Introduction to Substations

As the core heats the oil, the oil rises. The oil is then forced against the case of the transformer where it radiates heat into the atmosphere and cools. As it cools, the oil circulates down to the bottom of the core.

Electrical devices that monitor current flow within the substation for relaying and metering purposes

Electrical Devices used to create isolation points within a substation

Two winding transformers that step down high voltage to a low voltage that can be read by instruments for metering and relaying

Allows a circuit breaker to be removed from service for maintenance without disrupting power flow. The load is transferred to an adjacent circuit breaker by opening and closing a series of disconnects and energizing the transfer bus.

Located adjacent to the generating station and are designed to step the voltage up to transmission levels. Voltage change may be from 13.8 kV to 500kV

Provide voltage changes that remain at the transmission level. This voltage change may be from 500kV to 230kV

typically located near load centers. their main function is to change the voltage from a higher transmission voltage (ea 345kV) to a subtransmission voltage (ea 69kV). These subtransmission circuits the travel to the distribution substations.

usually located in the middle of the load centers and step voltage down from subtransmission levels to distribution levels (ea 138kV to 12kV)

-Changing the voltage of circuits from 1 level to another -Connecting or disconnecting lines or equipment from each other -Controlling the flow of power -Recording flow of power and related data

-Generation Substation -Transmission Substation -Subtransmission Substation -Distribution Substation

If one circuit fails or needs to be take out of service for maintenance, power is supplied to the station using the alternate circuit.

protects the transformer and distribution bus from fault conditions similar to a circuit breaker; however, typically not set to reclose, since most faults are permanent.

To ensure all ground connections are of the same potential

Key equipment such as relays, meters, and batteries. It may also contain communication hardware that allows some station equipment to be operated from a remote location

Before construction,maintenance, or operation is preformed

To allow the utility to confirm conditions of a station and record certain key data that indicates the operation of the system

-Protect electrical equipment and lines from abnormal conditions that occur -Isolate piece of equipment or line for maintenance

-Mechanical -Pneumatic and Mechanical -Hydraulic and Mechanical

-Single blade -Gang-Operated -Motor-Operated

The oil temperature, the sensoring point of the thermometer is physically located at the hottest spot usually at the center of secondary windings

Because the oil servers 2 purposes it insulates energized equipment and acts as a cooling agent. Impurities can drastically lower the dielectric strength of oil.

commonly used in power transformers as a blanket to help keep moisture from being absorbed by the oil. Space between the top of the oil level and the top of the power transformer case

the turns ratio is much greater than that of a regulator

Detect abnormal conditions on the power system and these initiate action to isolate or correct the conditions

-Programmable settings -Automatic self-check and diagnosis -Multiple relay functions such as over-current, over-voltage and under voltage -Telephone or radio interface, allowing remote programming and interrogation

Electromechanical relays have a target that drops (usually a red flag) to indicate that relay has operated.

-Not a type but a function, it opens up the power circuit breaker and operates under 2 conditions: Time over-current or Instantaneous over-current. -Time over-current tends to be a lower level of fault current; fault is somewhere down the line -Instantaneous over-current is a solid fault very high level and close to the source (usually in the 1st half of the circuit)

Batteries provide DC voltage used to operate power circuit breakers

•Three-Phase ammeter •VARS or wattmeter •Three overcurrent relays •Lockout relay