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What is the purpose of Fyrite tester?
To determine oxygen content in the gas space of a transformer.
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Explain purpose of gas bottles in the T C G tester.
- Zero grade nitrogen. Test calibration
- 1 % Methane. Test calibration
- Instrament Air. Test calibration and operation.
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Explain the purpose of the airflow tester.
Tests high side fuses for proper operation.
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Explain why some transformers have 7,200 or 2,400 volt rating.
Voltage can be set at either 12.5 K V or 4 K V systems.
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What is the common name of these transformers?
Dual voltage transformers.
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What tests are performed on batteries and at what intervals?
- Monthly. High and low cell voltage checks, overall voltage, and charging current.
- Quarterly. Voltage check of every cell, overall voltage, and charging current.
- Annually. E Bite, Impedance test of each cell.
- 3 to 5 years. Capacity test.
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Why is the "equalize" setting used?
- To burn off sulfation.
- Reduces variations in cell voltage readings.
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What happens if the bank is left on equalize for to long?
- Excessive gassing reduces electrolyte levels.
- Battery damage can occur.
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What are the 4 main STAGES of transformer processing and the purpose of each?
- HEATING THE OIL.
- REMOVING THE OIL.
- TRANSFORMER DRYOUT.
- VACUUM FILLING.
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What are the 4 main stages of transformer processing and the PURPOSE of each?
- Processing oil and heating the core temperature of the transformer.
- Storing the oil before appling vacuum to the tank.
- Removes moisture from the transformer using heat and vacuum.
- To prevent air bubbles in the transformer core when refilling with oil.
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What is the purpose of processing oil?
- To clean the oil.
- Remove moisture.
- Reduce acids, (if necessary).
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What is the purpose of a vacuum during processing oil?
To assist in de gasing and removal of moisture from the oil.
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What is the purpose of a vacuum during transformer dryout?
To assist in removal of moisture from transformer insulation.
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What is the purpose of the dry air from the dry air machine during processing?
- Helps prevent moisture from entering the transformer during oil circulation and removal.
- Used to break vacuum after filling.
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What is the purpose of the cold trap?
- Collects moisture when air passes through it.
- To indicate the dryness of the transformer.
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What piece of equipment is located in the processing trailer must be running before dry ice is added to the cold trap and why?
- Vacuum booster pump.
- Violent eruptions can occur.
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How much acetone is initially placed in the cold trap?
5 Gallons.
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What considerations must be given when arranging oil hoses for processing?
- Oil should flow:
- In and out of the transformer.
- In and out of the storage tanks.
- Circulate through the hoses.
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What processor valves should be opened before any oil circulation begins and why?
- To and from storage valves.
- The oil will have a path to circulate if the inlet and outlet valves are closed.
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Why is it necessary to have a oil sight gauge during processing?
To monitor oil levels while draining and filling transformer.
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Where is the sight gage connected when processing?
Transformer drain valve and opening at top of transformer.
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What stages are the sight gage monitored?
Draining and filling transformer.
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At what viscosity should the vacuum pump oil be changed?
70% of new oil.
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What type of counting mechanisms are used in sectionalizers?
- Spring.
- Hydraulic.
- Electronic.
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What is the most common type of sectionalizer used at T P U?
G N 3 E
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Can this type of sectionalizer be used to pickup load?
Yes.
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Can this type of sectionalizer be used to interrupt load? How many amps?
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Can this type of sectionalizer be used to interrupt fault current?
No.
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Explain wetting Voltage:
Voltage available at relay & status point contacts.
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Where would you find wetting Voltage in a substation?
SCADA & some control and relay systems.
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State at least 3 safety precautions to be observed when using a megger.
- De energize, isolate, and discharge circuit before connecting Megger.
- Do not touch leads when testing.
- Discharge equipment after testing and before handling leads or equipment.
- Only use Meggers for high resistance measurements.
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Describe the typical sequence of events that cause a power circuit breaker to close.
- Closing coil operates.
- Stored energy is released to linkage and operating rod.
- Operating rod moves contacts to the closed position and charges opening spring.
- Holding latch maintains contacts in closed position until released.
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Describe the typical sequence of events that enable a power circuit breaker to trip and open.
- Trip coil or manual trip operates and releases trip latch.
- Opening spring releases stored energy through linkage and operating rod separating the contacts.
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When a job briefing is conducted, what are the minimum areas that need to be covered?
- Hazards associated with the job.
- Work procedures involved.
- Special precautions.
- Energy source controls.
- PPE Requirements.
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