Core Topics 2013 Flashcards
The inducing of an EMF in a coil or conductor by magnetic flux lines generated in another coil or conductor is called
Mutual Induction
The construction of a basic transformer consists of the following components:
- Primary winding
- Secondary winding (s)
- Magnetic circuit
- Enclosure
The _______ winding is the winding where energy is applied. It may be either the high voltage or low voltage winding. Usually the _______ from the core in power transformers.
Primary
Furthest
The mathematical expression for the transformer voltage turns ratio is:
Ep/Es = Np/Ns
or
Ep Ns = Es Np
The _________ is the ratio between the currents in the primary and secondary of a transformer and is in __________ proportion to the turns-ratio
current ratio
inverse
__________ are the most common type used in the transfer of electrical power.
Iron core transformers
The cores of iron core transformers are designed to:
- Minimize flux leakage.
- Accommodate various winding configurations.
- Accommodate specific size requirements
In an __________ the windings are wound around an insulation or non-magnetic form.
air-core transformer
__________ consist of a single winding serving as both the primary and secondary.
Autotransformers
__________ can be designed with multiple taps or slider to provide a wide range of input and output voltages
Adjustable transformers
__________ maintain a constant output voltage with varying input voltage.
Regulating transformers
In a __________ connected transformer winding, one end of each of the leads is connected together. The three remaining leads are connected to the load or power source.
Wye
In the __________ connection, the windings are connected in series to form a closed loop
Delta
What were the two Root Causes leading to multiple failures associated with the Main Bank Transformer.
RC1 – Inappropriate material performance of the silicon polymer insulation prevented proper control of environmental contamination
RC2 – Engineers did not adhere to sound engineering principals by not using applicable codes and standards in the design of the CCVT.
EXPLAIN the function of the Capacitive Coupled Voltage Transformers (CCVTs).
The Capacitive Coupled Voltage Transformers (CCVTs) are necessary in high voltage transmission and distribution systems for relaying and metering.
The two methods by which the IDD system will use to identify a problem bushing and abnormality are:
- Measured capacitance of one phase is greater than the other phases by observing an increase in leakage current
- Power factor indicates a phase angle different from 120
The IDD ALERTS! associated with abnormalities within the IDD itself are:
- Maintenance Mode – IDD records data, but does not analyze the data
- Unable to obtain information – Information processing not functioning properly
- Unable to obtain recording – Hardware issue between IDD and Bushing CTs
The IDD ALERTS! associated with abnormal trends are
• Power Factor
o Slightly changed - Closely monitor
o Moderately changed - Investigate at earliest opportunity
o Severely changed - Investigate imediately
• Capacitance – Provides the same ALERTS! as Power Factor
Name three types of fittings used for Electrical Penetrations @ DCPP
- Swagelok Fittings (Most common)
- Hi-Seal
- Gyrolok
Name the three levels of FR clothing
Single-Layer Flame Resistant (SLFR): minimum rating of 8 cal/cm2.
Double-Layer Flame Resistant (DLFR): minimum rating of 15 cal/cm2
Suited: (15 cal/cm2 to 100 cal/cm2)
State the purpose of the brushless exciter
The Brushless Exciter is Designed to produce the generator field voltage and current required from no load to rated load. This provides rated output of the generator during normal and grid transient conditions
Name the 4 major components of the brushless exciter
- Permanent Magnet Generator (PMG)
• Provides a continuous source of AC power for excitation without the use of brushes or collector rings - AC Exciter Stator
• Provides a continuous magnetic field. - AC Exciter Rotor
• Induces an AC voltage in the three-phase exciter rotor windings. - Rectifier/Fuse Wheel.
• Converts 300Hz, 3 phase AC from the AC exciter into DC for application to the generator field.
How does the permanent magnet generator produce electricity without the use of brushes or slip rings?
Magnets rotate around conducting wires, this rotation creates electricity
AC Exciter is composed of what two parts
a Stator and a Rotor
Name the components make up the Fuse Wheel (rotating rectifier)
Diodes (120)
Full-wave rectifier
Fuses
a localized dielectric breakdown of a small portion of electrical insulation. It can be initiated by voids cracks or inclusions within a solid dielectric.
Partial Discharge
PD generally occurs in systems operating at voltages of _______ or above
3000
