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Line Protection

Home > Grid Automation > Protection Relays > Line Protection > P443, P445, P446

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

MiCOMho Agile P443, P445, P446
Distance Protection Relays

Part of the MiCOM P40 platform, the MiCOMho Agile P443, P445 and P446 relays operate with advanced load blinding and disturbance detection techniques, such as power swing blocking, to ensure stability when no tripping is required. Whether protection is required for lines, cables or hybrids of grounded transmission and distribution circuits, the MiCOMho Agile P443, P445 and P446 relay characteristics allow for versatile deployment.

Key features:

  • MiCOM P443 & P446: True subcycle distance protection with transmission class security and dependability
  • Unparalleled speed, security and selectivity
  • Extremely versatile logic capabilities, managing leader-follower autoreclosing and check sync schemes in dual breaker applications
  • Transmission-class circuit breaker failure protection for one or two breakers. The breaker failure protection may be initiated from internal protection within the relay or from external devices
  • Single-pole and 3-pole breaker operation is supported, with independent supervision and condition monitoring statistics for each pole
  • Trip circuit supervision, control and interlocking schemes can be designed via graphical support software
  • 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


Transmission and distribution systems are essential for the safe, sure routing of power from generation sources to consumers. However, exposed overhead lines transporting power are by nature sometimes vulnerable and prone to fault. In the case of a faulty circuit, the Agile range provides speedy protection to trip and isolate it, thereby preventing further damage.

Each relay model contains multiple main protection elements: distance, delta directional incremental protection and directional earth/ground fault unit protection (DEF). This permits simplified application and spares holdings, because the relay can be adopted as the standard protection platform. 

The MiCOMho Agile P443 and P445 are suitable for feeders controlled by a single circuit breaker. The MiCOMho Agile P446 is suitable for complex installations where feeders are controlled by two circuit breakers such as ring bus/mesh corner formations and the breaker-and-a-half configurations. 

Key benefits:

  • P443 and P446: Sub-cycle fault clearance from 0.7 to 1 cycle
  • Simple set mode: The relay determines its own settings from protected line data
  • Power swing blocking without the need for setting
  • Integral teleprotection via a MODEM, fiber or MUX channel
  • Fast CB failure resetting (<3/4 cycle)
  • Phase-preference tripping for cross-country earth faults in Petersen/isolated systems (P443 version 92)
Feeder Management

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
86 Latching/Lockout Contracts
Device Number Function
78DC Delta (Incremental) Protection
79 Autoreclose
85 Teleprotection Channel Schemes
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 Earth Fault Definite Time Overcurrent
50ST Stub Bus Protection
Device Number Function
51N Neutral/Ground 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 P443 Subcycle Distance & Delta Incremental Protection

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MiCOM P445 Subtransmission Economy Distance Protection

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MiCOM P446 Dual Breaker Subcycle Distance & Delta Protection

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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

GE’s latest MiCOM P440 transmission models offer a perfect functional match to our “mho” family of distance relays, from the heritage installed-base brands GEC Measurements, GEC Alsthom, Alstom and Areva. The subcycle pedigree is maintained, optimised and advanced:

SHNB Micromho and SHPM Quadramho Replacement:

LFZP Optimho and LFZR Replacement:

LFDC Delta Directional Comparison Relay Replacement: