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Test stuff > NSTM Chapter 300, Electric Plant - General > Flashcards

NSTM Chapter 300, Electric Plant - General Flashcards

1
Q

For repair activity work conducted shipboard not IAW NSTM Chapter 300, a ___ between shipyards/repair activities and Ship’s Force

A

Memorandum of agreement must be documented

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2
Q

For naval applications, voltages greater than or equal to ___ are considered high voltage

A

1000 volts

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3
Q

The resistance of a human body is about ___

A

500 ohms

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4
Q

When the skin is damp the resistance of a human body is about ___

A

300 ohms

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5
Q

A situation where electrical current passes through air gaps between ungrounded conductors or between conductors and grounded components

A

Arc flash

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6
Q

Another product of an arc flash is the incident energy, which is ___

A

Radiant energy

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7
Q

Radiant energy is expressed in ___

A

Calories per centimeter squared (cal/cm^2)

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8
Q

Threshold for a second degree burn

A

1.2 cal/cm^2

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9
Q

Threshold for a third degree burn

A

10.7 cal/cm^2

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10
Q

Two major hazards with an arc flash

A

Arc temperature

Incident energy

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11
Q

Occurs when the severity of an arc or short circuit current causes destructive heating and explosive vaporization of both the surrounding air and the metal in the current path

A

Arc blast

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12
Q

The unobstructed distance from exposed energized circuits within which unprotected skin could receive a second degree burn if an arc flash were to occur

A

FPB

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13
Q

FPB

A

Flash Protection Boundaries

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14
Q

The FPB distance aboard a ship for 450-volt circuits is ___

A

4 feet

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15
Q

The FPB distance aboard a ship for 4160-volt circuits is ___

A

11 feet

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16
Q

The FPB distance aboard a ship for 13.8K volt circuits is ___

A

13 feet

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17
Q

An FPB of 4 feet is applicable to circuits with rated voltages between ___

A

30-1000 volts

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18
Q

An FPB of 11 feet is applicable to circuits with rated voltages between ___

A

1000 to 5000 volts

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19
Q

An FPB of 13 feet is applicable for voltages ___

A

Greater than 5000

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20
Q

The FPB does not need to extend past ___

A

Permanent solid structure

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21
Q

Intentionally connects the non-current carrying conductive parts of electrical equipment, such as the enclosure, frame, or chassis, to ground through a low-resistance path

A

Equipment grounding

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22
Q

The purpose of equipment grounding

A

If energized electrical conductor contacts the enclosure due to fault or damage, it shunts the current away from possible human contact

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23
Q

Grounding of metal enclosing cases, bases, frames, and structural parts of electrical equipment shall be IAW ___

A

MIL-STD-1310 and MIL-E-2036

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24
Q

On metallic hull ships, grounds can be provided by the fact that the metal enclosing cases or frames are ___

A

In contact with one another and the metal structure of the ship

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25
Q

A ground must be provided for equipment mounted on a hinged door if the voltage exceeds ___

A

30 volts

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26
Q

Resistance to ground should be less than ___

A

0.1 ohm

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27
Q

___ systems provide a limited amount of current when one phase is faulted to ground, and thus allows critical equipment to continue operation until steps can be taken to remove the fault

A

Ungrounded

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28
Q

___ system designed so that a phase conductor fault to ground will produce high current and quickly trip the circuit breaker or blow the fuse

A

Grounded neutral

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29
Q

Electric utility service for wiring ashore uses ___ system

A

Grounded neutral

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30
Q

___ system is isolated from the ungrounded power system at the upstream supply transformer

A

Grounded neutral receptacle

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31
Q

Some ships use ___ for improved personnel safety over that which standard circuit breakers provide

A

Ground fault current interrupt equipment

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32
Q

Both conductors of a shipboard receptacle have a ___

A

Potential between the conductors and the ground

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33
Q

Ashore receptacles has one ___

A

Neutral conductor which is connected to ground at the source

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34
Q

The resistances of an ungrounded system when ___, form the insulation resistance of the system

A

Combined in parallel

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35
Q

Insulation resistance of the system is measured using ___

A

500-volt DC megger or installed ship’s active ground detector

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36
Q

Contain capacitors connected from the conductors to the ground

A

Electromagnetic Interference Filters

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37
Q

Used to reduce interference to shipboard electrical and electronic equipment

A

Electromagnetic interference filters

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38
Q

Ungrounded high voltage power systems have a high failure rate due to ___

A

Transient overvoltage surges

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39
Q

The surges in an ungrounded high voltage power system is the result from ___

A

Oscillations that occur because of the system’s inherent inductance and capacitance

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40
Q

Ships with electrical systems rated ___ are designed with high resistance grounding subsystems

A

1000 volts and above

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41
Q

High resistance grounding subsystems are normally contained within an enclosure with ___

A

A three-phase transformer connected in a wye/delta configuration with an open delta secondary. A resistor is connected across the open delta secondary

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42
Q

Absorbs and clamps voltage spikes on the main AC bus

A

Transient voltage surge suppression systems

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43
Q

Arc Fault Detection systems are installed on ___ where they ___

A

Switchboards and load centers

Continuously monitor the interior of these enclosures for arcing faults

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44
Q

Arc fault detection systems can sense ___

A

Pressure, gassing particles, and light

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45
Q

AFD systems consist of ___

A

Pressure sensors, thermal ionization detectors, photo sensors, and control units that monitor the sensors

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46
Q

In an AFD system the thermal ionization detector is associated with ___

A

The continuous thermal monitor system

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47
Q

In an AFD system the control circuitry requires ___ to indicate the presence of an arc and trip the switchboard isolation

A

Both a photo sensor and its corresponding pressure sensor

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48
Q

Do not join extension cords longer than ___ together

A

25 ft

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49
Q

Never join more than ___ extension cords together

A

2

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50
Q

Extension cords up to ___ are permissible

A

100 ft

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51
Q

___ use silicon-controlled rectifiers vice mechanical contacts to provide dual power supplies to individual loads

A

Static automatic bus transfer switches

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52
Q

Electrical systems require a minimum of ___ isolation points in each conductor isolation path

A

One

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53
Q

All electrical work should be approached with a focus on ___

A

What could go wrong

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54
Q

CO permission is not required when performing ___

A

IVV or safe-to-work voltage checks

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55
Q

The safety observer for work on energized circuits must ___

A

Be trained in first aid, know what breaker isolates the system and be ready to operate it immediately, and not engage in any distracting behavior

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56
Q

For work on energized circuits greater than ___ a safety line shall be attached to the worker

A

300 volts

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57
Q

IVV

A

Initial Voltage Checks

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58
Q

When shorting a capacitor to drain the charge it should be done ___

A

Three times about ten second apart

59
Q

When energized wiring and non energized wiring are located in close proximity to each other

A

Capacitive coupling

60
Q

Detecting stray voltage using Simpson 260 the reading should be ___

A

Less than fill scale deflection on the 2.5V scale

61
Q

Detecting stray voltage using DVM set to low impedance mode or Fluke stray voltage eliminator installed the reading should be ___

A

Less than 3 volts

62
Q

Capacitive storage is verified as indicated by ___

A

Minimum of 5 seconds with steadily decreasing voltage indication

63
Q

To dissipate capacitor stored energy the ground must have a reading of ___

A

Less than 0.1 ohm

64
Q

Do not approach or take a conductive object without an approved insulating handle closer than ___ to potentially energized exposed equipment without proper PPE

A

2 ft

65
Q

Establish an electrical safety and arc flash area while checking that ___ equipment is deenergized

A

Greater than 1000 volts

66
Q

Proximity voltage tester must be ___ from equipment being tested

A

8 inches or closer

67
Q

STW

A

Safe-to-work

68
Q

If all circuits are ___ STW checks are not required

A

30 volts or less

69
Q

Safety devices installed in power and lighting circuits and in control circuits to protect the equipment and circuits from damage due to excessive current

A

Fuses

70
Q

Silver plated fuses develop a ___ over time that does not affect performance

A

black oxide coating

71
Q

SIlver plated fuses are designated by ___

A

The letter S following the current rating of the fuse

72
Q

If the replacement fuse blows, then ___

A

A fault probably exists

73
Q

___ before replacing a fuse

A

Deenergize the circuit

74
Q

Do not use ___ to grab a fuse that remains in the fuse barrel when the fuseholder is removed

A

A bare hand

75
Q

For circuits ___ or less, fuses may be removed or replaced without deenergizing the load

A

10 amps

76
Q

Some indicator types of panel mounted fuse receptacles contain riveted connections that carry current. These connections are required to be ___

A

Soldered to achieve a low-resistance connection

77
Q

A draw-out type circuit breaker uses a ___ to remove

A

Racking mechanism

78
Q

The imaginary plane formed by the opening of an electrical enclosure

A

Electrical safety plane

79
Q

If electrical components are mounted on the door, then the plane includes ___

A

The arc formed by the doors edge as it swings open

80
Q

No precautions are required for visual inspections of equipment or circuits rated ___ or less

A

30 volts

81
Q

For visual inspections, erect a barrier at least ___ from the electrical plane of the equipment

A

2 ft

82
Q

Minimum PPE to wipe water off of equipment

A

Rubber gloves

83
Q

Have an attached cord, are hand-held or frequently handles while operated, and are plugged into an electric power receptacle

A

Portable electrical tools and devices

84
Q

A unit that is not hard-wired, can be moved, but normally is stationary while operating

A

Mobile electrical equipment

85
Q

Equipment brought onboard by the owner for personal use

A

Personal electrical equipment

86
Q

Use rubber gloves when using metal-cased tools that are not marked as ___

A

Double insulated

87
Q

When performing work that could tear the rubber gloves ___

A

Wear leather gloves over them

88
Q

If damage or defects are found in portable cord and plug-connected hand-held equipment and cords, then ___

A

Remove from service, and turn it into tool issue or the electrical safety officer

89
Q

Isolated receptacle units are isolated from ___ by ___

A

The main power distribution system

Transformers

90
Q

Isolated power receptacles circuits are limited in length to reduce the ___ to an acceptable level

A

Line-to-ground capacitance

91
Q

Isolated power receptacles limit ground leakage to less than ___

A

10 mA

92
Q

Refers to the existence of two separate insulating systems within a tool or device

A

Double insulated

93
Q

The term “double insulated” stamped on a device is a ___ designation

A

Underwriters Laboratories (UL)

94
Q

Computer power strips of the marine type must have ___

A

A metal case, double-pole switch/circuit breaker, and dual thermal fuses. Must provide both common and normal mode protection and be listed by a nationally recognized testing laboratory

95
Q

Marine power strips have the commercial item description of ___

A

A-A-50622

96
Q

If the power cord must be more than 25 ft long, the equipment must be ___

A

Permanently mounted and hard-wired

97
Q

Commercially available mobile electrical equipment must not be used aboard ship unless ___

A

They have been approved for shipboard use

98
Q

Three-conductor flexible cables should be ___

A

Type SO or ST, black, white, and green

99
Q

The length of power cords for high-current equipment should be ___

A

Only as long as required

100
Q

Testing of electrical equipment other than visual inspections should be done in a workshop equipped with ___

A

An electrically safe work bench and insulating rubber deck covering

101
Q

Grounding conductors shall be ___ and have minimum cross-sectional area of ___

A

Stranded

9000 circular mils (AWG #10)

102
Q

The conduction of electricity across the surface of a dielectric

A

Creepage

103
Q

The shortest distance between two conductors or between a conductor and ground, measured along the surface of the insulating material

A

Creepage distance

104
Q

By increasing the creepage distance, the creepage current is ___

A

Reduced

105
Q

In order to use air as insulation, a solid insulating material must be used for ___

A

Support to maintain the required air-spacing distance between uninsulated conductors

106
Q

Insulation systems are classified by temperature because ___

A

Temperature has the predominate effect of insulation life

107
Q

Insulation life will decrease by one half for every ___ above the specification limit

A

10 - 15 degrees C (50 to 59 degrees F)

108
Q

Class B or F insulation systems: maximum temperature rise

A

120 degrees C minus (nameplate max ambient)

109
Q

Class H insulation systems: maximum temperature rise

A

145 degrees C minus (nameplate max ambient)

110
Q

Class N insulation systems: maximum temperature rise

A

170 degrees C minus (nameplate max ambient)

111
Q

For top-curved surfaces having a radius greater than 3 inches and for top-flat surfaces, surface creepage distance shall be increased ___ where these surfaces have irregularities which permit the accumulation of dust and moisture

A

33%

112
Q

Three methods of taking temperatures in wiring

A

Thermometer
Resistance
Infrared

113
Q

The ability to withstand potential difference and is usually expressed in terms of voltage at which the insulation fails due to electrostatic stress

A

Dielectric strength

114
Q

Maximum dielectric strength values can be measured only by ___

A

Testing to destruction

115
Q

Two reasons for using an ungrounded power system aboard a ship

A

Improve reliability of power

Prevent galvanic corrosion

116
Q

Insulation resistance should be verified in reference to the ___ in which the winding is embedded, between ___, and between ___

A

Metallic structure
Individual windings on the same component
Isolated brush rigging polarities

117
Q

When testing rotor windings, the test voltage should be applied between the copper conductors and a metallic part of the rotor rather than the ___ in order to ___

A

Stator

Eliminate the insulating effect of oil in the bearings

118
Q

For portable tools, appliances, and cable assemblies, measure the insulation resistance of each line terminal to the ___ and to the ___

A

Equipment frame

Metal shell of the equipment plug

119
Q

The ratio of the 10 minute insulation resistance value to the 1 minute insulation resistance value

A

Polarization Index

120
Q

The polarization index test is useful for ___

A

Appraising the cleanliness and dryness of a winding

121
Q

Insulation resistance of a winding will normally ___ with the duration of the test voltage

A

Increase

122
Q

The measured insulation resistance of a dry winding in good condition will reach a fairly steady value in ___

A

10 to 15 minutes

123
Q

The measured insulation resistance of a wet or dirty winding will reach a fairly steady value in ___

A

1 or 2 minutes

124
Q

For most equipment, the minimum acceptable value of polarization index is ___

A

2.0

125
Q

Following a DC high-potential test, hold the ground for at least ___

A

Four times the accumulated test period or 1 hour, whichever is longer

126
Q

Perform a ___ before a high-potential test

A

500 volt megger

127
Q

No more than ___ AC high-potential tests should be made during the repair process

A

One

128
Q

An electronic device designed specifically to stress the whole winding’s insulation system by applying a series of pulses between turns of a coil, between coils, between phases of two windings or two legs of a winding, and from the windings to ground to detect short circuits

A

Surge tester

129
Q

Two methods of sealing an explosion-proof enclosure

A

Completely filling the voids with liquid

Hermetic sealing

130
Q

Being incapable of releasing sufficient electrical energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture

A

Intrinsically safe equipment and circuits

131
Q

The ___ of paint from electrical equipment should be avoided

A

Removal

132
Q

Repainting of electrical equipment should be done only when ___

A

Necessary to prevent incipient corrosion due to lack of paint

133
Q

Paint should never be applied to any ___ in electrical equipment

A

Insulating surfaces

134
Q

Water piping near electrical equipment should be ___

A

One continuous length

135
Q

Rule of thumb for using electric lamps to keep equipment dry is to provide ___ for each ton of machine weight

A

100 watts

136
Q

The temperature in the secured equipment should be kept about ___ above the ambient air temperature

A

2.8 to 5.6 degrees C (5 to 10 degrees F)

137
Q

Desiccant should be composed of ___

A

Silica gel or clay

138
Q

___ desiccant is required with machines that use carbon brushes

A

Clay

139
Q

Silica gel desiccant will cause carbon brushes to ___

A

Deteriorate rapidly

140
Q

Bags of desiccant are never to be placed inside a ___

A

Motor enclosure

141
Q

Transparent plastic sheet to wrap secured equipment should be at least ___ thick

A

4 mils

142
Q

When the relative humidity reaches ___, the desiccant should be replaced

A

40%

143
Q

Core testing is mandatory for all motors requiring ___ when repairs are accomplished

A

Rewind

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