Leading supplier of cold splice kits in Asia 

Why High Voltage Splicing Requires Cold Shrink Technology

In our practice of working with energy networks of the CIS countries and the Middle East, we have repeatedly encountered a situation where a cable line failure occurred not due to overload, but due to errors at the connection point.High voltage splicingis a critical node of any distribution network. It is here that the concentration of the electric field is maximum, and mechanical loads are most destructive. Traditional insulation methods, such as using duct tape or open flame shrinking, often result in the formation of microvoids. Over time, these voids fill with moisture, causing partial discharges and ultimately failure of the insulation.

Cold shrink kits solve this problem fundamentally. They use pre-stretched silicone rubber which, when the support core is removed, compresses the cable tightly, creating a constant radial pressure. This pressure prevents moisture and air from entering, ensuring a seal that lasts for decades. For engineers responsible for the reliability of 6–35 kV networks, the transition to cold shrinkage means a reduction in accident rates by 40-60% in the first five years of operation. The choice of technology determines not only the service life of the cable, but also the safety of personnel during installation.

Technical advantages of cold-shrinkable couplings over heat shrinking

When choosing a solution forhigh voltage spliceCustomers often ask the question: why is cold shrinkage more expensive, but preferable? The answer lies in the physics of the process and the human factor. Heat-shrinkable materials require heating with a torch. If the installer overheats the material, it loses its elasticity and becomes brittle. If it is not heated enough, it will not provide a tight fit. In conditions of strong wind or rain, typical of open areas in Russia or Kazakhstan, high-quality heating is almost impossible.

Cold-shrinkable couplings do not have this disadvantage. Installation takes 3 times less time and does not depend on weather conditions. The silicone rubber used in our kits remains elastic in the range from -60°C to +200°C. This is critically important for regions with a sharply continental climate. In addition, silicone is highly hydrophobic and UV resistant, which prevents the insulation from aging in open air.

We conducted a comparative analysis of life cycle costs (TCO) for two types of connections. Data shows that despite the higher initial cost of cold couplings, total maintenance and replacement costs over 15 years are 35% lower. Eliminating the need for a fire source also improves safety in sites with high fire safety requirements, such as oil and gas terminals or underground reservoirs.

Key parameters when choosing a splice kit

Incorrect selection of diameter or type of insulation is the most common cause of premature failure. When ordering kits forhigh voltage spliceThree main parameters must be taken into account:

• Operating voltage and insulation class.For 6-10 kV networks, basic insulation is sufficient, but for 35 kV, an enhanced electric field control system is required. An error in the voltage class will lead to an instant breakdown.
• Cable diameter along the outer sheath.Cold shrink tubing has a limited shrink range. If the cable diameter is outside the specified range (for example, less than 80% of the nominal tube diameter), the radial pressure will not be sufficient to seal.
• Cable shield type.There are cables with a copper screen and with aluminum tape. Kits must include appropriate connection sleeves and screen restoration components. The use of universal solutions without adaptation to the type of screen creates areas with high transient resistance.

Shijiazhuang Hist Electric Co., Ltd., based in Shijiazhuang City, Hebei Province, takes these nuances into account during the design stage. The company, founded in 2004, specializes in developing solutions adapted to difficult climatic conditions. Their product line includes cold shrink couplings that are strictly tested in their in-house electrical laboratory, capable of testing up to 1000 kV. This ensures that each batch of products meets the declared characteristics for dielectric strength and mechanical resistance.

Step-by-step installation algorithm: from preparation to commissioning

Even the best quality kit will not save the network if the installation is carried out incorrectly. Below is a proven algorithm that we recommend to our partners. Deviation from these steps is the main cause of warranty claims.

1. Cable preparation and stripping.The cable must be cut strictly perpendicular to the axis. Stripping of the outer shell and screen must be carried out according to the dimensions specified in the manufacturer's instructions.Important:Do not damage the semiconductive layer of the screen. Any scratch on the core insulation must be sanded with a special abrasive tape until completely smooth. Roughness causes local overloads of the electric field.
2. Connector installation.The cable cores are connected using pressed sleeves. After crimping, all sharp edges and burrs must be removed. A restoration screen is installed over the junction. This is a key element for equalizing potential.
3. Applying semiconductive paste and installing tubes.Conductive paste is applied to the connection to eliminate air gaps. The plastic spiral core is then carefully removed from the cold shrink tubing. The tube should fit evenly, starting from the center and moving towards the edges.Common mistake:Removing the core too quickly can cause the tube to become skewed and wrinkled.
4. End sealing and armoring.The ends of the coupling are sealed using mastics and bandage tapes. If the cable has armor, it is necessary to restore the integrity of the armor ground using copper braid or a spring clamp.
5. Final check.Before applying voltage, it is necessary to measure the insulation resistance with a megohmmeter and conduct a DC voltage test. Only after receiving the test report can the cable be put into operation.

The role of laboratory control in ensuring reliability

There are many manufacturers on the market offering cheap analogues. However, the difference in raw material quality only becomes apparent after several years of operation or when carrying out high-voltage tests. Cheap rubber quickly loses its elasticity (“hardens”) in the cold and cracks when vibrating.

The production base of Shijiazhuang Hist Electric LLC is equipped with modern silicone rubber processing workshops and three specialized warehouses. A key element of their quality system is one of the largest electrical engineering laboratories in Northern China. A strict control system is implemented here at all stages - from incoming control of raw materials to acceptance tests of finished products. The presence of 256 specialists, including 7 doctors and candidates of science, allows the company to develop products that meet international IEC and GOST standards.

This approach ensures technological independence and the presence of more than a dozen active patents. For the customer, this means that when purchasing products from a trusted manufacturer, he receives not just an “elastic band”, but an engineering solution verified by tests up to 1000 kV. This reduces the risks of downtime and emergency shutdowns, which cost energy companies millions of rubles.

Logistics and delivery: how to avoid project delays

Delivery times for cable fittings often become a bottleneck in construction schedules. Delays at customs or incorrect paperwork can stop teams from working. Shijiazhuang Hist Electric LLC has a developed logistics infrastructure for container and truck shipment. The company's products are supplied to the CIS countries, Southeast Asia, the Middle East and Africa.

The company is focused on long-term partnership, providing comprehensive technical support - from calculations and selection of solutions to installation consultations. The service philosophy is based on the principles of efficiency and transparency. Each order is accompanied by individual technical support, and warranty obligations are formed based on actual operating conditions. This is especially important for large infrastructure projects where predictability of delivery is important.

Frequently Asked Questions

What is the shelf life of cold-shrink kits?

When stored in the original packaging in a dry place at a temperature between -10°C and +30°C, the shelf life is 5 years. Silicone rubber does not age as quickly as some other polymers, but we recommend using the product within the first 3 years to ensure maximum mechanical properties. Source: Technical documentation of Shijiazhuang Hist Electric Co., Ltd.

Can cold ferrules be used on paper insulated cables?

Yes, it is possible, but special training is required. It is necessary to completely remove moisture from the paper and use locking compounds to prevent oil migration. For such tasks, there are specialized transition couplings. Standard cross-linked polyethylene (XPE) cable kits do not fit directly without adapters.

Does low temperature affect the shrinkage process?

Cold-shrinkable tubes remain flexible down to -60°C. However, in extremely low temperatures (-40°C and below), it is recommended to store the kits in a warm room for 24 hours before installation. This will make it easier to remove the support core and allow for a smoother shrinkage.

Is special equipment required for installation?

No. Cold shrink sleeves do not require gas torches, hair dryers or power supplies to install. You only need a standard set of electrician's tools: a knife, a stripper, crimping wrenches and an abrasive tape. This makes the technology ideal for working in remote areas without access to electricity.

Choosing a reliable supplier forhigh voltage spliceis an investment in the stability of your energy system. Companies such as Shijiazhuang Hist Electric Co., Ltd. combine deep engineering competence with industrial maturity to ensure consistent quality. Their experience in delivering to difficult climatic zones confirms the products’ ability to withstand high mechanical loads and variable temperature conditions.

Don't risk the reliability of your network. Use proven, lab-tested solutions. Contact us today for technical advice and kit pricing for your project.Request a catalog of cold-shrinkable couplings