thermal loads for foundation design in 230 kV GIS

[arango]

Hello guys,

The following table presents the load combinations per node (anchoring point) provided for the design of a 230 kV GIS

Node Load Case Fx [kN] Fy [kN] Fz [kN]
01 DEAD LOAD 0,94 0,00 -6,76
01 TEMPERATURE -6,34 -0,14 34,69
02 DEAD LOAD -0,95 0,00 -6,67
02 TEMPERATURE -6,13 -0,14 -33,23
03 DEAD LOAD 0,00 -0,51 -3,83
03 TEMPERATURE -0,22 -3,70 -19,86
04 DEAD LOAD 0,00 0,49 -3,39
04 TEMPERATURE -0,22 -4,03 22,19
05 DEAD LOAD 0,28 0,00 -2,04
05 TEMPERATURE 2,87 -0,13 -15,43
06 DEAD LOAD -0,29 0,00 -2,09
06 TEMPERATURE 2,90 -0,13 15,70
07 DEAD LOAD -0,07 0,01 -6,88
07 TEMPERATURE -0,03 -2,33 -16,00
08 DEAD LOAD -0,03 0,01 -3,48
08 TEMPERATURE -5,77 -0,70 21,52
09 DEAD LOAD -0,07 0,04 -7,41
09 TEMPERATURE -0,05 -0,29 7,34
10 DEAD LOAD 0,00 0,02 -6,72
10 TEMPERATURE 1,76 -1,34 -10,38
11 DEAD LOAD 0,03 -0,01 -3,27
11 TEMPERATURE -0,23 0,27 27,26
12 DEAD LOAD 0,06 0,00 -3,14
12 TEMPERATURE 13,47 0,49 -25,99
13 DEAD LOAD 0,00 0,00 -8,28
13 TEMPERATURE 0,01 0,04 -0,24
14 DEAD LOAD 0,25 0,00 -1,91
14 TEMPERATURE -6,36 0,25 34,58
15 DEAD LOAD -0,27 0,00 -1,88
15 TEMPERATURE -6,19 0,25 -33,38
16 DEAD LOAD 0,00 -0,46 -3,33
16 TEMPERATURE -0,14 5,04 27,45
17 DEAD LOAD 0,00 0,47 -3,36
17 TEMPERATURE -0,14 4,91 -26,54
18 DEAD LOAD -0,07 -0,04 -7,45
18 TEMPERATURE -0,04 0,39 6,31
19 DEAD LOAD -0,01 -0,02 -6,68
19 TEMPERATURE 1,50 1,57 -9,80
20 DEAD LOAD 0,03 0,01 -3,30
20 TEMPERATURE -0,22 -0,33 26,35
21 DEAD LOAD 0,06 0,00 -3,12
21 TEMPERATURE 12,85 -0,58 -24,34


As you can see except for node 13, in all the other nodes the thermal loads are way bigger than the dead load (weight) of the equipment. I understand that due to pressure changes inside the GIS, the expansion joints make the housing expand or contract and these can lead to some load either downward or upward on the foundation, the problem is the magnitude of this thermal loads seem too high, even more, when a single bay's dead load is around 50 kN, and the max. thermal load in a single node is 34,69 kN upwards. I checked with another project using a completely different vendor, and the information shown in the load combination report is consistent in thermal force with such high values. Something more than changes on pressure must be behind this condition and I cannot fully understand it.

Can anybody explain to me where these loads are coming from? Any guide is more than welcome

Thanks.

 

[bacon4life]

I suspect it is the metal tank and conductors rather than the SF6 gas that causes higher loads during thermal extremes. I do not know if your values are typical for GIS. I AIS busses am more used to allowing space for thermal movement rather than providing clamping forces to prevent it.