# Subject Name: POWER SYSTEMS-II

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Subject Name: POWER SYSTEMS-II
Topic Name : D.C. Distribution Systems Prepared By: Paresh R. Modha Asst. Professor, CSPIT, Changa.

DC Distribution Systems
For certain applications, d.c. supply is absolutely necessary. For example, d.c. supply is required for the operation of variable speed machinery (e.g. DC motors), electrochemical work and electric traction. Types of DC Distribution Systems are : (i) Distributor fed at one end (ii) Distributor fed at both ends (iii) Distributor fed at the centre (iv) Ring distributor.

Distributor Fed at one End

Distributor Fed at Two (both) End

(ii) Two ends fed with unequal voltages.

Example : 1 Ex. :1 : A 2-wire d.c. street mains AB, 600 m long is fed from both ends at 220 V. Loads of 20 A, 40 A, 50 A and 30 A are tapped at distances of 100m, 250m, 400m and 500 m from the end A respectively. If the area of X-section of distributor conductor is 1cm2, find the minimum consumer voltage. Take ρ = 1·7 × 10−6 Ω cm.

Solution of Ex : 1

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Example : 2

Solution :

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Distributor Fed at Centre :
In this type of feeding, the centre of the distributor is connected to the supply mains as shown in Fig. It is equivalent to two singly fed distributors, each distributor having a common feeding point and length equal to half of the total length.

Example : 3

Solution :

Ring mains Distributor systems :
In this type, the distributor is in the form of a closed ring as shown in Fig. It is equivalent to a straight distributor fed at both ends with equal voltages, the two ends being brought together to form a closed ring. The distributor ring may be fed at one or more than one point. each distributor having a common feeding point and length equal to half of the total length.

Example : 4 : A 2-wire D.C. Ring distributor is 300 m long and is fed at 240 V at point A. At point B, 150 m from A, a load of 120 A is taken and at C, 100 m in the opposite direction, a load of 80 A is taken. If the resistance per 100 m of single conductor is 0.03 Ω, find : (i) current in each section of distributor (ii) voltage at points B and C Solution :

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Actual Representation :

HOME WORK Example : (Self Study)

References [1] M. V. Despande, “Electrical Power System Design” , TMH Publication, New Delhi. [2] V. K. Mehta, “Principle of Power Systems”, S. Chand Publications. [3] B.R. Gupta, “Power System analysis and Design”, S. Chand Publications.

Asst. Professor, CSPIT, Changa.
Questions ? Thank You .. for Your Attention ..! Prepared By: Paresh R. Modha Asst. Professor, CSPIT, Changa.