open61850

IEC 61850 for Python, under the Apache 2.0 licence: an MMS client (reports, report control blocks, controls), GOOSE and Sampled Values codecs, supervision of GOOSE and SV streams, Sampled Values publication with a real-time engine, an SCL reader, pcap/pcapng files 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, GOOSE and SV publication and supervision, SCL and COMTRADE are what exist; each is tested, against two IED families and, in CI, against libiec61850. 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 publishers (GoosePublisher, SV Publisher) do network I/O; open61850.pcap reads and writes files. The public names of each module are those of its __all__.

Examples

Discover the data model and read values by their IEC 61850 reference:

from open61850.mms import MmsClient, discover

with MmsClient.connect("192.0.2.10") as client:
    print(client.association.max_outstanding_calling)   # requests the IED accepts at once
    model = discover(client)                             # logical devices, nodes, data, control blocks
    for ref in model.references(fc="MX"):
        print(ref)                                       # IED01_LD0/MMXU1.TotW.mag.f [MX]
    print(client.read("IED01_LD0/LLN0.Mod.stVal[ST]"))  # same as "IED01_LD0/LLN0$ST$Mod$stVal"
    ref = model.resolve("IED01_LD0/MMXU1.TotW.mag.f")    # the FC found in the model
    print(ref, client.read(ref))

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, operate

with MmsClient.connect("192.0.2.10") as client:
    result = operate(client, "IED01_BayLD/CBCSWI1.Pos", 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])

Supervise the GOOSE and SV streams of a Wireshark capture, on any OS (the same code takes the frames of PacketCapture live):

from open61850.pcap import read_pcap
from open61850.supervision import BusSupervisor, EventKind, SvSupervisor

bus = BusSupervisor(sv_supervisor=SvSupervisor(sample_rate=4800))
for frame in read_pcap("bus.pcapng"):
    for event in bus.feed(frame):
        if event.kind is not EventKind.NEW_STREAM:
            print(event)        # 1790000002.209167 MU01_SV1 gap: smpCnt 999 -> 1004
print("\n".join(bus.summary()))

GooseSupervisor and SvSupervisor take decoded messages and a reception time, and keep only state: an application can feed them from its own receive loop.

Take a GOOSE control block from an SCL file, or check an IED against its SCL:

from open61850 import scl
from open61850.mms import MmsClient, discover
from open61850.mms.model import compare

(ied,) = scl.load_ieds("IED01.cid")
control = ied.goose_controls[0].goose_control(src_mac="02:00:00:00:00:01")   # for GoosePublisher
with MmsClient.connect("192.0.2.10") as client:
    print(compare(scl.load_model("IED01.cid"), discover(client)))              # [] when they match

Publish a GOOSE control block, as a protection relay would (Linux, root):

from open61850.data import BoolData
from open61850.goose_publisher import GooseControl, GoosePublisher

control = GooseControl("IED01_LD0/LLN0$GO$gcbTrip", "IED01_LD0/LLN0$DS_TRIP", app_id=0x0001,
                       dst_mac="01:0c:cd:01:00:01", src_mac="02:00:00:00:00:01", min_time_ms=4, max_time_ms=1000)
with GoosePublisher("eth1", control, [BoolData(False)]) as pub:
    pub.start()                      # stNum 1, repeated every second once settled
    ...
    pub.publish([BoolData(True)])    # trip: stNum 2, sent at once, then after 4, 8, 16... ms

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
    ...

Recorded samples can replace the waveforms: a stream captured from a merging unit, or a fault record in COMTRADE, resampled to the publisher's rate. A Playback starts at a given second (by default when the publisher starts), once or every few seconds; both engines send it.

from open61850.comtrade import load_comtrade
from open61850.sv import Playback

record = load_comtrade("fault.cfg")
stream.playback = Playback.from_comtrade(
    record, ["IA", "IB", "IC", None, None, None, "VA", "VB", "VC"], rate=4800,
    scales=[w.scale for w in stream.waves], repeat_s=10,    # 9-2LE units: mA and 10 mV
)

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 browse IED01_LD0 --types
open61850-mms 192.0.2.10 browse --fc MX --flat
open61850-mms 192.0.2.10 compare-scl IED01.cid
open61850-mms 192.0.2.10 rcbs --status
open61850-mms 192.0.2.10 read 'IED01_LD0/LLN0.NamPlt[DC]' 'IED01_LD0/LLN0$ST$Mod$stVal'
open61850-mms 192.0.2.10 dataset IED01_LD0/LLN0.DS_MEAS
open61850-mms 192.0.2.10 subscribe 'IED01_LD0/LLN0$BR$CB_MEAS'
open61850-mms 192.0.2.10 operate IED01_BayLD/CBCSWI1.Pos open

compare-scl station.scd --ied IED01 lists what the IED lacks or has more than its SCL (logical devices and nodes, attributes, control blocks, data sets). browse prints the data model (logical devices, logical nodes, data objects with their attributes and functional constraints, control blocks, data sets), with --flat one reference per line.

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.

sudo open61850-sv eth1 02:00:00:00:00:01 01:0c:cd:04:00:01 MU01_SV1 --appid 0x4000 --conf-rev 1 \
  --smp-synch 2 --vlan-id 100 --vlan-priority 4 --i-peak 10 --v-peak 100 --phase 30 \
  --fault --fault-i-peak 50 --fault-v-peak 20 --fault-cycle 4 --rt-priority 80

open61850-sv publishes one SV stream until stopped (--duration to stop by itself, --dump to print one frame). --replay-pcap FILE --replay-svid ID replays a captured stream, --comtrade FILE.cfg --comtrade-channels IA,IB,IC,,,,VA,VB,VC a fault record, with --replay-delay and --replay-repeat in seconds.

echo true | sudo open61850-goose eth1 02:00:00:00:00:01 01:0c:cd:01:00:01 'IED01_LD0/LLN0$GO$gcbTrip' \
  'IED01_LD0/LLN0$DS_TRIP' false --appid 0x0001 --vlan-id 100

open61850-goose publishes one GOOSE control block with the initial values given, then one new state per line read on standard input.

open61850-supervise capture.pcapng --events --sample-rate 4800
sudo open61850-supervise --live eth1

open61850-supervise prints a line per stream (messages or samples, rate, missed, events), with --events every event of a file; with --live it prints events as they happen and the summary on Ctrl-C.

Scope and limits

• No MMS server.
• SV publication sends sinusoids, periodic faults and recorded samples (captures, COMTRADE); samples computed live by the application 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 (Schneider VMC7, ABB SSC600) and, in CI, against libiec61850's example servers, publishers and subscriber (model, reads, reports, the four control models, GOOSE both ways, SV); reports of other IEDs are welcome.

More examples

examples/ has short programs, each runnable as it is and run in CI against libiec61850:

Development

python -m pip install pytest
python -m pytest

The tests need no network. tools/interop/run.sh runs the interoperability tests against libiec61850's example programs in Docker (libiec61850 is only run there, as a peer, never linked or shipped). 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".

How to contribute is in CONTRIBUTING.md; maintainer notes (what the IED captures taught, design decisions) in AGENTS.md.

License

Copyright 2026 Florent Carli

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