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Proc. of Int. Conf. on Control, Communication and Power Engineering 201010

Proposed Procedure for Determination of Heavily Loaded Branch of a Power Network Using Novel Voltage Stability Indicator on the Verge of Voltage Collapse Point Sumit Banerjee, Member IEEE 1, C.K. Chanda2, Pratap Sekhar Puhan2, Prosit Ghosh 1 ,Ruchira De 1 1

Dr B.C. Roy Engineering College/ Department of Electrical Engineering, Durgapur , India Email: sumit_9999@rediffmail.com, prosit_714@yahoo.com, ruchira.de@gmail.com 2 Bengal Engineering and Science University /Department of Electrical Engineering, Howrah, India Email: ckc_math@yahoo.com, puhan_samal@rediffmail.com Abstract— This paper presents a novel approach for determining the weakest branch or the heavily loaded branch of a power network on the verge of voltage collapse point. The proposed procedure for determination of heavily loaded branch of a power network using novel and unique voltage stability indicator at the proximity of voltage collapse point was tested on the simple IEEE 14 bus interconnected systems and significant results are observed to be in very good agreement.

load bus voltage of a power system within reactive loading index range [8]. II. THEORY We consider a simple 2-bus system as shown in figure 1.

V S = V S ∠δ S

Index Terms— Interconnected systems, Local voltage stability indicator, voltage collapse, voltage stability, weakest branch.

G

IS

VL = VL ∠δ L

Z S = Z S ∠α

IL

Z L = Z L ∠φ

I. INTRODUCTION Figure 1

Voltage stability [1,2] is a major concern for proper control and assessment of security of large power systems in contingency situation, specially in developing countries because of unusual growth of load demand and lacuna in the reactive power management side. It is mostly associated with ultimate voltage collapse which can appear in a distribution system [3-6] operating under the most heavy loading condition, so that the voltage decreases monotonically leading the system to be blackout. The problem of voltage collapse generates due to the inability of the power system to cope with its reactive power supply and demand , i.e., mismatch of reactive power generation and voltage [7,8]. Most of the low voltage distribution systems [3,4] having single feeding node and the structure of the network is mainly radial with some uniform and nonuniform tapings. Radial distribution systems [4,9] having a high resistance to reactance ratio, which causes a high power loss. Hence, the radial distribution system is one of the power systems, which may suffer from voltage instability. For a low voltage distribution system, the conventional Newton-Raphson method normally suffers

r Here a load having an impedance of Z L = Z L ∠φ is connected to a source through an impedance of r Z S = Z S ∠α . If line shunt admittances are neglected, the current flowing through the line equals the load current. From figure1, the current flowing through the line is given by,

IL =

VS ∠δ S − VL ∠δ L RS + jX S

(1)

The complex power is written as

S L = PL + jQL = VL I L* P − jQ P − jQ L or, IL = L * L = L VL ∠ − δ L VL

(2)

From (1) and (2)

VS ∠δ S − VL ∠δ L PL − jQL = VL ∠ − δ L RS + jX S

R from convergence problems due to high ratio of the X

[RS PL + X S QL ] + j[X S PL − RS QL ] = 2 VS VL [cos(δ S − δ L ) + j sin (δ S − δ L )] − VL

branches. This paper has developed a novel and new voltage stability margin indicator [10] of a low voltage distribution system to estimate the maximum permissible

200 © 2009 ACEEE

A simple equivalent 2-bus system of interconnected type of power system.

(3)

(4)


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