Dranetz Visa Guide de l'utilisateur télécharger pdf (Page 119)

6-5

CH 6/ Advanced Setup Options

Procedure to

record transient

disturbance

(continued)

Continued on next page

Action... Result...

STEP 2: PowerVisa shows the

“floating window” algorithm used

for waveshape fault detection.

• Press limit field under

Threshold to change limit. Use

the keypad to enter the

threshold limit or tolerance. If

the wave samples differ by

more than the threshold

tolerance for a time exceeding

the duration or window percent

of power frequency cycle, a

waveshape fault is registered.

• Press limit field under

Duration to change limit. Use

the keypad to enter the

threshold duration or window.

• Enable toggles whether this

limit is enabled or disabled.

• Amps toggles between Volts

and Amps.

• Press Group A B C to set

identical waveform threshold

duration values for Channels A,

B and C.

• Press Next to set the rms

distortion waveshape limit.

Proceed to Step 3 on page 6-6.

• Press Prev to return to the

instantaneous peak transient

screen.

• Press Cancel to retain previous

threshold duration and return to

Advanced Options menu.

MARK112_104

Brief explanation on floating window algorithm:

The figure above helps illustrate the “floating

window” algorithm used for waveshape fault

detection. This window is visualized on screen as

sliding along a waveform, precisely one cycle

behind the previous sample point, v

. The height

of the window defines a maximum allowable

voltage deviation in magnitude. The width of the

duration corresponds to a number of sample

points, N. For each sample v

, when compared to

i-1 cycle

where the deviation in magnitude is

outside the maximum allowable deviation, a

counter is incremented. For each sample v

that is

within the maximum allowable deviation, the

counter, if greater than 0, is decremented. If the

count reaches N, a trigger occurs.

Present

Cycle

Previous Cycle

with Floating Window

Trigger

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Dranetz Visa Guide de l'utilisateur Page 119

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