First, the contestants analyzed the dual-ended Comtrade fault records, captured by two SMART Blocks®, source-end waveform shown below:

Drag to Zoom

The contestants could see the fault was a Single Line-to-GND (SLG) fault (phase B) and they were provided the line-length, PT/CT ratios, and Phase-B based Sequence Components, as below:

Line Characteristics

Line length (miles):

PT ratio:

Whole number

CT ratio:

Whole number

B-PHASE BASE For fault types: B-GND, A-C, and A-C-GND

Roger's handy tip #117:

During normal (pre-fault conditions), each of the three voltage and current phase signal sets are "balanced" (ie, of similar magnitudes and equally separted in phase). During a fault, these phasor sets become unbalanced, both in terms of magnitude and phase separation.

These sets of unbalanced phasors can be fully resolved by the creation of three sub (component) sets of balanced phasors such that when vectorially added together, sum to equal the set of unbalanced phasors.

Balanced sequence component sets:

Zero (in phase)

Positive sequence (normal phase rotation)

Negative sequence (reverse phase rotation)

Being balanced, enables traditional 3-phase voltage calculations (such as Kirchoffs laws) to be applied to any of these sequence component sets "during" fault conditions. This then, enables the calculation of "distance-to-fault" which is vitally important in helping to reduce restoration times.

Source end

Zero Sequence Components

Positive Sequence Components

Negative Sequence Components

v0_b_rms:

0.00

v0_b_ang:

0.00

v0_b_re:

0.00

v0_b_im:

0.00

i0_b_rms:

0.00

i0_b_ang:

0.00

i0_b_re:

0.00

i0_b_im:

0.00

v1_b_rms:

0.00

v1_b_ang:

0.00

v1_b_re:

0.00

v1_b_im:

0.00

i1_b_rms:

0.00

i1_b_ang:

0.00

i1_b_re:

0.00

i1_b_im:

0.00

v2_b_rms:

0.00

v2_b_ang:

0.00

v2_b_re:

0.00

v2_b_im:

0.00

i2_b_rms:

0.00

i2_b_ang:

0.00

i2_b_re:

0.00

i2_b_im:

0.00

Remote end

Zero Sequence Components

Positive Sequence Components

Negative Sequence Components

v0_b_rms:

1.56

v0_b_ang:

72.21

v0_b_re:

0.48

v0_b_im:

1.48

i0_b_rms:

1.72

i0_b_ang:

164.88

i0_b_re:

-1.66

i0_b_im:

0.45

v1_b_rms:

23.52

v1_b_ang:

-86.95

v1_b_re:

1.25

v1_b_im:

-23.49

i1_b_rms:

2.04

i1_b_ang:

-175.05

i1_b_re:

-2.03

i1_b_im:

-0.18

v2_b_rms:

1.74

v2_b_ang:

67.21

v2_b_re:

0.67

v2_b_im:

1.60

i2_b_rms:

1.41

i2_b_ang:

160.84

i2_b_re:

-1.33

i2_b_im:

0.46

For Single Line-to-GND (SLG) faults, the sequence networks connect in series at the fault point, as below:

Our winners knew that each sequence network is comprised of two parallel paths (between fault nodes), therefore the sum of the voltage drops along each parallel path must be equal.

Using the negative sequence loop is preferred as this network is unaffected by load or zero-sequence mutual coupling.

Therefore, summing the voltage drops along each of the parallel paths within the negative sequence network provides:

Knowing the line impedance (Z2L) and Sequence Components provided by ASAPiQ™ above:

Line impedance (real):

Ohms primary

Line impedance (j):

Ohms Primary

Then m is calculated as:

M_MAG:

nan

% of line-length from source

M_ANG:

nan

And:

Distance-to-Fault:

nan

miles from source

However, our contestants didn't know the line impedance. Instead, they knew the distance-to-fault (a function of m).

Therefore, rearranging the above formula to solve for Z2L, gives:

ASaP iQ™ Advanced Sensing and Prediction platform uses the above techniques to automatically calculate the line-impedance (once the distance-to-fault is entered) or to automatically calculate distance-to-fault (once the line impedance is entered). Both are valuable tools in helping protection engineers quickly and reliably pinpoint the location of faults to help shorten restoration times and keep production lines up and running.