Useful Tables

Last updated on 2023-03-31 1 mins. to read

Comments

Add comment

Elctrical Resistivities & Temperature Coefficients

Last updated on 2023-03-31 1 mins. to read

The following table is taken from IEC 60287-1-1:2006 and other sources:

[mceToken,materials]

 

Comments

Add comment
Ei Le Dec 12, 2018 6:45 PM
Correct that resistivity in given table is the DC resistivity in https://mycableengineering.com/knowledge-base/conductor-resistance ?

Should it be Ω/m as resistivity is proportional to length?  

How to calculate α20 when temperature in cable is changing? Possible to assumed it's constant in temperature range og 20-90 degrees celcius?
Reply
Steven McFadyen Dec 12, 2018 7:35 PM
The values are the ones you should use for d.c. resistivity and the units are Ω.m.  

For 20 to 90°C, normally people would assume α is constant.  Using a more accurate value is probably not going to make much difference (unless you are doing laboratory type experiments).

If you are interested in how α varies with temperature, an Internet search will give more information.
Reply
Ei Le Dec 12, 2018 7:52 PM
Great, thank you!
Reply

Metric AWG Conversion

Last updated on 2023-03-31 9 mins. to read

Definitions

 

  • Circ.Mils - cross sectional area in Circular Mils
  • Awg  - American Wire Gauge size
  • mm² - Metric Wire Size mm²

Conversion Table

      Number strands/diameter
per strand		 Approximate overall
diameter
mm² Awg Circ.Mils inch mm inch mm
0.5   987 1/.032 1/.813 0.032 0.81
  20 1020 7/.0121 7/.307 0.036 0.91
0.75   1480 1/.039 1/.991 0.039 0.99
  18 1620 1/.0403 1/1.02 0.04 1.02
  18 1620 7/.0152 7/.386 0.046 1.16
1   1974 1/.045 1/1.14 0.045 1.14
1   1974 7/.017 7/.432 0.051 1.3
  16 2580 1/.0508 1/1.29 0.051 1.29
  16 2580 7/.0192 7/.488 0.058 1.46
1.5   2960 1/.055 1/1.40 0.055 1.4
1.5   2960 7/.021 7/.533 0.063 1.6
  14 4110 1/.0641 1/1.63 0.064 1.63
  14 4110 7/.0242 7/.615 0.073 1.84
2.5   4934 1/.071 1/1.80 0.071 1.8
2.5   4934 7/.027 7/.686 0.081 2.06
  12 6530 1/.0808 1/2.05 0.081 2.05
  12 6530 7/.0305 7/.775 0.092 2.32
4   7894 1/.089 1/2.26 0.089 2.26
4   7894 7/.034 7/.864 0.102 2.59
  10 10380 1/.1019 1/2.59 0.102 2.59
  10 10380 7/.0385 7/.978 0.116 2.93
6   11840 1/.109 1/2.77 0.109 2.77
6   11840 7/.042 7/1.07 0.126 3.21
  9 13090 1/.1144 1/2.91 0.1144 2.91
  9 13090 7/.0432 7/1.10 0.13 3.3
  8 16510 1/.1285 1/3.26 0.128 3.26
  8 16510 7/.0486 7/1.23 0.146 3.7
10   19740 1/.141 1/3.58 0.141 3.58
10   19740 7/.054 7/1.37 0.162 4.12
  7 20820 1/.1443 1/3.67 0.144 3.67
  7 20820 7/.0545 7/1.38 0.164 4.15
  6 26240 1/.162 1/4.11 0.162 4.11
  6 26240 7/.0612 7/1.55 0.184 4.66
16   31580 7/.068 7/1.73 0.204 5.18
  5 33090 7/.0688 7/1.75 0.206 5.24
  4 41740 7/.0772 7/1.96 0.232 5.88
25   49340 7/.085 7/2.16 0.255 6.48
25   49340 19/.052 19/1.32 0.26 6.6
  3 52620 7/.0867 7/2.20 0.26 6.61
  2 66360 7/.0974 7/2.47 0.292 7.42
35   69070 7/.100 7/2.54 0.3 7.62
35   69070 19/.061 19/1.55 0.305 7.75
  1 83690 19/.0664 19/1.69 0.332 9.43
50   98680 19/.073 19/1.85 0.365 9.27
  1/0 105600 19/.0745 19/1.89 0.373 9.46
  2/0 133100 19/.0837 19/2.13 0.419 10.6
70   138100 19/.086 19/2.18 0.43 10.9
  3/0 167800 19/.094 19/2.39 0.47 11.9
  3/0 167800 37/.0673 37/1.71 0.471 12
95   187500 19/.101 19/2.57 0.505 12.8
95   187500 37/.072 37/1.83 0.504 12.8
  4/0 211600 19/.1055 19/2.68 0.528 13.4
120   238 MCM 37/.081 37/2.06 0.567 14.4
    250 MCM 37/.0822 37/2.09 0.575 14.6
150   300 MCM 37/.090 37/2.29 0.63 16
    350 MCM 37/.0973 37/2.47 0.681 17.3
185   365 MCM 37/.100 37/2.54 0.7 17.8
    400 MCM 37/.104 37/2.64 0.728 18.5
240   474 MCM 37/.114 37/2.90 0.798 20.3
240   474 MCM 61/.089 61/2.26 0.801 20.3
    500 MCM 37/.1162 37/2.95 0.813 20.7
    500 MCM 61/.0905 61/2.30 0.814 20.7
300   592 MCM 61/.099 61/2.51 0.891 22.6
    600 MCM 61/.0992 61/2.52 0.893 22.7
    700 MCM 61/.1071 61/2.72 0.964 24.5
    750 MCM 61/.1109 61/2.82 0.998 25.4
    750 MCM 91/.0908 91/2.31 0.999 25.4
400   789 MCM 61/.114 61/2.90 1.026 26.1
    800 MCM 61/.1145 61/2.91 1.031 26.2
    800 MCM 61/.0938 91/2.38 1.032 26.2
500   1000 MCM 61/.1280 61/3.25 1.152 29.3
    1000 MCM 91/.1048 91/2.66 1.153 29.3
625   1234 MCM 91/.117 91/2.97 1.287 32.7
    1250 MCM 91/.1172 91/2.98 1.289 32.7
    1250 MCM 127/.0992 127/2.52 1.29 32.8
    1500 MCM 91/.1284 91/3.26 1.412 35.9
    1500 MCM 127/.1087 127/2.76 1.413 35.9
800   1579 MCM 91/.132 91/3.35 1.452 36.9
1000   1974 MCM 91/.147 91/3.73 1.617 41.1
    2000 MCM 127/.1255 127/3.19 1.632 41.5
    2000 MCM 169/.1088 169/2.76 1.632 41.5

Comments

Add comment

Standard Wire and Cable Sizes

Last updated on 2023-03-31 1 mins. to read

 

IEC 60228 is the International Electrotechnical Commission's international standard on conductors of insulated cables.   Among other things, it defines a set of standard wire cross-sections:

International standard wire sizes (IEC 60228)
0.5 mm² 0.75 mm² 1 mm² 1.5 mm² 2.5 mm² 4 mm²
6 mm² 10 mm² 16 mm² 25 mm² 35 mm² 50 mm²
70 mm² 95 mm² 120 mm² 150 mm² 185 mm² 240 mm²
300 mm² 400 mm² 500 mm² 630 mm² 800 mm² 1000 mm²

Comments

Add comment

Typical Environmental Conditions, by Country

Last updated on 2023-03-31 1 mins. to read

{mceSQLTable, [Select Top 1 'Country', 'Soil Thermal Resistivity K.m/W', 'Ground Ambient Temperature, °C', 'Air Ambient Temperature, °C', ''] [SELECT Country AS Country, SoilThermalResistivity AS SoilThermalResistivity, GroundAmbientTemperature AS GroundAmbientTemperature, AirAmbientTemperature as AirAmbientTemperature, '/mce/mceMainApp/assets/images/flags/' + Flag AS FlagURL FROM Country WHERE Country not like '%_other%' ORDER BY Country][table table-hover][][][FlagURL][img img-responsive]}

Comments

Add comment

Symbols

Last updated on 2023-03-31 1 mins. to read

Comments

Add comment

Symbols - Cable Construction

Last updated on 2023-03-31 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 2023-03-31 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 2023-03-31 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 2023-03-31 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 2023-03-31 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 2023-03-31 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 2023-03-31 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