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# RELAYS 101

### Relay Test Set Values From S.E.L. 'One-Bus'

The routine takes your input data of secondary values for Z1, Z0, RF, Line Distance (in Percent of Line) and Source Z (also in Percent of Line). The output values are the 3-phase voltage and current magnitudes and angles that you can then use on your 3-phase relay test set to simulate fault pick-up in your SEL distance relay. Note that the calculations are limited to one-source, one-bus and one-line. Note that the RF (fault resistance) value is only used internally in the phase-ground fault calculation. Note that the output gives voltage and current values for A-G and a B-C faults only. Note that a higher value for the Source Impedance represents a weaker source (that is a higher voltage drop before the calculated local bus); where a zero value for the Source Z means full voltage at the local bus.

##### Given: Source Z Angle = Line Z Angle / One Source, One Bus, One Line / Source Volts = 67v L-N

Enter Line Impedance Secondary Ohms and Distance Values to Compute Relay Test Set Values

Enter 100% Line Z R1 component: Enter 100% Line Z X1 component:

Enter 100% Line Z R0 component: Enter 100% Line Z X0 component:

Enter Fault Resistance RF component: (Used internally for Ground Fault Calculation Only)

Enter Source Impedance (PU of Line): (Higher number represents weaker source. 0 = Infinite Source)

Enter Distance Bus to Fault (PU of Line): (1.0 = 100% of protected line)

Choose Fault Type A-G Fault B-C Fault

VA Magnitude: VA Angle:

VB Magnitude: VB Angle:

VC Magnitude: VC Angle:

IA Magnitude: IA Angle:

IB Magnitude: IB Angle:

IC Magnitude: IC Angle:

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