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Electrical Grid 1 > Chapter 7 > Flashcards

Chapter 7 Flashcards

Substations

1
Q

What are other names for Substations?

A

Power Station or Supply Station

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2
Q

Common description of Substation

A

Fenced enclosure with large equipment inside and several power lines coming in and out of the station.

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3
Q

Common location of substations

A
  • 1-10 acres of land owned by a utility.

- Geographically located where it can most effectively perform its functions

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4
Q

What are the three major functions of Substations?

A
  • Change the voltage of circuits from one level to another
  • Connect or disconnect lines or equipment from each other
  • Control the flow of power by adjusting the voltage and current
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5
Q

What are some Substations limited to?

A

Some Transmission Stations only have equipment that can connect or disconnect lines or equipment from each other and they are commonly referred to as Switching Stations.

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6
Q

What are Generation Stations designed to do?

A

Generation Stations are designed to Step Up the voltage that is produced by the generators of a power plant so it can be transported to where it will be used.

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7
Q

Where is the Generation Station located?

A

Adjacent to the Generating Plant

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8
Q

What are Transmission Stations designed to do?

A

Transmission Stations are typically installed to change the voltage levels to help integrate a system.

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9
Q

Common properties of a Transmission Station?

A
  • Several Transmission lines coming in and out
  • 500kV to 230kV
  • Large Power Transformers & Circuit Breakers
  • Equipment to control the Voltage and Current
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10
Q

Common properties of Subtransmission Stations?

A
  • Typically located near load centers
  • Main function is to change voltage from a higher Transmission Line Voltage
  • Example 345kV Transmission to 69kV Subtransmission to then be distributed to a Distribution Substation within a load center
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11
Q

Where are Distribution Substations located?

A
  • In the middle of a load center

- Within 4-10mi of each other in densely populated areas

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12
Q

Common properties of Distribution Substations?

A
  • They have transformers that would change Subtransmission Voltages to Distribution Voltages
  • Typical station might have two Subtransmission lines supplying the power and 10 Distribution circuits leaving the station to supply power to customers in the area
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13
Q

Substation Functions

A
  • Voltage Change
  • Point of interconnection for lines of different ownership
  • Power flowing in and out of the substation measured
  • Lines coming in and out the station connected and disconnected for routine work or abnormal conditions
  • Equipment inside the station connected and disconnected for routine work or abnormal conditions
  • Lightning surges and switching surges removed for line and equipment
  • Voltage and Current on lines controlled
  • Communication circuits connected to lines and equipment
  • AC-DC-AC
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14
Q

What are some of the major pieces of equipment easily identified?

A
  • Power Transformers
  • Circuit Breakers
  • Disconnect Switches
  • Current and Potential Transformers
  • Capacitors and Reactors
  • Voltage Regulators
  • Steel Structures
  • Control House
  • Ground Grid
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15
Q

What are Power Transformers used for?

A

To change voltage level from one to another

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16
Q

Common properties of Power Transformers

A
  • Large
  • Heavy
  • Contain mineral oil
  • Require special transportation
  • Older stations have 3-Single Phase units
  • Newer stations have 1-3 Phase unit
  • May or may not have a Load Tap Changer (LTC)
17
Q

What is LTC used for?

A

To cut in or out a portion of the transformer winding which adjusts the voltage to the conditions.

18
Q

Common properties of Circuit Breakers?

A
  • Connect and disconnect lines and equipment

- Large in size but not as heavy as transformers

19
Q

What are Circuit Breakers designed to do?

A

Interrupt large amounts of current, and typically use oil, air, vacuum, or Sulfur-Hexafluoride Gas

20
Q

Whats the purpose of installing Disconnect Switches?

A
  • Isolate lines and equipment
  • Provide a means to connect or disconnect parts of the station to reroute flow of power
  • Normally operated by Switchman
21
Q

How do Current and Potential Transformers work?

A
  • Provide a reduction in the voltage and current so the power flow can be measured
  • Sense abnormal levels of voltage and current which is used to disconnect lines and equipment during trouble conditions
22
Q

How do Capacitors and Reactors work?

A
  • Assist in controlling the flow of power on the system

- Connected and disconnected from the system based upon the dynamics of the flow of power

23
Q

What do Voltage Regulators do?

A

-Automatically adjust the voltage as required
-If the station transformer does not have a LTC a separate regulator may be used
The Regulator may be 3-Single Phase or 1-3 Phase unit

24
Q

What do Steel Structures in Substations provide?

A
  • Means to terminate lines entering and leaving the station

- Mount switches, disconnects, bus conductors, and other equipment

25
Q

What is a Control House?

A
  • Houses key control equipment such as relays, meters, and computers
  • Contains DC batteries that are used to control key equipment if power to the station is lost
26
Q

How does the Ground Grid work?

A
  • Provide a path to earth for lightning surges
  • Provide a ground reference source for transformers and associated system neutral conductors
  • Provide a ground source for other station equipment
  • Ensures safety to the workers in the station by limiting ground potential differences
  • Ensure the safety of the public who may be near the station fence during a fault condition
  • Limit the influence of faults to communications facilities entering the station
27
Q

What makes up the Ground Grid?

A
  • Large stranded copper wire buried 12-18 inches below the grade and spaced in a grid pattern of 8-20 foot squares
  • Supplemented by ground rods as necessary to to further reduce the overall resistance
  • Covers the entire footprint and slightly outside the perimeter fence
  • The fence is connected to the grid at several locations`
28
Q

Basic Substation design?

A
  • Enough room for expansion in case more capacity for power delivery is needed
  • So equipment can be safely maintained and operated with room for bringing in a mobile substation in case a transformer needs to be taken out of service
29
Q

What are the Key Elements when talking about Environmental Considerations?

A
  • Appearance of the Station - Attractive Landscaping, Low Structure Profile and Decorative Fencing
  • Electromagnetic Fields - Minimize EMF
  • Sound - Sound Barriers or Special Design Consideratio
  • Oil Spill Containment - Contain released liquid in case of catastrophic failure & have immediate Cleanup Crew
  • Fencing - Installed for both human and wildlife safety and Substation equipment security. Must be surrounded by a high fence

Electrical Grid 1 (10 decks)

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