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Secure GCU-S Grid Control Unit   

The control unit supports grid-friendly tasks, making it an essential part of CLS management.  

The GCU-S is a high-security control unit for power management, smart grids, distribution grid automation, VPP / direct marketing, and facilities or infrastructures with all-IP connectivity.  

The communications paths with the SMGW and the FNN control unit are established using secure TLS connections and provide suitable protection. 

The EFR control solution enables automatic and manual control functions for necessary applications such as feed-in management and load management. The control solution can also handle flexible capacities. It is used in low-voltage and some medium-voltage systems. 


The GCU-S control unit is a member of the IP-based EFR product line dedicated to secure energy supply. The GCU-S uses the same platform as our SGH-S communications gateway and therefore has the same inherent security features. The device can be used independently or in combination with the meter system. With extensions for data acquisition and output, the GCU-S can also be used to form a secure, flexible and cost-effective remote control system.  

One of the main goals in this regard is to fill the gap in low- and medium-voltage distribution grids, most of which are not monitored or controlled.


The functionality of the GCU-S control unit extends from conventional  remote control to grid management with secure IP communications in grids with distributed generation facilities. The following features are typical: 

  • Two independent TLS-protected Ethernet IP interfaces for WAN and LAN connectivity 
  • Daisy-chained device operation  
  • Integrated security module meeting statutory requirements for gateways 
  • Four bistable 1 A changeover relays for switching purposes 
  • Configurable relay control, grouping and interlocking 
  • Up to four optoisolated digital inputs (240 V rating) 
  • 230 V AC or 24/48 V DC supply voltage  
  • Flexibly configurable functionality using dedicated profiles, particularly for communications, operating or switching schedules and security functions 
  • Role-based access control 
  • EN 61850 default user protocol 
  • Firmware upgrade over IP interfaces with WELMEC-compliant partitioning into fixed and modifiable firmware 
  • Independent protocol allocation for Ethernet interfaces by firmware upgrade 
  • Longwave broadcast channel for direct control or redundant control channel 


The scope of use of the GCU-S control unit meets or exceeds the FNN standard. It includes load and power management, facility and infrastructure control, management of distributed generation facilities, and grid management tasks in low-voltage and medium-voltage distribution grids. In particular: 

  • Heating control 
  • Load and facility management  
  • Street lighting 
  • Management of renewable energy generation in LV and MV grids 
  • Process output and control 
  • Time-critical control in LV and MV grids 
  • VPPs and direct marketing 
  • Substation automation 

Along with use as a system component, the GCU-S can be used as an independent IP terminal device or as an independent remote control receiver when connected to an active longwave antenna. In combination with the SGH-S secure gateway, the GCU-S acts as a CLS device meeting statutory requirements for controlling loads and distributed generation facilities. It is connected through the TLS-secured CLS interface to the gateway, which in turn establishes a secure connection to the relevant external party. 

Continuous advancements in distributed power generation and the growing popularity of electric vehicles create new applications for this family of devices, such as smart control of distributed storage elements and controlled charging of vehicles according to grid status. For these grid-friendly tasks, such as imbalance detection or price-sensitive switching, the GCU-S provides distributed intelligence for endpoint devices. 

The Ethernet IP interfaces can be operated independently of each other and used for different purposes: connection to the gateway as a CLS interface, daisy-chain connection with other GCU-S units, connection to external devices or systems for grid quality monitoring or other purposes, and connection to inverters. In combination with the gateway and other IP-capable devices, the GCU-S can be used in control systems for purposes such as cost analysis and allocation, or efficiency measures in building complexes. 

Target groups

  • VPP and direct marketers 
  • Grid operators and responsible meter operators 
  • Competitive meter operators 
  • Industrial applications and special applications 
  • e-Mobility 

Your contact

Paul Martin Halm

Head of Product / System Development

+49 (0)89 904 10 20 – 28


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