The selected DC power supply should also meet the following requirements: the power supply and voltage should have a certain adjustment range; it should be able to work continuously, and the power failure should not exceed 24h; there is a reliable lightning protection device; it should be installed between the protected pipeline and the grounded anode There is a device to prevent the reverse flow of current; in areas with AC interference, the power supply's anti-AC interference voltage should not be lower than 10V; when using rectifier equipment, a filtering device should be provided.
A comparison of the technical conditions of the alternative power supply is listed. CCITT (International Telegraph, Telephone Advisory Committee) recommends the power supply scheme of the communication system in remote areas without electricity. The power of the power supply is considered in the recommendation, which can be used as a reference for cathodic protection professionals. Alternative power supply technical conditions comparison category structure moving parts fuel requirements pollution noise battery reliability life, solar cells are simple no no need to be about 20TEG simpler no need no need not high 20CCVT complex 1 if no need high 20 wind generators Complexity, no need to be lower, 10 categories, applicable conditions, land occupation, maintenance work, price, economic power, unattended domestic status quo, solar cells, solar energy, abundant, small, simple, expensive, small, commercial, TEG gas pipeline, not simple, slightly expensive, can introduce CCVT gas pipeline The wind turbine can be imported without being simple and expensive. The wind can be richer, more complex and cheaper. It is not available. 4 IR drop in pipeline potential measurement. The measured potential at the time of power contains an IR drop error component, which makes the measured pipeline protection potential value high. Because of the actual polarization value, misjudgment is caused. For this reason, it is necessary to reduce the IR drop component in the measurement as much as possible in the pipeline design. The general method is to install on / off relays on the power supply, and to achieve unified control of the entire line, so that the breakers of all stations on the entire line are stopped and turned on at the same time, and the response error should not be greater than 011s, so that the along the line can be measured during the measurement The power on / off potential.
The on / off time period can be set at 12s on and 3s off. Another method is to use the near-reference method, bury the long-term reference electrode as close to the pipe surface as possible, and make the soil R as small as possible to reduce the IR drop. Sometimes, the auxiliary test piece electric method is also preferable, but the test piece should not be set more, because it is a leakage point, and it consumes part of the cathodic protection current. In this method, only the auxiliary test piece needs to be disconnected, and the instantaneous power-off potential of the test piece can be measured. Its advantage is that it can avoid the problem of power failure across the line. Interference effects Stray current interference effects are common problems encountered in pipeline design. The main sources of interference are DC electrified railways, such as electric locomotives in Fushun and Anshan mining areas, urban trams, and underground railways. Generally, the influence of interference should be based on actual measurement. Before the pipeline is buried, it is impossible to know the degree of interference and the location of the interference anode area. According to the requirements of SY / T0017) 95 standard, the pipeline potential is positively shifted by 20mV, that is, there is interference. It is necessary to take protective measures when the positive offset is 100mV.
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