The mechanical effects of short-circuit currents in - Montefiore

into account in the calculation. One must consider that
the value of tK = 0.1 s is of a rather theoretical nature.
Force / kN
Force / kN
100mm
200mm
400mm
110
100
Force / kN 60mm
90
80
70
60
1 spacer 3 spacers
55
84,6
55,2
83,1 83
54,7
50
40
40 39,6 39,8
30 26,3 26,3 26,4
20
10
110
100
90
80
70
20
10
0
0
0,1s 0,3s 0,5s
short-circuit duration
110
100
90
80
70
60
50
40
30
20
10
0
88
117,2 117,6 116,7
83,5
58,8 58 58,1
30,3 29,7
29,6
0,1s 0,3s 0,5s
short-circuit duration
1 spacer 3 spacers
60
55,9
50
40
30
42,9
30,2 31,8
27
41 40
3839,9
4140,8
41
110
100
90
80
70
40
30
20
10
0
60mm
100mm
200mm
400mm
60
56
50
47,2 46,8
35
0,1s 0,3s 0,5s
short-circuit duration
110
100
90
80
70
60
50
40
30
20
10
0
60mm
100mm
200mm
400mm
32 28 31
27
1 spacer 3 spacers
56,9
54 54
79,1
60,5 60
56,3
0,1s 0,3s 0,5s
short-circuit duration
78
86,4
41 40 42,8
38 40,8
40
50,6
0,1s 0,3s 0,5s
short-circuit duration
57,5
50
40
40 34,8
Figure 3.47 a, b, c Calculation results
a) Contraction maxima Fpi
b) Swing-out maxima Ft
c) Fall-of-span maxima Ff
110
100
90
80
70
60
30
20
10
0
79
55 54,7
71
89
60,6
58
0,1s 0,3s 0,5s
short-circuit duration
The contraction effect rises with the number of spacers
and the sub-conductor distance to become the relevant
short-circuit tension force at the suspension points for
three spacers at aT = 400 mm. The dependency of the
second and third maxima on the number of spacers must
be attributed to the reduction of sag (i.e. effective
conductor length available for the contraction) by the
contraction with increasing sub-conductor distance aT
and number of spacers nAH during the short-circuit. Also
the existence of the droppers may lead to a reduction of
the kinetic possibilities of the span during the swingout
and the fall-of-span phases, in particular.
In comparison to the above the same sequence is used
for the reactions at the foot of the towers and at the
transition to the foundation in Figure 3.48 a, b and c.
The static relation between the exciting tension force
70
62,9
106,5
56
and the considered reaction force at the tower foot is
1/6.2.
Of course the respective values of Figure 3.49 for equal
conditions must remain independent of the short-circuit
duration. The number of spacers and the sub-conductor
distance have severe effect on the reactions. The fall of
span is generally the more important against swing-out.
For up to 100 mm sub-conductor spacing aT, the
reaction to contraction is negligible against all other
maximum. Yet, if the calculation and, in particular, the
chosen damping is right, the contraction plays the
dominant role among the other maximums at aT = 200
mm and above. With one spacer and aT = 200 mm, the
ESL factor for contraction is slightly less than 1, while
for 400 mm it is 1.2. For a larger number of spacers the
factors are even higher.
Finally, the maximum spacer compression was
considered. Figure 3.48 gives the results of that calculation.
Spacer compression has lately come into
renewed interest through [Ref 54].