Lessons learned from commissioning of IEC 61850-9-2 process bus-based busbar protection system

Distributed busbar protection systems are common these days compared to traditional centralized busbar protection systems. Often, a digital distributed busbar protection system is implemented using the proprietary technology of the numerical relay original equipment manufacturer (OEM). IEC 61850-9-2 standard for process bus communication and IEC 61850-9-2 LE guidelines offer a provision for a standardized and interoperable IEC 61850-based distributed busbar protection system and digital secondary system (DSS). This paper introduces necessary and sufficient test processes and performance metrics required for a DSS installation and the specific commissioning results for a DSS serving a large-distributed busbar protection application.

DSSs simplify the physical installation of the substation secondary system by significantly reducing the amount of copper cabling required for wiring digital and analog signals to substation Protection & Control IEDs. IEC 61850-9-2 LE-compliant intelligent electronic devices (IEDs) provide the possibility for interoperability between different OEM IEDs at the process bus level, giving customers the flexibility to include products from more than one vendor during the initial installation and future expansion of the process bus. This flexibility may be an advantage in contrast to DSS solutions implemented using proprietary process bus technologies. IEC 61850-9-2 process bus protocols (sampled values [SVs] and generic object-oriented substation event [GOOSE]) are Ethernet-based solutions installed as direct fiber-optic cables between devices or as a local-area network (LAN) using an Ethernet switch to communicate between process bus IEDs. Because process bus SV IEDs require time-synchronization accuracy with errors less than one microsecond to function, IEEE 1588 Precision Time Protocol (PTP) power profile is used to provide high-accuracy time synchronization to IEDs through an Ethernet network via the process bus or station bus; alternatively, a separate IRIG time distribution bus can be used. To ensure reliable operation of the IEC 61850-9-2 process bus system, a highly secure and resilient communications network is necessary.

This paper discusses an IEC 61850-9-2 process bus, PTP power profile, and software-defined networking (SDN)-based busbar protection system, which was implemented at a 400 kV substation for the Power Grid Company of Bangladesh (PGCB). The implemented solution protects four diameters of a one-and-a-half breaker scheme, and it has a provision for future expansion to accommodate up to eight diameters. It discusses SV-based and GOOSE-based busbar protection philosophy, network latency, time synchronization, cybersecurity requirements, the ability of the software-defined process bus to meet and exceed requirements, field testing results, and lessons learned from the project. It also discusses the many metrics used to test and verify the behavior of an installed process bus system and provides data and evidence of the health and performance of the process-bus-based DSS protection system.