Stress Cones
- Thread starter blues
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What's the voltage?
How are you going to get them any closer than the termination points without adding spacers? you bolt them to the termination points, the distance will take care of itself. The XF was or should have been built to standards that take distances into account.
http://www.google.com/url?sa=t&rct=...5oGwAg&usg=AFQjCNGbZ5o4UChHu7S4U5eQ-ZtDIUuqEw
http://www.google.com/url?sa=t&rct=...5oGwAg&usg=AFQjCNGbZ5o4UChHu7S4U5eQ-ZtDIUuqEw
rcwilson
Senior Member
- Location
- Redmond, WA
Voltage on the surface of a stress cone goes from line voltage (say 4.16 kV) at the terminal end down to zero at the ground strap or cable jacket. The stress cone stretches the voltage along its length to minimize voltage stress on the insulation boundary.
At the bottom, there is no spacing requirement. It is like cables in a conduit. At the termination, the spacing required is the same as the transformer or switchgear termination. Consider all parts of the upper stress cone as energized.
Where I have seen problems is in tight enclosures where stress cones from different phases touch in the middle where the voltage is not zero, maybe 2300V phase-phase.
I think there must be ways of insulating the stress cone to prevent problems. Check with Raychem or 3M or other suppliers for a solution. If there wasn't, how could we safely terminate in a 5 kV motor j-box?
At the bottom, there is no spacing requirement. It is like cables in a conduit. At the termination, the spacing required is the same as the transformer or switchgear termination. Consider all parts of the upper stress cone as energized.
Where I have seen problems is in tight enclosures where stress cones from different phases touch in the middle where the voltage is not zero, maybe 2300V phase-phase.
I think there must be ways of insulating the stress cone to prevent problems. Check with Raychem or 3M or other suppliers for a solution. If there wasn't, how could we safely terminate in a 5 kV motor j-box?
Why isn't the box large enough to accomadate the 5kv cones?
Sounds like it might be a NEMA issue.
rcwilson
Senior Member
- Location
- Redmond, WA
I was comparing a motor junction box where we splice a shielded cable to the unshielded motor lead with air terminal chambers in switchgear or transformers where the terminals are fixed and might be bare - no tape or insulating boots. Some motor boxes have fixed terminals and plenty of room for stress cones. Others just have the motor leads, like 480V motors. The connection gets taped or heat shrink insulation is applied to insulate the splice. If the tape doesn't cover all of the stress cone, the active parts of adjacent cones can touch.
After thinking about it, I need to talk with manufacturers to see if the standard heat shrink stress relief has an integral insulation layer that would make these concerns go away.
rafael rivera
Member
Hoping for a great weekend to all;
Termination Kits Manufactures offer what's know in the industry as " Rejackets ". this is nothing else but insulation hose ( Polymer ) that its installed over the length of the conductor after is has been strip out, the Stress Cone bottom end goes over the top end of the rejacket, bottom end of rejacket goes as far back to on the conductor as you may required. We have done a lot of it specially applycated to Multiconductors HV Cables, the
" Rejacketing " is installed as back as where the cable jacket was stripped out and a cable breakout boot is installed over to make the installation weather proof. 3M, Raychem, Prysmian Guard they all make this for different applications and voltage levels.
This statement does not answers the OP's question but will prevent having problems downsteams from where the conductors terminates as
RJ Wilson mentioned on his reply.
Regards.
Termination Kits Manufactures offer what's know in the industry as " Rejackets ". this is nothing else but insulation hose ( Polymer ) that its installed over the length of the conductor after is has been strip out, the Stress Cone bottom end goes over the top end of the rejacket, bottom end of rejacket goes as far back to on the conductor as you may required. We have done a lot of it specially applycated to Multiconductors HV Cables, the
" Rejacketing " is installed as back as where the cable jacket was stripped out and a cable breakout boot is installed over to make the installation weather proof. 3M, Raychem, Prysmian Guard they all make this for different applications and voltage levels.
This statement does not answers the OP's question but will prevent having problems downsteams from where the conductors terminates as
RJ Wilson mentioned on his reply.
Regards.
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