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Electrical system protection

Electrical system protection is one of the most important aspects of system design and operation. The move from aging electromechanical and electronic relays to modern, fully integrated protection and control devices takes a great deal of understanding to optimise and to maximise the benefits for the operator.

We carry out protection engineering for transmission networks, generation plants connected to grids, large and small industrial users, and distribution companies.


Mott MacDonald provides these services:

  • Generation protection: thermal, hydro, wind, and novel prime movers
  • Industrial system protection
  • Integrated control and protection for transmission and distribution systems
  • Relay coordination studies, detail scheme design, philosophy statements
  • Commissioning, reviews, and retrofits
  • Specialist protection schemes

We carry out protection engineering for transmission networks, generation plants connected to grids, large and small industrial users, and distribution companies.

Protection systems can vary from simple to extremely complex. Modern electronic relays can be part of an overall protection and control system, acting as remote terminal units and control points as well as protection in both large substations and the wider network.


Mott MacDonald has extensive experience in all aspects of protection for the following:

  • Cables
  • Industrial generation
  • Industrial networks
  • Main generation plants
  • Offshore networks
  • Specialist applications
  • Substations up to 500kV
  • Transmission lines
  • Utility distribution systems
  • Wind farms


Our proven capability in all aspects of protection design, application, and commissioning management has been developed over many decades. Whether the project is to extend existing transmission, distribution or generating stations, or for greenfield development, our global resources enable us to specify, design, and provide settings for the installation.

We have experience in all distribution and transmission voltages up to 500kV, employing either traditional discrete relays or intelligent multifunction devices. Our protection specialists support our substation and network projects and run their own projects where protection or protection and control are the only issue.

Our protection engineers are skilled in the following:

  • Application engineering/relay setting calculations
  • Arc flash analysis
  • Associated control functions, including auto switching schemes, transformer automatic AVC projects and interlocking systems
  • Fault analysis
  • Multifunction relay configuration
  • Protection philosophy definition and policy creation
  • Protection upgrading/refurbishment in existing substations
  • Relay coordination
  • Relay scheme design/equipment technical specification
  • Reliability assessment
  • Specification of commissioning requirements
  • Substations up to 500kV
  • System fault studies
  • System protection design

Customer benefits

We fully understand the substation and system operation required to maximize the benefits and deliver correct definition and settings.

We use suitable setting software where appropriate, but always carry out checks by other means to deliver suitable and safe solutions. Our power system modeling service covers the load and fault level computations needed to enable protection systems to be defined and relays set.

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