The CenturionTM on-line insulation performance monitor detects changes in oil dielectric strength and protects transformers, load tap changers, circuit breakers and any oil-filled equipment. The unit uses a non-destructive method to determine the level of carbon and metallic particulates, fiber, moisture and other impurities. It manages the overall health of all critical oil-filled equipment by mitigating risk of operating aging and overloaded transformers; extending maintenance cycle and prioritizing expenditures; increasing system reliability, thus reducing the chance of unscheduled outages; prolonging asset life-cycle, thus reducing capital expenditure; and providing low-cost insurance against expensive failures. This continuous on-line technology can guard the integrity of valuable substation assets. Correlation with lab samples can be made based on the readings obtained.