Grid Operations

Nexant software applications play a critical role in ensuring safe and reliable grid operations. With the changing flow patterns resulting from today's deregulated markets and distributed generation and demand response environments, it is now more essential than ever to accurately analyze and predict transmission grid security levels.

Real-time security and market operations are based on a state-estimated model of the transmission grid. Nexant's state estimator GEN-SE® is the most advanced in the field. It employs generalized equipment representation and sophisticated algorithms to produce the most accurate and reliable snapshot model of the network. This estimator has unique strengths in terms of convergence reliability, computation speed, realistic modeling, bad measurement detection and identification, and the resolution of parameter and topology errors. It is used in many national, regional, and large metropolitan control centers. A companion, highly innovative, topology estimator application TOPAZ®, developed in partnership with EPRI, applies the most powerful possible techniques for the real-time identification of network topology errors (typically due to misread breaker statuses).

The estimated model of the power system network state is the basis for all subsequent real-time or near-real-time grid calculations. Some of the most important such functions are performed by Nexant's versatile SCOPE® package. One of these functions is rapid contingency analysis under (N-1) or more stringent security criteria. SCOPE's main claim to fame (having been implemented in over a hundred EMS's worldwide) is its ability to solve a wide variety of security constrained optimal power flow problems, whether online or in study mode. In this area, SCOPE performs security-constrained economic dispatch, remedial action calculations, loss minimization, and bid based reactive economic dispatch. A unique and very important strength of SCOPE is that it accommodates different levels of network modeling detail, so that tradeoffs between computing speed, solution accuracy and data availability can be made, depending on the specific application. At the high end, very detailed system modeling is available, including conditional post-contingency switching, and contingency-specific constraints.

Another industry-leading Nexant application is its FLASH® short circuit analysis, designed for operation in real time. This application incorporates both advanced modeling at circuit breaker level and extremely high speed. The symmetric and asymmetric make/break duties of individual circuit breakers are evaluated, together with open-branch analysis. FLASH is used in some of the world's highest-density cities and (in one case) for an entire nation.

As grids become more interconnected and cascading outages increase in probability, control center operators must be at pains to model the important elements of their external network world. Nexant's totally unique MODELEX® software determines what parts of the external system should remain explicitly modeled (and also indicates what real-time external data is needed) in order to accurately reflect the responses and loop flows of the "external" network. In addition, it computes the corresponding reliably-accurate external network equivalents.