Earth connections

Erd-. earth, earthy, terrestrial, mineral, ground, soil. geo-, -ableitung, /, (Elec.) earth connection, ground, -achse, /. axis of the earth, erdacht, p.a. devised, invented. 

An electrical earth system comprises the provision on the supply system of an earth connection to facilitate earth fault current flow, the connecting of all exposed metalwork within the installation to a common grounding terminal and the connection of this terminal to earth. For a complete installation the principal factors which need to be considered, are ... 

The connection to earth can be made utilizing earth rods, earth plates, earth lattices or grids, or buried strip conductors. Selection depends on the locality and type of ground conditions at the site. The effectiveness of the earth connection is, in turn, dependent on the resistivity of the soil at the site, the type of soil and climatic conditions have a direct effect upon the resistance of the connection made. Typical values of resistivity — m) for different types of soil are ... 

Apply b above clean flow cell Replace lamp if using an unsuitable eluent component of absorbance at detection wavelength, change eluent Fix or change earth connection... 

In the early 60s, we were Earth-bound, but not Earth-connected. We were shackled to the illusion of the Earth as nothing but a dirtball, and of ourselves as tiny ants crawling on its surface jostling with each other for domination. LSD broke us out of that mode. Acid is a sky-energy psychedelic it rips you from your conceptual moorings and allows you to float or fly and get a bird s-eye view of the things you ve been attached or committed to. 

In some ways this new generation is awesomely wise at an age when we were just beginning to explore, they already know what they want and what they need. It s what we all need in order to save the planet to bond with the Earth. So developing their Earth-connection through the medium of the mushroom—the Earth s sacred, time-honored offering to the human brain— makes much more sense to them than sky-flying with LSD. 

Earthing connections, including any supplementary earthing bonding connections are satisfactory (for example connections are tight and conductors are of sufficient cross-section)... 

Earth connections maintain the integrity of the type of protection X X X... 

FIG. 102. PDr.ctaiy ir.ixe by Biazzi (Courtesy BtuzziS.A., Vcvey, Switzerland). Earth connection of the bow.1 can be seen. 

Looking at Figure 9-1, L stands for Live (or Line or Phase ), N for Neutral, and E is the Safety Ground or simply, earth. EUT stands for Equipment Under Test. Note that the earth is shown represented by the IEC symbol for Protective Earth (ground with a circle around it) and is occasionally labeled PE in literature. The DM noise generator is across the L and N pair. It tries to push/pull a current Idm through these two wires. No current flows through the earth connection on account of this noise source. 

To know what the measured voltages Vl and Vn are, we now look at Figure 9-3. The voltage due to the common mode component is 25 2 multiplied by the current flowing in the earth connection (i.e. 50 Q times the current in each leg). The voltage due to the differential mode component is 100 2 times the differential mode current. Therefore the LISN provides the following load impedances to the noise generators (in the absence of any input filter)... 

To qualify the preceding sbghfly — connechng the metal enclosure of the equipment to earth can sometimes be considered as an acceptable level of safety protechon — there are exceptions to this, as we will soon learn. However, assuming for now that earthing is acceptable, we know that to protect the user in case the earth connection fails (maybe due to something as simple as a loose contact), we need to provide one more level of protection. So this could simply be the 4 mm of separahon. 

For minimizing noise in general, we must actually ensure that all the grounding (earthing) connections — from the PCB to the enclosure, and on to the earth wire, are good. Any intervening PCB traces should also be wide, and of low inductance. 

We ask — is it really a good idea to place a small inductor (e.g. a bead or small toroid with a few turns) somewhere in the earth connection Suppose we place it on the wire connecting the ac inlet to the enclosure (or PCB to inlet). This is then called a ground choke or earth choke. It is commonly found on low-power evaluation boards (from vendors promoting their clever IC solutions), but rarely seen on a commercial power supply. 

Whether earthing connections and neutral busbars need to be isolated during maintenance, e.g. as may be required when two transformers feed a common switchboard. 

Having fonnd K and Ki it is now possible to find the mesh voltage Em as follows. The resistance Rep is substitnted into the fanlt cnrrent eqnations (H.1.1) and (H.1.2), to give the total fault current If. The earth retnm circnit between the pole at point A in Fignre 13.12 and the earthing connection at point B at the sonrce is a parallel circnit of the resistances to earth en and Rgp and the overhead earth retnm line impedance Zgoh- The parallel combination is -... 

All the lightning conductors should be periodically tested, to see that they are in working condition, at least every three months, according to Mr Richard Anderson. The object of the test is to determine the resistance of the earth-connection, and to localise any defective joints or parts in the conductors. The best system of testing the conductors is to balance the resistance of each of the earths against the remainder of the system, from... 

Figure 1. Schematic of the Sun-Earth Connection. The thin lines signify magnetic field lines.

CAUTION. High leakage current Earth connection essential before connecting supply, (for stationary equipment)... 

Storage precautions for storing the containers at the user end are to be given. Some of the precautions to be avoided are direct sunlight, exposure to rains, dusty conditions, proximity to hot surfaces, provision of earth connection to container (having aluminium powder, inflammable matter), and need to install smoke detectors and water sprinklers in the storage sheds. 

Avoid use of sharp knives and crow bars for opening the drums unless permitted by the supplier. There are chances of fire or explosions if metallic chisels and steel hammers are used. Use only non-sparking type devices (wooden mallets) with proper earth connection to each container (especially for Aluminium Powder). 

For site welding earth connection shall not be taken from pipelines or process tanks. Separate lead cable shall be used. 

Earth connections for electrical installations as well as process units, storage tanks, pipelines, and gas lines handling inflammable materials shall be as per instmetions/standard practice. 

Any instructions from electrical inspector/SEB for installing the new transformer (especially when capacity of the process plant will be increased)—earth connections and separate earth pits for the transformer body and incoming neutral. 

Starters, push button stations, flameproof fittings, motors, and earth connections as per applicable safety standards. Approval shall be taken from electrical inspecting authorities before commissioning. 

Continuity tests for earth connections provided on process vessels (carrying explosive, inflammable, or toxic materials). 

Electrical earth connections, short-circuit protections, etc. 

Figure 10.35 shows the most important parts of an electromedical device. The power line and earth connection are shown to the right. The signal connections to the outside world... 

This is the type of supply more often found when the installation is fed from overhead cables. The supply authorities do not provide an earth terminal and the installation s circuit protective conductors (CPCs) must be connected to earth via an earth electrode provided by the consumer. lET Regulation 542.2.3 lists the type of earth rod, earth plate or earth tapes recognized by BS 7671. An effective earth connection is sometimes difficult to obtain and in most cases a residual current device (RCD) is provided when this type of supply is used. The arrangement is shown in Fig. 3.36. 

Fix a temporary link between the line and earth connections on the consumer s side of the main switch. 

Test between the centre pin of any Edison screw lamp holders and any convenient earth connection. 

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