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MODELING RELAYS FOR POWER SYSTEM
PROTECTION STUDIES

by
SANDRO GIANNY AQUILES PEREZ

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ABSTRACT
Numerical relays are the result of the application of microprocessor technology in relay
industry. Numerical relays have the ability to communicate with its peers, are
economical and are easy to operate, adjust and repair. Modeling of digital and
numerical relays is important to adjust and settle protection equipment in electrical
facilities and to train protection personnel. Designing of numerical relays is employed
to produce new prototypes and protection algorithms. Computer models of numerical
relays for the study of protection systems are greatly enhanced when working along with
an electromagnetic transient program (emtp). A literature survey has revealed that
previous modeling techniques presented a lack of automation in the generation of relay
models, or show high complexity in linking the numerical relay models with the power
system modeled in the emtp.
This thesis describes a new approach of modeling and designing of numerical relays.
The proposed methodology employs a Visual C++-based program (PLSA) to obtain
from the user the specifications of the relay to be designed, and to process this
information to generate the FORTRAN code that represents the functional blocks of the
relay. This generated code is incorporated in a PSCAD/EMTDC case using a resource
called component, which facilitates the creation of user-custom models in
PSCAD/EMTDC. Convenient electrical and logical signals are connected to the inputs
and outputs of the PSCAD/EMTDC component. Further additions of digital relay
models into the PSCAD/EMTDC case constitute the protection system model. The
thesis describes a procedure for designing distance and differential relay models, but the
methodology may be extended to design models of other relay elements.