# 9-Bus System (System I)

I. Introduction:

$$\bullet$$ In this test case, 9-bus interconnected distribution system with one single-end fed and equal impedances for all the lines is considered.
$$\bullet$$ This system has $$3\phi$$ fault at the midpoint of each line, as shown in the below figure, with no backup protection for relays $$\{R_{17},R_{19},R_{21},R_{23}\}$$.
$$\bullet$$ Bus 1 is supplied by a power source of  $$100 \text{ MVA}$$, $$33 \text{ kV}$$ with a source impedance of $$(0+j0.1) \ \text{p.u}$$. Also, the lines impedances are equal to $$(0+j0.2) \ \text{p.u}$$.
$$\bullet$$ All the directional overcurrent relays (DOCRs) have same CT ratio ($$CTR$$) of $$500:1$$, and all these DOCRs are considered to be numerical, in which both plug-setting ($$PS$$) and time-multiplier setting ($$TMS$$) are continuous.
$$\bullet$$ The lower and upper limits of $$PS$$ of each DOCR are calculated based on the following practical equaltions:
$$PS^{min}_{i} = \frac{OLF \times I_{n,i}}{CTR} \text{..... (1)}$$
$$PS^{max}_{i} = \frac{2}{3 CTR} I^{min}_{f,i} \text{..... (2)}$$
where $$I_{n,i}$$ is the nominal current rating of the circuit protected by the relay $$R_i$$. $$OLF$$ is the overload factor (with $$OLF=1.25$$), and $$I^{min}_{f,i}$$ is the minimum fault current that should be detected by the $$i$$th relay.
$$\bullet$$ In addition, relays $$\{R_{17},R_{19},R_{21},R_{23}\}$$ are assumed with no backup.
$$\bullet$$ Also, the minimum operating time of each relay $$T^{min}$$ is taken as 0.2 s.
$$\bullet$$ The rest data are given below (click on them for bigger size):

II. Single-Line Diagram:

$$\bullet$$ This single-line diagram was drawn by Ali R. Alroomi in Sept. 2013 and all the necessary data were coded in MATLAB m-files.

III. Files:

$$\bullet$$ System DATA (MATLAB, m-file Format) [Download]
$$\bullet$$ Results Tester (MATLAB, m-file Format) [Download]

IV. References (Some selected papers that use this system):

[1] P. Bedekar and S. Bhide, "Optimum Coordination of Directional Overcurrent Relays Using the Hybrid GA-NLP Approach," IEEE Transactions on Power Delivery, vol. 26, no. 1, pp. 109–119, Jan. 2011.
[2] F. Adelnia, Z. Moravej, and M. Farzinfar, "A New Formulation for Coordination of Directional Overcurrent Relays in Interconnected Networks," International Transactions on Electrical Energy Systems, vol. 25, no. 1, pp. 120–137, Nov. 2013.
[3] M. N. Alam, B. Das, and V. Pant, "A Comparative Study of Metaheuristic Optimization Approaches for Directional Overcurrent Relays Coordination," Electric Power Systems Research, vol. 128, pp. 39–52, Nov. 2015.
[4] F. A. Albasri, A. R. Alroomi, and J. H. Talaq, "Optimal Coordination of Directional Overcurrent Relays Using Biogeography-Based Optimization Algorithms," IEEE Transactions on Power Delivery, vol. 30, no. 4, pp. 903–911, 2015.