RF1: Transformer O/C E/F Settings Basic Knowledge.

Q1.) Setting methodology for T/F HV side O/C E/F relay is -

Depends upon voltage level

Depends upon T/F operational mode

Same irrespective of T/F operational mode

None from this

Q2.) For transformer; setting of Overcurrent PSM shall be very precise -

A) For fully loaded transformers

B) For T/f having load trimming

C) For every transformer

D) For option A or B

Q3.) TMS for HV side overcurrent relay shall be such that HV side relay operational time would be 500 ms for relay current corresponding to -

70% of LV side bus fault

LV side bus fault

TF HV Terminal Fault

None of this

Q4.) Time discrimination between HV and LV side overcurrent relay at the fault level lower than considered for TMS calculations will be -

Less

More

Depends on Source Impedance

Depends on T/F Reactance

Q5.) For T/F LV Side Non-Directional relay TMS shall be calculated considering relay current corresponding to -

A) 70% of LV Bus fault

B) LV Bus fault

C) 70% of LV Bus fault with correct use of HS

D) A or B as per use of HS

Q6.) For transformer operating in parallel; most prefered protection scheme for LV side is -

Use of only directional relay

Dual directional relay

Use of Non-directional relay

Combination of directional and non-directional elements

Q7.) Whether it is possible to operate transformer in paralle if only Non-Directional relays are available to its LV side-

YES

NO

As a compromise for rear faults

As a compromise

Q8.) For T/F LV Side Forward-Directional element considering relay current corresponding to T/F LV LA fault we need to calculate -

E/F PSM

O/C and E/F TMS

E/F HS

O/C and E/F HS

Q9.) Approximate relay setting calculations may be risky decision in case of -

A) Remote Sub-stations

B) Sub-stations close to major grid source

C) Equally in both case A or B

Always

Q10.) For T/F HV O/C E/F relay HS shall corresponding to relay current for -

T/F HV terminal fault

70% of T/F HV terminal fault

T/F LV Bus Fault

70% of T/F LV Bus Fault

Topic SETOCTF Ex-1 Your score is:

000

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ABD AMT NSK PUN NGP KRD VSH

ABD1 ABD2 JALN PRBN NND1 NND2 LTR1 LTR2 BEED PRLI EKTN GRWL WALJ TPTN KMBH