TRACE (Available) Transfer Capability Evaluation

TRACE is an acronym for Transfer Capability Evaluation. The package calculates the maximum MW transfer, starting from a given power system operating state, between two or more parts of the power system. This calculation is subject to pre and post contingency transmission and other operating constraints. TRACE addresses problems of transmission constrained MW transfer both in system planning and operations. The Available Transfer Capability (ATC) calculation is a subset of its functionality.

TRACE is distinguished from various simpler existing MW transfer calculations in a number of ways:

• Optional accurate nonlinear modeling of the power system, its controls, and its constraints. This avoids gross modeling approximations that may give misleading, and challengeable, results.
• Optional imposition of voltage constraints. This avoids dangerously optimistic maximum transfers based on thermal limits alone.
• Modeling of multiple control types. Controls are not limited to generator MWs. They can include phase shifts, hvdc link flows, zonal load levels, and even individual load curtailment.
• Modeling different levels of control degrees of freedom. The simpler MW transfer calculations, typically with a single degree of freedom, tend to under-utilize the available transmission capability.
• Notwithstanding TRACE's optional very accurate network modeling, it also supports a DC network modeling mode, which produces much faster non-iterative results. This can be suitable for fast on-line ATC calculations. In fact, TRACE will compute some ATC transfer limits with the DC model and others (more sensitive to voltages/VArs) with the AC model, as desired.

The cornerstone of TRACE is the security (contingency) constrained optimal power flow calculation. In the TRACE context, this calculation has two main components:

1. Identification of the limiting contingencies, possibly from a very large postulated set, and
2.Maximization of transfers subject to the constraints represented by these contingencies.

TRACE is a product whose development was sponsored by EPRI. It includes two proprietary components: ABB System Control's security analysis (item 1 above), and PCA's security constrained OPF (item 2 above). The TRACE package is commercialized by ABB and PCA, and a heavily discounted license fee is available to EPRI members. As needed, PCA may redirect any inquiries about TRACE to ABB EIS or to EPRI.

Power Computer Applications, 1921 S. Alma School Road, Suite 207, Mesa, AZ 85210. Tel: 480-345-7600; Fax: 480-345-7601.