Line Protection Solutions For Multiple Ibr Interconnections With Unfavorable Conditions In An Incumbent Utility Infrastructure

The introduction of inverter-based resources (IBRs) creates challenges with weak infeed on the bus it is interconnecting. Line protection for such systems rely on a strong source from a grid-connected network for dependability and advanced logic for security. Incumbent utility infrastructure often consists of a mix of technologies, designs, and configurations. Factors such as customer centricity, market competitiveness, and cost often bind the scope. There is also a queue of projects driven by external customers (such as MISO, MTEP, or 3rd-party build) impacting the same sites and driving the need for efficient solutions. Generation tie-in dates are also uncertain. Preparing relay settings for multiple IBR interconnections, even out of sequence, has become essential to avoid scope creep and repeat work, and also to coordinate relays down the line. This paper outlines the challenges with legacy, non-standard, and special scenarios, and solutions implemented on recent interconnections.

The paper presents a protection scheme for lines with IBRs on both sides of the network; short circuit modeling; coordination of under/over voltage elements (27/59); implementing distance protection (21) as the primary scheme with advanced logic, communications-aided trip (85), and enhanced POTT without differential scheme (87); applying negative-sequence supervision; and fault identification and selection logic. Effectiveness of the protection scheme is evaluated against the incumbent system with line-in, line-out string bus configurations, power line carriers, and on lines that do not have digital communications or differential schemes. Protection scheme performance for alternate configurations and N-1 contingencies are also discussed. The paper summarizes how a combination of the proposed solutions can be selected to apply on different networks, which will help in preparing for multiple IBR interconnections and increase the resiliency of protection systems. In conclusion, benefits and lessons learned of proposed schemes are presented along with some alternate future long-term solutions.