Short answer
OCS maintenance follows "periodic maintenance combined with condition-based maintenance" and is divided by scope of work into three levels: routine maintenance (localised defects, scheduled as they arise), comprehensive repair (sectional, systematic rectification carried out in batches during possession windows) and overhaul (renewal or upgrading of whole tensioning sections and whole blocks that have reached end of life or lost capacity). The baseline inspection interval for high-speed and conventional lines is set by the operating maintenance rules (a matter of days).
The logic behind the three levels
The depth of deterioration is matched to the strength of the intervention: early localised deterioration is restored by routine maintenance with minimum intervention; linked sectional deterioration moves to comprehensive repair in batches; and items approaching end of life are renewed by overhaul. Condition-based maintenance uses 6C inspection data to grade equipment health and schedules targeted work by grade, avoiding both under-maintenance and over-maintenance. It is worth noting that the TB/T 30013 to 30018 series, effective 1 September 2026, establishes for the first time a "three-level maintenance" system standard for rolling stock and similar equipment, and the maintenance philosophy of OCS operation points the same way.
What it means for material procurement
Comprehensive repair and overhaul batches are the windows where material demand concentrates; replacing wire in a section that has reached its wear limit needs a complete set for the whole section (contact wire, splice clamps, droppers and terminal anchors), so lead times should be locked in early.
Related reading
33 new railway standards in force from today (including the three-level maintenance system) | Wire replacement product set
Reference: Siwei OCS Encyclopedia — maintenance intervals and grades (CC BY-SA 4.0)