Page 77 - Mathematical Models and Algorithms for Power System Optimization

Optimization of Annual Generator Maintenance Scheduling 67

GMS study period, then the system cannot schedule maintenance for such units in
the studied period. The only feasible way is to postpone the maintenance cycles of
some units from the GMS study period.
b. For all generating units that participated in the inspection of concurrent
maintenance time nonoverlapping constraints, if the sums of their maintenance
time and minimum intervals between maintenance times is less than the total GMS
study period, then the system has the prerequisite for maintenance scheduling.
However, some units may not be tightly scheduled for maintenance (such as
pursuing maximum reserve capacity of the system), which causes an inability of
other unit maintenance to be inserted in the studied period. For this situation, in
case of failure to delay the maintenance scheduling of other units from the GMS
study period, it is required to give up the pursuit of maximum system reserve
capacity; instead, the maintenance start time for these units depends on their
sequence of last maintenance completion time and refers to their earliest and latest
start time of next maintenance of each unit. In addition, if the reserve margin in
some periods is unable to meet the system’s load demand due to such a schedule,
the load level in such a period must be curtailed to comply with the GMS
requirements.

3.5.3 Related Rules of the Expert System

3.5.3.1 Rules of determining priorities for unit maintenance
Rule 1: The maintenance priority manually assigned by the system dispatch engineer is the
highest one over others determined by other methods.

Rule 2: The unit with highest production cost has highest maintenance priority.
Rule 3: If two units have the same production cost, then the one with larger capacity has highest
maintenance priority.

Rule 4: If two units have the same production cost and capacity, then the one with early
completion time of the last maintenance has highest priority.

3.5.3.2 Rules of verifying GMS capability

Rule 5: If the system’s GMS operation index OPindex>1.0, then try to extend the interval
between the maintenance period of some units.