Flashcards in Electrical Power Deck (41)
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1
What is electrical demand?
A measurement of power, in kW, based on a customer's highest use within a given unit of time.
2
What is contract demand?
The addition of all of a utilities customer demand so that they can estimate the maximum overall generating capacity they need to provide.
3
Electric utilities sell two products:
Usage and demand
4
What is Usage?
The overall flow of electricity over time, in kWh
5
What is Demand?
The simultaneous use of power, in kW. Demand becomes the load the utilities must provide.
6
What is peak demand?
The most power, in kW, used over a specific time period.
7
T/F Most medium and large commercial customers pay for demand.
True
8
What is Load Factor?
The relationship between kWh consumption and kW demand for the same billing period. It describes the profile of the electrical use of a facility.
9
Load factor for a given time period =
Average kW in time period / Peak kW in time period
10
Average kW =
Total kWh / # of hours in time period
11
A high load factor means power use is relatively ______.
constant
12
A low load factor means power use is ________.
inconsistent, with high and low peaks.
13
For an industrial facility, a ____ load factor is ideal.
high
14
What are baseload plants?
Power plants that operate constantly to provide the minimum amount of power needed around the clock.
15
What are some typical baseload plants?
Coal, natural gas, nuclear, hydroelectric dams, geothermal, biomass
16
What are intermediate plants?
Power plants that operate daily or seasonally to follow the large but predictable swings in demand. Dispatched during baseload outage or maintenance.
17
What are some typical intermediate plants?
Natural gas, hydroelectric, solar thermal, solar VP, wind farms
18
What are peaking plants?
Power plants that are used only sporadically and for short periods of time to accommodate peak demand that exceeds the intermediate plants.
19
What's the most expensive type of plant to run?
Peaking plants, because they sit idle most of the year.
20
What are some typical peaking plants?
Natural gas, oil and diesel generators, hydroelectric dams
21
How much excess capacity beyond peak needs are utilities required to have as a margin of safety?
10-20%
22
What are Demand Side Management strategies?
Strategies offered or incentivized by utilities to reduce the power use of its customers during time of extreme demand, done cooperatively.
23
What are some DSM strategies?
Large lighting, motor, or HVAC retrofits, rescheduling large loads to off-peak hours, interruptible loads, curtailable loads,
24
What's an interruptible load?
One that the utility can remotely turn off at certain times of the day or year during peak times. The customer is offered a financial incentive, like a yearly rebate.
25
What's a curtailable load?
One that a customer is willing to turn off if given sufficient notice by the utility. They work best for manufacturing facilities with significant inventory.
26
What is Alternating Current (AC)?
The electrons oscillate between positive and negative voltage, relative to ground. The higher the voltage, the higher the sine wave.
27
What is three-phase voltage?
Three separate lines carry the electricity and the AC voltage in each line is offset 1/3 from each other, allowing for a more constant power generation.
28
What percentage of all electricity produced is lost in transmission due to the resistance of the wires?
7%
29
What are substations?
Stations where voltage is stepped down to lower levels that can be safely distributed by local distribution lines to each customer.
30
