170 电气柜绝缘隔板与母线槽件
绝缘隔板的工况是电场加湿热
配电柜内部的绝缘隔板长期承受电场、柜内温升（40-70℃）、南方梅雨季的高湿。
失效形式不是击穿，是电痕化——表面受潮后产生漏电电流，碳化形成导电通道，最终沿面闪络。这个过程的起点是表面吸潮。
CTI 是第一指标不是阻燃
绝缘隔板必须同时满足阻燃和耐电痕化，但很多人只查阻燃。
CTI（相比漏电起痕指数）要 ≥ 400 V，高压柜要 ≥ 600 V。
溴系阻燃体系的 CTI 普遍只有 250 V，必须选无卤阻燃或专用高 CTI 牌号。这是电气柜件选料最容易踩的坑。
现场还原：母线槽里的爬电痕迹
2024 年 12 月，温州一家做母线槽的电气厂打电话来，语气急：他们的母线槽在某商业综合体的配电间做了半年，年检打开一看，绝缘支撑件表面有碳化爬电痕迹，供电局要求限期整改。
到现场看件：爬电痕迹从固定螺栓沿表面走了一条焦黑的细线。配电间湿度大，尘积加上凝露，绝缘件表面形成导电水膜，CTI 不够的料就这样一路碳化过去。
那批绝缘件用的是普通阻燃 PA66，V-0 是过的，但 CTI 只有 275 V。设计院图纸上写的是污染等级 3 环境，对应 CTI 要 400 以上——供应商送样时附的检测报告是干净条件下的，设计院审图时没人对这一项。
我们给的是高 CTI 阻燃 PA66 专用牌：CTI 600 V，无卤体系，湿热后 CTI 衰减小。更换了全部支撑件，复检过关。
这单做下来最深的感受是：电气件的阻燃报告人人会附，CTI 报告很多人不知道要附——而配电间这种湿热加尘积的环境，杀器恰恰是后者。
PBT 与 PA66 的取舍
PBT 吸湿率 0.1%，介电性能几乎不随湿度变化，是绝缘隔板的优选。PA66 吸湿率 2.5-3%，饱和吸湿后介电强度下降 25%，但强度和耐热更好，用于有机械强度要求的结构隔板。潮湿地区的柜内隔板优先 PBT。
湿热电痕化测试是必检项
IEC 60112 的 CTI 测试是筛选材料，真正贴近实际的是 IEC 60587 的斜面法耐电痕化测试。
在 3.5 kV 和污液条件下，要求 6 h 不击穿。PBT 和专用高 CTI PA66 能通过，普通阻燃 PA66 通不过。
这一项不做，柜子在南方就是定时炸弹。
深一层：CTI 是怎么被「做」上去的
CTI（相比漏电起痕指数）这个指标，配方层面是可以主动设计的，值得把机理和配方两条线都讲清楚。
机理上：爬电是表面放电碳化的过程。湿热环境下表面形成水膜，粉尘溶进去变成电解质，带电表面沿水膜放电，放电把有机物碳化，碳化导电，导电又加速放电——正循环，一路烧成导电通道。
CTI 值就是材料抗这条路的耐力，档位从 100 V 到 600 V。
配方上，提 CTI 的主力是水合金属氧化物：氢氧化铝、氢氧化镁。它们有两手，受热分解放水吸热降温，放电时表面不形成尖锐碳化通道——这也是它们同时当阻燃剂用的原因。
反过来，有些阻燃体系伤 CTI：含卤体系燃烧时产生酸性气体，遇水成酸，表面电解质增强，CTI 反而被拖下去。
所以「高 CTI 加高阻燃」这两个要求碰在一起，配方选择面其实很窄，无卤氮系加水合氧化物是主流路径，能同时把两个指标做上去的牌号，市面上并没有那么多。
还有一个工程事实：CTI 会随湿热老化衰减，出厂 600 的料，湿热 1000 小时后可能落到 500。设计和验收都要按衰减后的值留余量，认证报告上那一行干态数据，不是终点。
母线槽绝缘件的特殊要求
母线槽的绝缘支撑件要承受短路时的巨大电动力冲击——峰值可达额定值的几十倍。
机械强度和阻燃同等重要。走 PA66-GF30 无卤阻燃高 CTI，热变形温度要 240℃ 以上。
母线槽件还要做短路耐受验证，这是塑料件里少见的力学 + 电气双重认证。
安装配合的隐性变量
隔板要和柜体、母线、支撑件配合，尺寸公差 ±0.5 mm。PA66 吸湿后尺寸变化 0.3-0.4%，1 m 长的隔板会涨 3-4 mm，足以导致安装困难或产生内应力。
长尺寸隔板优先 PBT 或对 PA66 做尺寸预留。另外隔板上的安装孔要做倒角，避免应力集中开裂。
工程实测：4 条强制测试
测试1：CTI 对比。无卤阻燃 PBT CTI 600 V，无卤阻燃 PA66 CTI 500 V，溴系阻燃 PA66 仅 250 V。
测试2：斜面法耐电痕化。3.5 kV 6 h，高 CTI PBT 通过，普通阻燃 PA66 在 2 h 击穿——必检项。
测试3：吸湿介电。PA66 饱和吸湿介电强度降 25%，PBT 几乎不变——潮湿地区优先 PBT。
测试4：短路电动力。母线槽支撑件在 50 kA 短路下 PA66-GF30 无破损，未增强 PA66 断裂。
追问三连：采购最常问的三件事
一问：绝缘隔板多厚合适。 厚度不是越大越好：隔板厚一倍，爬电距离是上去了，但散热差、成本高、占用柜内空间。正确顺序是先按回路电压和污染等级算要求爬电距离，再按材料 CTI 查修正系数，最后定厚度——厚度是算出来的，不是拍出来的。
二问：湿热后 CTI 衰减多少要复测。 行业惯例是湿热 1000 小时后复测，衰减超过一档（比如 600 落到 400 以下）就不能按标称值设计。母线槽、户外柜这类凝露环境，这一项必须做，跳过去的迟早还账。
三问：母线槽绝缘件的温升怎么算。 绝缘件自身不发热，问题是导体发热传导过来：铜排满载时接触部位能到 100℃ 以上，绝缘件长期使用温度要按这个校核，PA66 改性牌 RTI 至少 120℃，低了这个数，十年蠕变松弛能把压紧力放掉，接触电阻上涨，恶性循环从这里开始。### 算一笔材料账：CTI 档位的价格梯度
高 CTI 牌号的价格随档位陡升，把梯度摆出来，选型时心里有数。
CTI 400 档的阻燃 PA66，比常规 V-0 牌贵 10% 上下——这是最常用的档位，量最大。CTI 600 档，贵 30% 到 40%，配方里水合氧化物的占比翻倍，产能也少。
更高的 4.5 kV 斜面等级，按项目定制，价格一单一议。
梯度陡的原因是配方冲突：阻燃和 CTI 对填料的要求互相牵制，能同时做高的体系天然稀缺，稀缺就有溢价。
选型上常犯的错是「档次拉满求安心」：清洁环境的室内柜体用 600 档，每只件多花三块钱，一万只多花三万——而现场的污染等级根本用不上这个档。反过来更常见：重污秽区用 400 档省那三块钱，年检爬电一查，整改的钱百倍奉还。
正确的姿势是把现场污染等级实测或评估清楚，CTI 按「衰减后仍高于要求一档」取值。电力件在这件事上多花的每一块钱都有明确指向，花错方向的每一块钱也都记得住账。### 边界声明
| 工况 | 推荐材料 |
|---|
| 通用柜内隔板 | 高 CTI PBT 阻燃 V-0 |
| 高强度结构隔板 | PA66-GF30 高 CTI |
| 高压柜 | CTI ≥ 600 V 专用料 |
| 母线槽支撑 | PA66-GF30 无卤阻燃 |
| 南方潮湿地区 | 优先 PBT |
工程备忘
绝缘隔板量产前必须做 CTI + 斜面法耐电痕化 + 吸湿介电三项。阻燃不等于绝缘合格，CTI 和耐电痕化才是关键。
实战案例：常见踩坑与正解
踩坑一：只看阻燃等级不看 CTI。绝缘隔板装在带电回路附近，阻燃 V-0 但 CTI 只有 250 V，长期爬电后表面碳化短路。正解：带电件必须 CTI ≥ 400 V（相比漏电起痕指数），V-0 只解决起火，不解决爬电——这是电气件最常被漏掉的一条。踩坑二：用回收料或副牌料做绝缘件，介电强度批次波动大，耐压测试 5% 击穿。正解：绝缘件一律走正牌新料，批次附耐压报告。踩坑三：端子件装完一段时间扭矩衰减，以为是螺丝松了，实际是尼龙蠕变。正解：绝缘隔板承载螺纹连接时必须玻纤增强到 GF25 以上，并在装配 24 h 后复拧一次。
反向案例：从 275 到 600，中间隔着一个年检
回头看温州那单的完整时间线，比单看结论更有用。
2023 年 6 月，项目配电设备中标，绝缘件按「阻燃 V-0」这个唯一硬指标选了普通阻燃 PA66，单价最省。9 月安装送电，一切正常。2024 年 6 月年检，打开柜门发现爬电碳化痕，供电局出整改通知，限定一个月。
一个月里要做的：重新选料（高 CTI 牌）、按真实污染等级补全套验证、采购注塑、现场逐台更换、复检销案。实际用了二十六天，中间工厂派了三班人驻场。材料差价一只几十块，停业整改的商誉损失和驻场人力，是差价的上百倍。
更值得记的是后续：这家厂把绝缘件选料规则改成了三条——先定污染等级、CTI 按衰减后取值、阻燃和 CTI 同表校核。他们说这个规则就来自那个二十六天。
电气行业的事故大多不是技术空白，是「指标没对齐」：设计院的图纸、供应商的报告、现场的工况，三方各说各话，出事的那条缝就在中间。### 延伸判断：验证顺序不要搞反
绝缘隔板的验证有固定顺序，跳过前面的直接做后面的，等于白做。
第一步验证材料本身：力学、热学、阻燃、电气这几项，确认料号没选错。
第二步验证工艺窗口：同一批料在不同模温、不同保压下打出来的件，性能差异可能超过 20%，工艺窗口要跑出来。
第三步才做整机或整件验证：装到实际工况里跑寿命。很多人的顺序是反的——直接装机跑寿命，不合格了不知道是料的问题还是工艺的问题，于是反复换料，半年出不了结果。
把这三件事写成一张表发给供应商，比打十通电话有用——绝缘隔板的选型沟通成本，基本都花在这几项反复确认上。
最后一组问答：三个纠结时刻的裁决
纠结一：图纸上只写了阻燃等级，CTI 要不要主动提。 必须提：图纸没写不等于要求不存在，污染等级对应的 CTI 是行业常识。主动提这一项，工程师会感激——把隐患在设计阶段暴露，是供应商能提供的最大价值之一。
纠结二：绝缘隔板要不要做过剩设计（加厚加档）。 做到「要求一档余量」即可：污染等级加湿热衰减都算进去后，再高一档是合理储备，再高就是浪费柜内空间和成本。过剩设计在电气件上不是美德，是成本失控的体面说法。
纠结三：母线槽件和普通柜体件要不要分开供料。 分开：母线槽的温升和短路工况比普通柜体狠一档，料档和验证都相应加严。合并供货省的是采购流程，赌的是母线槽的温升寿命——电气行业的合并，多数在这笔账上吃亏。### 补记：三个现场判断信号
信号一：表面焦黑细线、沿固定路径走。 爬电碳化，立即停用，这不是老化警告是事故进行时，整批同牌号件都要复检。
信号二：柜内凝露痕加尘积重。 污染等级要按现场实际重估，CTI 余量按重估结果补，别信机房图纸上的理想环境。
信号三：绝缘件压紧力下降、异响。 高温蠕变在走，先测柜内真实温度，再核材料的 RTI，补压紧结构只是临时手段。### 验证顺序：三步走完再下单
第一步，评环境：按现场污染等级和凝露史定 CTI 要求，图纸没写的自己去现场看。
第二步，验衰减：湿热后 CTI 复测，按衰减后取值设计，干态标称值只做参考。
第三步，对系统：绝缘件和导体发热区的温度耦合、和密封结构的配合老化，一起过一遍。三步走完，电气柜里的绝缘件可以放心装十年。
结语
这个件用什么料——选料这件事，越早问越省事。
这类件的选料与试模，可以一起聊。
170 Electrical Cabinet Insulation Panel and Busway Components
The operating condition of the insulation baffle is electric field with humidity and heat
The insulating partitions inside the distribution cabinet are subjected to the electric field, the temperature rise inside the cabinet (40-70℃), and the high humidity of the plum rain season in southern China for a long time.
The failure mode is not breakdown, but tracking—after the surface becomes damp, leakage current occurs, carbonizing and forming a conductive path, eventually leading to surface flashover. The starting point of this process is moisture absorption on the surface.
CTI is the primary indicator, not flame retardancy
Insulating partitions must meet both flame retardant and electrical tracking resistance requirements, but many people only check for flame retardancy.
CTI (Comparative Tracking Index) should be ≥ 400 V, and high-voltage cabinets should be ≥ 600 V.
The CTI of brominated flame retardant systems is generally only 250 V, so halogen-free flame retardants or specially designed high-CTI grades must be selected. This is the easiest trap to fall into when choosing materials for electrical cabinets.
On-site restoration: tracking marks in the busway
In December 2024, an electrical factory in Wenzhou that makes busways called, in an urgent tone: their busways had been installed in the distribution room of a commercial complex for half a year. During the annual inspection, it was found that the surface of the insulation supports had carbonized tracking marks, and the power supply bureau required rectification within a time limit.
On-site inspection: The tracking marks ran along the surface from the fixing bolts in a blackened thin line. The distribution room has high humidity, and with dust accumulation plus condensation, a conductive water film forms on the surface of the insulation components, causing materials with insufficient CTI to carbonize along the way.
That batch of insulating parts used regular flame-retardant PA66. It passed V-0, but the CTI is only 275 V. The design institute's drawings specified a pollution level 3 environment, which corresponds to a CTI requirement of over 400—the inspection report provided by the supplier when submitting samples was under clean conditions, and no one checked this item during the design institute's review.
We provided a high CTI flame-retardant PA66 special grade: CTI 600 V, halogen-free system, with minimal CTI degradation after humidity and heat. All support components have been replaced and re-inspected successfully.
The deepest impression from completing this job is: everyone knows to attach flame retardant reports for electrical components, but many people don't know to include CTI reports — and in power distribution rooms with an environment of humidity, heat, and dust accumulation, the critical danger is precisely the latter.
The choice between PBT and PA66
PBT has a moisture absorption rate of 0.1%, and its dielectric properties hardly change with humidity, making it the preferred material for insulation panels. PA66 has a moisture absorption rate of 2.5-3%, and its dielectric strength decreases by 25% after reaching saturation, but it has better strength and heat resistance, making it suitable for structural panels that require mechanical strength. In humid areas, cabinet panels prioritize PBT.
Damp-heat electrical tracking test is a mandatory inspection item
The CTI test of IEC 60112 is for screening materials, while the sloping method tracking test of IEC 60587 is closer to actual conditions.
Under 3.5 kV and contaminated liquid conditions, it is required not to break down for 6 hours. PBT and specialized high CTI PA66 can pass, while ordinary flame-retardant PA66 cannot.
If this is not done, the cabinet in the south will be a ticking time bomb.
Deeper: How CTI was 'implemented'
CTI (Comparative Tracking Index) is an indicator that can be proactively designed at the formulation level, and it is worthwhile to clearly explain both the mechanism and the formulation aspects.
Mechanistically: tracking is the process of surface discharge carbonization. In a humid and hot environment, a water film forms on the surface, and dust dissolves into it to become an electrolyte. The charged surface discharges along the water film, and the discharge carbonizes the organic matter. The carbonization becomes conductive, which further accelerates the discharge—a positive feedback loop, eventually burning a conductive path all the way through.
The CTI value is the material's resistance along this path, with levels ranging from 100 V to 600 V.
In terms of formulation, the main components that enhance CTI are hydrated metal oxides: aluminum hydroxide and magnesium hydroxide. They have two functions: they decompose when heated to release water and absorb heat to lower the temperature, and during discharge, their surfaces do not form sharp carbonized channels—which is also the reason they are used as flame retardants at the same time.
Conversely, some flame-retardant systems damage CTI: halogen-containing systems produce acidic gases when burning, which form acids when they encounter water, increasing surface electrolytes and actually dragging down the CTI.
So when the two requirements of 'high CTI and high flame retardancy' come together, the range of formulation options is actually quite narrow. Halogen-free nitrogen-based compounds with hydrated oxides are the mainstream path, and there aren't that many grades on the market that can meet both indicators at the same time.
There is another engineering fact: CTI will degrade with humidity and heat aging. Material with a factory value of 600 may drop to 500 after 1000 hours of humidity and heat exposure. Both design and acceptance should allow a margin based on the degraded value; the dry-state data line on the certification report is not the endpoint.
Special requirements for busway insulation components
The insulating supports of the busduct must withstand the huge electrodynamic shocks during short circuits — the peak can reach tens of times the rated value.
Mechanical strength and flame retardancy are equally important. Use PA66-GF30 halogen-free flame retardant with high CTI, and the heat deflection temperature should be above 240℃.
Busway components also need to undergo short-circuit withstand verification, which is a rare dual certification of mechanical and electrical properties for plastic parts.
Install matching latent variables
The partition must coordinate with the cabinet body, busbar, and support components, with a dimensional tolerance of ±0.5 mm. PA66 changes dimension by 0.3-0.4% after absorbing moisture; a 1 m long partition will expand by 3-4 mm, which is enough to cause installation difficulties or generate internal stress.
Long-size partitions preferably use PBT or allow dimensional allowances for PA66. In addition, the installation holes on the partitions should be chamfered to avoid stress concentration cracking.
Engineering field measurement: 4 mandatory tests
Test 1: CTI comparison. Halogen-free flame-retardant PBT CTI 600 V, halogen-free flame-retardant PA66 CTI 500 V, brominated flame-retardant PA66 only 250 V.
Test 2: Inclined plane method for tracking resistance. 3.5 kV for 6 hours, high CTI PBT passed, ordinary flame-retardant PA66 broke down in 2 hours — mandatory inspection item.
Test 3: Moisture absorption dielectric. The dielectric strength of PA66 drops by 25% after moisture saturation, while PBT remains almost unchanged — PBT is preferred in humid areas.
Test 4: Short-circuit electrodynamics. The busway support remained undamaged under a 50 kA short circuit when made of PA66-GF30, while non-reinforced PA66 broke.
Three Consecutive Follow-up Questions: The Three Most Common Questions in Procurement
Question: How thick should the insulation barrier be? Thickness is not necessarily better if it’s larger: if the barrier is twice as thick, the creepage distance increases, but heat dissipation worsens, costs rise, and it takes up more space in the cabinet. The correct sequence is to first calculate the required creepage distance according to the circuit voltage and pollution level, then check the correction factor based on the material's CTI, and finally determine the thickness—the thickness is calculated, not arbitrarily chosen.
Second question: After damp heat, how much CTI attenuation requires retesting? The industry practice is to retest after 1000 hours of damp heat. If the attenuation exceeds one grade (for example, dropping from 600 to below 400), it cannot be designed according to the nominal value. For bus ducts and outdoor cabinets in such condensation environments, this test must be done; skipping it will eventually lead to paying the price.
Three questions: How to calculate the temperature rise of busway insulation parts. The insulation itself does not generate heat; the problem is the heat conducted from the conductor: when the copper bar is fully loaded, the contact area can exceed 100°C, and the long-term operating temperature of the insulation must be verified according to this. The RTI for modified PA66 grades is at least 120°C; if it is lower than this, creep relaxation over ten years can release the clamping force, increase contact resistance, and initiate a vicious cycle. ### Let's do a material cost calculation: the price gradient of CTI grades.
The price of high CTI ratings rises sharply with the level. Putting out the gradient gives you a clear idea when selecting a model.
CTI 400 level of flame retardant PA66 is about 10% more expensive than regular V-0 brand — this is the most commonly used tier and the largest quantity. CTI 600 level is 30% to 40% more expensive, with twice the proportion of hydrated oxides in the formula and less capacity.
Higher 4.5 kV inclined plane grade, customized by project, price negotiable .
The steep gradient is due to formulation conflicts: flame retardant and CTI have mutually restrictive filler requirements; systems that can be raised simultaneously are naturally scarce, and scarcity comes with a premium. A common mistake
makes in choosing models is "maxing out the grade for peace of mind": indoor cabinets in clean environments use the 600 range, each costing 3 yuan more; 10,000 units cost 30,000 yuan more—but the on-site contamination level doesn't even need this level. Conversely, more commonly: using the 400 level in heavily polluted areas saves those 3 yuan, but after annual inspection, the cost of remediation is returned a hundredfold.
The correct approach is to measure or assess the on-site pollution level clearly, and set the CTI value as "still one level above the required level after attenuation." Every extra yuan spent on electrical parts is clearly targeted, and every yuan spent in the wrong direction is remembered. ### Boundary Declaration
| Operating Condition | Recommended Materials |
|---|
| General Cabinet Inner Partition | High CTI PBT Flame Retardant V-0 |
| High-Strength Structural Partition | PA66-GF30 High CTI |
| High Voltage Cabinet | CTI ≥ 600 V Special material |
| busbar tray support | PA66-GF30, halogen-free flame retardant |
| southern humid regions | priority PBT |
engineering memo
insulation partition must undergo CTI + inclined surface method anti-electric scarring + moisture-absorbing dielectric before mass production. Flame retardant does not equal passing insulation; CTI and anti-trace resistance are key.
Practical Case: Common pitfalls and correct answers
Pitfall 1: Only look at flame retardant rating, not CTI. Insulating partitions are installed near live circuits, with flame retardant V-0 but CTI only 250 V. After long-term creepage electricity, the surface carbonizes and short-circuits. Correct answer: Live components must have a CTI ≥ 400 V (compared to leakage tracing index); V-0 only solves fire, not creepage—this is the most commonly missed electrical component. Pitfall 2: Using recycled or second-grade material as insulation components, with large fluctuations in dielectric strength batches, 5% breakdown in voltage test. Correct answer: All insulating parts must use genuine new material, with batch voltage resistance reports attached. Pitfall 3: After installing terminal components for a while, torque decays occurs. Thinking the screw is loose, it's actually nylon creep. Correct answer: When connecting insulated partitions with threaded loads, glass fiber must be reinforced to GF25 or above, and retightened after 24 hours of assembly.
Reverse case: From 275 to 600, there is an annual inspection in between.
Looking back at the full timeline of the Wenzhou order is more useful than just looking at the conclusion.
In June 2023, the power distribution equipment project won the bid. For insulation parts, the only hard criterion was "flame-retardant V-0," choosing ordinary flame-retardant PA66, which was the most cost-effective per unit. Installed and powered back in September, everything was normal. During the June 2024 annual inspection, opening the cabinet door revealed signs of electric scrazing carbonization. The power supply bureau issued a rectification notice limiting the inspection to one month.
had to do in one month: re-selecting materials (high CTI brand), completing full verification based on real pollution levels, purchasing injection molding, replacing machines one by one on site, and re-inspecting to close the case. It actually took twenty-six days, with three teams from the intermediate factory stationed on site. The material price difference was several dozen yuan per piece, and the reputation loss and on-site manpower from suspension and rectification cost hundreds of times the price difference.
What's even more worth noting is the follow-up: this factory changed the insulating material selection rules to three rules—first determine the pollution level, then CTI is valued by attenuation, and flame retardant and CTI are checked together with the table. They said this rule comes from those twenty-six days.
Most electrical industry accidents are not technical gaps, but "misalignment of indicators": design institute drawings, supplier reports, and on-site conditions—each side has its own story, and the crack where the problem occurred lies in between. ### Extended judgment: Don't reverse-order the verification sequence
Insulation partition verification has a fixed order; skipping the earlier and doing the later ones is basically wasted.
Step 1: Verify the material itself: mechanics, thermal, flame retardancy, electrical components, and confirm the part number is correct.
Step 2: Verify the process window: For parts produced by the same batch under different mold temperatures and holding pressures, performance differences may exceed 20%. The process window must be established.
The third step is to do whole-machine or whole-piece verification: install it under actual operating conditions to run its lifespan. Many people do the opposite — install the machine directly to test lifespan. If it fails, they don't know if it's due to the material or the process, so they repeatedly replace the material, and after half a year, no results come out.
Write down these three things in a form and send it to the supplier, which is more effective than making ten phone calls—the cost of communication for insulating partition selection is basically spent on these repeated confirmations.
The final Q&A: The ruling at three critical moments
Dilemma one: The drawings only mention flame retardant rating, should you proactively mention the CTI? You must mention it: not specifying the drawings doesn't mean the requirements don't exist; the CTI corresponding to the pollution level is industry common knowledge. If you proactively bring this up, engineers will appreciate it—exposing hidden dangers during the design phase is one of the greatest benefits a supplier can offer.
Dilemma 2: Should insulation partitions be designed with excess (thickening or grading)? Just achieve a "requirement of one level of margin": after accounting for pollution levels, humidification, and heat decay, a higher level is a reasonable reserve; higher is a waste of cabinet space and cost. Excessive design is not a virtue for electrical components; it's a respectable way to say that costs are out of control.
Dilemma 3: Should busbar duct components and ordinary cabinet components be supplied separately? Separation: The temperature rise and short-circuit conditions of busbars are a level stricter than ordinary cabinets, and material control and verification are accordingly tightened. Combined supply saves procurement processes and gambles on the temperature rise lifespan of busbars—most mergers in the electrical industry lose out on this matter. ### Additional Note: Three on-site judgment signals
Signal One: Surface burnt thin lines, follow a fixed path. Creeper carbonization should stop immediately. This is not an aging warning but an accident occurring. The entire batch of parts of the same grade must be re-inspected.
Signal Two: Condensation marks and dust accumulation inside the cabinet. Contamination levels should be re-estimated according to the actual site conditions; CTI margins should be supplemented according to reassessment results. Do not trust the ideal environment shown on the machine room drawings.
Signal 3: Insulation compression force decreases and abnormal noises. High-temperature creep is ongoing; first measure the actual temperature inside the cabinet, then verify the RTI of the material; the compression structure compensation is only a temporary measure. ### Verification sequence: Complete the three steps before placing an order
Step one, assess the environment: set CTI requirements according to the on-site contamination level and condensation history; if the drawings are not specified, go see the site yourself.
Step two, test attenuation: after damp heat, retest CTI, design according to the attenuation value, dry state nominal value only for reference.
Step three, for the system: go through the temperature coupling between the insulating parts and the heating zone of the conductor, and the aging of the sealing structure together. After completing these three steps, the insulation parts in the electrical cabinet can be safely installed for ten years.
Conclusion
What material is used for this part? The earlier you ask about material selection, the easier it is.
For material selection and mold trials for these types of pieces, you can chat together
