Index

# RELAYS 101

### Apparent Impedance

This is a culmination of topics learned. You might call it a Final Test. Everything needed to calculate the various apparent Z values has been shown prior to this aplet. For example calculating phase-to-phase values, "K0", Neutral Current and adding phasors. And of course OHM's Law. Z = V/I (general). Zp-g = Vp/(Ip+K0IN) (Fault Z for a phase-ground fault). And Zp-p = Vp-p/Ip-p (Fault Z for a phase-phase fault). To operate - enter the phase voltage and current values and line Z values then click calculate. Calculations assume phase sequence of A-B-C. A-phase impedance values and plot points are colored "black" and are read-only. B-phase impedance values and plot points are colored "red" and are read-only. C-phase impedance values and plot points are colored "blue" and are read-only. Values for Reach and MTA (on the R-X Diagram) are the values for Z1 magnitude and angle are colored "green" and are read-only. Remember to adjust your Z0 values (if needed) when you adjust your Z1 values (Reach and MTA). Doing so will ensure that your ratios stay the same. Or you can just put in the correct Z0 and Z1 values (your Reach and MTA are now set) then you can zoom in or out. Z0 and Z1 values absolutely affect the values of ZAG, ZBG and ZCG. Experimentation on the app will confirm. Using the zoom only adjusts the scale on the canvas, it doesn't change Impedance values. Intermediate calculations are gathered at the bottom of the form and are read-only.

##### Apparent Impedance Plot (R-X Diagram)

VA Magnitude: VA angle: IA magnitude: IA angle:

VB magnitude: VB angle: IB magnitude: IB angle:

VC magnitude: VC angle: IC magnitude: IC angle:

Z0 magnitude: Z0 angle: Z1 magnitude: Z1 angle:

Zoom Value

##### Calculated Apparent Impedance

ZAG magnitude: ZAG angle: ZAB magnitude: ZAB angle:

ZBG magnitude: ZBG angle: ZBC magnitude: ZBC angle:

ZCG magnitude: ZCG angle: ZCA magnitude: ZCA angle:

##### Intermediate Calculations

Neutral Current Magnitude: Neutral Current Angle:

K0 magnitude: K0 angle: K0IN magnitude: K0IN angle:

VAB magnitude: VAB angle: IAB magnitude: IAB angle:

VBC magnitude: VBC angle: IBC magnitude: IBC angle:

VCA magnitude: VCA angle: ICA magnitude: ICA angle:

IA+K0IN magnitude: IA+K0IN angle:

IB+K0IN magnitude: IB+K0IN angle:

IC+K0IN magnitude: IC+K0IN angle:

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