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Sag Line Mitigator Update

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Progress is excellent.

1. Utility Lineman Perspective:
2. Revised Test Plan
3. Opportunities

———–background info—————
Previous UFTO Notes:

— Sagging Line Mitigator; Mon, 08 Mar 1999

This unique device would replace or work with standard insulated hangers on power transmission towers, to counteract the effect of temperature on the sagging of overhead transmission lines. This allows increased line ampacity (load current capacity) of existing lines during curtailed summer months, reduced tower heights, and/or increased tower spacing. This device will significantly reduce the risk of forest fires and outages caused by sagging lines, increase the efficiency of energy transfer, delay the need for additional line capacity, and delay the construction of new lines.

— T Line Sag Mitigator Gets Funding; Partner Wanted; Tue, 29 Jun 1999

— US Patent No. 5792983 Aug. 11, 1998
SAG COMPENSATOR FOR SUSPENDED LINES USING ROTARY MOTION
Abstract: The invention used devices that change in length as a function of temperature to mitigate sag in a suspended line. The devices have actuators which change in length as a function of temperature. This change in length is transferred to a linkage mechanism, such as a cog or disc, which amplifies the change in length and changes it to rotational motion that tensions the suspended line. Therefore, the same change in temperature that causes the suspended line to sag will cause the device to actuate a rotary motion that reduces line sag.
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Progress is excellent.

1. Utility Lineman Perspective:

Earlier this month, the construction coordinator for T&D reliability at a major utility visited the company to discuss the role of a Lineman in transmission line work and to provide input on the current SLiM design, functionality, and its proposed installation procedure.

The visit began with a review of the SLiM overall concept, the current design status, and current challenges, providing the relevant information he needed to evaluate the device from a Lineman’s perspective. After seeing the 3D computer animation of the SLiM models and the full-size mockup, he was very optimistic about how SLiM would be received by both T&D operators and lineman: “…if this device does what it is designed to do, it should sell like hot cakes!…” His view on the installability of the device was that it would be relatively simple to do using existing installation procedures and equipment.

The second topic of discussion involved a detailed review of installation procedures for SLiM and line attachment hardware. Previously three methods of line contact had been identified for SLiM: compression dead-end, preformed dead-end, and mechanical jaw grip dead-end. Based on this meeting, two methods of attachment were considered as the most common to be used by utilities; compression dead-end and strain clamp dead-end (new, not previously considered). Each attachment method would have its own installation procedure for live line work; “Bare Hand” technique and “Hot Sticking” technique respectively. These procedures will be outlined in detail in a future report once they are completed.

Conclusions/actions:
– The SLiM concept was seen as a very attractive method of resolving sag related issues,
– The SLiM device would require nothing more than standard installation procedures and equipment, and
– General guidelines will be developed for SLiM installation techniques using utility experience and knowledge.

2. Revised Test Plan

To demonstrate the functionality and integrity of the device, the company has decided to replace the original plan to test the device in the field with a host utility, with a plan to do controlled tests in a laboratory setting.

Reasons for the change– field testing appears not to be feasible, and won’t get the needed information:
– Field testing at a remote site does not allow sufficiently close testing control to measure all relevant parameters at the right time.
– Field testing on a real line significantly limits our response and our ability to efficiently implement design changes that may be required (and are identified) as a result of testing.
– Field testing, most probably, will not impose the device to the extreme conditions at which it needs to be tested. Furthermore, it only would test for a specific environment that is not applicable to other conditions.
– Convincing a utility to install these devices on heavily transit lines in nearly impossible and installing them on light-duty loads would be almost useless.

The new plan:

— Utility Survey and Testing Site.
The objective of this new task will be to conduct a utility survey, generate awareness and interest amongst utilities about the product, and solicit a host siting for part of testing.

— Conduct lab and field testing, improve/optimize designs, finalize the product design.
The test plan will be implemented by a series of lab and “field” testing. These tests will be conducted “interactively” in environments that are controllable and manageable. Test results will be used to improve designs and retest if necessary. The final outcome of this task will be a device or a family of devices which will have passed all testing requirements such that they will function as intended when installed on actual power lines.

3. Opportunities

1. Suggestions for who might be able to help them with the survey?
2. Active participation in the development– advisory, in-kind, investment, testing.
3. Suitable lab needed- business arrangements to be determined. An RFP will be issued in a few weeks. Let me know if you’re interested.

CONTACT:
Contact: Dr. Manuchehr Shirmodhamadi
Material Integrity Solutions, Inc., Berkeley, CA
510-594-0300 x202 mshir@misolution.com

Sagging Line Mitigator

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Sagging Line Mitigator (SLiM)

This unique device would replace or work with standard insulated hangers on power transmission towers, to counteract the effect of temperature on the sagging of overhead transmission lines. This allows increased line ampacity (load current capacity) of existing lines during curtailed summer months, reduced tower heights, and/or increased tower spacing. This device will significantly reduce the risk of forest fires and outages caused by sagging lines, increase the efficiency of energy transfer, delay the need for additional line capacity, and delay the construction of new lines.

The design philosophy is: “Because of the unpredictable nature of ambient temperature, elimination of the sag must be accomplished by a device which operates based on the same change in temperature.”

This automatic mechanical device would counteract axial expansion and hence sagging of suspended lines, such as those used in overhead electric transmission lines, due to ambient temperature increases. The device keeps the profile of the line and hence its sag constant and independent of ambient temperature changes. This device works on the same principal as the axial thermal expansion mechanism of the line but reverses its impact on the sag. That is, as ambient temperature increases (or decreases) so does the line length and its sag. The same ambient temperature change will increase (or decrease) the length of an actuator. The change in actuator length is amplified and transferred through a series of mechanical linkages comprising of lever-type devices, cogs, gears, or alike to contract (or extend) the line connections to the device such that the increase (or decrease) in line length is compensated for.

Several concepts are considered for the actuator. One uses a material with a high thermal expansion coefficient and a high compressive modulus of elasticity. Another uses a series of shape memory alloys for response to temperature changes. Yet, another uses an incompressible fluid with a high bulk modulus. Either device can also be “heated” for higher performance by wrapping it in a “heater coil” powered by the magnetic flux of the power line.

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