Reliable & safe Grid connectivity of SC test Laboratory, innovatively using substation bus-bar design

There are numerous designated Inter/Intra state consumers, generators and distribution licensees connected to the grid network requiring reliability of the normal grid operations even during the period of test conductions. Though the grid elements are generally constructed as per global Standards/best practices, still occurrences of the short-circuit in the grid network during grid operations cannot be ever eliminated, particularly for the power lines which crisscross the varying terrain and environmental conditions. At NHPTL, during initial SC test conduction no abnormal voltage drop were observed at the generating station in the vicinity of

Bina. Nevertheless, concerns were raised by the generating station nearby, regarding any possible risk of generator unit tripping/outage during the planned SC testing at NHPTL. The objective of this paper is to present an innovative and viable operational solution that could be adopted to mitigate voltage drop risks during SC testing, without compromising grid security or requiring other expensive mitigating methods for such short duration of the SC test conduction.

The said operational solution leverages the existing 1½ bus-bar configuration at two associated 400 kV substations connected to the generating station near Bina. An arrangement of ‘Bypassing’ was devised by opening two main circuit breakers at each of the two substations prior to SC test conduction. Thus an effective extension of the electrical distance of the generating station feeders from the NHPTL node could be enabled. Required power system simulations were carried out to evaluate the impact of this network reconfiguration on voltage profile, system stability, and grid parameters.

The study results demonstrated that the implementation of the ‘By-passing’ arrangement reduced the voltage drop at the generating station from approximately 18% to 2.5% during SC test conduction. Additionally, no adverse impact was observed on other remotely connected generating stations or grid elements. The findings were validated through power system simulations and corroborated by several years of operational experience thereafter.

The paper concludes that the proposed ‘By-passing’ arrangement is an effective, economical, and reliable risk mitigation strategy for managing voltage stability issues with such gridconnected short-circuit testing laboratory. The approach offers valuable insights for similar high-power testing facilities and grid-interfaced projects that require temporary gridconnectivity solutions without compromising grid reliability and stability.