Page 20 - PD Experience on 3-5kV
P. 20

Bipolar Machine PD
                                                                         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
                                                                     300                                300
                                                                     200                                200
                                                                     100 e [m V ]                       100
                   5.6  MODERATE BUT CHANGE IN                        0                                 0
                                                                     P ulse M agnitud
                         PATTERN                                    -100                                -100
                   Plant:  4kV Induction Motor, 1250hp              -200                                -200
                   Original test date was: May 2009 (periodic)      -300                                -300
                   PD Values:  Qm+ 95mV, Qm- 125mV                      0  45  90  Phase Angle [deg] 225  270  315  360
                                                                                   135
                                                                                      180
                   Pulse phase analysis:  primarily internal PD, but may be   Jun 2013
                   interphasal                                                    Bipolar Machine PD
                   Follow-up monitoring: initial increase but since Jun   1 to 3.16 pps  3.16 to 10 pps  10 to 31.6 pps  31.6 to 100 pps
                   2011 primarily stable [Figure 12]                     100 to 316 pps  316 to 1000 pps  > 1000 pps  Subset 8
                   Comparison of Jun 2011 to Oct 2013 showed similar   300                              300
                                                                     100 e [m V ]
                   magnitudes but a significant change in PD pattern   200                              200
                   New PD Values: Qm+ 132mV, Qm- 161mV                                                  100
                                                                     P ulse M agnitud
                   Current situation:  continue to monitor, but consider   0                            0
                   additional testing because of the change in PD pattern   -100                        -100
                                                                    -200                                -200
                                                                    -300                                -300
                                                                        0  45  90  135  180  225  270  315  360
                                                                                  Phase Angle [deg]
                                                                   Jun 2011


                                                                                  Bipolar Machine PD
                   5.7  INCREASE BUT NOT PD                              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, 1.865MW          150                                150
                   •   Original test date was: Sep 2007 (periodic)   100 V ]                            100
                   •   PD Values:  Qm+ 16mV, Qm- 8mV                  50                                50
                   •   Pulse phase analysis:  negligible PD          P ulse M agnitude [m  0            0
                   •   Follow-up monitoring: increase in Apr 2014 (see   -50                            -50
                       below)                                       -100                                -100
                   •   Comparison of Nov 2013 to Apr 2014 shows a   -150                                -150
                       single source at or near the zero crossings that has   0  45  90  135  180  225  270  315  360
                       reversed polarity.  This is not PD.                        Phase Angle [deg]  Apr 2014
                   •   Decision:  continue to monitor
                   •   New PD Values: Qm+ 56mV, Qm- 88mV
                   •   Current situation:  no problems indicated

                                      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-     Activity Qm+   Activity Qm-
                90                                                                       100 to 316 pps  316 to 1000 pps  > 1000 pps  Subset 8
                80                                                                    150                         150
                70                                                                    100 V ]                     100
                60                                                                    50                          50
                50 xis                                                                 0                          0
                40  A
                30  Y                                                                 P ulse M agnitude [m  -50   -50
                20                                                                   -100                         -100
                10
                 0                                                                   -150                         -150
                       2009      2010      2011      2012      2013      2014
                                                                                                 135
                                                                                                    180
                                                X Axis                                  0  45  90  Phase Angle [deg] 225  270  315  360
                                         Long-term Trend                                        Nov 2013


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