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Line Protection

Home > Grid Automation > Protection Relays > Line Protection > P543, P544, P545 & P546

Related Links
  Interactive Selector Guide - Line Differential
  Interactive Selector Guide - Line Distance
  Spotlight Application
  Typical Applications
  Transmission Principles & Protection
  GSA Schedule
  Legacy Transmission Protection

MiCOM Agile P543, P544, P545 & P546
Line Differential and Distance Protection

Part of the MiCOM P40 platform, the Agile P543, P544, P545 & P546 range of transmission-class protection relays provide comprehensive line protection for differential, subcycle distance and directional earth fault applications, with 1/3 pole tripping. This range of products is ideal for HV, EHV and UHV applications on lines and cables of any length.

Key features:

  • Current transformer supervision operates with or without voltage inputs, to prevent any spurious tripping and raise the alarm
  • True subcycle distance protection with transmission class security and dependability 
  • Unparallelled speed, security and selectivity 
  • Compatible with 56/64kbps or 2Mbps for direct fiber or MUX communications channels
  • Suitable for use with equal or unequal transmit and receive path delays (eg SDH/SONET)
  • Suitable for MPLS differential channels
  • Full suite of monitoring, control and recording capabilities plus fault locator, autoreclose and check synchronism
  • Harsh environment coating as standard for all GE’s MiCOM P540 series relays protects against corrosive gases such as H2S or SO2
  • No internal batteries in GE-branded models – removes a maintenance item and eases air-freight logistics
  • NERC CIP cybersecurity
  • Binary inputs ESI48-4 EB2 compliant
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


The MiCOM Agile P543, P544, P545 & P546 range of transmission-class protection relays provide high speed current differential unit protection. They are designed for overhead line and cable applications, interfacing readily with the longitudinal (end-end) communications channel between line terminals. The interface options support direct fiber optic or multiplexed digital links.

Each of the models offer resident subcycle distance protection to complement the powerful suite of main and backup protection. Full scheme, five-zone distance protection is adopted from the class-leading MiCOMho MiCOM Agile P443. The product line becomes the standard in all HV, EHV and UHV line protection applications, duplicated where dual redundant main protection is demanded. Set any combination of differential, distance, overcurrent and reclosing, depending on the site needs. One universal relay type instead of two or more discrete models means reduced spares holding, less training, and lower cost. 

The MiCOM Agile P544 and P546 are suitable for the complex installation and feeders controlled by two circuit breakers such as breaker-and-a-half configurations with dual breaker autoreclose logic schemes with synchrocheck for both breakers.

Key benefits:

  • A universal relay that reduces spare holding - apply as a current differential relay, a distance relay, or both
  • Neutral differential boosts sensitivity of tripping for resistive earth faults, even for lines with heavy load-flow 
  • Transient biasing reduces CT knee point dimensioning by typically 25% compared to historical applications 
  • Differential protection adaptable to all different substation topologies: in-zone transformers and unequal line end CT ratios 

Main characteristics:

  • Comprehensive communication options including IEC 61850 Edition 1 and Edition 2
  • IEC 61850 redundant Ethernet, supporting self healing ring, RSTP, dual homing, PRP or HSR
  • Fast subcycle distance protection with quadrilateral or mho zones and setting free power swing detection
  • InterMiCOM64 for transmitting digital signals through teleprotection communication links
Functional block diagram

ANSI ® Device Numbers and Functions

Device Number Function
25 Check Synchronising
27 Phase and Line Undervoltage
37 Undercurrent
46 Negative Sequence Overcurrent
49 Thermal Overload
50 Phase Definitive Time Overcurrent
51 Phase Inverse-Time Overcurrent
52 Circuit Breaker Control
59 Phase and Line Overvoltage
67 Directional Phase Overcurrent
68 Power Swing Blocking
78 Out-of-Step Tripping
78DC Delta (Incremental) Protection
79 Autoreclose
Device Number Function
85 Teleprotection Channel Schemes
86 Latching/Lockout Contacts
87L Line Differentila -2 or 3 Ends
87N Neutral Differential
87T In-Zone Transformer Differential
21BL Load Encroachment/Blinder
21FL Fault Locator
21G Ground Distance
21P Phase Distance
46BC Broken Conductor
50/27 Switch-on to Fault
50BF CB Failure
50N Earht Fault Definite Time Overcurrent
50ST Stub Bus Protection
Device Number Function
51N Neutral/Groud IDMT Overcurrent
59N Neutral Voltage Displacement
59R Remote End Overvoltage
64N Restricted Earth Fault
67N Directional Neutral/Ground Overcurrent
81df/dt Rate of Change of Frequency
81O Overfrequency
81U Underfrequency
CTS CT Supervision
PSL Programmable Logic
SEF Sensitive Earth Fault
TCS Trip Circuit Supervision
VTS VT Supervision

MiCOM Agile P54x Models

P543 Line-Differential with Optional Subcycle Distance IED, in 60TE case

Buy Now

P544 Line-Differential with Optional Subcycle Distance IED, in 60TE case, suitable for two circuit breakers such as breaker-and-a-half. P544 is under last-time buy. Orders may be placed until  30th June 2024 and will be fulfilled based upon availability. As an alternative, please refer to P54.

Buy Now

P545 Line-Differential with Optional Subcycle Distance IED, in 80TE case

Buy Now

P546 Line-Differential with Optional Subcycle Distance IED, in 80TE case, suitable for two circuit breakers such as breaker-and-a-half

Buy Now

MiCOM S1 Agile

Key benefits:

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:

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 - "If it's Blue Think to Renew"

GE’s latest MiCOM P540 series models offer an ideal path to refurbish an older installed base of MiCOM P540 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.

Pin-Pin Upgrade Methodology:

LFCB and MITZ Replacement: