APPLICATION OF MSC NASTRAN UDS IN MODELING AND ANALYSIS OF HYBRID ALUMINUM COMPOSITES REINFORCED CONDUCTOR CORE Bo Jin [1] [2] , Dr. Wenning Liu [2] , Hemant Patel [2] , Dr. Steven Nutt [1] [1] M.C. Gill Composites Center, University of Southern California Los Angeles, CA, 90089 [2] NASTRAN Product Development, MSC Software Glendale, CA, 91203 [Abstract] MSC NASTRAN User Defined Services (UDS) and PATRAN were applied to perform load-displacement analysis of ACCC, a new type of power cable with hybrid composites reinforced core. PATRAN was used to model the geometry of the hybrid composites core, and MSC NASTRAN was implemented to analyze the load-displacement behavior of the structure. MSC NASTRAN UDS subroutine UMAT was used to provide user defined materials for enhanced material models in MSC NASTRAN Nonlinear Solution (SOL 400). ACCC core structural displacements under different loading conditions have been presented by post processing in PATRAN. 1. Introduction The North American Electric Reliability Corporation stated in 2008 that by 2017 there will be a 17% increase in electrical energy demand with only a 5% increase in electrical grid capacity [1]. While the increase of the area of power grid infrastructure is difficult due to the resistance from the public based on power stations and natural environments, as well as man power and land needed for infrastructure development, an alternative solution is to enhance the electrical infrastructure with more efficient overhead conductor cables which can meet higher electricity demands. The overhead conductors are designed to serve predefined mechanical and electrical loads, and they vary in size and stranding ratios which have similar electrical characteristics [2]. One type of a high voltage (approximately at around 100 kV) overhead conductor cable uses helically wound round 1350-19 high purity Al (high conductivity 61.2%) as the current carrying wires, with steel reinforced round wire core, is termed ACSR, for Aluminum Conductor Steel Reinforced. Comparing to the widely used traditional 1350 Al wire conductors, the ACSR steel core wire conductors have lower conductivity but higher strength, which provides less sag then the aluminum overhead conductor cables do, and allows the ACSR to be used in extreme environments such as strong wind or ice loading [2]. Comparison of both 1350 Al wire and the ACSR steel core’s properties, e.g. conductivity, coefficient of thermal expansion, elastic modulus and ultimate tensile strength, are shown in Table 1.
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APPLICATION OF MSC NASTRAN UDS IN MODELING
AND ANALYSIS OF HYBRID ALUMINUM COMPOSITES
REINFORCED CONDUCTOR CORE
Bo Jin [1] [2]
, Dr. Wenning Liu [2]
, Hemant Patel [2]
, Dr. Steven Nutt [1]
[1]
M.C. Gill Composites Center, University of Southern California
Los Angeles, CA, 90089 [2]
NASTRAN Product Development, MSC Software
Glendale, CA, 91203
[Abstract] MSC NASTRAN User Defined Services (UDS) and PATRAN were applied to perform
load-displacement analysis of ACCC, a new type of power cable with hybrid composites
reinforced core. PATRAN was used to model the geometry of the hybrid composites core, and
MSC NASTRAN was implemented to analyze the load-displacement behavior of the structure.
MSC NASTRAN UDS subroutine UMAT was used to provide user defined materials for
enhanced material models in MSC NASTRAN Nonlinear Solution (SOL 400). ACCC core
structural displacements under different loading conditions have been presented by post
processing in PATRAN.
1. Introduction
The North American Electric Reliability Corporation stated in 2008 that by 2017 there will be a 17%
increase in electrical energy demand with only a 5% increase in electrical grid capacity [1]. While
the increase of the area of power grid infrastructure is difficult due to the resistance from the
public based on power stations and natural environments, as well as man power and land needed
for infrastructure development, an alternative solution is to enhance the electrical infrastructure
with more efficient overhead conductor cables which can meet higher electricity demands.
The overhead conductors are designed to serve predefined mechanical and electrical loads, and
they vary in size and stranding ratios which have similar electrical characteristics [2]. One type of
a high voltage (approximately at around 100 kV) overhead conductor cable uses helically wound
round 1350-19 high purity Al (high conductivity 61.2%) as the current carrying wires, with steel
reinforced round wire core, is termed ACSR, for Aluminum Conductor Steel Reinforced.
Comparing to the widely used traditional 1350 Al wire conductors, the ACSR steel core wire
conductors have lower conductivity but higher strength, which provides less sag then the
aluminum overhead conductor cables do, and allows the ACSR to be used in extreme
environments such as strong wind or ice loading [2]. Comparison of both 1350 Al wire and the
ACSR steel core’s properties, e.g. conductivity, coefficient of thermal expansion, elastic modulus
and ultimate tensile strength, are shown in Table 1.
1350 Al Wire ACSR Steel Core
Conductivity 61.20% 8%
CTE (x10-6
/oC) 23 11.5
E (GPa) 69 200
UTS (GPa) 1.65 1.376
Table 1. Comparison of properties between 1350 Al wire and ACSR Steel Core
However, the ACSR steel core conductor is limited by operating temperature due to its high
coefficient of thermal expansion (CTE). Conductors are forced to carry higher currents while the
electricity demand is increasing. The higher currents lead to higher operating temperatures and the
energy generated consecutively contribute to the overall sag of the overhead conductor. Due to
prevention of black outs, short-circuiting and catastrophic events, the operating temperature of the
conductor is limited on purpose based on sag specification. By increasing the thermal rating of the
conductor will satisfy the electricity demands by increasing the ampacity (current carrying
capability) but hence also causes higher operating temperatures which induce sag and heat loss in
the overhead power lines. The CTE of steel reinforcement is 11.5x10-6
/oC thus during high
electricity demands the cable will expand and causing an increase in overall line length, as well as
inducing sag and greater heat losses because of the increased resistivity of the power line. The
parabola formula for calculating the sags [3] is shown below in Equation 1:
D =WS2
8H (1)
where W is the conductor weight per unit length (lb per ft), S is the Span length (ft), and H, as a
constant for each temperature, is the horizontal tension (lb).
The steel, which provides the structural support in the ACSR, also accounts for up to 40% of the
overall weight of the conductor [4].
In order to meet the current energy demands, a new type of overhead conductor cable termed
ACCC/TW for Aluminum Conductor Composite Core/Trapezoidal Wire was developed by
Composites Technology Corporation (CTC) and the primary design objectives were to increase
the overall strength of the conductor, rated ampacity and improve the sag at higher temperatures
when compared to the ACSR cable. The ACCC/TW is shown in Figure 1, and cross sectional area
shown in Figure 2.
This new type of hybrid composites conductor replaces the steel core with a hybrid composites
rod that utilizes unidirectional glass and carbon fibers in a common epoxy matrix. The ECR