1. EE4503 Electrical Systems Design
Electrical Equipment and Apparatus

2. Topics Introduction to Electrical Equipment and Apparatus
Medium Voltage Equipment
Low Voltage Equipment

3. Equipment Degree of Protection Level: IP
IPxy or IPxyz: IP follow by two or three digit number
x: level of protection against contact or solid material getting into
y: level of protection against liquid
z: level of protection against impact

4. Equipment Degree of Protection Level: IP

5. Electrical Equipment and Apparatus
HV Equipment (High Voltage): more than 36kV
MV Equipment (Medium Voltage): 1kV to 36kV
LV Equipment (Low Voltage): less than 1kV

6. Electrical Equipment and Apparatus
MV Equipment

7. MV Equipment http://www.geelectrical.com/catalog/buylog/15_BL.pdf
Surge Arrestor
Current Transformer / Potential Transformer
Power Meter
50/51 Relay (instantaneous overcurrent relay and ac inverse time over current relay)
Circuit Breaker (IEEE 52)
Disconnecting Switches / Load Interrupter Switches
Fuses

8. Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์
MV Equipment
Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์

9. MV Equipment Lightning Arrester: LA
Operation
Normal: High Impedance so low Leakage Current
Overvoltage: Impedance Drop so Lightning Current goes to ground
Type: Spark Gap Arrester & Arrester without Spark Gap
Rating: Voltage and Discharge Current

10. MV Equipment LA: Spark Gap Arrester
Old type, less uses
Components:
Spark Gap
Varistor
SiC-Arrester
Varistor is the resistor with nonlinear behavior between resistant and voltage
SiC (Silicon Carbine)

11. MV Equipment LA: Arrester Without Spark Gap
Components: Strong Non-linear Voltage dependent e.g Zinc Oxide
MO-Arrester
ZnO-Arrester
MO = Metal Oxide
FRP = Fiberglass Reinforced Plastics

12. MV Equipment Disconnector or Disconnecting Switch (DS)
Use to disconnect the circuit
Disconnect high voltage but low (or no) current circuit
If on-load disconnection, require Load Buster
Create large isolating distance for safety
** For safety, interlocks with other devices

13. MV Equipment Disconnector or Disconnecting Switch (DS)
Manual Operated, Motor Operated, or Pneumatic Drive
Rating: Rated Voltage, Rated Normal Current, Short Circuit Current, BIL
BIL = Basic (lightning) Impulse Insulation Level

14. MV Equipment Earthing Switches: ES
Connect the metal parts to ground
discharging extra charge that left in the circuit.
for the safety when maintain the system.
May interlock with other devices e.g. DS
Rating: Rated Voltage, Short Circuit Current, BIL

15. MV Equipment High Voltage High Rupturing Capacity Fuses: HV HRC Fuses
Protect the electrical system from over- current or short-circuit.
Compose of fuse string and material to suppress arcs.
Some have a “Striker Pin” to indicate the disconnecting.

16. MV Equipment High Voltage High Rupturing Capacity Fuses: HV HRC Fuses
Rating: Maximum Operating Voltage Rating, Continuous Current Rating, Short Circuit Current Rating, Selectivity (cooperate more than one safety devices together)
Special Rating for using with motor: Starting Current & Starting Time

17. MV Equipment Switch Disconnector or Load Break Switch: SD
Able to disconnect circuit at load current
Contain Arc Suppression
Create large isolating distance for safety
Rating: BIL, Rated Voltage, Rated Operating Current, Rated Breaking Current, Rated Short Circuit Making Current

18. MV Equipment SD Arc Suppression Operated by Spring Air Vacuum
Gas (e.g. SF6)
Operated by Spring

19. MV Equipment Instrument Transformer
Voltage Transformer
Current Transformer

20. MV Equipment Voltage Transformers
Transform the high voltage to the measurable voltage level
Do not SHORT circuit the secondary coil
Rating: Burden, Primary Voltage, Secondary Voltage, Permissible Voltage Stress, Accuracy
Measurement: Class 0.1 = 0.1%, Class 0.5 = 0.5%
Protection: Class 3P = 3%, Class 6P = 6%
Burden is the about of power that still give the valid reading (exceptable at 25% or 100% of burden)
Permissible Voltage Stress is the factor of the voltage that VT can still be usable for example, 1.2

21. MV Equipment Current Transformers
Transform the high current to the measurable current level (usually 5A)
Do not OPEN circuit the secondary coil
Some have “OPEN-circuit” protection
Rating: Burden, Primary Current, Secondary Current, Short-circuit Current, Rated Voltage, Accuracy Class

22. MV Equipment Current Transformers
Sometime have two secondary core: protection & measuring cores.
Measuring Core: small saturation factor
Accuracy: Class 0.1 = 0.1%, Class 0.5 = 0.5%
Measuring Core: high saturation factor
Accuracy: Class 5P = 5%, Class 10P = 10%
Accuracy: Class 5P10 = 5% at 10 time rated current

23. MV Equipment Protective Relay
Detect the event and signal circuit breaker.
Usually need CT & VT
Mechanism
Electromechanical Relays
Solid State Relays
Digital Relays

24. MV Equipment Protective Relay
Overcurrent Relay (50, 51)
Ground Fault Relay (50N, 51N)
Directional Overcurrent Relay (67)
Directional Ground Fault Relay (67N)
Directional Power Relay (32)
Distance Relay (21)
Differential Relay (87)
Under Voltage Relay (27)

25. MV Equipment MV Circuit Breaker: MVCB
MVCB is able to break the circuit in the normal load and in the short circuit condition.
MVCB take the order from specific relays to trip.

26. MV Equipment MV Circuit Breaker: MVCB
Need to suppress arcs:
Vaccum
SF6
Rating: Voltage, BIL, Nominal Current, Short Circuit Current

27. MV Equipment MV Contactors
Switch that use for the situation where a lot of open/close circuit happen: e.g. Motor circuit

28. MV Equipment MV Switchgears
Complete set of switching devices, protection devices, measurement devices.
Use at the incoming of the power system and distribute out on the other side

29. MV Equipment MV Switchgears
Enclosure
Busbar
Protection Devices
Measurement Devices

30. MV Equipment MV Switchgears
Cubicle
Compartmented
Metal - Clad

31. MV Equipment Ring Main Unit: RMU
Like Switchgear
Like Selector Switch

32. MV Equipment Transformer
Bridge to Low Voltage system
Categorized by insulator & heat ventilation
Liquid-immersed Transformer
Oil-type Transformer
Less-Flammable Liquid-insulated Transformer
Dry-Type Transformer

33. MV Equipment Transformer
Usually contain over-heat protection
Sensors: 3 levels (start ventilation, warning, shutdown)
Temperature-Relay
Protective Enclosure (even dry type)
Cast Resin Transformer: can overload by % using extra heat ventilation

34. Electrical Equipment and Apparatus
LV Equipment

35. LV Equipment Circuit Breaker
switch and able to disconnect circuit when there is overload or short-circuit
Two main types:
Molded Case Circuit Breaker (MCCB)
Air Circuit Breaker (ACB)
Rating: Continuous Current, Interrupting Capacity

36. LV Equipment Circuit Breaker - MCCB
MCCB is made of strong polymer material.
Miniature Circuit Breaker (MCB) used in the consumer unit: 1, 2 or 3 poles for IC around 3kA to 10kA.
Earth Leakage Circuit Breaker (ELCB) or Residual Current Circuit Breaker: 10mA or 30mA

37. LV Equipment Circuit Breaker - MCCB
Standard CB: usually around 100AF to 2,500AF and the IC is around 18kA to 30kA
High Interrupting Capacity Circuit Breaker: Used when there is a chance of high short-circuit current. IC is usually very high 25kA to 100kA.
Current Limiting Circuit Breaker: Used for very fast breaking and very high short-circuit current

38. LV Equipment Circuit Breaker - ACB
Usually large circuit breakers
Two types:
Fixed Type
Drawout

39. LV Equipment Circuit Breaker – ACB v.s. MCCB
ACB’s components can be accessed
MCB is required no maintenance
ACB is suitable for large systems when the short circuit current is high

40. LV Equipment Circuit Breaker – Continuous Current
The amount of current that can pass thru the CB under the given ambient temperature
Usually manufactures usually offer one frame with many rating:
Ampere Frame (AF): maximum rating for the specified structure
Ampere Trip (AT): selected rating for each CB

41. LV Equipment Circuit Breaker – Interrupting Capacity
Interrupting Capacity (IC) or Breaking Capacity is the maximum short-circuit current that the CB is still functional.
IC has to be tested under many parameters, e.g. voltage, power factor, harmonics, etc.

42. LV Equipment Circuit Breaker – Tripping Unit
The main function of the CB is to properly trip the system
Thermal – Magnetic
Solid State Trip

43. LV Equipment Circuit Breaker – Thermal & Magnetic Trip
Thermal (Bimetal) Device: Small Overload about 125% of rated current & Long Time Delay
Electromagnetic Device: Large Overload about 10 times of rated current & Instantaneous Trip Time

44. LV Equipment Circuit Breaker – Thermal & Magnetic Trip
Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์

45. LV Equipment Circuit Breaker – Thermal & Magnetic Trip

46. LV Equipment Circuit Breaker – Thermal & Magnetic Trip

47. LV Equipment Circuit Breaker – Thermal & Magnetic Trip

48. LV Equipment Circuit Breaker – Solid State Trip
Use electronics to decide the trip action
High accuracy and reliability
Can be configuration tripping pattern in many ways

49. LV Equipment Low Voltage Fuses
Breaking the circuit by melting the metal when over current.
D-fuse
D0-fuse
NH (HRC) fuse (usually in industries)
Rating: Nominal Current, Nominal Voltage, Short-circuit Current

50. LV Equipment Low Voltage Fuses – D & D0 Fuse

51. LV Equipment Low Voltage Fuses – HRC Fuse
Many sizes (dimensions)
Rated current from 6A to 1,250A
Short-circuit current up to 100kA

52. LV Equipment Panelboards
The equipment that takes the main power in and distributes power out to many feeder.

53. LV Equipment Panelboards - components
Enclosures to protect the inside components
Busbars conducts the current to Branch CB and also hold the CB
Circuit Breakers
Main CB
Branch CB: Plug-in unit

54. LV Equipment Panelboards – consumer units
IC is about 10kA
Single phase
4, 6, 8, 12, 16 branches
Main CB: AT=16, 20, 32, 45, 63, 70, 80, 110A
Three phases
12, 18, 24, 30, 36, 42 branches

55. LV Equipment Panelboards – industrial units
Three phases
12, 18, 24, 30, 36, 42 branches
Usually being used as “Load Center”
Main Lugs: is mainly for distributing load
Main Circuit Breaker: complete with main circuit breaker

56. LV Equipment Panelboards – industrial units

57. LV Equipment Measuring Instruments
Ammeter (I, A)
Voltmeter (V, V)
Frequency Meter (F, Hz)
Power Factor Meter (pf)
Power Meter (kW)
Energy Meter (kW-hr)
Current Transformers
Universal Measuring Device
No need to have voltage transformers because “LV Equipment”

58. LV Equipment Magnetic Contactors
Switch controlled by electrical power
Rating: Utilization Category
AC1: general load p.f.>0.95
AC2: slip-ring motor (2.5 x In)
AC3: squirrel cage motor (5 to 7 x In) disconnect at load
AC4: squirrel cage motor (5 to 7 x In) and disconnect at the starting current

59. LV Equipment Magnetic Contactors - usage
Commonly use in the motor starting circuit
Direct-on-line Motor Starter (DOL)
Start-Delta Motor Starter (Y)
Auto Transformer Motor Starter
Resistance Motor Starter

60. LV Equipment Switchboards
Distribution panel that distribute the main power unit (e.g. out of transformer) to the branch circuit
Standard: height around 2 to 2.2m
Enclosure from steel sheet
Protect against physical damage, thermal damage and erosion

61. LV Equipment Switchboards
Busbar attached inside the enclosure
Circuit Breaker: Main CB & Feeder CB
Measuremnet Instrument
Protection device (Ground Fault Protection, Lightning Arrestor)
Follow standards (e.g. IEC60439)

62. LV Equipment Switchboards
Rating: Rated Voltage, Rated Current, Rated Short-Circuit Current

63. LV Equipment Busways or Busduct
Equipment that transmits power from one place to the other

64. LV Equipment Busway or Busduct
Rating: Indoor or Outdoor usage, Voltage Drop, Rated Current, Short-Circuit Rating
Busway can be reduced as long as the protection is still valid and the extension is no longer than 15.2m (50 ft)

65. Reference Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์
Depend on the area, end-user can connect to the “meter” of the authority in three ways.