Coordinating dissimilar line relays in a communications-assisted scheme

Tucker, William M.; Burich, Andrew; Thompson, Michael J.; Anne, RadhaKiranMaye; Vasudevan, Sneha

doi:10.1109/cpre.2014.6798998

Cited by 6 publications

(2 citation statements)

References 5 publications

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“…Although the NERC Misoperations Report mentions accommodating different operating speeds between different relay technologies in a communications-assisted scheme, it is important to realize that it is not possible to completely ensure the sensitivity coordination of dissimilar relays. That is, a pilot tripping element and its associated remote pilot blocking element in dissimilar relays will not respond in the same way to an extreme boundary fault [2].…”

Section: Reducing Misoperationsmentioning

confidence: 99%

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Transmission line setting calculations - beyond the cookbook

Thompson¹,

Heidfeld²

2015

2015 68th Annual Conference for Protective Relay Engineers

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Setting transmission line relays is fairly easy to learn-but takes years to master. With the proper education, tools, and references such as company standards available, a relatively inexperienced engineer can do good work with proper supervision and review. There are many references and training programs that provide the high-level basis for protective element setting criteria. But, the concepts have to be applied with care in context of the particular transmission line and system in question. The transmission network is complex, with many variations that must be identified to determine when deviations from cookbook guidelines are required. This paper looks at various commonly used transmission line protective elements and points out characteristics of the line and system to look for when standard reaches and margins cannot be used. While the subject is vast, the authors draw on their experience to point out some of the more common issues.Sensitivity is a measure of the ability of the relay to pick up for in-zone faults. It affects how the relay performs under minimum source conditions, for high-resistance faults, and for low-grade faults. Sensitivity is related to selectivity as well. Distance and overcurrent elements that are set more sensitive are less selective and vice versa. Selectivity, speed, and sensitivity need to be balanced to produce a relaying scheme that is reliable. B. Defining ReliabilityThe reliability of a relaying scheme is more precisely defined using the terms dependability and security. Dependability is the ability of a scheme to operate for any inzone fault. Security is the ability of a scheme to not operate when there is no in-zone fault. They are usually inversely related, but better schemes can raise both to improve overall reliability. Security is challenged every time faults occur in adjacent zones of protection, but dependability is only challenged when the fault is in-zone.According to the North American Electric Reliability Corporation (NERC) Misoperations Report, approximately 94 percent of misoperations resulted in false trips [1]. False trips indicate a bias toward dependability, whereas failures to trip indicate a bias toward security. Traditionally, transmission line relaying schemes are designed with a dependability bias 850 978-1-4799-8722-1/15/$31.00

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Section: Reducing Misoperationsmentioning

confidence: 99%

“…Blocking element coordination is just as important for modern POTT schemes as it is for DCB schemes [2]. The coordination process should be conducted in primary ohms in case the CTRs are different.…”

Section: E Phase Distance Pilot Blocking Zonementioning

confidence: 99%