The mechanical effects of short-circuit currents in - Montefiore

Both cases have the same 200-kV-arrangement, case 2
with single conductors and case 3 with close bundled
conductors. Figure 8.11 and Figure 8.12 give the results.
In Figure 8.11a, many results lie within the range ±25
%. In Figure 8.11a and Figure 8.12a, the marks above
+25 % show that the standard calculates values far on
the safe side; this is due to the fact that in some cases
the span rotates one or several times, see Figure 4.2 of
[Ref 1]. The measured second maximum of the force at
the bottom of the movement is lower than the force in a
span falling down from its highest position. When the
kinetic energy is exhausted a fall from the highest
position can occur and this is taken into account in the
standard. In addition, at the beginning of the fall down
the kinetic energy in the conductor is not zero which is
considered by the factor 1.2 in Equation (*35) of the
standard, see Section 4.2.4 of [Ref 1]. The results under
the –25 % line are only with low short-circuit forces
compared to the static force and also with short-circuit
durations less than 0,1 s.
a) b)
8
+25%
0 %
12
6
4
F c / F st
2
0
-25%
0 2 4 6 8
F m / F st
120
In both cases 2 and 3, the horizontal displacements had
only been measured in a few tests and are in good
agreement, Figure 8.11b and Figure 8.12b.
8.3.2. Strained conductors
Case *8 (FGH 1985)
The span length is 40 m, in case 8 with a single
conductor Al/St 537/53 and with single and bundled
conductors Al/St 537/53 and Al/St 1045/55. Figure
8.13a compares the maxima of F t and F f, including the
tests where the sub-conductors clash effectively. Only in
some tests, the sub-conductors do not clash effectively,
Figure 8.13b, but in the most cases, the swing out and
drop forces are decisive, Figure 8.13c. The horizontal
displacement b h is given in Figure 8.13d. A good
agreement is achieved.
10
8
6
F c / F st
4
Figure 8.10: Case 1: Short-circuit forces
a) Sub-conductors are clashing effectively (60 tests)
b) Sub-conductors do not clash effectively (78 tests)
2
0
+25
0 %
-25%
0 2 4 6 8 10 12
F m / F st