China
Africa
Explore chapters and articles related to this topic
Logistical Considerations for Work Involving Confined Spaces
Published in Neil McManus, Safety and Health in Confined Spaces, 2018
A device for ensuring electrical safety is the ground fault circuit interruptor (GFCI or GFI) (Figure 9.7). A GFCI is a circuit breaker that detects overloads and shorts as do regular breakers, but also detects a ground fault (Bernstein 1991). A ground fault is a flow of current through an unintended path from the “live” wire to ground. The GFCI measures imbalance between current flowing into the circuit and current flowing out. The breaker opens the circuit when leakage is occurring. In this case, current is flowing to ground. Leakage can occur through damp or worn insulation, defective wiring, or cutting of the cord. The rapid opening of the breaker decreases the shock hazard. The GFCI will not protect against contacting the “live” wire and the neutral wire (short circuit) or two “live” wires. Protection is offered against contact with a “live” wire and a ground path. GFCIs monitor leakage in the range 4 to 6 mA. Testers are available for determining performance of GFCIs and to verify the amount of leakage.
5 Grounding and Bonding
Published in C. Sankaran, Power Quality, 2017
In Chapter 1, a ground loop was defined as a potentially detrimental loop formed when two or more points in an electrical system that are normally at ground potential are connected by a conducting path such that either or both points are not at the same potential. Let’s examine the circuit shown in Figure 5.12. Here, the ground plane is at different potentials for the two devices that share the ground circuit. This sets up circulation of currents in the loop formed between the two devices by the common ground wires and the signal ground conductor. Such an occurrence can result in performance degradation or damage to devices within the loop. Ground loops are the result of faulty or improper facility wiring practices that cause stray currents to flow in the ground path, creating a voltage differential between two points in the ground system. They may also be due to a high-resistance or high-impedance connection between a device and the ground plane. Because the signal common or ground conductor is a low-impedance connection, it only takes a low-level ground loop potential to cause significant current to flow in the loop. By adhering to sound ground and bonding practices, as discussed throughout this chapter, ground loop potentials can be minimized or eliminated.
Overhead Lines
Published in Martinez-Velasco Juan A., Power System Transients, 2017
Juan A. Martinez-Velasco, Abner I. Ramirez, Marisol Dávila
High voltages can be generated on grounded parts of a power line support when either a ground wire or a phase conductor is struck by lightning. If lightning strikes a tower or a ground wire, the discharge should be then safely led to the earth and dissipated there. The purpose of grounding for protection against lightning is to bypass the energy of the lightning discharge safely to the ground; that is, most of the energy of the lightning discharge should be dissipated into the ground without raising the voltage of the protected system. The tower grounding impedance depends on the area of the tower steel (or grounding conductor) in contact with the earth, and on the resistivity of the earth. The latter is not constant, fluctuates over time, and is a function of soil type, moisture content, temperature, current magnitude, and waveshape.
A Review of the EMI Effect on Natural Convection Heatsinks
Published in IETE Journal of Research, 2023
Abdullah Genc, Habib Dogan, Ibrahim Bahadır Basyigit, Selcuk Helhel
Grounding, filtering and shielding are well-known EMC methods to suppress RE at inter-system and at PCB level. Eliminating and/or limiting EMI problems at its origin can be possible at PCB design level including heatsink selection. Grounding is used to prevent undesirable EMI currents from occurring by a low resistance path formed between the electrical devices and the ground. The common-mode currents and grounding in the heatsink are studied [28, 29] that grounding to a feedback circuit on the PCB provides safety against high voltage variations. Proper grounding methods allow to obtain about 12 dB reduction in RE. The grounding connections to the PCB with λ/2 or λ/4 ranges decrease the coupling or shifting the resonance frequency as shielding. In this case, if the harmonic values are shifted to a frequency region without the harmonics of the device, a dramatic reduction of the EMI values will occur. Moreover, the Faraday cage forms between the PCB and the heatsink as the grounding at lower ranges such as λ/10 or λ/20. This cage shields the Integrated Circuit (IC) and reduces the EMI from the IC [30].