Single-phase systems protection

Protection of a domestic or an industrial single-phase system... 

Protection of a domestic or an industrial single phase system Ground fault on an LT system Ground fault protection in hazardous areas. Ground leakage in an HT system Core-balanced current transformers (CBCTs). Ground fault (G/F) protection schemes... 

Oxidation of cyclic amines. Sheehan and Tulis have examined the oxidation of acylated cychc amines with ruthenium tetroxide in a chlorinated solvent (single-phase system) or with ruthenium dioxide—sodium metaperiodate in CHCI3-H2O (two-phase system). Lactams can be obtained in good yield by oxidation of 1-methyloxalylpiperidine or l-methyloxalylpyrroUdine (1) with RUO4. Tlih, protective group is cleaved with sodium methoxide in methanol. The N-carboethoxy derivative of azetidine (n = 0) is oxidized in low yield... 

The devices are not restricted to single-phase systems. Figure 3.4 illustrates a three-phase RCD connected into the supply from a three-phase distribution board to a motor. In this particular case, the RCD may be set to operate at a leakage current of perhaps 500 mA since it is providing protection... 

A key factor in the design and choice of earth continuity conductors, e.g. cable armouring, bonding straps, and fault current protective devices is the earth loop impedance . This is especially the case for solidly earthed low voltage systems, whether they be three-phase, single-phase or even direct current systems. 

This is another vital part of an impressed current system. The T/R must be rugged and reliable with minimal maintenance requirements. It should be easy to maintain with good instruction manuals, circuit diagrams for maintenance and easy access to fuses and other consumable and replaceable components. Compared with pipeline or marine CP applications (steel piles, etc.) the power demand is modest. Most steel in concrete needs less than 10 mA-m to provide protection, usually at less than 10 V. The power for a 100 watt light bulb will protect 10,000 m. This means that a single phase, air cooled T/R will usually protect even the largest structure and power consumption is rarely an economic concern. 

The modem method of choice (manual or automated) is a solid phase system, using phosphoramidite chemistry (Fig. 4). The most advanced automated systems employ P-cyanoethylamidites, rather than me-thylamidites. Cyanoethyl protection avoids the poten-tud hazard of thymine methylation by intemucleotide methyl phosphate, which is present when methylami-dites are used the cyanoethyl group is also more easily removed than methyl, so that deprotection of the phosphate, deprotection of the bases, and release from the solid support can be performed in a single stage. 

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