A summary of the common problems in the design of

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Summary of common problems in the design of water industry substation and distribution station

introduction: Aiming at some problems found by the author in the review of the design of 10 and 6kV substation and 10 and 6/0.4kv substation for many years, this paper makes a brief analysis according to the current national codes and standards, and puts forward specific improvement suggestions

keyword: problems in substation and distribution substation specification

there will be many problems in the design of 10, 6 kV distribution substation and 10, 6/0.4kv substation. It is a very common and very important work in engineering construction. Its standardization and technicality are very strong, and many aspects involve the implementation of national mandatory provisions. To do a good job in the design of substation and distribution station, we should not only implement the current relevant national specifications and regulations, but also meet the specific requirements of the local power supply department, otherwise various problems will occur, affecting the design quality and project progress. In order to do a good job in the design of the substation and distribution station, I now sort out some of the problems I found when reviewing the design drawings of the substation and distribution station of our institute, make a brief analysis, and communicate with you for common improvement

1. The names of substations and power distribution stations should be accurate and not arbitrary when using terminology in engineering design. The name "substation and distribution substation" should not be used in general in the design documents of specific projects. "Substation and distribution substation" is a general term of substation and distribution substation, which is only used for general reference. When it comes to a certain category or an individual, it should be called "substation" or "distribution substation" respectively. In gb50053-94 code for design of 10kV and below substation, "substation" is interpreted as "10kV and below AC power supply supplies power to electrical equipment after being transformed by power transformer"; The explanation of "power distribution substation" is "there is only switching and power distribution in the substation, and we are back!" There is no main transformer on the busbar of the high-voltage power distribution device that can function ". Sometimes, in both substation and distribution devices, those whose main function is to increase and decrease voltage, including high and medium voltage distribution devices, are called "substation". Those whose main function is medium voltage distribution, including 3 ~ 10/0.4kv transformers, are called "substation". When a project has multiple substations, each substation shall be named with the name of the building or serial number

2. The type of live conductor system and the type of system grounding according to Article 312 of iec-tc64, the type of distribution system has two characteristics, namely, the type of live conductor system, such as three-phase four wire system, and the type of system grounding, such as TN-C-S system. TN-S system of three-phase four wire system shall not be called "three-phase five wire system" in official documents. It has been clearly pointed out in the "explanation of terms" on page 37 of gb50054-95 code for design of low voltage power distribution, "three-phase four wire system is one of the types of live conductor distribution system, three-phase refers to L1, L2, L3 three-phase, four wire refers to three phase wires and one n wire passing through normal working current, excluding PE wire not passing through normal working current". It further clarifies that "TN-C, TN-C-S, TN-S, TT and other grounded distribution systems belong to three-phase four wire system". In China, 220v/380v should be used for low-voltage distribution voltage. The type of live conductor system should adopt single-phase two-wire system, two-phase three wire system, three-phase three wire system and three-phase four wire system. In the design documents, the definition of TN-S and TN-C-S grounding types is sometimes confused. The grounding type of the system is generally in terms of the power supply range of a substation or a transformer. When the neutral line N line and the protective line PE line are separated only in a local range, such as a building or a floor, it should be called TN-C-S system. When the exposed conductor of the electrical device on the load side of a residual current protector in TN system is grounded separately, it can be called local TT system

3. Classification terms and various classification, classification and other terms in the design documents of standard units of measurement shall be unified with national standards and industrial standards and shall not be confused. For example, the term often used: power load should be called class I, II and III load, where "class" is used instead of "class"; Lightning protection buildings are called class I, II and III lightning protection buildings, where "class" is used instead of "class". The new lightning protection specification is no longer divided into industrial and civil, and the grid size of roof lightning protection should also be subject to the new specification; The hazardous area of explosive gas environment is divided into zones 0, 1 and 2, the hazardous area of explosive dust environment is divided into zones 10 and 11, and the hazardous area of fire is divided into zones 21, 22 and 23. Here, "zone" is used instead of "class" or "class"; However, the dangerous places of gunpowder, explosives, ammunition and initiating explosive devices are electrically divided into class I, II and III dangerous places, where "class" is used instead of "area". Other terms and expressions should also be used correctly, such as "circuit breaker" and "substation" should be used in official documents, rather than "automatic opening of parts and accessories", "substation", etc., which are not listed one by one. The standard symbols of measurement units should be correct, and the case of letters should not be arbitrary. For example, a, V, W, kV, kW, KVA, kvar, LX, km, etc. shall all use legal units of measurement, and special attention shall be paid to the correct case of unit symbol letters. All unit symbols converted from human names, such as a, V, W, N, PA, and prefix symbols above megabytes, such as m, G, shall be written in large letters; In addition, they are all lowercase, such as kV, MW, kvar, km, etc. For information about units of measurement, please refer to pages 773 ~ 783 in Chapter 16 of the "industrial and civil power distribution design manual"

4. The requirements for civil engineering clearly stipulate the selection of substation site and the requirements for relevant disciplines such as architecture in gb50053-94 code for design of 10kV and below substations. We still have many specific problems in the implementation. Now we only list the following examples for brief analysis, which should be paid attention to in the future design

1) fire cornice: when the oil immersed power transformer is selected for the substation attached to the workshop, some do not set fire cornices above the door of the transformer room. In article 6.1.8 of the mandatory provisions of the engineering construction standard gb50053-94, it is stipulated that "when electrical equipment with combustible oil is arranged on the bottom floor of multi-storey and high-rise main buildings, a fire cornice with a width of not less than 1.0 and a real-time graphic dynamic switching of m shall be set above the opening of the outer wall on the bottom floor"

2) emergency exit: some designs only set one exit or two exits in the distribution room with a length of more than 7m, but close to the same end. This does not comply with the provisions of article 6.2.6 of gb50053-94. The specification requires that "the distribution room with a length greater than 7m should be provided with two exits, which should be arranged at both ends of the distribution room"

3) beam height: some designs do not take into account the indoor clear height

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