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.

An evaluation of energy storage techniques for improving ride-through capability for sensitive customers on underground networks

Abstract: Most customers of Consolidated Edison Company of New York, Inc. (Con Edison) are supplied through extensive secondary distribution network systems. These customers do not experience interruptions or outages, except under very rare circumstances. This is a significant advantage for these customers, since they do not normally need to apply conventional uninterruptible power systems (UPSs) for protection of critical loads against outages. However, voltage sags, which occur whenever there is a fault on the power system, can cause dropout or misoperation of sensitive equipment. Some type of protection may be needed for these loads to provide ride-through support during voltage sags. This paper describes the methodology used in a research project sponsored by the Electric Power Research Institute (EPRI) and Con Edison to evaluate the need for voltage sag ride-through improvement for selected customers. Technologies that can supply the required ride-through and application considerations are evaluated. Two case studies are presented to illustrate the methodology used to perform the evaluations.

Reliability Modeling of Protective Systems

Abstract: Electric power systems are comprised of a very large number of interconnected components that are designed for the sole purpose of generating and delivering electrical energy to consumers. Usually, the consumers are free to accept or-reject the available electrical energy at will, suggesting a probabilistic rather than deterministic demand pattern. The system is operated by humans and by automatic control apparatus, both having some probability of failure to perform their function. Moreover, the system physical components are subject to failure in some random way, with each failure often requiring corrective action. Since the system is geographically extensive, it is subject to a large number of natural and man-made hazards. Examples are lightning induced faults and physically damaged components that result from natural or man-made causes. For the purpose of this discussion we classify all of the above as disturbances. Some of these disturbances, such as short circuits, cause severe upsets in system operation and must be somehow removed or isolated. This is the role of the 'protective systems,' which are installed throughout the power system, to detect and remove hazardous disturbances, which we usually call faults.

Comparing Power Transformer Turn-to-Turn Faults Protection Methods: Negative Sequence Component Versus Space-Vector Algorithms

Abstract: This paper presents a comparison of two of the most sensitive methods to detect low-level turn-to-turn faults in the windings of three-phase transformers. The performance of the negative sequence component and of the space-vector protection algorithms is tested under several internal and/or external fault conditions. The results indicate that the space-vector approach is slightly more sensitive for detecting low-level turn-to-turn winding faults. For more severe defects, the fault detection sensitivity of both methods is similar.

Detection of Incipient Faults in Underground Medium Voltage Cables

Abstract: This paper presents an operational experience with incipient faults: it has been observed that 10 to 15% of cable faults are preceded by incipient faults. Practically all incipient faults become permanent faults in the period between a few seconds to few weeks. Incipient faults occurring in fast successions create considerable over-voltages and induce faults on other feeders. A method has been presented to detect incipient faults in a secure and reliable way. The method is secure by checking consistency of the load before and after the event, checking if the event is a single phase event, and checking for duration and consistency between the superimposed fault component and the ground current. The presented method has been implemented and tested using recorded field cases and on a digital simulator. Simplified variants of the method can be implemented by using programmability and flexibility of modern microprocessor based relays. Recommendations are given as to the trip vs alarm applications of the incipient cable fault detection functions. In many cases tripping on the first incipient fault is a prudent application.

Description of a Micro-SMES system for protection of critical customer facilities

Abstract: The system configuration, theory of operation, computer simulations, and important application experiences of a (750 kVA) superconducting magnetic device (Micro-SMES) for application on power distribution circuits to enhance customer power quality are presented. The functions of the major components of the Micro-SMES are separately discussed and the operation of each component is illustrated with an Electro-Magnetic Transients Program (EMTP) simulation example. Application performance characteristics obtained from the first practical installation of a Micro-SMES are summarized and its protection effectiveness is evaluated. >