SES-Ampacity is a powerful tool that helps selecting appropriate conductors for grounding or transmission line design applications, based on the conductors’ thermal characteristics.
The program can compute the minimum conductor size needed to withstand a given current or can determine the conductor ampacity or the conductor temperature rise of bare buried conductors during a fault, or of overhead conductors during a fault or under steady-state conditions.
Conductor selection is a major factor that must be taken into account during the process of grounding or transmission line design. It is important that the most appropriate conductor type and size be selected for optimum operating efficiency. The electrical and thermal properties of conductors dictate the choice of conductor type and size for a given design. Factors such as environmental effects, electrical loss, current loading and many others must often be considered in the process.
SES-Ampacity offers two calculation modules that allow you to quickly estimate the required size of buried conductors or to simulate the thermal behavior of above-ground conductors.
A database stores the properties of conductors that are related to their thermal/electrical behavior for a large collection of conductors. This database can be extended with your own conductor data if the predefined ones do not meet your needs.
A user-friendly interface and facility of data entry make SES-Ampacity an efficient and useful tool for the conductor selection process in grounding and transmission-line design applications.
Bare Buried Conductor Module
The Bare Buried Conductor module can compute the following quantities:
- Minimum conductor size.
- Ampacity (i.e., maximum fault current rating).
- Temperature rise during a fault and final temperature after the fault.
The assumptions made in the calculations are as follows:
- No heat loss into the surrounding soil (i.e., the heating process is adiabatic)..
- The thermal capacity per unit volume (i.e., the product of specific heat and specific weight) of each conductor remains constant during the heating process: this is usually the case for fault durations on the order of a few seconds or less.
The basic equations used in this module are provided in ANSI/IEEE Standard 80 for the calculation of ampacity for symmetrical currents. To account for asymmetrical current characteristics (i.e., dc offset), the symmetrical current is increased in accordance with the decrement factor presented in the same standard.
Bare Overhead Conductor Module
The temperature of an overhead conductor that carries an electrical current is function not only of the magnitude of this current but also of several environmental factors that influence the amount of solar heating and the ability of the conductor to dissipate heat by convection and radiation.
The Bare Overhead Conductor module includes computation methods, based on the procedure described in IEEE Standard 738, relating electrical current to conductor temperature that are used in either of the following two ways:
- To calculate the conductor temperature when the electrical current is known.
- To calculate the current that yields a given maximum allowable conductor temperature.
For those two cases, SES-Ampacity can perform four different computations related to the thermal capacity of bare overhead conductors:
- Steady-State Thermal Rating given conductor temperature.
- Steady-State Conductor Temperature given load current.
- Thermal Rating after a step change in temperature.
- Conductor Temperature after a step change in current.
The results are presented in a report and include a graphical representation of the Temperature-Time curve in response to a step change in current when a Transient Conductor Temperature analysis has been performed.