Online UPS, it is getting power AC is converting to DC, then
the DC source stored to Battery at power supply on mode when
power fail, the DC sorce is changed to AC by inverter so
output power is having without noise.
OFFline UPS is having automatic voltage regulator, it
getting power from supply, it is regulated by AVR, then
power stored to battery so the change over time approx 2ms
to 5ms so change over noise comes.
Online UPS is unterrupted power suppy to the load,
Offline UPS can't ensure uninterrupted power supply, it
depends on the tolerance of the load. For any sophisticated
equipment (medical equipment), Online UPS is recommended.
A standby UPS or "offline UPS" draws current from the AC
outlet and switches to battery within a few milliseconds
after detecting a power failure.
The line interactive UPS "interacts" with the AC power line
to smooth out the waveforms and correct the rise and fall of
The "Online UPS" is the most advanced and most costly UPS.
The inverter is continuously providing clean power from the
battery, and the computer equipment is never receiving power
directly from the AC outlet. However, online units contain
cooling fans, which do make noise and may require some
location planning for the home user or small office.
On load tap changer (OLTC) explode?
Vector group: Ynd11
Rated Power: 353MVA
Rated Current: 693A
Type: T III Y1000 110/c 12193w
Max Operation Current: 295A
Step Voltage: 550V
Arrangement in Tx windings: Y Connection
Problem: Damage of Unit 1 Generator Transformer On Load Tap
Description of Incident:
9.00 a.m. :- Generator No Load test on excitation system
10.30 a.m :- Carried out AVR change over
11.30 a.m :- Preparation for Generator Manual Synchronizing
12.00 a.m :- Manual Synshronizing test started.
Observed incoming generator voltage higher than running voltage.
CECR operator operated Generator Transformer OLTC to bring down
the incoming generator voltage
12.03 a.m :-Generator Transformer abnormal alarm operated at
Gen.Control Desk (CECR)
CECR operater at Generator transformer bay informed that the
oil splashed out from OLTC.
CECR operater informed that he heard explosion inside OLTC.
Observed Oil level & Oil Flow alaram operated at Tranformer
12.05 am :- CECR operator 'Open Gen Field Breaker”
12.10 a.m. :- Elec1 team inspected the OLTC and found the
OLTC rupture disk was broken
and oil spilled at OLTC area.
- Elec1 found the OLTC top cover bulging.
Do anyone know why and possibility cause happen in this OLTC.