€h 10 - Power Distribution Flashcards
10-1 Power Distribution
Electrical shock =
Cause of injury and death
10-4 Phase difference:
Two waveforms match each other in electrical degrees =
“In phase”
10-7 Distribution
Serving utility and the customer’s site =
Distribution system
10-9 Ohm’s Law
V =
(2)
* Voltage
* IR
10-9 ohms law
I =
(2)
* current in amperes
* V/R
10-9 ohms law
R =
(2)
* resistance in ohms
* V/I
10-9 ohms law
Formulas to calculate power in W =
Except W = RV, does not belong
10-10 ohms law
Ohms law always applies =
(dc)
10-10 ohms law
When (V) and (I) are known =
Z = sqrt of V/I
10-10 ohms law
When (R) and reactance (X) are known =
Z = sqrt of (R^2 + X^2)
10-10 ohms law
When (R), inductive reactance (XL), and capacitive reactance (XC) are known =
Z = sqrt of {R^2 + [X (L) - X (C)]^2}
10-10
Inductive reactance =
Magnetic
10-10
capacitive reactance =
Electric
Fig 10.9
Resistive load
Fig 10.10
Inductive circuit
Fig 10.11
Capacitive load
10-13 watt hours
18,500 kWh x 24hrs x 30days = 1332.00 kWh
Cost per usage = $0.075
1332.00 kWh x $0.075 = $99
10-13 watt hours
2,000 W x 24 hrs x 365days = 17,520,00 watt-hours or kWh
Cost per usage = $0.08 per kWh
$0.08 x 17,520 kWh = $1,401.60
10-14 Heat
One watt is equal to =
3.413 Btu/hr
10-14 Heat
Watts x 3.413 =
Heat dissipated in Btu
10-14 Heat
Btu/12,000 =
Tons of air conditioning required to maintain ambient temperature
10-14
Horsepower =
Unit of mechanical power
10-16
AWG =
(2)
* American wire gauge
* accepted world wide
10-16 AWG numbering system
Sizes in the AWG =
(3)
* Number of steps
* smaller # = larger wire
* larger # = smaller wire
10-16 solid conductor range
AWG range =
36 AWG to 4/0
10-17
circular mils =
Larger than 4/0
10-20 voltage and current fluctuations
Transients/Surge =
Rapid increase
10-20 voltage and current fluctuations
Swell =
Increase .05 cycles to one minute
10-20 voltage and current fluctuations
Sag =
Decrease 0.5 cycles up to one minute
10-20 voltage and current fluctuations
Interruption =
Total absence
10-21 ac voltage quality problems
Solid-state equipment =
Cause harmonics
10-22 isolated ground (IG)
IG receptacles =
Orange triangle
10-24 oversized transformers
K-rating =
(2)
* Transformer’s ability to safely dissipate heat
* Higher k-rating the better the transformer
10-31 tier classification N-Base requirement
(N) =
Need, or no redundancy
10-39 devices that filter/regulate utility lines
Voltage regulators =
Adjust the line voltage
10-39 devices that filter/regulate utility lines
Harmonic filters =
Reduce voltage
10-39 generator equipment
Motor generators =
Using the utility to drive a motor
10-39 generator equipment
Engine generators =
Futile-powered engine
10-53 direct current (dc) power
Telecommunications the nominal operating voltage =
U.S. is -48V
10-53 direct current (dc) power
Cellular radio the nominal operating voltage =
+24V
10-55 dc power
Rectifier/charger =
Charges the battery
10-56 dc power
LVD =
(2)
* low-voltage disconnect
* disconnect the battery
10-65 installation of (dc) systems
Terminating - do not mix aluminum =
Copper cable
10-66
Batteries =
Store energy
10-66 Batteries
Three main types of batteries =
* alkaline
* flooded
* valve regulated
* except zinc oxide, does not belong
10-66 cells
Cells can be connected in parallel =
Increase battery capacity, 5 times
10-67 alkaline cells
Common type of alkaline cell =
NiCd cell
10-67 cells
lead-acid cells =
Cell of choice
10-67 cells
Gases =
A min. of four changes of room air per hour
10-73 parallel cells
Five parallel =
Not recommended
10-73 temperature
Operating temperature of battery =
77 degrees
10-74
Battery clearance =
3.28ft
10–75 battery room considerations
Avoid =
* exposing the battery plant to direct sunlight
* placing the battery adjacent heating or cooling sources
