UNITED STATES

DEPARTMENT OF AGRICULTURE

RURAL UTILITIES SERVICE

SUMMARY OF

ITEMS OF ENGINEERING INTEREST

AUGUST 1996
Items of Engineering Interest

August 1996

TABLE OF CONTENTS

ITEM PAGE

PROCUREMENT & CONSTRUCTION

Guidelines for Approving the Use of Steel Distribution Poles................................................1

Purchase of Steel Poles.........................................................................................................3

Pole Embedment ..................................................................................................................4

ACSS Conductor .................................................................................................................4

Special Conductors for Bare Overhead Lines........................................................................5

Use of Stirrups.....................................................................................................................7

Use of Standoff Brackets on Full Round Cable Riser Shields................................................9

Guy Attachments................................................................................................................ 10

Guy Markers...................................................................................................................... 10

Keep Testing Your Underground Power Cable................................................................... 11

ANSI Standard for Testing Hardware................................................................................. 13

OPERATION

Safety Signs ....................................................................................................................... 14

Automatic Meter Reading .................................................................................................. 15

INSPECTION & MAINTENANCE

Pole Inspection and Maintenance........................................................................................ 16

Inspection & Maintenance Form for Pad-Mounted Equipment............................................ 16

SMD Power Fuse Unit Bore Closedown............................................................................. 17

Simplified Replacement Guide for Medium Voltage Cable.................................................. 18

ENVIRONMENTAL MATTERS

Raptor Electrocutions on Electric Utility Overhead Structures............................................ 20

Insulated Distribution Transformer Covers......................................................................... 23

Control of Sulfur Hexafluoride (SF6) Emissions.................................................................. 23

ADMINISTRATIVE

Recent RUS Engineering Publications ................................................................................ 24

Transmission and Distribution Engineering Committee ....................................................... 25

APPENDICES

Appendix A -- Inspection & Maintenance Form for Pad-Mounted Equipment..................... 29

Appendix B -- Underground Cable Failure Report............................................................. 30

Appendix C -- Electric Staff Division Directory.................................................................. 31
Items of Engineering Interest

August 1996

ABBREVIATIONS

AAC All Aluminum Conductor

AAAC All Aluminum Alloy Conductor

ACSR Aluminum Conductor Steel Reinforced

ACSS Aluminum Conductor Steel Supported

ACSS/TW Aluminum Conductor Steel Supported - Trapezoidal Wire

AMR Automatic Meter Reading

ANSI American National Standards Institute

ASTM American Society for Testing and Materials

BIL Basic Impulse Level

DSM Demand Side Management

EPA Environmental Protection Agency

EPR Ethylene Propylene Rubber

FCC Federal Communications Commission

HMW High Molecular Weight

HMWPE High Molecular Weight Polyethylene

IEEE Institute of Electrical and Electronics Engineers

kV Kilovolt

RUS List of RUS Informational Publication 202-1, “List of Materials

 Materials Acceptable for Use on Systems of RUS Electrification Borrowers”

MOV Metal Oxide Varistor

NESC National Electrical Safety Code

NRECA National Rural Electric Cooperative Association

OCF Overload Capacity Factor

OHGW Overhead Ground Wire

REA Rural Electrification Administration

RTP Real Time Pricing

RUS Rural Utilities Service

S&C S&C Electric Company

SSAC Steel Supported Aluminum Conductor

T&D Transmission & Distribution

TOU Time-of-Use

TR-HMW Tree-Retardant High Molecular Weight

TR-XLPE Tree-Retardant Cross-Linked Polyethylene

UL Underwriters Laboratory

USFWS United States Fish & Wildlife Service

VR Vibration-Resistant

XLPE Cross-Linked Polyethylene
Items of Engineering Interest

August 1996

1

PROCUREMENT & CONSTRUCTION

GUIDELINES FOR APPROVING THE USE OF STEEL DISTRIBUTION POLES

RUS has several areas of consideration regarding the use of steel distribution poles by borrowers.

For your information and reference, we have listed below the guidelines that we are presently

using when considering borrower requests for RUS approval to use steel distribution poles. We

request that borrowers seeking RUS approval to use steel distribution poles on their systems

adequately address each of these items:

1. Approval is only being granted on a case-by-case trial basis to gain experience.

2. Presently, approval is only being considered for site specific projects defined by the

borrower.

3. The borrower should state the maximum number of steel poles to be used.

4. The borrower should furnish an analysis, using sound engineering economics, of the

cost of using steel poles compared to standard RUS construction with wood poles.

If the use of steel poles is more costly, other sound reasons should be furnished to

justify their use.

5. All assembly units have to be built according to RUS construction standards. If

nonstandard construction is proposed, the borrower must furnish sufficient

dimensioned drawings and other information for our evaluation of the design.

6. The borrower needs to furnish sufficient information and data describing the

proposed steel poles including the methods and materials of surface coating to be

used to protect the poles and pole butts against corrosion.

7. All other material to be used has to be RUS accepted or RUS technically accepted.

A compilation of accepted materials may be found in RUS Informational

Publication 202-1, “List of Materials Acceptable for Use on Systems of RUS

Electrification Borrowers” (RUS List of Materials). Inquiries regarding technically

accepted materials should be directed to the Chairman of Technical Standards

Committee “A” at (202) 720-0980. The borrower must furnish sufficient

information, data and test results of all proposed nonaccepted material for our

evaluation.

8. RUS strongly advocates a minimum withstand strength, (often incorrectly and

simply referred to as a BIL level), of 300 kV for distribution pole top assemblies

attached to steel poles. A minimum of 300 kV withstand must be maintained at

deadend assemblies. The borrower should make clear what assemblies and materials

are to be used and the resulting calculated withstand strength level. If the design is

less than 300 kV, the borrower should state what additional measures, if any, such

as the installation of surge arresters, are to be used to minimize flashovers.

(Withstand strengths of less than 300 kV will usually facilitate

flashovers of lightning strikes to or proximate to distribution lines.
Items of Engineering Interest

August 1996

2

A recloser operation is usually required to clear the resulting arc.

Thus, a minimum of 300 kV withstand is required to maintain a

reasonable quality of service. Standard RUS pole type assemblies,

with wood poles, have a minimum withstand strength of 350 to

400 kV. For mathematical purposes, the total resistive type

impedance of wood and capacitive type impedance of insulators

should be added as perpendicular vectors.)

9. The borrowers should state what existing and additional safety measures, for line

workers, will be enforced to compensate for any reduced electrical clearances

between energized conductors and the proposed steel poles.

10. The borrower needs to furnish a statement regarding the anticipated impact of the

steel pole design on the potential electrocution of raptors and identify any mitigation

measures that will be incorporated in the design.

11. A steel pole may be used as a part of a grounding circuit if the pole meets the

sufficient conductivity and low impedance requirements of the National Electrical

Safety Code (NESC) and other RUS specifications. A directly embedded steel pole

is not recognized in the NESC as a grounding electrode. Therefore, RUS requires

that separate driven ground rods or grounding electrodes be used for all equipment,

surge arresters and other required system grounds.

12. The borrower should use stainless steel or galvanized steel ground rods and soft

annealed iron ground wire to mitigate the corrosive affects of buried dissimilar

metals in close proximity.

13. RUS advocates using steel poles that meet the strength requirements of the NESC

Grade B construction. The design of the distribution line itself only needs to meet

NESC Grade C construction. Extreme ice conditions and appropriate high winds

should be considered in the construction design.

14. The design of unguyed angle and deadend structures should consider pole deflection

and will usually require greater embedment depths.

RUS does not judge the above items to be onerous. Each item is important for a sound and safe

design. The relevant items above, plus several other design considerations, are incorporated in

RUS construction drawings and specifications for wood pole distribution lines.

If you would like more information or have any questions, please call James L. Bohlk, Electrical

Engineer, Distribution Branch at (202) 720-1967.

PURCHASE OF STEEL POLES

To help expedite delivery of steel poles, purchasers should provide complete design parameters

and details of other features such as anchor bolts and related foundation requirements.
Items of Engineering Interest

August 1996

3

Normally, steel pole manufacturers prepare specific pole designs tailored to the loads and pole

geometry specified. Manufacturers may also supply orders from stock of available steel poles,

designed as equivalent to standard wood poles in height and classes. In selecting the type of

supporting structures to be used on a line project, the design engineer should investigate which of

the structure options will result in the more cost efficient approach.

Confusing pole loading tree data, drawings, or load conditions may cause misinterpretation or

misapplication of the intended design requirements. Pole fabrication may be delayed if subsequent

design changes for the poles are necessitated. Some of the factors to consider for the

specifications on the design and fabrication of steel poles include the following:

• Length or height above the groundline, as well as the total pole length, should be

shown on the drawings and in the pole data table of dimensions.

• Controlling dimension for the arm lengths should be clearly shown on the drawing.

This controlling dimension should be shown in one of three ways: from the pole

centerline, from the face of the pole, or from the edge of the arm's end bracket.

• Specify the shape of the arm, straight or curved. Indicate insulator swing clearances

to be maintained, and arm rise dimensions. Straight arms are suggested if the arm is

less than 5 feet (1.5 meters) long.

• For steel arms on suspension type poles, the elevation dimensions should reference

the insulator attachment hole at the tip of the arms. For arms on deadend poles, the

dimensions should refer to the centerline of the arm tip.

• When specifying loads, use one global system of x-, y-, and z-coordinates on all the

pole drawings, with the appropriate sign convention, to represent combined vertical,

transverse, and longitudinal forces.

• For each pole drawing, show a load tree with load force vectors at wire attachment

points. For each loading case condition, specify the loads, wind pressure on pole,

and overload factors, in tabular format, and how the loads are to be applied for the

load case. Generally, it is clearer if the values in the load table have been resolved

and combined into a set of x-, y-, and z-coordinate loads, rather than in other forms,

such as showing the loads as conductor tensions or wire loads in pounds per foot

(Newtons/meter), requiring additional calculations. This approach is recommended,

especially if the poles include underbuild which have spans and line angles different

than the transmission line.

• Pole design should include possible conditions where complex wire arrangement,

underbuild, or future additions are involved. When specifying loads, the designer

should consider reversing transverse wind loads, unbalanced longitudinal loads (if

any), as well as various wire combinations. For complicated loadings, additional

plan and elevation views may be needed to clarify the loadings and their directions.

• For an unguyed, deadended single pole steel structure designed for a range of line

angles, the design loads for the minimum line angle should also be specified to
Items of Engineering Interest

August 1996

4

properly design the arms (the maximum line angle loads usually control the design of

the pole and foundation).

• For a steel pole structure to be cambered or raked, the load condition to calculate

the camber or rake should be specified.

• For guyed steel pole structures, the type, size of guy wire, maximum number of

multiple guys (if any), guy anchor locations, and guy slopes should be provided.

• If using concrete drilled pier or caisson type foundations, the minimum compressive

strength of the concrete should be specified so that the steel pole supplier will be

able to properly design the base plate and anchor bolt cage assemblies.

• If switching equipment is to be installed on the pole, the switch manufacturer's

drawings and details should be provided to the steel pole supplier.

If you would like more information or have any questions, please call Bing C. Chan or

Donald G. Heald, Structural Engineers, Transmission Branch, at (202) 720-0999 or

(202) 720-9102, respectively.

POLE EMBEDMENT

RUS announces the issuance of RUS Bulletin 1724E-205, “Design Guide: Embedment Depths

for Concrete and Steel Poles,” dated August 22, 1995. This new bulletin provides engineering

information concerning selection of embedment depths for steel and concrete transmission poles

subject to large overturning moments.

Increasing use of steel and concrete poles has necessitated a more definitive method of

determining pole embedment depths. The primary purpose of this bulletin is to furnish

engineering information concerning selection of embedment depths for steel and concrete poles in

different types of soils. The information in this bulletin may be used to approximate embedment

depths for cost estimates, to make preliminary selection of embedment depths, and to verify or

check selection of embedment depths based on other or more exact methods.

If you would like more information or have any questions, please call Bing C. Chan, Structural

Engineer, Transmission Branch, at (202) 720-0999.

ACSS CONDUCTOR

Type ACSS conductor has been used on transmission uprating projects due to its better sag

characteristic when compared to type ACSR conductor. The conductor (previously known as

SSAC) is covered by ASTM designation B 856, for type ACSS, Aluminum Conductors,

Coated-Steel Supported, with aluminum round wires, and ASTM B 857, for type ACSS/TW,

with trapezoidal-shape aluminum wires. Both ASTM standards have been adopted by ASTM and

will appear in the next ASTM Standards, Volume 02.03, Electrical Conductors.
Items of Engineering Interest

August 1996

5

The aluminum material in ACSS has been annealed and is "softer" than the aluminum for type

ACSR conductor. ACSS has slightly better conductivity than conventional ACSR, but its

principal advantage for line upgrading is its better sag-tension characteristics. Because the

conductor tension is carried almost entirely by the steel strand, type ACSS conductor will sag less

than ACSR under high electrical loads. It is a good conductor to consider whenever there is a

considerable range between the "normal load" and the "peak load".

Due to the soft aluminum, it may be difficult to install the conductor without some local

deformation. For example, at deadends, some birdcaging of the conductor at compression

deadend clamps can occur during installation. To reduce birdcaging, the "come along" should be

attached as far out as possible. Minor birdcaging with ACSR may also result, but the effect

usually is temporary and disappears by the following day after sustained loading. With ACSS, the

birdcaging may remain because the conductor wires are bent outward. A wood block may be

useful in reforming the ACSS wires.

The aluminum sleeve of the compression clamp that some manufacturers furnish for ACSS may

be longer than the compression clamp for a comparable size of ACSR conductor. This may

actually increase the birdcaging problem.

The conductor should not be used for voltages at or above 230 kV because radio and television

interference may result. This conductor is not RUS accepted (i.e., not included in the RUS List of

Materials), and as such, its use for a line project is considered on a case-by-case RUS approval

basis.

If you would like more information or have any questions, please call Donald G. Heald, Structural

Engineer, Transmission Branch, at (202) 720-9102.

SPECIAL CONDUCTORS FOR BARE OVERHEAD LINES

Twisted-pair conductors (also known as type T-2) are used for overhead lines in areas prone to

conductor motion problems caused by wind acting on conductors coated with ice. The conductor

consists of two component type AAAC or ACSR conductors twisted together to form a figure-8

shape. The nonsymmetrical conductor profile presented to prevailing wind is designed to reduce

or resist wind-induced motion, oscillation or vibration of the iced conductors. Conductor motion

problems of conventional ACSR conductors have occurred on rural lines in the Midwest and

north central areas of the U.S. and have resulted in failures of wires or strands. Key contributing

factors are: location, line orientation to prevailing wind direction and wind speed, and terrain

topographic features. T-2 conductor was originally developed by Kaiser Aluminum with field

testing beginning in 1968. Initial line performance data and conductor observations were reported

for the 1970-1980 period. Kaiser Aluminum has since sold its interest in the type T-2 conductors.

In order to obtain experience, twisted-pair conductor is conditionally accepted on page av(1), of

the RUS List of Materials. Currently, four manufacturers of the special conductor are included.
Items of Engineering Interest

August 1996

6

The conductor sizes are limited to standard ACSR and AAAC conductors in the RUS preferred

sizes (RUS does not include type AAC conductor). Component conductors must meet the

applicable ASTM specifications for ACSR and AAAC wires and stranded conductors.

Additional notes on the twisted-pair conductor are:

1. Selection and design of the special conductor should be based on an engineering

study or recommendation which should include such considerations as: history,

performance of existing lines with similar terrain, line orientation, and wind

conditions.

2. Presently, no industry-wide accepted standard exists for the special conductor. This

conductor's twist lay direction and lay length may vary among the manufacturers and

differences may exist if the same size of conductor is obtained from different

suppliers. ASTM Committee B-1 on Electrical Conductors, is presently working on

draft specifications covering material and testing requirements for twisted-pair

ACSR conductors for adoption as an ASTM standard. Balloting of the proposed

draft is scheduled for late 1996 or early 1997. Also planned are ASTM

specifications for twisted-pair type AAAC conductors.

3. Type T-2 designation is a trademark and its name usage should be restricted to its

present owner's or licensee's products. Other manufacturers have chosen various

other names for their products: ACSR/Duplex, AAAC/Duplex, and type VR

(Vibration-Resistant).

4. Required twisted-pair sag tension data for the ruling span and design criteria of the

line project are available from the conductor manufacturers. Sag-tension

characteristics should be similar to conventional, single ACSR and AAAC

conductors. The specified conductor tension limits may be affected by the design

recommendation on overhead groundwire (OHGW) sag (adequate midspan

separation is usually assured for standard RUS structures by keeping the OHGW's

initial sag at 60°F (16°C) unloaded condition, to 80 percent of the conductor's sag,

under the same condition).

5. Splices for component conductors are identical to splices currently included for

single ACSR and AAAC conductors. Other hardware and fittings designed or

adapted for the twisted-shape conductors, such as suspension clamps, are available.

Coordination of attachment design details with the hardware supplier and the

conductor manufacturer will assure satisfactory performance of conductor and

components.

6. Line construction of special conductor should provide specifications covering

method for its handling and installation, in accordance with the conductor

manufacturer's recommendations.

If you would like more information or have any questions, please call Bing C. Chan, Structural

Engineer, Transmission Branch, at (202) 720-0999.
Items of Engineering Interest

August 1996

7

USE OF STIRRUPS

During 1995, the Overhead Distribution Lines Subcommittee of the National Rural Electric

Cooperative Association's (NRECA) Transmission and Distribution (T&D) Engineering

Committee conducted a survey on the use of stirrups to make connections to distribution line

conductors. Five hundred and seventeen distribution cooperatives reported on their experience

with using stirrups by answering questions dealing with types of stirrups used, their applications

and failure rates. Several respondents provided additional comments which were very

informative.

Over 50 percent of the respondents use hot line clamps on stirrups to connect transformers,

cutouts, arresters, reclosers, regulators and capacitor banks to main lines. Over 60 percent use

this method to connect tap lines and over 25 percent use this method to connect main lines

together.

Summarized below is the approximate percentage of cooperatives that use the types of stirrups

identified in the questionnaire:

• 31 % -- Bail with two attached compression connectors

• 17 % -- Bail with two separate compression connectors

• 14 % -- Loop with a single hot line clamp

• 11 % -- Loop with two hot line clamps

• 15 % -- Loop with a single compression connection

Less than 10 percent of the cooperatives reported that they had failure rates of one to five

percent. Only four cooperatives reported that they had failures with more than five percent of

their installed stirrups. The remaining cooperatives reported failure rates of zero to less than one

percent.

Obviously, stirrups have a widespread use by distribution cooperatives. Several different types of

stirrups are being used, and the reported failure rates of connections with stirrups are very low.

The NRECA Overhead Distribution Lines Subcommittee and engineers at RUS analyzed the data

and comments of the survey and drew several more conclusions.

There is no universal preference for stirrup types or applications. Some respondents strongly

defended their preferences and denounced other types, whereas, just as many respondents made

similar remarks about another type of stirrup. The same opposing views were voiced about where

stirrups should and should not be used.

The primary purpose of the survey was to gather data regarding failure rates and problems with

stirrups. The final data shows that there were more failures caused by the connectors than by the

stirrups themselves by a ratio of approximately three to two. Some respondents blamed most
Items of Engineering Interest

August 1996

8

failures on poor workmanship or improper tool selection when installing compression type

connectors. The data and the comments also attribute the following causes for failures of stirrups

and hot line clamps.

• Used in an area of vibrating conductors.

• Used where the current (load) is too high.

• Stirrup material not large enough.

• Stirrup material is aluminum.

• All purpose (aluminum) clamps used with the stirrup.

Over the last several years, RUS has not received any negative reports nor any complaints

regarding connections using stirrups. In the survey, there was only one negative comment about

the general use of stirrups, whereas, there were several comments advocating their widespread

use. The data shows that if the proper size and material stirrups and hot line clamps are used, for

the proper application, and if they are properly installed, then their failure rate is expected to be

equal to or less than the other components of the distribution system.

Based on this survey’s results and many discussions with its borrowers, RUS is proceeding to

include the combined use of stirrups and hot line clamps in its standard drawings and

specifications for primary distribution lines. However, if and until RUS can properly

implement this change, the use of stirrups is only authorized on those systems which have

written approval by the appropriate RUS Regional Engineering Branch in Washington.

We anticipate that it will take several months to make this change.

Furthermore, the allowed use of stirrups will probably have the following conditions directed at

mitigating failures. These guidelines should be followed by all distribution cooperatives presently

using stirrups.

• Stirrups with two compression connectors are not to be used in areas of vibrating

conductors.

• The stirrup and hot line clamp shall be sized to meet or exceed the current carrying

capacity of the tap conductor or equipment jumper.

• All stirrup conductors shall be made of copper or bronze.

• All stirrup conductors shall be of #2 copper equivalent or larger.

• All-purpose or aluminum hot line clamps shall not be used with stirrups.

• Stirrups are not recommended to be used to connect reclosers, autotransformers or

line regulators.

• Stirrups are not to be used to connect main lines or heavily loaded tap lines.
Items of Engineering Interest

August 1996

9

• All stirrups, connectors and clamps shall be installed in accordance with the

manufacturer’s specifications.

Stirrups and hot line clamps should not be used for sectionalizing tap and especially main lines for

operational or maintenance purposes. RUS advocates permanent compression or bolted type

connectors be used because of their better current carrying capabilities and proven reliability.

RUS strongly recommends that line switches or fused or solid blade cutouts be used at line

locations where occasional line sectionalizing may be required.

At locations where permanent connections using compression or bolted type connectors are not

desired, the present RUS standards specify installing hot line clamps (over armor rods on

aluminum conductors). All connections, regardless of the types of connectors, stirrups or hot

line clamps to be used, need to be installed properly, carefully, and with the proper tools. All

conductors needs to be thoroughly cleaned with a wire brush before installing connectors or

clamps and a suitable inhibitor needs to be used before applying connectors over aluminum

conductor.

RUS thanks Jim Dedman of NRECA and Chairman Jim Byrne (Poudre Valley Electric

Cooperative, Ft. Collins, Colorado) and Lowell Wessel (Jackson County Rural Electric

Cooperative, Browntown, Indiana) of the NRECA Overhead Distribution Lines Subcommittee for

their excellent contributions in conducting and analyzing the recent stirrup survey.

If you would like more information or have any questions, please call James L. Bohlk, Electrical

Engineer, Distribution Branch at (202) 720-1967.

USE OF STANDOFF BRACKETS ON FULL ROUND CABLE RISER SHIELDS

Although we have included full round cable riser shields in the RUS List of Materials, we require

these shields, as well as riser conduits, to be mounted directly to the surface of the pole with no

standoff brackets. This will prevent climbing by unauthorized persons. We believe the RUS

required mounting method makes the installation comply with NESC Rule 217A1b and

Rule 217A2 regarding “climbing” and “steps”, respectively.

If you would like more information or have any questions, please call Trung Hiu, Electrical

Engineer, Distribution Branch, at (202) 720-1877.

GUY ATTACHMENTS

Guy attachments which use pole eye plates or guying tees with grid gains rely on the tightness of

their mounting on a wood pole to achieve full capacity. These guy attachments depend on the

grid teeth (or spurs) of the pole eye plate and the grid gains for the guying tee remaining in full

contact with the wood pole in order to distribute the shear loads to the pole and maintain the

stability of the connection. When first installed, the guy attachments are bolted tightly to the pole.
Items of Engineering Interest

August 1996

10

With a tight connection, the bolts are loaded primarily in tension, the shears are distributed from

the grid teeth to the wood pole, and there is little or no “pull away” at the top of the attachment.

As the wood pole dries out, the connection may become less tight. If the connection loosens, the

attachment will tend to “pull away” from the pole at the top bolt and “compress” the wood near

the bottom bolt. Moments will be induced into both bolts. The combined tension and moment in

the bolts will reduce the capacity of the guy connection.

Some borrowers may wish to make it a practice of tightening all guy attachments 2 or 3 years

after a new line is constructed. Guy connections should be periodically inspected for tightness

thereafter.

If you would like more information or have any questions, please call Donald G. Heald, Structural

Engineer, Transmission Branch, RUS, at (202) 720-9102 or Bubba McCall, Oglethorpe Power

Corporation, at (770) 270-7665.

GUY MARKERS

Guy Markers (guy guards) are used to make anchor guys conspicuous to the public in an effort to

help prevent accidental collision with the guy by a pedestrian or vehicle.

Previously, the Rural Utilities Service (RUS) required guy markers to be flame retardant. In

order to provide borrowers with greater flexibility in their choice of products, Technical

Standards Committee “A” is now considering applications for acceptance of plastic or fiberglass

guy markers that are not required to be fire retardant.

In the RUS List of Materials, these guy markers will be shown on either a separate page or in a

separate category on the same page.

Borrowers will have the option of selecting either type depending on the area in which it is to be

used. Non-flame retardant guy markers may be used in areas where the burning of ditches or crop

burning activities are not active.

If you would like additional information or have any questions, please contact George Keel,

Engineering Technician, Distribution Branch, at (202) 690-0551.

KEEP TESTING YOUR UNDERGROUND POWER CABLE

In previous Items of Engineering Interest, we have discussed testing of new underground cable.

The Underground Subcommittee of the NRECA’s T&D Engineering Committee highly

recommends that electric utility operators test underground cable they purchase. The

Subcommittee's recommendation is founded on results of independent cable testing of cable

samples conducted in 1993, 1994, and 1995. These samples were supplied by co-ops throughout

the United States and represent samples of all eight major U.S. suppliers of medium voltage cable.
Items of Engineering Interest

August 1996

11

The Subcommittee provided its testing results as an inducement to promote the independent

testing of newly purchased cable.

The Subcommittee recommends that the following tests be conducted at a minimum:

1. Dimensional analysis of all cable components;

2. Microscopic examination for voids, contaminants and protrusions; and

3. Insulation shield stripping test.

The Subcommittee also recommends that optional testing of Tree-Retardant Cross-Linked

Polyethylene and Cross-Linked Polyethylene insulated cables include a Hot Oil Test. The

Subcommittee does not recommend conductor shield and insulation shield resistivity tests because

they consistently test well below maximum specifications.

Subcommittee recommended typical sampling rates are to test one sample, each, from the first

and last reel on orders of 50,000 feet (15,240 meters) or less and one sample for each additional

50,000 feet of cable ordered.

The Subcommittee recommends that purchasers instruct manufacturers to cut samples and send

them to the selected testing laboratory, or the purchaser can cut the samples upon arrival of the

shipment. The Subcommittee further recommended that purchasers notify suppliers in advance

that cable testing will be conducted and purchasers should establish responsibilities and

procedures in case of a failure, such as: Any evidence of noncompliance with the enclosed

specifications shall be justification for:

1. Further testing at manufacturer's expense (each shipping reel);

2. Rejection of the tested reel and possibly the reels preceding and following in the

manufacturing process; and

3. Rejection of the entire order, depending on the severity and frequency of

noncompliance.

A partial list of possible independent testing laboratories provided by the Subcommittee includes:

Cable Technology Laboratories, Inc.

P.O. Box 708

690 Jersey Ave.

New Brunswick, NJ 08903

(201) 846-3220

Forster Electrical Engineering, Inc.

550 North Burr Oak Ave.

Oregon, WI 53575

(608) 835-9009
Items of Engineering Interest

August 1996

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NEETRAC

62 Lake Mirror Road, Building 3

Forest Park, GA 30050

(800) 762-6522

All of these laboratories participate in the Cable Acceptance Testing Program promoted by

NRECA’s T&D Underground Subcommittee. The inclusion of a laboratory in this list does not

imply endorsement by RUS. The testing laboratories listed above have voluntarily agreed to

collect electric cooperative test data and provide it to the NRECA Underground Subcommittee

annually for information and publication. To have your data included, note on your purchase

order "INCLUDE IN COOPERATIVE DATA FILE." Cooperative names will not be published

and participation is voluntary.

The following table summarize results of the 1995 testing (the 1993 and 1994 testing are

summarized in the 1995 Items of Engineering Interest):

1995 TEST RESULTS

CABLE TYPE TR-XLPE* EPR** TOTAL

INSULATION LEVEL 15 kV 25 kV 35 kV 15 kV 25 kV 35 kV

TOTAL TESTED 116 137 0 141 7 0 401

NUMBER FAILED

CONTAMINANTS 0 0 4 0 4

NUMBER FAILED

DIMENSIONAL 1 3 4 0 8

NUMBER FAILED

LOW STRIP TENSION 1 2 2 0 5

NUMBER FAILED

NEUTRALS TOUCHING, KINKED, OR

CORRODED 1 0 0 0 1

NUMBER FAILED

NEUTRAL

INDENTATION 0 0 2 0 2

PROTRUSIONS 0 3 0 0 3

NO EXTERNAL

MARKINGS 2 0 0 0 2

PERCENT FAILURES 4.3% 5.8% 8.5% 0.0% 6.2%

* Tree-Retardant Cross-Linked Polyethylene ** Ethylene Propylene Rubber

If you would like more information or have any questions, please call Trung Hiu, Electrical

Engineer, Distribution Branch, at (202) 720-1877.
Items of Engineering Interest

August 1996

13

ANSI STANDARD FOR TESTING HARDWARE

A proposed ANSI Standard for Testing of Transmission and Distribution Line Hardware

(C135.61) is in the final voting stages of IEEE. This standard will cover the requirements for

mechanically testing load rated line hardware for use on transmission and distribution facilities.

The standard will cover routine acceptance testing.

Hardware items which this standard specifically addresses, but is not limited to, are clevis and eye

fittings, socket fittings, ball fittings, chain links, shackles, triangular and rectangular yoke plates,

suspension clamps, and strain clamps.

The fact that a certain manufacturer’s hardware item has been accepted by RUS is not a guarantee

of production quality and that all production items will meet necessary strength tests. Many

manufacturers will have their own acceptance testing procedures used on production runs. This

standard defines routine acceptance tests and establishes a uniform standard which production

runs are to meet.

The standard is based on a defined acceptance quality level. Given a certain lot size, there will be

a minimum established sample size. Determination of acceptability will be based on the number of

samples failing to pass the tests.

Once this standard is approved, borrowers should consider referring to this standard in their

purchase orders of appropriate hardware. The standard requires all tests by the manufacturer to

be recorded in a permanent and organized manner and maintained for a minimum of 10 years.

Borrowers may want to consider asking for a copy of the test reports or for a summary report.

This standard could also be used by borrowers in performing their own routine tests of hardware.

If you would like more information or have any questions, please call Donald G. Heald, Structural

Engineer, Transmission Branch, at (202) 720-9102.

OPERATION

SAFETY SIGNS

In previous Items of Engineering Interest, we discussed the ANSI standards for environmental

and facility safety signs. These standards are intended to promote uniform national practice, and

include considerable changes from some past safety sign practices. As RUS underground

construction drawings and specifications are revised, we plan to delete standards for safety signs

and refer to the ANSI standards, which are:

• ANSI Z535.1 Safety Color Code

• ANSI Z535.2 Environmental and Facility Safety Signs
Items of Engineering Interest

August 1996

14

• ANSI Z535.3 Criteria for Safety Symbols

• ANSI Z535.4 Product Safety Signs and Labels

• ANSI Z535.5 Accident Prevention Tags (for Temporary Hazards)

These coordinated standards are intended to apply to every permanent or temporary safety sign or

tag on a utility system. These standards prescribe details for colors, shapes, and panel layout for

the three panels: (1) signal word panel, (2) message panel, and (3) pictorial panel. As stated in

previous Items of Engineering Interest, the appropriate ANSI signs for dead-front pad-mounted

equipment are a “Warning” sign on the exterior of the enclosure, and a “Danger” sign inside the

enclosure. We also discussed which sign might be appropriate under the ANSI standard for

substation fences. Although RUS has never stipulated which sign to use, we stated that we

thought the “Danger” sign was the best choice. It now appears that many people believe the

“Warning” sign better meets the ANSI criteria for substation fences, and that “Danger” signs

should be installed inside substations on structures that support live parts. This belief seemed to

be the prevailing opinion at the most recent NESC Technical Subcommittee meetings. We believe

that in the past most borrowers have used the “Danger” sign for substation fences with no

additional safety signs inside the substations. Practices under the ANSI standards are in progress

but not yet finalized and, thus, it would be inappropriate to make a specific recommendation at

this time. State regulatory agencies or insurance companies may have recommendations and

should be contacted.

If you would like more information or have any questions, please call Trung Hiu, Electrical

Engineer, Distribution Branch, at (202) 720-1877.

AUTOMATIC METER READING

Automatic meter reading (AMR) offers many advantages that electric cooperatives may want to

consider. Besides providing the ability to read meters remotely to improve billing and accounting

costs and accuracy of meter readings, an AMR system offers many attractive features such as

signal outage notification, remote reconnect/disconnect performance, meter tampering detection,

safety improvement, time-of-use (TOU) billing, new or complex rates, and load management

monitoring.

Electric cooperatives just getting started in AMR should consider the specifications of available

products and the performance features as well as regulatory and consumer issues. Factors to be

considered include whether a prospective AMR system can be used for both single-phase and

poly-phase metering and if it is compatible with both electronic and electromechanical meters,

including those already on the system. It is also important to know whether the system is equally

practical in both high density and low density load areas.

Industry surveys show that utilities may recover their AMR investment in about 10 years.

Usually, utilities offer customers “add-on” value features such as fire alarm, power outage alert,
Items of Engineering Interest

August 1996

15

home security, low temperature reporting, and medical alert to their customers in order to

facilitate the AMR conversion revenue recovery.

Some cooperatives have already installed AMR systems on a trial basis and have experienced

savings on operations costs, cash flow improvement, and otherwise found the benefits of an AMR

systems very positive. It allows more timely and accurate billing and better informed reaction to

customers’ inquiries. AMR systems with TOU features also allow customers the ability to make

more knowledgeable cost savings decisions regarding energy use. Of course, there are benefits

that customers can not see directly such as system performance improvement, decrease in future

rate increases, and faster response during power outages.

There are some disadvantages too. In addition to the high first cost for mass deployment, AMR

users should realize that once AMR is installed, they lock themselves into a single source of

supply. This could limit future choices for advanced applications such as demand side

management (DSM) and real time pricing (RTP). Also meters and related electronic equipment

need to be evaluated in accordance with the appropriate ANSI standards (C12 series).

Communications equipment may need to conform to the requirements of the Federal

Communications Commission (FCC).

If you would like more information or have any questions, please call Anh Mai, Electrical

Engineer, Distribution Branch, at (202) 720-1792.

INSPECTION & MAINTENANCE

POLE INSPECTION AND MAINTENANCE

RUS announces the issuance of RUS Bulletin 1730B-121, “Pole Inspection and Maintenance,”

dated April 15, 1996. The purpose of this bulletin is to provide RUS borrowers with information

and guidance for establishing and sustaining a continuing program of wood pole maintenance.

This guide bulletin supersedes REA Bulletin 161-4, “Pole Inspection and Maintenance,” published

October 1974. This bulletin recommends inspection intervals for standing wood poles and

contains current information on the three types of internal treatments, i.e., liquid internal

preservative, fumigants, and solids. Included in this bulletin are several tables to help determine

the remaining effective overload capacity factor (OCF) in poles that have experienced decay

damage.

If you would like more information or have any questions, please call H. Robert Lash, Chief,

Transmission Branch, at (202) 720-0486.
Items of Engineering Interest

August 1996

16

INSPECTION & MAINTENANCE FORM FOR PAD-MOUNTED EQUIPMENT

The NRECA T&D Underground Subcommittee has developed a sample “Inspection &

Maintenance Form for Pad-Mounted Equipment.” This form could prove to be quite useful and

augment borrowers’ operations and maintenance programs for reporting purposes. The form is

included as Appendix A. Any comments or feedback would be appreciated, and should be sent to

Mr. Hiu.

If you would like more information or have any questions, please call Trung Hiu, Electrical

Engineer, Distribution Branch, at (202) 720-1877. The form is available in electronic format from

Mr. Hiu.

SMD POWER FUSE UNIT BORE CLOSEDOWN

S&C Electric Company’s SMD power fuses include a solid material liner consisting of

compressed boric acid cakes which generate deionizing gases to effect circuit interruption. The

solid material liner is susceptible to damage from gross water entry, moderate amounts of water

entry combined with corona, and, in some fuse unit vintages, high temperatures. Analysis has

shown that such damage may involve deterioration of the boric acid cakes, followed by the

constriction of the fuse unit bore, i.e., fuse unit bore closedown. The extent and rate of bore

closedown depends on the amount of water that has entered the fuse unit. In the most severe

cases, the constriction may actually immobilize the fuse unit arcing rod and prevent proper

operation of the fuse.

Over the years, a number of fuse units returned to S&C for inspection have been found to exhibit

fuse unit bore closedown. Most such returned fuse units were severely damaged by the gross

entry of water. This can be prevented by following minimal storage and handling precautions, i.e.,

to store fuse units in a dry place and to avoid leaving fuse units hanging open in the mountings.

In a smaller number of cases, bore closedown occurred with relatively small amounts of water

inadvertently introduced into a fuse unit, such as might occur when a fuse unit is temporarily left

hanging open in a mounting during a rainstorm.

Design and Process Improvements

To minimize the susceptibility of fuse units to bore closedown, improved techniques were adopted

in the early 1970’s for the assembly of boric acid cakes. In 1985, numerous additional

refinements were implemented, including a new rain cap design for all SMD fuse units rated

69 kV and below, as well as for SMD-1A fuse units rated 115/138 kV.

The electrical mechanism for fuse unit bore closedown, as mentioned earlier, can involve corona

discharge within the fuse unit in the presence of excessive moisture. SMD-1A and SMD-2B Fuse

Units rated 115 kV and 138 kV were modified in the early 1960’s to include a semiconductive

coating on the inside (bore) surface of the solid material liner. This proved so effective that it has
Items of Engineering Interest

August 1996

17

also been applied to all 69 kV fuse units since 1985. Subsequently, as a precautionary measure,

34.5 kV and 46 kV fuse units have also been bore coated since 1992.

Inspection Procedures

S&C SMD-1A, SMD-2B, and SMD-2C fuse units can be tested in the field for bore closedown

using a technique called airflow testing. SMD-50 fuse units may be tested by means of X-ray

analysis and SMD-3 Fuse Units require complete fuse unit disassembly at S&C to inspect for bore

closedown. All three techniques are nondestructive to the fuse unit.

S&C recommends periodic airflow testing to values furnished with the S&C Airflow Test

Instrument which reflect the minimum bore diameter that is within tolerance.

Fuse units that may have experienced questionable storage in the past should have the condition

of the bore verified by airflow testing, X-ray analysis, or disassembly inspection at S&C. The

person to be contacted at S&C for any questions or problems concerning fuse bore closedown is

Roger Knopf, at (312) 338-1000, extension 2748.

If you would like more information or have any questions, please call Harvey L. Bowles, Chief,

Distribution Branch, at (202) 720-5082.

SIMPLIFIED REPLACEMENT GUIDE FOR MEDIUM VOLTAGE CABLE

As an ongoing effort to improve quality of service, the NRECA T&D Underground

Subcommittee has developed a “Simplified Replacement Guide for Medium Voltage Cable.”

This simplified guide is intended for electric utilities that do not have formal cable replacement

programs. There are many philosophies for cable replacement ranging from a points system for

rating cable and failures to a simplified approach of replacing cable after a certain number of

failures. There are two primary reasons for replacing medium voltage cable: (1) failure of the

cable insulation system and (2) severe damage to the concentric neutral wires via corrosion.

Mechanical failures resulting from installations and dig-ins should be handled on a case-by-case

basis and are not addressed in this guide.

The guide promotes maintaining an accurate system for reporting and tracking of primary cable

failures. A good tracking system will help in identifying problem cables by manufacturer, by year

of manufacture and of installation, by type, by location, etc. A sample reporting form is included

as Appendix B.

This replacement guide addresses three criteria to consider:

1) Neutral Corrosion. Neutral deterioration can occur anywhere in a span or run of cable

compromising the continuity of the neutral and may affect system operation and safety.
Items of Engineering Interest

August 1996

18

Presence of stray voltages may be an indication of corrosion problems, but the only positive way

to determine the extent of corrosion is to dig up sections of cable for inspection or have a

corrosion survey performed. Spot cable replacement for corroded neutral cable is usually not a

practical solution due to the sporadic nature of deterioration. The best solution is to replace

extremely deteriorated cable on a per span basis and schedule replacement of moderately

deteriorated spans for a later time. Whenever a primary cable is exposed because of a failure or a

dig-in, the neutral should be inspected. If there is extreme corrosion, the cable should be repaired

to restore power and the entire run scheduled for immediate replacement. The reporting form in

Appendix B includes a guide for estimating the condition of the concentric neutral.

2) Single-Phase Loop Feed Cable and Cable Feeding Noncritical Loads. This cable should be

replaced after two or three unexplained insulation failures. If there are other spans of the same

vintage (type, manufacturer and date) cable in the same loop that have failed, they should be

scheduled to be replaced also.

3) Three-Phase Cable, Radial Single-Phase and Critical Loads. When there is an unexplained

insulation failure of this cable, a sample of the cable should be sent to a laboratory for failure

analysis. A two foot (0.6 m) sample is preferred, but a smaller sample can be accommodated by

most labs. A longer sample will give a better indication of the cable’s condition. The

recommended tests to be performed on this failed cable are wafer analysis for analysis of voids,

contaminants, protrusions, and trees and a hot oil test of XLPE or HMWPE. Volume resistivity

tests are expensive and are not usually needed on failed cable. Cable strip tension tests are also

not usually needed unless there is an obvious lack of bonding between the insulation and the

shield. If there are trees larger than one half of the insulation thickness, the cable should be

replaced as soon as possible. If there are large numbers of smaller trees, the utility has to make a

decision on when the cable should be replaced. If there are large contaminants, many

contaminants, large protrusions or large voids in the insulation, the cable should be replaced as

soon as possible. Some cable labs will try to determine the remaining life of the cable, but that is

an inexact science at best.

The following labs participate in NRECA’s cable acceptance program:

Cable Technology Laboratories, Inc.

P.O. Box 708

690 Jersey Ave.

New Brunswick, NJ 08903

(201) 846-3220

Forster Electrical Engineering, Inc.

550 North Burr Oak Ave.

Oregon, WI 53575

(608) 835-9009
Items of Engineering Interest

August 1996

19

NEETRAC

62 Lake Mirror Road, Building 3

Forest Park, GA 30050

(404) 608-5104

All of these laboratories participate in the Cable Acceptance Testing Program promoted by

NRECA’s T&D Underground Subcommittee. The inclusion of a laboratory in this list does not

imply endorsement by RUS.

This guide was prepared by the NRECA T&D Underground Subcommittee. Any comments or

feedback would be appreciated, and should be sent to Mr. Hiu.

If you would like more information or have any questions, please call Trung Hiu, Electrical

Engineer, Distribution Branch, at (202) 720-1877. The guide is available in electronic format

from Mr. Hiu.

ENVIRONMENTAL MATTERS

RAPTOR ELECTROCUTIONS ON ELECTRIC UTILITY DISTRIBUTION

OVERHEAD STRUCTURES

A review of utility raptor electrocution forms filed with RUS since 1985 was presented at the

1996 Rural Electric Power Conference in Fort Worth, Texas. The paper presented by Richard

Harness of Electrical Systems Consultants, titled "RAPTOR ELECTROCUTIONS ON

ELECTRIC UTILITY DISTRIBUTION OVERHEAD STRUCTURES" indicates that overhead

distribution powerline poles configured with transformers and bare jumpers are associated with

the most raptor electrocutions. The paper indicates that although many utilities today are

employing larger crossarms in their new construction to provide increased phase-to-phase and

phase-to-ground separation to reduce the potential for electrocutions, uninsulated jumper wires

may pose a greater threat to raptors.

The paper reviews the type and frequency of overhead electric distribution pole-top units

associated with raptor electrocutions. Bird-of-Prey fatality data was collected from 51 electric

utilities located in Montana, Nebraska, New Mexico and Texas. Records were obtained from

41 RUS borrowers and 10 other municipal or investor-owned utilities, spanning the years 1986

through 1995. Most of the information base was obtained from a generic raptor electrocution

reporting form created and distributed by RUS in 1985. Additional records were obtained from

the United States Fish & Wildlife Service (USFWS) and through ads placed in wildlife and utility

trade journals.

A number of different raptor species were represented in the data. The birds covered a wide size

range, from small American kestrels (wingspan, 50 cm) to large bald eagles (wingspan, 2 m).

Listed in Table 1 is a breakdown of the number and type of species electrocuted.
Items of Engineering Interest

August 1996

20

TABLE 1

RAPTOR SPECIES TABULATION

SPECIES NUMBER SPECIES NUMBER

Hawk 78 Golden eagle 63

Red-tailed hawk 21 Bald eagle 9

Swainson's hawk 3 Eagle 6

Ferruginous hawk 2 EAGLE 78

Harris hawk 2 Owl 44

Rough-legged hawk 1 Great horned owl 32

Goshawk 1 Short-eared owl 1

Harrier 1 Western screech owl 3

Kestrel 4 Great Gray owl 2

Gyrfalcon 1 OWL 82

Prairie falcon 1 TURKEY VULTURE 15

HAWK 115 OSPREY 11

Because electric cooperatives use construction unit standards developed and published by RUS,

each electrocution record was assigned a specific standardized distribution pole-top construction

unit. Table 2 illustrates the association of raptor mortality by species group as it relates to RUS

distribution pole-top construction units.

TABLE 2

DISTRIBUTION LINE DATA - CONFIRMED AND SUSPECTED ELECTROCUTIONS

Total

Unknown Transformers Tangent Deadend Switch Recloser Riser Capacitor Ground No.

1-Phase 3-Phase & Tap Raptors

Eagles 5 11 27 21 7 0 1 2 2 2 78

Hawks 3 35 40 12 8 2 2 3 1 9 115

Owls 4 24 25 6 5 1 6 4 1 6 82

Vultures 1 5 5 0 0 0 1 0 1 2 15

Osprey 0 0 4 2 4 0 0 1 0 0 11

Total 13 75 101 41 24 3 10 10 5 19 301

Total Transformers 176 58.47% of all confirmed and suspected electrocutions were associated with transformers

Table 2 shows a strong correlation between both single and three-phase transformers and raptor

mortality. Transformers accounted for 58 percent of all confirmed and suspected electrocutions.
Items of Engineering Interest

August 1996

21

Although tangent structures proportionally killed more eagles than other raptor species, they still

only accounted for 27 percent of all eagle electrocutions. Transformers still killed the greatest

number of eagles, accounting for 49 percent of all reported and confirmed eagle electrocutions.

The correlation between both single and three-phase transformers and raptor mortality is

important not only because transformers account for the greatest percentage of electrocutions, but

because the percentage of poles on rural electric systems with transformers is relatively low

(between 13 and 24 percent of all pole structures).

Further review of transformer caused electrocutions reveals that three-phase transformers account

for 57 percent of all transformer deaths. This is significant because three-phase transformer banks

are showing higher mortality rates than single-phase transformers even though the number of

three-phase banks in rural areas would typically be much lower. The paper estimates that less than

21 percent of all rural electric systems require three-phase transformer banks. Since transformers

should only comprise between 13 and 24 percent of all pole structures and less than 21 percent of

these should be three-phase units, multi-phase transformer banks are particularly lethal to raptors

since they are still associated with 57 percent of all transformer electrocutions.

Three-phase transformer banks are potentially lethal to raptors because of minimal phase-to-phase

and phase-to-ground separation between bare energized jumper wires connecting transformers,

protective cutouts and surge arresters. Rural multi-phase transformer banks often serve remote

irrigation or oil pumps and may be particularly harmful because they are situated near open

agricultural fields likely to support numerous raptors. Additional factors such as habitat type,

prey availability, raptor behavior, species, sex, age, and size may also contribute to the frequency

of rural three-phase transformer electrocutions.

Fortunately, transformer units can be raptor-proofed without making structural changes. The

amount of exposed energized hardware can be dramatically reduced on new transformer

installations by using 600 volt insulated jumper wire and installing insulated bushing covers.

Existing transformer units can be retrofitted by either replacing bare wire with 600 volt insulated

jumpers or by sliding insulating material over bare jumpers. Several utility manufacturers produce

insulating material constructed with an open seam, allowing it to be easily slipped over existing

bare conductors. Because the insulating material and bushing covers are relatively inexpensive

and easy to install, this option is also economically attractive compared to increasing separation

between conductors.

Although it may be appropriate to utilize increased phase separation in remote areas with high

golden eagle populations, the mortality data presented in this paper indicates that an emphasis on

providing insulated jumpers on all electrical equipment and at tap and deadend locations should

provide more protection for all raptor species, including eagles, at less cost to the utility.

If you would like more information or have any questions, please call Dennis Rankin,

Environmental Protection Specialist, Engineering and Environmental Staff, RUS, at

(202) 720-1953, or Richard Harness, Electrical Systems Consultants, Inc., at (970) 224-9100.
Items of Engineering Interest

August 1996

22

INSULATED DISTRIBUTION TRANSFORMER COVERS

Raptor electrocution continues to be one of the major concerns of the U.S. Fish and Wildlife

Service and state wildlife agencies. Based on electrocution data collected by RUS, transformer

poles appear to be associated with the majority of raptor electrocutions.

Some reputable transformer manufacturers have informed the Electric Staff Division that they sell

pole-type distribution transformers with a protective insulated cover rated at 15 kV dielectric

strength. The additional cost for this feature ranges from $5 to $8.

Since RUS has not received any testing criteria nor test results, we cannot attest to the accuracy

nor durability of the cover insulation. The quoted insulation values may deteriorate over time due

to exposure to ultraviolet light, contamination, and other aging factors. However, insulated

covers on pole-type distribution transformers will help to mitigate the electrocution of raptors and

small animals on the top of transformers. If your system is experiencing problems due to raptor

or small animal electrocutions, you might consider purchasing pole-type distribution transformers

with insulated covers. You do not need any special approval from RUS to buy transformers with

this feature if the basic transformer is RUS accepted (i.e., included in the RUS List of Materials.)

If you have any experience with transformers with insulated covers or if you would like more

information or have any questions, please call Dennis Rankin, Environmental Protection

Specialist, Engineering and Environmental Staff, at (202) 720-1953.

CONTROL OF SULFUR HEXAFLUORIDE (SF6) EMISSIONS

Sulfur hexafluoride (SF6) serves as a common dielectric in circuit breakers and as an insulator in

many other types of electrical power equipment. According to Ko et al. (1993), the major use of

SF6 worldwide is in electrical transmission and distribution systems. SF6 has been identified by

the Intergovernmental Panel on Climate Change as a potent greenhouse gas (1995). The

atmospheric lifetime for SF6 is estimated to be 3,200 years with a global warming potential for a

100-year time horizon of 24,900. Studies report the atmospheric concentration of SF6 to be low

but estimate its rate of increase to be approximately 7 to 8 percent per year (Rinsland, 1991;

Maiss, 1994). Due to the extreme length of time required to remove the gas from the

atmosphere, emissions will likely accumulate. Thus, there is good reason to control the release of

SF6.

To reduce emissions of SF6 from electrical transmission and distribution systems, the United

States Environmental Protection Agency (EPA) is developing a voluntary partnership with the

industry. Such a program presents a new and innovative way to achieve environmental

protection. For electrical power systems, opportunities exist to reduce emissions. EPA

encourages better maintenance of equipment, capture and recycling of the gas, consideration of

opportunities for substituting environmentally benign chemicals for SF6, and perhaps replacement

of older, leaking equipment.
Items of Engineering Interest

August 1996

23

Voluntary partnerships will be sought with individual utilities. EPA is interested in working with

interested parties in the industry to develop the format of the voluntary program. EPA invites

utilities to join in investigating options for reduction of emissions of the greenhouse gas SF6.

If you would like more information or have any questions, please call Harvey L. Bowles, Chief,

Distribution Branch at (202) 720-5082, or Elizabeth Dutrow, U.S. Environmental Protection

Agency, (202) 233-9061.

Intergovernmental Panel on Climate Change. Climate Change 1994, Radiative Forcing of Climate

Change. The Press Syndicate of the University of Cambridge. New York, New York. 1995.

Ko, Malcolm, et al. “Atmospheric Sulfur Hexafluoride: Sources, Sinks and Greenhouse

Warming”. Journal of Geophysical Research. Volume 98. Number D6. pp. 10,499-10,507.

June 20, 1993.

Maiss, M. and I. Levin. “Global Increase of SF6 Observed in the Atmosphere.” Geophysical

Research Letters. Volume 21. Number 7. pp. 569-572. April 1, 1994.

Rinsland, C. P., et al. “ATMOS/ATLAS 1 Measurements of Sulfur Hexafluoride (SF6) in the

Lower Stratosphere and Upper Troposphere.” Journal of Geophysical Research. Volume 98.

Number D11. pp. 20,491-20,494. November 20, 1993.

ADMINISTRATIVE

RECENT RUS ENGINEERING PUBLICATIONS

RUS has published several items recently of interest to the RUS electric engineering community.

These publications include:

• Bulletin 1726-601, “Electric System Construction Policies and Procedures --

Interpretations” (5/10/96). This bulletin, mostly in a question and answer format,

provides clarifications and interpretations concerning some of the policies and

procedures in 7 CFR 1726 relevant to RUS electric borrowers when purchasing

materials and equipment, and when constructing facilities by contract or force

account.

• Bulletin 1730B-121, “Pole Inspection and Maintenance” (4/15/96). This bulletin

provides information and guidance to RUS electric borrowers in establishing or

sustaining a continuing program of effective, ongoing pole maintenance.

If you need any of these publications, please contact RUS' Program Support and Regulatory

Analysis Staff at (202) 720-8674.
Items of Engineering Interest

August 1996

24

TRANSMISSION AND DISTRIBUTION ENGINEERING COMMITTEE

In 1991, NRECA established its Transmission and Distribution Engineering Committee to work

with REA (now RUS) in the development and maintenance of electric transmission and

distribution standards and specifications, and the exchange of engineering information of mutual

interest to rural electric utilities. The Committee is composed of some of the most dedicated and

talented individuals from NRECA and from electric cooperatives all across the United States.

These individuals routinely donate several weekends and considerable amounts of other personal

time each year to fulfill their commitments to the Committee.

We want to use this opportunity to thank these individuals and the organizations that sponsor

their participation.

The following list includes Committee members as of August 1996:

NRECA TRANSMISSION & DISTRIBUTION ENGINEERING COMMITTEE

MEMBER ORGANIZATION LOCATION

Committee Chairman

 Jim Baker Middle Tennessee EMC Murfreesboro, TN

NRECA Staff Coordinator

 Jim Dedman NRECA Arlington, Virginia

Craig Anderson Dairyland Power Co-op LaCrosse, WI

Dominic Ballard East Kentucky Power Co-op Winchester, KY

David Beam North Carolina EMC Raleigh, NC

Alan Blackmon Blue Ridge EC Pickens, SC

Gregory Broussard Jackson EMC Jefferson, GA

James Byrne Poudre Valley REA Fort Collins, CO

Jim Carter NRECA - WQC Spartanburg, SC

James Crouch Fairfield EC Winnsboro, SC

Russ Dantzier Mid-Carolina EC Lexington, SC

Berl Davis Palmetto EC Hilton Head, SC

Bruce Dreyer Middle Tennessee EMC Murfreesboro, TN

Carl Garner Middle Tennessee EMC Murfreesboro, TN

David Garrison East Central Oklahoma EC Okmulgee, OK

David Gebhardt LaPlata EA Durango, CO

Ron Gunnell Randolph EMC Asheboro, NC

Jack Heflin Western Farmers EC Anadarko, OK

Wayne Henson East Mississippi EPA Meridian, MS
Items of Engineering Interest

August 1996

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MEMBER ORGANIZATION LOCATION

Vince Heuser Nolin RECC Elizabethtown, KY

Robert Johnson Arkansas EC Corp. Little Rock, AR

Joseph Joplin Rutherford EMC Forest City, NC

Kendrick Kirschenmann Rushmore EPC Rapid City, SD

Russell Lea Clay EC Keystone Heights, FL

Gregory Lindsly Dixie EMC Baton Rouge, LA

Troy Little Four County EPA Columbus, MS

Charles Lukkarila United Power Assn. Elk River, MN

Charles (Bubba) McCall Oglethorpe Power Corp. Tucker, GA

David Moore Johnson County EC Cleburn, TX

William Murray Berkeley EC Moncks Corner, SC

Jim Newberg Missoula EC, Inc. Missoula, MT

David Obenshain Piedmont EMC Hillsborough, NC

Bob Oldham Southern Maryland EC Hughesville, MD

Mike Opitz Western Farmers EC Anadarko, OK

Michael Pehosh Ozarks EC Fayetteville, AR

Chris Perry Nolin RECC Elizabethtown, KY

Peter Platz Coast Electric Power Bay St. Louis, MS

John Rodgers Nodak EC, Inc. Grand Forks, ND

Paul Rupard East Kentucky Power Co-op Winchester, KY

Brad Schmidt Cass County EC Fargo, ND

Stephen Shirey Allegheny EC Harrisburg, PA

Robert Siekas Cherryland EC Grawn, MI

Gordon Sloan Sulphur Springs Valley EC Willcox, AZ

Thomas Slusher Union EMC Monroe, NC

Michael Smith Singing River Electric Co-op Lucedale, MS

Paul Spears Tri-County Electric Co-op Azle, TX

Gary Stein Wabash Valley Power Assn. Indianapolis, IN

Blaine Strampe Federated REA Jackson, MN

Tom Suggs Natchez Trace EPA Houston, MS

John Twitty Alabama EC Andalusia, AL

Scott Wehler Adams EC Gettysburg, PA

Lowell Wessel Jackson County REC Browntown, IN

Kenneth Winder Moon Lake Electric Roosevelt, UT
THIS PAGE IS

INTENTIONALLY

BLANK
Items of Engineering Interest

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APPENDIX A

INSPECTION & MAINTENANCE FORM FOR PAD-MOUNTED EQUIPMENT

LOCATION:_________________________________________ MANUFACTURER.....__________________________________

MAP ID........__________________________________________ SERIAL NO.................__________________________________

TYPE OF EQUIPMENT [ ] TRANSFORMER............................KVA .......... PHASES 1 3____

 [ ] JUNCTION CABINET...................[ ] 3 PHASE................[ ] V PHASE...............[ ] 1 PHASE

 [ ] SWITCHGEAR...............................MODEL 3 4 5 6 9 10 11 13 OTHER 

 [ ] OTHER-SPECIFY____________________

EXTERIOR MARKING “WARNING” DECAL....[ ] NEED TO REPLACE OR ADD..[ ] REPLACED OR ADDED..[ ] OK

 LOCATION NUMBER..[ ] NEED TO REPLACE OR ADD..[ ] REPLACED OR ADDED..[ ] OK

 OTHER-SPECIFY____________________ [ ] NEED TO REPLACE OR ADD..[ ] REPLACED OR ADDED..[ ] OK

FOUNDATION: TYPE...[ ] BOX PAD..........[ ] FLAT POLY PAD........[ ] CONCRETE PAD

 CONDITION.....[ ] NEED TO REPAIR OR REPLACE..............[ ] REPAIRED...........[ ] REPLACED..........[ ] OK

 GRADE.....[ ] NEED TO RAISE OR LEVEL.......................[ ] RAISED.................[ ] LEVELED.............[ ] OK

EXTERIOR FINISH........[ ] FADING -NO CORROSION.................[ ] NEEDS PAINTING..........[ ] PAINTED..........[ ] OK

 [ ] CORRODING.........................................[ ] NEEDS REPAIR...............[ ] REPAIRED

 [ ] CORRODING-BEYOND REPAIR......[ ] NEEDS REPLACING......[ ] REPLACED

OIL FILLED EQUIPMENT.......[ ] MINOR LEAK.....[ ] NEEDS REPAIR.....[ ] REPAIRED.....[ ] REPLACED.....[ ] OK

 [ ] MAJOR LEAK - MUST BE REPAIRED OR REPLACED IMMEDIATELY

EQUIPMENT SECURITY: ITEMS NOT CHECKED AS “YES”, MUST BE REPAIRED OR REPLACED IMMEDIATELY

 SECURED TO FOUNDATION.........................................[ ] REPAIRED.........................[ ] REPLACED.........................[ ] YES

 PENTAHEAD BOLT PRESENT AND SECURED........[ ] REPAIRED.........................[ ] REPLACED.........................[ ] YES

 HASP AND PAD OR OTHER LOCK INSTALLED.... .[ ] REPAIRED.........................[ ] REPLACED.........................[ ] YES

INTERIOR MARKING... ”DANGER” DECAL...[ ] NEED TO REPLACE OR ADD...[ ] REPLACED OR ADDED...[ ] OK

 CABLE LABELS....[ ] NEED TO REPLACE OR ADD...[ ] REPLACED OR ADDED...[ ] OK

INTERIOR FINISH.........[ ] FADING - NO CORROSION................[ ] NEEDS PAINTING..........[ ] PAINTED..........[ ] OK

 [ ] CORRODING..........................................[ ] NEEDS REPAIR...............[ ] REPAIRED

 [ ] CORRODING-BEYOND REPAIR......[ ] NEEDS REPLACING......[ ] REPLACED

TERMINATIONS............ELBOWS.............__________ NEEDS REPLACING__________ REPLACED__________ OK_____

 (ENTER POTHEADS.......__________ NEEDS REPLACING__________ REPLACED__________ OK_____

 QUANTITIES) SECONDARY....__________ NEEDS REPLACING__________ REPLACED__________ OK_____

GROUNDS..........ROD-MEASURED OHMS_____[ ] NEED TO REPLACE OR ADD..[ ] REPLACED OR ADDED..[ ] OK

 CONNECTIONS:..........................[ ] NEED REPAIR..............................[ ] REPAIRED..........................[ ] OK

SURGE ARRESTERS....EXISTING.........................[ ] NEED TO REPLACE OR ADD..[ ] REPLACED OR ADDED..[ ] OK

 CONNECTIONS:............[ ] NEED REPAIR...............................[ ] REPAIRED..........................[ ] OK

FAULT INDICATORS.....[ ] TESTED..................[ ] NEED TO REPLACE OR ADD...[ ] REPLACED OR ADDED..[ ] OK

INSECT NESTS....[ ] NEEDS TREATING...[ ] TREATED/REMOVED-DO NOT REMOVE FIREANT NESTS...[ ] NONE

LIST ANY OBSTRUCTIONS: ______________________________________________________________________

(FENCES; TREES; SHRUBS; BUILDINGS; ETC.)

PLEASE NOTE ANY OTHER PROBLEMS, ACTION TAKEN OR NEEDED: _______________________________________

_________________________________________________________________________________________________________

(USE OTHER SIDE IF ADDITIONAL SPACE IS NEEDED)

INSPECTED BY: DATE: 

ANY HAZARDOUS SITUATIONS, SAFETY VIOLATIONS OR MAJOR OIL LEAKS

MUST BE REPORTED AND REPAIRED IMMEDIATELY!
Items of Engineering Interest

August 1996

28

APPENDIX B

UNDERGROUND CABLE FAILURE REPORT

Cooperative: Date Truck/Crew: 

Location Underground Outage # 

∗∗∗ Circle Appropriate Answer∗∗∗

 Oper.

Conductor Type Metal Manufacturer Insulation Size Volts

 #2 Solid Copper Alcoa HMW 175 5kV

 1/0 Strand Aluminum Cablec TR-HMW 220 15kV

 4/0 Filled Strand CPI XLPE 260 25kV

 250 Essex TR-XLPE 320 35kV

 350 GE EPR 345

 500 Hendrix 

 750 Kaiser

 Kerite

Okonite

 Pirelli

Reynolds

 Rome

Southwire

 General

 Phelps-Dodge

 ___________

Jacket Neutral Condition Year Manufactured 

None Tinned Cu. Like new 25% gone Year Installed 

Semi-con Bare Cu. Green 50% gone Direct buried or duct (type )

Insulated Flat Strap Red 75% gone Plowed or trenched

Ridgelock Red & pitting 100% gone Main Line or Service Tap

# of wires Red & deep pitting Number of phases: 1 2 3

Severed strands Phase designation: A B C

Are Anodes Installed? Yes No

Year Anodes Installed 

Are Fault Indicators Installed? Yes No

Did they work properly? Yes No

Are MOV's installed? Yes No

What is the cable depth? in.

Comments:____________________________________________________________________________

 ____________________________________________________________________________
Items of Engineering Interest

August 1996

29

APPENDIX C

RURAL UTILITIES SERVICE

ELECTRIC STAFF DIVISION

Office of the Director

George J. Bagnall Director

(202) 720-1900 gbagnall@rus.usda.gov

Margaret A. Reason Secretary

(202) 720-1900 preason@rus.usda.gov

Fred J. Gatchell Deputy Director

(202) 720-1398 fgatchel@rus.usda.gov

Harvey L. Bowles Acting Chair, Technical

Standards Committee “A”

(202) 720-0980 hbowles@rus.usda.gov

Michelle Lew Secretary

(202) 720-0980 mlew@rus.usda.gov

Robin L. Meigel Financial Analyst

(202) 720-9452 rmeigel@rus.usda.gov

William Procopiow Architect

(202) 720-9090

Energy Forecasting Branch

Georg A. Shultz Chief

(202) 720-1920 gshultz@rus.usda.gov

Lisa Johnson Secretary

(202) 720-1920 ljohnson@rus.usda.gov

Sharon Ashurst Public Utility Specialist

(202) 720-1925 sashurst@rus.usda.gov

Christopher L. Tuttle Economist

(202) 205-3655 ctuttle@rus.usda.gov

Distribution Branch

Harvey L. Bowles Chief

(202) 720-5082 hbowles@rus.usda.gov

Anjunette A. Lyles Secretary

(202) 720-5082 alyles@rus.usda.gov

James L. Bohlk Electrical Engineer

(202) 720-1967 jbohlk@rus.usda.gov

Trung V. Hiu Electrical Engineer

(202) 720-1877 thiu@rus.usda.gov

George L. Keel Engineering Technician

(202) 690-0551 gkeel@rus.usda.gov

Anh T. Mai Electrical Engineer

(202) 720-1792 amai@rus.usda.gov

Transmission Branch

H. Robert Lash Chief

(202) 720-0486 blash@rus.usda.gov

Virginia S. Jenkins Secretary

(202) 720-0486 gjenkins@rus.usda.gov

Bing C. Chan Structural Engineer

(202) 720-0999 bchan@rus.usda.gov

Donald G. Heald Structural Engineer

(202) 720-9102 dheald@rus.usda.gov

Adrias M. Crowder Engineering Technician

(202) 720-9098 acrowder@rus.usda.gov