In an IEC 61850 substation, trips, blocking and signals between devices travel as GOOSE messages, and on the process bus currents and voltages arrive as Sampled Values. Testing a protection is no longer just injecting current and reading a contact: the test set subscribes to the relay's GOOSE, publishes the ones the relay expects and, if needed, generates the sampled values. Isolation is done with the IEC 61850 test modes and simulation.
What changes when testing with messages
In a conventional protection, the relay receives currents and voltages over wires from the instrument transformers, receives signals through contacts and trips through a contact to the breaker coil. The test set replaces the input wires and measures the output contact.
In an IEC 61850 substation automation system (SAS), some of those wires disappear:
| Signal | Conventional | IEC 61850 |
|---|---|---|
| Trip to another device, blocking, 50BF initiation | Contact and wire | GOOSE message |
| Breaker and disconnect switch position | Hard-wired auxiliary contacts | GOOSE from the bay controller or the interface unit |
| Currents and voltages | Wires from CTs and VTs | Sampled Values from the merging unit, on the process bus |
| Trip to the breaker | Relay contact | Contact or GOOSE to the breaker interface unit |
The test adapts: the test set must speak IEC 61850.
What the test set does
In general terms, a test set with IEC 61850 plays three roles:
- Subscriber. It receives the GOOSE the relay publishes (trip, pickup, alarms) and treats them as binary inputs: it measures their time and state.
- GOOSE publisher. It sends the relay the messages its logic needs: breaker position, blocking, teleprotection permissives, signals from other bays.
- Sampled Values publisher. If the relay receives currents and voltages over the process bus, the test set generates the sampled values instead of analog currents.
There are test sets that combine analog outputs and IEC 61850, and test sets dedicated to GOOSE and Sampled Values only, without conventional amplifiers. We describe them in secondary injection relay test set.
Tools that go with the test
The test set does not work alone. A message-based test usually adds the tools described in IEC 61850 test tools:
- A network analyzer, which captures the port traffic and shows each GOOSE and Sampled Value with its header, content and timing. It shows whether the relay publishes what it should even when the test set does not receive it.
- An MMS client, which reads from the relay the mode of each logical device, the simulation status and internal data, without depending on the HMI.
- The system configuration tool, to confirm in the SCD what each device publishes and receives.
The configuration comes from the SCD
To subscribe and publish correctly, the test set needs the same configuration as the system: destination MAC address, APPID, VLAN and priority, message identifier, data set and its configuration revision. That information is in the substation’s SCD file. If the test set is configured by hand and not from the current SCD, the test can pass against a configuration that no longer exists.
You can review the SCD and the addresses of each GOOSE with our free tools IEC 61850 SCL viewer and GOOSE and SV addresses.
Logical isolation: test mode and simulation
With wires, the bay is isolated by opening test blocks. With messages, IEC 61850 provides logical isolation:
- Test or test/blocked mode. The relay under test flags what it publishes with the test bit. In-service devices treat that data as invalid and do not act on it. In test/blocked, its physical outputs do not operate either.
- Simulation (LPHD.Sim). With simulation active, the relay accepts the GOOSE and Sampled Values flagged as simulated, published by the test set, and uses them instead of the real messages from the same publishers.
The usual combination is the relay in test/blocked with simulation active, fed by the test set. The details of each mode are in IEC 61850 test mode: Mod, Beh, Sim and the test bit.
- Is the relay under test in test or test/blocked?
- YesDo all in-service receivers ignore data with the test bit (verified at commissioning)?
- YesMessage-based testing is possible with the bay in service, following the approved procedure
- NoAlso isolate with physical test blocks or take the receivers out of service
- No, it is onDo not inject: its GOOSE trips are real for the other devices
What is verified, in general terms
These points are added to the conventional relay test plan:
- Each GOOSE published by the relay: it goes out with the expected content, quality and time.
- Each GOOSE received: the relay uses it in its logic and reacts correctly when the message stops arriving or arrives with invalid quality.
- Transfer times of the trip and blocking messages, which are part of the total scheme time.
- Behavior in each mode: outputs, test bit and simulation, and that everything returns to normal service at the end.
- Sampled Values, where applicable: the relay detects loss of samples or of synchronization and blocks what it should.
If a message does not arrive or arrives late during the test, the diagnosis is in GOOSE not arriving or arriving late.
We configure and test your IEC 61850 system
At Tiza Group we configure the GOOSE, the test modes and the logic of IEC 61850 relays with remote relay configuration, and we perform in the field the secondary injection testing and end-to-end testing of the complete system, in the commissioning of medium, high and extra-high voltage substations and industrial plants, in Colombia, or elsewhere on request. The system engineering is covered by our IEC 61850 specialty.
Related guides
- IEC 61850 test mode: Mod, Beh, Sim and the test bit
- IEC 61850 GOOSE: how it works, stNum, sqNum and testing
- IEC 61850 Sampled Values (SV): 9-2, 9-2LE and IEC 61869-9
- GOOSE not arriving or arriving late: causes and diagnosis
- Merging unit: IEC 61869-9, 9-2LE and testing
- Test blocks and bay isolation for testing
- GOOSE interlocking with CILO and CSWI (IEC 61850)
- GOOSE between relays of different brands
- Lost sampled values on the process bus
References
- IEC 61850-7-4, Compatible logical node classes and data object classes (LPHD.Sim, Mod and Beh).
- IEC 61850-8-1, Specific communication service mapping (SCSM) - Mappings to MMS and to ISO/IEC 8802-3 (GOOSE).
- IEC 61850-9-2, Sampled values over ISO/IEC 8802-3.
- IEC 61850-6, Configuration description language (SCL and SCD).
- IEEE C37.233-2023, Guide for Power System Protection Testing.
- OMICRON, CMC 850 brochure (GOOSE simulation and subscription and Sampled Values generation).
Frequently asked questions
Do I need a special test set to test with GOOSE?
You need a test set with the IEC 61850 function: it must subscribe to the relay's GOOSE to measure the trip time and publish the GOOSE the relay needs, such as breaker position or blocking. For relays that receive currents and voltages over the process bus, it must also generate Sampled Values.
Why doesn't the test set see the relay's trip GOOSE?
The usual causes are that the test set subscription does not match the relay's actual configuration (MAC address, APPID, GOOSE identifier, data set or configuration revision), that the VLAN does not reach the test set port, or that the relay is in a mode that does not publish what is expected. Check it against the current SCD file.
Can a GOOSE-based protection be tested with the substation in service?
Yes, if the system was designed for it: with the IEC 61850 test modes, the relay under test flags its messages and the in-service devices ignore them, and with simulation the relay uses the test set's messages instead of the real ones. It requires checking beforehand that every device interprets the modes the same way and that the mode of each IED is visible on the HMI.