Substation Grounding Design

Substation Grounding Design

Substation Grounding Design before the constructing is essential because it is very dangerous without doing it. For more visit here.

* When possible, substations vicinity a layer of pretty resistive cloth such
as beaten rock.
• The addition of a floor layer modifications the floor resistance, Rf.
• The new floor resistance becomes:

ground resistance Substation Grounding Design
ground resistance

Where,
p = resistivity of the earth(Ωm)
ps = resistivity of floor layer material(Ωm)
hs = thickness of floor material(m)
Assuming the extra conservative physique weight of 50 kg to decide the permissible physique contemporary and a physique resistance of one thousand Ω,

the tolerable   touch voltage is

touch voltage Substation Grounding Design
touch voltage

the tolerable step voltage is

step voltage Substation Grounding Design
step voltage

Grid Current
In practice, single-line-to-ground and line-to line- to-ground faults will produce the most grid current.
• Fault inside nearby substation,
– nearby impartial grounded
– impartial grounded at far off location
– device grounded at nearby station and at different points

Local neutral grounded and Fault within local substations – substation

Fault within local substation and local neutral grounded
Fault within local substation and the local neutral grounded

Neutral grounded and Fault within local substation and at the remote location

Fault within local substation and neutral grounded at the remote location
Fault within local substation and the neutral grounded at the remote location

ystem grounded at local station and also at other points and Fault in the substation

Fault in substation the system grounded at local station and also at other points
Fault in the substation system grounded at local station and also at other points

Conductor Sizing of Substation Grounding Design

The short-time temperature rises in a floor conductor, or the required conductor measurement as a
function of conductor current, can be bought from

Conductor Sizing Substation Grounding Design
Conductor Sizing

Where,

  1. I – rms current, kA
  2. A – conductor cross section, mm2
  3. Tm is maximum allowable temperature, 0C
  4. Ta is ambient temperature, 0
  5. a0– thermal coefficient of resistivity at 0 0 C ,1/0C
  6. ar– thermal coefficient of resistivity at reference temperature ,1/0C        
  7. ρr – resistivity of the ground conductor at reference temperature, mΩ -cm
  8. k0 – 1/α0 or (1/αr) −Tr ,0C
  9. t0 – duration of current, sec
  10. TCAP – Thermal Capacity per unit volume, 1/(cm3.0C)
  11. Tt – reference temperature for material constants, 0C

Resistance Due to Earth Mesh 

Using Sverak’s approximation,

Resistance Due to Earth Mesh
Resistance Due to Earth Mesh

Where,

ρ – is the soil resistivity in Ωm

A – is the area occupied by a ground grid in units of m2

h – is the depth of the grid in unit of m

Mesh Voltage (Em ) of Substation Grounding Design

The real mesh voltage, Em (maximum contact voltage), is the product of
– the soil resistivity,
– the geometrical thing based totally on the configuration of the grid, Km;
– a correction factor, Ki,
which money owed for some of the blunders delivered via the assumptions made in deriving Km; and
– the common modern-day per unit of nice buried size of the conductor that makes up the grounding machine (IG/LM)

 correction factor Substation Grounding Design
correction factor

The geometrical issue due to primarily based on the configuration

geometrical factor Substation Grounding Design
geometrical factor
geometrical factor Substation Grounding Design
geometrical factor

h0 = 1 m (grid reference depth)

correction factor

Ki = 0.644 + 0.148n

The effective buried length,

LM= LC +LR

 LR – total length of all of the ground rods

For grids with floor rods in the corners, as properly as alongside the perimeter and during the grid, the nice buried length,

geometrical factor Substation Grounding Design
geometrical factor

na – 1 for square grids

nc– 1 for square and rectangular grids

nd – 1 for square,L-shaped gridand rectangular

Otherwise,

geometrical factor Substation Grounding Design
geometrical factor

Where,

 Lc – total length of the conductor in the horizontal grid unit ofm

 Lp – peripheral length of the grid unit ofm

A – area of the grid unit of m2

Lx – maximum length of the grid in the x direction unit of m

Ly – maximum length of the grid in the y direction unit of m

Dm – maximum distance between any two points on the grid unit of m

D – spacing between parallel conductors unit of m

h – depth of the ground grid conductors unit of m

d – diameter of the grid conductor unit of m

IG – maximum grid current unit of A

Step Voltage (Es) of Substation Grounding Design

  • * The most step voltage is assumed to manifest over a distance of 1 m, commencing at and extending outdoor of the perimeter conductor at the attitude bisecting the most excessive nook of the grid.

Step voltage is a product of

– the soil resistivity,

– The Geometrical factor Ks,

– the corrective factor Ki, and

– the average current per unit of buried length of grounding system conductor (IG/LS)

corrective factor Substation Grounding Design
corrective factor

the effective buried conductor length, LS, is defined as,

Ls = 0.75Lc + 0.85Lr

Substation Grounding Design
corrective factor

Substation Grounding Design Steps

Design Steps Substation Grounding Design
Design Steps
Design Steps Substation Grounding Design
Design Steps

Substation Grounding Design before the constructing is essential because it is very dangerous without doing it. For more visit here.

substation details

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