CALCULATION NOTES

HV & MV CABLES
1. CABLE CURRENT CARRYING CAPACITY
• Misalkan 20/3.3 kV, 12.5 MVA transformer, direct
buried, 3 core XLPE, SWA, PVC, copper conductor cable.
• Arus pada 20 kV?
• Ifull-load = 12.5 × 106 / 1.73 × 20 × 103
• = 361 A >>>
• Kabel dipasang flat pada trench dengan jarak 0.45 m center
to center dengan ground temperature 20oC.
Flat pada trench dengan jarak 0.45 m – C2C
Ground temperature 20oC.
DAYA TR TEGANGAN (KV)
(MVA) 20 150 500
30 866.03 115.47
40 1154.70 153.96
60 230.94
500 1924.50 577.35
600
KABEL NOMENKLATUR
CODE DESCRIPTION
N MV cable according to DIN VDE 0276
A Aluminium (Al) conductor
[blank] Copper (Cu) conductor
2X Cross-linked polyethylene (XLPE) insulation
S Screen of copper wires and copper tape, helically wound
Screen of copper wires and copper tape over each individual core,
SE
helically wound
Y Polyvinyl Chloride (PVC) sheath
2Y Polyethylene (PE) sheath
(F)2Y Longitudinal water tightness with PE sheath
(FL)2Y Longitudinal and transversal water tightness with Al/PE sheath
0.97
DERATING FACTORS BASED ON IEC 60287

Flat pada trench dengan jarak 0.45 m – C2C

Ground temperature 20oC.
0.97
Flat pada trench dengan jarak 0.45 m – C2C
0.97
Flat pada trench dengan jarak 0.45 m – C2C
0.97
Flat pada trench dengan jarak 0.45 m – C2C
0.97
Flat pada trench dengan jarak 0.45 m – C2C
0.97
Flat pada trench dengan jarak 0.45 m – C2C
0.97
Flat pada trench dengan jarak 0.45 m – C2C
0.97 & 0.87
Flat pada trench dengan jarak 0.45 m – C2C
0.97 & 0.87
0.97 & 0.87

• Rating kabel setelah DERATING adalah:

• = 361/(0.97 x 0.87)
• = 427.78 A
2. SHORT CIRCUIT RATING
• Isc = K × A / √t
• Di mana:
• K – constant:
 Value of k
Temperature
Material Conductor Material
Initial (°C) Final (°C) Copper Aluminium Steel
Thermoplastic 70°C (PVC)  70 160/140 115/103 76/78 42/37
Thermoplastic 90°C (PVC) 90 160/140 100/86 66/57 36/31
Thermosetting, 90°C (XLPE, EDR) 90 250 143 94 52
Thermosetting, 60°C (rubber) 60 200 141 93 51
Thermosetting, 85°C (rubber) 85 220 134 89 48
Thermosetting, 185°C (silicone rubber) 180 350 132 87 47
• A – Penampang kabel, 240 mm2 based on current carrying
capacity
• t – short circuit duration, untuk MV cable menggunakan 1
second
•Isc = 240 × 143 / √1 = 34.32 kA
PERHITUNGAN PENAMPANG KABEL
ISC x √t
S=
K
• S = Luas penampang dalam mm2
• ISC = Arus Hubung-Singkat dalam kA
• T = Fault clearing time (1 detik atau 3 detik)
Contoh
• Arus Hubung-Singkat (ISC) = 50 kA.
• Tripping time sistem 1 detik.
• Berapa ukuran kabel XLPE Aluminium dan XLPE Copper?
XLPE ALUMINIUM CABLE
• Dari formula di atas:
• S= (50× √1)/0.094
• = 531.91
• = 532 mm2.
• Dipilih kabel 3 core 630 mm2.
XLPE COPPER CABLE
• Dari formula di atas:
• S = (50× √1)/0.143
• = 349.65
• = 350 mm2.
• Dipilih kabel 3 core 350 mm2.
SHORT CIRCUIT CURRENT FOR XLPE CABLES
(COPPER CONDUCTOR)
SHORT CIRCUIT CURRENT FOR ALUMINIUM
CABLES (ALUMINIUM CONDUCTOR)
• https://www.ecmweb.com/nec/nec-guidelines-transformer-and-
transformer-feeder-protection
• 0.094 for XLPE insulated Aluminium cables, 0.143 for
XLPE insulated Copper cables
and 0.076 for PVC Insulated Aluminium cables.
Routine tests
• These non-destructive tests are normally carried out on all
lengths manufactured.
• Conductor resistivity
• Spark test on oversheath
• Voltage tests on sheath
• D.C. voltage test on oversheath
Sample tests
• These potentially destructive tests are normally carried out
on every production run.
• Examination of conductor and dimensions
• Hot set test for XLPE insulation
• Insulation and oversheath thickness
• Four hour voltage test
TYPE TESTS
• These destructive tests are normally carried out in addition
to the above tests on commencement of a particular cable
supply to validate its design.
• Electrical type tests including bending and heat cycle
• Non-electrical type tests including mechanical properties
after ageing and tests under fire conditions.
• Number of cores: generally one or three
Solid or stranded aluminium conductors: for applications requiring a lighter cable weight, also often more
economical due to lower aluminium prices.
Stranded copper conductors: for applications requiring a smaller overall diameter and higher transmitting
properties.
Bedding
Bonded or strippable out semi-conducting layer
Water tightness: longitudinal, longitudinal + quasi-radial, longitudinal + radial
Insulation layers (conductor screen, insulation and insulation screen): XLPE, which is more commonly used
for MV cables, or EPR which is more flexible and often better suited to marine and offshore applications.
Metallic screen: to nullify the electric field outside the MV cable. Concentric copper wire screens,
Aluminium foil laminate, or extruded lead alloy sheath.
Twisted three-core cable or triplex
Armouring: for mechanical protection. Aluminium wire armoured for single-core cables, Galvanised steel
wire armour, strip or tape.
Tapes: Separator tapes to facilitate peeling, water-swellable tapes to prevent water ingress, Conductive tape
for core binding.
Outer Sheath: compounds with various properties, tailored to the specific application's requirements,
including resistance to oils, greases, rodents, termites, UV and flame, as well as zero halogen emissions.
• https://electrical-engineering-portal.com/cable-sizing-transformer-
feeder#table-derating-factors