© ERICO ®, Inc NFPA 70 National Electric Code (NEC) Grounding & Bonding.

Presentación del tema: "© ERICO ®, Inc NFPA 70 National Electric Code (NEC) Grounding & Bonding."— Transcripción de la presentación:

1 © ERICO ®, Inc. 1998 NFPA 70 National Electric Code (NEC) Grounding & Bonding

2 © ERICO ®, Inc. 1998 EQUIPMENT GROUNDING Proposito:  Proporsionar seguridad al personal Manera:  Interconnecting all non-current carrying metal components and will eliminate potential differences among the metal components.  Connecting the equipment grounding conductor system to Earth will eliminate potential differences between metal components and Earth.  Components: raceways, boxes, cabinets, frames, cable armor, building steel, etc...

3 © ERICO ®, Inc. 1998 SYSTEM GROUNDING Purpose:  Provide equipment protection by operating overcurrent devices to clear fault current and providing a potential reference. Means:  An intentional connection to equipment ground from one of the current carrying conductors of an electrical distribution system.

4 © ERICO ®, Inc. 1998 TYPES of SYSTEM GROUNDING Ungrounded Solidly or Effectively Grounded Resistance Grounded Reactance Grounded

5 © ERICO ®, Inc. 1998 AC Systems Required to be Grounded NEC 250-5 AC circuits < 50 volts  Where supplied by transformers if the transformer supply exceeds 150 volts to ground.  Where supplied by transformers if the transformer supply system is ungrounded.  Where installed as overhead conductors outside of building. AC Systems of 50 to 1 kV Supplying Premises Wiring  Where max voltage to ground is 150 volts or less.  Where a 3Ø, 4W Wye-connected system supplies L-N load.  Where a 3Ø, 4W Delta-connected system supplies L-N load.  Where a grounded service conductor is un-insulated. AC Systems of 1KV & Over (See 250-5(c)) Separately Derived Systems (See 250-5(d))

6 © ERICO ®, Inc. 1998 Effective Grounding Path NEC 250-51 The path to ground from circuits, equipment, and metal enclosures for conductors shall (1) be permanent and electrically continuous, (2) have capacity to conduct safely any fault current likely to be imposed on it, and (3) have sufficiently low impedance to limit voltage to ground and to facilitate the operation of the circuit protective devices. The Earth shall not be used as the sole equipment grounding conductor.

7 © ERICO ®, Inc. 1998 Grounding Electrode System (H) NEC 250 - 81 & - 83 Formed by bonding all of the following: Metal underground water pipe (soil contact at least 10’) Building steel Concrete encased electrode (Ufer Ground) Ground ring Made and other electrodes  Local underground systems or structures  Rod & Pipe electrodes  Plates electrodes

8 © ERICO ®, Inc. 1998 NEC 250 - 81 & - 91(a) Splicing of the Ground Electrode Conductor  Listed irreversible compression type connectors  Exothermic Welding Process NEC 250-84: Resistance of Made Electrodes  Single Electrode R = 25 ohms or less R > 25 ohm, a second electrode is installed  Electrodes at least 6 feet apart

9 © ERICO ®, Inc. 1998 Grounding Conductor Connections (K) NEC 250 250-113: To Conductors and Equipment: Grounding conductors and bonding jumpers shall be connected by EXOTHERMIC WELDING, listed pressure connectors, listed clamps, or other listed means. 250-115: Connections to Electrodes: The grounding conductor shall be connected to the grounding electrode by EXOTHERMIC WELDING, listed lugs, listed pressure connectors, listed clamps, or other listed means.

10 © ERICO ®, Inc. 1998 Equipment Grounding Personnel Safety

11 © ERICO ®, Inc. 1998 System Grounding Equipment Protection

12 © ERICO ®, Inc. 1998 System Grounding Solid Neutral Grounding

13 © ERICO ®, Inc. 1998 System Grounding Resistance Grounded

14 © ERICO ®, Inc. 1998 Earth as Equipment Grounding Electrode UNACCEPTABLE / CODE VIOLATION