Modeling and Simulation of Impedance Distance Relay for Fault Location and Protection of Single Wire Earth Return Line


Different technologies and resources are utilized to provide electricity access for the rural population around the world. Single wire earth return (SWER) line gets prominent attention around the globe to electrify low load profile customers and remote load like telecom base stations by extending from the nearby medium grid. SWER distribution system is designed by tapping from medium voltage distribution line using an isolation transformer. Unlike other distribution systems, the secondary side of a transformer has an only single line with dedicated perfect grounding system. SWER lines are considered as a cost-effective solution, compared to the three phase grid extension by electric utility companies. Since line route is mostly in rural areas with different geographical topologies, natural and human-made faults are inevitable scenarios on the line. According to a preference of utilities and geographical locations, SWER lines are equipped with over current relay, surge arrestors or reclosers to isolate faulty line during the fault. The two main challenges on SWER line protection are to back up existing over current protection relay when it fails to clear the fault and to locate the location of fault for line maintenance. Technicians patrol up to hundreds of km along SWER line to locate a fault. This activity will be inefficient and time-consuming way of locating the fault. In this paper, we model and simulate the impedance distance relay to back up existing protection system and locate the fault. Our model successfully backs up definite time over current (DTOC) relay for a single line to ground (SLG) faults across the line. Consequently, fault locator-block locates the faulty line position.


  1. SWER
  2. Rural Electrification
  3. Impedance relay
  4. Fault location
  5. Protection



Fig.1.Impedance relay simulation model


Fig.2.Fault cleared by DTOC

Fig.3.Fault cleared by Zone-1 relay

Fig.4.Fault cleared by zone -2 relay


In this paper, the two challenges on SWER line, backup protection of DTOC relay and fault location during fault are addressed. An impedance relay is proposed to backup DTOC relay and to locate faults on SWER line.The simulation is done on MATLAB/SIMULINK on each step of 15km from relay point to the entire line. A fault is simulated at 0.4 s and during the inception of fault, the proposed impedance relay managed to clear the fault according to the intentional time delay set between each zone when DTOC fails to operate. Fault locator-block also measures the fault location by considering fault impedance during a fault. The model can measure a SWER line fault location for a fault impendence of 5Ω and below with less than 3% errors. Whereas, fault impedance compensation is required for a fault impedance greater than 10Ω to achieve better result with minimum error percentage.


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[4] L.MANDENO, “RURAL POWER SUPPLY, ESPECIALLY IN BACK COUNTRY AREAS.,” in Proceedings of the New Zealand Institution of Engineers, Vol. 33 (1947), 1947.

[5] P. Grad, “Energy Source & Distribution,” 2014, 18 May 2014. Available: [Online] [Accessed 11 March 2019].

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