MEP-PROJECTS GENERATES A NEW PROCESS OF CALCULATION OF CABLES IN BURIED CONCRETE GALLERIES
One of the most important aspects of electrical systems is the calculation of cables and, consequently, the choice of their layout. Efficient cable calculation can save significant amounts of money on new construction projects. Within the electrical engineering branch, this aspect can be solved by using different solutions expressed in the calculation criteria established in international standards such as IEC, IEEE, BS, etc.
MEP-Projects has recently developed cable installations in buried galleries – cable tunnels – mainly in the Arab states of the Persian Gulf. We are working with electrical levels of power supply for low and medium voltage, these installations, being in buried galleries, do not have a cable calculation procedure included in the standard commonly used in the Gulf area (IEC – International Electrotechnical Commission).
In order to be able to perform a standardized calculation using the method of airborne cables supported by electrical trays, we have developed an algorithm for our customers to know the internal temperature of the gallery based on the heat produced by the cables and the ambient temperature of the gallery. In this way we can select the coefficient of loss of ampacity derived from the final temperature of the medium.
The established solution is based on the following standards:
IEC 60287-1-1 Electric cables – Calculation of the current rating – Part 1-1: Current rating equations (100 % load factor) and calculation of losses – General
IEC 60287-1-2 Electric cables – Calculation of the current rating – Part 1: Current rating equations (100 % load factor) and calculations of losses – Section 2: Sheath eddy current loss factors for two circuits in flat formation
IEC 60287-1-3 Electric cables – Calculation of the current rating – Part 1-3: Current rating equations (100 % load factor) and calculation of losses – Current sharing between parallel single-core cables and calculation of circulating current losses
IEC 60287-2-1 Electric cables – Calculation of the current rating – Part 2: Thermal resistance – Section 1: Calculation of thermal resistance
