IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays

IEEE Transactions on Power Delivery (Impact Factor: 1.73). 08/1999; 14(3):868 - 872. DOI: 10.1109/61.772326
Source: IEEE Xplore


This paper introduces the new standard “IEEE standard
inverse-time characteristic equations for overcurrent relays”. It
provides an analytic representation of typical electromechanical relays
operating characteristic curve shapes in order to facilitate
coordination when using microprocessor-type relays

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    • "In this paper, our test power system is equipped with overcurrent relays, and the inverse-time characteristics of the overcurrent relays complies with IEEE Standards [6]. The pickup time of the inverse characteristic of overcurrent relays is expressed as "
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    • "–[12], and the simulation inverse curve formula of electromagnetic overcurrent relays [13], respectively. They are employed to derive the adjustment equations for different types of overcurrent relays (1) where t time to trip, in seconds; L time dial, or lever setting; i the secondary fault current of the current transformer, in amperes; In tap value; M multiples of pickup current, where ; "
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    ABSTRACT: This paper presents a practical and effective novel approach to solve the coordination problem caused by the curve intersection of overcurrent relays in subtransmission systems. Based on the IEEE and IEC standard characteristic curve equations of digital overcurrent relays, as well as the simulation curve equation for electromagnetic overcurrent relays, lever setting adjustment equations for a selected point on the characteristic curve is derived. Then, centered on the derived equations, a dedicated software program is developed to compute the corresponding relay lever setting with different tap value in order that, passing through the selected point, another curve with the new lever setting is chosen. Finally, assisting with the graphical capability of the commercial ASPEN OneLiner, the proposed fixed-point coordination curve adjustment procedure can completely eliminate the coordination curve intersections. In addition, an actual case of a subtransmission network in Taiwan Power Company is simulated to validate the feasibility of the technique proposed.
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    • "See IEEE C37.112 -1996, IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays, [3] "
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