Conclusion
Through this report, the power distribution was introduced to show the stages of distributing and to show the importance of designing distribution substations for high-rise buildings, which are complicated in structure, to provide them with the required power to meet the demand. Also, a background about how the distribution started in the past for high rise building was presented.
A literature review about the most important components in the distribution substation which includes the transformer, generator, and feeders. The techniques of distributing the power inside the building vertically using risers or horizontally from the riser to the distribution boards or meters were demonstrated in the literature.
After that, the load criteria were studied for a specific building structure that includes thirteen floors to be able to design a distribution substation that can supply the building with electricity according to Kahramaa standards. First, the common load power was assumed using different approaches either by previous studies of similar buildings or by estimated equations. Then, the total power consumption was calculated for each residential floor. Finally, the power of the emergency load that consists of the necessary devices that should be in process in any kind of situation was determined. Moreover, the maximum demand of the whole building was obtained with the help of Kahramaa diversity factors and the building total load.
In the substation, a capacitor bank with an automatic controller is applied with 200 kVAR to correct the power factor of the building to 0.9 lagging and disconnect in case of a unity power factor. Based on the maximum demand obtained, a dry type transformer with a size of 1000kVA was installed in the substation to supply the low voltage panel with electricity and deliver it to the divided feeders or sub-main distribution boards. Additionally, for the emergency load that was found a backup diesel generator with a rating of 250kVA was utilized to maintain the operation of the load in case of emergency or blackout. To be able to calculate the voltage drop, the characteristics of the cables that connect the LVP with the SMDBs were found.
A protection system was planned to protect the high-rise building from any kind of fault that may occur and to stabilize the system by isolating the faulty components and keep the rest of the building working. Thus, a fault analysis was applied for the whole system to choose suitable protection devices that can be reliable and grantees the safety for the other electrical components and human beings. The protection system components include the circuit breaker and the current transformer.
A 1600A air circuit breaker (ACB) was chosen for the dry type transformer based on the transformer’s current carrying capacity. Moreover, the diesel generator was protected using moulded case circuit breaker (MCCB) which has a rating of 350A. The circuit breakers of the SMDBs were designed to be three phase MCCBs that vary from 40A to 350A, while the circuit breakers for the DBs were either
Design of Electrical Distribution and Protection Systems for A High-Rise Building
Department of Electrical Engineering Senior Design Project Report 42
single or three phase MCCBs depending on the rated current. Also, 630 A three phase MCCB was implemented for the riser.
Current transformers were employed for the metering of the dry type transformer and the diesel generator. According to Kahramaa standards, the CTs should be installed with the same rating as the circuit breakers. Hence, 1600/5 A CT was mounted for the transformer and 400/5A for the diesel generator.
The earthing system was designed to fit the constraints as the earthing resistivity should be less than 5Ω. The earthing system was divided into two main sections, for the whole building and the dry type transformer. The total resistivity for each system was found to be 3.46Ω with four rods. The earthing core size was determined for the two earthing systems as well as for the SMDBs that is almost half the size of the main cables.
Finally, AutoCAD software was simulated to illustrate the layout of the system and it can be said that the project complied with the constraints specified in the beginning, as well as applying Kahramaa standards for designing the distribution and protection systems.
The Impact of the Current Situation on the Project
In the wake of the unpredicted conditions happening around the world and the rapid increase in the number of people infected with the coronavirus. The government in Qatar decided to suspend classes for all students in the state of Qatar to ensure their safety and to reduce the number of new cases. This decision affected most of the SDP students since they cannot meet to test the hardware of their projects at the university or that the software that is being used for the project is not working at home. However, for this project, it was not affected because it is totally based on computations and calculations which can be done through distance learning using Excel and it does not depend on any prototyping or lab testing.
Recommendations for Future Work
To improve the high-rise building and make it more reliable a lightning protection system can be implemented to protect the building from strikes. In addition, transform the building into a smart building by utilizing sensors and actuators to control the process of the ventilation, air conditioning, lighting, and water heating of the building to minimize the power consumption of the building. As a result, the building will be more economical and more eco-friendly. Furthermore, solar panels can be planted at the roof as a second power source to reduce the effect on the environment.
