Open AccessApplication of let‐through energy to back‐up over‐current protection on high‐voltage feeders
Author(s) -
Slabbert Martin J.,
Bansal Ramesh C.,
Naidoo Raj
Publication year - 2018
Publication title -
iet generation, transmission and distribution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 110
eISSN - 1751-8695
pISSN - 1751-8687
DOI - 10.1049/iet-gtd.2018.6190
Subject(s) - relay , conductor , fault (geology) , electrical engineering , joule (programming language) , voltage , electrical conductor , engineering , current (fluid) , energy (signal processing) , protective relay , limit (mathematics) , control theory (sociology) , electronic engineering , computer science , power (physics) , efficient energy use , materials science , mathematics , physics , control (management) , mathematical analysis , statistics , quantum mechanics , artificial intelligence , seismology , composite material , geology
Let‐through energy (LTE) refers to the I 2 t or Joule energy that a conductor is exposed to during a fault on the feeder. This energy is influenced by the magnitude of the fault current and time it takes for the protection system to clear the fault. If the LTE exceeds the conductor thermal energy limit, the conductor will get damaged. This concept of LTE evaluation is applied to the inverse definite minimum time (IDMT) current based back‐up protection elements on a multisource high‐voltage feeder in a hypothetical and actual network. Another method to calculate the relay operating time for IDMT relays was developed based on an average disk speed of electromechanical over‐current relay and the proportionality of its speed to the magnitude of the fault current. This method was incorporated into a software application to generate results. These results allow the user to evaluate the conductor LTE exposure, total fault time exposure, the effect of instantaneous fault clearing and the application of auto‐reclose cycles. An energy‐area evaluation was applied to quantify and evaluate small protection settings changes. The conclusion is that LTE analysis on back‐up protection should be considered for high‐voltage feeders to ensure that the conductors are protected.