Medium-voltage vacuum replacement circuit breaker for generator applications (GCB)

Author: Jerrod Overcash


Improve reliability and reduce operation and maintenance expenditures with a new line-up of medium-voltage vacuum replacement generator circuit breakers.

With minimal operational and maintenance expenses adding up to significantly lower lifecycle costs, replacing your old gas and airblast generator circuit breakers (GCBs) with new vacuum generator circuit breakers provides a quick and easy return on your investment. Siemens has combined its vacuum generator circuit breaker product line with nearly 40 years of experience in the replacement circuit breaker market to create custom engineered, vacuum replacements for aging SF6 and airblast generator circuit breakers.


A Siemens direct replacement vacuum solution not only allows you to preserves the investment in your existing switchgear but also eliminates expensive overhauls and major rebuilds throughout the lifecycle of your circuit breaker.


As outlined in IEC/IEEE 62271-37-013, generator circuit breakers have to handle a special set of conditions beyond that of standard distribution breakers including:

  • Very high rated and short-circuit currents

  • Very high DC components of up to 130% with delayed current zeros

  • High peak currents

  • Very high Rate of Rise Recovery Voltage (RRRV) and Transient Recovery Voltage (TRV).

The strong constant dielectric properties and extremely quick rate of recovery of the Siemens vacuum interrupter means Siemens vacuum generator circuit breakers can meet or exceed all of these requirements and completely fulfill the TRV requirements without the need for additional capacitors.


The installation process for new Siemens replacement generator circuit breakers is simple and occurs in three easy steps:

  1. The existing gas or airblast circuit breaker is removed from the cell.

  2. The new Siemens vacuum circuit breaker is installed and inserted directly into the existing cell, requiring minimal adjustments in the field.

  3. The breaker is then able to connect to the existing bus and is ready to put into service.

Siemens vacuum solutions are available for many OEM brands such as ABB, GE, Alstom, Hitachi, and more. Solutions utilize Siemens 3AH operating mechanism, which is the core operating mechanism for all Siemens medium-voltage circuit breakers. Implementation of the newest 3AH36 operating mechanism in an isolated phase HB3 generator circuit breaker produces ratings for vacuum generator circuit breakers reaching 24kV, 100kA, and up to 12,500 A.


All Siemens generator circuit breakers are type tested to the unified IEC/IEEE 62271-37-013 standard and are capable of up to 50 full fault interruptions with an expected service life of up to 30,000 operations.

Siemens vacuum generator circuit breaker technical characteristics compared to standard distribution circuit breakers

Major technical characteristics
Distribution circuit breaker
Generator circuit breaker
IEC 62271-100
IEC/IEEE 62271-37-13
TRV amplitude factor
TRV rate (at 100MVA)
0.41 kV/µs
4.0 kV/µs
Peak s.c. making current (at 60Hz)
2.6 x I sc (2.5 x at 50 Hz)
2.74 x I sc
Short-time current duration
1s (optional 3s)

Siemens vacuum generator circuit breaker technical characteristics compared to typical gas generator circuit breakers

Comparison of generator breaker types
Siemens Vacuum GCB
Typical GCB
Operating cycles at rated current
Interruptions at 100% rated short circuit current
30 (≤ 80 kA ); 50 (≤ 50 kA)
Monitoring of arc quenching medium
not required
Capacitors to withstand the TRV rate
not required
Use of green house gases / toxic decomposition products
no / no
yes / yes

For an in-depth view of medium-voltage generator applications, refer to Siemens TechTopics No. 44, No. 71, and No. 73.

Mailing address

Siemens Industry, Inc.

7000 Siemens Road

Wendell, North Carolina 27591

United States