POWER FLOW IN H.T. CABLE

hallo dhayanandhan,

would you please to describe about your "proper CIRCUIT INTERLOCKING system" ?? (single line diagram will be best) …is that correct you say it happened after 9 years without problem??

Since the Turbo alternator supply to 3 transformer's CBs (A,B,C transformer) …have you double checked that the Interlock CBs are correct??

Based on your description I would suggest that you must localize your problem first by trying to do this step by step :

1. - shut down the EB before change it to the Alternator supply
2. - disconnect the transformer before do the change over
3. - observe about what causes the CB trip, whether power reverse, over voltage, earth fault etc so that you can determine the fault.

thank you & cheers,

Dear Mr. Tootie,

Thank you for your immediate response and I will furnish the details such as single line diagram etc. shortly.

Thank you once again.

DHAYANANDHAN,

CR4 MEMBER, INDIA

And also check the type of load for the three transformers?

May be under some capacitive condition, this problem is happening. (the difference is between the infinite grid - EB vs finite power supply- alternator)

Dear Guest,

Thank you or your response and advise. I will check up in the manner you have suggested and give you the feed back, so that it will be useful for CR4 MEMBERS.

DHAYANANDHAN.S, CR4 MEMBER,

INDIA.

Hi dhayanandhan,

Is the breaker trips on overcurrent or earth fault? Since the Panel is functional through the breaker from EB the rest of the HT panel and down stream distribution appears to be normal. You state that the breaker is also functioning normal.The points to be clarified are(i) when the changeover is being done supply from EB is available or not. (ii) Is the interlocking still functional.(iii) Is the breaker has draw out earthing system for safety if so weather it is functional? (iv) Did you carry out megger test of the breaker terminal point (v) CT & PT of the panel is checked for normal functioning and insulation? Did any Phase sequence done on cable either at EB side or Local Generator side. Please check and see weather you can locate the fault.

Thank you Mr. Abraham, for your response and advise. I will check up in the manner you have suggested and give you the feed back, so that you will know what could be the error, and it will also be useful for CR4 MEMBERS.

DHAYANANDHAN.S, CR4 MEMBER,

INDIA.

When change over is opted for this trfr while other two trfrs are in cut off state -

response could be clueful .

Thank you Mr. Sivaa, for your response. It is not possible to isolate the other 2 transformers. What is possible is while changing over to the Turbo-set Power it is possible to charge this transformer first and observe, then charge the other 2 transformers.

By trying this method there is a possible problem that the feed water pums starting cannot be delayed beyond a particular duration which will be in 40 to 50 seconds and by this time the boiler pressure will come down.

DHAYANANDHAN.S,

CR4 MEMBER,

INDIA.

For this trfr ; O/P current rating when compared with second trfr ; with E.B. Supply - is it more ?

Connected load can be partially switched off { !! } for this trfr , while changing over - for observations , please .

As Interlock mechanism is considered for satisfactory performance , such parameters are to be considered . Else , we need to refer that .

Dear Mr.Sivaa,

The current rating is similar. The transformer has load of 5 to 6 % of full load.

Still the problem evades and mystery.

DHAYANANDHAN.S,

CR4 MEMBER,

INDIA.

Hello Mr Dayanandhan,

base on your description about your power system your are not synchornousing EB grid

with your TG supply. It seems the problem may be with the Ht cable connecting

between TG HT breaker panel to Transformer breaker panel or faulty relay or relay

setting.please check & confirm.

Dear Mr. Kamalakar,

the relays are O.K. We are not synchronising with Grid. It is only cutting the grid and switch over to Turbo-alternatr supply. What could be the problem is still evading, and remains mystery. When it is O.K with grid supply it should be O.K for any supply.

DHAYANANDHAN.S,CR4 MEMBER.

It must be the inrush current that is handled by the generator AVR and making the breaker to trip, the grid impedance whereas will cause the voltage to drop, making current go down and saving the trip.

Did you try to cut off some loads on the transformer while change over and see?