THE RELATIONSHIP BETWEEN THE BENDING AMPLITUDE AND
BENDING STRESS/STRAIN AT THE MOUTH OF A SO-CALLED SQUAREFACED
CLAMP FOR DIFFERENT CONDUCTOR SIZES AND DIFFERENT
TENSILE LOADS: EXPERIMENTAL APPROACH
(2013)Аннотация
In this research, realistic models were developed using experimental approach and statistical or
deterministic analysis in the relationship between bending amplitudes and bending stress (strain)
of the overhead line conductor. This was rigidity clamped and subjected to Aeolian vibration
(lHz-150 Hz). The experiments were performed at the Vibration Research and Testing Centre
(VRTC) laboratory of the University of KwaZulu-Natal. A shaker connected to the conductor
was used to simulate the Aeolian vibration and transducers (accelerometers, thermocouples and
strain-gauges) to control the shaker and collect data. For almost half a century, in transmission
lines, bending stress which is a key factor in determining the life expectancy prediction of
overhead conductor is assessed by using an idealized model the so-called Poffenberger-Swart
formula based on cantilever beam theory and many assumptions 2.
Four overhead line ACSR (Aluminum conductor steel-reinforced) conductors i.e. Rabbit (6 Al.
/lSt.), Pelican (18 Al. /lSt.), Tern (45 Al./7St.) and Bersfort(48 Al./7St.) were investigated at
three different ranges of tensile load i.e. 20 %, 25%, and 30% Ultimate Tensile Strength (UTS).
Bending amplitudes (0.0 lmm -l.2mm) and bending stresses measurements were collected and
plotted as bending stress crb versus bending amplitude Yb, curve-fitting with polynomial function
of the third order in terms of four parameters (where curve fitting coefficients Bo, 81, 82, and 83)
provided excellent simulations (predictions) of the experimental data for the conductors.
However, it was found that the accuracy of the fit is not improved by the inclusion of higher order
terms. Therefore, only four-parameters (for all cases high order than 3 are ambiguous, in spite of
the Regression parameter or predictor were R2 ~ 0.998 but Standard errors were large). It was
noticed that the precedent model is the simplest polynomial to be employed for the
characterization of all conductors investigated (for all three wires). Other ways to obtain the best
curve fittings were explored and discussed such as power model. The experimental results were
compared to the Poffenberger-Swart model. In all cases, it was observed that the deviation from
the results to the above model is significant for small bending amplitudes and is small for high
bending amplitudes and good correlations were observed when associated this with the bending
stiffness model developed by Papailiou 17.
