Interoperability Test for IEC 61850-9-2 Standard-based Merging Units

Merging units (MUs) sample alternating current (AC) in one or multiple phases and convert these analog voltage and current signals to digital values and transmit the sampled values (SVs) to protection relays (PRs) and bay controllers (BCs) through either Ethernet or optical communication channels based on the IEC 61850-9-2 protocol. MUs could provide real-time data for current, voltage, and status of power grids, and therefore, they can play a key role in real-time monitoring, protection, and control of the grids. However, MU data exchange, sharing, and interoperability can pose major challenges for the power industry. With the standardization of MU data formats, interfaces, and communication protocols, it is hopeful that data interoperability of MUs can be achieved via the IEC 61850-9-2 standard. Nevertheless, MUs and PRs produced by different vendors may not be interoperable, even though they might conform to the IEC 61850-9-2 standards. Meanwhile, another challenge is how to assure the interoperability of MUs and the best way to achieve that is through MU interoperability testing. This paper proposes a passive interoperability test method for IEC 61850-9-2 based MUs. It mainly focuses on monitoring the communications and capturing the packets between the device under test (DUT) or MU, and the MU tester or PR, and analyzing the interoperability of MUs based on the packets captured. The interoperability test system consists of five parts: a MU tester, a DUT, a network switch, a network sniffer, and a MU interoperability analyzer. IEC 61850-9-2 provides an interoperability test suite that includes a number of test cases. Two commercial MUs from different vendors have been tested with the MU Tester over Ethernet based on the interoperability test method proposed. Test results of a test case for sending SVs are provided.