When commissioning and maintaining protection and control systems supporting IEC 61850, there is an urgent need to utilize specialized tools to address a number of tasks, such as: keeping control over a stream of messages according to the implemented configuration and input signals, simulating messages with arbitrary signal attributes, and troubleshooting various communication issues (corrupted signals, configuration discrepancies, data transfer failures, etc.). Besides, it would be great to have all this functionality in one simple and easy-to-use unit. We have been provided with a device claiming to possess these features – OMICRON electronics’ DANEO 400 (Fig. 1). Let’s put hands on it and figure out if it could pretend to the name of the universal tool.
In order to test the unit out, we arrived at a 110/10 kV substation where TEKVEL company took part in the extensive reconstruction of the 6 kV switchgear with a considerable use of GOOSE (for relay protection and control, among other applications) and MMS communications.
Verification of the network traffic against SCD
We decided to test DANEO 400 in real digital substation.
TEKVEL engineers have developed Substation Configuration Description (SCD) file in advance (at the office when working on the project documentation). After arriving at the facility, we downloaded configuration into the IEDs. We first needed to check whether all of the devices produced GOOSE messages according to the SCD file, which seemed a reasonable enough desire. As DANEO 400 incorporates such a feature, we exported the SCD file from relay manufacturer’s tool and attempted to load it to that of DANEO 400.
Once the file was put into the DANEO software, we needed to select which of the IEDs present on the file would be inspected (Fig. 2). We had a total of 17 IEDs listed (two busbar sections).
The configuration software was idle for a while, and then rejected our file declaring timeout error. We had no doubt that the SCD file was valid so we decided to select just a few IEDs (all belonging to one section), and the import turned out a success. By playing around with the procedure, we found out that it was possible to pick thirteen IEDs at the most. The reason for this behavior is still to be revealed.
In order to see if the messages defined in the SCD file are present on the network, select the Verification menu in the DANEO 400 software, and then checkmark what you want to verify (either GOOSE & SV streams or MMS connection) (Fig. 3).
Fig. 4 shows what the test results will look like if all the messages defined in the SCD file can be found on the network.
Fig. 5 gives a summary of the results if an IED is expected to be sending, say, three messages (based on the provided SCD definitions), but is only sending two of them.
The DANEO 400 software allows us to figure out which of the GOOSE/SV messages causes issues. To do this, close the Verification window, and pick the troublesome device from the pull-down menu on the left-hand side of the screen (Fig. 6).
Expand the device details in order to pinpoint the message defined in the SCD file but absent on the network, as indicated by the red cross in Fig. 7.
If the IED is sending none of the predefined messages, a red cross will appear opposite the IED name in the System Verification window (Fig. 8).
One more interesting feature of the verification procedure is its capability of finding “orphans” – messages not matching any of the SCD definitions. Our network was free of such instances.
Testing GOOSE-based protection and control functions
Having verified that all of the defined messages are indeed present on our network, we were about to test them out. We needed to test protection and control functions depending on GOOSE inputs and sending out GOOSE messages. When using Wireshark, we were facing a couple of issues:
- it appeared difficult to look through the messages and highlight those of interest;
- it was hard to detect signal assertion in one or more GOOSE messages (which also applied to successive transitions).
The first problem can be coped with by coloring the messages in Wireshark, but the second peculiarity is really annoying, especially when working on your own. You have to stop keeping track of all the messages before searching for the important ones.
Oscilloscope for signals transmitted via GOOSE is great to use, especially when you are commissioning PAC system alone.
Capturing the signal transitions was equally inconvenient with IEDScout. Unlike Wireshark, the binary signals were represented as open/closed contacts, but there was no digital waveform displayed. Once away from your computer, you have no notion of what is going on with the signals when you are back at it.
To deal with this issue, DANEO offers a special function called Observation, which can be regarded as an oscilloscope for displaying selected signals. First, add signals to the pool of signals for observation (Fig. 9), and then view their records (Fig. 10).
This is so convenient! For example, assert the current-based element in the arc fault protection logic, come to a switchgear unit, open the pressure relief valve, then come back and make sure a GOOSE message was published. It would be superb if DANEO 400 could simulate messages based on the SCD file, but such a feature is absent, which makes one pay for IEDScout.
Keeping track of GOOSE/SV/PTP messages
Another attractive feature of DANEO 400 is the opportunity to verify that all of the messages get transferred without errors and data loss. To be honest, we did not believe we would have to resort to such a procedure in real facility conditions, but this eventually occurred.
Using DANEO400 monitoring feature we identified the reason for GOOSE communications failures.
While at the substation, TEKVEL engineers implemented supervision of GOOSE communications in subscribers with visual indication of alarm conditions along with audible sounds to call attention of the maintenance crew. A short while after bringing two switchgear units into service, the crew declared that the alarm had been set off. It looked weird that it was being set off in an unpredictable way, and then cleared occasionally… Moreover, different subscribers for the same GOOSE message could behave differently, say, with one of the IEDs declaring an alarm condition, and another one remaining silent. During a week of operation, each of the IEDs provided an alarm at least once. Possible suspects were either Ethernet switches, which might have been configured incorrectly, and were dropping the messages or subscribers. That looked like our chance to try out the Supervision feature targeting this kind of problems.
An option under the monitoring settings (on the Configuration tab) allows you to select the messages you would like to keep track of, as well as a DANEO 400 port used for controlling the traffic (Fig. 11).
The Actions tab is utilized for monitoring setup. The following communication details can be made visible:
- Time to live expired.
- Out of sequence (Incorrect order of messages)
- Parsing Error.
- Never seen (A message has not been captured after the monitoring started)
Whenever DANEO detects failures in the data transfer, pertinent information is recorded into the event log (the Event list tab), which stores the event timestamp as well as the message type and source, while also displaying the type of error (Fig. 13).
By connecting our DANEO 400 to various nodes at the electrical facility and utilizing its capability of uninterrupted monitoring, we found out that the subscribers themselves were to blame for not having received the messages properly. This was later confirmed in a TEKVEL lab as well as in manufacturer’s lab. DANEO 400 did help us out, and the relay manufacturer benefited too by fixing the implementation error in the end.
It is worth pointing out that DANEO 400 can also perform in-depth analysis of PTP time synchronization parameters through analysis of the protocol messages (grandmaster clock drift, grandmaster clock replacement, insertion of a UTC leap second, etc.). This functionality will provide the perfect complement to the IEC 61850 traffic supervision at existing electrical facilities.
DANEO 400, just like other equipment manufactured by OMICRON electronics, has turned out to be a good quality unit. There are still some minor flaws (showing up, for instance, when processing big SCD files) but overall this is a great tool. Nevertheless, exploiting DANEO 400 is not enough for setup and maintenance tasks at a digital substation, as a few important functions have not been implemented (such as simulation of GOOSE & SV messages based on an SCD file, reporting/controls via MMS, etc.). Some of the absent functions are available in IEDScout (GOOSE and MMS), and the other ones in CMC and SVScout (Sampled Values). In order cover all possible testing and monitoring scenarios at a digital substation, one has to put all of these tools together. It would certainly be cool to have an all-in-one unit, and we are pretty sure DANEO 400 could potentially be designed to fulfill all our expectations.