Operation; I Basic Transformer Theory - Westinghouse PS-1002 Instruction Book

24
) b) Check tap changer operating mechanism
(
to make sure that the tap changer is in the proper posi­
tion for the required voltage.
DO NOT OPERATE THE TAP CHANGER WHILE THE
TRANSFORMER IS ENERGIZE D FROM ANY SOURCE.
THE TAP CHANGER WILL FLASHOVER AND CAUSE
TRANSFORMER F AlLURE. THE TANK MAY RUP­
TURE AND CAUSE PERSONAL INJURY.
) c) Delta-Wye and Series X Multiple con­
(
nections are made using an internal terminal board or
a de-energized switch . Make the connection according
to the chart on the transformer nameplate. Terminal
board connections must be mechanically tight to pre­
vent overheating of the joint. Transformers are shipped
connected in the higher voltage connection unless re­
quested otherwise by the Purchaser.
DO NOT OPERATE THE DELTA-WYE AND/OR SE­
RIES M U LTIP L E SWITCH WHILE THE TRANS­
FORMER IS ENERGIZED. TO DO SO WILL CAUSE
DANGER TO LIFE AND DAMAGE TO PROPERTY.
) d) A secure, effective low resistance ground
(
is essential for protection. The transformer tank must
be grounded permanently by connecting a ground
cable per the National Electric Code to a ground pad
located at the bottom of the tank.
A POOR GROUND CONNECTION MAY RESULT IN
DANGER TO LIFE OR DAMAGE TO PROPERTY.
) e) Check all conde nser bushings to be sure
(
the power factor test terminal is grounded before the
transformer is energized.
THE POWER FACTOR TEST TERMINAL MUST BE
GROUNDED DURING NORMAL OPERATION. IF
THE POWER FACTOR TERMINAL IS LEFT UN­
GROUNDED, A HAZARDOUS VOLTAGE WILL BE
IMPRESSED ON THE POWER FACTOR TEST TER­
MINAL. THE TERMINAL MAY FLASHOVER. LIFE
COULD BE IN DANGER.
)
7.
(
Make a physical examination of control circuit wiring and
alarm devices. Look for cut or broken insulation, and
open connections.
8. )
(
Liquid level should be at the correct level according to
Section 5 .4 , Table 2.
)
9 . (
Refinish all paint scratches. See Section 8 .8
)
1 0.
(
Tighten all external bolts and hardware. Check handholes,
mechanical relief devices. etc.
)
1 1 .
(
All tools or other objects used in installation are ac­
counted for and have been removed from the trans­
former.
When the inspections and tests in paragraphs 6 .6 . 1
through 6.6. 1 1 are complete and any required repairs
have been made , the transformer may be energized.
7.

OPERATION

7 . 1 Basic Transformer Theory
The electrical power transformer is an energy conversion
device . It is used to convert electric energy from the high
voltage levels used to transmit power to the low voltage
levels where the energy is consumed.
A simple transformer consists of an iron core with two
separate windings that are wound around the core. Refer
to Figure 17. When voltage is connected to the turns of
the primary winding, voltage is induced in the secondary
winding by electromagnetic induction. VOLTAGE WILL
BE ON THE SECONDARY TERMINALS XI AND X2
ANYTIME VOLT AGE IS CONNECTED TO THE PRI­
MARY WINDING TERMINALS H l AND H2. When an
electrical load is connected to the secondary, current will
flow in the secondary winding. The magnetic flux in the
core and the current flowing in the windings generate
heat, which is an indication that some of the energy is
consumed in the voltage conversion. Typically, the en­
ergy lost as heat is less than 1 % of the total transformed.