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Home > Grid Automation > Protection Relays > Bus Protection > P74x

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MiCOM Agile P74x Series
Distributed Busbar Differential Relays – P741 Central Unit , P742 Peripheral Unit , P743 Extended Peripheral Unit

Part of the MiCOM P40 platform, the Agile P74x offers high performance, secure and sensitive protection for all types of busbar configurations at all voltage levels, accommodating up to 28 terminals in eight differential zones (three phase). Consisting of the Agile P741, P742 and P743 relays, the P74x platform is engineered to provide a centralized or distributed architecture with CT saturation detection, dynamic topology processing algorithms and a fast reset (less than 1 cycle) circuit breaker failure element.

Key benefits:

  • Tripping time is constant, less than 1 cycle and independent of the fault current, the substation topology and the number of feeders
  • Suitable for application on solidly grounded, impedance grounded, Petersen coil grounded and isolated systems
  • Free of charge software tools for easy scheme configuration and monitoring
  • Connection between central and peripheral units is by redundant fiber, eliminating EMC, touch and step potential issues
  • No internal batteries in GE-branded models – removes a maintenance item and eases air-freight logistics
  • Advanced binary inputs comply with the harshest norms for surge withstand, plus the ESI 48-4 EB2 standard. Spurious wiring pickup is eliminated without the use of interposing relays, external resistors or time delays. Battery/wiring faults, switching noise, and induction from long parallel circuits are tolerated without mis-operation
What's New

What's New

MiCOM P40 Agile Explorer

Enhanced Ethernet board module with switchable Ethernet redundancy delivered in a single model.

It supports PRP, HSR and RSTP in one model, allowing a single P40 model to be used in any application requiring redundant Ethernet communications. The new module is designed to handle high density traffic in the IEC 61850-8-1 network, with time latency halved. Larger architecture digital substations can also be supported, with up to 50 nodes now possible in HSR rings.

Key Features & Benefits:

  • Universal IRIG-B – Modulated and demodulated supported in the same model
  • HSR Ring – Extended to 50 node support for larger substation architectures
  • Fast performance, particularly in onerous applications such as where process bus GOOSE is used for tripping purposes


  • Typical operating time of 8ms with high speed/high break contacts, 13ms with standard contacts
  • Sensitive earth fault elements improve detection of resistive or arcing faults
  • Phase segregated biased current differential high speed busbar protection
  • Easy maintenance, operation and future expansion of the busbar supported
  • Up to 28 peripheral units supported - scalable busbar solutions from medium to large substations

Key benefits:

  • Interoperable with all classes of CT: IEEE, IEC, air-gapped, non-gapped, and CTs with moderate knee point voltage
  • True sub-cycle busbar protection - transmission class security and dependability
  • High-Availability communications - automatic self-healing on fiber disconnection between central and peripheral units
  • IEC 61850 redundant Ethernet with RSTP and IEC 62439 PRP and HSR – with HSR support for up to 50 nodes in a ring

Functional Block Diagram

Busbar protection functional block diagram

ANSI© Device Numbers and Functions

Device Number Function
87BB Bus Differential
50 Phase Definite Time Overcurrent
51 Phase Inverse-Time Overcurrent
86 Latching/Lockout Contacts
50BF CB Failure
50N Earth Fault Definite Time Overcurrent
50ST Short Zone Earth Fault
51N Neutral/Ground IDMT Overcurrent
52 Circuit Breaker Control
CTS CT Supervision
PSL Programmable Logic

MiCOM S1 Agile

Key benefits:

  • Powerful, free of charge, PC toolsuite
  • Optimum management of the installed base, structured as per the substation topology
  • Intuitive and versatile interface with file management facilities
  • Logical structure based on substation, voltage level and bay
  • Version control and cross-checking facilities for IED settings
  • Real-time measurement visualization – MiCOM S1 Agile extends to all MiCOM Agile IEDs - including P847 PMU and busbar schemes

Engineering Tool Suite

S1 Agile is the truly universal PC tool for MiCOM Agile relay, assemble all tools in a palette for simple entry, with intuitive navigation via fewer mouse-clicks. No-longer are separate tools required for redundant Ethernet configuration, phasor measurement unit commissioning, busbar scheme operational dashboards, programmable curve profiles or automatic disturbance record extraction – applications are embedded. MiCOM S1 Agile supports all existing MiCOM, K-Series and Modulex, including a utility for automatic conversion of setting files from previous generations of numerical relays like K-series and MiCOM P20 to the latest P40 Agile models.

To move to the future, with no loss of functionality, no loss of device support, and full compatibility with your installed base and system architecture – request a copy of S1 Agile with the contact form link below.

MiCOM S1 Agile software

Key features in the MiCOM S1 family:

  • GE’s integrated engineering tool that provides users with access to automation IED configuration and record data
  • Integrated configuration and monitoring features
  • Send and extract setting files
  • Event and disturbance record extraction and analysis

MiCOM S1 Agile software request

To receive the MiCOM S1 Agile, please use our Contact form. This will also ensure that you are kept up-to-date with the latest enhancements, including updates and bug fixes.

Tool & Remote HMI

MiCOM Agile P74x Busbar Topology Configuration Tool and Remote HMI Tool Features

  • Scheme editor: allows the user to define and create a P74x busbar scheme using busbar, CT, circuit breaker and isolator graphical icons
  • Synoptic: allows the user to allocate IEDs (P741, P742, P743) to the busbar scheme synoptic.
  • Dynamic synoptic: allows the user to display the P74x measured analogue quantities and DDB (digital data bus) status information via the user defined P74x scheme created using the scheme editor in accordance with downloaded embedded configuration of P74x IEDs
  • File merge: with this feature the user can automatically create the synoptic settings from above tools into a default setting file of IEDs

Refurbishment Solutions

Refurbishment Solutions – “If It’s Blue Think to Renew”

GE’s latest MiCOM P74x series models P741, P742, P743 inclusive offer an ideal path to refurbish an older installed base of MiCOM P74x relays. Whether those older products were initially sold as Alstom or AREVA-branded products, newer models retain pin-pin refurbishment capability. Advantageously, users can benefit from the advancements made in protection, control, communications, hardware and cybersecurity that have taken place in the intervening years. The new P40 retains form, fit and function compatibility but delivers the latest platform and software ready for today’s environment, and for future-proofed application for the decades ahead.

  • Take the order code (CORTEC) of the older relay being removed, typically a blue case relay
  • Translate to today’s latest GE MiCOM model, adding Ethernet options if required
  • Order the new P40 relay
  • Extract settings and logic, use S1 Agile toolsuite to convert settings
  • Detach the terminal blocks from old relay, leaving wiring attached / detach terminal blocks from the new.
  • Carefully examine the terminal blocks to see that no physical damage has occurred since installation
  • Mount new relay. Old relay blocks fit straight onto the new relay - safer, less wiring to reconnect.
  • It is recommended to apply rated current and voltage to the relay CT/VT inputs during secondary injection testing to check the continuity of the CT/VT terminal block connections to the relay.
  • Download converted files
  • Test, return circuit to service with only minutes of downtime

Contact us for advice and support