CYMCAP - Cable Ampacity Calculations


The CYMCAP software is dedicated to the calculation of ampacity and temperature rise calculations for power cable installations. It addresses steady-state and transient thermal cable rating as per the analytical techniques described by Neher-McGrath and the IEC 287© and IEC 853© International standards. The accuracy of our software provides increased confidence when upgrading power cable installations and designing new ones; maximizing the benefits from the considerable capital investment associated with them. It also helps increase system reliability and support the proper utilization of the installed equipment.

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The CYMCAP software is dedicated to performing ampacity and temperature rise calculations for power cable installations. Determining the maximum current power cables can sustain without deterioration of any of their electrical properties is important for the design of electrical installations. It was developed jointly by Ontario Hydro (Hydro One), McMaster University and CYME International, under the auspices of the Canadian Electricity Association.

The field-tested accuracy of the CYMCAP software provides increased confidence when upgrading existing power cable installations and designing new ones, thus maximizing the benefits from the considerable capital investment associated with them.

Analytical Capabilities

  • Iterative techniques based on Neher-McGrath and IEC-60287© methods
  • Full compliance with North American practice and support all pertinent IEC standards IEC 60287©, IEC 60228©, IEC 601042©, IEC 60853©, etc.
  • Detailed graphical representation of virtually any type of power cable. This facility can be used to modify existing cables and enrich the cable library with new ones. This includes single-core, three-core, belted, pipe-type, submarine, sheathed, and armored cables
  • Different cable installation conditions such as directly buried, thermal backfill, underground ducts or duct banks
  • Pipe-type cables directly buried or in a thermal backfill
  • Independent libraries and databases for cables, duct-banks, load curves, heat sources and installations
  • Modeling of cables in air on riser poles, groups of cables in air, moisture migration, nearby heat sources and heat sinks, etc.
  • Different cable types within one installation
  • Non-isothermal earth surface modeling
  • Cyclic loading patterns as per IEC-60853©
  • Multiple cables per phase with proper modeling of the sheath mutual inductances which greatly influence circulating current losses and thus de-rates the ampacity of cables
  • All bonding arrangements for flat and triangular formations are supported with explicit modeling of minor section lengths, unequal cable spacing, etc.

Transient Analysis

The program supports a Transient Thermal Analysis Option which includes the following:

  • Ampacity given time and temperature.
  • Temperature analysis given time and ampacity.
  • Time to reach a given temperature, given the ampacity.
  • Ampacity and temperature analysis as a function of time.
  • User-defined load profiles per circuit.
  • Multiple cables per installation.
  • Circuits can be loaded simultaneously or one at a time.

Additional Optional Modules


The CYMCAP Additional Modules offer extended capabilities to the CYMCAP software, allowing modeling more installations, particularly non-standard installations. This includes the modeling of installations with multiple ductbanks and backfills of different thermal resistivity each; the calculation of the ampacity and temperature of cables in unventilated tunnels; the rating of cables in both filled and unfilled troughs; and the rating of cables in one or more non-magnetic casings.


The CYMCAP Additional Modules allow performing several analyses of interest for cables installations like evaluating the magnetic flux density at any point on or above the ground of an underground cable installation, determining the positive and zero sequence impedances and admittances for all the cables present in an installation, performing short-circuit cable ratings, determining the optimal placement of several circuits within a ductbank given specified constraints and calculating the ampacity of two circuits crossing each other.