This specification is revised by the Second Design and Research Institute of the Ministry of Machinery Industry, in conjunction with relevant units, in accordance with the notice requirements of the National Development and Reform Commission's Document No. 250 (1986). During the revision process, the standardization team conducted extensive investigation and research, carefully summarized the experience since the implementation of the standards, absorbed some scientific research achievements, and extensively solicited opinions from relevant units across the country. Finally, the draft was reviewed and finalized by our department in conjunction with relevant departments. The main content of this revision includes: adding particularly important loads and their power supply requirements in the load classification; In the content of ensuring power quality, new measures have been formulated to limit voltage fluctuations and flicker, control the abnormal rate of sinusoidal waveform of power grid voltage caused by harmonics, and reduce the asymmetry of three-phase low-voltage distribution systems; It was also proposed that reverse voltage regulation should be selected for on load voltage regulation of power grids above 35kV, and for some reactive loads, separate on-site compensation should be used, as well as the selection of three-phase distribution transformers in D, yn11 junction groups
Power supply load classification
Power load is divided into first level load, second level load, and third level load based on its requirements for power supply reliability and the losses and impacts caused by accidental interruption of power supply.
(1) First level load
First level load refers to the power load that, after an unexpected power outage accident, will cause personal injury or death, or cause significant economic damage to equipment, major product scrapping, requiring a long period of time to resume production, or causing significant adverse effects in politics.
(2) Second level load
Second level load refers to the power load that, in the event of an unexpected interruption of power supply accident, will cause significant economic losses such as damage to main equipment, scrapping of a large number of products, inability to resume production in the short term, or affect the normal work of important units, or result in social and public order disorder.
(3) Third level load
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