Detecting and solving the coordination curve intersection problem of overcurrent relays in subtransmission systems with a new method

This paper presents a practical new method to quickly and effectively eliminate coordination curve intersection problems in subtransmission systems resulting from improper protective coordination settings in electromechanical overcurrent relays. Firstly, a database representing the relay operating characteristics was constructed based on the electromechanical overcurrent relay characteristic curves published by the manufacturer. Then, combining with this database, a fixed-point coordination curve adjustment procedure dedicated to electromechanical overcurrent relays was proposed to tackle the curve intersection situation of the coordinated upstream and downstream relay pair appearing in the original design. In addition to correcting manmade errors that could cause unexpected widespread power outages when fault occurs, the proposed technique can also enhance the effectiveness and accuracy of coordination. This study also simulated an actual case in Taiwan Power Company to verify the feasibility and practicality of the proposed method.

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Study of Solving the Coordination Curve Intersection of Inverse-Time Overcurrent Relays in Subtransmission Systems

IEEE Transactions on Power Delivery ◽

10.1109/tpwrd.2008.919391 ◽

2008 ◽

Vol 23 (4) ◽

pp. 1780-1788 ◽

Cited By ~ 20

Author(s):

Jarm-Long Chung ◽

Ying Lu ◽

Wen-Shiow Kao ◽

Chih-Ju Chou

Keyword(s):

Overcurrent Relays ◽

Curve Intersection

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Selective Sampling and Orientation of Non-Homogeneous Tissues

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100238 ◽

1968 ◽

Vol 26 ◽

pp. 98-99

Author(s):

C. C. Clawson ◽

L. W. Anderson ◽

R. A. Good

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Light Microscopy ◽

Random Sampling ◽

New Method ◽

Microscope Examination ◽

Small Areas ◽

Selective Sampling ◽

Large Numbers ◽

Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

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