Page 16 - PD Experience on 3-5kV

Trend Analysis Plot Qm only
Mach. Qm+ Mach. Qm-
350
300
250
xis
A
200Y
150
100
Jul Oct Jan 2016 Apr Jul Oct Jan 2017
2015 X Axis
Figure 12. Periodic Test – High, but stable

Trend Analysis Plot Qm only

Mach. Qm+ Mach. Qm- System Qm+ System Qm-
500
400
300xis
A
200 Y
100
0
2010 2015
X Axis
Figure 13. Periodic Test – High but Increasing trend

4.2 DATABASE ANALYSIS FOR PD MAGNITUDES
From the database, here are the statistics based on over 300 motors. [7]
Rated kV 2-5
Negligible 25% 9 25% of the results have Qm levels below this value
Low 50% 22 50% of the results have Qm levels below this value
Typical 75% 62 75% of the results have Qm levels below this value
Moderate 90% 216 90% of the results have Qm levels below this value
High 95% 360 95% of the results have Qm levels below this value

4.3 FAILURE MECHANISM PD PATTERNS

Failure Results
Mechanism Definition out of Failure Mechanisms based on PD pattern
200
Clouds or Zero
Leads 4 Leads
crossings
Interphasal Phase-to-phase 19 Interphasal
Delamination/ Negative 71 Delamination
+
Impregnation Predominance Thermal Deterioration
Thermal No Predominance 1 Surface Activity
Deterioration
Movement/ Positive 0 10 20 30 40 50 60 70 80
Slot discharge Predominance 24
++

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