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This paper presents a methodology on the design of an optimal predictive control scheme applied to an islanded microgrid. The controller manages the batteries energy and performs a centralized load shedding strategy to balance the load and generation within the microgrid, and to keep the stability of the voltage magnitude. A nonlinear model predictive control (NMPC) algorithm is used for processing...
This paper describes several commonly applied line protection schemes, including distance schemes, directional comparison schemes using distance and directional elements, and line current differential schemes. Using analysis tools like fault trees, power system studies, and event analysis, we evaluate and compare these protection schemes in terms of speed, sensitivity, dependability, security, and...
The Penonomé wind power plant in Panama will have a total capacity of 337.5 MW. The first two phases currently in service provide 270 MW of generation. In this power plant, wind generators belonging to different companies are connected to a 34.5 kV system. Two transformers interconnect the 34.5 kV system to Panama's 230 kV transmission system at the El Coco substation. The 34.5 kV system is grounded...
This paper explains the principles of negative-sequence differential (87Q) protection, its basis for excellent sensitivity and speed, and the need for securing it with external fault detectors to deal with the saturation of current transformers. The paper reviews applications of 87Q elements to lines and transformers. It explains why 87Q elements cannot be used for turn-to-turn fault protection in...
This paper is a tutorial on the protection of mutually coupled transmission lines. It discusses how mutual coupling affects the polarizing quantities of ground directional elements, the reach of ground distance elements, and the accuracy of single-ended fault locating algorithms. The paper provides settings guidelines for instantaneous directional overcurrent and ground distance elements. It discusses...
This paper discusses the factors to consider for sizing current transformers (CTs) for line protection applications. We first cover CT basics, with emphasis on errors and ac and dc saturation. We also discuss the criteria to avoid CT saturation. Then we analyze the effect of CT saturation on overcurrent, distance, directional, and differential elements. Further, we present the advances in protection...
During the past few years, a worldwide acceptance of IEC 61850 has been demonstrated as more and more substation devices are being integrated based on Ethernet technology. This trend represents new challenges for integrators, manufacturers, and end users. However, the field-proven benefits and lessons learned are truly valuable to managers, supervisors, and executives curious about bringing the benefits...
In this paper, we apply fault tree analysis to compare the dependability and security of line protection schemes with different degrees of redundancy. We also compare the scheme costs. For each scheme, we use a basic protection scheme as the reference. We then evaluate schemes with double redundancy and two-out-of-three voting schemes. We also evaluate the effect of comprehensive commissioning testing,...
Overhead distribution systems may experience faults involving more than one feeder. During simultaneous faults, the transformer low-voltage-side overcurrent relay measures a current greater than the current measured by faulted feeder relays. Therefore, the transformer relay may trip faster than faulted feeder relays. Transformer relay misoperation affects service availability in circuits not involved...
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