Protective multiple earthing

Cable sheath. Additional overhead line conductor Protective multiple earthing fP.M.E.) Buried Strip/rod/plate Earth-leakage circuit breaker, Voltage-operated Earth-leakage circuit breaker, Current-operated... 

Here Ze is the impedance of the supply side of the earth fault loop. Tfie actual value will depend upon many factors the type of supply, the ground conditions, the distance from the transformer, etc. The value can be obtained from the area electricity companies, but typical values are 0.35for TN-C-S (protective multiple earthing, PME) supplies and 0.8n forTN-S (cable sheath earth) supplies. Also in the above formula, R is the resistance of the line conductor and R2 is the resistance of the earth conductor. The complete earth fault loop path is shown in Fig. 3.32. 

Figure 3.35 Protective multiple earthing supply (TN-C-S system) showing earthing and bonding...

This type of underground supply is becoming increasingly popular to supply new installations in the United Kingdom. It is more commonly referred to as protective multiple earthing (PME). The supply cable uses a combined... 

Regulations 4 to 8 refer to the continuity of the supply neutral conductor, general requirements for connection with earth, multiple earthing of the neutral, protective multiple earthing (PME) supplies on consumers premises, and metalwork earthing. The main duties are to ... 

Where a combined neutral and earth conductor is used to supply a consumer s premises, the supplier must meet the protective multiple earthing requirements of Regulation 7, as well as ensure that the consumer s installation meets the criteria set out in the same Regulation for equipotential bonding and earthing. The neutral conduetor of PME supplies must not be connected through to metalwork in caravans or boats (refer to Part 6 of BS 7671 and Chapter 10 of this book for clarification). 

The TN-C-S type of distribution is called PME (protective multiple earthing) of the neutral because the neutral serves as a combined neutral and protective conductor (PEN) and is earthed at the transformer and at several other locations between the transformer and consumer. The underground service is... 

The ozone layer around the Earth has provided us all a natural ring of protection from harmful UV radiation. However, multiple anthropogenic activities have acted as barriers and often caused damage to this shield. Less protection from UV light will, over time, lead to increased health problems and crop damage. Major health problems linked to overexposure to UV radiation by the depletion of ozone include skin cancer (melanoma and nonmelanoma), premature aging of the skin and other skin problems, cataracts and other eye damage, and suppression of normal immune system function.29... 

Storage and Security Each stockpile is stored in a chemical exclusion area at each installation. Most of the stockpile is kept on pallets, in boxes, in cans, or is stored individually in igloos specifically designed for ammunition and explosives. The igloos have lightning protection systems and steel doors, and they are covered with earth. They are equipped with multiple locking systems. 

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