Additional analysis

Additional analysis modules

Duct bank optimiser add-on module

Eaton's CYME Duct Bank Optimiser add-on module allows the user to determine the optimal placement of several circuits within a duct bank. More specifically, the module can recommend various circuit configurations within a duct bank so that:

• The duct bank overall ampacity, i.e. the sum of the ampacities for all circuits, is maximised or minimised
• The ampacity of any given circuit is maximised or minimised

For a 3 by 4 duct bank with three trefoils and one three-phase circuit (one phase per conduit), there are up to 665,280 possible combinations. The elaborate mathematical algorithm of the module prevents the repetitive calculation of equivalent cases, therefore the solution is efficiently obtained.

Magnetic fields

Eaton's CYME Magnetic Fields Module (EMF) is an add-on module to the CYMCAP software. After a steady-state ampacity or temperature simulation, the module computes the magnetic flux density at any point on or above the ground of an underground cable installation. The output is a plot (or a table) of magnetic flux density versus position. Modelling features include:

• Infinite-length, thin-wire, two-dimensional approach
• Consideration of time-varying currents producing an elliptically polarised rotating magnetic vector
• The currents in a three-phase circuit can be unbalanced (in magnitude and phase)
• All media is assumed homogenous, isotropic and linear
• The induced currents are neglected 

Cable impedance calculation

Eaton's CYME Cable Impedance Calculation add-on module (ZMat) calculates the electrical parameters for cables necessary for performing load flow and short-circuit studies at the power frequency (50/60 Hz). The calculation of impedances is performed after a steady-state ampacity or temperature simulation has been successfully completed. The final results are the positive and zero sequence impedances and admittances for all the cables present in the installation.

All impedance and admittance matrices are displayed in the report, starting from the primitive matrices per section per metallic component, then the bonding matrices, then the phase and circuit matrices and finally the resulting symmetrical components matrices.

The following features are supported:

• Computation of the sequence impedances and admittances for all cables present in an installation
• Multiple cables per phase are supported
  
• One or more neutrals can be represented and are taken into account in the calculations
• Resistivity of the soil can be changed

Short-circuit cable rating

Eaton's CYME Short-Circuit Cable Rating (SCR) add-on module is dedicated to the rating of cables for short-circuit currents. The implemented method is based on the IEC Standard 60949 (1988) “Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects.” The CYMCAP program computes both adiabatic and non-adiabatic ratings.

The module offers two possibilities, according to the known input data:

• Compute the maximum short-circuit current that a cable component can carry, given the short-circuit time together with the initial and final temperatures
• Compute the final temperature that a given cable component will reach for a specified short-circuit current, initial temperature and time interval

Short-circuit ratings can be computed for  all metallic layers supported in the CYMCAP software:

• Conductor
• Sheath
• Sheath reinforcement
• Concentric neutral/skid wires
• Armour

Circuits crossing

Eaton's CYME Circuits Crossing (Xing) add-on module allows the user to determine the steady-state ampacity of two circuits crossing each other.

When two circuits cross each other, each of them behaves as a heat source for the other one. The amount of generated heat, the vertical distance between the crossing circuits and the crossing angle are the main parameters that influence the crossing rating. In the absence of crossing calculations, the general practice is to use the conservative result where the circuits are assumed to be parallel. When the circuits are parallel, the thermal interaction is maximum. It goes to a minimum when they cross each other at a right angle. The conservative approach unnecessarily de-rates both circuits. By using the Circuits Crossing module, one can achieve ratings up to 20% higher than the conservative ampacities that are obtained based on the parallel installation scenario.

Modelling features include:

• Modelling of two circuits crossings each other in the same installation
• Circuits crossing directly buried underground, in buried ducts and in buried pipes underground
• Rating methodology as per the IEC standard 60287-3-3