Section 7 Protective Devices of Electrical Equipment

701. General

1. Electrical equipment is to be protected against accidental overcurrents including short-circuit. The protective devices are to be capable of continuously servicing other circuits which are used for the electrical source and/or other important feeder circuit as far as practicable by breaking fault circuit and to be capable of eliminating damage to the systems and hazard off fire.

2. Circuit-breakers and fuses used for the protective devices are to comply with the requirements in

Pt 6, Ch 1, Sec 8 of the Rules or equivalent thereto.

702. Protection against short-circuit

1. Short-circuit protection is to be provided in each live pole of a direct-current system and in each phase of an alternating current system.

2. Circuit breakers and fuses for used by protective device are to comply with the requirements in Pt 6, Ch 1, Sec 8 of the Rules or the equivalent above. 【See Guidance】

703. Protection against overload

1. Overload protection is to be provided in the following line or phase;

(1) Two-wire D.C. or single-phase A.C. system-at least one line or phase.

(2) Three-wire D.C. system-both outer lines.

(3) Three-phase A.C. system-at least two phase.

2. Tripping characteristics of overload protective devices(blowing out characteristics for fuse) are to be adequate for the thermal capacity of the electrical equipment and wirings protected.

704. Protection of generators

1. Generators are to be protected against short-circuit and overcurrent by a multipole circuit-breaker ar- ranged to open simultaneously all insulated poles. In the case of generators less than 50 kW and

not arranged to operate in parallel, they may be protected by a or a circuit breaker in each insulated pole.

2. In the case of generators arranged to operate in parallel, they are

multipolelinked switch with fuses

to be provided with reverse pow-

er protection for A.C. system or reverse current protection for D.C. system.

78 Rules for the Classification of Steel Barges 2015

705. Protection of motors

Each motor used for important system is to be protected from short-circuit and overload. protective device of motor is to have a delay characteristic to enable the motor to start.