低壓配電系統(tǒng)的設(shè)計(jì)

1 關(guān)于配電箱：

配電箱是按電氣接線要求將開關(guān)設(shè)備，測量儀表，保護(hù)電氣和輔助設(shè)備組裝在封閉金屬或非金屬箱重，購車低壓配電裝置的設(shè)備。配電箱應(yīng)具有合理的分配電能的作用，且設(shè)計(jì)時(shí)盡量考慮各相負(fù)載均衡，啟停控制對電網(wǎng)影響降低到最小。一般分為照明配電箱，計(jì)量給電箱，動力配電箱。

2 生產(chǎn)執(zhí)行標(biāo)準(zhǔn)：

一般在中國我們按照GB7251標(biāo)準(zhǔn)執(zhí)行，在國際上的其他地區(qū)的項(xiàng)目，應(yīng)遵循招標(biāo)方技術(shù)規(guī)格要求執(zhí)行。

GB7251.1 2013 低壓成套開關(guān)設(shè)備和控制設(shè)備 第1部分總則

GB7251.12 2013低壓成套開關(guān)設(shè)備和控制設(shè)備 第2部分：成套電力開關(guān)和控制設(shè)備

GB7251.3 2017低壓成套開關(guān)設(shè)備和控制設(shè)備  第3部分由一般人員操作的配電盤

在國際上，我們一般按照IEC61439標(biāo)準(zhǔn)執(zhí)行，滿足歐標(biāo)標(biāo)準(zhǔn)。有時(shí)候客戶項(xiàng)目要求也會按British Standard標(biāo)準(zhǔn)執(zhí)行，BS標(biāo)準(zhǔn)的開關(guān)標(biāo)準(zhǔn)覆蓋了很多方面，包括電路斷路器、跳閘器、動力繼電器、氣體絕緣開關(guān)、手動控制開關(guān)、車用電子產(chǎn)品、繼電器等。深入了解這些標(biāo)準(zhǔn)對于市場參與者（例如制造商和設(shè)計(jì)院）和最終用戶的安全至關(guān)重要。

BS開關(guān)標(biāo)準(zhǔn)的實(shí)施旨在保證產(chǎn)品的質(zhì)量和性能，以確保在使用開關(guān)設(shè)備時(shí)不會出現(xiàn)危險(xiǎn)和故障。在制定標(biāo)準(zhǔn)的過程中，會對開關(guān)產(chǎn)品的性能、壽命、外部環(huán)境的影響、使用者的安全需求、電壓和頻率等多種因素進(jìn)行綜合考慮。

BS開關(guān)標(biāo)準(zhǔn)在很長一段時(shí)間內(nèi)一直被視為世界上比較權(quán)&威性和可靠的標(biāo)準(zhǔn)之一。人們普遍認(rèn)為采用符合BS標(biāo)準(zhǔn)的開關(guān)將為消費(fèi)者提供更安全、可靠和長久使用的保障。

3 電參數(shù)及使用環(huán)境的要求：

   不同國家及地區(qū)，變電站出來的電壓不僅相同，所以在設(shè)計(jì)開始時(shí)，應(yīng)與客戶確認(rèn)電壓，防護(hù)等級，室內(nèi)或是室外使用，以及是否屬于海邊，或者是海上使用。同時(shí)，我們還應(yīng)考慮現(xiàn)場的溫差，及濕度，海拔等影響。溫度/濕度早晚比較大的情況時(shí)，箱內(nèi)需要加裝加熱器除濕，必要時(shí)還需要加裝性能可靠的呼吸閥。現(xiàn)場的復(fù)雜環(huán)境均會影響元件的選型及配電箱結(jié)構(gòu)的設(shè)計(jì)。此外還應(yīng)考慮配電箱的安裝方式，及柜門的打開方向，配電箱殼體的材質(zhì)要求等等。

4 配電箱的防護(hù)等級：

IP防護(hù)等級（Ingress Protection））系統(tǒng)是由IEC（International Electrotechnical Commission）所起草，將電器依其防塵防濕氣之特性加以分級。IP防護(hù)等級是由兩個(gè)數(shù)字所組成，第1個(gè)數(shù)字表示電器防塵、防止外物侵入的等級(這里所指的外物含工具，人的手指等均不可接觸到電器之內(nèi)帶電部分，以免觸電)，第2個(gè)數(shù)字表示電器防濕氣、防水浸入的密閉程度，數(shù)字越大表示其防護(hù)等級越高。防護(hù)等級應(yīng)遵照IEC60529標(biāo)準(zhǔn)執(zhí)行。

IP后首數(shù)字 代表防塵等級

IP后第二位數(shù)字代表 防水等級

5 內(nèi)部元件的選擇

    元件的選擇如熱繼電器的選擇，需要根據(jù)脫扣電流及復(fù)雜還選擇。此外，不用國家的不同標(biāo)準(zhǔn)，還應(yīng)注意導(dǎo)線的顏色，及耐壓等級，是否有要求導(dǎo)線為低壓無鹵阻燃等等。涉及到低溫區(qū)域環(huán)境，如-60攝氏度的極低環(huán)境溫度，還應(yīng)考慮低溫特性進(jìn)行設(shè)計(jì)。

7 人機(jī)交互性的設(shè)計(jì)

    現(xiàn)代設(shè)計(jì)理念要求考慮人機(jī)交互性，如配電箱安裝的高度，箱內(nèi)或箱外的照明燈具，各回路開關(guān)標(biāo)簽及運(yùn)行指示燈的位置，顏色，必要時(shí)急停開關(guān)的設(shè)置及醒目的標(biāo)識說明等等，都應(yīng)考慮在內(nèi)。

Design of low voltage distribution system

1 About distribution box：

Distribution box is a device that assembles switchgear, measuring instruments, protective electrical and auxiliary equipment in closed metal or non-metal boxes according to electrical wiring requirements and purchases low-voltage distribution devices. The distribution box should have the function of distributing power reasonably, and the load balance of each phase should be considered as far as possible in the design, and the impact of start-stop control on the grid should be minimized. Generally divided into lighting distribution box, metering power box, power distribution box.

2 Production execution standard：

Generally, in China, accordance with GB7251 standard, and in other areas of the international project, we should follow the technical specifications of the  tenderer.

GB7251.1 2013 Low voltage switchgear and control equipment - Part 1 General

Low voltage switchgear and control equipment - Part 2: Switchgear and control equipment

GB7251.3 2017 Low voltage switchgear and control equipment - Part 3 Switchboards operated by general personnel

Internationally, we generally comply with IEC61439 standards to meet European standards. Sometimes customer project requirements will be implemented according to British Standard standards, BS standard switching standards cover many aspects, including circuit breakers, trip, power relays, gas insulated switches, manual control switches, automotive electronics, relays and so on. An in-depth understanding of these standards is essential for the safety of market participants (such as manufacturers and design institutes) and end users.

The implementation of BS switching standards aims to guarantee the quality and performance of products to ensure that there are no hazards and failures when using switchgear. In the process of developing the standard, many factors such as the performance of the switch product, life, the impact of the external environment, the safety needs of the user, voltage and frequency are comprehensively considered.

The BS switch standard has been regarded as one of the most authoritative and reliable standards in the world

for a long time. It is widely believed that the use of BS standard switches will provide consumers with more safety,

reliability and long-term protection.

3 Electrical parameters and operating environment requirements：

Different countries and regions, the voltage out of the substation is not only the same, so at the beginning of the design, we should confirm with the customer the voltage, protection level, indoor or outdoor use, and whether it belongs to the sea, or is used at sea. At the same time, we should also consider the on-site temperature difference, humidity, altitude and other effects. When the temperature/humidity is relatively large in the morning and evening, the box needs to be equipped with a heater dehumidification, and if necessary, it also needs to be equipped with a reliable breathing valve. The complex environment of the site will affect the selection of components and the design of distribution box structure. In addition, the installation method of the distribution box, the opening direction of the cabinet door, the material requirements of the distribution box shell and so on should be considered.

4 Protection level of distribution box：

The IP Protection (Ingress Protection) system was drafted by the International Electrotechnical Commission (IEC) to classify electrical appliances according to their dust and moisture resistance. IP protection level is composed of two numbers, the first number indicates the electrical dust, to prevent the level of foreign object intrusion (here refers to the foreign objects including tools, human fingers, etc. are not exposed to the electrical appliances within the live part, so as to avoid electric shock), the second number indicates the degree of electrical moisture, waterproof immersion, the greater the number indicates the higher the level of protection. The protection level shall comply with the IEC60529 standard.

The first digit after IP indicates the dust protection level

The second digit after IP indicates the waterproof rating

5 Selection of internal components

    The selection of components, such as the selection of thermal relays, needs to be selected according to the trip current and complexity. In addition, without the different standards of the country, we should also pay attention to the color of the wire, and the pressure level, whether the wire is required to be low-pressure halogen-free flame retardant and so on. When it comes to low-temperature regional environments, such as extremely low ambient temperatures of -60 degrees Celsius, the low-temperature characteristics should also be considered in the design.

7 Design of man-machine interaction

    Modern design concepts require consideration of human-machine interaction, such as the height of the distribution box installation, the lighting inside or outside the box, the location of the circuit switch label and running indicator light, color, if necessary, the setting of the emergency stop switch and eye-catching identification instructions, etc., should be taken into account.