THE PERFORMANCE OF VICTORIA'S PRIVATISED POWER STATIONS
 
 Contents

4. SOME BACKGROUND ABOUT MAINTENANCE OUTAGES
4.1 Causes of loss of availability.

Information concerning the causes of outages is not available in the public domain in Australia.  For this kind of information NERC data is the best available.  Some of the detailed data from NERC is shown on Table 4.  Table 5 gives a typical outage program for major power stations in Victoria and typical values of LOA associated with the various kinds of outage.
Note that the concept of boiler cleaning, is an activity specific to the Victorian brown coal fired power stations where an accretion develops on the boiler tubes during the course of a boiler run.  The boiler must be taken off line every so often and this accretion must be washed off.

Table 4:   NERC  Data for Fossil-Steam Units  400-599 MWe 1992-1996
Losses due to outages and deratings by cause code categories
 
  ALL FOSSIL   COAL ONLY  
Cause of outage Equiv. hrs per unit % LOA Equiv. hrs per unit % LOA
Boiler 827.76 9.4 926.13 10.6
Balance of plant 193.26 2.2 152.24 1.7
Steam turbine  333.41 3.8 316.77 3.6
Generator  91.76 1.0 79.5 0.9
Pollution control equipment 43.46 0.5  36.02 0.4
External 17.22 0.2  21.02 0.2
Regulatory, safety, environ 28.88 0.3 21.66 0.2
Personnel errors 4.94 0.1 6.22  0.1
Performance 3.39 0.0 3.31  0.0
TOTAL 17.5 17.7
Boiler tube leaks 194.46  2.2 245.78 2.8
Boiler overhaul and inspections  388.33 4.4  451.39 5.1
TOTAL Pressure Equip (including turbine)   41.8    48.1
 
 
 Table 5:  A typical plant outage program
 
Description Typical frequency Typical duration Typical LOA Content of outage
Major outages Every 4 years 4-8 weeks  2-4 % Planned major repairs 
Full inspection
Minor outages Yearly or six monthly 3-5 days 1% Critical planned inspections and repairs
Boiler clean(This type of outage is required only by brown coal boilers)  Determined by fouling in boiler- 3-6 months 2 days 1%(Brown coal only) Heat transfer surfaces cleaned. Inspections may be possible in some areas.  Always happens at beginning of minor and major outages.
Forced outage Random event  2-3 days 2-8% Repair the failure and inspect other equipment at immediate risk
TOTAL 6-14%
 
 
National Conference 1999
 
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