A method for the computation of fault location in two- and three-terminal high voltage lines is presented. It is based on digital computation of the three-phase current and voltage 60/50 Hz phasors at the line terminals. The method is independent of fault type and insensitive to source impedance variation or fault resistance. Furthermore, it considers the synchronization errors in sampling the current and voltage waveforms at the different line terminals. The method can be used online following the operation of digital relays or offline using data transferred to a central processor from digital transient recording apparatus. The authors start with a two-terminal line to explain the principles and then present the technique for a three-terminal line. The technique was first tested using data obtained from a steady-state fault analysis program to evaluate the convergence, observability, and uniqueness of the solution. The technique was then tested using EMPT-generated transient data. The test results show the high accuracy of the technique. >

A new fault location technique for two- and three-terminal lines

Fault location is an important application among intelligent monitoring and outage management tasks used for realization of self healing networks, one of the most attractive features of smart grids. The data gathered from various intelligent electronic devices (IEDs) installed throughout the power system could be utilized for smart approaches to locating faults in both transmission and distribution systems. This paper discusses issues associated with improving accuracy of fault location methods in smart grids using an abundance of IED data. Two examples of how the gathered data from different IEDs is used to improve fault location accuracy in transmission and distribution systems are discussed in detail.

Smart Fault Location for Smart Grids

This work presents a digital fault location technique for rural distribution feeders, using the voltage and current data at a single location. Rural distribution feeders include single-phase, two-phase, and three-phase laterals off a main three-phase primary distribution feeder. The fault location scheme presented here attempts to account for the multiphase laterals, the unbalanced conditions, and the unsymmetrical nature of distribution feeders by continually updating voltage and current vectors at set locations within the system. The updated voltage and current vectors are the estimates of the 60-Hz phasor quantities obtained using a recursive optimal estimation algorithm. The distance to the fault is then estimated using a method based on the apparent impedance approach and the updated voltage and current vectors. Another consideration is the ability to determine the fault location on a lateral. A simulation of an actual rural distribution feeder using the Electromagnetic Transients Program (EMTP) is used to test the approach. >

A fault location technique for rural distribution feeders

Concepts for adaptive protective relaying of transmission lines are presented. These include changes in online relay settings, relay characteristics, or logic in response to power system or environmental changes, or as a result of operating experience. Such changes as line-out or generator-out contingencies, which affect fault current distributions and degrade the system's security level, initiate adaptive protection system responses. Adaptive relaying is shown to be capable of improving relaying reliability and power system security and of achieving better utilization of transmission facilities. Most of the concepts require a hierarchical computer system, involving front-line parallel processors, a substation host, and remote central processors, all linked by channels that transmit data or relaying changes prior to or after a disturbance. It is suggested that maximum value from adaptive relaying will result from integration with existing or planned substation control and data acquisition functions and interfacing with the central energy management system (EMS). Emphasis is placed on use of interim hardware approaches to allow evolutionary development. >

Adaptive transmission relaying concepts for improved performance

Reach accuracy of a distance relay on transmission lines is adversely affected by fault resistance combined with remote-end infeed which is not measurable at the relaying point. Different network conditions correspond to different remote-end infeed behaviour and in conventional setting a safety margin is necessary so as to avoid maloperation. In this paper an adaptive setting concept which can overcome this disadvantage is proposed. A microprocessor based distance relay with this new technique can respond to network conditions that change from time to time and computer simulation has confirmed the validity of this new concept. >

Adaptive relay setting for stand-alone digital distance protection

A microprocessor based fault locator is described, which uses novel compensation techniques to improve accuracy. It displays the distance to the fault in percent of transmission line length, for facilitating repair and restoration following a permanent fault. Also, it pinpoints weak spots following transient faults.

An Accurate Fault Locator With Compensation For Apparent Reactance In The Fault Resistance Resulting From Remore-End Infeed

A method and a device for determining the distance from a measuring station to a fault on a transmission line based on a fault model of a transmission network while taking into consideration the zero-sequence impedance and, where assuming a fault current, while taking into consideration the feeding of fault current to the fault point from both ends of the transmission line (FIG. 3 ).

Method and a device for determining a fault on a transmission line

A method and a device for phase selection for single-pole tripping of high-impedance ground faults in direct grounded power networks. Starting from the ratio of the negative-sequence voltage to the zero-sequence current (U2/I0) and the ratio of the negative-sequence voltage to the positive-sequence voltage (U2/U1), two criteria with different conditions are formed, each of which indicating a faulted phase, and if both criteria indicate the same phase as faulted, single-pole tripping can take place.

Phase selection for ground fault

Method and means for fault location in a multi-terminal network consisting of a main power line having branch power lines leading from a number of tap points (A₁,...A(n-2)) to various consumer areas and where terminals (T₁,....Tn) exist in the end stations of both the main power line and the branch power lines, said terminals measuring the prevailing current (i₁,....in) and voltage (u₁,....un), which readings are transferred to and combined in a common calculation and evaluation unit (1) which calculates, with knowledge of the characteristic data of the line sections and branch lines and by using known methods, currents and voltages in all the tap points. By comparing the calculated voltage in a tap point departing from values measured in the terminals of adjacent line sections or from calculated values in the nearest tap points, it can be determined whether a fault exists in any main power line section or branch line.

Method and means for fault location in a multi-terminal network

A method and a device for identifying, when a fault has been detected in a power network, single-phase to ground faults by determining for each phase an auxiliary current based on the present phase current, ground fault current and ground current. If the difference between two consecutive, calculated values of the auxiliary current in some phase is smaller than a predetermined limit value, this means that there is a single ground fault in this phase.

Leif Eriksson

Papers

An Accurate Fault Locator With Compensation For Apparent Reactance In The Fault Resistance Resulting From Remore-End Infeed

Method and a device for determining a fault on a transmission line

Phase selection for ground fault

Method and means for fault location in a multi-terminal network

Method and device for identifying single ground faults