MV Cable Termination vs. Splicing: Differences and Applications
In medium-voltage distribution systems, selecting the right cable is only part of the job. For an underground power grid or industrial installation to operate reliably, you need the right accessories at every junction and endpoint.
Two components form the backbone of these systems: MV cable terminations and MV cable splices. While both belong to the medium-voltage accessory family, they serve entirely different purposes. Procurement teams and junior engineers frequently confuse the two or treat them as interchangeable items on a bill of materials. Making the wrong choice leads to improper insulation, electrical failure, and costly system downtime.
Understanding the core functional differences between terminations and splices—and knowing how to select the right one for your layout—helps keep your installation running smoothly over the long haul.
What Is the Difference Between MV Cable Termination and MV Cable Splicing?
The fundamental distinction lies in where the component sits and what it connects. A termination prepares a cable to meet a piece of equipment, whereas a splice bonds two separate lengths of cable together into a continuous run.
MV Cable Termination
A termination is installed at the end of a medium-voltage cable. Its primary task is to connect the cable conductor to an electrical apparatus or bus bar while managing the extreme electrical stress present at the cut cable end.
The most common connections of equipment are as follows:
- Switchgear: Connection between incoming and outgoing feeder lines inside substation apparatuses.
- Transformers: Transition from buried cables to transformer bushings.
- Motors: Connection of medium-voltage, high-capacity drives and motors in industrial plants.
- Busbars: Connection between cable ends and stationary power bars.
Upon cutting the shielded cable for connection to the terminal lug, you break the shield, which is a grounded metallic conductor. This break leads to a large concentration of electric field lines in the shield layer, which is called stress concentration. If there is no termination, such stress leads to the breakdown of the insulation near the termination point and results in a phase-to-ground flashover.
The termination helps in dealing with this problem through the application of a stress control device (geometric stress cone, high-permittivity stress control tube) that ensures a gradual decrease of the electric field. It also includes environmental sealing of the cable insulation. There are standardized industry recommendations for the selection and installation of medium-voltage termination devices (IEEE 1637).
MV Cable Splicing
A cable splice, which is otherwise known as a joint, joins together two cable segments that are laid out in a continuous line.
Some typical cases where the need for splices arises include the following:
- When Cable Exceeds Reel Lengths: Long cable installations often go beyond the length of the largest cable shipping reel and thus require splices.
- Cable Repair: In case a cable feeder buried underground gets damaged due to excavation or any other reason, it gets cut and replaced through splices.
- Branching Lines: T-splices or branch joints allow a main feeder line to supply tap-off loads.
A splice must rebuild every layer of the original cable. When two cable ends are spliced, technicians connect the conductors with a compression connector or shear-bolt sleeve, restore the inner conductor shield, rebuild the primary insulation, replace the metallic shield across the joint, and reseal the outer jacket.
Once completed, the splice must handle mechanical tension, resist groundwater ingress, and maintain dielectric strength identical to the original cable. Standards like IEEE 576 provide field-tested recommendations for selecting splice assemblies and carrying out reliable jointing procedures.
Side-by-Side Comparison
Parameter | MV Cable Termination | MV Cable Splicing |
Primary Purpose | Connects a cable end to electrical equipment | Connects two separate cable sections together |
Installation Location | Cable terminus (entry point to equipment) | Mid-span along a cable run |
Typical Applications | Switchgear, transformers, motors, and busbars | Cable extensions, damaged line repairs, route changes |
Main Function | Electrical connection, stress control, environmental sealing | Restores conductor continuity, insulation, shielding, and outer jacket |
How to Choose the Right Solution for Your MV Cable Project
Deciding between a termination and a splice is usually straightforward once you examine your line diagram, but selecting the exact specification requires deeper technical evaluation.
Engineering teams and sourcing managers should work through three practical steps before issuing purchase orders.
1. Start with the Project Layout
Map out every foot of the planned cable route and identify every transition point. Ask these foundational questions:
- Is the line terminating at a cabinet, transformer, or outdoor pole? If so, you need a termination kit matched to that environment (indoor vs. outdoor).
- Does the continuous pull exceed 1,000 to 1,500 feet? Check your reel limits. You will likely need inline splices to complete the run.
- Are you retrofitting an existing underground duct line? Maintenance projects often require specialized repair splices designed for tight space constraints inside manholes.
- Are there branch taps? Distribution networks tapping into main feeders require specialized branch or tee splices rather than standard inline joints.
Your physical layout directly determines the total count of terminations and splices required.
2. Match the Accessory to the Cable Construction
A cable accessory is only as good as its mechanical and electrical match to the host cable. Medium-voltage accessories must fit the cable’s dimensions and material properties precisely; there is no room for approximation.
Check the following five factors in accordance with the manufacturer's data sheets:
- Voltage Classification: Confirm that the accessory is suitable for your system voltage (i.e., 5 kV, 15 kV, 25 kV, or 35 kV) and Basic Impulse Level (BIL).
- Conductors' Sizes & Types: Accessories are made with specific sizes and materials (AWG or kcmil, or mm² for metric countries), along with specific types of conductors (either copper or aluminum).
- Insulation Types: XLPE and EPR cables have distinct characteristics of expansion dynamics and insulation diameter over insulation (DOI).
- Shields: Find out which kind of shield is used in your cables, as they can be tape shields, wire shields, LC shields, and jacketed concentric neutral (JCN). Terminals and splices have grounding equipment for each of these shields.
- Environment of Use: Indoor terminals are located in climate-controlled switchgear cabinets and have short creepage distances. Outdoor terminals have weatherproofing (rain sheds) against ultraviolet radiation, moisture, and environmental pollution.
Both IEEE and IEC standards emphasize that mixing incompatible accessory components with mismatched cable types is a primary cause of premature insulation breakdown.
3. Focus on Installation Quality
Field statistics show that the vast majority of medium-voltage cable failures occur at accessories, and most of those failures stem from installation errors rather than manufacturing defects. Whether installing a cold-shrink termination or a heat-shrink splice, workmanship quality determines long-term reliability.
Prioritize these field practices during construction:
- Follow Cutback Dimensions: Always strip cable layers to the exact millimeter specified in the installation instruction sheet. Incorrect cutback lengths misplace internal stress control components relative to the semi-conductive shield edge.
- Maintain Cleanliness: Dust, moisture, and oils from skin leave conductive tracking paths across high-voltage insulation interfaces. Keep tools clean and wipe down insulation with approved solvent wipes.
- Smooth the Semi-Con Transition: When stripping the semi-conductive layer, leave a clean, straight edge without nicking or gouging the underlying primary insulation. Any score mark on XLPE or EPR insulation acts as an initiation site for partial discharge.
- Ensure Ground Continuity: Double-check that ground braids or shield connectors are properly secured across splices and bonded to system ground at terminations. A floating or poorly bonded shield generates high induced voltages.
- Conduct Acceptance Testing: Once installation is complete, perform Very Low Frequency (VLF) withstand testing and partial discharge (PD) testing before energizing the line to confirm that accessories were installed without hidden defects.
Conclusion
Although MV cable terminations and MV cable splices are both crucial to power distribution systems, they perform distinct roles. Terminations safely connect cable ends to electrical apparatus while controlling concentrated electrical fields; splices restore electrical, mechanical, and insulation integrity across two joining cable sections.
Selecting the right solution requires reviewing your project layout, matching the physical and electrical specifications of your cable, and insisting on strict installation standards in the field. Skimping on accessory quality or installation oversight to save upfront costs almost always leads to premature line failure, expensive emergency repairs, and unplanned outages down the road. Proper selection and careful installation give your medium-voltage infrastructure the long-term operational reliability it needs.
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about HEBEI- HUATONG
Founded in 1993, Hebei-Huatong is a global cable manufacturing enterprise with production facilities located in Tangshan (Hebei Province, China), Busan (South Korea), Panama, Kazakhstan, Tanzania, Cameroon, and Angola. Its core product portfolio includes submersible pump cables for oil extraction, flexible moving cables for harbor cranes, cUL/CSA listed cables for AI PDU and marine shipboard cables. The company provides robust support for the continuous, safe, and efficient operation of industrial sectors worldwide, including offshore and onshore oil & gas exploration, and material handling via port cranes.
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