INFIPRO: Design and calculations for medium, high & extra-high voltage cables
Our software program INFIPRO will allow you to:
- Design medium, high and extra-high voltage cables
- Calculate short-circuit current
- Calculate current rating (100% load factor) and induced voltage
- Calculate cyclic and emergency current rating of cables
Contact us to know more and access a test demo.
Screen connection
The current that flows in the phase conductors, induce voltages in the cables screens. The level of the induced voltages depend on several factors, which can be summarized as:
- Current flowing through the conductor,
- the length of the circuit,
- the mutual inductance between conductors and screens, which is related to the separation of the single core cables and the screen radius.
Solidly Bonded
As a rule, we can state that the screens rigidly connected to earth (solidly bonded connection) almost eliminate induced voltage…
Conexión Single Point
In this connection system, the screens are connected to earth at one end, and the other end is isolated from earth by SVLs voltage limiters.
Double Single Point connection
The double single point connection ( or “mid-point bonding” connection ) is used when the length of the route is too long to use a connection end-point bonding.
Cross Bonding
Connection systems mentioned above are valid for relatively short lengths. But for long lengths, the cross-bonding system must be used.
Short-circuit current
The calculation of the maximum short circuit current in the conductor is performed according to standard IEC 949, “Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects”.
The short-circuit current is given by the expression:
where:
I: is the short-circuit current ;
IAD: is the short-circuit current calculated in an adiabatic hypothesis;
: is the factor which takes into account the loss of heat in the adjacent components.
Isc adiabatic calculation
The formula of adiabatic heating, is presented in the following general form:
Non adiabatic factor calculation
The general formula of an empirical equation for the factor is as follows non-adiabatic:
Screen calculation
For screens, the same method for calculating the maximum short circuit current can be applied.
In principle, one can not consider the influence of the metal sheet attached to the cable sheath, if any, or the influence of helically arranged strips equipotentia.
Is calculated for a wire taken individually and then multiplied by the number of wires for the total value of the short circuit.
Therefore can be used in all formulas wire section taken individually.