1995 Us Army Facilities Engineering Electrical Interior Facilities 180p

8/13/2019 1995 Us Army Facilities Engineering Electrical Interior Facilities 180p

1/180

ARMY TM 5-683NAVY NAVFAC MO-116

AIR FORCE AFJMAN 32-1083

FACILITIES ENGINEERINGELECTRICAL INTERIOR FACILITIES

APPROVED FOR PUBLIC RELEASE: Distributioni s un l imi ted

DEPARTMENTS OF THE ARMY, THE NAVY, AND THE AIR FORCENOVEMBER 1995

WWW.SURVIVALEBOOKS.COM


2/180

REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared by or for the Government and is

public property and not subject to copyright.

Reprints or republication of this manual should include a credit sub-

stantially as follows: J oint Departments of the Army, the Navy andthe Air Force, USA, Technical Manual TM 5-683/NAVFAC

MO-116/AFJ MAN 32-1083, Electrical Interior Facilities, 30 November

1995.



3/180

TM 5-68NAVFACMQ-11

AFJMAN 32-108

TECHNICAL MANUAL NO. 5-683 H E A D Q U A R T E R S

NAVY MANUAL NAVFAC MO-116 DEPARTMENT OF THE ARMY,

THE NAVY, AND THE AIR FORC

AIR

FORCE

MANUAL

AFJ MAN 32-1083W A S H I N G T O N, DC, 30 November 199

ELECTRICAL INTERIOR FACILITIES

cHAPTER 1.

2.

3.

4.

5.

6.

7.

8.

I N T R O D U C T I O NP urpose a nd s cope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Codes a nd s pecifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ma inten a nce requiremen ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P riority a nd schedu ling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ha za rds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SWITCHG EAR ASSE MBLI ES 600V OR LES S

P eriodic maint ena nce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Meta l enclosures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B us ba r a nd t ermina l conn ections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Un der floor ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bu swa ys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P ower circuit br eakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Netw ork protectors.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Auxiliar y sw itch gea r equipmen t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Switchgear trouble-shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TRANSFORMERS

Sm all pow er tr an sformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dr y-type t ra nsform ers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ELECTRIC MOTORS

Ma inten a nce of electric motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Altern at ing curr ent (AC) motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dir ect current (DC) motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motor operat ing considera tions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Motor insu lat ion testin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motor t rouble-shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MOTOR CONTROLS

Fun ctions o motor contr ols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Types of motor contr ols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Component s a nd m a intena nce of motor contr ols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P reventive ma intena nce an d tr ouble-shooting guid e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

POWER CABLES

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Visua l inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cable insulation testing ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Over potentia l testin g. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ca ble trouble-shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SOLID-STATE ELECTRONIC EQUIPMENT

Solid-sta te ma inten an ce. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Solid-state components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electrical disturbances (power quality) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dist urba nce meas urement a nd m onitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Volta ge surge su ppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

G R O U NDI NG

G round m ain tena nce. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Types of ground ing sy stems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

G round fa ult int errupt ing meth ods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P a r a g r a p h

11

1-2

1-3

1-41-5

1-61-7

2-1

2-22-32-42-52-62-72-82-9

3-13-2

4-14-24-3

4-44-54-6

5-15-25-35-4

6-16-26-36-46-5

71

7-27-37-47-5

8-l8-18-3

P a g e

11

1-1

111-1

1-11-21-2

2-1

2-12-22-22-22-32-102-122-16

3-13-1

4-14-14-13

4-204-244-24

5-15-15-66-15

6-l6-l6-16-26-5

7 17-17-77-77-8

8-18-18-9

*This manual supersedesTM 5-683/NAVFAC MO-116/AFM 91-17, dated 2 March 1972



4/180


5/180

TM 5-683/NAVFAC MO-116/AFJMAN 32-108

LIST OF FIGURES(cont'd)

Figure 211. Lar ge cell for a st at ionar y ba tt ery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3-1. Dry-type tr a nsform er. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-1. Cut a wa y view of squirr el-cage ind uction motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-2. Cut aw ay view of w ound-rotor induction m otor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-3. Cut aw a y view of syn chronous mot or . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-4. Pr ima ry pa rts of an AC induction m otor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-5. Clean ing a nd dr ying m otors in pla ce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-6. Bea ring in sta llat ion precaut ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-7. Constr uction of ball a nd r oller bea rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-8. Gr eas ing bea rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-9. Typical sleeve bear ings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-10. Cuta wa y view of a typica l DC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-11. Main t ypes a nd connections of D Cmot ors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-12. Arma tur e of a la rge DC motor on st an ds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-13. Inspecting a nd inst alling br ushes on a larg e DC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-14. Cuta wa y section of a commut a tor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-15. Bru sh " cha tt eract ion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-16. Poor commuta tor conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-17. Good commutator films.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-18. Exam ple of eccentric commuta tor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-19. Dial ga uge to mea sure commut a tor concentricity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-20. Common und ercuttin g mist a kes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4-21. Connections for test ing mot or insula tion resist a nce. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-1. Man ua l sta rt ers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-2. Typical ma gnetic st a rter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-3. Combina tion st a rter s in NE MA enclosures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-4. Coordination of motor overload relay and current limiting fus e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-5. Autot ra nsform er sta rter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-6. Resista nce sta rt er. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-7. Pa rt-Winding s ta rt er. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-8. Solid St at e sta rt er . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-9. Typical motor control center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-10. Cuta wa y view of typical molded case circuit breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-11. Molded cas e circuit brea ker tim e-current curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-12. Fuse ma inten an ce practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-13. Underwriters Laboratories Cartridge fuse classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-14.Typica l t herm al overloa d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-15. Typical hea ter s election t a ble for therm al overload device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-16. A NE MA size 6 ma gnet ic conta ctor (courtesy of Siemen s-Allis) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6-1. Connections for test ing low volta ge cable insulat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

71. Typical ca pacitor t ypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2. Diodes a nd SC Rs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

73. Cha ra cterist ics of diodes an d Zeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4. Testing Zener volta ge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

75. Tra nsist or test ing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1. Typical equipm ent g round . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2. Typical grounding sy stem for a building an d its a ppara tus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3. Methods of system ground ing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4. Methods o fsolidly groundin g th e neutra l of three-phase syst ems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5. Methods of resistance grounding the neut ra l of three-phase sy stems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-8. Gr ounding for electronic a nd ADP syst ems.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-7. Gr ound fa ult circuit int errupt er operat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-1. Prehea t fluorescent lam p an dfixture components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-2. Mercury la mp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-3. Trouble-shooting flu orescent lightin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-1. Sa mple comput er-ba sed fire detection sys tem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10-2. Cla ss A a nd B fire detection circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

121. P a dlock and mult iple lock ad apt er . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

122. Typical safety tag. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

123. Ground cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12-4. Grounding clamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

125. Ey e an d fa ce protection selection guide.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13-1. Set-up for mea surin g AC volta ge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13-2. Set-up for measuring resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P a g e

2-1

3-2

4 -8

4 -9

4-14-1

4-1

4-1

4-1

4-1

4-1

4-1

4-1

4-1

4-1

4-1

4-2

4-2

4-2

4-24-2

4-2

4-2

5 -2

5-2

5-3

5-4

5-5

5 -6

5-7

5 -8

5-9

5-1

5-1

5-15-1

5-1

5-1

5-1

6 -2

7 -3

75

7 -6

7-6

7-8

8 -3

8-4

8-5

8 -6

8 -6

8-1

8-1

9-2

9-3

9-4

10-2

10-3

122

122

123

12-4

12-6

13-4

13-5



6/180


LIST OF FIGURES (contd)

Figure 13-3.

13-4.

13-5.

14-1.14-2.

14-3.

14-4.

14-5.

14-6.

14-7.

14--6.

14-9.

14-10.

14-11.

Ta ble 2-1.2-2.

4-1.

4-2.

4-3.

4-4.

4-5.

5-1.

5-2.

6-1.

6-2.

71.

9-1.

10-1.

111.

13-1.14-1.

14-2.

15-1.

15-2.

15-3.

1.54.

Set-up for testin g pha se sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Megohmmeter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..........

Diagram of megohmmeter connections.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Comp a r i s on o f wa t e r f low w i t h e le c t r i c c u r re n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Curves showing components of measured current during insulation testing . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Typical curves show ing dielectric absorption effect in a time-resistence or double-read ing t est . . . . . . . . . . .

Resistive components of a made electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

S o i l r e s i s t i v i t y v s m o i s t u r e c o n t e n t o f r e d c l a y s o i l . . . . . . . . . . . . . . . . . . . . . . . . -

Soil resistance vs temperature of clay soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Soil resistance vs depth of electrode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ea rth electrode w ith h emispheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fall-of-potential method graph. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sampling the cell electrolyte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reading the hydrometer f loat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LIST OF TABLES

U.S. s ta ndard bolt t orgues for bus connections heat t reated steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Trouble-shooting procedures for switchgear equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motor application guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nam eplate voltage ra tings of sta nda rd induction motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AC synchronous motor trouble-shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..........

DC motor generator trouble-shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motor control preventat ive maintenance guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motor control trouble-shooting chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -

Condu ctor sizes, insula tion th ickness, test voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cable maintenance overheating problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P ower q ua lity problems su mm ar y .. ...--. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lamp trouble-shooting guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....

Comparison of fire detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Common tra de nam es for P CB by ma nufa cturers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tools an d equipment for effective electrical m ain tena nce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..Interpreting insulation resistance test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Condit ion of insu lat ion indicat ed by dielectric absorption r at ios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P ercenta ge of failure cau se since ma inta ined.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Equipment fa ilure rate mult ipliers vereus maintenance quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Int erior wirin g a nd light ing sys tem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electric motors a nd controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P a g e

13-6

13-7

13-7

14-2

14-2

14-3

14-5

14-5

14-6

14-6

14-6

14-7

14-s

14-9

P a g e

2 -32-17

4 -2

4-24

4-26

4-33

4-36

5-17

5-19

6 -6

6-7

79

9 -6

10-4

112

12-2

14-3

14-4

15-2

15-2

15-3

15-5

i v



7/180

TM5-683/NAVFAC MO-116/AFJMAN 32-1083

CHAPTER 1

INTRODUCTION

1-1. Purpose and scope.

This ma nua l provides guidance to facil i t ies ma inte-

na nce personnel in the ma intena nce of interior elec-

trical systems of 600 volts and less. These systems

include such components as illumination, low volt-

age syst ems, rotat ing equipment, motor control cen-

te r s , so l id-s t a te equ ipment , t r ans f o rmers , and

switchgear . It also a pplies to low volta ge controlled

devices on high-voltage systems. The procedures

presented in this manual are basic and can be ap-

plied to the equipment of any manufacturer. De-

tailed information and instructions should be ob-

tained from the instruction book for the particulartype of equipment being serviced.

1-2. References.

Appendix A cont a ins a list of references used in this

m a nu a l .

1-3. Codes and specifications.

Maintenance on electrical systems and equipment

must ad here to the codes and specif icat ions a s they

apply to the work to be performed. Also, manufac-

turers maintenance instructions which accompany

select electrica l components m ust be applied in con-

junction with the codes and specifications listed be-

low and the departmental specif ications l isted in

appendix A.

a. The National Electrical Code [National Fire

P rot ection Associat ion #70 (NF P A 70)]. This code is

the most w idely a dopted set of electrical sa feguard-

ing practices. It defines approved types of conduc-

tors and equipment, acceptable wiring methods,

mandatory and advisory rules, operating voltages,

limitations on loading of conductors, required work-

ing spaces, methods of guarding energized parts ,

interrupting capacity requirements of system pro-tective and control devices, requirements for con-

nections and splices, insulation resistance require-

ments, a nd grounding requirements.

b. Recommended Practice for Electrical Equip-

ment Maintenance (NFPA 70 B).

C. A m e r i c a n N a t i o n a l S t a n d a r d s I n s t i t u t e /

Insti tute of Electrical and Electronics Engineers

St a nda rd (ANS I/IE EE St d.) cha pter 15, 242-1986,

IEEE Recommended Pract ice for Protect ion and Co-

ordinat ion of Industria l and Commercial Power Sys-

tems. This code provides preventive maintenance

practices for electrical systems a nd equipment usedin industrial-type applications.

1-4. Maintenance requirements.

Preventive maintenance should not be confused

with repairs af ter a breakdown. The definition of

maintenance implies that the equipment or system

is inspected to discover i ts weaknesses and then

repair or replace the necessary elements before a

breakdown occurs. A maintenance program for pro-

tective devices and the electric system could be di-

vided into the following steps: inspecting, cleaning,

tightening, lubricat ing, testing, a nd r ecording.

a. The effectiveness of the distribution system is

measured in t erms of volta ge regula tion, power fac-

tor, load balance, reliability, efficiency of operation,

and costs. To ensure the systems efficiency, lessen

failures, and maximize safety, an effective mainte-

nance program must be employed. This program

should in clude an d/or consider t he follow ing:

(1) Scope of work.

(2) Intervals of performance.

(3) Meth ods of a pplica tion.(4) Safety requirements, practices and proce-

dures.

(5) Adherence to codes, specifications and di-rectives.

(6) Maintenance management procedures re-

garding tools, records, and follow-up procedures.

(7) Ha zar ds associat ed with w ork and the fa cil-

i ty .

(8) Emergency operating instructions.

(9) Requirements for periodic review to deter-

mine addit iona l loading in circuits such a s in fam ily

housing, bachelor quarters, and maintenance and

administrat ive bui ldings.

b. A well executed maintenance program will

provide benefits in t erms of:

(1) Economic operation.

(2) Improved safety.

(3) Longer equipment life.

(4) Reduced repair and overhaul time.

(5) Fewer unplanned outages.

(6) Early detection of undesirable changes in

the power syst em.

(7) Improved operation of the facility.

1-5. Records.

A good record keeping system is essential for safe,

efficient a nd economical operat ion of electr ical fa cil-

i t ies and for planning and executing an effective

1-1



8/180


prevent ive maintenance program. I t i s recom-

mended to use the Work Information Management

Syst em (WIMS) or other da ta -aut omated systems t o

keep records rather than paperwork f i les. Suitable

forms and reports requirements should be devel-

oped to suit local needs. When facilities are built,

instruction documents and spare parts l is ts for al lequipment installed should be obtained prior to

beneficial occupancy acceptance.

a. In addition to charts , work orders, and real

property records, the following records have been

found useful in analysis and correction of recurring

trouble areas.

(1) Diagrams. Accurate single-line and sche-ma tic diagra ms of the distribution system should be

readily accessible in the electrical shop. These are

essential references when switching circuits and re-

routing electric power in emergencies. Such dia-

grams also provide a simple means of locating facil-

ities and determining the characteristics of electricsupply to buildings requiring maintenance. Electri-

cal personnel must have access to latest "as-built "

building drawings for use in tracing out circuitry

within buildings.

(2) Equi pment l i sts/ logs. These lists should bemaintained on all i tems of equipment such as mo-

tors, motor controllers, meters, panelboards, electri-

cal controls, and switchgear. Lists should reflect

detailed information such as the density of al l l ike

it em s, i t e m r a t i n g s a n d p h y si ca l l oc a t i on s .Lists/logs w ill fa cilita te scheduling of in spections

and maintenance services.

(3) Equipment maintenance records. Theserecords should be maintained on every individual

i tem of electrical equipment that requires mainte-

nance services. Records should include detailed in-

formation such as scheduled maintenance and in-

spect ion requ i rements , p rev ious tes t resu l t s ,

maintenance repairs performed and any other re-lated information that would facil i tate analyzing

the equipment performance. Maintenance records

should be retained on file for as long as needed to

allow collection of sufficient data to perform the

equipment performance analyses. By observing the

equipment performance, downward trends can be

identified and problem areas corrected before majorbreakdowns occur.

(4) Em er gency opera t i ng i nst ru ct i ons. E m e r -

gency operation of electrical facilities is safer and

quicker when instructions are prepared and posted

in advance. There should be instructions for each

genera l type of an ticipated emergency, sta ting w ha t

each employee in the electrical section should do,

setting up a lternat ives for key personnel, and estab-

lishing follow-up procedures for use after an emer-gency has passed. Instructions should be posted in

the electrical shop, security guard office, all em

gency generating or opera ting a reas, a nd other lo

tions as the responsible supervisor deems necessa

Employees should be listed by name, title, offi

telephone number, home address and home te

phone number (where permissible). These instr

tions should emphasize safety under conditionsstress, power interruptions and similar emerg

cies.

1-6. Priority and scheduling.

In regard to the support of the instal led phys

facilities, it is the policy of the Military Dep

ments t hat , in order of priority , ma intenance sho

be second only to operations. It must be system

and timely. Subsequent sections in this docum

provide generaI suggestions on service frequenc

and procedures. Although these proposed acti

and frequencies may appear to be excessive, th

suggestions are based upon experience and equment manufacturers recommendations. They

not intended to supersede instructions that elec

cal manufacturers normally provide. Every reali

effort should be made to adhere to these suggesti

considering existing manpower levels and availa

test equipment. It is generally good practice to

spect equipment three to six months af ter i t is f

put into service and then to inspect and maintai

every one to three years, depending on its serv

and operating conditions. Conditions that make quent maintenance and inspection necessary a

a. High humidity and high ambient temperatu

b. Corrosive atmosphere.c. Excessive dust and dirt .

d. High repeti t ive duty.

e. Frequent fault interruption.

f. Older equipment.

1-7. Hazards.

Material specifications, construction criteria, ins

l a t ion s t andards , and s a f e work ing procedu

should be applied to minimize hazards. All w

should be performed by qualified electricians

conform to the latest accepted procedures and s

dards .

a. Building electrical systems. Fi re and s a fhazards in building electrical systems often re

from tampering by unqualif ied personnel. Proba

the greatest example of tampering is the unaut

rized changing or replacing of fuses. Careful ob

vation by maintenance personnel is needed to c

trol excessive use of items such as extension cor

heaters, air conditioners, and improper ground

which cause over loading o f the wir ing sys te

Whenever possible, installation of additional rectacles is preferable to the use of extension cor

1-2



9/180

Each building should be inspected for loose wires,

poor connections, bare conductors, unauthorized or

nonstand ard at ta chment cords, use of wiring or f ix-

tures as support for extraneous i tems, any condi-

tions likely to cause f ires and la mps larger tha n th e

sta nda rd size prescribed for outlets .

b. Hazardous locations. Special occupancy areasinclude gara ges, aircraf t h an gars, ga soline dispens-

ing and service stations, bulk storage plants , and


health care facil i t ies . Such areas designed as "Haz-

ards Locations," as specified in Article 500 of the

Na tional E lectrical C ode, require special an d equip-

ment considerations. These considerations include

the use o f specia l f i t t ings , r ig id condui t , and

explosion-proof apparatus. Maintenance personnel

must ensure that a l l work performed in a hazardousarea complies with the code requirements for the

areas particular hazard classif ication.

1-3



10/180


CHAPTER 2

SWITCHGEAR ASSEMBLIES 600V OR LESS

2-1. Periodic Maintenance.

A periodic maintenance schedule must be estab-

l i s h e d t o o b t a i n t h e b e s t s e r v i c e f r o m t h e

switchgear. Annual check should be made on all

major switchgear devices af ter instal lation. After

trends have been established regarding the equip-

ment condition a nd reliabil ity , t he ma intenance in-

terval may be extended (1836 months) in keeping

with the operating conditions. A permanent record

of all maintenance work should be kept. The record

should include a list of periodic checks and tests

made (including date of test), condition of the equip-

ment, repairs or adjustments performed, and test

da t a tha t w ould faci li ta te per forming a t rend analy-

sis. Maintenance personnel must follow all recog-

nized safety pract ices , both the nat ional ly publ ished

standards and mili tary regulations. Some specif ic

suggestions in dealing with switchgear mainte-

na nce are given below:

a. Tools designed for slowly closing switchgear

circuit breakers or other devices during mainte-

na nce are not suita ble for use on an energized sys-

tem. The speed necessary for device closing is as

important as its speed in opening; therefore, a

wrench or other manual tool is not fast enough.

b. Before working on a switchgear enclosure,verify that the enclosure is de-energized by check-

ing for volta ge using a volta ge detector.

c. Disconnect all drawout or tilt-out devices such

as circuit breakers, instrumentation transformers,

an d control power tra nsformers.

d. Do not lay tools on the equipment w hile work-

ing. It is al l too common to forget a wrench when

closing up an enclosure. Dont take the chance.

e. Never rely upon the insulat ion surrounding a n

energized conductor t o provide protection t o person-

nel. Use suitable safety clothing and equipment.

f. Always use the correct maintenance forms and

equipment. When performing maintenance the fol-lowing should be a vaila ble:

(1) Forms for recording th e condit ions as found

an d w ork done.

(2) Control power connections, test couplers,and spare parts recommended by the manufacturer

to facil i tate repair and maintenance of each type ofcircuit breaker.

(3) Special tools, such as lifting mechanismsfor removing an d t ra nsporting power circuit break-

ers, relay test plugs for testing a nd calibrat ing pro-

tective relays, a low resistance ohmmeter for mea-

s u r i n g t h e r e s i s t a n c e o f c o n t a c t s , a m m e t e r s ,

voltmeters, m egohmm eters, low voltag e/high cur-

rent t est sets for testing power circuit breakers, a nd

other special test equipment.

(4) Manufacturers instruction books regarding

the maintenance of switchgear devices such as cir-

cuit breakers, relays, bus bars, meters, etc. The

fundamentals that are presented in the upcoming

sections are designed to supplement these instruc-

tions, giving the elements of the overall mainte-

nance program ra ther t han the deta i ls.

2-2. Metal enclosures.

Maintenance is recommended below:a. With power off and the bus properly grounded,

open the enclosure and remove any accumulated

dust and dirt . Vacuum cleaning is recommended;

blowing with compressed air is not.

b. Check structure and anchor bolts for t ight-

ness . For bus and breaker connect ions ensure

manufacturers specified torques are used.

c. Clean and lubricate circuit breaker racking

mechanisms with a non-hardening, non-conductive

grease.

d. Inspect operation and adjustment of safety

shutters, mechanical and key interlocks, auxil iary

and l imit sw itches.e. Clean and inspect strip heaters.

f . Clean any a i r f i l ters tha t are ins ta l led in the

ventilation openings.

g. Inspect all relays, contractors, switches, fuses,

and other auxiliary devices for correct operation

an d cleanliness.

h. Tighten control wiring connections.

i . Inspect al ignment and contacting of primary

disconnecting devices, checking for signs of abnor-

ma l wea r or other dam age. Discolora tion of these or

other si lvered surfaces is not usually harmful un-

less caused by sulphide deposits, which can be re-

moved by a solvent , such a s a lcohol, or silver polish.j . A f t e r c l e a n i n g , m e a s u r e t h e r e s i s t a n c e t o

ground and between phases of the bus with a

megohmmeter (para 14-2). It is not possible to give

definite l imits for sat isfactory insulation resista nce

values, so that a change in the reading from one

inspection period to another is the best indication of

any weakening tendency. The readings should be

taken under similar conditions each time, and the

record should include temperature and humidity.

k. B efore replacing th e breaker, wipe the primar y

disconnecting device contacts. Apply a thin coat of

2-1



11/180

TM 5-683/NAWAC MO-116/AFJMAN 32-1083

contact lubricant to the s ta t ionary s tuds and to the

primary disconnects on the breaker.

l . Ensure that all metal shields are securely in

place. These shields must be installed to confine any

blast in the event of circuit breaker failure.

(1) A n ote on l ubr icants. One of the most useful

lubricants for motors is an extreme pressure (EP)

lithium-base petroleum grease. As the usage of

Class F winding temperat ure rat ings has increased ,

however, others have adopted synthetic greases to

withstand higher bearing temperatures .

(2) Synt hetic oil s and greases. Synthetic oi ls

and greases compounded from various silicones,

alkyl benzene, diesters, and fluorinated ethers, are

available for extremely high-temperature service

that would cause premature oxidation of petroleum

lubricants. Some synthetics also suit extremely low

temperature, down to 40 or 50 degrees below zero.

The main uses for synthetic lubricants in motorbear ings a re reduced f r i c t ion and res i s tance to

moisture and chemical contamination. Such appli-

cations must be carefully worked out with bearing

a nd lubricant suppliers, beca use no universal lubri-

cant formulation will apply to all environments.

However, i t is not unusual for lubricant to vary

little more than brand name. Thus substitutions are

often possible. Consult with t he man ufactur er of the

switchgear to determine the importa nt characteris-

tics of the lubricant prior to specifying a substitute

lubricant. Carefully selected substitutes will reduce

the cost of procurement, stocking and dispensing.

2-3. Bus bar and terminal connections.

Many fa i lures a re a t tr ibutable to improper termina-

tions, poor workmanship, and different characteris-

tics of dissimilar metals. Loose bus bar or terminal

connections will cause overheating which can be

easily spotted by a discoloration of the bus bar. A

thermographic survey can be conducted to detect

overheating before discoloration occurs (para 14-7).

An overheating condition will lead to deterioration

of the bus system a s well as t o equipment connected

to the bus; i.e. protective devices, bus stabs, etc.

Therefore, bus ba r a nd t ermina l connections should

be regularly checked to ensure that they are prop-

erly tightened without damaging the conductors.

Special attention should be given where excessive

vibration may cause loosening of bolted bus and

terminal connections. Tightening torque values for

electrical connections are provided in table 21.

This information should be used for guidance only

wh ere no tight ening informat ion on t he specific con-

nector is available. I t should not be used to replace

manufacturers instructions which should always be

followed. Do not assume that once a connection has

been torqued to its proper value that i t remains

2-2

tight indefinitely. I f signs of arcing ar e evident, t hen

the connections should be broken and the connect-

ing surfaces cleaned. Because of the different char-

a cteristics of copper an d a luminum, t hey should not

be intermixed in a terminal or splicing connector

wh ere physica l conta ct occurs between t hem, unless

th e device is suita ble for t he purpose and conditions

of use. Materials such as solder and compounds

shall be suitable for the use and shall be of a type

which will not adversely affect the conductors.

a. Al um in um connectors. Special considerations

must be given to aluminum connections. Aluminum

connectors are plated and should not be cleaned

with abrasive. I f these connectors are damaged,

they should be replaced. I t should be noted that

when making connections with aluminum conduc-

tors, be sure to use a joint compound made for the

purpose. To assist in the proper and safe use of solid

aluminum wire in making connections to wiringdevices, refer to the National Electrical Code. Make

aluminum connections with solderless circumferen-

tial compression-type, aluminum-bodied connectors

U L list ed for AL/CU . Remove sur fa ce oxides from

aluminum conductors by wire brushing and imme-

diately apply oxide-inhibiting joint compound and

insert in connector. After joint is made, wipe away

excess joint compound and insulate splice.

b. Bus in sulators and barr iers. Bus bar support

insulat ors an d/or barr iers should be wiped w ith a

clean cloth. Do not use steel wool or oxide papers to

remove dirt; use a cleaning solvent that will not

leave trace deposits. While cleaning, check insula-tors for cracks and signs of arc tracking. Defective

units should be replaced. Loose mounting hardware

should be tightened.

2-4. Underfloor ducts.

All undefloor duct systems require checks for evi-

dence o f o i l and wa ter . Entrances and f i t t ings

should be checked and corrected as necessary to

prevent entrance of l iquids, insects, and rodents.

Cockroaches, ants, beetles and rodents have been

known to a t t ack cab le insula t ion , espec ia l ly i f

greases or oi ls are present . External heat and heat

caused by overloaded circuits can cause cracking of

cable insulation and drying of taped splices. Mois-

ture can then penetrate the cable and could cause a

fault. Therefore, underfloor conduits and duct sys-

tems should be kept sufficiently clear of electrical

and hot water f loor-heating systems to prevent un-

due heating of the enclosures.

2-5. Busways.

Feeder busway, trolley busway and plug-in busway

(fig 21) require annual cleaning and removal of oil

substances and dirt. Ventilated-type busway should



12/180

TM 5-683/NAWAC MO-116/AFJMAN 32-1083

NOTE : REDUCE TORQUE BY 20% WHEN CADMIUM PLATED BOLTS ARE USED.

have the bus bars cleaned annually with clean, dry

compressed a i r a t a maximum pressure o f 50

pounds per square inch. Plug-in devices should be

s e r v i c e d u s i n g t h e s a m e p r o c e d u r e s a s o t h e r

switches or breakers. The plug-in bus or prongs

should be checked annually for annealing or corro-

sion on all connections which are rated in excess to

75 percent of the rating of the bus duct. Connections

should not be retorqued as part of a routine main-

tenance procedure unless visibly loose or shown to

be loose by an infrared scan. All busway connections

should be torqued according to manufactures rec-

ommendations. If this information is not available,

use the torque specifications in table 2-1. Inspect toensure tha t :

a. Ventilation continues to be adequate.

b. Clearances are maintained and encroachment

from other equipment facilities has not occurred.

2-6. Power circuit breakers.

Power circuit breakers encompass all breakers ex-

cept molded case breakers and breakers used for

control applications. It is recommended that power

circuit breakers be inspected once a year after in-

stallation. More frequent inspections are recom-

mended where severe load conditions, dust, mois-

ture or other unfavorable conditions exist, or if the

vital nature of the load warrants i t . Any breaker

that has in terrupted a f aul t a t or near i ts shor t

circuit ra ting should be inspected immediately a f ter

the in terrupt ion and serviced i f necessary . Re-

energize equipment completely before working on

any devices , connect ions , bus work, breaker orf eeder cab le compar tmen ts . Th is inc ludes de-

energizing any connections to outside primary or

secondary sources such as transformers, tie lines,

etc. Manufacturers instruction documents should

also be obta ined and read carefully before disassem-

bly or adjustments are performed.

a. Drawout circu i t breakers. A d r a w o u t - t y p e

breaker should be tested and inspected for proper

operation as follows:

(1) Withdraw the breaker to the test position.This position disconnects the primary power circuit



13/180


FEEDERBUSWAY

PLUG-IN

N>

BUSWAY

F i gu r e 2 -1 . Typ i ca l busway i n s ta l l a t i o n .

but leaves the control circuits energized (fig 2-2). If

a test position is not provided, then complete-

ly withdraw the circuit breaker from its compart-

ment and use a test coupler to provide control

power.

(2) Test for voltage to make sure that all pathsof potential backfeed from control power circuits, as

well as outside sources, are disconnected. This is

especia lly importa nt if an externa l source of control

power is being used for t esting.

(3) Operate the breaker and check all func-tions. Use both the electrical means (when pro-

vided) and the mechanical means to charge, close

and trip the breaker. This is particularly important

for breakers that normally remain in ei ther the

opened or closed position for long periods of time.

(4) Remove the breaker from its compartment

to a c lean maintenance area . Close the compart-

ment door and cover the breaker cutout to prevent

access t o live part s.

(5) Check and lubricate all safety rollers andauxiliary contacts. Check all mechanical clearances

to ensure they are within manufacturer specified

tolerances. Also inspect a nd lubricate bus st a bs an d2-4



14/180

TM 5-683/NAVFAC M116/AFJMAN 32-1083

~DISCONNECTED

ALL POWER DISCON-NECTED

WITHDRAWNBREAKER WITHDRAWNREADY FOR REMOVAL

F i gu r e 2-2. D raw ou t c i r c u i t b r ea ke r pos i t i o n s .

a c/dc cont rol block cont a cts. Verify corr ect opera tion

of trip free and anti-pump mechanisms.

b. Fi xed circui t br eakers. Maintenance on fixed-

or bol ter-type c ircui t breakers is normally per-

formed with the breaker in place inside its cubicle.

Special precautions must be exercised to assure

equipment is de-energized and the circuit in which

it is connected is properly secured from a safety

s tandpoin t . Al l contro l c i rcu i t s should be de-

e n e r g i ze d . S t o r e d e n e r g y c l o s i n g m e c h a n i s m sshould be discharged.

c. Power cir cuit breaker comp onent s. M a i n t e -

nance on all power circuit breakers will encompass

maintenance on the following components.

(1) Insulat ion. The general rule for insulationis keep it clean an d dry. Remove interpha se barriers

and clean them and all other insulating surfaces

with dry compressed air and a vacuum cleaner.

Wipe insulation with clean lint-free rags and sol-

vents as recommended by the manufacturer if hard-

ened or encrusted contamination must be removed.

Repair moderate damage to bushing insulation by

sanding smooth and refinishing with a clear insu

lating varnish. Check insulating parts for evidence

of overheating a nd for cracks tha t indica te excessive

thermal aging.

(2) Contacts. Th e major function of the powe

circuit breaker depends among other things upon

correct operation of i ts contacts. These circui

breakers normally have at least two distinct sets o

contacts on each pole, main and arcing (fig 2-3)Some have an intermediate pair of contacts which

open after the main contacts and before the arcing

contacts.

(a) M ain contacts. When the b reaker i s

closed, practically the entire load current passes

through the main contacts. Also, short circuit cur

rent must pass through them during opening or

closing faulted lines. If the resistance on these con

tacts becomes high, they will overheat. Increased

contact resistance can be caused by pitted contac

surfaces, foreign ma terial embedded on conta ct sur



15/180


FIXED ARCING CONTACT

MOVABLECONTACT

MOVABLE MAIN

CONTACT

ARCI

F i gu r e 2 -3 . Power c i r c u i t b r ea ke r m a i n a nd a r c i n g con ta c t s .

faces, or weakened contact spring pressure. This (c) Contact maintenance. The general rules

will cause excessive current to be diverted through

the arcing contacts, with consequent overheatingand burning.

(b) Ar cin g contacts. Arcing contacts are the

last to open; any arcing normally originates on

them. In circuit interruption, they carry current

only momenta ri ly , but tha t current may be equal t o

the interrupting rating of the breaker. In closing

aga inst a short c ircui t , they may momenta ri ly carry

considerably more than the short circuit interrupt-

ing rating. Therefore, they must make positive con-

tact when they are touching. I f not, the main con-

tacts can be badly burned or may result in a failure

to interrupt a faul t .

for maintaining contacts on all types of breakers

a re: keep them clean, a ligned and w ell adjusted. Toinspect the circuit breaker contacts, the arc chutes

must be removed. When doing this, check the arc

chutes for evidence of damage, and replace dam-

aged parts. I f not damaged, then blow off dust or

loose particles. Once the main contacts are exposed,

inspect their condition. Slight impressions on the

sta tionary conta cts cau sed by the pressure a nd wip-

ing a ction of the mova ble conta cts is tolerable. Con-

ta cts w hich h ave been roughened in service should

not be f i led but large projections, caused by u nusua larcing, should be removed by filing. When filing,

take care to keep the contacts in their original de-



16/180


sign. That is, i f the contact is a l ine type, keep the

a rea of conta ct l inear , and if ball ty pe, keep the ball

shaped out. Discoloration of silver-plated surfaces is

not usually harmful unless caused by insulating

deposits. These deposits should be removed with

alcohol or a silver cleaner. Whether cleaned or not,lubricate the main contacts by applying a thin f i lm

of slow aging, heat resistant grease. All excess lubri-

cant should be removed with a clean cloth to avoid

accumulation of dirt and dust. Under no circum-

stances should the arcing contacts be lubricated.

Where serious overheating is indicated by discolora-

tion of metal and surrounding insulation, the con-

tact and spring assemblies should be replaced in

accorda nce with ma nufacturers instructions. While

careful ly c losing the c ircui t breaker , check for

proper gap, wipe and contact alignment. Contact

gap is the d is ta nce betw een t he s ta t ionar y a nd mov-

able contacts with the circuit breaker in the fully

open position. I f the a rcing conta ct ga p is too small ,

a circuit breaker may not be able to interrupt a

fault. I f the main contact gap is too small , the mainconta cts wi l l interrupt the faul t a long with t he arc-

ing contacts and possibly burn the main contacts.

Contact wipe is the amount of over travel between

the stationary and movable contacts from the time

when the contacts are just touching to the time

when the circuit breaker is fully closed (figs 24,

25, and 26). Check that all contacts make and

break at approximately the same t ime. Make ad-

justments in accordance with the manufacturers

recommendat ions. La mina ted copper or brush st yle

b

F i g u r e 2-4. Arc i n g con ta c t gap and w i pe.

CONTACT WIPE

2-7



17/180


ACRING CONTACTS

TOUCHING

CON

F i gu r e 2-5 In t e rmed i a t e con ta c t gap .

contacts found on older circuit breakers should be

replaced when badly burned. Repairs are not prac-

tical because the laminations tend to weld togetherwhen burning occurs, and contact pressure and

wipe are greatly reduced. These contacts may be

filed to remove large projections or to restore their

original shape. They should be replaced when theyare burned sufficiently to prevent adequate circuit

breaker operation or when half of the contact sur-

face is burned aw a y. Ca rbon conta cts, used on older

circuit breakers, require very li ttle maintenance.

However, inadequate contact pressure caused by

erosion or repeat ed f il ing m ay cause overhea ting or

interfere with their function as arcing contacts.

(3) Operating mechanism. The purpose of theoperating mechanism is to open and close the

breaker contacts. This usually is done by linkages

connected, for most power breakers, to a power op-

erating device such as a solenoid or closing spring

2-8

for closing, and contains one or more small sole-

noids or other types of electro-magnets for tripping.

Tripping is accomplished mechanically, independent

from the closing device, so tha t the brea ker conta cts

will open even though the closing device still may be

in the closed position. This combination is called a

mechanically trip-free mechanism. After closing,the prima ry function of the opera ting mechan ism is

to open the breaker when it is desired, which is

wh enever t he tr ipping coil is energized at above its

rated minimum operating voltage. The breaker op-

erating mechanism should be inspected for loose or

broken par ts; m issing cott er pins or reta ining keep-

ers; and missing nuts and bolts. I t should also be

examined for damage or excessive wear on cam,

latch, and roller surfaces. Excessive wear usually

results in loss of travel of the breaker contacts. I t

can affect operation of latches; they may stick or

slip off and prematurely trip the breaker. Adjust-



18/180

TM 5+583/NAVFAC MO-1 16/AFJMAN 32-1083

11L 1 3CONTACT WIPE16 32

Figure 2-6. Main contact wipe.

menta for excessive wear are possible for certain lubricate pins and bearings not disassembled. Useparts . For others, replacement is necessary. The non-ha rdening a nd non-conductive grease lub

closing and tripping action of a breaker should be cate the ground or polished surfaces of cam

quick and positive. While documenting, operate the rollovers, latches and props, pins and bearings th

breaker several times, checking for obstructions or are removed for cleaning. Check the breaker ope

excessive friction. Any binding, slow a ction, dela y in a t ing mechanism adjustments and readjust as d

speration, or failure to tr ip or latch must be con- scribed in th e ma nufa cture%inst ruction book.

rected prior to returning to service. Clean and these adjustments cannot be made within specifie

relubricate the operating mechanism. Use a tolerances, it will usually indicate excessive we

nondetergent light machine oil (SAE-20 or 30) to and the need for a complete overhaul.

2



19/180


(4) T r i p devi ces. The t rip devices on low volta ge

circuit breakers provide the electrical decisions

needed to detect th e difference between norma l an d

abnormal conditions of current flow. The mainte-

nance and adjustment of these devices is just as

important as the work performed on the main con-

tacts and operating mechanism. The trip devices

are either electro-mechanical or solid-state. Both

types are responsible for providing various degrees

of fixed, short, or inverse time delays ba sed on the

a m o u n t o f c u r r e n t t h e y s e n s e . T h e e l e c t r o -

mechanical type, with an air or f luid dashpot for

time delay, should be tested as part of the mainte-

na nce work performed. A dash pot is a pneumat ic or

hydraulic device used for cushioning or damping of

movement to a void mechanical sh ock a nd consisting

essentially of a cylinder conta ining air or l iquid a nd

a pis ton moving in i t . Test ing of the electro-

mechanical devices requires th e use of a low volta ge

(about 0-20V) but h igh current (usua l ly O-

50,000A) prima ry injection t est set designed specifi-cally for this purpose. Calibration tests should be

ma de to verify th at the performa nce of the device is

within the values shown on the manufacturers pub-

l ished curves; taking into account that the time-

current curves are plotted as a band of values

rather than a single l ine (fig 27). Pay careful at ten-

t ion to how the manufacturer has presented the

curve data. There is a wide variety of formats.

Check to see tha t t he current is in amperes or mul-

tiples of a pickup value and whether temperature

ranges or previous conditions will affect results.

Usually, the trip devices are tested one unit at a

time. There ar e some devices which ma y use a ther-mal element for time delay. These may have to be

tested all at once to get results similar to those

published by the ma nufa cturer. Check the t est con-

ditions carefully. I f the trip devices do not operate

properly, the calibration and timing components

should be adjusted or replaced per the ma nufa ctur-

ers recommendations. If repair or replacement of

the electro-mechanical devices is being considered,

then thought should be given toward retrofitting

the existing breaker with solid-state trip devices.

This newer technology is generally more reliable

beca use the part s used to make th e trip unit do not

drif t out of a djustm ent or suffer th e effects of a ging

or contamina t ion to the same degree as the i r

electro-mechanical forerunners. I f the breakers a re

a lready equipped w ith solid-sta te t rip devices, they

should also be checked for proper operation and

time delay in accordance with the manufacturers

published curves. The test procedure recommended

by th e ma nufa cturer should be followed.

(5) Au xil ia ry devi ces. Inspect the closing motoror solenoid, shunt trip coil and mechanism, alarm

2-10

mechanisms, and the control wiring for correct op-

erations, insulation condition and tightness of con-

nections. Check on-off indicators, spring-charge in-

dicators, mechanical and electrical interlocks, key

interlocks, and lock-out fixtures for proper opera-

tion and lubricate where required. In particular,

test the positive interlock feature which prevents

the insertion or removal of the breaker w hile it is in

the closed position. Check control devices for free-

dom of operation. Replace contacts when badly worn

or burned. After the breaker has been serviced,

manually operate it slowly with a closing device to

check for tightness or friction and to see that the

contacts move to their fully open and fully closed

positions. Electrically operate the breaker several

times to check the performance of the electrical ac-

cessories using the TEST position, an external

test /cont rol cabinet , or a test coupler.

2-7. Network protectors.

The current-carrying parts, main contacts, and op-erating mechanism of a network protector are very

similar to those of the air circuit breaker. This simi-

larity usually ends with the principal mechanical

devices. Unlike the usual feeder circuit breaker, the

network protector is more like a tie circuit breaker;

that is, i t is almost always energized on both sides.

This condition requires that extreme care be taken

during installation or removal of the unit from ser-

vice. The netw ork protector is equipped with specia l

relays t ha t sense the netw ork circuit conditions and

command the mechanism to either open or close

automatically in response to those conditions. Net-

work protectors are used where large amounts ofpower must be distributed to high density load ar-

eas such as commercial buildings and office com-

plexes. To form a network, several incoming power

sources may be connected. As a result, a short cir-

cuit a t a ny point in t he system usua lly involves very

high fault currents.

a. Safety precautions. Due to the construction

and purpose of the network protector, taking it out

of service or placing it ba ck in service is a procedure

that must be done while the circuit is energized.

During this work, always use the special insulated

tools provided with the particular model to be ser-

viced. Alternate or make-shift tools are not recom-

mended unless they have been laboratory tested

and are known to have good safety performance.

Electrical grade, safety gloves should stil l be worn

by the person servicing the unit regardless of the

type or condition of the tools used.

b. M ai ntenance. A routine maintenance schedulefor network protectors should be observed. The fre-

quency of inspection w ill vary based on the location

and environment in which the unit is installed, and



20/180


21/180


the number of operat ions the uni t has made. In a l l

cases, open the circuit first. This is done by moving

t h e c o n t r o l h a n d l e f r o m A U T O M A T I C t o

MANUAL and then manually opening the circuit.

The cont rol ha ndle a nd/or opera tin g mecha nism

should then be locked in th e OP EN position beforefurther work is done. Maintenance should include

cleaning an y a ccumula tion of dust, dirt or corrosion

deposits, a thorough visual inspection, and overall

performance tests. Should the operation of any part

be suspect, refer to the manufacturers instructions

describing operation, adjustment, and replacement

of these parts. I f the network sensing relays are out

of calibration, they should be recalibrated by com-

petent shop personnel. The network protector is

housed in a cell or enclosure similar to those used

for air circuit breakers (fig 2-8). The circuit breaker

mechanism and the network relay panel assembly

of a network protector are usually constructed aa anintegral , drawout uni t which must be withdrawn

fmm the housing for proper maintenance. Removal

is done by unbolting the fuses at the top (usually)

and the disconnecting links at the bottom (some

models have bolt-actuated disconnecting f ingers at

the bottom). After removing any additional lock-

down bol ts or la tches , the drawout uni t may be

carefully withdrawn using the rails provided for

suppor t . Al though th i s prov ides a compara t ive

measure of safety, work should be done cautiously

since there is voltage present within the enclosure.

I t is better to move the unit completely away fromth e enclosure (fig 29). The following inspection a nd

maintenance operations can be done on the drawout

unit :

(1) Clean the breaker assembly. Use of avacuum cleaner is preferred. Use cloth rags free of

oil or grease for removing clinging dirt.

(2) Remove arc quenchers. Replace if damaged.

(3) Inspect main contacts (fig 2-10). Smooth

any heavily frosted area with a very f ine f i le or a

burnishing stone which does not shed abrasive par-

ticles. Protect hinged joints from falling particles

during f iling.

(4) File smooth any especially high projections

of metal on arcing contacts.

(5) See that all electrical connections are tight.

(6) Look for any abrasion of wire insulation

an d repair .(7) Check for signs of overheating of control

wire and current carrying parts .

(8) See that all springs are in good condition

and are properly seated in place.

(9) See that all nuts, pins, snap rings or retain-

ers, and screws are in place and tight.

(10) Replace any broken or missing barriers.(11) With the rollout unit still set aside, per-

form the following maintenance operations inside

the enclosure:

**WARNING**Both source and load terminals are probably still energized. Use insulated tools and safety

protective equipment for this work. Do not remove any barriers from the enclosure.

(a) Look for loose hard wa re on the enclosurebottom or beneath the frame. I f any is found, trace

to source and correct problem or replace.

(b) Clean stand-off bus insulators.

(c) Remove oxide f ilm from t erminal conta ctsi f necessary.

( 1 2 ) M a n u a l l y c l o s e a n d t r i p t h e b r e a k e r

mechanism according to instructions furnished for

the particular model.(13) Perform an operational test using a net-

work protector test kit .

(14) Conduct insulation resistance tests, di-

electric test and electrical operating test in accord-

ance with the manufacturers recommendations.

(15) Carefully replace the drawout unit in theenclosure. Make a f inal inspection to be sure no

control wiring has become snagged, and that no

plugs or connecting surfa ces ha ve been bent or dam -

aged.

2-8. Auxiliary switchgear equipment.

Auxiliary equipment includes devices such as fuses,

capaci tors , meters , relays , etc . This equipment

should be serviced along with the major switchgear

components, unless there is some indication that a

device is being heavily or improperly used, in which

case it should be inspected more often. Protective

relays and meters should be inspected and cali-brated on a scheduled basis. Critical service equip-

ment should have the protective relays checked at

every maintenance turn (annually or according to

manufacturers recommendations). Relays applied

to other general distribution circuits may be done

less frequently (see para 2-8h).

a. Fuses. Fuse maintenance is covered as a sepa-

rate category of electrical equipment (para 5-4d).

b. Capaci tors.

power capacitor

The maintenance requirement on

instal la t ions is so smal l that i ts

2-12



22/180


)INGs

BREAKER UNIT J COUPLING

F i gu r e 2 -8 . Typ i ca l d r a wou t n etwo r k p r o tec t o r and enc l o su r e .

Holes For

M o u n t i n g

Screws

( Two OnEach Side

F i gu r e 29 . Netwo r k p r o tec t o r r emovab l e un i t .

importance is often overlooked. The voltage of the

system at the capacitor location should be checked

at l ight load periods to determine if an overvoltage

condition exists. Any changes in circuit connections,

which may increase vol tage levels , warrant a re-

check of operating conditions. The conductor sizes

should provide for not less than 135 percent of ca-

pacitor current at rated voltage and WA. As a gen-

eral rule, i f the side of the capacitor unit casing is

operating at a temperature above 55 degrees C (131

degrees F a temperature almost too hot for bare-

hand contact) , then a more complete investigationof operating conditions should be made. The case

temperatures should never exceed 65 degrees C

(149 degrees F) under any conditions. Adequate

ventilation is therefore necessary to remove the

heat generated by continuous full-load duty. Re-

move any obstructions at ventilation openings in

capacitor housings to ensure that this ventilation is

maintained. A disconnected capacitor retains its

electrical charge for some time and may even retain

the full-line voltage across its terminals. Therefore

always discharge a capacitor before handling or

making connections. An insulat ion short c ircui tjumper may be used for this purpose; however, it

should only be applied with full knowledge of the

circuit, and with the use of appropriate protective

equipment. Power capacitors are generally provided

with individual fuses to protect the system in case

of a short circuit within the capacitor. In addition to

a faul ty capaci tor , a fuse may be blown by a n a bnor-

mal voltage surge. Check for blown fuses and re-

place them with a type recommended by the manu-

facturer. Do not remove fuses by hand until the

capacitor has been completely discharged. Clean the

case of a capacitor, the insulating bushings, and any

2-13



23/180

TM 5-683/NAVFAC MO-1 16/AFJMAN 32-1083

ARCQUENCHER

BLOWOUT

COIL

ARC

QUENCHERSUPPORTINGSCREWS

SCREWS FORMOVABLE

ARCING

CONTACT

LOCKING

PLATE

FLEXIBLECONNECTION

STOP PINFOR MOVABLE

ARCINGCONTACT

CONTACT

SUPPORT

CROSS BAR

UPPER

CONTACT BAR

MOLDED

SUPPORTFOR ARC

QUENCNER

INSULATION

STATIONARYARCING

CONTACT

MOVABLEARCING

CONTACT

UPPER MAIN

SILVERCONTACTS

STOP SCREW

MAINBRIDGING

CONTACT

BLOCK

LOWERCONTACTBAR

F i g u r e 210. Typ i ca l con t a c t con s t r u c t i o n f o r a n etwo r k p r o t e ct o r .

connections that are dirty or corroded. Inspect the posed connections, and safety gear and tools must

case of each capa citor for lea ks, bulges, or discolora-

tion. I f any of these conditions exist, then replace

th e capa citor (pa ra 112).

c. Ba tt er y suppl i es. Th e contr ol bat tery is such an

importa nt i tem in sw itchgear operat ion t hat i t must

be given strict attention in the maintenance pro-

gra m. The bat tery cha rger plays a critica l role sinceit supplies norma l direct current (DC) power to t he

stat ion and maintains the bat ter ies a t a high level

of charge. The batteries, in addition to supplying

temporary heavy demands in excess of the charger

capacity, serve a s a back-up source to tr ip breakers

upon loss of alternating current (AC) power. Failure

of the charger or i ts AC supply transfers al l DC load

to the batteries. Each battery cell electrolyte levelshould be checked. While a single cell may not pro-

duce a serious shock hazard, when the cells are

connected in a battery bank, a severe shock hazard

may be possible. Also, there are usually many ex-

2-14

be used to the best degree of safety such as face

shields, a cid/caust ic resista nt gloves, emergency

eyewash, etc. Electrolyte is the f luid contained in

each battery cell (fig 211). Low electrolyte levels

indicate too high a charging rate. In this case, the

float-voltage setting of the charger should be

checked against the battery manufacturers recom-mendations. The specific gravity of the battery elec-

trolyte should be taken using a hydrometer (para

14-6). I f the readings between battery cells vary

more than fif ty points on the hydrometer scale, the

battery probably has a bad cell which should be

replaced. If all cells read consistently low (within 50

points), the batt ery should be fully cha rged a nd th e

battery charger checked for proper operation. The

battery top surface should be clean. Surface con-

tamina t ion can produce leakage currents tha tpresent a drain on the charger and the battery. Vent

holes in t he cell ca ps should be open. Ba tt ery t ermi-



24/180

nal connections should be tight and free of corro-

sion. I f the termina l connections a re corroded, they

should be cleaned with bica rbonat e of soda. B a tt ery

terminals and cable ends should be cleaned thor-

oughly. I f stranded cable is used it is advisable to

cut off the corroded end. If this is not possible, the

stra nds should be separa ted a nd c leaned interna l ly .

Any dus t accumula t ion on the ba t tery charger

should be blown off or wiped clean. Ventilation

openings should be clear of obstruction. Terminal

connections should be checked for tightness. All re-

lays, l ights or horns for indicating such abnormal

conditions as grounds, loss of AC power supply, and

high or low voltage should be checked to ensure that

they are operating properly. During maintenance

outages of the AC supply, th ere may be times when

it is necessar y to provide a t empora ry supply to the

TM 5-683/NAVFAC MO-1161AFJMAN 32-1083

charger. While being charged, a battery produces

and emits a mixture of hydrogen and oxygen gases

which is very explosive. Open flames or sparks must

not be permitted in close proximity t o the ba tt eries.

The room or compartment in which operating bat-

teries are located should be well ventilated. Smok-

ing should be prohibited in these rooms or compart-

men ts .

d. I nstrum ent tran sform ers. I n s t r u m e n t t r a n s -

formers are used to step down a current or voltage

in order to operate a meter or a relay. Indoor-type

instrument transformers are normally dry type, ex-

cept potentia l tra nsformers (P Ts) which ma y be en-

closed in compound-filled metal cases. The more

common transformer constructions have the com-

plete transformer molded into one solid mass with

only the t erminals exposed.

I ** CAUTION** I

INever open circui t the secondary winding of a current transformer while energized . To do so

may resul t in component damage or persona l in jury . IVENT AND ELECTROLYTE

FILLING FUNNEL

NEGATIVE (-) TERMlNAL/

POSITPLATE

RUBBER

SEPARAT

IVE-

OR

POSITIVE (+) TERMINAL

ELECT

LEVEL

ROLYTE

LINES

NEGATIVE PLATE

F i gu r e 2 -11. La r ge cel l f o r a s ta t i o na r y ba t t e r y .

2-15



25/180


(11) Verify connection of seconda ry P T leads by

applying a low volta ge to the leads a nd checking for

voltage contribution at applicable devices.

(12) Check for PT secondary load with second-

ary voltage and current measurements. Make sure

load is less t ha n volt a mps (VA) of P T.f. M eteri ng. Most of the buildings in a typical

mili tary instal lation are unmetered. Meters (both

recording and indicating), relays, and associated

equipment are usually part of a substation, main

dis tr ibut ion swi tchboard equipment , or specia l

equipment. Indust rial sh ops a nd other buildings oc-

casionally uti l ize kilowatt hour demand meters,

power factor meters, ammeters, and voltmeters. In

an effort to determine whether the maintenance or

operat ion of these meters is adequa te demands t ha t

the m etering instruments be of th e specif ied ra nge,

accurately calibrated, and adequately serviced. In-

strument accuracy is always expressed in terms ofthe percentage of error at the full-scale point. Maxi-

mum accuracy, consequently, is obtainable by keep-

ing the rating as high on the scale as possible, and

requires a properly rated instrument. An instru-

ment with an accuracy of 1 percent, with a scale

reading of 100 divided into 100 divisions, is accurate

to plus or minus one division. Hence, a reading of 20

has a margin of error of plus or minus one division,

which in th is ins tance means tha t the t rue va lue

could be between 19 or 21an actual variation of 10

percent. If the maximum indicating meter reading

is less tha n 50 percent of the meter r an ge, indicat-

ing meters should be recalibra ted, and ra tchets anddials changed. How often an instrument is cali-

brat ed depends on i ts use and the desired accuracy.

I f ca l ibra t ion s tandards and equipment are not

available, instruments of nearly the same rating

ma y be checked aga inst ea ch other. If w ide discrep-

an cies are n oted, the suspect instrum ent should be

checked by a competent laboratory or returned to

the manufacturer. For many mili tary establish-

ments, the uti l i ty company will best perform this

work. Take care to prevent entrance of dirt or lint

into an instrument because this dirt could hinder

the actuation of the instrument pointer. Clean the

glass with a damp cloth because a dry cloth mayinduce a static charge on the glass and af fect the

Documents

1995 Us Army Facilities Engineering Electrical Interior Facilities 180p