2. The 2016-2017 Auxiliary Electric Team:
Justin Griffin
Protective Relaying
Overcurrent and Differential Relaying
Lighting
Ethan Wilcox
Substation Arrangement and Location
Neutral Grounding Methods
Equipment Location
Dinh Pham
UPS/Inverters
Battery Sizing
Black Start Generator
Douglas Heller
Lightning Protection
Load List
One Line
Natnael Hailemichael
Power Transformers (MAT/RAT/GSU)
Instrument Transformers (CT/PT)
Phasing
Mekebeb Geremew
PUS
Bus Duct
MV Bus Transfer Schemes
Rafael Alvarez
Motor Control Center
Motors
Variable Frequency/Speed Drives
Mariana Da Silva Bozan
SUS
Electrical Installation, Conductors, Wiring
Three Line Diagram

3. Power Transformers Instrument Transformers Phasing of the Electric System
Natnael Hailemichael

4. Transformer Sizes and Their %Z
Decisions we have made:
Two MATs and two RATs (same size RAT and MAT)
Both MATs running with fans on (ONAN/ONAF/ONAF)
GSU output increased from 275MVA to 290MVA
Minimum impedance for fault study
Maximum impedance for voltage regulation
All SUS transformers have 2.5MVA and 5% impedance rating

5. Power Transformer Protection
Devices that indicate the status of the physical quantities of the transformer
Buchholz Relay
Oil Level Indicator
Devices measuring electrical quantities affecting the transformer
Over Current Relay
Ground Fault Relay
Lightning Arrestor
Fire Protection
Reinforced concrete for walls, roof, and floor
Fire resistance rating of 3hrs
Deluge system to sprinkle water during fire

6. Current Transformers Two types of current transformers
C type: ratio error can be determined by calculation from the excitation curve
T type: Ratio error must be determined by test due to significant leakage flux
We will be using the “C type” current transformers in our design
Sizing our CTs (SUS level):
Based on the 6.9KV switchgear, we choose a CT rating of C250
CT ratio: S = 2.5MVA, V = 6.9KV, Solve for current
I = 209A. We want the ammeter needle to be at 3/5 of the way at full load so CT ratio = 209:3
Actual CT ratio = 350:5 so we choose 400:5 as our CT ratio

7. Current Transformers 400 : 5 CT rating
For metering, you want to be on the linear level
For relaying, you can be above the knee point.

9. Questions?
Natnael Hailemichael

10. Bus-Duct Primary Unit Substation MV Bus Transfer Schemes
Mekebeb Geremew

11. Isolated Phase Bus-Duct
The momentary current is depends on what equipment it’s connected to.
Ratings (Current ratings based upon 40oC ambient)
Rating voltage 18 kV rms
Basic impulse insulation level 150kV
Rated continuous current 12KA.
Momentary current 156 kA
Standards and Codes:
American National Standards Institute (ANSI IEEE-C37.23)
National Electric Code (NEC) (NFPA No. 70)

12. Cable Bus Cable Bus and Bus Bar systems have similar properties
Voltage Drop, Power Consumption, En- closure Size, System Weight as well as short circuit capacities
Advantages of cable bus
Reliability
Service Life
Support Requirements
System Maintenance
Flexibility
Material Cost

13. PUS Bus rating: Max/Nominal voltage 15/ 6.9 kV rms
Basic impulse insulation level 95KV
Rated continuous current 1.5KA
Max fault current 25KA
Breaker rating:
Max/Nominal voltage 8.2/6.9KV

14. PUS Continued MV Starter rating: Max/Nominal voltage 7.2/6.9KV
Basic impulse insulation level 95KV
Rated continuous current 800A
Available momentary current rating is 25KA rms symmetrical
Standards:
IEEE Std C ™-2015, IEEE Standard for Metal-Clad Switchgear.
This standard provides information essential to designing and testing of metal-clad switchgear

15. MV Bus Transfer Schemes
Fast transfer
High Speed, Fast transfer.
Transient torques are reduced due to speed of transfer.
Transfer of complete bus with reduced interruption of process.
Avoids parallel transfer operation.
Avoids exposure to breaker failure effects.
Relevant Standard: ANSI C50.41

16. Questions?
Mekebeb Geremew

17. Motor Control Center (MCC) Variable Frequency Drives Motors
Rafael Alvarez

18. Motor Control Center
A floor-mounted assembly of one or more enclosed vertical sections typically having a horizontal common power bus for the distribution of power and principally containing combination motor-control units.
Have both fault capability and overcurrent capability in every bucket
NEMA ICS , UL 845, NEC, IEEE

19. Motor Control Center Voltage size: .48 kV
Amperage Sizing: Smallest breaker in the MCC that would protect against overcurrent under full load continues conditions
Physical limitations
More MCC’s mean higher reliability

21. Variable Frequency Drives and Motors
AC induction motors are fixed speed devices because the motors operate from a constant frequency power source
VFDs are electronic systems that convert AC to DC and then simulate AC with a changed frequency, thereby changing the speed of the motor
Advantage comes from running fans, pumps, or whatever other processes at different speeds
Nameplate would tell us if the motor is able to use a VFD on a motor
Example: Matching the pump curve with the motor efficiency curve. Increased efficiency equal savings in operating cost

22. Variable Frequency Drives and Motors
Motors started with a VFD will be further away from the time current curve because there is a lower inrush current when the motors are started at a lower speed.
The faster a motor is started, the more life that is taken out of it. Starting an induction motor at a lower speed will increase it’s longevity.
Higher inrush currents cause heating and stress in the components of a motor.
Motor starters, cables, bearings, insulation breakdown
More expensive startup cost with a lower maintenance cost. Translates to a lower fixed cost

23. VFD and Motor Example
Pump curve shows the relationship between pressure and flow. As the flow increases the pressure drops.
Red line shows needs of the system. The extra flow causes the resistance to increase
Without an added device, the system will have a single operating point. This point shows the maximum flow needed at the maximum demand.

24. VFD and Motor Example
VFD pump allows control of the pump’s speed electrically, while using only the energy needed to produce the given flow.
Pump would be continuously flowing
Results in longer life for the motor as well as a lower operating cost

25. Questions?
Rafael Alvarez

26. Secondary Unit Substation Electrical Installation Three Line Diagram
Mariana Bozan

27. Secondary Unit Substation
50HP motors and below do not contribute to the fault
𝑀𝑉𝐴 𝑓𝑎𝑢𝑙𝑡 = 3 𝑥𝐿𝑅𝐴 𝐾𝐴 𝑥 𝑉(𝐾𝑉) 𝑋" 𝑑 or 𝑀𝑉𝐴 𝑓𝑎𝑢𝑙𝑡 = 𝑀𝑉𝐴 𝑟𝑎𝑡𝑒𝑑 𝑍 𝑝𝑢
MVA method:
Series : 𝑀𝑉𝐴 1,2 = 𝑀𝑉𝐴 1 𝑥 𝑀𝑉𝐴 2 𝑀𝑉𝐴 1 + 𝑀𝑉𝐴 2
Parallel : 𝑀𝑉𝐴 1,2 = 𝑀𝑉𝐴 1 + 𝑀𝑉𝐴 2

28. Secondary Unit Substation
Fault Contribution at SUS bus:
21𝐴|2.23 𝑀𝑉𝐴 NO 21𝐵|3.39 𝑀𝑉𝐴
22𝐴|2.91 𝑀𝑉𝐴 NO 22𝐵|1.43 𝑀𝑉𝐴
23𝐴|0 𝑀𝑉𝐴 NO 23𝐵|1.42 𝑀𝑉𝐴
24𝐴|2.43 𝑀𝑉𝐴 NO 24𝐵|1.25 𝑀𝑉𝐴
25𝐴|2.41 𝑀𝑉𝐴 NO 25𝐵|2.41 𝑀𝑉𝐴

29. Secondary Unit Substation
Fault Contribution of SUS at PUS level ( Considering 2.5 MVA transformers with 𝑋" 𝑑 =5%):
21𝐴|2.13 𝑀𝑉𝐴 𝐵|3.17 𝑀𝑉𝐴
22𝐴|2.75 𝑀𝑉𝐴 𝐵|1.4 𝑀𝑉𝐴
23𝐴|0 𝑀𝑉𝐴 𝐵|1.4 𝑀𝑉𝐴
24𝐴|2.32 𝑀𝑉𝐴 𝐵|1.22 𝑀𝑉𝐴
25𝐴|2.3 𝑀𝑉𝐴 𝐵|2.3 𝑀𝑉𝐴
Total contribution of MCC`s and SUS to PUS (not considering MV motors):
Total on PUS 21A = 9.5MVA
Total on PUS 21B = (Fire Pumps MCC) = 10.7MVA

30. Electrical Installation

31. Electrical Installation
Factors such as temperature, number of conductors, insulation will affect the ampacity of the cable.

32. Three Line Diagrams

33. Three Line Diagrams
Source : Electroswitch website

34. Three Line Diagrams

35. Three Line Diagrams

36. Questions?
Mariana Bozan

37. Protective Relaying Overcurrent and Differential Relaying Lighting
Justin Griffin

38. MAT Differential Relay
CT secondary connection should be opposite of primary. To compensate for the 30 degree shift in a delta- wye transformer.
Source : Power System Analysis & Design (5th Edition)

39. MAT Differential Relay-Cont.
Find primary and secondary Currents for transformer.
Find secondary current for CTs (primary and secondary)
Choose Appropriate CT ratio
Choose Tap ratio
Keep percent mismatch below 10%

40. Lighting :Zonal Cavity Ratio Method
Takes into consideration the effect that inter-reflectance has on the level of illuminance.
Factors to consider
Area of room.
Reflectance percentage off ceiling, work plane, and floor.
Height of lamps from ceiling.
Height of work surface from floor.
Amount of lights in room.

41. Step 1 : Find Cavity Ratios
Source : Holophane®

42. Step 2: Determine Cavity Reflectance For Ceiling and Floor
Ρcc : Ceiling Cavity Reflectance
Ρfc : Floor Cavity Reflectance
Pw : Wall Reflectance
Source : Holophane®

43. Step 3: Find the Coefficient of Utilization (CU)
CU final = CU (20% floor) x Multiplier for actual ρfc.
Source : Holophane®

44. Step 4: Compute Average Illuminance Level
LLF (Light Loss Factor): The amount of light lost throughout life cycle of the lamp.
Source : Holophane®

45. References
Holophane® aesl.hanyang.ac.kr/class/are141/zonal%20cavity%20ratio%20method.pdf
ABB C : Type HU & HU-1 Transformer Differential Relays

46. Questions?
Justin Griffin

47. Neutral Grounding Methods Substation Arrangement Equipment Location
Ethan Wilcox

48. Low Resistance Neutral Grounding
Resistors rated for 10 seconds with max temperature increase of 760C
200A to 400A for 6.9kV and above
100A to 400A for 2.4kV to 4.16kV
Our PUS level motors and switchgear then require 10 Ohm resistors if rated for 400A (fault study indicates about 230A)
6.9kV / 1.73 = ~4000 V / 400 A = 10 Ohms
Relays are configured to trip before the 10 seconds is up

49. High Resistance Neutral Grounding
Used for voltage levels below 2.4kV – so we will use this at 480V SUS/MCC level
Must limit to 5A to 10A
SUS -> 480 V / 1.73 = V / 5A = 55.5 Ohm or 10A = 111Ohm

50. Sample Touch Potential Calculation
Source: electrical engineering portal – Jignesh Parmar

51. Considerations for grounding
Grounding of our system is extremely important for protective relaying
Limiting current – reduces sensitivity
Too much current – reduces selectivity
Errors in calculations cost money!
Source: IEEE C62

52. Substation Arrangement / Equipment Location
Sources should be as close as possible to their loads
Long cable lengths present voltage drop issues
NEC 210 says total voltage drop between feeder and source should not exceed 5%
Refer to table 9 in NEC for values in voltage drop calculations (V = I*R)

53. Substation Arrangement / Equipment Location
Larger conductor sizes result in higher resistances – more voltage drop
Be mindful of NEC – minimum ampacity and size should be observed or fault conditions run the risk of vaporizing your wires

54. Questions?
Ethan Wilcox

55. Battery Sizing Uninterruptible Power Supply Black Start Generator
Dinh Pham

56. Load list

57. Load Classifications L1- Continuous load Solid State Relays
Control Relays
Indicating Lamps
Emergency Bearing Oil Pump
Turning Gear Motor
Inverter 75KVA
Stack lighting
L2 – Momentary load
Breaker Tripping
Motors Staring
L3- Non-continuous load
Closing breakers

58. Battery Sizing A1 = L1 + L2 = 1868A (1min) A2 = L1 = 882 A (35 min)
1868 +(882*35) +(897*24) = 54266A/60 =904AH
Battery sizing = 904 AH

59. Battery Sizing

60. Starting DC Motor 25 HP 125VDC 80% efficiency = 186A
Inrush current = 125VDC/0.1 ohm = 1250A
372A=125VDC/(0.1+X)
X = (125VDC/372A) -0.1= ohm

61. Battery Sizing Relevant Standards:
IEEE Standard IEEE Design Guide for Electric Power Service Systems for Generating Stations
IEEE Standard Recommended Practice for Sizing Large Lead Storage Batteries for Generating Stations and Substations

62. Uninterruptible Power Supply (UPS)*
Transformer-based UPS
Did not oversize the UPS
Load up the inverter as much as possible *
*_ Each Charger will have a Polarity Ground Detector Circuit built in

63. Uninterruptible Power Supply (UPS)
Relevant Standard
IEEE Standard 944 -IEEE Recommended Practice for the Application and Testing of Uninterruptible Power Supplies for Power Generating Stations

64. Sizing the Black Start Generator
The auxiliary load (30MVA)
The percent required for startup is 20%
30 MVA x 0.2 = 6 MVA ( Total load required to start the unit )
6000 HP x 0.2 = 1200 HP ( Total demand on ID Fan motor)
Remove the biggest load (ID fan) to determine the running load
Starting ID fan is starting demand
Maintain minimum voltage when starting the biggest load

65. Black Start Generator Relevant Standards:
IEEE Standard Guide for Design, Operation, and Integration of Distributed Resource Island Systems with Electric Power Systems
[2] Turner, Steve. Considerations For Generator Protection During Black Start Conditions. 1st ed. IEEE, Print.
Grande-Moran, Carlos. Black Start Studies. 1st ed. Siemens, Print.

66. Questions?
Dinh Pham

67. Lightning Protection Load List One Line
Douglas Heller

68. Lightning Protection

69. Lightning Protection Discussed previously the tools for protection
How do we determine the areas in our plant that are at risk of a lightning strike?
Lightning strike at Torrens Island Power Station near Adelaide, Australia Anthony James :: scribol.com

70. Lightning Protection The Rolling Sphere Method
Helps determine areas of the plant that are susceptible to lightning strikes
A large sphere is rolled over the lightning protection in the plant
The radius of the sphere is determined by the characteristics of the lightning and the system it is protecting
Any equipment touched by the sphere is at risk of a lightning strike
Top right ::
All others ::

71. Lightning Protection The Rolling Sphere Method
Sphere radius is based primarily on the stroke current of the lightning bolt
Somewhat counterintuitively, protecting for less powerful lightning bolts offers the most protection
Less stroke current means a smaller sphere
Lightning is a highly probabilistic phenomenon, and the sphere must be calculated based on lightning data in the region of the plant
Data available from Vaisala Lightning Detection Network
Top :: W H
Right :: “Monte Carlo…” Gatta, Geri, Lauria, Maccioni

72. Lightning Protection Relevant Standard:
IEEE Std 998™-2012 (Revision of IEEE Std ) IEEE Guide for Direct Lightning Stroke Shielding of Substations

73. Load List

74. MCC
SUS
Load List
PUS

75. One Line

76. One Line Some Key Features:
Two pairs of equally sized two- winding MATs and RATs
Fast Transfer capability
High reliability/Low overhead
Emergency Diesel
Local Black Start Generator
Senior Design 2017 One Line

77. Questions? Douglas Heller
Senior Design 2017 One Line

78. Hackerman Approved (tm)