Overhead Line Impedance Calculator

Phase conductor data

load(RpadBaseFile("AA_conductors.RData"))
HTMLon()
HTMLselect("phaseConductors", a$label)
phase A phase B phase C

X:

feet
Y: feet

Neutral conductor data

    HTMLon()
    HTMLselect("neutralConductor", a$label)

X:

feet
Y: feet

Other parameters

Earth resistivity ohm-m

Conductor temperature degC

aa = a[a$label==phaseConductors,]
aa.n = a[a$label==neutralConductor,]

gmd = (sqrt((xA-xB)^2 + (yA-yB)^2)*
       sqrt((xB-xC)^2 + (yB-yC)^2)*
       sqrt((xC-xA)^2 + (yC-yA)^2))^(1/3)
gmd.pn = (sqrt((xA-xN)^2 + (yA-yN)^2)*
          sqrt((xB-xN)^2 + (yB-yN)^2)*
          sqrt((xC-xN)^2 + (yC-yN)^2))^(1/3)
r = aa$rac*(1+0.00404*(condT-25))
r.n = aa.n$rac*(1+0.00404*(condT-25))

z1 = r/5.28 + 1i*.0529*log10(gmd/aa$gmr)
znn = r.n/5.28 + .01807 +
      1i*.0529*log10(278.9*sqrt(rho)/aa.n$gmr)
zpn = .01807 + 1i*.0529*log10(278.9*sqrt(rho)/gmd.pn)
z0 = r/5.28 + 3*.01807 +
     1i*3*.0529*log10(278.9*sqrt(rho)/(aa$gmr*gmd^2)^(1./3)) -
     3*zpn^2/znn;
zg = (2*z1+z0)/3

HTMLon()
HTMLh2("Results")
cat(" ")
HTMLh4("Positive-sequence impedance:")
cat("Z1 =",z1,"ohms/1000 feet")
HTMLh4("Zero-sequence impedance:")
cat("Z0 =",z0,"ohms/1000 feet")
HTMLh4("Loop impedance (the impedance to line-to-ground faults):")
cat("Zs =",zg,"ohms/1000 feet")



by Tom Short, tshort@epri.com, Copyright 2005. EPRI, license: GNU GPL v2 or greater