Testing of IEC 61850 Sampled Value based Devices and Systems

Author:Alexander Apostolov, USA

Testing of IEC 61850-9-2 Based IEDs

The testing of different functions in IEDs that are based on sampled measured values can be achieved in a couple of different ways depending on the requirements of the specific test. One approach is acceptable when testing the IED only, while another can be used if the testing includes the complete MU/IED system. The difference is that in the first case there is no hard wiring between the test device and the tested IED – i.e. the test system can be communications based only.

The key component of this module is the Merging Unit simulator described earlier. It will have to take the waveforms generated from the Network Simulator and then format them in the required 80 samples/cycle and multicast the individual sampled values to the LAN 80 times per cycle (e.g. 80 messages/cycle) (Figure 6(a)).

The testing of different types of functions available in the IED will be similar to the testing of conventional hardwired or hybrid devices. The only difference is that an Ethernet link is used instead of a hardwired interface between the test device and the IED under test. This applies to both the configuration and analysis modules of the test system (See page 46).
In order to gain confidence that the performance of IEC 61850 Sampled values applications is similar to the performance of conventional hardwired devices of the same model the test system should be able to simultaneously apply the simulated analog signals to the hardwired IED and the corresponding sampled values to the IED with the SV interface. The GOOSE messages from both IEDs are received by the test devices and used to evaluate their performance (Figure 6(b)).

If we are testing the protection IED that is interfacing with a merging unit as a system, the test device will apply the simulated analog signals to the merging unit which will then publish the sampled values. The IED subscribes to these sampled values and publishes the GOOSE messages when it operates. These GOOSE messages are then used by the testing tool to evaluate the performance of the tested protection function based on the expected operating time..

The test system needs to subscribe to and monitor the GOOSE messages received from the tested IED that represent the operation of the tested functional elements in order to determine if the devices operated as required. If the tested device has relay outputs as well, they will have to be wired into the test device and their operation will be compared with the received GOOSE messages to determine if the performance of communications based solutions is similar to the hard-wired case.
The test system may also retrieve the waveform records from the tested device and again compare them with the original waveforms from the simulation tool. Figure 6(c) shows the system configuration for hybrid testing of IEDs that have relay outputs and at the same time support GOOSE messages.

Testing of IEC 61850 Digital Substation
The testing of distributed bay and substation level functions that are based on communications only – IEC 61850 8 – 1 or 9 – 2 – will be similar functionally to the testing of an individual IEDs. The main difference is that in this case there will be multiple test devices with virtual simulators or analog outputs. The simulation of the substation and system environment required for the functional testing of bay and system level functions will require the simulation of multiple merging units (IEC 61850 9-2) and other IEDs (IEC 61850 8-1).

The simulation tool will also be different, because first of all it will require a multi-node system simulator. Once the results from the simulation are available, the results from the Network System Simulator are distributed between the individual test devices that perform the simulations, as well as to make them available as sampled measured values from the virtual merging units that participate in the test.

The evaluation of the performance of the distributed functions in this case will be based on the subscription of the test system components to the GOOSE messages from the different IEDs participating in the tested distributed applications. At the final stage of the site acceptance testing when the test devices are injecting analog signals to the merging units in the substation yard and capturing the relay outputs operation that trip the breakers, all test devices need to be accurately time synchronized in order to perform the tests. A simplified block diagram of this test system is shown in the Figure

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