What is the purpose of Fyrite tester?
To determine oxygen content in the gas space of a transformer.
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.
Explain the purpose of the airflow tester.
Tests high side fuses for proper operation.
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.
What is the common name of these transformers?
Dual voltage transformers.
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.
Why is the "equalize" setting used?
- To burn off sulfation.
- Reduces variations in cell voltage readings.
What happens if the bank is left on equalize for to long?
- Excessive gassing reduces electrolyte levels.
- Battery damage can occur.
What are the 4 main STAGES of transformer processing and the purpose of each?
- HEATING THE OIL.
- REMOVING THE OIL.
- TRANSFORMER DRYOUT.
- VACUUM FILLING.
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.
What is the purpose of processing oil?
- To clean the oil.
- Remove moisture.
- Reduce acids, (if necessary).
What is the purpose of a vacuum during processing oil?
To assist in de gasing and removal of moisture from the oil.
What is the purpose of a vacuum during transformer dryout?
To assist in removal of moisture from transformer insulation.
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.
What is the purpose of the cold trap?
- Collects moisture when air passes through it.
- To indicate the dryness of the transformer.
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.
How much acetone is initially placed in the cold trap?
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.
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.
Why is it necessary to have a oil sight gauge during processing?
To monitor oil levels while draining and filling transformer.
Where is the sight gage connected when processing?
Transformer drain valve and opening at top of transformer.
What stages are the sight gage monitored?
Draining and filling transformer.
At what viscosity should the vacuum pump oil be changed?
70% of new oil.
What type of counting mechanisms are used in sectionalizers?
What is the most common type of sectionalizer used at T P U?
G N 3 E
Can this type of sectionalizer be used to pickup load?
Can this type of sectionalizer be used to interrupt load? How many amps?
Can this type of sectionalizer be used to interrupt fault current?
Explain wetting Voltage:
Voltage available at relay & status point contacts.
Where would you find wetting Voltage in a substation?
SCADA & some control and relay systems.
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.
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.
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.
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.