Design of grounding system to protect against lightning and fault is important for both safety and reliability especially for Metropolitan Electricity Authority (MEA) as mostly Metropolitan Electricity Authority operates on overhead networks. This thesis assesses lightning performance for 69 kV 115 kV overhead subtransmission lines 24 kV distribution line using case study from Metropolitan Electricity Authority. Because of the limitation of the right of way distribution feeders are regularly installed together with subtransmission lines in a single concrete pole. Overhead Ground Wire (OHGW) installed at top of the pole and grounding system in concrete pole protects fault current or direct lightning surge to ground. Metropolitan Electricity Authority has developed lightning protection based on an IEEE standard which uses international data for insulation coordination. As a result reliability of the system is lower than the designed value. This thesis suggests a methodology to improve the performance in order to increase the reliability of subtransmission and distribution lines feeding distribution substations. This thesis recommends installation of addition external ground wire on the outer surface of the concrete pole to reduce top pole voltage and back flashover rate or installation of bundle overhead ground wires to protect shielding failure. As all the case studies presented in the thesis which constitute this thesis are applied to existing systems of Metropolitan Electricity Authority it is expected that the proposed methodologies can be served as useful practical guidelines for lightning performance assessment subtransmission lines and distribution lines of Metropolitan Electricity Authority.

This research objective was to design the ginger candy compression machine and determine the efficiency and capacity for saving time and labor in pressing ginger candy for community enterprise groups Pim Malaherb Chiang Rai Province. Ginger candy compression machine consists of the main structure namely the extruder and power transmission systems. The machine was designed with two horsepower motors or 1.5 kilowatts to drive the shaft and to rotate the screw through the flange. This study installs the inverter to control the motor speed at 1000±10 1200±10 and 1400±10 rpm. The extrusion die had an average diameter of 9.7 millimeters. The results found that the motors speed that was suitable for compression was a Rotational speed of 1400±10 rpm. When the speed increased the efficiency and the working rate increased too. The amount of ginger stirred was used at 300 500 600 900 1000 1500 2000 and 3000 grams. The maximum efficiency was 90.85 percent. The efficiency increased with the amount of ginger stirred. The ginger candy compression machines engineering economic analysis results found that the machines operating cost was 18063.6 baht per year. When considering the machines operation at 792 hours per year the payback period was 6 months and 11 days.