Hybrid signal analysis in protection and automation systems

Modern protection and automation systems for electrical power systems are increasingly using communication protocols to transfer information. In the mid-term, more and more hybrid systems and systems distributed across large distances will be implemented.
 In this context, hybrid means that protection and automation systems will operate simultaneously with classical secondary quantities and conventionally wired binary status signals, as well as with communication protocols such as those according to IEC 61850. Measuring and evaluating all of these different signals within such hybrid systems requires measurement systems that are also distributed and operate in a hybrid way. The following article provides an overview of the current status of developments, describes the challenges currently being faced, and presents potential solutions.
Hybrid systemsBesides classical secondary quantities and conventionally wired binary status signals, more and more of the mission critical information of the automation systems is transported across communication networks. In systems utilising IEC 61850 communication, the transmission of binary status information via GOOSE messages is an established practice. The next step will be to replace the secondary quantities with Sample Values, which will then transmit digitally coded current and voltage values across the communication network. But even if data transfer within automation systems will be primarily performed via communication protocols in the future, classical actuators and quantities within the process will still need to be acquired by conventional means.
Distributed systemsOnce it is digitised and wrapped in data packets, the transmission of information across large distances is essentially simplified. Whereas the installation of wire loops between individual binary outputs and inputs quickly becomes too costly or susceptible to interference, transmission via noise immune network connections is comparatively easy and allows large volumes of information to be transmitted. This enables the use of applications which previously could not be implemented effectively without digital communication technology. These include bridging distances within a substation across local networks, as well as between substations across wide area networks. Depending on the bandwidth and signal propagation delay (latency) of the network connections, additional new deployments have become possible. While formerly it was only possible to transfer a few bits using modulators and pilot wires, and even then often with significant delays, channels with bandwidths of multiple Mbit/s and low latency are frequently available now. Concepts such as remote interlocking or remote tripping of circuit breakers are increasingly being applied today.
Distributed hybrid measuring systemSupervising and evaluating the function of distributed systems requires a measuring solution which is capable of registering data and signals at all the relevant measurement locations of the distributed system. The system itself must also be hybrid in order to record both the classical signals and the network communication at the same time. The new DANEO 400 signal analyser from OMICRON offers these options. Its central software manages all the acquisition devices deployed at various measuring locations as a single measurement system. A precondition for such a system is that all recording devices can be accessed via a network connection. It is then no longer necessary to manually transfer individual files from the acquisition devices and compile all of the data. The measured data is actually compiled for the user in a transparent process and refers to the observed event – the subsequent analysis is then based directly on the related data. It is also possible to export the measured data in generic formats (COMTRADE, PCAP) in order to perform special analyses with external tools.

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