Design and implementation of POTT protection scheme using IEC-61850

This study is an attempt to implement the International Electrotechnical Commission (IEC) - 61850 to protect a transmission line using Generic Object Oriented Substation Events (GOOSE) messaging. IEC 61850 describe rules for integration of protection, control, measurement and monitoring functions within a power system network at the process and station control levels. Earlier envisioned for substation automation, IEC 61850 has shown its potential in eliminating substation wiring, enhanced interoperability between vendors and systems. Thus efforts are now being made to expand it to cover substation to control center and substation to substation automation. In this paper, GE D90 Plus Line Distance Protection relays were used to protect an assumed transmission line scheme through Permissive Overreach Transfer Trip (POTT) communication scheme. Different types of faults were calculated for different locations and tested. GOOSE messages carrying trip signals were transmitted by the relays. The relays operated in the expected tripping zone and picking up right elements thus validating the results. The time delay between tripping the relays at each end of transmission line was found to be ranging between 3 microsecond to 2.9 millisecond

Food receipts analyses: examining food choices and shopping practices of newly arrived refugee families in the U.S.

The main objectives of this study were (a) to examine food shopping, choices, and budgeting practices among the two major recently arrived refugee groups, those of Burmese and Iraqi origin, and (b) to compare pre-resettlement living conditions and access to food between these same two groups. The study was approved by the IRB of the University of North Carolina at Greensboro. A case-study approach was used to carry out an in-depth investigation of food choices and shopping practices of eight newly arrived refugee families. Of the eight families, four were Iraqi refugees, while four were originally from Burma. Participating families were interviewed to collect socio-demographic and related information on pre-resettlement living conditions. Additionally, food receipts were collected from each family for one and a half to two months to determine which foods were purchased, the percentage of the food budget coming from Supplemental Nutrition Assistance Program (SNAP) benefits, and the types of stores visited. The receipt data were analyzed using descriptive frequencies. Results indicated that refugees of Burmese origin spent on average 19 years living in rural refugee camps, while the Iraqi refugee families lived in urban centers in neighboring countries prior to resettlement for an average of four and a half years. The SNAP benefits represented the majority of the food budget for most families. Refugee families from Burma on average spent more of their food budget at ethnic stores compared to Iraqi families. Purchase of dairy foods and plant proteins was rare among participants from Burma while animal protein accounted for 30 percent of their food budget. Iraqis spent 18 percent of their food budget on foods from the solid fats and added sugar category. In conclusion, nutrition education interventions with refugees should be tailored to families taking into account their pre-resettlement living situations and prior food access