IEC 61850 Protection Testing

IEC 61850 is the global standard for communication networks and systems in substations. As utilities transition from copper wiring to digital process buses, protection testing methods must evolve. VA-TEK’s relay test sets are analog secondary-injection instruments: they test a relay through its conventional current and voltage inputs, which is how the large majority of installed relays are still proven. Full process-bus testing needs a dedicated IEC 61850 test set, which VA-TEK does not currently offer — this page explains what that work involves so you can specify the right tool.

Conventional vs. Digital Substations

In a conventional substation, protection relays receive analog current and voltage signals via copper cables from instrument transformers (CTs/VTs). Testing involves injecting analog signals directly into the relay terminals.

In an IEC 61850 digital substation, CTs and VTs are replaced or complemented by non-conventional instrument transformers (NCITs) or merging units (MUs) that publish digitized Sampled Values (SV) onto the process bus. Relays subscribe to these SV streams over Ethernet — there are no analog terminals to inject.

GOOSE Messaging

GOOSE (Generic Object-Oriented Substation Event) replaces conventional hard-wired binary signals between IEDs with high-speed Ethernet multicast messages. GOOSE carries trip commands, interlock signals, blocking signals, and breaker status information. Testing GOOSE-based schemes requires a test set that can both subscribe to GOOSE messages (to monitor scheme behavior) and publish GOOSE messages (to simulate IEDs that are not physically present).

Sampled Values (SV)

Sampled Values per IEC 61850-9-2LE transmit digitized current and voltage waveforms over Ethernet at 80 samples/cycle (4 kHz for 50 Hz systems, 4.8 kHz for 60 Hz). Testing a relay’s SV subscriber function means publishing calibrated SV streams to its Ethernet port — the functional equivalent of injection, carried over the process bus instead of copper. That requires a test set with native IEC 61850-9-2LE publishing.

Testing Scenarios

Three scenarios appear in the field. VA-TEK relay test sets cover the first two; the third needs different equipment.

Scenario 1: Conventional Relay Testing

Inject analog currents and voltages directly. Monitor binary outputs and GOOSE messages simultaneously. Standard approach for relays in conventional bays.

Scenario 2: Hybrid Testing

Inject analog signals into the relay while also subscribing to and publishing GOOSE messages on the station bus. Common in retrofit projects where digital communications overlay existing copper wiring.

Scenario 3: Full Digital (SV Injection)

Stream Sampled Values to the relay over Ethernet. Monitor GOOSE outputs and MMS reports. No analog connections required. Typical for new-build digital substations. This scenario needs an SV-capable test set; VA-TEK’s current relay test sets cover Scenarios 1 and 2.

For the analog side of the same work see the VAE-660 and VAE-430 relay test sets; for the digital side, our guide to IEC 61850 substation testing.