Power Factory Research Articles

Detection and classification of faults in transmission lines using the maximum wavelet singular value and Euclidean norm

In this study, a novel algorithm for detecting and classifying faults in high-voltage transmission lines is proposed. The algorithm is based on the discrete wavelet transform (DWT) and singular value decomposition (SVD). The DWT is used for extracting the currents’ high-frequency components under fault conditions. Signals under each fault condition are scaled in frequency, in order to build a wavelet matrix. By means of the SVD, the maximum singular value is calculated and employed in this proposal. The attained results exhibit that the maximum singular value represents a good indicator for the issue. This novel approach for detecting and classifying faults in power systems is called maximum wavelet singular value. Phase-to-ground, two-phase to ground, and three-phase faults’ simulations under different fault impedances are carried out by DIgSILENT Power Factory. The analysed fault conditions are evaluated demonstrating that the proposal reduces the computational burden and the time detection.

Islanding detection and load shedding scheme for radial distribution systems integrated with dispersed generations

This study presents a novel islanding detection and optimal load shedding scheme for radial distribution systems integrated with dispersed generation (DG). A simple and effective passive islanding detection method is developed based on the phase-space technique and using a probabilistic neural network-based classifier. After the system detects unintentional islanding state, it utilises an optimal load shedding scheme to prevent system collapse due to load-generation mismatch and voltage instability encountered in the islanded part of the system. The optimal load shedding scheme is developed based on the backtracking search algorithm. Extensive tests conducted with the DigSilent Power Factory® software and MATLAB® software on the IEEE 33-bus system with four DG units considering several scenarios of islanding condition were utilised to evaluate the effectiveness of the proposed islanding detection method and the optimal load shedding scheme. The results showed that the proposed method can effectively detect the islanding events and stabilise the islanded part of the system with minimum load curtailment.

Multi-Objective Distribution feeder reconfiguration to improve transient stability, and minimize power loss and operation cost using an enhanced evolutionary algorithm at the presence of distributed generations

Abstract This paper proposes a multi-objective evolutionary algorithm method for Distribution feeder reconfiguration (DFR) with distributed generators (DG) in a practical system. Considering the low inertia constant of DG units in order to take the transient stability of DGs into account is one of the major issues in power systems. Especially when the penetration of DGs is low, the impacts of them on the distribution system transient stability may be neglected. However, when the penetration of DG increases, the transient stability of them must be taken into account (more DGs, more transient issues). To this end, the DFR problem has been solve by an enhanced Gravitational Search Algorithm (EGSA) to improve the transient stability index and decrease losses and operation cost in a distribution test system with multiple micro-turbines. The effectiveness of the proposed approach is studied based on a typical 33-bus test system. For getting close to the practical condition and considering the detailed dynamic models of the generators and other electric devices in power system, simulation and programming of this approach are done by the DIgSILENT® Power Factory software.

Impacts of Low Voltage PEVs Single Phase Charging on Electrical Distribution Network

This paper presents impacts of low voltage PEV single phase charging on electrical distribution network. Simulation model and analysis tools under DigSILENT Power Factory program were used in this research. There are 5 case studies under this analysis, where each case operates at different charging time durations between 16.00 and 24.00. Assessment of the impact of PEV charging is performed based on the PEA standards. The simulation results show that all charging case studies increase line loading in the distribution network over the limit by 80%. The voltage at the upstream point of the feeder slightly dropped while at the downstream point dropped 4 times lower. Average line losses for all case studies increase approximately 13.36% compared to the base case study.

A Coordinated Voltage Control Scheme for Distribution Network with Renewable Sources

With significant penetration of renewable energy sources in distribution networks, the voltage control method may have to be revised especially during the light load condition. This paper presents a coordinated voltage control strategy to address this issue. A mixed-integer nonlinear optimal power flow was formulated and solved by Particle Swarm Optimization (PSO). All system constraints and operating limits are considered. The code was written using DigSILENT programming language (DPL) and implemented inside DigSILENT power factory simulation software. The proposed method can minimize generation curtailment to prevent overvoltage at any buses. A realistic distribution network was adopted to demonstrate the systems’ effectiveness. Simulation results show that all security constraints are maintained within operating limit. Power losses at the same time are minimized in comparison to the losses using the classical control method.

Artificial Neural Network Application in Optimal Coordination of Directional Overcurrent Protective Relays in Electrical Mesh Distribution Network

Directional Overcurrent relays (DOCR) applications in meshed distribution networks (MDN), eliminate short circuit fault current due to the topographical nature of the system. Effective and reliable coordination’s between primary and secondary relay pairs ensures effective coordination achievement. Otherwise, the risk of safety of lives and installations may be compromised alongside with system instability. This paper proposes an Artificial Neural Network (ANN) approach of optimizing the system operation response time of all DOCR within the network to address miscoordination problem due to wrong response time among adjacent DOCRs to the same fault. A modelled series of DOCRs in a simulated IEEE 8-bus test system in DigSilent Power Factory with extracted data from three phase short circuit fault analysis adapted in training a custom ANN. Hence, an improved optimized time is produced from the network output to eliminate miscoordination among the DOCRs.

Repairing compound damage in arid ecosystems – challenges and controversies

Using the Karoo as an example, we discuss past agricultural damage to the arid ecosystems, which is currently being followed by environmental changes and biodiversity losses associated with the new role of desert ecosystems as power factories (gas, uranium, wind and sun energy), mineral resources or retreats from the city. Development-related damage includes road building, vegetation clearing, soil compaction, water extraction and pollution. We present our views on prospects for ecologically and socially appropriate rehabilitation to rebuild complex and resilient ecosystems where recovery rate is constrained by aridity and rainfall unpredictability. We conclude that, to achieve intergenerational equity and conserve unique ecosystems, considerable investment in arid zone rehabilitation is needed to keep pace with the demands of a rapidly growing human population.

Transient Instantaneous Voltage Sag of Distributed Generation Bus in Muangxay Substation, Oudomxay Province, Laos

This paper presents the transient instantaneous voltage sag analysis of distributed generation (DG) in distribution system. The behavior of voltage sag is analyzed by using DigSILENT power factory software (DPFS). As affected by unsymmetrical fault of feeder 2, the calculation of initial condition carries out through instantaneous values (electromagnetic transients). The simulation results show that instantaneous voltage sag affects the DG and operation of electrical equipment. The phase short circuit affects the voltage waveform, varies from the original waveform and caused the flicker transient problem.

The Impact of Distributed Generation on Distribution Networks

Distributed Generators (DG or embedded generators) are generators that are connected to the distribution network. Their advantages are the ability to reduce or postpone the need for investment in the transmission and distribution infrastructure when optimally located; the ability to reduce technical losses within the transmission and distribution networks as well as general improvement in power quality and system reliability. This paper highlights the benefits of distributed generation by using a 15-bus radial distribution network, modelled in the DIgSILENT Power Factory software, to demonstrate the improvement in voltage profile as well as the reduction in technical losses. http://dx.doi.org/10.4314/njt.v34i2.17

Feasibility analysis of offshore wind power plants with DC collection grid

Offshore wind power plants (OWPPs) tend to be larger in size and distant from shore. It is widely accepted that for long distances HVDC links are preferred over HVAC transmission. Accordingly, one possible approach might be to consider not only a DC transmission system but also for the WPP collection grid. In this paper, a technical and economic comparison analysis of the conventional AC OWPP scheme and four proposed DC OWPPs topologies is addressed. Due to the conceptual novelty of DC technologies for OWPPs, uncertainty on electrical parameters and cost functions is relevant. A sensitivity analysis of the cost and efficiency of the components, OWPP rated power, export cable lengths and some economic data is carried out. For this study, a methodology is proposed and implemented in DIgSILENT Power Factory®. To compare conventional AC offshore collector grid and the various proposed DC configurations, an OWPP based on Horn's Rev wind farm is selected as base case. The analysis of the results shows that, in general terms, DC OWPPs present capital costs comparable with conventional AC OWPPs, as well as lower energy losses, concluding that DC collector grid could be of interest for future OWPP installations.

A performance comparison of single product kanban control systems

This paper presents a simulation experiment comparing the Single Stage, Single Product Base Stock (BS), Traditional Kanban Control System (TKCS) and Extended Kanban Control System (EKCS). The results showed that BS incurs the highest cost in all scenarios; while EKCS is found to be effective only in a very niche scenario. TKCS is still a very powerful factory management system to date; and EKCS did not perform exceptionally well. The only time EKCS did outperform TKCS was during low demand arrival rates and low Backorder (C b ) and Shortage costs (C s ). That is because during then, it holds no stock. The most important discovery made here is that EKCS becomes TKCS once it has base stock (or dispatched kanbans). The results have also evinced the strength of the pure kanban system, the TKCS over BS. Hence managers using BS should consider upgrading to TKCS to save cost.

Micro-Grid Smooth Switchover Method Based on Controller State Following

Micro-grid smooth switchover between different operation modes is important for steady operation and reliable power supply of micro-grid. In order to reduce the transient fluctuation of voltage and frequency during switchover, this paper proposed a new switchover method based on controller state following. When transferring to island mode, the control method for inverter of storage device changed from PQ control to V/f control. Before switchover, the output of V/f controller is always following the output of PQ controller. So that the sudden change of output is avoided at the moment of switchover. A micro-grid model with photovoltaic and battery is built on DIgSILENT Power Factory simulation software, to simulate micro-grid switchover from grid-connected mode to island mode. Results show this method can effectively suppress the transient fluctuation of voltage and frequency, and reduce the influence of transient process on power grid. This conclusion has important practical significance on micro-grid smooth switchover from grid-con- nected mode to island mode.

Generating Unit Model Validation and Calibration Through Synchrophasor Measurements

This paper presents a rule-based approach using synchrophasor measurements for generating unit model validation and calibration. The proposed method utilizes frequency and three-phase voltage signals recorded by phasor measurement unit at the point of common coupling of unit transformers to the high voltage grid. In the simulation setup, by taking the hybrid data simulation technique in use, the signals are being injected to the subsystem of generating units through a voltage source, which models the truncated external grid. The measured and simulated active power oscillations are then compared to each other and the effects of generating unit parameters on the oscillation mismatches are extracted. The maximum amplitude and damping ratio of oscillations are two main aspects of the observed mismatches. To recognize the most effective parameters on these aspects, a sensitivity analysis technique is applied. Next, identified parameters are adjusted to calibrate the generating unit dynamic model. Finally, quantitative and qualitative perspectives of the proposed method are investigated through different sorts of actual disturbances. The obtained results demonstrate that the final calibrated model outperforms the existing one, and it can be used for power system planning and operation studies. Time domain simulations are performed by DIgSILENT power factory software.

Impact of heat pump load on distribution networks

Heat pumps can provide domestic heating at a cost that is competitive with oil heating in particular. If the electricity supply contains a significant amount of renewable generation, a move from fossil fuel heating to heat pumps can reduce greenhouse gas emissions. The inherent thermal storage of heat pump installations can also provide the electricity supplier with valuable flexibility. The increase in heat pump installations in the UK and Europe in the last few years poses a challenge for low-voltage networks, because of the use of induction motors to drive the pump compressors. The induction motor load tends to depress voltage, especially on starting. The study includes experimental results, dynamic load modelling, comparison of experimental results and simulation results for various levels of heat pump deployment. The simulations are based on a generic test network designed to capture the main characteristics of UK distribution system practice. The simulations employ DIgSlILENT Power Factory to facilitate dynamic simulations that focus on starting current, voltage variations, active power, reactive power and switching transients.

Coordinated Control for an Offshore Wind Power Plant to Provide Fault Ride Through Capability

The operation of ac connected wind power plants equipped with full power converter wind turbines under deep voltage sags on the main ac grid is analyzed. It is identified that standard control schemes, based on the strict application of grid codes, can lead to instability problems when this kind of severe disturbances occurs. A coordinated control scheme is proposed to operate the system, ensuring fault ride through capability. An index alerts of instability proximity and allows to activate active power and reactive power regulation to guarantee safe operation during faults. This paper describes the proposed control approach and demonstrates its performance by means of dynamic simulations with DIgSILENT Power Factory.

Quantitative Characteristic of Meso-Damage Granite under Cyclic Loading with Different Frequencies

The failure damages of granite under cyclic fatigue load were caused by the propagation and coalescent of cracks at mesoscale, so it was helpful to understand the mechanical behaviours of rock by quantitatively investigating on meso-damage of granite. Stress amplitude of 10 MPa and sine wave cyclic loads with five different frequencies of 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1 Hz were adopted as dynamic disturbance. Then, the microtest (SEM) is carried out to study its fractography morphology and the meso-structural images of marble were processed by regional growing theory based on image processing technique. The meso-damage information of granite microcracks was obtained from SEM images. Quantitative analysis of meso-damage characteristics under cyclic fatigue load wase made from angle, length, width and area. The results showed that with the frequency of cyclic load increasing, the dispersion of microcrack growth azimuth value increased and the average of microcrack growth azimuth value fluctuated in the range. It is great helpful for seismic response analysis of the nuclear power factory in Chang Jiang.

Equating Permanence of Emission Reductions and Carbon Sequestration: Scientific and Economic Foundations for Policy Options

Terrestrial (biological) carbon sequestration is the process by which carbon dioxide (CO2) is removed from the atmosphere through photosynthesis and stored in terrestrial stocks of biomass or soil organic carbon. A ton of carbon (or CO2 equivalent) sequestered in terrestrial systems can be used as an offset credit against emissions from sources such as power plants, factories, or automobiles. However, carbon stored in terrestrial carbon pools is particularly susceptible to re-release (reversal), raising the so-called permanence issue. When a reversal occurs, crediting adjustments are necessary to restore the integrity of the offset mechanism. This paper explores the permanence issue from both an atmospheric and an economic perspective, showing that adjustments for reversals can depend on a variety of factors, including the assumed decay rate of the initial emissions pulse, the timing of any stored carbon release, a policy-determined “equivalency period” reflecting the relevant policy time horizon, the time-dependent economic value of carbon mitigation units, and the relevant discount rate for comparing economic flows over time.

Islanding detection in a distributed generation integrated power system using phase space technique and probabilistic neural network

The high penetration level of distributed generation (DG) provides numerous potential environmental benefits, such as high reliability, efficiency, and low carbon emissions. However, the effective detection of islanding and rapid DG disconnection is essential to avoid safety problems and equipment damage caused by the island mode operations of DGs. The common islanding protection technology is based on passive techniques that do not perturb the system but have large non-detection zones. This study attempts to develop a simple and effective passive islanding detection method with reference to a probabilistic neural network-based classifier, as well as utilizes the features extracted from three phase voltages seen at the DG terminal. This approach enables initial features to be obtained using the phase-space technique. This technique analyzes the time series in a higher dimensional space, revealing several hidden features of the original signal. Intensive simulations were conducted using the DigSilent Power Factory® software. Results show that the proposed islanding detection method using probabilistic neural network and phase-space technique is robust and capable of sensing the difference between the islanding condition and other system disturbances.

Distribution Automation in Case of Tie Bus between Two Feeders at Donekoy Substation in Laos

This paper proposesthe coordination between recloserandfuse link, reclosertorecloser, and recloserwith over current relay in tie feeder 1, 2ofDonekoy substationin Laos PDR.Disilent power factory software is used for simulation toimprove the operation of protective devicesand analyze the operating timein the distribution system.The operating coordination of recloser, fuse and overcurrent relayis improved. Resetting their functionality to limit the fault,the coordinating power aimsto reduce the problems of outages on distribution and also makes the system reliability.In case of maintenance circuit breaker, the 22 kV - tie bus applies to loads feeder 2 to ensure the stability power to appliances load of customers.Therecloser3 was installed on feeder 2 to protect the faults,and coordinates with recloser2 while the short circuit occursat fault2.

Time-Coordination-Based Fault Protection System for Power Distribution Network

In this paper, we present our study of the 22 kV power distribution network at Sisaket substation in Vientiane. Based on the simulation using Digsilent power factory software (DPFS), the protection device, particularly fuses and the reclosers, can be coordinated in time to better protect the system against both temporary and permanent faults, and consequently, the reliability of the system can be improved. Furthermore, the saving fuse and choosing the new protection device to prevent the distribution network is considered in this paper.