Power-system protection

About: Power-system protection is a research topic. Over the lifetime, 6353 publications have been published within this topic receiving 117961 citations.

High-resistance faults on a multi-terminal line: analysis, simulated studies and an adaptive distance relaying scheme

Abstract: The presence of a T-connection to a third terminal can drastically affect the performance of a distance relay at the other terminals. Fault resistance, especially high fault resistance, makes this problem more severe and complicated. Detailed analysis of the apparent impedance for these cases as seen from the relaying point is derived and, based on extensive simulations of the infeed/outfeed and fault-resistance effects on the relay characteristics, an adaptive distance relaying scheme is proposed. A microprocessor based distance relay using this new technique can quickly respond to very-high-resistance faults with maximum coverage of the protected line. The validity of this new scheme has been confirmed by real-time testing on a prototype hardware scheme. >

Tests of distance relay performance on stable and unstable power swings reported using simulated data of the August 14 th 2003 system disturbance

Abstract: The electric power system maintains a dynamic and delicate balance between generation and load in normal operatio condition. A disturbance, such as a sudden change of load, a power system fault, or a trip of a large generation unit, may break the balance, cause the oscillations among the generator rotor angles and force the generators to adjust to a new operating condition. The adjustment will not happen instantaneously due to the inertia of the generator prime movers. The oscillation will cause either stable and/or unstable power swings. During a power swing, the impedance trajectory seen by a distance relay may enter the fault detection zones and cause unwanted relay operation. During the Blackout on August 14th, 2003 in North America, stable and unstable power swings occurred and caused the operation of several distance relays. In 2007, Northeast Power Coordinating Council (NPCC) formed a joint team to start an investigation on the issue with the goal to improve the performance of distance protection in such events. This paper reports on distance relay testing that was performed by using simulated data of the blackout from NPCC's SS-38 working group. The simulations include both stable swings and unstable swings. The goal of these tests was to evaluate solutions which could be implemented to avoid unwanted distance relay operations for such events. The paper discusses the feasibilities and limitations of using load blinders to prevent relay operations during stable power swings. Several power swing blocking methods are discussed, and their advantages and disadvantages are compared. This paper describes the test procedures, and presents and discusses the test results. Relays were programmed for both mho and quadrilateral characteristics for the tests. Some recommendations and comments are made on the protection for the conditions of stable and unstable power swings.

Modeling of a transmission line protection relaying scheme using Petri nets

Abstract: This paper proposes a transmission line protection relaying scheme model using Petri nets (PNs), including three types of relays as well as an automatic reclosing device. By analyzing the properties of the PN model, the dynamic behaviors of the modeled system are evaluated and the drawback of the system is detected. This model may also be extended to other similar systems to evaluate their performances.

A signal processing module for power system applications

Abstract: This paper presents a unified power signal processor (PSP) for use in various applications in power systems. The introduced PSP is capable of providing a large number of signals and pieces of information which are frequently required for control, protection, status evaluation, and power quality monitoring of power systems. The PSP receives a set of locally measured three-phase voltage and current signals and provides their fundamental components, amplitudes, phase angles, frequency, harmonics, instantaneous and stationary symmetrical components, active and reactive currents and powers, power factor, and the total harmonic distortion. Simplicity and integrity of its structure as well as its robustness with respect to internal parameters and external disturbances and noise render the proposed scheme very attractive for practical implementations.

A new method for protection zone selection in microprocessor-based bus relays

Abstract: Use of graph theory simplifies representation of complex bus arrangements in power system stations. This paper presents a new method, based upon graph theory, for selecting bus protection zones in microprocessor-based relays. We use a typical bus arrangement to illustrate the graphical representation of station arrangements, graph operations, and associated matrix operations. We also describe an implementation of the zone selection method and use two examples to demonstrate the advantages of the method. Using the status of switching devices in the station, the zone selection method provides the relay with real-time bus arrangement information. The bus relay uses this information to assign input currents to a differential protection zone and to select which breakers to trip for a bus fault or breaker failure.