How can I calculate the value of DC time constant or X/R ratio for overall system,and how can I reduce it's value?
X/R ratio based on the type of physical n/ws : Distribution & Transmission
It is low in case of distribution and high in transmission network.In load flow study, this X/R ratio plays a significant role in the convergence.
http://www.powerstudies.com/articles/ImportanceofX-over-Ratios.pdf
By measuring, we can find out its (R AND X )value in case of distribution network. I have one paper which will help to find out R and X in matlab.
The physical significant of DC time constant is to control the charging and discharging times of capacitor in RC circuits.
Mr Umesh to find R/X follow the below mentioned Algorithm:
Step 1: Measure V and I
Step 2: Substitute in this paper: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4840204&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4840204
Step 3: Run using MATLAB
This particular things becomes good research paper.
Dr Dhramasa
Power and Energy Expert.
Caledonian Engg. College (Affiliated to Glasgow-UK)
00968-95231621
Load flow method for radial and weakly-meshed networks: Concept of duality
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Athens/Shibboleth
This paper appears in:
Power Systems Conference and Exposition, 2009. PSCE '09. IEEE/PES
Date of Conference: 15-18 March 2009
Author(s): Dharmasa
SNIST-JNT U'ty, Ghatkesar, India
Radhakrishna, C. ; Jain, H.S. ; Reddy, P.P.
Page(s): 1 - 9
Product Type: Conference Publications
Available Formats Non-Member Price Member Price
PDF US$31.00 US$10.00
ABSTRACT
Load flow method suitable for both radial and weakly-meshed network structures common to distribution systems is proposed in this paper. Here the concept duality of network has been exploited to obtain the solution. Unique data feeding technique and creation of single matrix [branch-voltage drop to node-current] based on dual nature of the electrical network are used in the procedural technique. A single informative forward path impedance [FPI] matrix is developed in the proposed method and it is found to be adequate for the analysis. The method first arranges constant input data and then proceeds further by collecting the information about forward path-impedances in matrix form. Then identify the dual of forward path-impedance matrix, which gives backward nodal-current injection information about the network. The solution is derived using forward path impedance and branch currents. This methodology is programmed for an IEEE 15-Node network using MATLAB Ver. 7.0. and it is demostrated that computational efficiency has been improved by the algorithm suggested. This paper also includes equations for two real-world issues like, when lines are modeled as Pi section and for network having tap changing transformer. The proposed method is flexible to extend for 3-phase networks also.
Please note: Mr.Lokesh connection with R/X it plays an important in the in the distribution power flow analysis.Not not in transmission power analysis, because as P.S says it is more.
In Dis- Line R dominates
In Tran-Line X dominates
Now tell me, what are the practical reasons for the same using your basics.
www.journal.esrgroups.org/jes/papers/4_4_4.pdf
The results of above paper discuss on Graphical Information based Load flow analysis on for distribution neteworkd.oposed algorithm are compared with [23] and [29] for the
Here, it is programmed in MATLAB Ver. 7.01. In case high values of R/X the proposed method convergence results shows the results as tabulated in Table 3.4
The software packages used for the study, installed in the PC having specification as: 512MB-RAM, Intel Pentium IV-Processor, 1.73 GHz-Speed. The strength of the algorithm has been demonstrated by inclusion of branch losses along with the nodal powers in (3.8).The method are recommended based on the power injection calculation by using graphical based constant matrix [NLPL] useful for both loads and a losses calculation from (3.9) and nodal voltage obtained from (3.11). Thus the proposed method has been found to be superior in accuracy, number of iterations and efficient as per the comparison and the results given in Tables 3.2, 3.3 and 3.4.Hence the collection of graphical information is made easy to obtain the require results. Only one key matrix [NLPL] is sufficient obtain the power flow solution.
3.5 CONCLUSION
The simple directed paths in a graph are used as information for proposed algorithm to obtain sorted power flow solution. The method shows effective way of conversion of directed path nodal powers and branch powers losses into path powers in matrix form. The inclusion of branch loss during the power injection has been found that proposed method has fast convergence characteristics when compared to existing methods. The algorithm is found to be robust in nature as the values of R/X varies. The method can be easily extended to solve three phase networks also.
Significance of X/R ratio lies in determining the breaking capacities of CB during fault breaking contact parting, the higher the ration, the more onerous is the breaking capacities required.
To determine X/R for a network, work out all x & r from source to the point of system you are interested to find x/r and breaking capacities for CBs duties...
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