Flyer · EN — Service flyer describing OEM preventive maintenance for AIS 3AP dead tank circuit breakers (DT) and dead tank compact switchgear (DTC). It outlines the four-step maintenance procedure (diagnostic test, inspection, preventive maintenance, function test) using the 25-year revision of a 3AP1 DT 145 kV as the example, and gives the recommended check and maintenance intervals by switching duty: checks after 12 years and full maintenance after 25 years, with operation-cycle limits ranging from 1,000 to 10,000 cycles depending on the component and load type. Following the OEM schedule supports an expected breaker lifetime of more than 50 years.
Siemens Energy dead tank circuit breakers rank best-in-class for Mean Time Between Failures (MTBF). Their build quality supports a long service life and continuous fault-free operation of the breaker — and, by extension, of the whole system. Achieving the expected lifetime of more than 50 years, while preserving operational stability, safety, reliability and availability, depends on following the OEM maintenance instructions.
Service attendance is offered across the entire operating life of the circuit breakers: inspection, maintenance, repair and a round-the-clock fault service provide the necessary backup.
Preventive maintenance follows the OEM's recommendation; the example given is the 25-year revision of an AIS 3AP1 DT 145 kV breaker. The work is organized into four steps.
Step 1 — Diagnostic test: SF6 filling and gas analysis.
Step 2 — Inspection: rupture diaphragm, visual check of the circuit breakers, control of the main contact system and switching modules, and a leakage test.
Step 3 — Preventive maintenance: replacement of parts per OEM recommendations, maintenance of the operating mechanism, cleaning of the gas compartment, and anti-corrosion protection.
Step 4 — Function test: mechanical and electrical function test, test operation, hydraulic monitoring system, trip and close solenoids — resulting in increased equipment reliability.
Procedures strictly follow the manufacturer's requirements, with a wide scope of measures that can be matched to individual needs for economical solutions. Work is carried out by certified technicians using original spares, with fast execution.
Maintenance is predefined according to the manufacturer's recommendation but can be flexibly adapted to individual requirements; Siemens Energy helps customers choose an adequate and cost-effective solution. All services are supervised or performed by certified Siemens Energy experts.
After commissioning, each component follows a periodic cycle: a check after 12 years and a full maintenance after 25 years, or earlier if the stated number of operation cycles is reached first. The cycle then repeats. Intervals differ by switching duty for the breaker, and by component for the disconnector and earthing switch integrated in the DTC.
| Component / switching duty | Check after | Maintenance after |
|---|---|---|
| Circuit breakers DT and DTC — switching of ohmic-inductive loads | 12 years or 6,000 operation cycles | 25 years or 10,000 operation cycles |
| Circuit breakers DT and DTC — switching of reactive loads | 12 years or 3,000 operation cycles | 25 years or 6,000 operation cycles |
| Disconnector (DTC only) | 12 years or 5,000 operation cycles | 25 years or 10,000 operation cycles |
| Earthing switch (DTC only) | 12 years or 1,000 operation cycles | 25 years or 2,000 operation cycles |
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