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Generator circuit-breaker HEC 9 for 250-300 kA

The world’s largest generator circuit-breaker (GCB)

HEC 9 has been developed as a system for large-sized power plants such as nuclear, coal-fired and hydropower plants. It has the world's highest performance with short-circuit currents up to 300 kA and it is also highly suitable for retrofits or replacements of old GCBs in air-blast technology.

Based on Hitachi Energy's well-proven and highly reliable SF6 technology, it enables lower lifecycle costs and gives a time-to-overhaul period of up to 20 years.

It is delivered in single-phase systems to facilitate the transportation and installation with plug-in design to minimize the activities at the site. Besides circuit-breaker, disconnector, capacitors and control cubicle, it also includes a wide selection of additional components such as earthing and starting switches, current and voltage transformers and surge arresters.


  • Load current up to 33,500 A
  • Power units up to 2000 MW
  • Indoor or outdoor installations
  • Replacements or retrofits of old units

Why Hitachi Energy?

  • Naturally cooled up to 28,500 A
  • Delivers the highest performance rates
  • Provides the lowest lifecycle costs - maximum system availability and reliability
  • Based on SF6, it is the only alternative to old and obsolete GCBs in air-blast technology
  • Fully type tested according to IEEE C37.013, the worldwide GCB standard
Available options:

Brief performance data

System Type HEC 9-250L HEC 9-250XL HEC 9-300L HEC 9-300XL
Rated maximum voltage [kV] 31.5 31.5 31.5 31.5
Rated frequency [Hz] 50 / 60 50 / 60 50 / 60 50 / 60
Rated power frequency withstand voltage [kV] 80 80 80 80
Rated lightning impulse withstand voltage [kV] 150 150 150 150
Rated short-circuit breaking current [kA] 250 250 300 300
HEC 9 with 50 Hz *)        
Rated normal current [A]: natural cooled up to 28,500
(naturally cooled)
up to 33,500
(enhanced convection)
up to 28,500
(naturally cooled)
up to 33,500
(enhanced convection)
HEC 9 with 60 Hz *)        
Rated normal current [A]: natural cooled up to 26,500
(naturally cooled)
up to 32,500
(enhanced convection)
up to 26,500
(naturally cooled)
up to 32,500
(enhanced convection)
*) with IPB longitudinal forced air cooling up to 57,000   up to 57,000  

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