Westermo supplies time synchronized switches for electric power system | Automation.com

Westermo supplies time synchronized switches for electric power system

Westermo supplies time synchronized switches for electric power system
July 22, 2008 - ELKOMTECH has chosen Westermo time synchronization R208 Ethernet switches to equip recently modernised substations within the network supervised by the Polish electric operator PSE. The network manages more than 1700 high voltage substation across the country. These distribute electricity to 35 million people and to many industrial operations – so high reliability is very important. Westermo’s R208 switches deliver the highest time stamping accuracy on the market. In the PSE project, Elkomtech also equipped them with a specific redundant power supply.

PSE has long used communications solutions based on the IEC61850 standard in its new or modernized substation systems. IEC61850 is a standard for the design of substation automation, part of the International Electrotechnical Commission’s (IEC) Technical Committee 57 (TC57) reference architecture for electric power systems. It is aiming to guarantee high reliability and easy development possibilities for the future. In 2006 Elkomtech installed WindEx, which supports surveillance centres by allowing remote access to many different substation control systems.

In the last two years, Elkomtech has ordered around 100 Westermo switches through Tekniska – Westermo’s Polish agent. It recently chose the R208 for new developments.

“We sell several brands of switches, but R208 switches from Westermo provide the best accuracy on the market in terms of time synchronization – with the highest level of reliability,” says Mr Kawale, engineer at Tekniska. “For such a critical application it is ideal. We have also added a specific redundant power supply to the switches to further increase system reliability.”

Two redundant inputs are provided. The power supply draws power from the input that has the highest potential difference when compared to the alternate supply. This allows the use of a 48V source as primary supply – with a 24VDC battery as back up. Power supply inputs have reverse polarity protection.

In industrial automation, Ethernet networks have always been limited by the latency jitter of data packet transmission inside the switches. Depending on network load, data packet size and the number of switches between the server and the client, data transmission inside an Ethernet switch can cause time latency jitter of several milliseconds. A packet that enters the switch first can even go out after one that arrives later due to switch QoS (Quality of Service) techniques.

Furthermore, a network with several off-the-shelf switches will accumulate time synchronization errors for each switch on the network path between the time server and time client. The precise data analysis needed for high- or medium-voltage substation automation then becomes impossible.

Westermo’s R208 switch allows precise time-stamping, providing a full, detailed history of data events. Sophisticated or critical industrial processes – whether or not they are in real time – can now be managed with the off-the-shelf SNTP Ethernet protocol. The R208 allows industrial Ethernet networks to be installed in a redundant ring configuration, eliminating network failure caused by either fibre or copper backbone failure. It has a reconfiguration time of 30ms.

“We are working on new solutions like synchrophasor acquisition and disturbance recording, where overall time resolution below 10 microseconds is needed,” says Mr Szaniawski, Elkomtech’s R&D Director. “This made Westermo’s 1 microsecond time synchronisation resolution a very good solution for us. We receive good technical assistance from Tekniska for our other Westermo switches. We know they will provide good levels of service on the R208 range.”

Distributed control
WindEx from ELKOMTECH enables continous monitoring of high voltage equipment across the country – detecting danger points, alarms and abnormalities. The system comprises six control centres equipped with 12 real-time servers. Six servers, working together within WAN, ensure full redundancy, while the other six servers have additional functions. This creates a coherent system with distributed functions but integrated databases.

Every control centre has dedicated terminals for control staff. All terminals in the WindEx system have a main connection to the local network and backup to other nodes. In the event of WAN failure every server can work alone, supporting its substation control systems through local terminals.

All remote substation control systems have two connections to the WindEx system, through servers in two different control centres. If the main connection breaks, the system automatically switches to the backup connection.

WindEx receives information from substation control systems. In the highest voltage stations, Elkomtech used its own system, Ex-LHV – which enables full monitoring and remote access to recorders, EAZ, and other substation automation devices. Ex-LHV is a system with a distributed structure, comprising field drivers, substation computers, HMI workstations and web servers. For information interchange, the system uses the PN EN 60870-5-104 protocol.

Substation LAN puts strong demands on physical and functional reliability of any hardware used in the system. It also affects Ethernet switches, which must guarantee redundant connections, prioritization, VLANs and multicasting, fast reconfiguration, full diagnostics of LAN operation and working in critical and severe environments – in which temperature and EMC fields can vary widely. Substation LANs must allow high accessibility which could be achieved by special design and choosing hardware with very good MTBF factors.


Ethernet LAN for small/medium substations consists of a few Westermo R200 switches working in a redundant fibre optic ring. Large substations use multi-ring topology. Thanks to redundant servers and LAN with redundant ring topology, potential failure of one module does not break the whole system. Specifically for IEC61850, critical GOOSE messages can be sent reliably using the multicast and prioritization functionality within Westermo’s switches. This essential feature allows new SSiN (Control and Managing System) elements to be installed more easily.

Elkomtech uses other Westermo communication solutions such as telephone modems and adapters – allowing it to connect older parts of its system with newer applications.
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