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( ) is the working grounding.

A. Grounding of potential transformers’ iron core
B. Grounding of current transformers’ iron core
C. Grounding of electrical welding machine
D. Grounding of transformers’iron core

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For three-phase insulated power systems, in order to prevent the risk of personal electric shock, measures ( ) are generally adopted for necessary electrical equipment.

A. working grounding
B. protective grounding
C. protective neutral line connection
D. shield grounding

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For a fluorescent lamp with a rated voltage of 220V, the starting voltage (the minimum voltage required to light the fluorescent lamp) and the extinguishing voltage (the highest voltage required to extinguish the fluorescent lamp) are generally around ( ).

A. 200V and 200V
B. 200V and 100V
C. 100V and 200V
D. 100V and 100V

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Many ships have two types of emergency lighting systems: emergency power system and temporary emergency power system. In terms of power distribution, emergency power system ( ).

A. is a part of normal lighting system
B. can only be powered by an emergency generator
C. no power distribution switch for branch line
D. no control switch for lighting equipment

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In order to ensure the maximum continuous power supply of the marine electrical power system, the operating value setting principle of the short-circuit protection appliances at all levels of the power grid is: step by step towards the generator, the so-called "( )" principle.

A. automatic unloading device
B. inverse time limit
C. sensitivity
D. selectivity

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( ) is the working grounding.

A. Grounding of potential transformers’ iron core B. Grounding of current transformers’ iron core C. Grounding of electrical welding machine D. Grounding of transformers’iron core

For three-phase insulated power systems, in order to prevent the risk of personal electric shock, measures ( ) are generally adopted for necessary electrical equipment.

For a fluorescent lamp with a rated voltage of 220V, the starting voltage (the minimum voltage required to light the fluorescent lamp) and the extinguishing voltage (the highest voltage required to extinguish the fluorescent lamp) are generally around ( ).

Many ships have two types of emergency lighting systems: emergency power system and temporary emergency power system. In terms of power distribution, emergency power system ( ).

In order to ensure the maximum continuous power supply of the marine electrical power system, the operating value setting principle of the short-circuit protection appliances at all levels of the power grid is: step by step towards the generator, the so-called "( )" principle.

A. Grounding of potential transformers’ iron core
B. Grounding of current transformers’ iron core
C. Grounding of electrical welding machine
D. Grounding of transformers’iron core