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For a forward fault:

DV is a decrease in voltage, so it is in the negative sense. DI is a forward current flow, so it is in the positive sense.

Where DI and DV are approximately in anti-phase, the fault is forward. The exact angle relationship for the forward

fault is:

V /

I = - (Source impedance Zs)

For a reverse fault

DV is a decrease in voltage, so it is in the negative sense. DI is an outfeed flowing in the reverse direction, so it is in

the negative sense. Where DI and DV are approximately in phase, the fault is reverse. The exact angle relationship

for the reverse fault is:

V /

I = (Remote Source impedance Zs’ + ZL)

where ZL is the protected line impedance and Zs’ source impedance behind the protection.

A directional characteristic angle (RCA) setting (Dir. Char Angle) allows you to set the centre of the directional

characteristic according to the amount by which the current nominally lags the reference DV. The characteristic

boundary is then +/- 90° either side of the set characteristic angle.

Note:

If Delta directional aided scheme are not used, Distance zone directionalizing uses fixed operating thresholds:

V=0.5V and

I=5%In. If the fault

V is below the setting of 0.5V, a conventional distance line ensures correct forward/reverse polarizing.

For Delta directional aided schemes, sufficient

V must be present for tripping to occur.

The delta directional element will produce a forward decision when the angle between the delta volts and delta

current shifted by the Dir. Char Angle setting is greater than 90°. The Dir. Char Angle setting is the characteristic

angle of the source impedance, Zs.

V02706

RCA = Characteristic angle setting (Dir. Char Angle)

RCA

Forward

Reverse

Figure 81: - DV Forward and Reverse tripping regions

To facilitate testing of the distance elements using test sets, which do not provide a dynamic model to generate

true fault delta conditions, set the Static Test Mode setting in the COMMISSIONING TESTS column to Enabled.

This disables phase selector control and forces the protection to use a conventional (non-delta) directional line.

Chapter 7 - Distance Protection P543i/P545i

178 P54x1i-TM-EN-1

GE P24DM User Manual

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