Transmission line setting calculations - beyond the cookbook

Abstract

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

A Single-End Protection Scheme for Hybrid MMC HVDC Grids Considering the Impacts of the Active Fault Current-Limiting Control

“…To avoid noise disturbance under external faults, the threshold with higher reliability coefficient k rel1 is selected to design the criterion of the Stage I protection, which can be expressed as: (26) where Δ I is the threshold for the Stage I protection.…”

“…Taking the relay CB12 as an example, the threshold setting calculation will be conducted as follows. Regarding the selection of reliability coefficients, for increment protection algorithms, such as ground instantaneous overcurrent protection, the reliability coefficient is ranging from 1.25 to 1.5 [26]. For decrement protection algorithms, such as the protection zone I of distance protection, the reliability coefficient is ranging from 0.8 to 0.9 [26].…”

“…Regarding the selection of reliability coefficients, for increment protection algorithms, such as ground instantaneous overcurrent protection, the reliability coefficient is ranging from 1.25 to 1.5 [26]. For decrement protection algorithms, such as the protection zone I of distance protection, the reliability coefficient is ranging from 0.8 to 0.9 [26]. To improve the reliability to avoid mal-operation, the reliability coefficients are selected to be 1.5 for increment protection criterion while 0.8 for decrement protection criterion.…”

The Impact of STATCOM on Power Systems Protection Devices

“…Step Zone 3 is used for backup protection in the event of a failure at the remote bus. Reaches of 200 percent or more of line impedance are common with Zone 3 [8]. To study the impact of STATCOM on performance of distance relay, we used 48-puls STATCOM was designed by MATLAB/SIMULINK environment and it has many applications like regulate voltage by setting the desired reference voltage, fix the reactive power, and fix the reactive current.…”

Analisis Resetting Rele Jarak Akibat Uprating Konduktor Gis Pesanggaran - Gi Sanur

“…Maximum torque angle adalah sudut ketika reach setting mencapai maksimum, dalam artian sudut dari diameter lingkaran mho. Besaran sudut MTA disetting sesuai dengan impedansi urutan positif / negatif penghantar yang diproteksi [8].…”