:File With REA:

:Bulletin 345-78:

UNITED STATES DEPARTMENT OF AGRICULTURE

Rural Electrification Administration

July l, 1980

Delay in Effective Date of REA Specification PE-78

Assistant Administrator - Telephone

SUBJECT: REA Specification for Carbon Arrester 

Assemblies for Use in Protectors, PE-78 

REA is delaying the effective date of P , E-78 from May 2, 1980, until 

December 31, 1980. When PE-78 was initially issued, all major impacted 

manufacturers informally indicated their ability to comply by the 

original May 2, 1980, effective date. Since then, circumstances have 

prevented all from qualifying. As a result there is presently no 

listed source of these devices from whom REA borrowers may purchase 

these products. Deferring the effective date will provide immediate 

relief from the nonavailability of listed arresters and will provide 

additional time for manufacturers to qualify to the new specification. 

Incorporated by reference in 7 CFR Part 1755.97
BLANK PAGE
UNITED STATES DEPARTMENT OF AGRICULTURE

Rural Electrification Administration

February 4, 1980

Supersedes 2/16/78

REA BULLETIN 345-78

SUBJECT: REA Specification for Carbon Arrester

Assemblies for Use in Protectors

I. Purpose: To announce the issuance of revised REA Specification

PE-78.

II. General: REA Specification PE-78 has been revised to clarify the

items which are covered by PE-78 as well as to revise some test

procedures to eliminate ambiguous data.

This specification becomes effective on May 2, 1980. All carbon

arrester assemblies bid or ordered by REA telephone borrowers

after that date shall comply with this specification. This does

not preclude the adoption of its requirements by manufacturers

prior to the effective date.

III. Availability of Specifications: Copies of the revised PE-78 will

be furnished by REA upon request. Questions concerning this specification may be referred to the Chief, Outside Plant Branch, Telephone Operations and Standards Division, Rural Electrification

Administration, U.S. Department of Agriculture, Washington, D.C.

20250, telephone (202) 447-3827.

Assistant Administrator - Telephone

Index:

SPECIFICATIONS:

Carbon Arrester Assemblies
BLANK PAGE
REA BULLETIN 345-78

PE-78

SEPTEMBER l979

SPECIFICATION FOR

CARBON ARRESTER ASSEMBLIES

FOR USE IN PROTECTORS

RURAL ELECTRIFICATION ADMINISTRATION-U.S. DEPARTMENT OF AGRICULTURE
REA Specification for

CARBON ARRESTER ASSEMBLIES FOR USE IN PROTECTORS

1. GENERAL

2. REQUIREMENTS

3. TEST POOCEDURES

4. MANUFACTURING QUALITY CONTROL

Figures 1 - 4
UNITED STATES DEPARTMENT OF AGRICULTURE

Rural Electrification Administration

REA SPECIFICATION FOR CAREBON

ARRESTER ASSEMBLIES FOR USE IN PROTECTORS

1. GENERAL

1.1 This document specifies REA requirements for carbon electrode,

air gap arrester assemblies for use in protectors. Each arrester

assembly consists of the combination of a mounting device with one or

more carbon arresters providing a gap in air at atmospheric pressure.

The arrester assembly must be installed in a protector, such as a

station protector, for use by an operating telephone company.

1.2 Impulse waveshape and arrester striking nomenclature are defined

in Figures 1 and 2.

1.21 The breakdown voltage of an arrester, for the purpose of this

specification, is defined as the value of potential which must

be applied to change the gap from a nonconducting to a conducting

condition.

1.22 A conducting condition for the purpose of this specification is

defined as that condition where current is discharged through

the arrester and the voltage drop across the arrester does not exceed

50 volts.

1.3 The characteristics of some arresters are, due to electrode

configuration, sensitive to polarity of the applied voltage.

Arresters in use on actual circuits may face surges of either polarity,

therefore, all impulse tests shall include both polarities.

1.4 Requirements as stated herein must be met by routine factory

production. By submitting data in accordance with this specification, the manufacturer so certifies. It is also the manufacturer's

duty to assure that production continues to comply with these minimum

standards.

1.5 All tests included in this specification shall be made with

arresters configured as intended for use in the field. If two

or more radically different mounting techniques are used, data shall

be submitted showing compliance for each type of mounting.

1.6 For the purpose of this specification, failure modes shall be

defined as follows:

 
- 2 -

1.61 Short Circuit Failure Mode: An arrester is considered to have

failed by the short circuit mode when a current of more than

.6 milliampere is measured in a circuit consisting of the arrester, a

100,000 ohm resistor, a milliammeter and a 100V (dc) source. Any

momentary or intermittent readings of .6 milliampere or greater shall

be considered as failure to meet this requirement.

1.62 Low Breakdown Failure Mode: In this mode, an arrester shall

have a dc breakdown of less than 180V on a voltage ramp rising

at not greater than 1kV/second.

1.63 High Breakdown Failure Mode: In this mode, an arrester shall have

an impulse breakdown in excess of the +3σ 100 V/μs values in

Table B.

2. REQUIREMENTS

2.1 DC Breakdown Voltage: The mean dc breakdown voltage and the -3σ dc

breakdown voltage of arresters shall be greater than those shown in

Table A, when measured in accordance with paragraph 3.1. Color coding

shall be as shown in Table A.

Table A – Minimum DC Breakdown Requirements

Primary Use Color Mean Vdc Breakdown -3σ dc Breakdown

Station or MDF Protection White 300 200

Plastic Cable Protection Yellow 700 510

2.2 Impulse Breakdown Voltage: The mean and +3σ surge breakdown voltages

of arrester, when measured in accordance with paragraph 3.1, shall

be less than or equal to the values in Table B.

Table B – Minimum Surge Breakdown Requirements

Primary Use Mean 100 V/μs +3σ Mean 10 kV/μs +3σ

Station or MDF Protection 750 1000 1000 1200

Cable Protection 1000 1500 1200 1600

2.3 60 Hz Current Carrying Ability: When tested in accordance with

paragraph 3.2, 80 percent of the asemblies tested shall not fail

by any mode on currents up to 30 amperes nor shall any become a fire

hazard at any level of current at which it is tested.

2.4 Failure Mode for Protection of Personnel: When the device is to be

used in situations where protection of persons against electrical
- 3 -

shock is the primary concern, such as in station protectors or MDF

protectors, either the arrester assembly or protector shall be designed

for ultimate failure exclusively in the short circuited mode before the

unit becomes a fire hazard. In this mode of failure, the unit shall

become permanently short circuited, and shall have an impedance of not

more than one ohm (1Ω) across the arrester/protector assembly. Tests

shall be continued on units which fail by the low breakdown mode until

a short circuit or high breakdown failure is encountered or until the

unit becomes a fire hazard.

2.5 Surge Life: When tested in accordance with paragraph 3.3,

arresters shall have an average life of 25 surges.

3. TEST PROCEDURES

3.1 Breakdown

3.11 After the air gap is installed in the test set, and prior to

initiation of the breakdown test, each sample shall be "cleared"

for up to 1 second by application of 180V dc in series with a 115V,

seven watt light bulb. Arresters which are shorted at the end of the

one second application (as indicated by a sustained glow of the lamp)

shall be replaced and the clearing process shall be repeated on the new

arrester.

3.12 The dc breakdown of an arrester shall be obtained by applying a

slowly rising (≤ 1000 volts per second) potential with a 20 ampere

crest current. See Figure 3 for a proposed circuit. Data shall be submitted by protector suppliers giving the mean initial dc breakdown, with

plus or minus tolerances for 1, 2, and 3 sigma, for both polarities of

applied voltage.

3.13 Arrester impulse breakdown data shall be submitted giving the

average breakdown on a rising wave front, with plus tolerances

for 1, 2, and 3 sigma for voltage surges rising at rates of 200 V/μs.

Crest current on this test shall be 20 amperes.

3.2 60 Hz Current Carrying Ability

3.21 The 60 Hz current carrying ability of the unit shall be determined

by subjecting samples to 60 Hz current for 11 cycles in increasing

amounts. Samples of the test group shall be tested in rotation to minimize heating effects. Data shall be submitted to show values of (single

11 cycle short) 60 Hz at which the arresters fail as well as failure

modes.

3.3 Impulse Life

3.31 At least fifty (50) samples shall be tested as described herein,

half with each polarity of surge. They shall meet the requirements of paragraph 2.5.
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3.32 Preparation and mounting of samples shall be as follows:

3.321 Test set mountings shall position arresters as in normal

service.

3.322 Test set mountings shall be clean and free from residue which

may influence test results.

3.323 The impulse discharge current and waveshape shall be calibrated

with an arrester in the circuit to assure that breakdown does

not cause waveshape or crest current to depart from the values specified.

3.324 After samples are installed in the test set, and prior to

initiation of the life test, each sample shall be "cleared” for

up to one second by the application of 180V dc in series with a seven

watt light bulb. Arresters which are still shorted at the end of the

one second application (as indicated by a sustained glow of the lamp)

shall be replaced, and the clearing process shall be repeated on the new

arrester. No further clearing shall be permitted after life testing

begins.

3.33 The sequence and timing for tests shall be as follows:

3.331 A 500A surge, as described in paragraph 3.342 shall be applied

to the sample under test.

3.332 There shall be a time delay of one to two seconds during which

no voltage is applied to the sample.

3.333 The samples shall be tested for short circuit failure as

described in paragraph 3.343.

3.334 There shall be another time delay of one to two seconds during

which no voltage is applied to the sample.

3.335 The sample's dc breakdown shall be measured as described in

paragraph 3.344.

3.336 Having completed the above tests on a sample the test set shall

step to the next sample. An interval of one to two minutes

shall exist between repeated test sequences on any one sample.

3.337 The surge on which a unit is first detected to have failed shall

be the last surge credited to the device. (e.g., A unit failing

on the first 500A surge would be credited with a life of one surge.)

3.34 Test procedures shall be as follows:

3.341 The polarity of the 500A surge, insulation resistance test, and

dc breakdown test shall be the same.
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3.342 500A Surge: A parallel loaded surge circuit, as detailed in

Figure 4, shall be used to subject the sample under test to a

peak 500 ± 5 percent surge on a 0 - 20 X 950 - 1050 μs waveshape.

The Virtual peak shall be used in defining the waveshape.

3.343 Short Circuit Failure: A dc power supply with a range of 0 to

1000V in series with a 100 kilohm resistor shall be connected

to the sample while the voltage is set at 0. Voltage across the sample

shall be increased from 0 to 100V in 1 millisecond ± 10 percent, and be

maintained at this value for 150 ms minimum. When the current flow is

integrated over the period between 50 and 150 ms, it shall yield a

current X time product less than 9 μA-s for the unit to be considered

to have survived.

3.344 DC Breakdown: A voltage ramp rising at not more than 5kV/s

shall be used to charge a 0.5 μF capacitor which is placed in

series with a 1000 ohm resistor and the test specimen. One breakdown

of the sample shall be performed, and the value shall be within the

tolerances of paragraph 1.6, except that the +3σ voltage limit for

100V/μs impulse breakdown shall be defined as the high breakdown limit

for this test.

3.35 Submit data on the average number of surges required for gap

failure, as well as data on all failure modes encountered. No

arrester assembly shall be credited with more than 100 surges.

4. MANUFACTURING QUALITY CONTROL

4.1 Manufacturers are expected to provide testing procedures to assure

that all carbon block arrester assemblies produced, which qualify

as meeting the requirements of this specification, comply with the

requirements.

4.11 This will require 100 percent production tests on all units. As

a minimum, production tests shall include checks of dc breakdown

levels and surge breakdown tests. The surge breakdown shall be as shown

in Table B.

4.2 Once every other year, on the anniversary date of the original

acceptance by REA, complete requalification data will be submitted

to REA by the manufacturer. While a data base as large as for the

original qualification is not required, data must be submitted on all

tests contained herein.
- 6 -

TIME

FIGURE 1: SURGE WAVESHAPE NOMENCLATURE

 

A Maximum, or crest, current or voltage

Tr Rise Time

Thy Time to 1/2 crest value (Decay Time)

Rate of Rise Slope of the curve from 10%A to 90%A

Surge Waveshape is specified as follows: A, Tr/Thy

e.g.: 500 volts, 5/1000 Microseconds

Vss Surge Striking Voltage

Vsdc dc Striking Voltage

Va Arcing Voltage

Delay Time T3 – T1 Transition Time T4 – T2

 T1 T2 T3 T4

 Time

FIGURE 2: ARRESTER BREAKDOWN NOMENCLATURE
-

7-

 

FIGURE 3 - BREAKDOWN TEST
- 8 -

NOTES:

1. S2 TO OPEN BEFORE S1 CLOSES

2. S1 TO REMAIN CLOSED FOR AT

LEAST l00MS.

3. CIRCUIT TO PROVIDE 0-20X 

950-l050MS IMPULSE

4. I1 = PEAK 500A±5%

5. I2 = PEAK 75A ± 331/3%

6. CB = MAIN CAPACITOR BANK;

LOW INDUCTANCE OIL FILLED

UNITS STRONGLY RECOMMENDED

FIGURE 4 – 500A SURGE GENERATOR