Purpose
In recent years, innovative methodologies of product development such as lean product development (LPD) and agile project management (APM) have emerged. Even though previous research studies focused on these subjects, only few of them were focused on traditional industries, as civil construction. The purpose of this paper is to cover a part of this gap by estimating the potential of the application of these two new approaches (LPD and APM) in the construction industry, more specifically on the design stage.
Design/methodology/approach
For this, a case study has been conducted in order to understand if some of LPD and APM tools and practices had already been used, and also to evaluate the potential application of these new methodologies. Three Brazilian companies have been evaluated, all of them were exclusive executors of the design stage and presented distinct characteristics (size, structure, business model, etc.).
Findings
The results show that there is currently little adherence to LPD and APM practices within the companies studied. In terms of potential application of these new methodologies, the study has identified evidence regarding technical similarities between the reported cases and others mentioned in literature. However, the interviewees’ reception of these concepts was mostly pessimistic, showing considerable resistance to changes in the current process.
Originality/value
According to the analysis, the study identified that the main challenge/hampering to the implementation of these tools in the cases studied herein are the functional organizational structures, the customer–supplier relationships and the internal cultural resistance to change.
This work proposes two new approaches based on the ordinary least-squares method and the total least-squares method to estimate the parameters of a balanced three-phase transmission line using voltage and current measurements from phasor measurement unit. First, a new model for the steady-state phasorial equations of a medium-length transmission line is proposed. Then, the noises acting upon each measurement on the ordinary least-squares setup are considered, and for the total least-squares setup, noise acting upon the observation matrix in order to account for model uncertainties and non-linearities is also considered. The methods are tested in simulation data of a real medium-size transmission line.s The main goal is to compare both methods and show their complexities. The results show good performances for both methods and, indeed, the total least-squares setup had better performance than other reported total least-squares estimators, which use a different phasorial set of equations and oversimplified noise modelling. It is concluded that for the ordinary least-squares, the solution is well known and its behavior is predictable. While for the total least-squares, the solution requires more sophisticated methods of matrix decomposition and its behavior is not as predictable. Therefore the implications of these new approaches, where new considerations about the modelling of the noises are made and where a new phasorial set of equations is used are significant, given that the many works in the literature make use of these commonplace tools.
Transmission line parameters are usually calculated based on technical and environmental approximations, e.g. line height, cable conductivity, etc. These characteristics vary depending on the environment and technical issues, meaning that the transmission line should be considered as a dynamic system with time-varying parameters. Estimation methods are a useful way to determine line parameters taken into account such characteristics. Most methods estimate these parameters at 50 ∼ 60 Hz, useful for steady state analysis. However, for transient state or harmonic distortion analyses, a frequency range should be estimated, which varies according to the phenomenon to be investigated. In this matter, considering the gap existent of studies to estimate frequency-dependent parameters, we propose an efficacious and simplified method based on the two-port line representation and the well-known least squares method to estimate these parameters of a transmission line with 400 km length, considering a minimum number of synchronized measurements from 1 Hz up to 250 Hz.
The parameter estimation for transmission systems is important to power flow analysis, planning the expansion of electric power systems, stability, dispatch and economic analysis. This type of task is developed through systems identification methods, being the least squares method and its variations the most common techniques to obtain the transmission line parameters. However, these techniques have some disadvantages, such as non-recursive parameter estimation or the availability of an ideally transposed line, in order to address a problem with symmetric matrices, which simplifies the estimation process. In this paper, a non-linear method (Extended Kalman Filter) is presented to obtain the states of the transmission line terminals jointly with the vectorized matrix of parameters; such approach is strongly affected by the initial conditions; these conditions are usually obtained manually, which requires a lot of time and effort. Therefore, an optimization method (Particle Swarm Optimization) is applied in order to improve the convergence of the EKF, which reduces the time for adjusting the hyper-parameters and improves the estimated results. The proposed method showed accurate results for non-transposed systems, and also in comparison with results obtained from the same EKF-based method without the proposed optimization technique.
This paper proposes a complete and novel approach for estimation of impedance and admittance parameters of transmission lines from phasorial voltage and current measurements. The work uses the rigorous modeling of the noise on the phasorial measurements, and the solution is obtained based on a nonlinear approach of the estimation problem. The distortion introduced into the classical nonlinear model from the noisy data is analyzed by using statistical techniques. Finally, the performance of the estimation method is studied considering various load conditions, time-varying loads, number of samples, and noise on the phasorial measurements. The proposed method shows high accuracy in the line parameters estimation, even with distortions due to high noise levels. In addition, a good performance is also observed with a small quantity of samples, which is not observed in the linear solutions.INDEX TERMS Nonlinear least squares method, parameter estimation, phasor measurements, statistical analysis, overhead transmission lines.
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