Distribution System Training

The objective of this module is to present and discuss the main features related to distribution system layout, including various means of providing continuity of service and alternative sources of supply.

On conclusion of this module, the participant should be able to understand the following concepts, and apply them in day-to-day work practice.

• The function of the distribution system
• Elements of a simple distribution system
• The source of power supply to the distribution system
• Single, double and multiple in-feeds to the distribution system
• The sub-transmission system (also known as high-voltage distribution)
• Primary feeder layout
• Branch circuits (lateral circuits)
• Typical transmission, sub-transmission, and primary distribution voltage levels
• The functions of transmission, sub-transmission, and primary distribution
• The function of distribution transformers
• Radial operation of primary feeders
• The primary loop with normally open tie
• Classification of customers
• Feed to high voltage customers (at sub-transmission and primary feeder voltages)
• Distribution transformer connections to provide 3-phase supply
• Distribution transformer connections to provide single phase supply
• Single-phase 3-wire supply (with centre tapped neutral)
• Connecting to a secondary main
• The need for continuity of service
• Alternate primary feeds ?”the primary selective system”
• Alternative feeds ?”secondary selective system”
• The secondary spot network with distribution transformers in parallel
• Definition of temporary faults and permanent faults
• Operation of the feeder circuit breaker in response to the reclosing relay for temporary, and permanent faults
• The combination of branch line fuses and the reclosing relay under temporary and permanent fault conditions
• Operation of the mechanical recloser under fault conditions
• Operation of the sectionalizer under fault conditions
• Information required by the operator, i.e. circuit diagrams, protection diagrams, area maps, and wall diagrams