OMICRON CMC 850: IEC 61850 Protection Testing

Short answer

The OMICRON CMC 850 is a protection test set dedicated to IEC 61850: it communicates with the devices under test through GOOSE and Sampled Values, without the conventional binary inputs and outputs or amplifiers. It is controlled with Test Universe, includes the CMIRIG-B interface for time synchronization and comes with its own functions accessible from a browser.

What it is and where it is used

The OMICRON CMC 850 is, according to its manufacturer, the protection test set dedicated to IEC 61850: instead of connecting test leads to relays, it interacts with them through GOOSE and Sampled Values, the real-time messages of the digital substation. It is controlled with OMICRON’s Test Universe software and is used in IED development and evaluation, in system factory acceptance tests, in commissioning, in demonstrations and in acceptance tests.

The digital substation and its architecture are in IEC 61850 digital substation; the messages in IEC 61850 GOOSE and Sampled Values. How to test a protection that receives its data over the network is in protection testing with GOOSE.

Versions, package and accessories

Item	What it is	Note
CMC 850	Test set	1.7 kg; 85 × 145 × 325 mm; two 10/100 Ethernet ports with Power over Ethernet (PoE), USB port, low-level analog outputs
CMIRIG-B	Synchronization interface	Delivered with the set; synchronizes with IRIG-B or with a pulse-per-second (PPS) signal
CMC 850 package	Set plus software	Includes IEDScout, OMICRON Control Center, GOOSE and Sampled Values configuration modules, QuickCMC and State Sequencer
CMGPS 588	OMICRON GPS clock	Can be connected over Ethernet; mentioned as a time reference option

The CMC 850 is compatible with the whole Test Universe suite, so the protection test modules can be used, and test plans with GOOSE and Sampled Values made for other CMC sets can be reused. With its 12 low-level analog outputs it can control external amplifiers.

Main functions

GOOSE: simulation and subscription of up to 360 inputs and outputs.
Sampled Values: up to three streams generated with Test Universe; the manufacturer states that four can be generated with RelaySimTest.
Synchronization: by IRIG-B or PPS through the CMIRIG-B, and by NTP or PTP to time-stamp GOOSE messages and synchrophasors. The 2018 brochure cites PTP per IEEE 1588-2002 (V1); more recent manufacturer documents refer to the profiles of IEC 61850-9-3 and IEEE C37.238.
Traffic separation: two Ethernet ports make it possible to keep substation data separate from the control commands of the set.

Built-in functions accessible from a browser

Besides control from Test Universe, the CMC 850 includes its own functions that are accessed with any browser:

receiving Sampled Values and showing them in a multimeter view and an oscilloscope view;
calculating phasors from the subscribed Sampled Values and publishing them with the IEEE C37.118 protocol;
synchronizing with network time sources (NTP or PTP);
replaying saved network traffic in PCAP format;
querying system information.

These functions also make it an observation tool: seeing what a merging unit is publishing, for example, without needing more equipment.

What tests it allows

Testing protections fed by Sampled Values. The set replaces the analog current and voltage signals with network messages that the relay processes as if they came from the instrument transformers.
Testing logic and interlocks over GOOSE. The messages of neighboring devices are simulated and the reaction of the device under test is verified.
IED and system evaluation. Checking that each publication and subscription in the configuration file (SCL) works as designed.
Observing network data. To locate a missing or faulty stream, it helps to analyze the traffic with Wireshark and review the SCL file; the IEC 61850 SCL viewer tool shows who publishes and who subscribes.

When the test includes relays with analog inputs, the CMC 850 is complemented with a conventional injection set or with external amplifiers.

Precautions and common mistakes

MAC address, APPID or VLAN that do not match. It is the most frequent cause of “the relay does not see the stream”; the GOOSE and SV addresses tool helps validate them.
No time reference. Testing without a common synchronization can produce quality losses or phase differences that are not the fault of the device under test.
Test mode of the device. Devices under test usually require test or simulation mode to accept messages with the simulation flag; see test mode and simulation in IEC 61850.
Network load. Sampled Values streams take up bandwidth; see Sampled Values and GOOSE bandwidth.
Legacy plans. A plan made for another CMC is reused, but check that the GOOSE and Sampled Values modules match those of the package.

Frequently asked technical questions

Manual and software: OMICRON provides the manual and updates to its customers; the figures in this sheet are from the public brochure (October 2018) and may have changed in recent versions.
Relationship with the CMC 500: the CMC 500 incorporates the IEC 61850 interfaces in a set with voltage and current outputs; the CMC 850 is limited to the network. Both are described in their own sheets.
What to read before using it: tests with Sampled Values require handling IEC 61850, SCL configuration and network time; the guide on IEC 61850 test tools summarizes them.

How we help

Do you need this test? We do it for you: depending on your case we recommend the right test and test set and include it in the quote. That way you run the test your case really needs, without paying for tests you do not need. On site, this work is done in Colombia, or elsewhere on request.

See the scope in secondary injection and in testing and commissioning, or tell us about your case through contact.

References

IEC 61850-8-1 (GOOSE) and IEC 61850-9-2 (Sampled Values); IEC 61850-6 (SCL); IEC 61869-9.
IEEE C37.118, synchrophasors; IEEE 1588, precision time protocol.
OMICRON, brochure “CMC 850: the protection test set dedicated to IEC 61850”, October 2018.

Frequently asked questions

What is the OMICRON CMC 850 used for?

To test protection and control devices that communicate over IEC 61850: it simulates and subscribes to GOOSE messages, generates Sampled Values streams and records the response of the device under test. It is useful in IED development and evaluation, in system factory acceptance tests and in the commissioning of digital substations.

Can the CMC 850 replace a CMC 356 or a CMC 500?

Not for every test. The CMC 850 has no amplifiers or conventional binary inputs: it only works where the device under test receives signals over the network. For relays with analog inputs you need a set with amplifiers, or external amplifiers controlled by its low-level outputs.

Why is time synchronization so important in these tests?

Because Sampled Values and GOOSE events carry a time stamp and the devices of the digital substation compare streams from different sources. If the test generator and the device under test do not share a common time reference, the result may show synchronization faults that are not the device's.