open61850

IEC 61850 for Python, under the Apache 2.0 licence: an MMS client (reports, report control blocks, controls), GOOSE and Sampled Values codecs, Sampled Values publication with a real-time engine, an SCL reader and a Linux capture for the process bus. The library is pure Python (standard library only, Python 3.10 or later); the optional real-time engine is in Rust.

It was written for a test and diagnostic platform of a digital substation process bus, and checked there against real IEDs (a Schneider VMC7 and an ABB SSC600). The other open-source IEC 61850 stack, libiec61850, is GPL; open61850 is an alternative for projects that cannot take a GPL dependency.

Status: alpha. The MMS client side and SV publication are what exist and what has been tested; there is no MMS server yet. Until 1.0, minor versions may change the API.

Installation

pip install open61850
pip install "open61850[rt]"    # adds the real-time SV engine (Linux wheels, x86_64 and aarch64)

What is in it

Only open61850.mms, open61850.capture and the Publisher of open61850.sv_publisher do I/O. The public names of each module are those of its __all__.

Examples

Read a value and list the logical devices:

from open61850.mms import MmsClient, ObjectName, OBJECT_CLASS_DOMAIN

with MmsClient.connect("192.0.2.10") as client:
    print(client.association.max_outstanding_calling)   # requests the IED accepts at once
    print(client.get_name_list(OBJECT_CLASS_DOMAIN))
    print(client.read(ObjectName("LLN0$ST$Mod$stVal", "IED01_LD0")))

Subscribe to a buffered report control block:

import queue
from open61850.mms import MmsClient, ObjectName, decode_report, is_report, rcb

reports = queue.Queue()
with MmsClient.connect("192.0.2.10", on_information_report=reports.put) as client:
    instances = [ObjectName(f"LLN0$BR$CB_MEAS{i:02d}", "IED01_LD0") for i in range(1, 4)]
    free = rcb.find_free(client, instances)
    rcb.enable(client, free.rcb)            # default RcbSettings: dchg, qchg, integrity, GI
    try:
        while True:
            message = reports.get()
            if is_report(message):
                report = decode_report(message)
                print(report.rpt_id, report.seq_num, [(e.index, e.value) for e in report.entries])
    finally:
        rcb.disable(client, free.rcb)       # also releases the reservation

Operate a breaker (the control model is read from the IED):

from open61850.mms import MmsClient, ObjectName, operate

with MmsClient.connect("192.0.2.10") as client:
    result = operate(client, ObjectName("CBCSWI1$CO$Pos", "IED01_BayLD"), False)   # False = open
    print(result)   # control model, ctlNum, CommandTermination, duration

A refusal raises ControlError with the AddCause of the IED.

Decode GOOSE and SV frames captured on the process bus (Linux, root):

from open61850 import goose, sv
from open61850.capture import PacketCapture

with PacketCapture("eth1") as cap:
    while True:
        frame = cap.recv()
        if frame is None:
            continue
        if (decoded := goose.decode_goose_frame(frame.data)) is not None:
            eth, pdu = decoded
            print(frame.timestamp, pdu.gocb_ref, pdu.st_num, pdu.sq_num)
        elif (decoded := sv.decode_sv_frame(frame.data)) is not None:
            eth, pdu = decoded
            print(frame.timestamp, [(a.sv_id, a.smp_cnt) for a in pdu.asdus])

Publish Sampled Values, as a merging unit or a simulator would (Linux, root):

from open61850.sv import Publisher, SvStream, Fault, three_phase

stream = SvStream(
    sv_id="MU01_SV1", app_id=0x4000, dst_mac="01:0c:cd:04:00:01", src_mac="02:00:00:00:00:01",
    waves=three_phase(i_peak=10, v_peak=100, i_lag_deg=30),               # 6I3U: Ia Ib Ic Ires In Ih Va Vb Vc
    fault=Fault(three_phase(i_peak=10, v_peak=100, ia_peak=50, va_peak=20), cycle_s=4),  # every 4 s, for 2 s
    conf_rev=1, smp_synch=2, vlan_id=100, vlan_priority=4,
)
with Publisher("eth1", rate=4800, asdus_per_frame=2, rt_priority=50) as pub:
    pub.add(stream)
    pub.start()          # at the next second: smpCnt 0 goes out on the second
    ...

Waveforms are functions of UNIX time, so several streams, processes or machines on the same clock stay in phase. With open61850[rt] the frames are sent by the Rust engine: absolute CLOCK_REALTIME deadlines, one sendmmsg per period for all streams, optional SCHED_FIFO priority and CPU pinning. Without it, a Python thread sends the same frames, with only the precision of time.sleep (tests, low rates). Measured on loopback on a Xeon server, 3 streams at 4800 samples/s, SCHED_FIFO 50: every sample sent, delay after the nominal sample time median 6 µs, 99th percentile 14 µs, maximum 46 µs over 10 s.

Command line

open61850-mms 192.0.2.10 association
open61850-mms 192.0.2.10 domains
open61850-mms 192.0.2.10 rcbs --status
open61850-mms 192.0.2.10 read 'IED01_LD0/LLN0$DC$NamPlt'
open61850-mms 192.0.2.10 dataset 'IED01_LD0/LLN0$DS_MEAS'
open61850-mms 192.0.2.10 subscribe 'IED01_LD0/LLN0$BR$CB_MEAS'
open61850-mms 192.0.2.10 operate 'IED01_BayLD/CBCSWI1$CO$Pos' open

subscribe takes a block or a group name without its instance number, picks a free instance, prints the decoded reports and releases the block on Ctrl-C.

Scope and limits

• No MMS server; GOOSE is encoded and decoded, but publishing it (retransmission scheme) is up to the application.
• SV publication sends sinusoids and periodic faults; arbitrary sample sources (replay, live measurements) are to come.
• Not implemented: file services, log control blocks and journals, setting groups, IEC 62351 security.
• The association proposes fixed calling/called AP titles and selectors by default (AssociationParameters changes them).
• Tested against two IED families so far; reports of other IEDs are welcome.

Development

python -m pip install pytest
python -m pytest

The tests need no network. The AF_PACKET capture tests run on Linux as root (sudo python -m pytest tests/test_capture.py); on another OS, docker run --rm --privileged -v "$PWD":/src -w /src python:3.13-slim sh -c "pip install pytest && python -m pytest".

Maintainer notes (what the IED captures taught, design decisions) are in AGENTS.md.

License

Copyright 2026 Florent Carli

Licensed under the Apache License, Version 2.0. See LICENSE for the full text.