BUS BAR CALCULATION

END USER = SVC A/C DGNP

CONSULTANT = NIL

SHOP ORDER NO = 7306026405

PROPOSED RATED BUS BAR CURRENT =

Ir (A) 1250

FAULT LEVEL

If (KA) 26.3

DURATION (SEC) 3

BUS BAR

W (mm) 60

T (mm) 16

R (RUN/PH) 1

BUS BAR RE-RATING TO BE DONE

AT AN AMBIENT TEMP OF =

50 DEG C

TEMP RISE CONSIDERED

WHILE RE-RATING =

55 DEG C

A. STEADY STATE THERMAL CURRENT CARRYING CAPACITY AT 40DEG C AMBIENT & 50DEG C TEMP RISE:

CURRENT CARRYING CAPACITY FOR SINGLE 60 X 16

CU BUS BAR = 1460 (REFER www.cda.org.uk)

MULT. FACTOR FOR 1 RUNS/PH= 1 (REFER www.cda.org.uk)

TOTAL CURRENT CARRYING CAPACITY / PH=

1460 X 1 = 1460

CROSS SECTION OF SINGLE BUS BAR CHAMBER IN HWX PANEL =

532 X 492 = 261744

TOTAL CU CROSS SECTION IN BUS BAR CHAMBER (INCLUDING ALL 3 PHASES)=

3 X W X T X R

= 3 X 60 X 16 X 1

= 2880

AREVA T D INDIA LIMITED

BUS BAR CALCULATION

TOTAL CU CROSS SECTION / BUS BAR CHAMBER AREA= 2880 / 261744

= 1.100311755 %

IF THIS RATIO IS LESS THAN 5%, DERATING FACTOR= 0.85

SO, ACTUAL CURRENT RATING / PH=

0.85 X 1460 = 1241 Amp

B. RE-RATING FOR DIFFERENT AMBIENT & TEMP. RISE:

RE-RATING TO BE DONE FOR:

AMBIENT TEMP= t2 = 50 DEG C

TEMP RISE= Φ2 = 55 DEG C

THEREFORE,

WORKING TEMP= T2 = 105 DEG C

SAY, REVISED BUS BAR CURRENT RATING (TO BE CALCULATED)= I2

FROM SECTION-A WE KNOW:

t1 = 40

Φ1 = 50

T1 = 90

I1 = 1241

NOW, WORKING FORMULA FOR CALCULATING THE REVISED BUS BAR CURRENT RATING :

I1 / I2 = (Φ1 / ΦΦ1 / ΦΦ1 / ΦΦ1 / Φ2)^0.61 X ((1+ρρρρ(T2-20) / (1+ρρρρ(T1-20))^0.5 (REFER www.cda.org.uk)

WHERE, ρ = TEMP. CO-EFFICIENT OF RESISTANCE FOR CU AT 20 DEG C = 0.00393

THEREFORE, REVISED BUS BAR CURRENT = I2 = 1285.90057 Amp

AREVA T D INDIA LIMITED