1. EE4503 Electrical Systems Design
Cable

2. Topics Introduction to Cables Cables for low voltage
Cables for high voltage
Cable selection

3. Cables Functionality Components
Conduct electrical power from one point to other
Components
Conductor
Insulator (optional)

4. Cables - Conductor Physical Material Solid
Strand: flexible, reduce skin effect
Material
Copper
Aluminum

5. Cables - Conductor

6. Cables - Insulator
Prevent the physical contact: between two cables, cable-to-ground
Physical durable e.g. impact, heat
Chemical durable, e.g. erosion
Commonly used
Polyvinyl Chloride (PVC)
Cross linked Polyethylene (XLPE)

7. Cables - Insulator

8. Cables for High Voltage
Withstand the high voltage: insulator (if any) need to be good.
Long distance transmission: Cable cost & Installation cost (e.g. electricity pole)
Two main types
Bare Wires (reduce cost)
Insulated Wires
Complication of Cable for High Voltage is the high voltage.

9. High Voltage Cables Bare Wires
Made of Aluminum for lower cost
Transmission system (not distribution system for safety): Reduce usage: animals, accident, etc.
AAC: All Aluminum Cable
AAAC: All Aluminum Alloy Cable
ACSR: Aluminum Conductor Steel Reinforced

10. High Voltage Cables Bare Wires
AAC: Basic type, for shorter span
AAAC: Improve the property of Aluminum by making it as an alloy  stronger, larger span, corrosion resistance (e.g. sea)
ACSR: Insert the steel in the core to have more tension.

11. High Voltage Cables Insulated Wires
For safety and prevent interruption
PIC: Partial Insulated Cable
SAC: Space Aerial Cable
XLPE: Cross-linked Polyethylene
hire-fire-crew-hot-air-balloonist_n_ html

12. High Voltage Cables Insulated Wires - PIC
Should not have any directly contact to human.
Extruded conductor shield is made of semi-conducting material to manage the electric field.
Insulation only to protect line to line contact.

13. High Voltage Cables Insulated Wires - SAC
Have extra shealth.
Should not have any directly contact to human.

14. High Voltage Cables Insulated Wires - XLPE
Conductor -> Copper
Conductor Shield -> made of semi-conducting material, allow the uniform distribution of electric field, prevent break down
Insulation
Insulation Shield -> made of semi-conducting material, to shield the electric field
Jacket / Shealth -> To protect the cable
Can be used both in Air and underground (humidity)

15. Cables for Low Voltage Below 750V Conductor: Aluminum or Copper
Insulator: PVC or XLPE
Number of Conductor: 1 or many
Special Type to suite the need: Fire Retardent

16. Cables for Low Voltage (see pdf)
PVC
NAY (aluminum)
THW
VAF
VCT
NYY (double shealth)
XLPE CV MI
Fire Safety Cable
Flame Retardant
Fire Resistant
Complication of Cable for Low Voltage is the usage.
MI Cable is very durable cable with metal shealth.
Flame Retardant -> stop spread of fire
Fire Resistant -> can operate for a period of time

17. Cables for Low Voltage Fire Resistant Cable
Flame Retardancy
Flame Propagation
Acid and Corrosive Gas Emission
Smoke Emission
Fire Resistance (Circuit Integrity)

18. Cables for Low Voltage Fire Resistant Cable
Fire Alarm System
Building Automation System
Emergency Lighting System
Public Address System
Standby Power System
Computer Network System
Closed Circuit TV System
Elevators and Escalators System
Fire Pumps and Pressurized Stairs
Etc.

19. Assignments
Take pictures of the cable that you can see and classify the types of those cables.
Take pictures of the name-plates

20. Cable Selection
Usage: Table 5-16 (EIT Standard ) for low voltage cable
Rated Voltage: 300V or 750V
Rated Current
Multiple Conductors
Voltage Drop
Rated Voltage is straight forward: either 300V or 750V

21. Cable Selection – Rated Current
Size of Conductor
Type of Insulator
Ambient Temperature
Installation Conditions:
Calculation: BCC - Technical_data_Cable
Table: BCC - InstallationGuide, AS_NZS_ _2009
Rated Voltage is straight forward: either 300V or 750V
Low voltage has so many possibility installation method.

22. Cable Selection – Rated Current Installation Conditions (3.1)
Handout: BCC - Installation Guide.pdf

23. Cable Selection – Rated Current Installation Conditions (3.1t)
Handout: BCC - Installation Guide.pdf

24. Cable Selection – Rated Current Installation Conditions (3.2)
Handout: BCC - Installation Guide.pdf

25. Cable Selection – Rated Current Installation Conditions (3.2t)
Handout: BCC - Installation Guide.pdf

26. Cable Selection – Rated Current Installation Conditions (3.3)
Handout: BCC - Installation Guide.pdf

27. Cable Selection – Rated Current Installation Conditions (3.3t)
Handout: BCC - Installation Guide.pdf

28. Cable Selection – Rated Current Number of Cables in a Conduit
Handout: BCC - Installation Guide.pdf

29. Cable Selection – Multiple Conductors
To increase the rated current
Handout: BCC - Installation Guide.pdf

30. Cable Selection – Multiple Conductors
Only for cable from 50 sq.mm. and up
Same type of cables
Same length
Same wiring method

31. Cable Selection – Voltage Drop
Voltage drop due to the impedance of the cable
NEC
Main incoming to load: no more than 5%
Feeder: no more than 2%
Branch Circuit: no more than 3%

32. Cable Selection – Voltage Drop
Zcable
Zload
220 V (AC)

33. Cable Selection – Voltage Drop
Load: 𝑍 𝑙 is from the consumption and power factor: 𝑝𝑓= 𝑅 𝑙 𝑍 𝑙 or cos −1 𝑝𝑓 = 𝑅 𝑙 𝑍 𝑙
Cable: 𝑍 𝑐 is from the table ( 𝑅 𝑐 and 𝑋 𝑐 )
𝑋 𝑐 depends on the wiring configurations.

34. Cable Selection – Voltage Drop Calculation
Use the normal voltage divider in the calculation.
𝐸 𝑠𝑜𝑢𝑟𝑐𝑒 = 𝐸 𝑐 +𝐸 𝑙
𝐸 𝑠𝑜𝑢𝑟𝑐𝑒 = 𝐼∗(𝑅 𝑐 + 𝑗𝑋 𝑐 ) +𝐸 𝑙
????

35. Cable Selection – Voltage Drop Calculation
visualisation_basse_def.pdf

36. Cable Selection – Rated Current Calculation
visualisation_basse_def.pdf

37. Equivalent Circuits Impedance: table for PVC cables
𝑅 𝑐 =𝑅∗𝐿 and 𝑋 𝑐 =𝑋∗𝐿
Size ( 𝒎𝒎 𝟐 )
Resistance
( 𝒎𝛀 𝒎 )
Reactance
2.5
7.400
0.155 4
4.625
0.141 6
3.083
0.131 10
1.850
0.121 16
1.156
0.113 25
0.740
0.107 35
0.529
0.103 50
0.370
0.100
Size ( 𝒎𝒎 𝟐 )
Resistance
( 𝒎𝛀 𝒎 )
Reactance 70
0.264
0.097 95
0.195
0.096
120
0.154
0.094
150
0.123
0.092
185
0.100
0.091
240
0.077
0.090
300
0.062
0.089
400
0.051
0.088
Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์

38. Cable Selection – Rated Current From Table
Voltage Drop/Amp/km
visualisation_basse_def.pdf

39. Cable Selection – General Rules
20% to 25% factor.
Using current or VA (not power).

40. Cable Selection – Examples
Water Heater 6kW
in Air or in Metal Conduit
Microwave 2,300VA
Industrial Heater 40kW, 400V 3phase
40oC or 50oC
6mm2 in Air and 10mm2 in Metal Conduit
2.5mm2
25mm2 and 35mm2

41. Cable Selection – Examples
Motor 37kW, 400V, In=72A
DOL & Star-Delta
Motor 60kW, 400V, pf.=0.8
Room
receptacles 2.5kVA
lighting 500VA
6mm2 in Air and 10mm2 in Metal Conduit
2.5mm2
25mm2 and 35mm2
35mm2 and 25mm2 (nominal current = nominal current (because of start-delta)/(root 3) and 6 wires is required reduction factor of 0.82)

42. Handout BCC - Installation Guide
HELUKABEL - Installation Operating Conditions
AS_NZS_ _2009

43. Reference Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์
Thai Electrical Code 2002: EIT Standard
Electrical Installation Guide 2010: schneider-electric
Depend on the area, end-user can connect to the “meter” of the authority in three ways.