Stress Cones


Stress cones conduct heat and electricity to spread voltage across a wire, preventing electrical surges and fires. In this article, you will learn how stress cones work, how to install a stress cone, the difference between stress cones and potheads, and other frequently asked questions. 

How Stress Cones Work

Electrical and motor insulations benefit from an added layer of protection provided by stress cones. These cylindrical cones transmit voltage over the line and conduct heat and electricity to reduce electrical surges and fires. Although it is also possible to use them for cables with a higher voltage, stress cones are typically utilized for wires between 6 kV and 25 kV.

Cones under stress aid in insulating cables, connections, and terminals. Cones help in preventing insulation failure by the intense electrical and heat buildup between cable conductors, shield termination, and cables. If the semiconductor layer of wiring fails, stress cones come in as a backup. They also support in spreading heat and electricity throughout the wiring, reducing energy spikes that can result in power outages, electrical issues, and fires.

How to Install a Stress Cone

Installing stress cones on motors are typically done post manufacturing, rather than by the motor manufacturer’s supply. Remember that the manufacturer will provide a conduit box with enough space for the stress cone on each lead if a customer requests stress cones.

De-energize the device or supply cables before installing a stress cone – this is crucial for the safety of the person installing or working with the power supply. Then, cut off the power to accomplish this. Here are the detailed instructions on how to install a stress cone:


Turn off the electricity at the main distribution panel for the cables you are working on. By applying a non-contact voltage detector to the insulation of the wires, you may verify that the power is off. Trying to turn on the associated gadget will help confirm that the power is off.

Step 2

Next, pull the cable’s end into a position that may be easily accessible. Calculating the amount of exposed line needed to complete your connection once the stress cone has been erected beforehand is helpful. Depending on the object to which you are attaching it. To find out this information, consult the owner’s manual.

Step 3

After removing the concentric neutral wires from the exterior of the cable, pull back the length of the exposed line plus the length of the stress cone. The wires that are around the cable’s outside are concentric neutrals. Now, these make up the ground lead.

Step 4

The next step is to ascertain the length of insulation that needs to be taken for a particular stress cone. The owner’s manual contains this information. Add this measurement, to the size of the exposed cable. Cut and remove the semiconductor shield wire to this length. Note: Avoid cutting or nicking the insulation at all costs.

Step 5

Cable termination with a stress cone
Courtesy: ResearchGate

To get rid of the semi-conducting residue, clean the freshly exposed portion of the insulation with a rag dipped in safety solvent. Remember not to clean the cable; only remove it. Next, wrap the wire in electrical tape 25 mm from the newly exposed area. Apply the provided lubricant to the stress cone’s interior surface and the cable insulation.

Step 6

To start, rotate and push the stress cone onto the cable’s end until the stress cone’s end is flush with the electrical tape. Then, lubricate the interior of the modules, then rotate them as you slide them onto the cable end. In continuation, install each module by repeating this procedure.

Step 7

Using a screwdriver to tighten the grounding clamp, wrap it around the stress cone. Run a 14-gauge copper wire to the system grounding location from the clamp. Next, connect the grounding system to the concentric neutral wires as well. In continuation, connect the ground terminal with both of the cables.

Step 8

In continuation, use a knife to score the insulation on the top of the last module to mark it. After finishing the incision through the insulation, remove the final module. Reinstall the final wire module.


These guidelines are for a particular kind of stress cone. Use the instructions that came with your device at all times.

Stress Cones vs. Potheads

An insulated electrical connector called a pothead is used to connect overhead wiring to equipment like transformers or to switch from an overhead line to an underground high-voltage cable. Its name refers to the method of potting or encapsulating the conductors inside the insulating bushing of the terminal.

Stress cones employ with potheads. Three typical styles are available for application.

First, stress cones are constructed inside the pothead, and a jumper cable is attached to the pothead’s original phase leads. The original phase leads are then used to construct stress cones inside the pothead. Finally, the initial phases are built upon to create molded stress cone leads.


What is Cable Stress?

Main reason of cable stress
Courtesy: Gore

Cables can flex in one or more of the four basic motions shown above . When this happens, a cable’s copper conductors and shields strain every time it bends or flexes.

Any line that flexes might fail for three main reasons: conductor and cable insulation degradation, ,deterioration of cable and conductor insulation, and fatigue of the conductor and shield in the flex area. Exhaustion of the conductor and protection at the point of termination may also cause for failure.

How do corona rings work?

Corona Rings found outside in a tower
Courtesy: Wikipedia

The word “corona ring,” more appropriately “anti-corona ring,” refers to a toroid of conductive material, typically metal, attached to a terminal or other nonstandard high-voltage equipment. The corona ring distributes the electric field gradient and brings its maximum values below the corona threshold. Corona rings are perfect for utilization on switchgear and insulators for high voltage power transmission and on high voltage generating equipment for research. The grading ring are also of use for surrounding insulators.