Questions and Answers
What percentage of PSO distribution lines are below grade within the city limits?
Where are most of the below-grade PSO distribution lines located?
What is the maximum voltage that PSO distribution lines can carry?
Which materials are used for PSO distribution wires?
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What is the purpose of the coating on PSO distribution wires?
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What is the maximum voltage that transmission lines can carry in Tulsa?
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How many insulators do transmission lines in Tulsa usually have at a minimum?
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Where are transmission lines generally supported?
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What happens to the voltage at substations in Tulsa?
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What is a notable characteristic of substations?
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What is the primary function of transformers?
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Which type of transformer is often located in vaults?
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What is a significant hazard for responders when dealing with vaults?
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What is TFD personnel's protocol when dealing with fires in underground vaults?
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Apart from aerial, what other types of transformers are mentioned?
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What is the final part of the electrical distribution system?
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What type of wiring is most commonly used for service wires entering a residential structure?
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What occurs when current runs to ground at the point of contact of a downed, energized wire?
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What is 'step potential'?
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What should responders do if they find themselves experiencing step potential?
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Study Notes
Tulsa's Electrical System
- Transmission lines carry electricity up to 345,000 volts and are supported by towers or poles.
- These lines typically take electricity from generation sites to substations, and can be found within the city limits.
- Transmission lines can be identified by the number of insulators, typically at least six.
Substations
- Substations are fenced-in areas where the voltage is reduced and sent into the distribution part of the system.
Distribution Lines
- Within the city limits, PSO has approximately 35% of their distribution lines below grade, mainly in new residential neighborhoods and apartment complexes.
- Distribution lines carry up to 34,500 volts, are copper, aluminum, or aluminum-coated steel wires, and can be single strand or stranded.
- Wires are often coated with a material that protects against wear, chaffing, and corrosion, but is not insulation.
Transformers
- Transformers can be aerial, pad-mounted, or sub-surface, and are designed to reduce voltage to a more usable level for customers.
- Sub-surface transformers are often located in vaults, which are confined spaces that present significant hazards to responders.
- TFD personnel will not enter or attempt to fight fires in underground vaults without PSO on scene.
Service Connections
- The final part of the distribution system is the service connection, which delivers power to the customer through wires entering the structure through the weatherhead or a conduit.
- The most common service wires entering a residential structure are triplex wiring, including two wires carrying 120 volts each, and one neutral.
Electrical Hazards
- When a downed, energized wire is in contact with the earth, there is current running to ground at the point of contact, creating a gradient, or decreasing current, that spreads out concentrically.
- This energized field can extend for several feet from the point of contact, creating the possibility of step potential.
Step Potential
- Step potential occurs when responders create a circuit with their feet as they walk near a downed wire, creating a path or circuit that can cause current or shock.
- Tingling sensations in the lower extremities have been reported at lower voltages, and death or serious injury can result at higher voltages.
- To avoid step potential, responders should bring both feet together and hop away from the downed wire location.
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Description
This quiz covers electrical system response for the Tulsa Fire Department, specifically transmission lines and substations. Learn about electrical systems and emergency response strategies.
