Circuit Breaker Troubleshooting
How long should you apply HV across the terminals of the interrupter be when testing vacuum loss?
What is one minute.
At what amps are disconnect switch whips designed to interrupt
What is less than 12 amps.
The network protector has an operating handle with these three operating positions:
What are automatic, open, and close.
If possible, how often should infrared analysis be conducted on equipment that is energized under full load.
What is annually.
Name 3 functions that oil performs in a transformer.
What are:
Provides excellent insulation
Provides cooling
High dielectric strength (the breakdown voltage)
High flashpoint and very stable at high temperatures
Oil also acts a barrier between atmospheric oxygen and the cellulose
72% of major circuit breaker failures are directly related to these two failures.
What are drive mechanism and electrical control and auxiliary circuits.
switches will have adequate contact pressure if the blade has rotated to within _____________ of perpendicular in the contact.
What is plus or minus 5 degrees.
The network protector is designed to protect the system from:
What are primary feeder faults and internal transformer faults..
90% of bushing failures are attributed to this.
What is water entrance through the top seal.
What gas is an indicator of arcing/sparking and severe overheating.
What is acetylene.
This performs three functions: charge the closing spring, release the open spring, and release the closing spring on command.
What is the control scheme.
A group of vertically mounted disconnect switches are considered properly open at.
What is 90 degrees + to be used as a held point of clearance for workers.
The most important elements of an A/C network power system are the:
What are networks transformers and network protectors.
The temperature of a normal LTC should be __________ than the main transformer?
What is cooler.
What gas suggest ingress of outside air into the transformer tank.
What is oxygen.
If the electrical control scheme is proven operational, the next step is to troubleshoot the?
What is the mechanical portion of the mechanism.
The operating mechanism is intended to fully open and fully close the disconnect switch by rotating the vertical operating pipe
What is180 degrees (plus or minus)
Low current arcing faults on ___________________ can sustain themselves for extended periods of time and cause extensive damage, more so than at 208Y/120-volts.
What are 480/277-volt spot network secondaries.
If after checking the transformer oil pumps for vibration and the bearings are suspect, what should be done?
What is have the DGA lab check for dissolved metals in the oil.
On newly energized transformers, oil samples (DGA) are taken at what intervals.
What is 1hr, 24hr, 48hr, 72hr, 1 week, 1 month, then once annually.
Circuit breakers are designed to satisfy predetermined breaking conditions and have electrical properties that can be resumed by the following:
What are:
Current carrying property
Insulating property
Current breaking property
Name the three standard types of group operated disconnect switch operating mechanisms.
What are the swing handle, hand crank, and the motor operated device (MOD)
Radial, loop, and network are three basic types of this.
What are distribution system designs.
A cool transformer radiator or segment indicates what?
What is a valve is closed or the radiator or segment is plugged.
What five forms can water exist in a transformer.
1. Free water, at the bottom of the tank.
2. Ice at the tank bottom.
3. Water can be in the form of a water/oil emulsion.
4. Water can be dissolved in the oil and is given in ppm in the DGA.
5. Water can be in the form of humidity.