project scenario 1 · top layer resistivity (ohm.m) 39.525 top layer depth (m) 15.735 bottom layer...
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Project:ProjectScenario:Scenario 1 Design Inputs
Refer to separate page for LM-RES soil modelling.
Table1 Soil characteristics
Model Determine values using soil modellingprogram (S-RES)
Top layer resistivity (Ohm.m) 39.525Top layer depth (m) 15.735Bottom layer resistivity (Ohm.m) 7865.432
Table2 Grid energisation
Source Determine using fault current distributionprogram (EFCD)
Units Current (A)Magnitude (real) 40Magnitude (imag) -9
Table3 Grid and rod conductor size
Method Specify grid conductor radiusConductor radius (mm) 4.72
Table4 Measurement units
Units Metric
Table5 System
Frequency (Hz) 50
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Fault Current Distribution
Table6 User Inputs
Calculations mode Standard cases
Case description CASE 1 - Two subs., Cables SC, Solidbonded, Local 1ph-e fault
Fault current (A) 1000 +0 iLength (m) 1000 +0 iSoil electrical resistivity (Ohm.m) 100 +0 iEarth grid (local) resistance (Ohm) 1 +0 iEarth grid (remote) resistance (Ohm) 1 +0 iCond. A position, Z (m) 0.5Cond. A position, Y (m) 0Cond. B position, Z (m) 0.5Cond. B position, Y (m) 0.5Cond. C position, Z (m) 0.5Cond. C position, Y (m) 1Phase cond. diameter (mm) 11.5Phase cond. a.c. resistance (Ohm/km) 0.247Screen outer diameter (mm) 22.7Screen thickness (mm) 0.85Screen a.c. resistance (Ohm/km) 0.265
Figure1 CASE 1 - Two subs., Cables SC, Solid bonded, Local 1ph-e fault
Table7 Results: Fault currents
Element Name [start, end node no.] Fault current (A)PHASE CONDUCTOR (FAULTED) [1, 4] -1000 -0 i (100 %)SCREEN 1 [2, 5] 656 +334 i (74 %)SCREEN 2 [2, 5] 181 -161 i (24 %)
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Element Name [start, end node no.] Fault current (A)SCREEN 3 [2, 5] 123 -165 i (21 %)FICTICIOUS EARTH RETURN [3, 6] 40 -9 i (4 %)EG LOCAL [2, 3] 40 -9 i (4 %)EG REMOTE [5, 6] -40 +9 i (4 %)SHORT-CCT [1, 2] 1000 +0 i (100 %)
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Levenberg-Marquardt Soil Resistivity (LM-RES) Modelling
Table8 User Inputs
Soil model Horizontal 2-LayerMeasurement method WennerMeasurement values Resistivity (Ohm.m)Account for probe depth? (True/False) FALSEDriven depth at short spacings (m) -Remove outliers? (True/False) FALSE
Table9 Field measurements
Spacing (m) Resistivity (Ohm.m) Included?(True/False)
R1 0.5 73.7 FALSER2 1 47.9 TRUER3 2 45.2 TRUER4 3 42.8 TRUER5 4 41.9 TRUER6 5 40.9 TRUER7 6 39.2 TRUER8 7 37.7 TRUER9 8 38.6 TRUER10 9 40.1 TRUER11 10 42.5 TRUER12 15 46.1 TRUER13 20 82.1 TRUE
Table10 Results
Top layer soil resistivity (Ohm.m) 39.525Top layer depth (m) 15.735
Bottom layer soil resistivity (Ohm.m) 7865.432Reflection factor, k 0.99
Goodness of Fit (R-square) 6.574
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Figure2 Non-linear model fit to field measurements
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Buried Grid Model
Table11 Segments
No. of segments accounting forintersections only 228
No. of segments after segmentation (foraccuracy) 228
Fault location (segment no.) 1Total length of conductor network (m) 1661.839
Figure3 Buried grid preview
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Safety Criteria Calculation
Table12 User Inputs
Safety standard (body resistance) IECFibrillation current method C1 - IECBody resistance curve (IEC) 95% of population exceeds curveConditions (IEC) DryFoot resistance calculation method IEEE80:2000Additional series resistance (i.e. shoe orglove) (Ohms) 0
Fault clearing time (s) 0.5System frequency (Hz) 50System X/R ratio 20Decrement factor DefaultDecrement factor value 1.062
Sub-surface layer resistivity (Ohm.m) 100Use top layer soil resistivity? (True/False) TRUESurface material resistivity (Ohm.m) 500Surface layer depth (m) 0.18
Table13 Results
Allowable Touch Voltage Limit (V) 200.069Allowable Step Voltage Limit (V) 430.535Permissible body current (A) 0.098Body resistance - 1 hand to both feet(Ohms) 2076.378
Body resistance - 1 foot to other foot(Ohms) 2076.378
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Earthing System Performance
Table14 Results
Grid Impedance, Z (Ohms) 1.813Grid Impedance Angle (degrees) 0.096Grid Potential Rise, GPR (V) 74.616Grid Potential Rise Angle (degrees) -12.376
Table15 Summary of Inputs
Top soil layer resistivity (Ohm.m) 39.52Depth top soil layer (m) 15.73Bottom soil layer resistivity (Ohm.m) 7865.43Excitation current (A) 40.18-j8.886576Faulted segment no. 1Final no. of segments 228Conductor radius (m) 0.00472Conductivity of buried conductor (S/m) 57E+6Frequency (Hz) 50Calculation delta 0.001
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Figure4 Surface potentials (V) - 3D view
Figure5 Surface potentials (V) - 2D view
Figure6 Touch potentials (V) - 3D view
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Figure7 Touch potentials (V) - 2D view
Figure8 Step potentials (V) - 3D view
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Figure9 Step potentials (V) - 2D view
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