Answer / guest

isolation transformers are used mainly for safety.
in the mains supply one line will be earthed. So if we touch
the other line we will get electric shock(because the
circuit will be completed through the
phase->human->ground(on which we are standing)). in an
isolation transformer no end is earthed. so even if we touch
one line we wont get shock because the circuit is not
complete.(dont do it).
one end of the CRO input will be grounded. so when
ever we want to measure any parameter of the mains using cro
we use a isolation transformer

On load tap changer (OLTC) explode? Transformer Vector group: Ynd11 Rated Power: 353MVA Rated Current: 693A Voltage:294/20KV OLTC 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 Changer (OLTC) Description of Incident: 9.00 a.m. :- Generator No Load test on excitation system started 10.30 a.m :- Carried out AVR change over test 11.30 a.m :- Preparation for Generator Manual Synchronizing test 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 transformer oil splashed out from OLTC. CECR operater informed that he heard explosion inside OLTC. Observed Oil level & Oil Flow alaram operated at Tranformer local annunciator. 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.

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