Cable termination: not just crimp and forget 

This is what everyone thinks they know, but in reality it’s a complete mess. Cable termination is not about taking any tip or crimper and pressing it all the way. It’s rather about understanding what exactly you’re working with: core cross-section, material, flexibility class, type of insulation. I often see how people take NShVI aluminum lugs onto a copper stranded conductor because “they seem to fit the diameter?”, and then they wonder why the contact gets hot. Or they forget about removing the internal insulation frompower cablesbefore installing the end funnels - a trifle, but leads to breakdown. I myself went through this at the beginning, until I got better at it and began to delve into the details that are written in fine print in catalogs.

The main thing is to start with the right choice

There are no options here. If the tip does not match the cable, all subsequent work is in vain. I always pay attention not only to the section, but also to the shape. For example, to connect to some imported devices of an input distribution device, you need tips with a special bend angle of the petal or a specific bolt hole size. A standard NSHVI may not physically stand up.

I once worked with supplies for a contractor who was installing a switchboard at a new facility. We brought them a batch of KG 4x25 cable, and ordered ordinary tinned copper lugs for crimping. But the cable itself had conductors of the fifth class of flexibility. In theory, it’s possible. In practice, in order to efficiently crimp such a multi-wire wire, you need either special crimper dies for thin wires, or tips with internal filling paste, which prevents oxidation and ensures better contact. Without this, there is a risk that individual wires will not be clamped and over time the contact area will decrease. As a result, we re-ordered NShVI tips with quartz-vaseline paste.

By the way, about supplies. Now there are a lot of things on the market, but the quality is very low. Previously, they often bought from local resellers, but then they switched to working directly with manufacturers. For example, we cooperate withShijiazhuang Hist Electric Co.,Ltd— they have been making cable fittings since 2004. This is not an advertisement, but a statement: when you have a stable supplier who understands what GOST and TU are, and does not just churn out hardware, life becomes easier. Their website -histe-ru.com— I used to use it as a guide to standard sizes when I needed to quickly clarify the parameters of some end effector for SIP.

The tool is half the battle

You can have the perfect tip and the perfect cable, but kill the whole thing with a crimper for three pennies. I have several hydraulic presses in my arsenal: one for sections up to 120 mm2, the other for large ones, up to 240 mm2. And this is not luxury. If you press a tip of 95 mm2 with a tool designed for a maximum of 50 mm2, underpressure is guaranteed. And pinching is also bad; you can crush the core or deform the tip itself.

Particularly critical withaluminum cables. Aluminum is a soft, fluid material. If you press it too hard, the contact will loosen after a while under load due to the creep of the metal. If you don't put enough pressure on it, it will heat up due to the high contact resistance. Here you need a calibrated instrument with a pressure gauge or indicator that the desired pressure has been achieved. Manual hydraulic ratchet crimpers are our choice for most field jobs.

I remember an incident during the installation of a boiler room. There were powerful pumps there, powered by an AVVG 3x70 aluminum cable. Six months after launch at one of the phases incable lugThe insulation began to melt. We took it apart and there was an oxide film inside the tip and the contact was blackened. The reason is that during installation the core was not properly cleaned and contact paste was not used. I had to redo everything, cutting off part of the cable. Since then, I have a rule for aluminum: cleaning the metal with a brush until it shines + mandatory treatment with a DAC-type paste or at least quartz-vaseline paste. And no “this will do.”

An Often Overlooked Technology

It would seem so complicated: cleaned, inserted, crimped. But there are nuances. For example, the direction of crimping. For tubular lugs, crimping always goes from the shank (from the cable entry point) to the petal. If you do the opposite, there is a risk of extruding the tip material and worsening the contact in the area where the bolted connection will later be.

Another point is crimp quality control. The easiest way is to try to forcefully pull the tip away from the cable after crimping. If done correctly, it will not move. A more advanced method is to use a crimp height gauge or a press with an indicator. But in the field, they most often rely on experience and the markings on the crimper dies. By the way, I always do two or three crimps on one tip, shifting by a few millimeters, especially on large sections. This ensures a large contact area and reliability.

When working with different projects, sometimes you are faced with a customer’s requirement to use a specific brand of fittings. This is not a whim. For example, some applications where corrosion resistance is important require tinned copper or even nickel plated ferrules. In the catalog of the sameShijiazhuang Hist Electric Co.,LtdYou can find different coating options, which is convenient. You just know that you are not taking a piece of hardware, but a product with certain properties for a specific environment - high humidity, chemical vapors, or just for the street.

Not just power lines

Termination is not only about 380 volt power supply. The same thing, in fact, happens with control cables and low-current lines. Only there are different tips - sleeve, ring, fork. And the errors there are no less critical. A poorly crimped terminal on a stranded wire in the control cabinet can lead to loss of the sensor signal, and then you will spend hours looking for an open circuit in the circuit.

Accuracy is important here. Stripping the insulation exactly to the length of the tip sleeve so that no bare copper remains. Correct selection by diameter: if the sleeve is large, the wire will dangle; if it is small, it will not fit or the veins will be damaged. For thin stranded wires, I sometimes use double crimp lugs: first the core is crimped, then an insulating sleeve for mechanical fixation. Helps a lot against vibration.

Once I had to redo an entire control panel precisely because of vibration. The tips on the control wires were crimped, but without fixing the insulation. After six months of operation of the pumping station, due to constant shaking, some wires simply came out of their tips. The system started to glitch. After that, on all critical low-current objects I use only lugs with an insulating sleeve or, at worst, I put heat shrink with an adhesive layer on the crimp area.

About heat shrinkage and insulation

This is a topic for a separate conversation, but without it the story aboutcable terminationwill be incomplete. After the tip is crimped, the connection must be insulated and protected. Previously, they were often wrapped with PVC electrical tape. Cheap, but unreliable. Over time, the glue flows and the tape unwinds, especially in warm panels.

Now the standard is heat-shrinkable tubing. Ideal if with an adhesive layer. Heated it with a construction hairdryer - the tube tightly pressed the joint, and the melted glue sealed all the cracks. This protects against moisture, dust and accidental touch. Mandatory for outdoor connections or in wet areas. It’s just important not to overheat, otherwise you can damage the insulation of the cable itself.

For the powerfulpower connectionsSometimes they use ready-made kits: a tip already filled with contact paste and heat shrink of a certain length. Convenient, fast, minimum defects. I have seen such solutions from different manufacturers, including in the assortment that suppliesShijiazhuang Hist Electric Co.,Ltd. For a large-scale project where it is necessary to ensure a uniform standard and speed of installation, this is a good option. Although for minor repairs on the farm, you often take everything separately.

Bottom line: there are no trifles

So it turns out that a seemingly simple operation becomes overgrown with a bunch of rules and “buts”. From the choice of tip and tool to the final insulation, you can mess up at every stage, and the consequences will not appear immediately, but months later, when the object has already been handed over and everything is working. Experience comes precisely through such mistakes, your own or others’.

Now, looking at any cable that needs to be terminated, I automatically evaluate: material, cross-section, operating conditions. Then I select the fittings, check the condition of the core, think about the paste and protection. This is no longer a conscious analysis, but a habit. And the main conclusion that can be drawn: in this matter you cannot skimp on trifles. The best tip and the right tool will pay off handsomely, eliminating unscheduled repairs and downtime. And a reliable connection is ultimately security. And these are not pompous words, but the daily practice of anyone who is seriously involved in electrical installation.

Therefore, when I again see someone trying to crimp a cable with pliers or using the first tip they come across, I always stop them. Because I know how this could end. And because I once learned from my mistakes, now I try to prevent others from repeating them. The whole pointending- attention to detail, which determines the reliability of the entire system.