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SCADA and PRP – A good match?
Is a PRP and HSR in Ethernet networks of transformers actually of any use – or does RSTP meet the requirements anyway?
The SCADA component plays an integral part in transformer stations. This was previously the case – and it is now still applicable to IEC 61850-based systems. This is because we monitor and operate the primary equipment systems with SCADA components. Only this way is reasonable local operation of a transformer station possible.
High availability: a must
Local SCADA systems are often designed for high availability, especially at high voltage levels. This is achieved by redundant systems and redundant Ethernet communication interfaces.
The international IEC 62439-3 standard describes two redundancy protocols for Ethernet Layer 2 (in accordance with OSI – Open System Interconnection Model):
- “Parallel Redundancy Protocol” (PRP) and
- “High-availability Seamless Redundancy” (HSR).
These protocols offer “seamless” redundancy with a switching time of 0 milliseconds – a must for critical high-speed applications. But, is this effort really always necessary?
Sure, Ethernet failover times, latency times and speed requirements are important parameters for the different SCADA and automation functions. However, isn’t a cost-effective combination of link aggregation and Rapid Spanning Tree Protocol (RSTP) sufficient? Most of all for the performance requirements of simple IEC 61850 client/server communication?
White Paper provides detailed information
However, critical high-speed functions integrated into a SCADA system, such as load shedding using IEC 61850 GOOSE, need the best failover performance. This can only be achieved with PRP and HSR redundancy protocols. Furthermore, the road has already been paved to increased integration of control and protection functions in the central SCADA servers. We will therefore see more and more SCADA systems that are equipped with PRP or HSR in the future.
What matters, and which architecture is the best for your equipment, is described in our new white paper “Ethernet Network Redundancy in SCADA and realtime Automation Platforms”.