Welcome to COSI range


Compact Optical Sensor Intelligence

Alstom Grid Instrument Transformers is ahead of the competition thanks to its innovative, patented Optical Instrument Transformer technology. It enables full IEC 61850 implementation and sets the benchmark in transmission network architectures for today’s and tomorrow’s electricity networks and Smart Grids.

Our comprehensive COSI range includes a full offer of Optical Instrument Transformers for AC or DC applications with the following innovative products:

COSI-CT | Optical Current Transformer (AC or DC)

COSI-MU | Merging Unit

COSI-CM | Combined Metering Unit

COSI-CT F3 | Flexible Optical Current Transformers

Our technology is based on the effects of light influenced by current (Faraday effect) to measure current. Our technology is suitable for use in AC or DC transmission systems.

The transformer can also be used in highcurrent DC applications, such as large scale aluminum electrolysis companies.

COSI-CT can also be applied in HVAC systems with a rated voltage of up to 1200 kV or HVDC systems with a rated voltage of up to 800 kV. The equipment can make precise measurements within a range between 1 A and 4800 A. The protective current is up to 216 kA (peak value) and the bandwidth is DC 20 kHz.