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2. Diagnostic Insulation Testing
Predictive Maintenance issues
Basis of Insulation Tests
Spot Tests & Polarisation Index
Dielectric Discharge Test
Power factor testing
AVO Range

3. Maintenance Regimes Corrective maintenance
Preventive (Periodic) Maintenance
Predictive Maintenance (Record & trend data to determine next action - variable maintenance periods)
Appropriate regime varies

4. Maintenance Regimes Value of Assets ? Critical role of Assets ?
Costs of failure ?
Costs of Maintenance regime ?
Manpower
Skills
‘Tools’ - Testing / Monitoring / I.T.

5. Why test insulation? System performance System safety
System reliability
Economic asset management
Over 60% failures caused by Insulation problems (CEGB & ERA Technology)

6. Insulation Failure Oil Contamination Mechanical damage Pin holes
Vibration
Temperature cycling
Moisture & humidity
Cracks

7. Test Techniques - DC Testing
Total Current has 3 components
Capacitive Current - Charging
Absorbtion Current -Polarisation
Leakage Current
TIME DEPENDENT
Temperature Dependent

8. Insulation Test Currents
100
I/uA
Charging
Total 10
Leakage
Absorption 1
0,1 1 10 T

9. Insulation Equivalent Circuit
Leakage
Capacitance
Absorption

10. Diagnosis from Insulation Tests
Record & Trend
Spot Tests - Record conditions as well (Temp, RH)
Time resistance tests - Polarisation Index Test (PI)
Step Voltage Test (SV)
Dielectric Discharge Tests (DD)

11. Insulation Test as a Go/NoGo Test
Spot Test carried out for given time (1 minute)
Commissioning
National /Manufacturer’s Standards

12. Time Resistance Tests Independent of equipment size and temperature
Some information without past results
Options;
Curves
Time - Resistance Ratios

13. Time ResistanceTest Absorbtion current visible
Absorbtion current not seen t1 t2
Time

14. Time Resistance Tests Polarisation Index Insulation Condition
(10 min/1 min ratio)
<1
1,0 - 2,0
2,0 - 4,0
>4,0
Insulation Condition
unsatisfactory
dubious
good
very good

15. Time Resistance Tests Dielectric Absorption Ratio (60 s/30 s)
<1
>1.6
Insulation Condition
unsatisfactory
dubious
good
very good

16. Step Voltage Test Test voltage is increased in 5 steps
Lower insulation resistance values at higher voltage indicate presence of cracks/holes

17. Step Voltage Test
5000 V
Resistance
2000 V
1000 V
Voltage

18. Dielectric Discharge Test
Test is run until currents stabilise
Measurements made on discharge DD = Current after 1 min Voltage x Capacitance

19. Dielectric Discharge Test+ - - - - - - + - + + - + - + - + + - - + - + + - - + - + + + + + + - - + -

20. Dielectric Discharge Test
DD Value
>4
<2.0
Insulation Condition
unsatisfactory
dubious
good

21. Tan Delta Testing Polarisation and capacitive current dominate
Aging (moisture/dirt) sensitive
Low voltages can be used

22. Perfect Insulation
I (capacitive)
ITOTAL
IR = 0
V (applied)

23. Facts about Insulation
In a “REAL insulation system” there is also a loss current flowing in-phase with the voltage // = IC IR
ITOTAL

24. REAL Insulation
I (capacitive) IC
ITOTAL IR
V (applied)

25. Facts about Insulation
In practice NO insulation is perfect
Resistive loss current is always present
Total current leads the voltage by a phase angle  and lags capacitive current by angle 

26. REAL Insulation
I (capacitive) IC
ITOTAL d  IR
V (applied)

27. What is Tan Delta?
Tan Delta is the ratio of in-phase (resistive) current to the 90-degree (capacitive) current
Tan Delta equals Dissipation Factor

28. What is Power Factor?
Power factor is the ratio in-phase (resistive) current to the total current.

29. Tan Delta Testing I(capacitive) IR Tan d = IC IC ITOTAL IR
Power Factor = d
ITOTAL  IR
V(applied)

30. Tan Delta v. Power Factor
Both values are similar up to 20% power factor and tan delta; beyond 20% they diverge.

31. Tan Delta 3 Terminal Test
Low voltage (L)
High voltage (H)
CHL
CLG
CHG
Ground Connection (G)

32. Tan Delta 3 Terminal Test
Configuration Measures
GST L-GND CHL + CHG
GST L-Guard CHG
UST CHL
GST H-Guard CLG
GST H-GND CHL + CLG

33. Why perform the Tan Delta Test?
Normal insulation resistance testing limited to 5kV dc
Tan Delta is up to 12kV ac
Most test specimens normally operate with AC voltage
Much closer resemblance to the normal operating condition of the insulation

34. Tan Delta Testing Comparison with name -plate values
Very sensitive to small changes
a.c. test at rated voltage
Larger, heavier test equipment

35. Insulation Test Diagnosis

36. Tests Performed On Transformers Circuit Breakers Rotating Machinery
Insulating Liquids
High Voltage Bushings
Surge Arrestors
High Voltage Coils

37. Diagnostic Testing - Where Used
P.I. Testing & Trending
Generators / Aerospace
Petrochemical/Process Industry
Transmission/Distribution
Pass/Fail
All electrical Equipment > 3 kV
Commissioning & Routine Maintenance
TREND to TRENDING !

38. MEGGER BM11D Portable, IP54 , large PbAcid battery
Readings to 500 GOhm
Display is large, clear & Easy to Use
Safety features
Automatic discharge, locking test leads, Hazard display
Integral Timer

39. MEGGER BM21 All BM11D features plus; Readings up to 5TOhm
Selectable Test Voltage
Selectable Test Time
Checks Capacitance at test End
Can show current as well as resistance
Burn mode

40. MEGGER BM25 As BM21 features plus; Automated tests
Polarisation Index
Step Voltage
Dielectric Discharge
RS232 download results every 5 s
Download software & lead

41. MEGGER S1-5005 As BM25 with 5 mA test current.
BM25 has 2 mA test current.

42. MEGGER S1-5010 Heavy Duty - Mains & Battery Automated Tests
Results Storage
RS 232 communications
Graphical Display

43. MEGGER S1-5010

44. MEGGER S1-5010 Memory for 75 sets of results Windows PC software
remote operation
results storage
External output for HV “ON” indicator
Switchable digital filter for noise rejection
IP54 weatherproofing

45. S and S1-S1 software
S1-5010

46. S1-S1 software Duplicates the S1-5010 on your PC screen.
Control the S from your PC via an RS232 link.
Download tests to your PC
in real time.
as a batch at the end of testing.
Annotate the tests results with details of the test.
Recreate graphs etc. in other software.

47. Test Start/Stop button Instrument On/Off switch
S via software
Voltage ON lamp
S1-5010
Soft keys
Soft keys
Test Start/Stop button
Instrument On/Off switch
Soft keys

48. S1-S1 Menu Bar - Window Remote Control Database Viewer
Selects the remote control window if a Database Viewer window is active.
Database Viewer
Selects a database viewer window if the Remote Control window is active or switches between Database Viewer windows if more than one is active.

49. Database Viewer - Details

50. Database Viewer - Graph

51. MEGGER EDA Electronic Dielectric Analyser Used on rotating machines
Simple to use
Automatic testing
Normalised parameters
Database of results

52. MEGGER EDA

53. MEGGER EDA Insulation of rotating machines Technique used for 15 years
hydraulic power generators
turbo-generator
6/12 kV motors
Technique used for 15 years

54. EDA Software
Notes:

55. MEGGER EDA Automatic testing PC controlled Motor data input
Test voltage input
Calculation of results

56. EDA Software
Notes:

57. MEGGER EDA Results at 2 test voltages Resistance Polarisation Index
Time constant (RC)
Dielectric Discharge
Absorption Index
Capacitance (ac & dc)

58. EDA Software
Notes:

59. MEGGER EDA Results Print out report Print out graphs Expert analysis
Comparison with previous results

60. BIDDLE Delta 2000 500 V - 12 kV power factor tester
Automatic bridge operation
High noise immunity
Menu driven display
Measures voltage, current, power (loss), power factor/tan-delta and capacitance

61. BIDDLE Delta 2000 Results storage Printer for on-site results
Downloading test data
Accessories
Oil test cell
Bushing connectors
Bar code wand

62. BIDDLE Delta 2000

63. BIDDLE 2.5 & 12 kV semi-automatic units
2.5 kV single unit construction
12 kV control unit and
Measure capacitance, dissipation factor and Watts

64. CB-100 Low Voltage Bridge 28 V test voltage Safe Compact Low cost
Often used on bushings & transformers

65. Testing with Safety How does the electrical risk appears ?
- When an electrical line or conductor is unexpectedly still live - When current sources are not properly isolated - When power generators are connected to the network - When there are atmospheric phenomenons such as lightning - Through induced currents

66. Testing with Safety
However, it has also been observed that the most common causes of unexpected presence of voltage on electrical lines or installations were due to: - A mistake in operating a switch - A mistake in identifying the work to perform - A "faulty" switch (one of the links for example remaining partially engaged)

67. Testing with Safety How does the electrical risk disappear ?
1. By observing Simple Electrical Safety Rules directed by common Sense (even if Working Practices vary from a country to another, GOLDEN RULES always apply) By using Simple, Light and Reliable Electrical Safety Equipment.

68. Testing with Safety
1. SEPARATE THE WORK AREA FROM ALL POSSIBLE SOURCES OF POWER SUPPLY by opening circuit-breakers, switches… AND LOCK THE LINKS IN THE OPEN POSITION

69. Testing with Safety
2. CHECK THE ABSENCE OF VOLTAGE at source and on site, on each conductor and apparatus involved.
3. APPLY APPROPRIATE SHORT- CIRCUIT AND EARTHING SYSTEMS in sufficient numbers on the conductors of your network where operation is taking place.

70. Testing with Safety
4. SHOWN, WARN OTHERS AND LIMIT THE WORK AREA even during the most simple temporary maintenance operation

71. Testing with Safety Discharge Sticks
Slowly discharge capacitive items (cables, capacitors….)
Discharge to a safe level in times RC (time constant)

72. Discharge Sticks Voltage Length Resistance Max. cap.
35 kV 50 cm 10 kOhm 6 uF
50 kV 136 cm 100 kOhm 6 uF
75 kV 156 cm 150 kOhm 4 uF
100 kV 176 cm 200 kOhm 3 uF
150 kV 208 cm 300 kOhm 2 uF

73. MEGGER Foster Oil Electric Strength Testers
Oil Testing
MEGGER Foster Oil Electric Strength Testers

74. Why test switchgear oil?
Prevent Transformer failure
Principle problems are:
humidity
oxygen
temperature

75. Oil Testing Methods Water content Acidity Colour Flash point
Gas content
Oil provides HV insulation
Electric strength is the most important test

76. Electric strength Test techniques
Electrode gap
Electrode shape
Vessel size
Voltage rise rates
Stand and stir times

77. Electric strength test results
Temperature affects values
Record results
Low results show presence of moisture or particles
Impurities from air, operator or equipment

78. Breakdown Testing

79. Electric Strength Test Results
Average over six tests
Scatter can be large
Standard deviation calculated
Report breakdown values, date, temperature

80. New Specification EN60156 Replaces IEC156 (1963) Optional stirring
Current limited breakdown for silicone oils
Gives guidance on scatter of results

81. Withstand Testing Test voltage held at preset level for 1 minute
Quick test of level of contamination
Increase to breakdown to find headroom?

82. Withstand Testing

83. MEGGER Foster OTSAF/2 Fully automatic, unattended operation
Wide range of tests including five custom
Results include standard deviation, time, date
Results printed or download via RS232
Stirring options for magnetic or propellor
60 kV, 80 kV and 100 kV versions

84. MEGGER Foster OTSAF/2

85. MEGGER Foster OTS60PB Portable oil test set for on site measurement
Battery powered for two days continuous use
Fully automatic, unattended operation
Pass/fail levels for go/no go testing
Small and lightweight (19 kg = 42 lb)
Complete with battery charger
Variety of electrodes
RS232 interface plus optional printer

86. MEGGER Foster OTS60SX Low cost, Semi automatic set
60 kV maximum output, 0,1 kV resolution
Simple START, STOP & PAUSE control
Weighs only 17,5 kg
Optional vessels for all specifications
Auto 60 second timer for withstand testing
Operates from 110/230 V power supply

87. MEGGER KF2000 Karl Fischer moisture in oil test set Simple to use
Quick results
Low cost
Battery powered, portable

88. MEGGER KF2000

89. Bringing Reliability to Amps Volts Ohms
AVO INTERNATIONAL
Bringing
Reliability to
Amps
Volts
Ohms 15 15

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