Utility Experience with Traveling Wave Fault Locating on Lower Voltage Transmission Lines
04/03/2019, 11:00AM-12:00PM, Oak Room, University Union, California State University, Sacramento
Speakers: Robbie James, PG&E, Scott L. Hayes PE, PG&E
Traveling wave fault location systems have been in use for over half a century, and at PG&E these stand-alone systems have historically been limited to our 500kV transmission lines for which impedance based fault location has proved difficult on these series compensated lines. The Transmission System Protection department at PG&E performs hundreds of fault locations every year using traditional impedance based fault location methods. With the introduction of microprocessor line relays which have traveling wave fault location functionality built in, PG&E has installed several on our lower voltage transmission lines to gain experience with this method and evaluate including this option on all new relay installations. Lower voltage transmission lines are the most difficult to use impedance based fault locating due to taps, infeeds and non-homogenous conductor.
The new relays can automatically calculate traveling wave fault locations, but only on clean two terminal lines where the relays on both ends of the line are connected together via a digital communication circuit. Manual traveling wave fault locating requires a new skill set for the Protection Engineer who at the most basic level needs to understand how traveling waves reflect and transmit through changes in the characteristic impedance along the line. These changes in characteristic impedance occur at the substation and the point of the fault, but also occur at tap points along the line. For the double ended traveling wave fault locating method, only accurate determination of the arrival time of the incipient waveform is needed for accurate fault locating, but for the single ended method it is critical to understand these line reflections as manifested in the Bewley lattice diagram. We will present cases where traveling wave event files on a line with multiple taps could not identify a location and cases where it was successful, and detail the conditions for both results. Discussion will include the differences between single ended and double ended fault locations with and without GPS clocks. A comparison between accuracy of our impedance based fault locations and the traveling wave fault locations will be discussed.
Robert James received his BS in Electrical Engineering and Computer Science from University of California, Berkeley in 2005, and graduated with distinction with an MS in Electrical Engineering from California State University, Fresno in 2009. He started his career with Pacific Gas and Electric Company in 2008 as an intern in Distribution Engineering and has held his current position as a Transmission System Protection Engineer since 2010. Robert has been a lead at PG&E for travelling wave fault location on the transmission system. He is a registered Professional Engineer in the state of California.
Scott Hayes received his BSEEE from California State University, Sacramento in 1985. He started his career with Pacific Gas and Electric Company in 1984 as an intern. Since then he has held multiple positions in System Protection including supervisor, as well as Distribution Engineer, Operations Engineer, Supervising Electrical Technician, Supervising Engineer in Power Generation and is currently a Principal Protection Engineer focusing on standards, procedures and quality. Scott has previously co-authored papers for the Western Protective Relay Conference, Georgia Tech, TechCon Asia Pacific, CEATI Protection and Control Conference and Transmission and Distribution World Magazine. Topics include Thermal Overload Relays for Intertie Lines, Data Mining Relay Event Files to Improve Protection Quality, Effects of CCVT Ferroresonance on protective relays and PG&E’s Wires Down Program. Scott is a registered Professional Engineer in the state of California and has served as Chairman of the Sacramento Section of the IEEE Power Engineering Society. He is currently the chairman of the CEATI Protection and Control Program and is a member of the NATF protection core team. He has also served on a NERC Standard Drafting Team.