System Protection Schemes Research Articles

IMPROVED PERFORMANCE DIRECTIONAL RELAY

ABSTRACT This paper presents, in a constitutive and functional approach, an original, improved performance directional relay which as proved to yield better results as compared to similar devices employed in relay protection circuits The directional relay described here has been designed to insure selectivity in maximal protection circuits for two-end supply networks and in transversal differential double-line protections, as well as to act as a component of long distance safeguarding of interconnected networks and as a protection device to prevent the engine operational status of synchron generators The scheme of the relay is based entirely upon static commutation. The working principle is based on controlling the phase differences between the current and the voltage in the circuit to be safeguarded through an electronic phase detector consisting of integrated circuits. The relay contains new elements as compared to traditionally adopted solutions and brings about certain technical and economical advantages, whereas its performances indicate it highly suitable for relay protection schemes in power systems.

A Probabilistic Approach to the Design of Power System Protection Schemes Against Blackouts

A probabilistic approach to study the dynamic behavior of power systems in extremely disturbed modes is presented. It takes into account all causes liable to lead to such conditions (weakened operating conditions, abnormal operations of protection schemes, multiple disturbances) and modeling uncertainties. Combinations of these factors are screened by Monte-Carlo simulations using a full-scale time-domain integration program and storing relevant parameters of the resulting system trajectories in a data base. The latter is analyzed using data mining tools, such as clustering and decision trees in order to identify system weaknesses and possible improvements. The approach is tested on the South-Eastern part of the EHV system of Electricité de France, using a simulation model with in excess of 11,000 state variables, yielding a data base composed of 1500 simulation scenarios. Their diversity is illustrated by discussing different observed scenarios: voltage collapse, overloaded line tripping in cascade, loss of synchronism. Some preliminary data mining results are provided.

Transmission system protection: a reliability study

ComEd developed a methodology for evaluating the reliability of transmission system protection schemes in 1995. Two approaches were developed: one focused on component reliability data; and the other on component operating history. The second approach has been put into practice. A review of transmission system disturbances identified protection schemes and lines that are less reliable than others, thus permitting a focused program of maintenance and replacements. The reliability method is described, along with sample data and results.

A high speed power system transmission line protection scheme using a 32-bit microprocessor

The availability of cheap and powerful microprocessors in recent years has led to their increasing use in all aspects of power engineering. In future years they are expected to play an even greater role in power system protection schemes because of their ability to: (1) compare on-line data and come to a logical or quick decision; (2) store information from past events and make an expert decision; (3) combine various complicated tasks, etc. Thus, the application of microprocessors in power system protection is much more attractive than in many other fields. As an example, this paper develops a high speed digital protection scheme for a power transmission line. A signal processing technique is used to analyze the power spectrum of the transient fault currents, which makes it possible to develop a desired digital filtering algorithm using computer-aided design (CAD) techniques and minimize the potential for false tripping due to the steady-state system harmonics. This design was implemented on a 32-bit MVME133 monoboard microcomputer to demonstrate the protection of a model power transmission line.