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VI How to Fix (By Jody Boucher, Northeast Utilities)
 Figure 17. Grease products such as this require proper application for satisfactory results. |
 18A. These RFI clips are used to eliminate poor connections between insulator units. They are very easy to apply and economical. There is no need to replace insulators when these clips are used. The clip install tool above. |
 Figure 18B. The clip is shown being installed. |
 Figure 18C. The completed clip installation. |
Power-line RFI repairs typically involve eliminating an arc of some type. As we discussed previously, the arc occurs in an air gap located between two conductors on a pole or other source on the structure. The conductor materials can be wood, metal, dirty insulators -- just about anything that can conduct electricity -- and not necessarily a primary conductor. Arcs can occur for several reasons, including loose hardware, a cracked insulator, tracking, corrosion between two pieces of metal, or a loose tie wire. Since a difference in potential across a gap creates the arc, it stands to reason that eliminating the gap can repair most power-line RFI problems.
Once a noise source is located, a solution must be determined. The question of "what exactly needs to be done' may require some good judgment on the part of the troubleshooter. Obviously a line crew must go to the site and make some sort of repair. But what repair or replacement? This decision is typically based on a number of factors. How much work is involved? How many poles require attention? Is this an isolated or widespread problem? Has equipment deteriorated to a point that it needs to be replaced? Good judgment is essential for an effective and economical repair. Sound decisions will always help determine the best course of action to initiate a cure. A simple job of tightening loose hardware vs. an equipment replacement must be considered carefully when examining the possible options.
One popular option for a simple fix is a grease compound. The grease is applied to the offending gap in order to bridge it. Be cautious however. Grease may be only a temporary fix. Unless a suitable product has been correctly applied to the offending gap, it may eventually diminish in the elements or wash out by rain. The problem can then re-occur. In either case however, grease can be a temporary fix until a long-term solution can be initiated. See Figure 17.
Long-term repairs eliminate the gap by replacing the
offending part, tightening hardware, or by cleaning to prevent tracking. Freezing and thawing can cause hardware to
loosen, especially in colder climates.
Helical spring washers added to the bolts can absorb the expansion and
contraction of wood poles and maintain hardware tension to prevent gaps from
forming.
 Figure 18D. The final installation shorts all three components of the insulator assembly. |
In some cases, it may be better to replace an insulator with a modern polymer unit tie instead of re-tying the old one. The new design does not require a wire. It also eliminates the possibility the problem could reoccur in addition to a second and costly visit by a line crew. The line crew and truck are by far the most expensive part of power-line noise repairs. In most cases, the cost of replacement parts is only a small fraction of the total expenditure. Also, jobs written as a capital replacement can possibly be charged at the utility rate base. Most maintenance budgets are tight these days so any chance to capitalize a project and upgrade the plant is an economical advantage.
New products and materials for line construction are constantly evolving in the industry. For example, polymer construction of various types of post top insulators, dead ends and fused cut outs provide higher Basic Insulation Level (BIL), lighter weight and are less prone to stress cracks. Vice top polymer insulators are far superior to wire ties that can arc when loose, especially in cases involving Poly covered wire (commonly used in the northeast United States). See Figure 18.
The most cost effective repair is a single repair done only once. Getting it right the first time not only helps maintain customer satisfaction, it's essential for an economic problem solving. Replace versus repair of offending equipment often depends on the balance between a repair's level of difficulty and economic justification of its unit cost. Complete replacement for older, obsolete or damaged equipment may be a better choice.
