The mechanical effects of short-circuit currents in - Montefiore

More documents

Recommendations

Info

The first case (Figure 5.14) corresponded to the dynamic response of a system to a degree of freedom at a constant Laplace force. The second case (Figure 5.15) may be resolved through a purely functional approach or by modal superposition. 7.2.3.2.2.5. Reclosure When a structure has been set in motion by an initial fault, the possibility of a recurring fault after reclosure may lead to increased mechanical stresses. Between the maximum loads due to the first fault and the maximum loads resulting from the two faults, there may be a build-up factor of as much as 1.8 [Ref 95]. Nevertheless, a fault recurs at reclosure roughly one out of ten times. One property, superposition, will be particularly useful in studying reclosure. PROPERTY OF SUPERPOSITION The displacement of the system is linked to the excitation force by a linear differential operator L and denoted in the following manner: r r FL ( t) during the short circuit (5.16) L ⋅ U = r 0 outside the short circuit Following a first fault, for a definite force F () t , a L fixed short-circuit intensity, voltage phase and circuit time constant, and for a given fault duration, only one physical solution describes the system's displacement over time on the basis of initial break conditions. r r r r (5.17) U( M, 0 ) = o ∀ M r where: M : spatial variables. Following a second fault, the system's response is the superposition of the dynamic responses of the faults over an initial break condition with, however, a time lag tR corresponding to the reclosure time: r r r r r r (5.18) U( M, t) = U1( M, t) + U2 ( M, t −tR) r r r r where U M , t) and U ( M , t) satisfy (7.16). 1( 2 Because of this lag property, the search for the maximum following the two short-circuit faults is simplified. In order to superimpose two staggered faults and calculate their optimum, all that is needed is to characterize the dynamic response of a rigid structure to each of them separately. Where the two faults are of the same type, amplitude and duration, this superposition principle is especially useful. 86 7.2.3.2.2.6. Combined Loads Each company has to define its own design policy in accordance with the occurrence of extreme loads. We propose here to examine the case of combined shortcircuit and wind loads. The action of the wind on the busbars depends on the angle of the wind's direction relative to the tube axis, whereas that relative to the insulating bushings is constant for a given wind velocity, despite its changing orientation. The maximum dynamic response thus varies according to the following formula (5.19) :
(5.19) ( ) ( ϕ ϕ ) 2 ⎛ 1+ m.cos − 2 FI, ϕ, V, θ = ⎜α. I. ⎝ 1+ m Where: α, β', β'', γ and m are coefficients that depend on the geometry of the problem and on the mechanical properties of the components, I is the short-circuit intensity, ϕ is the short-circuit current phase at the instant of occurrence of the fault, V is the wind velocity, θ gives the direction of the wind relative to the tube (axis Oy in our case), ϕ 0 is the maximum asymmetry phase, γ corresponds to the deadweight. Coefficients m, α, β’, β’’ and γ are obtained by studying the maximum dynamic variations and the initial, and thus static, component, of the dynamic response; from the perspective of the maximum and then minimum asymmetry, a wind is applied statically perpendicular or parallel to the busbars. 7.2.3.2.2.7. Influence of the Operating Configurations a) Transfer Situation Furthermore, the risks linked to cases of current parallelism need to be analyzed in the event of two busbar faults (see paragraph. 2.3.2) occurring in a transfer situation (a single line on a section of bars, for which the protections may be shifted to the coupling bay), as outlined in the flow chart below: COUPLING BAY BAY 1 BAY 2 BAY 3 FAULTY BAY b) Transfer Proximity Of all the possible layouts, those close to the transfer situation of a low input line should be avoided. In the diagram below, based on a 400-kW network, lowinput line 6 (low I 10) and autotransformer (ATR 4) are connected to the same section of bars. Under such conditions, I 8 and I 9 are at maximum and virtually equal to the substation Icc. The loads may then be very similar to those calculated for the transfer situation. ⎞ 2 + β'. V .cos ( θ) + β''. V .cos( θ) ⎟ + ( β''. V .sin( θ) + γ) ⎠ 0 2 2 2 87 2 ATR 3 LINE 5 ATR 2 LINE 4 LINE 3 I8 I7 I6 I5 I4 I3 COUPLING 2 COUPLING 1 analysed zone I8 I9 I1 I2 I3 ATR4 LINE6 LINE1 ATR1 LINE2 ou LINE I10 This situation does not balance the power sources and demand centers, and is therefore extremely rare. c) Operating Situation Cases of Ring Structures In the event of operation with a single electric node, the currents are distributed proportionally to the impedances encountered and thus depend essentially on the length of the circuits. The result is generally a marked reduction in electrodynamic stresses, which account for nearly a quarter of the design loads. In this case, the resistance limits will depend more on the resistance of the transverse busbars or the apparatus. 2 one node In the event of two-node operation, when the end coupling(s) delimit(s) the two nodes, the reduction is quite significant, since the factor reducing the electrodynamic stresses is high. node 1 node 2 Case of U-shaped Structures Two-node operation comes down to the same case as above. In the case of single electric node operation, the power inputs (lines or transformers) and demand
Page 1 and 2:
THE MECHANICAL EFFECTS OF SHORT-CIR
Page 3 and 4:
3.7. Special problems .............
Page 5 and 6:
1. INTRODUCTION 1.1. GENERAL PRESEN
Page 7 and 8:
The pinch (first maximum) can be ve
Page 9 and 10:
1.3.3.2 Supporting structures Simil
Page 11 and 12:
This method allows to state the sho
Page 13 and 14:
and becomes the static force in equ
Page 15 and 16:
(2.26) M el-pl ⎡ y d/ 2 y = 2⎢
Page 17 and 18:
V σ 3 2,5 2 1,5 1 mechanical reson
Page 19 and 20:
V F 3 2,5 2 1,5 1 mechanical resona
Page 21 and 22:
1. eigenmode 2. eigenmode 3. eigenm
Page 23 and 24:
(2.43) U E max max = 1 2 1 = 2 l
Page 25 and 26:
m (2.47) M = σm = Z mσ m dm 2 J w
Page 27 and 28:
profiles in Figure 2.14 it follows
Page 29 and 30:
(2.71) 2 tube tube 4 tube U ∂U
Page 31 and 32:
2.3.2. Influence of two busbars a)
Page 33 and 34:
Asymmetrical associated-phase layou
Page 35 and 36: d)Methods used IEC 60865 method : -
Page 37 and 38: Section 3.4 deals with the effects
Page 39 and 40: In Figure 3.5 to Figure 3.8, the ma
Page 41 and 42: Figure 3.17 Comparison calculated a
Page 43 and 44: movement of the dropper (swing out
Page 45 and 46: This value has to be compared with
Page 47 and 48: EN 60865-1 [Ref 3] with the assumpt
Page 49 and 50: a) b) c) 3 m 2 1 0 -1 δ m δ 1 Mov
Page 51 and 52: Droppers with fixed upper ends Duri
Page 53 and 54: Manuzio developed a simplified meth
Page 55 and 56: From prior tests the stiffness valu
Page 57 and 58: Force / kN Force / kN 100mm 200mm 4
Page 59 and 60: 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 ESL F
Page 61 and 62: 3.7. SPECIAL PROBLEMS 3.7.1. Auto-r
Page 63 and 64: for the maximum outswing and the ma
Page 65 and 66: Zug-/Druck-Kraft in kN Z eit in s F
Page 67 and 68: The numerical resolution of these e
Page 69 and 70: 4. GUIDELINES FOR DESIGN AND UPRATI
Page 71 and 72: standards and tested under specifie
Page 73 and 74: 5. PROBABILISTIC APPROACH TO SHORT-
Page 75: f G f(L) Lt Ls 75 G(L) ∞ R = ∫
Page 78 and 79: Only the lowest break values are im
Page 80 and 81: 5.2.2. A global Approach For analyz
Page 82 and 83: to multinode operation can compared
Page 84 and 85: 5.2.3.1.7. Proposed Approach The st
Page 88 and 89: centers are normally balanced by ba
Page 90 and 91: Remark: The risk integral (5.3) can
Page 92 and 93: 1,0 0,8 0,6 0,4 0,2 0,0 -0,2 -0,4 -
Page 94 and 95: The histograms below for the instan
Page 96 and 97: 5.2.3.8.2. Reliability based design
Page 98 and 99: power converter in a three phase br
Page 100 and 101: The time functions of the currents
Page 102 and 103: a) Determination of the linear mome
Page 104 and 105: Figure 6.11 Coefficients mJs1 and m
Page 106 and 107: 7. REFERENCES Ref 1. IEC TC 73/CIGR
Page 108 and 109: Ref 42. Stein, N.; Miri, A.M.; Meye
Page 110 and 111: Ref 80. Fiabilité des structures d
Page 112 and 113: 8. ANNEX 8.1. THE EQUIVALENT STATIC
Page 114 and 115: Figure 8.2 What is ESL in this case
Page 116 and 117: As the eigenfrequency of the portal
Page 118 and 119: Figure 8.9 Case 3 (third eigenfrequ
Page 120 and 121: Both cases have the same 200-kV-arr
Page 122 and 123: a) c) 5 +25 % 0 % 4 3 F c / F st 2
Page 124 and 125: a) b) 24 kN 20 +25 % 0 % 2,0 m F c
Page 126 and 127: Case *11 (EDF 1990) This is the 102
Page 128 and 129: 8.4. INFLUENCE OF THE RECLOSURE The
Page 130 and 131: ( ( δ ) ( δ ) ) T = Mg08 . b r .
Page 132 and 133: IEC 60865 Calculations If the clear
Page 134 and 135: 8.6.1.1 With calculation of the rel
Page 136 and 137:
f) Calculation of the stresses due
Page 138 and 139:
d) Determination of the forces at t
Page 140 and 141:
8.7. ERRATA TO BROCHURE NO 105 In V
show all

The mechanical effects of short-circuit currents in - Montefiore

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?