add comment