On-line PD Monitoring Applications - IIT Armour

76 Pages·2011·2.12 MB·English

On-line PD Monitoring Applications
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Failure Statistics
30
Australia & New Zealand
25
10 Years of Data
457 Failures
20
% 15
-

t
n
e
c
r 10
e
P
5
0
Windings Winding Core Tap Changer Motor Drive Bushings Cooling Other
Accessories Parts
Failure Statistics
35
Eskom
30
136 Severe Failures
25
1996 - 2006
%
20
-

t
n
e
c
r 15
e
P
10
5
0
Windings Core Tap Changer Main Tank & Oil Bushings Auxiliaries Others
System
Failure Statistics
35
Canadian Electricity Association
30
Forced Outages
1997 - 2006
25
%
20
-

t
n
e
c
r 15
e
P
10
5
0
Bushings Windings OLTC Core Leads Cooling Auxiliaries Other
Failure Statistics
50
Doble Engineering
45
40
1993 - 1998
35
% 30
-

t
n
25
e
c
r
e
P 20
15
10
5
0
Bushings Tap Changer Tank and Oil Core Winding Other
Failure Statistics
Bushing Monitoring
Power Factor
Capacitance
Partial Discharge
ΔT
DGA
Partial Discharge
Moisture in Oil
Operations Counters
Oil Dielectric
Cooling System
Contact Wear
Partial Discharge
Monitoring
Control Monitoring
Leakage Reactance
Fan Current
Online FRA
Control Failure
Issues With Time Based
Maintenance
Time between outages extended

Many failure modes happen quickly (days, weeks, months)

Off-line tests can not simulate actual operating conditions

(temperature, voltage, load, mechanical)
Historical data not sufficient to make a good decision

Less thorough maintenance

Can introduce new failure mechanisms

Time to Failure
Very Difficult to Predict / Forecast

Studies have shown

80% of all failures are random in nature

20% age related

If this is true, then current maintenance

practices are not all that effective
Time To Failure
Good Bill of Health

Only means there is no clue as to the unit will

fail
Easier to Predict when Failure is imminent

Advanced stages of deterioration

The only true way to capture impending

failure is to monitor continuously
Transformer Bushing Monitoring