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Volume-4, Issue-2, April-2014, ISSN No.: 2250-0758

International Journal of Engineering and Management Research Available at: www.ijemr.net

Page Number: 259-263

Particle Motion In Common Enclosure Three Phase Gib

L. Rajasekhar Goud1, M. Sivasatyanarayana2, D. Subbarayudu3, J. Amarnath4 1,2,3G.P.R.Engineering College(A), Kurnool, A.P. INDIA

4

Jawaharlal Nehru Technological University, Kukatpally, Hyderabad, A.P, INDIA

ABSTRACT

Gas Insulated substation (GIS) is now well established. In field installation, it has been observed that metallic particle contaminations often present in GIS and such contamination adversely affect the insulation integrity. A method based on particle motion is proposed to determine the particle trajectory in a three phase Gas Insulated Substation (GIS) or Gas Insulated Busduct (GIB). In order to determine the movement of particle in a GIB, an outer enclosure of diameter 500mm and inner conductor of diameter 59mm spaced equilaterally was considered. Aluminum and Copper wires of 0.1mm / 10mm were considered to be present on enclosure surface. The motion of the wire (particle) was simulated using the charge acquired by the particle, the macroscopic field at the particle site, the drag coefficient of restitution, Reynolds number and coefficient of restitution. The distance traveled by the particle, calculated using Cartesian coordinates, for given sets of parameters is presented in this paper. In order to determine the random behavior of moving particles, the calculation of movement in axial and radial directions was done at every time stem using rectangle random numbers. Typical results for aluminum and copper wire are also described in this paper. Keywords Particle movement, axial and radial movement, Monte-Carlo.

. I. INTRODUCTION

HE superior dielectric properties of Sulphur hexafluoride (SF6) have long been recognized for various high voltage applications. Compressed SF6

gas has been used as in insulating medium as well as arc quenching medium in electrical apparatus over a wide range of voltages. Due to the reliability of equipment, three phase common enclosure type Gas Insulated Busbuct (GIB) or Gas Insulated Substations (GIS) can be used for all services up to 500KV rating. This reduces space requirement, provides additional advantages of low maintenance and helps in cost saving. Conducting contamination could however, serious reduce the dielectric

strength of Gas Insulated System. Metallic particles in GIB / GIS have their origin mainly from the manufacturing process or they may originate from mechanical vibrations during shipment and service or thermal contraction or expansion at joints. Metallic particles can be either free to move in annular gap or they may be stuck either to the bus-bar or to an Insulator surface (spacer, busing etc.). If metallic particle will crosses the gap and comes in to contact with act as protrusion on the surface of the electrode. This may lead to reduction in breakdown strength of the gap. The present paper deals with the computer simulation of particle movement in three phase common enclosure movement in three phase common enclosure GIB. The specific work reported deals with the charge acquired by the particle due to macroscopic field at the tip of the particle, the force exerted by the field on the particle, the drag due to viscosity of the gas and random behavior during the movement. Wire like particles of aluminum as well as copper of a fixed geometry in a three-phase busbuct has been compared with the particle movement in a single-phase busduct. The movement pattern for three-phase busduct has been also obtained for higher voltages.

II. MODELING TECHNIQUE

Fig. 1 shows a typical horizontal three phase busduct comprising of inner conductors spaced equilaterally in a metal enclosure. The enclosure is filled with SF6 gas at high pressure. A particle is assumed to be at rest at the enclosure surface, just beneath the bus-bar A, until a voltage sufficient enough to lift the particle and move in the field, the particle lift and begins to move in the direction of field, the particle lifts and begins to move in the direction of field having overcome the forces due to its own weight and air drag. The simulation considers several parameters e.g. the macroscopic field at the surface of the particle, its weight, reynolds number, coefficient of restitution on its impact to enclosure and viscosity of the

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gas. During return flight, a new charge on the particle is assigned based on the instantaneous electric field.

Fig. 1 A typical three phase common enclosure GIB A, B,

C are the conductors

III. THEORETICAL STUDY

The primary goal of the simulations was to create an appropriate mathematical model of the particle motion in a three phase common enclosure GIS, which will enable further simulations of the motion of particle with arbitrary shapes. Several authors [1]-[11] have suggested solutions for the motion of a sphere or a wire like metallic particle in an isolated busbuct system. The theory of the particle charge and the electrostatic force on the particle is discussed in [1]-[6].

The motion equation is given by m dy

IV. SIMULATION OF ELECTRICAL FIELD IN TREE PHASE

BUSDUCT

= Fe - mg - Fd (1) dt Where, y is the direction of motion and Fd is drag force.

The direction of the drag force is always opposed to the direction of motion. For laminar flow the drag force component around the hemispherical ends of the particle is due to shock and skin friction. Very limited publication is available [7] for the movement for the movement of particle in three-phase busduct, however of equation of motion is considered to be same as that an isolated phase busduct.

The charge acquired by a vertical wire particle in

contact with a bare enclosure can be expressed as given by [1].

The electrical field in a three phase common enclosure GIB electrode system at the position of the particle can be written as:

E(t) = E1(t) + E2(t) + E3(t) Where E(t) is the resultant field in vertical wire

direction due to three conductors on the surface of the particle at the enclosure.

E1(t), E2(t) and E3(t) are the components of the electrical filed in vertical direction. The gravitational force and drag forces are considered as described by several authors.

V. SIMULATION OF PARTICLE MOTION

Computer simulation of the motion of metallic wire particles were particles were carried motion out on GIB of 64mm inner diameter for each phase and 500mm outer diameter with 245KV applied to inner conductors with appropriate phase difference.

A conducting particle motion, in an external electrical field will be subjected to a collective influence of several forces. The forces may be divided into [8]-[10]

Electrical force (Fc) Gravitational force (mg) Drag force (Fd)

Software was developed in C language considering the above equations and was used for all simulation studies.

VI. RESULTS AND DISCUSSIONS Table1 shows the movement of aluminum,copper and

silver particles at voltages of 300kv ,400kv,450kvand 500 KV. It is noticed that even for a voltage of 300kv the Ag particle could not leave the surface. This is expected due to lower field experienced in the three phase common enclosure GIB and heavier mass of silver. Graphical representation of radial movement in relation to time is given in Fig. 2. The simulations have also been carried out for an applied voltage of 500 KV with inner and outer diameters of the same dimensions. Based on above calculation the maximum movement of aluminum particle is found to be 99.1379mm and the same figure for copper is 28.89mm and for silver is 24.57mm respectively.

Table 1: Axial and Radial movement (mm) of Aluminum

and copper Particle in three phase GIB: Simulation time: 2 sec.

Voltage (kV)

Type

Max. Radial Movement(m

m)

Monte-Carlo ( 1 deg )

Axial(mm)

300 Al Cu Ag

33.56296 6.699295

N.M

462.4143 129.9625

N.M

33.56296 6.699295

N.M

400 Al Cu Ag

63.09916 15.07431 12.3704

738.0992 155.6658 244.188

63.09916 15.07431 12.3704

450 Al Cu Ag

81.00259 26.27919 20.27831

627.1832 419.7195 384.2483

81.00259 26.27919 20.27831

500 Al Cu Ag

99.1379 28.894

24.57452

809.3762 461.8137 492.2445

99.1379 28.894

24.57452

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Fig.6.1: Particle movement in three-phase GIB (300 KV/

Al/0.1/10mm)

Fig. 6.2; Particle movement in three-phase GIB (300 KV/ CU/0.1/10mm)

0

20

40

60

80

100

120

0 0.2 0.4 0.6 0.8 1

Mov

emen

t(m

m)

Time(sec)

Fig.6.3: Particle movement in three-phase GIB (500 KV/ AL/0.1/10mm

Fig.6.4 : Particle movement in three-phase GIB (500 KV/

CU/0.1/10mm)

Fig. 6.5: Particle movement in three-phase GIB (500 KV/

Ag /0.1/10mm)

Figure 6.6: Axial and Radial Movement in a 3-phase GIB (300

KV/ AL/0.1/10mm)

Figure6.7: Axial and Radial Movement in a 3-phase

GIB(500kV/ AL/0.1/10mm)

0

5

10

15

20

25

30

35

0 100 200 300 400 500

Rad

ial M

ovem

ent(m

m)

Axial Movement(mm)

Figure 6.8: Axial and Radial Movement in a 3-phase

GIB( 500kV / CU/0.1/10mm)

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Figure6.9: Axial and Radial