Electrical services design
Institution
Student name

Introduction
The need for electricity has been ever increasing. As well, the numbers of critical or sensitive loads have also increased. Today, the electricity transmission and distribution is greatly affected by this ever growing need. On the other hand, the consumer's demand has also been in a rising manner. These problems can be catered for by the use of energy storage devices, renewable energy and use of distributed generation.
Micro-grid paradigm can deal effectively with the ever increasing electricity needs. This paradigm is bestowed with the ability to regulate the electricity flow. This is achieved through the generation and distribution mechanisms. Grid refers to different interconnection of different electricity transmission lines. The line does not necessarily need to be transmitting electricity of equal magnitudes. But the electricity of different magnitude that runs from the highest to the lowest magnitude possible. In short, the grid connects the consumers to the electricity supply utilities (Vittal & Ayyanar, 2013, pg. 162).
The renewable energy integration into the main grid can take place in the distribution or at the transmission levels. The point at which integration takes place depends on the size or the scale of the electricity generation. Large generating stations directly feed the main grid. Unlike large generating stations, the small distributed generations feed the low or medium voltage lines. The design on each of the interconnection techniques to be used depends on the future and present challenges.

Discussion
Basic principle of operation
Heat
Recovery
System
Heat
Recovery
System
Micro-Turbine
(CHP)
Micro-Turbine
(CHP)
Distributed generation (DG) is composed of generation of power and interfacing with the main grid. Interfacing is achieved by use of inverters. Voltage sourced, and current controlled inverters are the devices that aid the interfacing process. DG units serve as auxiliary power sources. The units come into play at the moment of mains power loss. Interfacing the DG units with main generating plant serves to increase the efficiency and the reliability of the main power plant. In other words, DG units act as a backup at times when the mains supply is in isolation mode (Pota, 2010, pg. 357).

Power inverter
(12 VDC to 240 VAC)
Power inverter
(12 VDC to 240 VAC)
Change
Over
Switch
Change
Over
Switch
Mains
Supply
Mains
Supply

Children’s
Home
Building
Children’s
Home
Building

Figure 1: single line diagram of grid interfacing technology. The CHP system output both heat and electricity. If the electricity is in DC, it is inverted to AC. Heat recovery system recycles the waste heat energy.
The heat energy from the combustion process of the CHP system will be used for water heating in the children’s home building. The heat will also be used for general home heating, that is, during the cold seasons. Taking the example of 1,000 kW CHP system, the exhaust gasses can have a maximum of 600℃. This heat energy will be suitable for the heating purposes of the children’s home building.
The control scheme of the DG units that has been interfaced with mains grid constitutes several other circuits. These circuits are; the control circuit, resonance damping circuit, voltage controller and power flow controllers. Configuration and synchronization of the DGs are also part of the power control scheme.
Inversion and synchronizing processes
Power inversion takes place by converting direct current to alternating current power. Power electronics are used for this matter. The resulting AC power can be of three phase or single phase depending on its intended purpose. After rectification, power is fed to the grid or can be utilized directly.
Synchronization is the process that takes place before feeding the DG power into the main grid. At this point, the incoming power must meet any pre-set conditions for synchronism to take place. Otherwise, the synchronizing process fails (Johnstone, 2009, pg. 129). The pre-set conditions include; phase angle, frequency, and the incoming voltage. It is required that the magnitude of voltages from the both sides to be the same. The frequency of the incoming power together with the phase angle should also be of the same magnitude as the existing power in the grid.
Upon meeting the synchronization conditions, the AC breaker closes and, therefore, the incoming power gets into the flow along the grid. Power continues as much as the source is operational. The synchronization process takes place when the utility grid is working in parallel with the Dg unit. In case the two sources are independent, the DG unit only comes on when the main source is unavailable.
ETCI/ESB rules * On completion of the building electrical work, an electrical completion certificate will be obtained. Electrical work includes domestic wiring, industrial wiring or installation of any electrical device (Hossain & Pota, 2012, pg. 321). * A valid electronic, electrical completion certificate of the children’s home building will be provided to the ESB networks in order for the building to be connected to the grid. * The ESB requirement for any premise to be permanently identified for it to be connected to the supply utility will be ensured. All the mains circuits that are used to connect any device or buildings will be labeled. * All the ESB network equipment for the building will be provided with adequate space for the purpose of maintenance services. * The ESB Network meter will be installed before change over switches. * Safety devices such as isolators, meters, breakers and fuses will be labeled.

Mains power loss incidence
To be safe and to avoid inconveniences resulting from the mains supply failures the CHP units and the mains will operate independently. Change over switches that are automatically or manually operated will be employed in this case. The changeover switch would operate in such a way that sense the presence and absence of the mains. On mains absentia, the switch will trigger the CHP system to come into play. When the mains supply is restored, the same switch senses its presence and, therefore, de-energizes the DG unit (Hossain, 2012, pg. 91).
This type of power control is more reliable and effective since at no point power supply would miss. Also, to avoid failures by the DG unit, more units should be connected to operate in redundancy mode. The idea of independent operation of both the mains and the DGs together with their interfacing would greatly help even for the island units.
Specs and size of the technology
The chosen project for this technology is to supply a child's home building. The building has two floors; that is, ground and first floor with a total of 27 rooms. The mains supply is intended to be a priority at all times. The DG that could also be the black start or the standby the generator would only be used upon mains power failure. The intentions are that the whole building will be supplied by one mains supply switchboard. Then, each floor will have a sub-meter. The building will be supplied with a three-phase power. This means that the DG unit will also be producing a three phase power. DC power from the DG will be converted to three phase power with the aid of a three phase inverter (Harison, 2006, pg. 98).

Cost and prices of installation estimation Service & devices | Quantity | Cost/Price ($) | DG unit (micro-turbine for CHP) | 1 | 2,800.00 | Metering device | 1 | 50.00 | Inverter | 2 | 2,00.00 | Other devices (cables, switches, and breakers among others) | | 1,083.00 | Electrical devices(water heater (3 pieces),lighting devices (in house = 27*3 = 81 pcs, corridors and security lights = 30 pcs) andother relevant devices that are fit for children’s home) | | 1,222.00 | Installation labor | | 1,785.00 | Total cost | | 7,140.00 |
Table 1: Cost estimates
Suitability and unsuitability
The grid interfaced generation will be an advantage to the building. This is because all the power problems will be solved. If the technology of renewable micro-generation used, the building would be eco-friendly since renewable sources are environmentally friendly. The DG units will serve to raise the reliability of power supply utility.
The interface generation will also have some disadvantages. More programming procedures will be employed so as to implement a full function unit. Especially at the changeover or transfer switch junctions. The systems will require regular maintenance service. If several DG units placed in parallel are not implemented, the whole system would suffer unnecessary failures at some points of operation. The three phase power supply units would be more expensive as compared to single phase units.
Economic implications of interfaced generating
If the interface grid generation systems are designed and fully implemented, the power quality will increase. The cost of installing the independent units will be higher as compared to the installation of mains supply units alone. The cost of power would preferably go down. The reason being during the time when the atmospheric conditions are favorable, the renewable energy sources would be used instead of the mains supply. Despite the high initial cost, the interfaced grid generation is cheap as compared to other energy sources (George, 2011, pg. 231).
Conclusion
The objectives of the essay were met accordingly. The grid interfacing principle of operation and the techniques that are used to interface the grid and DGs were discussed. Inverter operations and synchronizing techniques were also discussed. The most important ESB and ETCI rules were also highlighted. The application process of grid interfacing technology was given some insight. At the incidence of mains power failure and during island modes, it was ensured that the supply would be changed to DG. Some unsuitability and suitability characters of grid interfacing were discussed. Lastly, the economic implications of the grid interfacing were discussed.
References
George, R. 2011. Constructing the ASCI computational grid. Washington, D.C: United States. Dept. of Energy ;.
Harison, K. 2006. Inverter for interfacing advanced energy sources to a utility grid. Oak Ridge, Tenn.: United States. Dept. of Energy. Office of Scientific and Technical Information.
Hossain, J., & Pota, H. 2012. Robust control for grid voltage stability: High penetration of renewable energy : Interfacing conventional and renewable power generation resources. Oxford: Oxford.
Johnstone, K. 2009. Interfacing interactive data analysis tools with the grid the PPDG CS-11 activity. Berkeley, Calif.: Lawrence Berkeley National Laboratory ;.
Kish, G. 2011. Addressing Future Grid Requirements for Distributed Energy Resources.
Pota, G. 2010. Application of a Suitable Control Strategy for Grid-Connected Inverters to the Power Management of a Microgrid. INTECH Open Access Publisher.
Vittal, V., & Ayyanar, R. 2013. Grid integration and dynamic impact of wind energy. New York, NY: Springer.