MOTOR online PD test IRIS Presentation

1. Classification: Internal Use
WHY IRIS IS DIFFERENT

2. Classification: Internal Use
Epoxy-Mica Capacitors EMCs
 Over 60,000 Iris EMC’s installed
 Reliable, conforming IEC TS 60034-
27-2 and IEEE 1434
 Directly Connected to HV bus
 80 pF creates a HPF with a cutoff of
40 MHz
 Turbo – 2 per phase
 Separates noise based on pulse
direction
 Motor – 1 per phase
 Separates noise based on pulse
shape
PD Sensors for Motors & Small
(usually <200MW) Turbos

3. Classification: Internal Use
3
DM 2000DM 2000
Couplers on Machine Terminals

4. Classification: Internal Use
Iris Termination Box
Most Generators –
“Double Ended”
Most Motors – “Single
Ended”
2 sensors installed per
phase
1 sensor installed per
phase

5. Classification: Internal Use
Periodic Monitoring

6. Classification: Internal Use
Continues Monitoring

7. Classification: Internal Use
Electrical Noise
• In on-line test, electrical interference from ‘noise sources’ such as
transmission line corona, sparking electrical connections, slip ring
sparking, power tool operation
• This noise masks stator winding PD – non specialists may assume
stator is close to failure, when high levels of relatively harmless noise
present – false indications
• Iris commercially manufactures sensors and instruments that
successfully separate electrical noise from PD
• Thus very low risk of false indications; users can perform and interpret
results with only 2 days training

8. Classification: Internal Use
Failures because of Winding Insulation
Source: CIGRE Study Committee SC11, EG11.02, “Hydrogenerator
Failures– Results of the Survey,” 2003, as cited by Brutsch, R., Tari, M.
; Frohlich, K. ; Weiers, T. ; Vogelsang, R. “Insulation Failure
Mechanisms of Power Generators”, IEEE EIM July-Aug 2008.
Source: “Assessment of the Reliability of Motors in Utility
Applications,” IEEE Transactions on Energy Conversion,
Vol. EC-2, No. 3

9. Classification: Internal Use

10. Classification: Internal Use

11. Classification: Internal Use
Multi-turn Coil
What is inside?
How is it made?
Epoxy to glow the
tap of mica

12. Classification: Internal Use
Electrical Representation of Partial
Discharge
Appl
ied
Cin
Cin
Cair
Vair
Applied
0 V
 Potential difference
(voltage) builds across
an air-filled void
 PD occurs if V/Dv >
3kV/mm ( i.e., electrical
stress exceeds
electrical breakdown
point of gas)
 2KV Across the voids
 The larger the void, the
larger the discharge

13. Classification: Internal Use
13
DM 2000DM 2000
What Are Partial Discharges?
• Small electrical sparks in air-filled cavities in or
adjacent to HV electrical insulation
• They occur because breakdown strength of air
(3 kV/mm) is much lower than that of solid
insulation (~300 kV/mm)
• Partial Discharges create small voltage pulses
– PD is monitored by detecting and measuring these
small voltage pulses

14. Classification: Internal Use
50/60 Hz phase-to-
ground voltage
Breakdown
voltage of void
Voltage across
the void
sustain
sustain
Partial Discharge
PD Pulse Characteristics:
 Extremely fast rise-time current pulse = short pulse width
 High-frequency, Rise time = 1 – 5 ns  Frequency range = 50 – 250 MHz
 Discharges also affect carbon bonds in resin
 PD is very dependent on voltage

15. Classification: Internal Use
PD IS A SYMBTOM OF FAILURES

16. Classification: Internal Use
Poor impregnation of coils (voids)
Internal
Voids

17. Classification: Internal Use
17
DM 2000DM 2000
Inadequate spacing between coils

18. Classification: Internal Use
18
DM 2000DM 2000
load cycling
Separation of insulation from
copper

19. Classification: Internal Use
Rotating Machines
• Primary assets, critical to operation
• Failures result dramatic consequences and revenue
losses, Risks!
• Exposed to various stresses: Thermal, Mechanical,
Electrical, Environmental & Chemical
• No one can manage what can’t be measured! Thus
managing risks associated with machine failures
require meaningful measurements

20. Classification: Internal Use
20
DM 2000DM 2000
Noise pulses are oscillatory and
have a width >6 ns

21. Classification: Internal Use
5 20 40 100 350
Frequency (MHz)
Test Frequencies (40-350MHz)
Maximum Signal-to-Noise Ratio (SNR)
Noise
Noise Filtration: High Frequency Domain
Partial Discharge (5-250+MHz)

22. Classification: Internal Use
22
DM 2000DM 2000
Simultaneously Use 4 Methods to
Separate PD from Noise
• High pass filter (noise predominantly <20 MHz)
• Time of pulse arrival between a pair of couplers
• Pulse shape analysis (risetime and degree of
pulse oscillation)
• Surge impedance mismatch

23. Classification: Internal Use
Disturbance Separation: Directional Time-
of-Arrival (Bus)
 2 m / 6 ft
Delay time
7ns
Classification Machine System
Unit PD L1 L1 + Delay
System L1 + Delay L1
Bus Noise L1 + < Delay L1 + < Delay

24. Classification: Internal Use
Disturbance Separation: Pulse
Shape Analysis
a) Pulse with fast rise time; probably a PD
b) Pulse with long rise time; likely to be noise
Classification Machine System
Unit PD All PD Null

25. Classification: Internal Use
Pulse Propagation through Power
Cable
0.055
V
0.0495
V
0.0055
V
0.008
V
0.0008
V
0.007
2 V

26. Classification: Internal Use
26
Iris PD Database
• Over 550,000 test results from thousands of
machines
• Each 2 years Iris publishes the statistical range of
Qm (peak PD) for each type of stator (voltage
rating, air or hydrogen cooling, and PD sensor
type)
• If a stator has a Qm that exceeds 90% of readings
then winding is deteriorated
• False indication rate <1.5% due to noise
separation

27. Classification: Internal Use
PD Alarm Levels
Air-Cooled Machines (80 pF sensors)
Voltage Class PD Magnitude (mV)
2-4 kV 274
6-8 kV 276
10-12 kV 401
13-15 kV 461

28. Classification: Internal Use
28
Phase: C, Sensor(s): C-M3,C-S3 Delay 11ns, Status
OVR,HNPR
Machine: NQN+: 144, NQN-: 63, Qm+: 77, Qm-: 36
Asset Class: Combustion Turbine, Sensor Type: Epoxy Mica Capacitor (80pF)
Operating load: 46.4 MW, Reactive Load: 18.9 MVar, Operating Asset Temp 81 deg C, Operating Voltage 11.5 kV
Operating Gas Pressure: N/A, Ambient Temp 25 deg C, Ambient Humidity: 55 %, Freq. (Test Duration) 50 Hz. (5 sec.)
Manufacturer: --- Year of Installation: 1997, Winding Manufacturer: , Re-Wind Year:
Start Time: 6/11/2009 9:48:53 AM
System: NQN+: -, NQN-: -, Qm+: -, Qm-: -
-150
-100
-50
0
50
100
150
-150
-100
-50
0
50
100
150
-225 -180 -135 -90 -45 0 45 90
Pu lse D en sity L in ear Plo t
B ipola r M a c hine P D
P
u
l
s
e
M
a
g
n
i
t
u
d
e
[
m
V
]
P hase A ngle [deg]
0 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
-150
-100
-50
0
50
100
150
-150
-100
-50
0
50
100
150
-225 -180 -135 -90 -45 0 45 90
Pu lse D en sity L in ear Plo t
B ipola r T ota l S ys te m N ois e
P
u
l
s
e
M
a
g
n
i
t
u
d
e
[
m
V
]
P hase A ngle [deg]
0 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
Impact of Disturbance Separation

29. Classification: Internal Use
29
DM 2000DM 2000
13.8kV Stator in Same Plant with Very High PD
Qm: Peak PD magnitude in mV @ 10 pps
Pulse Height Analysis (PHA) 2D
Graph:
250 500 750 1000 1250 1500
Pulse Magnitude (mV)
250 500 750 1000 1250 1500
101
102
103
104
101
102
103
104
Pulse Magnitude (mV)
Unit PD Noise

30. Classification: Internal Use
30
DM 2000DM 2000
Example of Trending
0
100
200
300
400
500
600
700
800
900
1000
Qmax*
(mV)
+ PD
- PD
* Peak PD Magnitude in mV at 10 pps

31. Classification: Internal Use
Thanks