Protection electrical systems

Independence Protective systems should be sufficiently independent of the control system or other protective systems (electrical/electronic or programmable). Where there is an interface, then the method of achieving independence should be defined, and common cause failures adequately considered. 

A Russian ammonia pipeline of nearly 2400 km extends from Togliatti on the Volga River to the Port of Odessa on the Black Sea, and a 2200-km, 250-mm dia branch line extends from Godovka in the Ukraine to Panioutino. The pipeline is constmcted of electric-resistance welded steel pipe with 7.9-mm thick walls but uses seamless pipe with 12.7-mm thick walls for river crossings. The pipeline is primed and taped with two layers of polyethylene tape and suppHed with a cathodic protection system for the entire pipeline. Mainline operating pressure is 8.15 MPa (1182 psi) and branch-line operating pressure is 9.7 MPa (1406 psi) (11). 

The low cost, light weight, and exceUent electrical conductivity of graphite anodes have made this impressed current protection system valuable for cathodic protection of pipelines, storage vessels, process equipment, and also for weU casings both on- and offshore. 

Protection from electric shocks (grounding system)... 

The Guidelines for Process Equipment Reliability Data with Data Tables covers a variety of components used in the chemical process industry, including electrical equipment, analyzers, instrumentation and controls, detectors, heat exchangers, piping systems, rotating equipment (pump, compressor, and fan), valves, and fire protection systems. 

Figure 20-9 shows the negative effect of uninsulated heating elements on corrosion protection. In a 250-liter tank, an electric tube heating element with a 0.05-m surface area was screwed into the upper third without electrical separation, and in the lower third a tinned copper tube heat exchanger with a 0.61 -m surface area was built in. The Cu heat exchanger was short-circuited for measurements, as required. For cathodic protection, a potential-controlled protection system with impressed current anodes was installed between the two heating elements. The measurements were carried out with two different samples of water with different conductivities. 

The processes of cathodic protection can be scientifically explained far more concisely than many other protective systems. Corrosion of metals in aqueous solutions or in the soil is principally an electrolytic process controlled by an electric tension, i.e., the potential of a metal in an electrolytic solution. According to the laws of electrochemistry, the reaction tendency and the rate of reaction will decrease with reducing potential. Although these relationships have been known for more than a century and although cathodic protection has been practiced in isolated cases for a long time, it required an extended period for its technical application on a wider scale. This may have been because cathodic protection used to appear curious and strange, and the electrical engineering requirements hindered its practical application. The practice of cathodic protection is indeed more complex than its theoretical base. 

External events are accident initiators that do not fit well into the central PSA structure used for "internal events." Some "external events" such as fire due to ignition of electrical wires, or flood from a ruptured service water pipe occur inside the plant. Others, such as earthquakes and tornados, occur outside of the plant. Either may cause failures in a plant like internal events. External initiators may cause multiple failures of independent equipment thereby preventing action of presumably redundant protection systems. For example, severe offsite flooding may fli 1 the pump room and disable cooling systems. An earthquake may impede evacuation of the nearby populace. These multiple effects must be considered in the analysis of the effects of external events. 

Taxonomy No. 4 2 4 2 Equipment Description PROTECTION SYSTEMS-FIRE-FIRE WATER PUMPS-ELECTRIC ... 

Grounding. Grounding is another way to provide protection from electric shock however, it is nonnally a secondary protective measure. By grounding a tool or electrical system, a low-resistance patlr to tire earth Uirough a ground coimection or comiections is intentionally created. Wlien properly done, tliis patli offers sufficiently low resistance and lias sufficient current-cariy ing capacity to prevent the buildup of voltages that may result... 

See also-. Climatic Effects Consumption Domestic Energy Use Electric Motor Systems Electric Power, Generation of Electric Power, System Protection, Control, and Monitoring of Electric Power Substations Electric Power Transmission and Distribution Systems Government and the Energy Marketplace Regulation and Rates for Electricity. 

This chapter introduces the basic items of design and specification for the principal systems and components of an electrical industrial installation. Electrical supply systems are discussed with regard to interface with the supply authorities and the characteristics. Salient features of switchgear, transformers, protection systems, power factor correction, motor control equipment and standby supplies are identified and discussed together with reference to the relevant codes of practice and standards. The equipment and systems described are appropriate to industrial plant installations operating at typically 11 kV with supply capacities of around 20MVA. 

The analysis and understanding of the operation of protection systems and the application of protective devices to power systems is wide ranging and complex. This section considers only the objectives of protection systems, discrimination and its importance to protection, and describes the most common types of relay used in industrial power systems. Many publications covering the subject of protection systems are available (e.g. Power System Protection, edited by the Electricity Council). 

Where facilities are exposed to the constant radiation of the sun, sun shades are provided over exterior exposed equipment that may not function properly at elevated temperatures or would deteriorate rapidly if left continual exposed to the direct sunlight. Most electrical or electronic equipment is rated for a maximum operating temperature of 40 °C (104 °F) unless otherwise specified, e.g., hazardous area lighting temperatures are normally specified for 40 °C (104 °F) limit. Of particular concern for fire protection systems are those containing storage for foam concentrates rubber hoses or other rubber components which may dry and crack. 

Flammable gas detection systems are typically used to initiate an alarm at a concentration level below the lower flammable limit (LFL). Two gas alarm levels (low and high) are often utilized to allow early warning prior to taking automatic actions. Detection systems may also be used to stop electrical power and initiate process shutdown. The low alarm setpoint should be —20% LFL and the high alarm level set point should be between 40%-60% LFL. Where these devices are used to initiate process shutdown or activate fire protection systems, it is common practice to use some form of voting, typically 2 out of 2, such that the frequency of spurious shutdowns or system activation is minimized. 

Sprinkler protection should be provided as for any storage facility handling similar material products. In storage areas that are always above freezing, preaction type systems electrically activated by a separate fire/heat detection system are often used. 

Active fire protection—A fire protection system or device that requires moving parts, detectors, instruments, electrical or other power or utilities. 

The catalyst preparation area is protected by an automatic water-spray sprinkler system that is actuated by associated heat detectors. Fixed fire water monitors surround this process area. The water for these fire protection systems is supplied through 8-inch underground water mains by three (two diesel and one electric) horizontal, centrifugal, 2500... 

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