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Electrical - Level 4 > Emerg Power & Renewable Energy > Flashcards

Emerg Power & Renewable Energy Flashcards

1
Q

As a battery discharges, the internal resistance ______?

A

Rises

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2
Q

As a battery becomes more loaded, the terminal voltage will ________?

A

fall

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3
Q

Where are EP systems neccessary?

A

in any facility where a large number of people congregate

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4
Q

What is a cell?

A

devices that convert chemical energy into electric energy

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5
Q

What is a battery?

A

when several cells are connected together

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6
Q

What does the output of a battery depend on?

A

the material within and how they are connected

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7
Q

What is each cell made out of, are they connected and what are they immersed in?

A
  • Made of two different materials called electrodes

- Not connected but immersed in a conductive liquid called electrolyte

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8
Q

What happens when cells are connected in series?

A

Higher voltage is achieved

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9
Q

What happens when cells are connected in parallel?

A

Higher current is achieved

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10
Q

What are batteries rated in?

A

voltage & ampere-hours

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11
Q

What are characteristics of primary cells? What is a dry cell?

A
  • Energy comes from consuming electrodes
  • No recharge
  • Energy is built into these cells
  • Great for portable equipment
  • Dry cell = electrolyte is solid or molten
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12
Q

What are characteristics of secondary cells?

A
  • Also called storage cells, no energy at the beginning

- Rechargeable

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13
Q

What is a wet cell?

A

a secondary cell which has a large capacity

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14
Q

How is a cell recharged?

A

Passing current through in the opposite direction of discharge

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15
Q

What do all batteries have?

A

internal resistance

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16
Q

What is the chemical reaction between charged and discharged batteries?

A 
Charged = Lead dioxide + Sulphuric Acid
Discharged = Lead sulphate + Lead dioxide + Water
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17
Q

What causes the internal resistance to increase during and when the battery is discharged?

A

“Sulphation”

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18
Q

What happens with every discharge cycle?

A

Some residual sulphation is left on the plates causing it to cummulate

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19
Q

What is the best way to test a battery?

A

Load test

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20
Q

What does the Amp Hour specification provide

A

A measurement of battery capacity

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21
Q

How is the Amp Hour calculated?

A

Maximum sustained ampacity drawn from a fully charged battery over a time of 20 hours, to a point where its 100% depth of discharge

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22
Q

What is reserve capacity?

A

another measurement of battery capacity, or how much energy can be stored by the battery

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23
Q

What are cold cranking amps?

A

provides a measurement of the starting power of a battery at -18°C under a load (amps) for 30 seconds with the end voltage maintained at 1.20 VPC

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24
Q

What are start batteries manufactured with? Why?

A

Softer plates which can convert chemical energy to electrical energy much faster than deep cycle batteries

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25
Q

Why do deep cycle batteries not work well for starting applications?

A

they are constructed with hard plates for lengthy discharge times

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26
Q

What is within lead-acid batteries?

A

Lead & Lead dioxide immersed in sulphuric acid

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27
Q

What do both electrodes do when discharging in lead-acid batteries

A

Both turn into Lead Sulphate

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28
Q

What is SLI

A

Starting
Lighting
Ignition

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29
Q

Specific Gravity = ?

A

Relative Density

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30
Q

What happens when charging batteries?

A
  • Plates go back to original material & electrolyte gets stronger
  • Hydrogen gassing may occur thru vents
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31
Q

What would be the charging voltage for a 12V battery?

A

14.2 - 14.5 VDC

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32
Q

How do you determine the level of charge in a battery?

A

check the specific gravity of the electrolyte

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33
Q

what is the specific gravity?

A

amount of acid contained in the water

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34
Q

What tool is used to measure specific gravity?

A

a hydrometer

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35
Q

Explain using a hydrometer and temperature?

A
  • SG readings should be taken at 25°C
  • When temp. falls, we decrease our readings
  • When temp rises, we increase our readings
  • For each degree away from 25, we change our SG reading by 0.7
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36
Q

What is the temperature effect on batteries?

A

High temp. = reduced life and voltage

Low temp = overall shelf life increases

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37
Q

Should plates always be covered in electrolyte? What should you do if battery electrolyte is low due to normal evaporation?

A
  • Yes

- Add distilled water

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38
Q

What should you do if electrolyte is low due to spillage? How should acid and water be mixed?

A
  • Add sulphuric acid ( 3:1 mixture)

- Always add acid to water

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39
Q

How should terminals be cleaned?

A

While wearing rubber gloves and goggles, cleans regularly using baking soda and water

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40
Q

What do you use for representation of health of large battery banks?

A

use pilot cells, 5-7 selected and tested

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41
Q

Nickel-Iron (Ni-Fe) battery characteristics?

A
  • Indestructible
  • Long life (30+ years)
  • Used in mining operations
  • Do not contain hazardous materials
  • Hard time keeping a charge
  • Operate poorly in low temps
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42
Q

Maintenance and testing for Ni-Fe batteries?

A
  • When overcharges, it gasses and loses electrolytes
  • Keep distilled water above plate line
  • Use a DC voltmeter on cells while under load to test
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43
Q

Nickel-Cadmium (Ni-Cd) battery characteristics?

A
  • Improvement from Ni-Fe
  • Hold charge, good life cycle & perform at low temps
  • Thinner plate design made for portable size batteries
  • More expensive than Lead-acid
  • Suffer from memory effect (hold less charge over time)
  • Cadmium is a disaster to humans & environment
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44
Q

Lithium-Ion (Li) battery characteristics?

A
  • Battery of the future

- High energy density, tiny memory effect & low discharge

45
Q

Why can Li batteries be dangerous?

A
  • contain a flammable electrolyte that is kept pressurized

- Prolonged exposure to heat reduces battery life & can lead to “thermal runaway” and cell combustion

46
Q

What do Li battery packs contain?

A

Fail-safe circuitry that disconnects battery when voltage is above cell “safe range”

47
Q

what is normal in charging terms?

A

restores battery after it has been used or sitting

48
Q

what is trickle in charging terms?

A

maintains battery fully charged with no load connected

49
Q

what is float in charging terms?

A

supplies charge to batteries and connected loads

50
Q

what is Bulk in charging terms?

A

restores battery after deep discharge (constant current)

51
Q

what is absorption in charging terms?

A

ensures plates are de-sulphated after bulk (constant voltage)

52
Q

What is equalization in charging terms?

A

elevated charge voltage to equalize cells and remove residual sulphation

53
Q

what is the preferred method of charging for Nickel Cadmium batteries?

A

Constant Current (Bulk)

54
Q

What does constant voltage charging do? What is it used for?

A
  • outputs preset voltage level to prevent overcharging
  • current decreases as charge builds
  • used for ‘basic’ charging of Lead-acid batteries
55
Q

What does the bulk stage provide?

A

desired current until a user preset absorption voltage is reached

56
Q

What happens in Absorption mode?

A

charger goes to constant voltage mode and current tapers off as battery plates become restored and de-sulphated

57
Q

what would continued charging at Absorption do?

A

excessively gas the battery and evaporate the electrolyte

58
Q

Level 1 electric vehicle charger characteristics?

A
  • typically 120V
  • slowest charger (8kms/hour)
  • considered Trickle
59
Q

Level 2 electric vehicle charger characteristics?

A
  • High voltage and current
  • 5-7 times faster than level 1
  • 24-40 km/hour
60
Q

What is the added component in stand-alone AC PV systems?

A

the inverter

61
Q

High quality inverters can give conversion efficiencies of _____?

A

90%

62
Q

What is the most common backup for PV systems?

A

Diesel or Propane generator

63
Q

What are the two types of Grid Connected PV systems?

A
  • Utility Interface

- Utility Interactive

64
Q

Characteristics of Utility Interface?

A
  • Solar energy stored in battery bank
  • Provides some or all of buildings electrical needs
  • Low batteries = building transfer to utility
65
Q

Utility Interactive characteristics?

A
  • No storage

- Excess energy fed to utility grid

66
Q

What is islanding?

A

the undesirable condition where a PV system continues to transfer power to the utility grid during a utility outage

67
Q

what must be done if the utility experiences an outage? Why?

A
  • utility-interactive inverters must stop supplying power to the grid
  • it is an extreme electrocution hazard to any line workers
68
Q

What are benefits of grid connected PV systems?

A
  • Home powered by PV during the day
  • simple to install
  • low capital cost
  • could possibly be paid back for extra energy
69
Q

cons of grid connected PV systems?

A
  • more expensive inverter required

- utility approval process

70
Q

What is net metering?

A

Utility buys power at the same rate they sell it

71
Q

What is dual metering?

A
  • utility may buy power at a different rate than they sell it
  • Records energy flow in both directions seperately
72
Q

What are 4-jaw meter bases used for?

A

single phase applications

73
Q

what are 5-jaw meter bases used for?

A

single phase applications but have a 5th jaw for neutral

74
Q

what is a 7-jaw meter base used for?

A

3-phase applications

75
Q

what are the 3 factors that determine any PV module’s power output?

A
  • load impedance
  • solar irradiance
  • cel temperature
76
Q

What is solar irradiance? How is it measured?

A
  • solar power available per unit area

- measured in watts per square meter

77
Q

what is ‘one sun’ ?

A

Peak irradiance at sea level = 1000 watts/meter squared

78
Q

What are the two conditions modern inverters come in?

A
  • Sine wave

- Modified Square wave

79
Q

Modified square meter characteristics?

A
  • most commonly seen on PV systems
  • Cheaper than sine wave inverters
  • Not as efficient
  • cause more harmonic distortion in a system due to the extra step produced
80
Q

What is a solar tracker?

A

a generic term used to describe devices that orient various payloads towards the sun

81
Q

What is a maximum power point tracker (MPPT) ?

A

a high efficiency DC to DC converter that presents an optimal electrical load to a solar panel or array and produces a voltage suitable for the load

82
Q

What is a closed freon system?

A

a passive tracker that requires no power and accurately tracks the sun throughout the day

83
Q

How much can 10% shade coverage of an array reduce the output by?

A

90%

84
Q

How is Azimuth measured?

A

from the north

85
Q

What is a pyranometer? what is it measured in?

A

a sensor that measures the solar radiation flux density from a field of view of 180°
Measured in watts per square meter

86
Q

What is a pyranometer used to measure?

A

solar irradiance on a planar surface

87
Q

What is a pyrheliometer?

A

an instrument for direct measurement of solar irradiance

88
Q

What are building-integrated photovoltaics (BIPV) ?

A

photovoltaic materials used to replace building materials in parts of the building envelope such as the roof, skylights or facades

89
Q

Stand-by power supplies come in three forms, what are they?

A
  1. Dual Radial Feeds
  2. Batteries & UPS
  3. Emergency Generators
90
Q

How are generators brought online? What is the best fuel?

A

They can be started, then switched to critical loads using an automatic transfer switch
Can take 8-15 seconds to be brought online
Best fuel is Diesel

91
Q

What are some installation tips to be considered when installing generators?

A
  • Locate as close as possible to main supply
  • Mount on vibration pads
  • Avoid areas of high or low temps.
  • Adequate fueling must be available
92
Q

Where are control panels typically mounted?

A

Alternator end of generator

93
Q

What should have alarms?

A

everything (oil, coolant)

94
Q

What 4 things must be the same for generators to be paralleled?

A
  1. Terminal Voltage
  2. Frequency
  3. Phase Sequence
  4. Phase displacement
95
Q

What must synchronized units have? Why?

A

Reverse Power Relays
If one generator goes into speed droop, it will be unable to pick up its share of the load and will act like a load itself

96
Q

How often should the generator be ran in preparation for a real emergency?

A

at least 30 mins per week and at least under 40% load-full is possible

97
Q

What do Automatic Transfer switches provide?

A

“break before make” switching

98
Q

What does break before make switching ensure?

A

the two sources are always isolated

99
Q

How does a Closed Transition Transfer Switch work?

A

overlaps the two sources for .1 seconds, not long enough to do any damage and no line “bump”

100
Q

How do you lockout a generator and transfer switch for maintenance?

A
  • Place ATS selector switch in STOP
  • Disconnect batteries at generator
  • Open and lock-out the CB of generator
  • Turn off normal power and perform shutdown
101
Q

What components does a typical MicroHydro power system contain? (6)

A
  1. Water Intake
  2. Canal
  3. Forebay tank
  4. Penstock
  5. Powerhouse
  6. Tailrace
102
Q

What does the turbine control do?

A

ensures power always flows out from the generator to the system

103
Q

What is a benefit of run of river generation?

A

requires much less flooding

104
Q

What is SCADA?

A

supervisory control and data aquisition

105
Q

what does wild AC in micro-hydro power generation allow?

A

low speed / low head water turbines to be competitive

106
Q

What is a Hydrokinetic power system?

A

a system consisting of one or more hydrokinetic turbines that convert kinetic energy of flowing water into electrical energy

107
Q

What are some advantages and disadvantages of hydrokinetic systems?

A

Advantages:

  • More predictable than wind power
  • No retaining structure
  • Discreet or even invisible

Disadvantages:
- Winter operations possibly problematic

108
Q

What are the 3 types of hydrokinetic turbines?

A
  1. Vertical-axis
  2. Horizontal-axis
  3. Oscillating-foil

Electrical - Level 4 (8 decks)

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