The branch current method is a network analysis technique in which branch current directions are assigned arbitrarily, and then Ohm's law and Kirchhoff's current and voltage laws are applied systematically to solve for the unknown currents and voltages. Selective short-circuit protection can be achieved in different ways, such as: Time-graded protection Time- and current-graded protection A straightforward way of obtaining selective protection is to use time grading. For the sake of convention, I'll denote any current entering the node as positive in. In the United States, the National Electric Code (NEC) exists to guide electricians in the proper installation of electrical equipment and defines the specific requirements for circuit protection. 5 The focus of the NEC, which is a code that is developed by the National Fire Protection Association. IEEE/IAS/I&CPSD Protection & Coordination WG Chair Jacobs Canada, Calgary, AB rasheek. com IEEE Southern Alberta Section PES/IAS Joint Chapter Technical Seminar - November 2016 Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 2 Abstract: Protective relays and devices. Alternating Current (AC – an electric current that periodically reverses direction) is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans, and electric.