Search

Today high speed protection of power system elements is necessary and realizable. This paper introduces time-domain protection techniques for transmission lines using voltage and current signals in Cartesian coordinates. Three techniques are proposed using this approach for line protection. Direction of fault is obtained using change in angle between Cartesian planes of voltage and current. In the second application on unit protection scheme, internal and external faults in transmission lines are discriminated using dot product of the normals to both end current planes. Fault type identification is obtained using the angle between incremental changes in currents in Cartesian coordinates. The output of each protection function using the new concept is derived in a quarter-cycle. The performance of each of the proposed techniques is tested for load variation, high resistance fault, different fault types, power swing, fault inception angles and signal with noise. Further, the proposed techniques are evaluated using field data from a 400 kV double circuit line. [ABSTRACT FROM AUTHOR]

This paper proposes a traveling wave based scheme for wye-connected shunt capacitor bank protection. The proposed method provides high sensitivity and fast response, assisting in mitigating capacitor damage during internal cascading failure. The available protection schemes for capacitor bank use RMS values of voltage and current phasors for trip decision. Threshold selection is required in these methods which needs accurate estimation of equivalent capacitance of the bank. In addition, phasor being estimated from one-cycle running data window, such a method is slow. The proposed traveling wave based method identifies an internal fault in case of opposite polarities of traveling waves seen in the terminal voltage and current signals of the faulted phase. If the mid-point tapping is available in capacitor bank, the faulted half can be identified using the traveling wave of tap voltage. The magnitude of the traveling wave in terminal voltage reveals the number of failed capacitor elements. Such information assists in expediting maintenance. The performance of the proposed method is tested using PSCAD/EMTDC simulation data for various situations, including internal short circuit, external, and identical faults in the shunt capacitor bank. Comparative analysis highlights its higher sensitivity and better accuracy in comparison to available protection methods. [ABSTRACT FROM AUTHOR]

Converter interfaced distributed generations in a microgrid feed the modulated current of limited magnitude during fault conditions. The protection design and its operation are thus challenging due to limited fault current which is further reduced by Petersen coil grounding in medium‐voltage (MV) level. This paper aims to address this challenge by developing a current‐only directional relay algorithm for the protection of converter dominated MV microgrid with Petersen coil grounding. The relay's operating principle is based on the sign of the change in phase angle of the fault current with respect to the prefault which indicates the direction of fault. The negative and positive changes in current's phase angle determine the fault in forward and reverse direction, respectively. The tripping decision is derived by comparing the binary output of the relay at both ends of the line segment under protection. This requires a simple, flexible and low bandwidth communication channel. Both theoretical analyses and simulation studies have been performed on a typical distribution grid intended to be operated as microgrid. The proposed protection method is suitable for microgrid having the converters with and without reactive power support. Various operating conditions are evaluated, including bidirectional power flow, high resistance fault, different fault types, loading conditions and signals with noise. [ABSTRACT FROM AUTHOR]

This paper presents protection and fault location of wye-connected shunt capacitor banks used in medium or high voltage applications. The proposed method is sensitive to single element failure obtained by using voltage adaptive instantaneous superimposed current in each phase. The change in equivalent reactance computed using time-domain signals is used to find the number of failed capacitor element and types of fault. The location of the faulted capacitor is identified using sign of the voltage difference of the lower and upper halves of the shunt capacitor bank. The performance of the proposed method is tested for various cases including identical faults, simultaneous faults, system voltage unbalance in both single and double wye-connected shunt capacitor banks. The method is also validated using field data collected from a 400 kV SCB for an internal fault. The proposed technique is compared with available methods and found accurate. [ABSTRACT FROM AUTHOR]

A fast and accurate protection scheme for a dc microgrid enhances the service reliability and improves the power quality. A fault in any section of a dc microgrid results in oscillation in current, where its frequency is a function of fault position. The frequency and associated transient power of the first cycle of the oscillation are used for fault detection and faulted section identification, respectively. Based on the inverse-time transient power, a relay coordination scheme is proposed for the faulted section isolation in a dc ring bus microgrid. The maloperation of a relay due to the communication failure in the unit protection scheme can be averted by applying the proposed method using local data. The performance of the method is tested using data obtained from PSCAD/EMTDC simulations for numerous cases including bidirectional power flow situation, high fault resistance, and different fault types. The proposed algorithm is also validated on a scaled-down hardware setup in the laboratory. [ABSTRACT FROM AUTHOR]

In discussions of human-environmental dynamics and climate change, treatments of water usually focus on the problem of drought. Monsoon environments constitute a different set of parameters for landscape interactions because of seasonal episodes of water abundance. In this paper, we evaluate the microscale management of routine and anticipated high-water events for the ancient Indian subcontinent, where people used the monsoon cycle to engage in rice farming that in turn supported the growth of cities. Rice production would have encompassed two fluctuating inputs: rural labor, which may have become scarce when villagers left farmlands to become city dwellers; and water, the quantity of which varies dramatically on both a seasonal basis because of the monsoon and on an occasional basis because of tropical cyclones. The abundance of water (even with its risks of overabundance) encompassed numerous logistical challenges but also permitted high productivity within short distances of urban centers. The case study of the ancient city of Sisupalgarh in eastern India illustrates that high levels of productivity per land area enabled city residents to engage in short-distance economies for food production, while maintaining regional contacts through durable-goods trade to mitigate occasional episodes of crop failure in times of major flooding. [ABSTRACT FROM AUTHOR]

The potential benefits of direct current (DC) network in low‐voltage system promote smart grids and facilitate increasing penetration of distributed generation (DG). Correct identification of faulted section of a distribution network by an automation system reduces power outage time and improves reliability indices of such systems. With the onset of a fault in a DC distribution system, data recorded at an outage management system are used to identify the faulted section. With DG units active in a distribution system, there will be bidirectional power flow and faulted section identification becomes challenging. Using voltage and current data from consumer‐end smart meters and the substation, a method is proposed to identify the faulted section in DC distribution system. The Hadamard product of fault‐affected sections (obtained from network topology and voltage status matrices) is used to identify the faulted section correctly. Using power systems computer‐aided design/electro‐magnetic transient design and control simulation, the accuracy of the proposed method is verified for different fault situations including simultaneous faults, fault close to a bus and with rooftop photovoltaic integration to a DC distribution system. The method has the capability to provide information on the fault segment that connects feeder pillar to the consumer end also. [ABSTRACT FROM AUTHOR]

The least erroneous knowledge on fault location in distribution systems helps the restoration process, expedites maintenance, and reduces power outage duration. A fault-location method using the probe power unit (PPU) in dc microgrid assumes that the natural frequency of the system is equal to the damped resonant frequency of probe current. This assumption leads to prominent error in fault-location calculation. To estimate the location of fault in the low-voltage dc microgrid system, a noniterative fault-location technique using PPU is proposed in this paper. Considering damping frequency and attenuation of the probe current, which is a function of fault distance and damping coefficient, the fault location is obtained. The technique is tested for high-resistance fault as well as radial and looped topologies and is found to be more accurate. [ABSTRACT FROM AUTHOR]

With enhanced processing capacity and communication infrastructure available in smart grid platform, unit protection scheme is a promising technique. High resistance fault is a problem with current differential and current direction based unit protection solutions. In this letter, a protection scheme capable of fast fault detection and reliable selectivity for DC microgrid is proposed. The method uses superimposed currents of both ends of a line segment presented on $\Delta i$ -plane during fault to derive protection decision. Using PSCAD/EMTDC simulations, performance of the proposed method is evaluated, compared and found to be accurate. [ABSTRACT FROM AUTHOR]