Influence of instrument transformers on power system protection
Instrument transformers are a crucial component of power system protection.
They supply the protection system with scaled-down replicas of current and voltage
signals present in a power network to the levels which are safe and practical to op-
erate with. The conventional instrument transformers are based on electromagnetic
coupling between the power network on the primary side and protective devices on
the secondary. Due to such a design, instrument transformers insert distortions in the
mentioned signal replicas. Protective devices may be sensitive to these distortions.
The inuence of distortions may lead to disastrous misoperations of protective devices.
To overcome this problem, a new instrument transformer design has been devised:
optical sensing of currents and voltages. In the theory, novel instrument transform-
ers promise a distortion-free replication of the primary signals. Since the mentioned
novel design has not been widely used in practice so far, its superior performance
needs to be evaluated. This poses a question: how can the new technology (design)
be evaluated, and compared to the existing instrument transformer technology? The
importance of this question lies in its consequence: is there a necessity to upgrade
the protection system, i.e. to replace the conventional instrument transformers with
the novel ones, which would be quite expensive and time-consuming?
The posed question can be answered by comparing inuences of both the novel
and the conventional instrument transformers on the protection system. At present,
there is no systematic approach to this evaluation. Since the evaluation could lead to
an improvement of the overall protection system, this thesis proposes a comprehensive
and systematic methodology for the evaluation. The thesis also proposes a complete
solution for the evaluation, in the form of a simulation environment. Finally, the
thesis presents results of evaluation, along with their interpretation.
Advisor:Kezunovic, Mladen; Abur, Ali; Lively, William M.; Narayanan, Krishna
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:performance evaluation instrument transformer power system protection
Date of Publication:05/01/2005