Falling Conductor Protection

Risk Reduction Category

Protection & Detection to remove fire ignition source.

Technology Description

Downed electrical conductors pose a public safety risk due to the possibility of human contact with the conductors and the potential for arcing to ignite wildfires. Downed or fallen conductors are over-head conductors that have contacted the ground or objects connected to the ground [1].

A California utility has worked with Quanta and Schweitzer Engineering Laboratories (SEL), Inc., to develop a falling conductor protection (FCP) system. A broken overhead distribution conductor falling from a height of 30 feet (9 m) will accelerate from the moment of the break, and one or both ends reach the ground 1.37 s later [2]. The system will detect the break from circuit voltage signatures and issue trip commands so that the affected section is de-energized 200 to 500 ms after the break–when the conductors have fallen only a few feet, or about 1 meter [2].

The system uses distribution phasor measurement units (PMUs), standard protection equipment, and high-speed communication to detect the break from circuit voltage signatures and issue trip commands so that the affected section is de-energized 200 to 500 ms after the break [2].

A conceptual diagram is shown in [2], below. At the substation, there is a PMU, a real-time automation controller (RTAC) with clock and a private LTE cellular network. Multiple zones are shown in the diagram with standard protection equipment outfitted with PMUs, synchronized clocks and the communications network of private LTE cellular network.

Figure 1: Conceptual Diagram of FCP [2]

Figure 1: Conceptual Diagram of FCP [2]

The RTAC uses five voltage-based methods to detect the falling conductor condition. They are as follows:

  • Rate-of-change of per phase voltage (dV/dt)
  • Negative-sequence voltage magnitude (V2Mag)
  • Negative-sequence voltage angle (V2Ang)
  • Zero-sequence voltage magnitude (V0Mag)
  • Zero-sequence voltage angle (V0Ang)

The design permits the user to individually enable or disable each of the five methods, previously described. A voting scheme is available for added security; whereby, a certain number of methods must be asserted for the RTAC to issue GOOSE trip commands, as shown in Figure 2.

Figure 2: Voting scheme for FCP Trip Signal Issuance [2]

Figure 2: Voting scheme for FCP Trip Signal Issuance [2]

To make the FCP scheme more reliable and secure, there were several enhancements and security checks added to the pilot version of the FCP solution, which was first implemented during the 2014–2015 timeframe. These are illustrated in Figure 3.

Figure 3: Blocking conditions for FCP [2]

Figure 3: Blocking conditions for FCP [2]

This technology has been publicly discussed since 2019 and is presently an offering by SEL.

A second vendor, GE, with Southern California Edison has also deployed a similar system. HFCP (High-speed Falling Conductor Protection) detects increase in feeder impedance ratio, measured at PMU location and coordinates with downstream PMUs after conductor breaks [4].

Figure 4: GE/SCE HFCP Diagram [4]

Figure 4: GE/SCE HFCP Diagram [4]

Technical Readiness (Commercial Availability)

San Diego Gas & Electric Company (SDG&E) has implemented a falling conductor protection (FCP) solution based on synchrophasor technology and high-speed IEC 61850 Generic Object-Oriented Substation Event (GOOSE) messaging/tripping. This solution detects and trips the affected circuit section within milliseconds of the break. The affected circuit section is de-energized before the conductor touches the ground, thereby eliminating the risk of safety hazards caused by an energized downed conductor. SDG&E has implemented this solution to date on multiple 12 kV circuits with traditional communications layouts using Ethernet radios [3].

SCE and GE have also implemented a HFCP for distribution.

Vendors with Hardware and Software

Schweitzer Engineering Laboratories, Inc.: https://selinc.com/mktg/135956/

General Electric Grid Solutions: https://www.gegridsolutions.com/services/catalog/gridnode-highspeed-falling-conductor-protection.htm

Implementations / Deployments

Several 12 kV circuits at SDG&E

Southern California Edison

Innovations as of Mid 2023

Potential Enrichment Work Opportunity

References

[1] Fire Mitigation for Distribution: Achieve Quick Progress With Advanced Technology Solutions, Anthony Rahiminejad and Daqing Hou Schweitzer Engineering Laboratories, Inc., Nick Nakamura and Manoj Bundhoo G&W Electric, 2019.

[2] Transmission Line Falling Conductor Protection System Development at SDG&E, Chris Bolton, Tariq Rahman, Daniel Dietmeyer, San Diego Gas & Electric Company, Eric A. Udren, Quanta Technology, LLC, USA, PACWorld magazine, March 2023.

[3] Detecting and Isolating Falling Conductors in Midair – First Field Implementation Using Private LTE at Protection Speeds, Charlie Cerezo and Caleb Murphy San Diego Gas & Electric Company Tanushri Doshi, Rohit Sharma, and Jay Lopes Schweitzer Engineering Laboratories, Inc., 76th Annual Conference for Protective Relay Engineers College Station, Texas March 27–30, 2023.

[4] High-Speed Falling Conductor Protection in Distribution Systems using SynchrophasorData, Y. Yin, H. Kruger, H. Bayat, M. Leyba and N. Dunn GE Grid Solutions A. Marquez, A. Torres, I. Sanchez, K. Tran, M. Webster Southern California Edison Company, Conference for Protective Relay Engineers College Station, Texas March, 2022.