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Transformer Protection

Home > Grid Automation > Protection Relays > Transformer Protection > P64x

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  Legacy Transformer Protection

MiCOM Agile P640 Series
Transformer Protection Relays - P642, P643, P645

Part of the MiCOM P40 platform, the Agile P64x transformer protection relays helps preserve transformer service life and provides fast protection for transformer faults. The platform consists of three model variants (P642, P643 and P645) that cover two and three-winding transformers (including auto-transformers), with up to five sets of 3-phase CT inputs, and offers high and low impedance restricted earth fault, and has integral asset management capability.

Key features:

  • High stability during external fault with heavy CT saturation due to transient bias technique
  • No slow-down of differential elements due to 2nd harmonic component in fault currents
  • Adaptable to transformers with considerable CT mismatch between terminals – matching factor up to 20
  • Current transformer supervision operates with or without voltage inputs, fast enough to prevent any spurious tripping and alarm 
  • 10 integrated function keys, tri-color LEDs, and graphical programmable logic permit the creation of comprehensive, tailored schemes
  • No internal batteries in GE-branded models – removes a maintenance item and eases air-freight logistics
  • Supports all major digital control system protocols, easing integration into DCS, SCADA and engineering workstations
  • NERC CIP cybersecurity
  • Binary inputs ESI48-4 EB2 compliant
  • Harsh environment protection extends the life of the product
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


Transformers are high capital assets in electrical power systems. Elimination of all electrical and mechanical stresses, although desirable to preserve transformer life, is impractical. Adaptive techniques to measure, alarm (or trip) and advise on cumulative service can help to schedule preventive maintenance before a costly failure occurs. Internal faults are a risk for all transformers, with short-circuits dissipating the highest localized energy. Unless cleared quickly, the possibility to rewind windings reduces and core damage may become irreparable.

GE's P642, P643 and P645 address all these issues, preserving service life and offering fast protection for transformer faults. A transient bias technique has been included, enhancing relay stability and CT requirements. Hosted on an advanced IED platform, the P64x incorporates differential, REF, thermal, and overfluxing protection, plus backup protection for uncleared external faults. Model variants cover two and three-winding transformers (including auto-transformers), with up to five sets of 3-phase CT inputs.

Key benefits:

  • Backup and logging of through faults 
  • Simple settings – wizard requires only nameplate data 
  • Integrated backup overcurrent per winding or CT input - optional directionalizing when relay fitted with a 3-phase VT  
  • Ordering the 3-phase VT permits full monitoring and measurement of power and energy quantities 

Main characteristics:

  • Current loop analogue inputs [CLIO] and analogue outputs [RTD] for remote monitoring 
  • Optional single or dual redundant Ethernet available for IEC 61850 or DNP3
  • Transient biasing reduces CT knee point dimensioning by typically 25% compared to historical applications
Functional block diagram


ANSI ® Device Numbers and Functions

Device Number Function
24 Overfluxing
27 Undervoltage
46 Negative Sequence Overcurrent
47 Negative Sequence Overvoltage
49 Thermal Overload
50 Phase Definite Time Overcurrent
51 Phase Inverse-Time Overcurrent
52 Circuit Breaker Control
59 Overvoltage
67 Directional Phase Overcurrent
Device Number Function
68 Inrush Detection
89 Latching/Lockout Contacts
50BF CB Failure
50N Earth Fault Definite Time Overcurrent
51N Neutral/Ground IDMT Overcurrent
51R Voltage Restrained Overcurrent
51V Voltage Controlled Overurrent
59N Neutral Voltage Displacement
64N Restricted Earth Fault
67N Directional Neutral/Ground Overcurrent
Device Number Function
81O Overfrequency
81U Underfrequency
87T Transformer Differential
CLIO Current Loop Transducer I/O
CTS CT Supervision
LoL Loss of Life
PSL Programmable Logic
RTD Temperature Measurement
TCS Trip Circuit Supervision
Thru Through Fault Monitoring
VTS VT Supervision

Agile P64x Models

P642 2 Winding transformer management IED

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P643 3-End transformer management IED

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P645 5-End transformer management IED

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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.

Refurbishment Solutions

GE’s latest MiCOM P640 models offer a perfect functional match for our MBCH and KBCH family of transformer differential relays, from the heritage installed-base brands GEC Measurements, GEC Alsthom, Alstom and Areva:


  • Same 4U rack mounting format
  • KBCH, P642/P643/P645 share the same S1 Agile PC toolsuite
  • Contact us for advice and support