Compact by design.
Certified by physics.
Siemens Energy dead tank circuit breakers with integrated current transformers — reliable, compact, and proven in thousands of installations worldwide.
The grounded-tank workhorse.
Siemens Energy dead tank circuit breakers (3AP-DT series) are designed for outdoor installation in high-voltage transmission networks. The dead tank design houses the interrupter unit inside a grounded metal tank, providing excellent seismic performance and allowing direct integration of current transformers (DT/DTC) within the bushing.
This integration eliminates the need for separate free-standing current transformers, reducing substation footprint and installation cost — the very reason utilities in North America, Australia and Japan have specified the 3AP-DT for decades.
Four engineering advantages.
Integrated CTs (DT / DTC)
Built-in current transformers cut substation footprint. DTC version provides high-accuracy measurement for protection and revenue metering.
Reliable Interruption
Self-blast arc-quenching technology ensures reliable interruption even under severe short-circuit fault conditions.
Seismic Resistant
Rigid dead tank design delivers excellent earthquake resistance — proven in seismic-prone regions from California to Japan.
Modular Mechanism
Spring-operated mechanism with minimal maintenance and up to 10,000 operations of mechanical endurance.
Global Certification
IEC 62271-100 and IEEE C37.04 compliant. Type-tested in independent laboratories including KEMA and IPH.
Wide Temperature Range
Reliable operation from −40 °C to +55 °C — engineered for outback substations and arctic transmission alike.
Two frames, one platform.
The 3AP-DT platform spans transmission classes 72.5 kV to 550 kV across two mechanical frames sharing the same interrupter, drive and control design.
DTC — Dead Tank with integrated Current Transformers
The DTC variant integrates high-accuracy current transformers directly into the bushing, providing:
- Protection CT cores — 5P / 10P class for relay protection
- Metering CT cores — 0.2S / 0.5S class for revenue metering
- Multiple ratios — up to 6 cores per bushing, field-selectable ratios
- Reduced footprint — eliminates standalone CT towers, saving up to 30% substation space
- Lower installation cost — fewer foundations, less cabling, faster commissioning
Basic or Compact — same core, different equipment.
Basic Variant
- Switching operation counter
- 19 auxiliary switch contacts (9 NO, 9 NC, 1 wiper)
- Local actuator
Compact Variant
- All Basic variant features
- Spring motor run-time monitoring
- Heating monitoring (current measuring relay)
- Light & socket outlet for maintenance
- Overvoltage attenuation
- Motor & heating circuit breakers
Where 3AP-DT delivers.
Transmission Substations
HV grid connection and bulk power transmission across national utilities.
Renewable Energy
Solar and wind farm grid integration, collection substations, storage tie-ins.
Industrial Plants
Steel, mining and petrochemical facilities requiring rugged HV switching.
Need a quote or technical support?
Share your voltage class, short-circuit current, and CT ratio requirements. Our engineering desk returns a sized proposal within 72 hours.