Link Redundancy on the Process Bus According to IEC 61850 Ed.2: Experience with RSTP, PRP and HSR Pr

Link Redundancy on the Process Bus According to IEC 61850 Ed.2: Experience with RSTP, PRP and HSR Protocols.

IEC 61850 is an undeniable technological advance for every Protection, Automation and Control (PAC) system. The standard presents the implementation of communication for power utility automation, via Ethernet network through two buses: the station and the process.

The network topology will define the path taken by the information. It is known that network failures can interrupt this path, causing loss of information. Thus, with the advancement of Substation Automation System (SAS) implementation based on IEC 61850, it becomes necessary to ensure maximum availability of the deployed data network.

One of the biggest fears of professionals is the loss of communication on the process bus. If this happens, the protection would become blind, without receiving the voltage and current signals from the system. Therefore, the implementation of redundancy protocols in the substation communication network is essential.

Some implementations of redundancy in the Ethernet network are already widespread. Currently, the most used protocol is the Rapid Spanning Tree Protocol (RSTP). This protocol is characterized by an algorithm (on the Switch) capable of determining the best path that a message should follow. In a network with RSTP, if one of the paths fails, all existing traffic will be transferred to the “healthy” link. However, the time spent on this maneuver will be, at best, in terms of milliseconds.

The concept of link redundancy was included in the second edition of IEC 61850, parts 8 and 9, suggesting the use of the IEC 62439-3 standard. It is noteworthy that the link redundancy is treated, in IEC 61850, as an option. In IEC 62439-3 there are two viable solutions for implementing redundancy in an IEC 61850 network, achieving both the network recovery time requirements and enabling node redundancy.

This paper presents the results of the Process Bus redundancy tests using three protocols: RSTP, PRP (Parallel Redundancy Protocol) and HSR (High-availability Seamless Redundancy). In each case, the loss of one of the redundancy links is simulated using an electronic switch, which will open the circuit. Precise electronic switching control of the link (link on/off) will allow measuring the network recovery time and analyzing the IED trip times in case of link loss for the three types of redundancy.

The effect of link loss on protection with redundancy in RSTP, PRP and HSR will be demonstrated in practice through a process bus with a Merging Unit and a protection IED supporting IEC 61850-9-2 LE. Thus, some questions that arise, like: what is the real time of recomposition found for the RSTP? What will the protection trip delay be? What is the influence of network topology on RSTP, PRP and HSR? They will be answered by testing different topologies, which will make it possible to evaluate, in practice, the impact of changing the network configuration on each protocol and, consequently, the effect on IED operating time.

A statistical analysis will be performed (tables, graphs, histograms) allowing to measure the performance of each protocol, as well as the feasibility of using each one in the IEC 61850 network.