RF3:- Approximate Calculations of O/C E/F Settings for Two Transformers Operating In Parallel

     In the following figure let HV Bus voltage is ??kV  and LV Bus voltage is ??kV.
     T/F-1 having capacity ?? MVA  while T/F-2 having capacity ?? MVA 
     T/F-1 HV CTR is ??/1 Amp  and its LV CTR is ??/1 Amp.
     while T/F-2 HV CTR is ??/1 Amp  and its LV CTR is ??/1 Amp.
     T/F-1 reactance is ?? %  and T/F-2 reactance is ?? %.

     What shall be the PSM and TMS setting for O/C and E/F relays for T/F HV side and LV side.


(NOTE: Use approximate calculations neglecting source impedance and calculating TMS at 70% of LV Bus fault. Roundup % reactance to nearest integer. As we are neglecting source impedance, T/F short circuit current for LV bus fault can be calculated considering as if they are woring separately

Section-A: Calculations for Full Load Current and Short Circuit MVA.

1) T/F-1 LV Side Full Load Current =    Amp

2) T/F-2 LV Side Full Load Current =    Amp

3) T/F-1 HV Side Full Load Current =    Amp

4) T/F-2 HV Side Full Load Current =    Amp

5) T/F-1 Short Circuit MVA for LV Bus Fault =    MVA.

6) T/F-2 Short Circuit MVA for LV Bus Fault =    MVA.

Section-B: Calculations for LV Non-Dir., LV Forward and HV PSM.

7a) T/F-1 LV Non-Directional Relay O/C PSM =    %

7b) T/F-2 LV Non-Directional Relay O/C PSM =    %

8) T/F-1 LV Non-Directional E/F PSM =   30%    20%    15%

9) T/F-2 LV Non-Directional E/F PSM =   30%    20%    15%

10a) T/F-1 HV O/C PSM =    %

10b) T/F-2 HV O/C PSM =    %

11) T/F-1 HV E/F PSM =   30%    20%    15%

12) T/F-2 HV E/F PSM =   30%    20%    15%

13a) T/F-1 LV Forward O/C PSM =    %

13b) T/F-2 LV Forward O/C PSM =    %

14) T/F-1 LV Forward E/F PSM =   30%    20%    15%

15) T/F-2 LV Forward E/F PSM =   30%    20%    15%

Section-C: Calculations for LV Non-Dir., LV Forward and HV TMS.

16a) T/F-1 LV Short Circuit Current =    Amp

16b) T/F-2 LV Short Circuit Current =    Amp

17a) T/F-1 HV Short Circuit Current =    Amp

17b) T/F-2 HV Short Circuit Current =    Amp

18a) T/F-1 LV Relay Current at 70% of Bus Fault Level =    Amp

18b) T/F-1 LV Relay Current at 70% of Bus Fault Level =    Amp

19a) T/F-1 LV Non-Directional O/C TMS =    

19b) T/F-2 LV Non-Directional O/C TMS =  

20a) T/F-1 LV Non-Directional E/F TMS =    

20b) T/F-2 LV Non-Directional E/F TMS =  

21a) T/F-1 HV Relay Current at 70% of LV Bus Fault Level =    Amp

21b) T/F-1 HV Relay Current at 70% of LV Bus Fault Level =    Amp

22a) T/F-1 HV O/C TMS =    

22b) T/F-2 HV O/C TMS =  

23a) T/F-1 HV E/F TMS =    

23b) T/F-2 HV E/F TMS =  

24) T/F-1 Forward O/C TMS =    .

25) T/F-2 Forward O/C TMS =    .

26) T/F-1 Forward E/F TMS =    .

27) T/F-2 Forward E/F TMS =    .

Topic SETOCTF Ex-3 Your score is:

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