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Prof. D. Wilton ECE Dept.

This document provides an overview of grounding in electrical systems, emphasizing its importance for safety and noise reduction. Grounding connects conductors to the physical earth, preventing voltage drops and electric field buildup around equipment. It clarifies the distinction between grounding and reference points, illustrated through examples of voltage relationships in circuits. Key concepts such as the function of grounded neutral wires and Ground Fault Circuit Interrupters (GFCIs) are discussed, highlighting their roles in protecting against electrical faults.

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Prof. D. Wilton ECE Dept.

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  1. ECE 2317 Applied Electricity and Magnetism Prof. D. Wilton ECE Dept. Notes 5 Notes prepared by the EM group, University of Houston.

  2. Grounding Grounding: connecting a conductor to the physical earth • Safety reasons • Noise reasons equipment water pipe

  3. equipment + VAB = 0 - water pipe Grounding (cont.) • Ensures that there is no voltage drop between equipment and ground • Ensures that there is no electric field outside of equipment • Ensures that there is no charge build up on equipment

  4. equipment ground Grounding (cont.) Ground symbol: Note: grounding is NOT is the same thing as a reference point. (However, when a circuit is grounded, the ground is OFTEN chosen as a reference point of zero volts.)

  5. A + 12 [V] 100  - B ground Example reference point (choose 0 [V]) Find: voltage at the ground VG

  6. Grounding (cont.) hot neutral (grounded back at junction box) ground

  7. Grounding (cont.) wall I hot + junction box V - neutral ground The neutral wire is grounded back at the junction box. Note: The voltage of the neutral wire at the device is not the same as ground, because the neutral wire has a resistance.

  8. Ground Protection The metal casing of an electrical device is normally connected to ground. hot neutral ground

  9. GFCI (Ground Fault Circuit Interrupter) Ih Ig = Ih - In hot neutral In GFCI Circuit trips when Ig > 5 [mA]

  10. Double Insulated Tool Ih plastic case hot neutral In The device is surrounded by an insulating plastic case. It does not require a ground.

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