Loadbreak elbows connect underground distribution cables to dead front bushings on padmount transformers. They provide a safe and secure interface between the transformer and incoming electrical cables. In this article, we will explore the step-by-step process of installing 200 Amp loadbreak elbows on concentric neutral and copper tape shielded cables.
Note: This article is not a replacement for the manufacturer's instructions. Please reference the instruction manual that came with your loadbreak elbows for installation guidance.
Tools & Accessories you will need:
- Ruler
- Light marker
- Cable scoring tool
- Chamfering tool
- Pliers
- Mastic tape
- Electrical tape
- Cable cutting tool
- Insulation stripping tool
- A wire brush
- A lug crimp
- Cable cleaner
- Jacket removing tool
- Elbows and arresters
Continue reading and / or check out our video guide to installing 200 amp elbows. We will take you through each step of the process.
Installation Process
1. Identify The Bushings
Within the primary side of any padmount, you will find bushing inserts. A padmount set up for a loop feed application will have six bushings. A padmount configured for a radial feed application will have three bushings. Check out our article to learn more about radial and loop power distribution systems.
Inspect the loadbreak elbows selected for making up the cable connections to the transformer. Ensure the elbow connectors match the transformer’s bushing interface. The voltage class of the elbow connector should match the voltage class of the transformer bushings.
For both transformer types, make sure the bushings are statically grounded with a #14 AWG bare copper wire. This wire is called a drain wire. It is used to dissipate static charges between the bushing well and separable insert. Loop the drain wire through the grounding tab of the insert. Connect the other end of the wire to the metal bushing clamp.
If you have a six bushing primary transformer (loop feed) at the end of a radial lineup, make sure you install arresters on the other three bushings. This will protect the transformer from switching and lightning surges.
2. Determine Which Cable You Should Prepare
In this guide, we cover making up cable terminations with load break elbows for both concentric neutral and tape shielded cable. First, we’ll cover elbow terminations for concentric neutral cable. Skip to step 3b to learn more about copper tape shield cable installation.
3. Preparing Your Cable
Once you have selected your cable, follow the steps below to prepare the cable end.
3a. 15kv Concentric Neutral Cable
First, determine the proper cable length needed for the elbow termination. You will want enough slack in your cable to allow easy installation and removal of the elbow connector with a hot stick. First, train the cable in front of the bushing where the elbow will be installed. With the cable in place, use a light marker to indicate where the cable crosses the center of the bushing. Everything above your mark will be cut off in a later step.
Note: Leaving excess cable above this first mark will make it easier to ground the concentric neutral wires later on.
Measure the Cable
Measure and create a second mark 8 inches below your original mark.
Score the Cable
Use a scoring tool to remove the outer jacket from the mark you just made to the end of the cable. The end product should look something like the picture below.
Fold Concentric Wires Back
Wrap the end of the remaining jacket in mastic tape. Apply one piece around the jacket without stretching the tape. Next, take the concentric neutral wires and fold them back straight onto the mastic tape.
Apply Mastic Tape
Once the wires are bent back, add another ring of mastic tape on top of them. Then, secure the tape and wires with some electrical tape.
Cut off Extra Cable
After securing the concentric neutral wires, measure eight inches from the end of the cable and mark it with a light pen. Remove this portion of excess cable between your new mark and the cable end.
3b. Copper Tape Shielded Cable
Tape shielded cable requires a shield adapter kit to ground its copper tape shield. The shield adapter kit allows a connection to be made between the cable’s copper tape shield and earth ground.
Remove Copper Tape
Just like the concentric neutral cable, mark eight inches down from your first mark. Use a scoring tool again to remove the jacket from your second mark to the end of the cable. After scoring the jacket, remove it to expose the copper tape shield. This is where the process changes a little bit. Measure one inch from the end of the jacket and make a mark. Then, take your scoring tool and remove the rest of the copper tape to the end of the cable. You should be left with one inch of copper tape.
Install Shield Adapter Kit
To install the shield adapter kit, put some mastic tape around the edge of the cable jacket. Lay the ground braid from the shield adapter kit on top of the copper shield. Using a constant force spring, make two complete turns around the braid. Then, bend the braid back over the mastic tape and continue installing the constant force spring around the ground braid.
Apply Mastic Tape
Add another piece of mastic tape over the first layer of mastic to sandwich the ground braid. Next, cover the constant force spring with black electrical tape. The electrical tape should cover the constant force spring and mastic. The end result should look like the picture below:
At this point, you can go ahead and slide the cold shrink sleeve for the jacket seal over the cable to be installed later.
4. Strip Wire Insulation
Whether you are using a concentric neutral cable or a copper tape shielded cable, you are now ready to prepare the termination point of the elbow. Take an insulation stripping tool and strip back from the tip of the wire 2 ⅛ inches of insulation. This will expose the conductor.
5. Attach Connector to Conductor
Wire brush the exposed conductor to remove any oxidation. Next, install the compression connector for the size and type of your conductor. The compression lug should include an inhibitor. The compression lug must be installed with the inhibitor left inside. Rotate the compression lug to evenly distribute the inhibitor across the surface of the conductor. The hole at the tip of the compression connector will determine the orientation of the elbow’s probe. Make sure the flat end of the compression lug is facing the transformer bushing.
6. Crimp your Connector
Review the manufacturer’s crimping instructions for the compression fitting you are using. It should have directions on what tool to use and how many times to crimp the connector. Also, check and make sure your probe fits into your connector before attaching it. When attaching the compression connector, rotate the crimping tool after each crimp to prevent bowing the connector.
7. Reveal The Cable Insulation
Once the connector is crimped, measure 6 ⅞ inches from the end of the connector and make another mark. With a scoring tool, remove the semiconductor screen from your new mark to the end of the compression connector. Take care to ensure the blade of the scoring tool does not cut completely through the layer of semicon. This will prevent any cuts or scratches to the insulation during scoring. Start out with a square cut at your mark on the semicon; the first cut must be perfectly smooth. Avoid any jagged edges. A small vice clamped next to your scoring tool will help you get a clean square cut on the first pass around the semicon.
Make the initial cut around the semicon (keeping the scoring tool square against the vice clamp). Make one even, complete revolution, then spiral outward toward the end of the cable. Remove the semicon, and lightly inspect the insulation for any scratches or cuts. If you feel any cut or nick in the insulation with your finger nail, you need to start over.
8. Chamfer The Cable
Take a chamfering tool and pass it around the outside edge of the insulation. This should create a ⅛ inch bevel. Chamfering allows the elbow to slide on easily.
9. Clean your Cable
Clean the insulation thoroughly before you attach the elbow. Use a cleaner specified for transformer cables. Spray the cleaner into paper towels and wipe down the cable. Use a clean paper towel each time you wipe down the insulation.
Then, take the silicone supplied with the elbow and apply an even coat over the insulation. This is to: fill any tiny voids on the surface of the insulation, create a watertight seal, and aid in the installation of the elbow.
10. Install the Elbow
Align the elbow and compression connector (this will allow the probe to be threaded into the elbow properly). Once aligned, slide the elbow down onto the cable. Then, hand thread the probe into the connector to avoid cross threading. As you insert your probe, be careful not to damage or contaminate the white part of the probe.
Use the included wrench to continue twisting the probe after you cannot turn it anymore with your hands. Continue turning the wrench until the handle of the wrench is bent 90 degrees off from its original position. You will know that your probe is properly inserted when your wrench deforms at 100-120 inch/lbs of force.
11. Wrap the Jacket Seal
To keep moisture from getting into the cable’s jacket, follow these steps to install the jacket seal kit. Put a piece of mastic tape at the edge of the jacket. Position the jacket seal over the elbow and cable jacket. Then, begin pulling the plastic out from the jacket seal to shrink it over the elbow and cable.
Now take one of your concentric neutral wires and ground your elbow. Pull the wire through the ground tab on the elbow, wrap it around itself a couple of times, and cut off the excess.
Take the rest of your concentrics and bond them to earth ground. Before you plug your elbow in, put a thin layer of silicone around your bushing. You can tell that your elbow is properly seated onto your bushing when the yellow ring around the bushing is completely covered by the elbow.
Follow Up
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