Page 19 - PD Experience on 3-5kV

5.5 SEASONAL PD
Bipolar Machine PD
• Plant: 4kV Induction Motor, 1250hp 1 to 3.16 pps 3.16 to 10 pps 10 to 31.6 pps 31.6 to 100 pps
• Original test date was: Mar 2009 (periodic) 100 to 316 pps 316 to 1000 pps > 1000 pps Subset 8
• PD Values: Qm+ 198mV, Qm- 372mV 750 750
250 e [m V ]
• Pulse phase analysis: High primarily internal PD 500 500
• Follow-up monitoring: initial decrease followed by an 250
P ulse M agnitud
apparent increase (see below) 0 0
• Comparison of Mar 2009 to Feb 2011 showed no change -250 -250
in magnitude or pattern, but the Jun 2009 levels were -500 -500
lower in magnitude (see below) -750 -750
135
• Decision: continue to monitor 0 45 90 Phase Angle [deg] 225 270 315 360
180
• New PD Values: Qm+ 227mV, Qm- 314mV Mar 2009
• Current situation: no problems indicated

Trend Analysis Plot Qm only
Machine Qm+ Machine Qm-
350
300
250 xis
A
Y
200
150
Jan 2009 Apr Jul Oct Jan 2010 Apr Jul Oct Jan 2011
X Axis

Bipolar Machine PD Bipolar Machine PD
1 to 3.16 pps 3.16 to 10 pps 10 to 31.6 pps 31.6 to 100 pps 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 8 100 to 316 pps 316 to 1000 pps > 1000 pps Subset 8
750 750 750 750
250 e [m V ] 250 250 e [m V ] 250
500 500 500 500
P ulse M agnitud P ulse M agnitud
-250 0 0 -250 -250 0 0 -250
-500 -500 -500 -500
-750 -750 -750 -750
0 45 90 135 180 225 270 315 360 0 45 90 135 180 225 270 315 360
Phase Angle [deg] Phase Angle [deg]
Jun 2009 (summer results – significantly less) Feb 2011 (winter results – same as Feb 2009)
Qm+ 177mV, Qm- 216mV Qm+ 227mV, Qm- 314mV

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17 | P age