Electrical power systems grounding

Grounding of electrical systems is mandated by the electrical codes that govern the operation of electrical power systems. The National Electrical Code (NEC) in the U.S. is the body that lays out requirements for electrical systems for premises. However, the NEC does not cover installations in ships, railways, or aircraft or underground in mines or electrical installations under the exclusive control of utilities. 

Figure 5.2 shows the essential elements of a grounded electrical power system. It is best to have a clear understanding of the components of a ground system to fully grasp the importance of grounding for safety and power quality. The elements of Figure 5.2 are defined as follows ... 

A maintenance program should document all tests, inspections, and faults cleared by a main and feeder circuit breaker. Lack of such a program will reduce the reliability of the electrical equipment.Molded case circuit breakers require no internal maintenance. They should be inspected for broken casing and loose connections after they operate to clear a fault and should be replaced after they have operated to clear two faults. Feeder circuit breakers, especially older circuit breakers, should be exercised (repeatedly opened and closed) whenever possible.f" Part of the initial commissioning of an electrical power system must include testing of the ground fault protection. ... 

Connect the utility company power-system ground rod to the main facility ground point as required by the local electrical code. Do not consider the building ground system to be a substitute for the utility company ground rod. The utility rod is important for safety reasons and must not be disconnected or moved. Do not remove any existing earth groimd connections to the power-line neutral connection. To do so may violate local electrical code. 

FM Global. Property loss prevention data sheet 5-10, protective grounding for electric power systems and equipment. Norwood, MA FM Global 2003. 

CFR Part 56, Subpart K and Part 57, Subpart K address the use of electricity at surface metal and nonmetal mines and underground metal and nonmetal mines, respectively. These subparts address adequacy of cable conductors, circuit and traiUng cable overload protection, performance of work on electric equipment and electric power circuits, grounding system requirements and testing of grounding systems, handheld electric tools, fuse removal and replacement, protection of trading cables from physical damage, installation of troUey wires and track, isolation of communication circuits from power circuits, and so forth. 

The role of grounding electrodes is to effectively drain fault currents into the soil and thereby mitigate the damage of installations of telecommunication systems and electrical power systems. Thus, the performance of such a system is influenced by the transient characteristics of its grounding electrodes. It is therefore important to study these characteristics. Recently, NEA methods have been successfully applied in analyzing transient responses. 

In addition to the circuit breaker, there have been a number of other SMA appHcations for various functions in electric power generation (qv), distribution, and transmission systems. One such device is a thermal indicator that provides a signal visible from the ground of a hot junction or connector in a distribution yard. Such hot spots occur as a result of the loosening of bus bar connectors owing to cycHc temperature as the electric load varies. In addition to the use of SMA flags as a hot-spot indicators, actuators that automatically maintain the contact force in a bus bar connection have been demonstrated. Based on a BeUeviHe washer fabricated from a Cu—Al—Ni SMA trained to exhibit two-way memory, these washers, when heated by a hot joint, increase their force output and correct the condition. A 30 mm diameter washer 3 mm thick can produce a force of over 4000 N. Similar in purpose... 

From a basic physics standpoint, a circuit is a complete loop. Electric current can flow only if it returns to its source, i.e., completes the circuit. The path tlirough which tlie current returns to its source is called the "retum or ground. The reason for the tenn "ground is tliat the ctirlh is literally used to provide the return patli no matter what distance separates tlie equipment from the power source. Ground comiections can be made to a cold water system as its components provide a reliable, low-resistance patli for contact witli tlie earth. 

Although static discharges are small electrical phenomena, they are significandy different from a high voltage electrical discharge to ground from a power system or... 

Five biomass samples (hazelnut shell, cotton cocoon shell, tea factory waste, olive husk and sprace wood) were pyrolyzed in a laboratory-scale apparatus designed for the purpose of pyrolysis (Demirbas, 2001, 2002a). Figure 6.4 shows the simple experimental setup of pyrolysis. The main element of the experimental device is a vertical cylindrical reactor of stainless steel, 127.0 nun in height, 17.0 nun iimer diameter and 25.0 mm outer diameter inserted vertically into an electrically heated tubular furnace and provided with an electrical heating system power source, with a heating rate of about 5 K/s. The biomass samples ground... 

It was reported that in-channel amperometric detection was possible without using a decoupler. This has been achieved using an electrically isolated (non-grounded, floating) potentiostat [750]. On the other hand, when the CE power supply was battery operated (12-V battery to power 3-kV HV module) and therefore it was electrically isolated from the electrochemical detection system [765], In another report, a portable HV power supply (using 6 V battery for the HV module and 9 V battery for the electrochemical detection circuit) was constructed for CE-EC detection on a glass chip [751],... 

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