Page 18 - PD Experience on 3-5kV

5.3 IMMEDIATE REWIND 1 to 3.16 pps 3.16 to 10 pps 10 to 31.6 pps 31.6 to 100 pps
Bipolar Machine PD
• Plant: 4kV Induction Motor, 1250hp 3000 100 to 316 pps 316 to 1000 pps > 1000 pps Subset 8 3000
• Original test date was: Apr 2008 (portable instrument) 2000 2000
• PD Values: Qm+ 1368mV, Qm- 1466mV 1000 1000
• Pulse phase analysis: arcing at the motor terminals P ulse M agnitude [m V ] 0 0
combined with both internal and surface voids -1000 -1000
• Decision: rewind motor immediately in 2008 -2000 -2000
• PD Values: Qm+ 8mV, Qm- 4mV -3000 -3000
• Follow-up monitoring: slight upward trend since Jul 0 45 90 135 180 225 270 315 360
2009, new PD values Qm+ 53mV, Qm- 19mV Phase Angle [deg]

• Current situation: isolated source of arcing at motor Apr 2008
terminals indicated by a narrowband pulse near 225°

Trend Analysis Plot Qm only Bipolar Machine PD
1 to 3.16 pps 3.16 to 10 pps 10 to 31.6 pps 31.6 to 100 pps
Machine Qm+ Machine Qm-
100 to 316 pps 316 to 1000 pps > 1000 pps Subset 8
50 75 75
40 50 50
25 0 itude [m V ] 25
30 xis 0
A
20 Y -25 -25
10 P ulse M agn -50 -50
-75 -75
Jul Oct Jan 2009 Apr Jul Oct Jan 2010 Apr Jul Oct 0 45 90 135 180 225 270 315 360
2008 X Axis Phase Angle [deg]
Post-rewind Sep 2010

5.4 HIGH PD MONITORED THEN Bipolar Machine PD
REWOUND 1 to 3.16 pps 3.16 to 10 pps 10 to 31.6 pps 31.6 to 100 pps
100 to 316 pps 316 to 1000 pps > 1000 pps Subset 8
• Plant: 4kV Induction Motor, 3000hp 3000 3000
• Original test date was: Dec 2006 (periodic) 2000 2000
• PD Values: Qm+ 746mV, Qm- 817mV 1000 1000
• Pulse phase analysis: primarily internal PD P ulse M agnitude [m V ] 0 0
• Follow-up monitoring: mostly stable, but increase in -1000 -1000
negative PD Feb 2009, new PD values Qm+ 798mV, -2000 -2000
Qm- 1120mV. Negative predominance is a concern -3000 -3000
for multi-turn coil construction. (see below) 0 45 90 135 180 225 270 315 360
• Decision: rewound motor in 2010 Phase Angle [deg]
• New PD Values: Qm+ 8mV, Qm- 9mV Dec 2006
• Current situation: no problems indicated

Trend Analysis Plot Qm only
Machine Qm+ Machine Qm-
1500
1250
1000
750 xis
A
500 Y
250
0
2007 2008 2009 2010
X Axis

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16 | P age