[Code of Federal Regulations]

[Title 46, Volume 4]

[Revised as of October 1, 2005]

From the U.S. Government Printing Office via GPO Access

[CITE: 46CFR111.12-11]



[Page 219-220]

 

                           TITLE 46--SHIPPING

 

   CHAPTER I--COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)

 

PART 111_ELECTRIC SYSTEMS_GENERAL REQUIREMENTS--Table of Contents

 

           Subpart 111.12_Generator Construction and Circuits

 

Sec. 111.12-11  Generator protection.



    (a) Applicability. This section applies to each generator except a 

propulsion generator.

    (b) General. Each ship's service generator and emergency generator 

must be protected by an individual, tripfree, air circuit breaker whose 

tripping characteristics can be set or adjusted to closely match the 

generator capabilities and meet the coordination requirements of Subpart 

111.51. Each circuit breaker must contain the trips required by this 

section.

    (c) Type of trips. A circuit breaker for a generator must:

    (1) Open upon the shutting down of the prime mover;

    (2) Have longtime overcurrent trips or relays set as necessary to 

coordinate with the trip settings of the feeder circuit breakers; and

    (3) Not have an instantaneous trip with the exception that an 

instantaneous trip is required if:

    (i) Three or more alternating-current generators can be paralleled; 

or

    (ii) The circuit breaker is for a direct current generator.

    (d) Setting of longtime overcurrent trips. The pickup setting of the 

longtime overcurrent trip of a generator circuit breaker must not be 

larger than:

    (1) 115 percent of the generator rating for a continuous rated 

machine; or

    (2) 115 percent of the overload rating for a machine with a 2-hour 

or greater overload rating.

    (e) Setting of instantaneous trips. The instantaneous trip of a 

generator circuit breaker must be set above, but as close as practicable 

to, the maximum asymmetrical short circuit available from any one of the 

generators that can be paralleled.

    (f) Reverse-power and reverse-current trips. Each generator arranged 

for parallel operation must have reverse-power or reverse-current trips.

    (g) Location. A ship's service generator overcurrent protective 

device must be on the ship's service generator switchboard. The 

generator and its switchboard must be in the same space. (For the 

purposes of this section, the following are not considered separate from 

the machinery space: (1) A control room that is inside of the machinery 

casing and (2) a dedicated switch-gear and semiconductor rectifier (SCR) 

compartment on a mobile offshore drilling unit that is separate from but 

directly adjacent to and on the same level as the generator room).

    (h) Three-wire, single-phase and four-wire, three-phase generators. 

There must be circuit breaker poles for each generator lead, except in 

the neutral lead.

    (i) Three-wire, direct-current generators. Each three-wire, direct 

current generator must meet the following requirements:

    (1) Circuit breaker poles. There must be separate circuit breaker 

poles for the positive and negative leads, and, unless the main poles 

provide protection, for each equalizer lead. If there are equalizer 

poles for a three-wire generator, each overload trip must be of the 

``Algebraic'' type. If there is a neutral pole in the generator circuit 

breaker, there must not be an overload trip element for the neutral 

pole. In this case, there must be a neutral overcurrent relay and alarm 

system that is set to function at a current value not more than the 

neutral rating.

    (2) Equalizer buses. For each three-wire generator, the circuit 

breaker must protect against a short circuit on the equalizer bus.



[[Page 220]]



    (j) Circuit breaker reclosing. Generator circuit breakers must not 

automatically close after tripping.



[CGD 74-125A, 47 FR 15236, Apr. 8, 1982, as amended by CGD 81-030, 53 FR 

17847, May 18, 1988; CGD 94-108, 61 FR 28277, June 4, 1996; 62 FR 23908, 

May 1, 1997]