Page 19 - GuardII+ Series 4208 Platform PD User Manual

PD Card Operation

NOTE:
PD typically increases slowly over time. If the PD increases to the point
where the PD is greater than the User Range can detect, then the User
Range results will indicate an Over Range (OVR) Quality Flag. This
indicates that it is time to re-configure GuardII+ to a different sensitivity for
the User Range.

4.3.2. Auto Range
The Auto Range tracks changes in PD levels over time. As PD levels increase, Auto
Range will change to a lower sensitivity (reading higher PD) so that the measurement results
are within optimal levels for the measurement sensitivity; likewise, if PD levels decrease, Auto
Range will change to a higher sensitivity (reading lower PD). The purpose of the Auto Range
is to provide snapshots of PD throughout the life of the machine; because the sensitivity can
vary from time to time for many reasons, establishing a long-term trend from the results of the
Auto Range may require careful selection of coherent measurements.
The Auto Range does not change ranges immediately when it detects a PD level change;
the Qm value must be out of range for the current sensitivity in 4 consecutive measurement
cycles. Each input is tracked separately; so, if Qm levels are out of range on the Phase A
input, Phase B input, Phase C input and then Phase A input again, this does not count as 4
consecutive measurements out-of-range. Only 4 consecutive measurement cycles on the
Auto Range of the same input can cause an Auto Range sensitivity adjustment for that input.
NOTE:
Auto Range will change sensitivity based on the highest amplitude activity.
In cases where the magnitude of the non-Asset PD activity is much higher
than Asset PD activity, Auto Range may not be suitable for trending Asset
PD, which is the winding partial discharge of concern to the User.

4.3.3. Alert Range

The Alert Range is a sensitivity that measures PD levels up to a set of Alert Thresholds
that are selected during commissioning. The sensitivity selected for the Alert Range is based
on the desired Qm level of the Very High Alert Threshold used in the Triggers (refer to Section
4.6 for PD Trigger details). The purpose of the Alert Range is to provide a consistent trend
from commissioning time until the Alert Threshold is exceeded.

Like the Auto-ranging behavior, the Alert Threshold must be exceeded over 4 consecutive
measurement cycles on the same input before an Alert state actually occurs.

NOTE:
In cases where the Alert Threshold is far higher than the current PD levels,
the Alert Range may not show much (possibly any) data. This does not
necessarily indicate a problem with the GuardII+, although the Alert
Thresholds should be verified.

11
www.irispower.com