Prezentare izolatie Metrel
Transcript of Prezentare izolatie Metrel
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High Voltage Insulation Diagnostics
Presented by: Bostjan Flis
WELCOME!
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Content overview
Application areas of HV insulation testing
What influences insulation resistance
Symptoms of bad insulation
Testing methods Insulation testing with DC test voltage - insulation characteristics
Insulation testing with DC test voltage - test parameters
Limit values
Connection schemes
Test data evaluation i.e. statistics keeping
General requirements for HV insulation testers Metrel HV insulation testers
Metrel's solution providing, services and development
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Application areas of HV insulation testing
Insulation resistance testing is part ofpredictive maintenance of:
- Rotary machines (generators, motors)
- Transformers (industry, utilities, power distribution)
- Cables
- Measuring transducers
- Distribution boards
Benefits:
- Lower TCO (total cost of ownership)
- increased electrical safety
- prevention against fire hazard
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What influences insulation resistance
- Thermal exposure
- Overload
- Moisture
- Electrical shocks
- Mechanical shocks (vibrations, bad transportation)
- Dirt (oil, dust, conductive materials)
- General ageing of insulation
Symptoms of bad insulation
- Insulation breakdowns in a form of electrical short-circuits
- Fire
- Long-term downgrading values of insulation resistance
- Insulation resistance values under by standards determined values
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Insulation testing methods
- AC insulation testing (50/60Hz, 1 minute)
- Insulation surge breakdown testing
- Insulation testing with switching voltage
- Insulation testing with DC voltage
- Dielectric losses (tg)
- Partial discharges
- U I characteristics
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Insulation testing with DC test voltage - insulation characteristics
Riso Cpi
Rpi
Cis
Riss
Riss
Itot
+
Guar
U
ICisoIRCpiIRiso
IRiss U Test voltage
Riss1 and Riss2 Insulation surface resistance
Riso Insulation resistance
Ciso Capacitance of an insulation system
Rpi Polarisation resistance
Cpi Polarisations capacitance
Itot Total insulation current
IRiss Insulation surface leakage current
IRiso Resisitve part of the insulation current
IRCpi Polarisation current
ICiso Capacitive part of the insulation current
uA
0
10
20
30
40
t [s]0 200 400 600 800
IRiso
Itot
IRiss
IRCpi
ICiso
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Insulation parameters
Polarisation Index (PI)
PI = R tot (10 Min) / R tot (1Min)
Dielectric absoption ratio (DAR)
DAR = R tot (1 Min) / R tot (30 Sek)
Dielectric discharge (DD)
DD = I DIS (1 min) / (U * C ISO )
I DIS.a discharge current measured 1 minute after disconnecting the insulation system from the test voltage
C ISO. capacitance of the insulation system
U test voltage Discharge of
Ciss
Ito t
[s]10 20 30 40 50 6000
Badinsulation
Goodinsulation
Discharging of Cpi
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Limit values for insulation testing
with DC voltage
Insulation resistance
Limit value
General applications > 1M per 1kV der Nennspannung des Prflings
Rotary machines according toIEEE 43-2000
a./ 1 M + 1 M/1kVb./ 5 M for motors under 600Vc./ 100 M for motors above 600V
Switching- and control devices according to IEC 60439-1 > 1k for 1V of the UN of the test object
Splitting transformers and safety low voltage transformers accordingto IEC 61558 a./ Basis insulation > 2Mb./ Additional insulation > 5M
c./ Reinforced insulation > 7M
Polarisation index (PI)
PI Wert
Evaluation
1 to 1.5 BAD (valid for older types of insulation materials)
2 to 4 SUFFICIENT (valid for older types of insulation materials)> 4 VERY GOOD (also for the modern type of insulation materials)
Dielektric absorption ratio (DAR)
DAR value
Evaluation
< 1 BAD
1 DAR 1.25 SUFFICIENT
> 1.4 VERY GOOD
kVM ni UR
Thumb rule(motors and generators):
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Connection schemes
Precondition!
- Measuring object has to be disconnected from power supply network (voltage free)
- Surface of the insulation system has to be dry and clean
VNNN
G
VNNN
G
VNNN
G
Power transformer
HV vs LV
HV vs G
LV vs GDevice A Device B
Device N
Power supply
PE - ground
Port A Port A Port A
Port BPort B
PE PE
Port C1
Port C2Port C2
Port C1Port C
Multiple devices
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Test data evaluation i.e. statistics keeping
Statistics
- Always assure the same measuring conditions
(connection, temperature, test voltage, diagnostics parameters)
- Regular test intervals (6 months or one year)
- Results keeping for the entire life period of the equipment
- Observation of downgrading trends
Temperature coefficient
(all values are to be calculated on 75C)
rK
RR1
//i10/75i10
0304,028,2
10r
K
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General requirements for HV insulation testers
Test functions:
- Insulation resistance
- Step voltage test
- Capacitance
- PI, DD, DAR
- Current in A and mA range
- Voltage AC/DC
Accessories:
- Shielded test leads
- High quality test terminals (HV, antistatic, high surface resistance)
- PC Software for downloading of test results and creating test reports
Other features:
- Guard terminal to eliminate surface insulation currents
- Automatic discharging of the test object after measurement
- Built-in timer
- On-Line graph R = f(t)
- EM immunity for usage in HV environments
- EM Filters for improved accuracy
- Good charging system (accus or mains or both)
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Metrel HV insulation testers
Integrated features:
Test voltage up to 10kV DC
Resistance measuring range up to 10T
Automated calculation of PI, DAR and DD for profound insulation diagnostics
On-Line R=f(t) display
Test voltage setting in 25V steps
Shielded 12kV test leads to reduce influence of external EM fields
CAT IV/600V over-voltage category for utilities and industrial applications
New TeraLink PRO Windows PC Software for TeraOhm 5kV PlusHandbook Modern insulation testing on CD
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Metrel's solution providing, services and development
Product training in Metrel training centre
On-Line technical support
Application training and publications
Repair & Calibration training
Calibration equipment
Repair & Calibration services
Advanced technical solutions for all products segments
(Hardware, Firmware, PC Software)
Customised solutions (Instruments, Software, Accessories)
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WHY NOT
METREL?
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THANK YOU!
You have already made a good decision