Electrical Cable Trunk Installation Work PDF Download
Design of MV network:
Design parameters:
Load :
The location or area covered by distribution network. A precised map of this location is useful and needed for the design. Road, streets, path and other infrastructures such as canal,..etc should be presented. The designed load is forecasted for 10 to 20 coming years. Therefore, to do this many data are needed, depending on method used in the calculation. For example, total number of families, infrastructures in the location, future vision of the economic and social growth etc; electricity source near or in the location: Power plant, MV feeder, grid substation; existing MV line. MV network parameters and service parameters: Voltage, Maximum power, power factor (Cos phi) Note: In design process, some assumptions should be made at the preliminary stage. For example the best scheme should have shortest length. On the reliability of the scheme, the standard of performance is required in the MV distribution network - the outage shall not last longer than 48 hours. The good practice indicates that the total power loss in MV network should in the range of 2-5%. In Cambodia, the MV voltage range is 22[kV] + 10% to 22[kV] - 10%. Electricity source for the design: MV line or grid substation feeder, stand alone network with own generation.
Load center of LV loads:
LV household loads are connected to LV network via LV distribution (meter) box on the pole installed along the road, street or path in the village/town. So, the LV loads are from the pole on the LV line trace. Load from each pole is displayed as a circle with center at the pole and radius proportionally to the load. In each zone on the map all the LV loads are represented by a centralized load located on the load center. This location should be the place for transformer post. However, in reality it is difficult to identify the load center, and the place of transformer is not optimized. The load center is an equivalent location where the moment is equal to the sum of all moments of all pole considered.
The design of MV line installation scheme is a professional job and requires experiences. Experienced people and technicians can refer to the theory in the last chapter of the handbook.
There are many types of MV pole: wooden pole, reinforced concrete pole, steel frame pole etc. The selection of pole type depends mostly on economic point of view. In practice in Cambodia, the optimum type of pole is reinforced concrete one. The height of the 22 kV pole is standardized as 12m and 14m.