Conventional substations can consist of up to hundreds of hard-wired devices that rely on copper hard-wired connections. Modern substations, however, have improved upon this setup by adhering to the new, non-proprietary standard known as IEC 61850.
Modern substation design
Today’s substations are divided into three different levels:
Station Level – The Station Level is where you’ll find SCADA servers and HMI workstations. This is also the level where human operators monitor the status of the substation within a shielded control room, and where the Telecommunications equipment to communicate with neighbour substations and the dispatching centre are installed.
Bay Level – The Bay Level consists of devices known as Intelligent Electronic Devices (IEDs). IEDs are smart devices that receive data from sensors and power equipment, as well as issue control commands throughout the substation. They collect information from the Station Level and the measurements provided by the Process Level. The IEDs can also make local control decisions, transmit the data to other IEDs, or send the data to the substation SCADA system for further processing and monitoring.
Process Level – The Process Level is made up of devices such as circuit breakers and data acquisition equipment (CTs/VTs) that’s used to measure the current, voltage, and other parameters that are monitored in all different parts of the substation.
Substation communication networks play a critical role in the real-time, mission-critical operations of substations. While substations previously relied on analogue and one-way communication, modern substations can transmit data back and forth across a single layer and vertically between layers.
This advancement was meant to decongest the substation network by giving time-sensitive measurement data sent from the Process Level to the Merging Units (MUs) at the Bay Level and to the protection and control IEDs in the Station Bus Level. This vertical communication is connected via high speed and bandwidth guaranteed Ethernet network.
The Process Bus network handles time-sensitive data measurements between the Process Level devices and the Bay Level devices (this is what most of the substation’s protection and control functions rely on), while the Station Bus Network hosts the protection and control IEDs and handles communication between bays and outside the substation.
So now that we’ve isolated the time-sensitive data being transferred within a substation network, how can we prevent data loss while guaranteeing the delivery time of packets under any circumstance? One way is by introducing redundancy measures. IEC 61850 offers several previously standardized redundancy solutions to prevent the loss of data, including the Parallel Redundancy Protocol (PRP) and High Availability Seamless Redundancy (HSR). After all, increasing network availability will facilitate bandwidth availability for packet transfer.
But, while implementing network redundancy protocols is vital for improving and supporting network recovery time, they’re not enough to guarantee the on-time delivery of data. Even in IEC 61850 networks, single events and data transfers within a substation can greatly increase the amount of network traffic. When we take into consideration the large number of simultaneous communications within a substation, the availability of bandwidth becomes critical. The problem now is how to guarantee network availability for critical data streams in case of network congestion.
Thankfully, this is the problem that TSN solves.
Benefits of real-time communication for your substation
Time Sensitive Networking (TSN) and the new standards it brings with it offer many benefits to automation networks, including guaranteed, specific timing for mission-critical and time-sensitive applications. While some parts of TSN are still currently being developed by the IEEE, the technologies currently available to us offer up an entirely new level of determinism in data transfer. The goal is for current and future Ethernet networks to provide substations with:
Real-time networking – To date, Ethernet hasn’t been able to meet the growing demands for data delivery latency and timing. However, the ability to provide guarantees on data transfer timing is a key requirement for applications, such as the transfer of time-sensitive Sampled Values in Process Bus communications. This will allow low latency data transfer and elimination of jitter in real-time data transfer.
Future-proofing – While the standardisation process of TSN technology is expected to take a few more years, the technologies central to the TSN protocol family have been completed and have been demonstrated successfully. These mechanisms can already be integrated in products and their benefits can be used immediately. Backward compatibility is also ensured through the IEEE 802 standardisation process. This means that TSN networks that are already installed can still be used in the future.
Interoperability – TSN allows for the coexistence of real-time and non-real-time communication on the same network and it supports loss-tolerance and bandwidth reservation. These capabilities fundamentally enhance basic Ethernet technology. As TSN standards continue to roll out, the result will be a broad interoperability between vendors.
A new standard – TSN has already become one of the key enabling technologies for the IIoT and Industry 4.0. By combining TSN standards for lower layers of communication (Station Bus) and standards for higher protocol layers (Process Bus), the result is an open architecture that can be used to fully network even the most complex substation architectures.
Hirschmann’s managed switches enable real-time communication on all ports using time-sensitive networking (TSN) to provide advanced security and real-time communication on all of its ports. From applications within power and energy substations to the automated communications networks of the future, TSN is the technology that allows for the most seamless data transfer.
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