The calculation is based on permissible tension method, which is used for the calculation once again because LineCross is a stand-alone program. Climatic conditions, maximum tension and tension at average annual temperature are taken from the justified mechanical calculation by LineMech. To calculate the crossings “manually”, it is necessary to perform the mechanical calculation as well.
The reference clearance (vertical distance) from the wire of an overhead line to the marks of the crossed object is defined (overcrossing):
When the crossed object is positioned above the wires (cords) of an overhead line (undercrossing):
The values for and - are taken from mechanical calculation for the mode of +15 ºС, no wind.
The values for and for defining - are taken from mechanical calculation for the mode of the maximum sag (at maximum temperature and ice without wind.
The value for is taken for the equivalent span. The equivalent span is the square root from the sum of cubic lengths of spans in the strain sector divided by the sum of the same spans. In this case the crossing span belongs to the strain sector. The required accuracy for the equivalent span is 1m. One can easily define , by setting a small range of spans in LineMech, including the equivalent span, with the pitch of 1 m.
To avoid possible confusion, the distance are input to LineCross from the left support.
The program verifies the maximum sag f max at +40ºСor at -5 (-10)ºСin case of ice accumulation. I.e. the program will automatically change the input temperature. This would mean that you defined the mode for the maximum sag in mechanical calculation incorrectly. If it is necessary to perform the calculation for these values, we recommend changing the value for the temperature by a tithe of the degree, for example, +39.9 ºС.
In breakdown mode (wire-break in the adjacent span) the sag is increased due the insufficient draw of the wire (reduced tension) due to shifting of insulator string and some deflection of supports depending on the elasticity of the supports’ material, as well as on the distance to the strain support.
If the span of the crossing occurs between strain supports and the wires are attached with the help of strain insulator strings (spur lines, descents on portals), in case low tension is accepted to low the loads on load-bearing constructions, it is necessary to account for the weight of the insulator strings, considerable influencing the sag.Кромеодновременногопереходаиподходапрограммапозволяетрассчитыватьнесколькопересекаемыхсооруженийводномпролёте.
Except for cases of simultaneous overcrossing and undercrossing, the program allows calculating several crossed objects in one span.
When calculating the crossings the spotting of the supports on the line profile is adjusted, the decisions on using shorter of higher supports are made.The requiresclearances, temperatures, and modes are taken according to EIR depending on the characteristics of the crossed objects and natural obstacles, provided the agreement of the interested organizations (owners of the objects).