Client:

AMPIN ENERGY TRANSITION

Project: DEVELOPMENT OF 40MW(AC)/60MWp SOLAR PV PLANT,

Owner:

M/S AMP ENERGY C&I THREE PVT LTD.

EPC Contractor:

RAYS POWER INFRA LTD

Document Title:

LT & HT Cable Sizing Calculation

Doc./Dwg. No.:

Rev No: 00
RPIPL-KBJ-AMP--EE-CAL-LT_CBL-001 &
RPIPL-KBJ-AMP--EE-CAL-HT_CBL-001

Stamp:

REVISION STATUS
Prepared Reviewed Approved
Rev No. Name Date Name Date
Name Date
Mech Elec Civil C&I
00 RG 11-01-24 AM NSG 11-01-24
 INVERTER TO TRANSFORMER LT CABLE
1.0 OBJECTIVE :
To size LT AC Cables, XLPE insulated, Armoured, Aluminium Between LV Side of inverter Transformer and Inverter.
2.0 REFERENCE:
Current Ratings, Derating Factors are taken from "KEI" Cable Catalogue for LT XLPE Insulated, Armoured, Aluminium, Power cables.
3 DESIGN CRITERIA:
3.1 The cross section shall fulfill the following criteria:
i) To be withstand in short circuit time fault current in the circuit for the duration of it's circuit interrupting device.
ii) To be able to carry full load current after considering appropriate derating factor for ambient temperature variation, method of laying.
4.0 DESIGN BASIS:
a) The maximum symmetrical fault level at 660V bus is as follows:
Max fault kA = 48.114 kA
b) Derating Factor for Continuous Current Rating:
For Current Carrying Capacity Derating Factor Due to Site condition is arrived at as follows
i) For variation In Ambient temperature for cables laid in air (Assumed 50°C) = 0.89 Ref. - IS 3961-7 (Table- 13)
ii) Group rating factor for two no. of circuits per ladder support at 70mm space
0.95
(Cables laid direct on support in Trefoil formation) Ref. - IS 3961-7 (Table- 34)
Net Derating Factor = 0.85
5.0 CALCULATION:
5.1) Minimum cross section of LV cable based on short Time current withstand capability
i) Duration of short circuit to be considered = 0.3 Sec. (Breaker Operating Time)
ii) Minimum cross section required for 33kV cable to withstand fault Current for 0.3
(I*√t)/k
Sec. =
Where k is the constant for AL XLPE Cable = 0.094
= 280.35 Sq.mm.
Therefor minimum cross section of the cable is selected as 1CX400Sq.mm XLPE(AL).
5.2) Selection of cable Based on Rated current carrying(continuously) capability:
LT Cable between LV Side of Transformer to Inverter
i) Capacity = 4400 kW
ii) Full Load Current = 3849.1147 A
iii) Current Carrying Capacity of 400 Sq.mm (AL.) cable in Air at 40° C= 593 A
iv) Derated current carrying capacity of 400 Sq.mm (Al) 501.3815 A
v) No. of runs required = 7.6770178 run
vi) Selected Cable size is = 12R, 1Cx400 Sq. mm (Al) XLPE/phase
Therefore cable size is selected as 12R, 1Cx400Sq.mm /phase (AL.) XLPE is adequate from continuous current carrying capability points of view.
 INVERTER TO TRANSFORMER LT CABLE
1.0 OBJECTIVE :
To size LT AC Cables, XLPE insulated, Armoured, Aluminium Between LV Side of inverter Transformer and Inverter.
2.0 REFERENCE:
Current Ratings, Derating Factors are taken from "KEI" Cable Catalogue for LT XLPE Insulated, Armoured, Aluminium, Power cables.
3 DESIGN CRITERIA:
3.1 The cross section shall fulfill the following criteria:
i) To be withstand in short circuit time fault current in the circuit for the duration of it's circuit interrupting device.
ii) To be able to carry full load current after considering appropriate derating factor for ambient temperature variation, method of laying.
4.0 DESIGN BASIS:
a) The maximum symmetrical fault level at 660V bus is as follows:
Max fault kA = 48.114 kA
b) Derating Factor for Continuous Current Rating:
For Current Carrying Capacity Derating Factor Due to Site condition is arrived at as follows
i) For variation In Ambient temperature for cables laid in air (Assumed 50°C) = 0.89 Ref. - IS 3961-7 (Table- 13)
ii) Group rating factor for two no. of circuits per ladder support at 70mm space
0.95
(Cables laid direct on support in Trefoil formation) Ref. - IS 3961-7 (Table- 34)
Net Derating Factor = 0.85
5.0 CALCULATION:
5.1) Minimum cross section of LV cable based on short Time current withstand capability
i) Duration of short circuit to be considered = 0.3 Sec. (Breaker Operating Time)
ii) Minimum cross section required for 33kV cable to withstand fault Current for 0.3
(I*√t)/k
Sec. =
Where k is the constant for AL XLPE Cable = 0.094
= 280.35 Sq.mm.
Therefor minimum cross section of the cable is selected as 1CX400Sq.mm XLPE(AL).
5.2) Selection of cable Based on Rated current carrying(continuously) capability:
LT Cable between LV Side of Transformer to Inverter
i) Capacity = 3300 kW
ii) Full Load Current = 2886.836 A
iii) Current Carrying Capacity of 400 Sq.mm (AL.) cable in Air at 40° C= 593 A
iv) Derated current carrying capacity of 400 Sq.mm (Al) 501.3815 A
v) No. of runs required = 5.7577634 run
vi) Selected Cable size is = 9R, 1Cx400 Sq. mm (Al) XLPE/phase
Therefore cable size is selected as 9R, 1Cx400Sq.mm /phase (AL.) XLPE is adequate from continuous current carrying capability points of view.
 TRANSFORMER TO ICOG TO HT PANEL HT CABLE
1.0 OBJECTIVE
To size 19/33kV, XLPE Insulated, Armoured, HT cable for outgoing feeder
2.0 REFERENCES
Current ratings, derating factors are taken from "KEI" Cable Catalogue for 33kV XLPE insulated, armoured, Aluminium, Power
cables.
3 DESIGN CRITERIA:
3.1 The cross section shall fulfill the following criteria:
i) To be withstand in short circuit time fault current in the circuit for the duration of it's circuit interrupting device.
ii) To be able to carry full load current after considering appropriate derating factor for ambient temperature variation, method of
4.0 DESIGN BASIS
a) The maximum symmetrical fault level at 33 KV bus is as follows:
Max fault KA = 25 kA
b) Derating Factor for continuous current rating=
For current carrying capacity derating factor due to site condition is arrived at as follows
i) For variation in Ground temp. Ground ambient temp 35°C = 0.96 Ref. - IS 3961-7 (Table- 14)
ii) For depth of cable laying. Cable directly laid in ground (at 1.05 meter)= 1 Ref. - IS 3961-7 (Table- 16)
iii) Rating factor for variation in soil thermal resistivity at 1.138K.m/W= 1.08 Ref. - IS 3961-7 (Table- 24)
Derating factor for Multicore cables buried in ground with 200mm
iv) 0.68 Ref. - IS 3961-7 (Table- 28)
space (Maximum 5 Circuit in a Trench)=
Net derating Factor= 0.71
5.0 Minimum cross section of HT cable based on short Time current withstand capability
5.1) Minimum cross section of MV cable based on short Time current withstand capability
i) Duration of short circuit to be considered = 0.3 Sec. (Breaker Operating Time)
ii) Minimum cross section required for 33kV cable to withstand Fault
(I*√t)/k
Current for 0.3 Sec. =
Where k is the constant for AL XLPE Cable = 0.094
= 145.67 Sq.mm.
Therefor minimum cross section of the cable is selected as 3C X 185 Sq.mm XLPE(AL).
5.1 Selection of cable Based on Rated current carrying(continuously) capability:
8.8 MVA Transformer to Main Panel
i) Capacity = 8800 kVA
ii) Full load current = 154.0 A
iii) Current carrying capacity of 185 Sq.mm (AL.) cable in Ground at 30° C 270 A
iv) Derated current carrying capacity of 3CX185 Sq.mm (Al) 190.356 A
v) No. of runs required = 0.81 run
vi) Selected Cable size is = 1R, 3Cx185 Sq. mm (Al) XLPE
Therefore cable size is selected as 1R, 3Cx 185 Sq.mm (Al.) XLPE is adequate from continuous current carrying capability
 HT PANEL TO TRANSFORMER
1.0 OBJECTIVE
To size 19/33kV, XLPE Insulated, Armoured, HT cable for outgoing feeder
2.0 REFERENCES
Current ratings, derating factors are taken from "KEI" Cable Catalogue for 33kV XLPE insulated, armoured, Aluminium, Power
cables.
3 DESIGN CRITERIA:
3.1 The cross section shall fulfill the following criteria:
i) To be withstand in short circuit time fault current in the circuit for the duration of it's circuit interrupting device.
ii) To be able to carry full load current after considering appropriate derating factor for ambient temperature variation, method of
4.0 DESIGN BASIS
a) The maximum symmetrical fault level at 33 KV bus is as follows:
Max fault KA = 25 kA
b) Derating Factor for continuous current rating=
For current carrying capacity derating factor due to site condition is arrived at as follows
i) For variation in Ground temp. Ground ambient temp 35°C = 0.96 Ref. - IS 3961-7 (Table- 14)
ii) For depth of cable laying. Cable directly laid in ground (at 1.05 meter)= 1 Ref. - IS 3961-7 (Table- 16)
Grouping factor for two circuit of three single core cable in ground
iii) 0.83 Ref. - IS 3961-7 (Table- 26)
with 200mm space=
Net derating Factor= 0.80
5.0 Minimum cross section of DC cable based on short Time current withstand capability
5.1) Minimum cross section of MV cable based on short Time current withstand capability
i) Duration of short circuit to be considered = 0.3 Sec. (Breaker Operating Time)
ii) Minimum cross section required for 33kV cable to withstand Fault
(I*√t)/k
Current for 0.3 Sec. =
Where k is the constant for AL XLPE Cable = 0.094
= 145.67 Sq.mm.
Therefor minimum cross section of the cable is selected as 630 Sq.mm XLPE(AL).
5.1 Selection of cable Based on Rated current carrying(continuously) capability:
Case 1:HT panel to Power Transformer
i) Capacity = 41800 kVA
ii) Full load current = 731.3 A
iii) Current carrying capacity of 630 Sq.mm (AL.) cable in ground at 40° C 496 A
iv) Derated current carrying capacity of 630 Sq.mm (Al) = 395.213 A
v) No. of runs required = 1.85
vi) Selected Cable size is = 2R,1Cx630 Sq. mm (Al) XLPE
Therefore cable size is selected as 2R,1Cx630 Sq.mm (Al.) XLPE is adequate from continuous current carrying capability points of