1. What is a substation?
 Location for automatic protective devices
 Interconnects transmission lines
 Permits switching of system equipment.
 Directs flow of power
 Detects and isolates faulted system
components.
A properly planned and designed substation is essential for the
reliable operation of the electric system.
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2. Design Objectives
•Achieve reliability and
flexibility
•Satisfy electric system
requirements
•Minimizing investment
costs
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3. Needs Determination
The existing “Electric System” is analyzed to
determine the need to build new or improve existing
substation facilities.
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4. Design
Considerations
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5. Analysis Paralysis
Through the planning process, system studies
are conducted in order to properly design the
substation.
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6. Costs
Substations are capital-intensive
construction projects that require long
term strategic planning.
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7. Budgeting
 Preliminary equipment layouts ballpark the costs
and establish the broad requirements.
 Real-Estate Site, size, and location affect the
bottom line.
 Long lead Items - ordered ahead of time.
 Financing Bond issues
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8. Basic single line design
 Develop a single line of the station and bus
configuration.
 General concept of substation
 Physical layout and location of major
equipment and steel structures
 Equipment and materials specifications
 Electrical and safety clearances based on
IEEE standards
IEEE 1427 Guide for Recommended Electrical Clearances and Insulation Levels
in Air Insulated Electrical Power Substations. 8
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9. Bus Configurations
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10. Physical layout
 Indoors?
 Indoors the standard is Metal Clad Arc Flash IEEE
1584 guide to determine the arc flash hazard
distance to which employees could be exposed
during their work.
 Gas insulated switchgear (GIS)
 Indoor
 Outdoor
 Outdoors? Air insulated
 High profile
 Low profile 10
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11. Substation Footprint
IEEE 1427™, “Guide for Recommended Electrical Clearances and Insulation Levels
in Air Insulated Electrical Power Substations.
 Equipment foundations and plot plan.
 Locations of equipment and how they are connected to
each other.
 Physical orientation of the substation on site
 Incoming and outgoing power lines.
 Electrical clearances based on basic insulation level
 Spacing between equipment
 Equipment installation, maintenance and removal
access.
 Vehicle and personnel access 11
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12. Basic Impulse Level (BIL)
 Lightning, circuit breakers and high voltage switches can
create voltage surges that can be very damaging to
electrical equipment.
 The basic impulse level “BIL” of equipment measures its
ability to withstand surges and indicates dielectric
strength.
 When power system components are designed with
sufficient clearances and insulation to withstand these
surges, the design is known as the Basic Impulse Level.
 BIL dictates the phase to phase and phase to ground
clearances and minimal spacing between components.
 14.4kV = 110 BIL
 69kV = 350 BIL
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 230kV = 900 BIL 03/27/12

13. Component Spacing
System kV BIL kV A B C D E F G H I J K L N P
230 1050 13 13 18 18 48 24 24 22 17 17 20 48 18 262
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14. Structure Loads
Designed for mechanical and electrical
forces.
Seismic loads
Dead loads
 Line support, switches, insulators,
phase wires, potential transformers
Wind loads
Operating loads
Short circuit forces
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15. Foundations
 Foundations transmit loads from structures
and equipment to soils
 Many soil types require different designs.
 Identify geotechnical information required
 Soil boring plan and specifications
 Lab testing
 Geotechnical report
 Concrete design
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16. Essential Ground Design Elements
IEEE 80-2000 Guide for Safety in AC Substation Grounding
1. Data for soil resistivity, fault clearing times, and fault
magnitude.
2. Conductor and ground rod layout, location of shield
wires and feeder neutrals.
3. Know the material used and the depth of burial.
4. More ground rods and larger grids reduce the touch and
step potentials.
5. Safe designs are required by IEEE 80, 81 and the NESC
The metal to metal touch voltages between metallic objects or structures
bonded to the ground grid is assumed to be negligible. However, the metal
to metal touch voltages between metallic objects bonded to the grid and not
bonded to the grid may be substantial. 16
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17. Step and Touch
 Primary purpose is to assure that “during fault
conditions” a person in the vicinity is not exposed
to critical electric shock. The design must reduce
the voltage individuals receive when they are in
contact with equipment during fault conditions
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18. Protective Relaying
 Modern relays are Intelligent Electronic
Device’s (IED) that replace older electro-
mechanical relays
 Detect abnormal or undesirable system
operating conditions
 Initiate operation of circuit-interrupting
devices
 Provide remote control and data
monitoring
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19. Protection Zones
 Based on the single line there will be multiple
zones of protection which protect the
equipment inside the substation.
 In the event of a fault being detected. The
protective relays determine the fault location
and open the circuit breakers clearing the fault.
 Initiate back-up protection operations when
necessary.
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20. Surge protection
IEEE Std. 998-1996, Guide for Direct Stroke Shielding
Substation design involves more than installing circuit
breakers, transformers, and relays. Significant capital
investment and reliability standards require attention to
prevent surges (transient voltages) from entering the
facility. These surges can be direct lightning strokes on the
substation or on connected transmission lines.
l Evaluate significance of facility being protected.
l Evaluate geographical thunderstorm exposure.
l Design suitable system of protection.
l Evaluate the cost and effectiveness of the design.
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21. Seismic Thoughts
IEEE Std 693 - 2005 IEEE Recommended Practice for Seismic Design for Substations
 Prior to 1970 seismic requirements were minimal.
 Equipment commonly includes brittle materials
such as porcelain.
 When two or more structures are mechanically
linked by electrical conductors, they will interact
with each other.
 Equipment may be installed with little or no slack
for a “clean” look.
 Ideally, link the equipment so the two components
can move independently. 21
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22. Material & Equipment
Specifications
 IEEE
 A document that specifies, in a complete,
precise, and verifiable manner, the
requirements, design , behavior, or other
characteristics of a system component.
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23. Transformers
IEEE C57.12.36, Standard Requirements for Liquid-Immersed Distribution
Substation Transformers
Oil cooling
230-69kV Wye-Delta Connection +/- 30 degrees
69-12kV Delta-Wye Connection +/- 30 degrees
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24. Air insulated Circuit breakers
 Make, break and carry normal load currents.
 Make and break abnormal currents (short circuit).
http://animatedmanuals.com/S2%20anim.html
 Dissipates the energy in the arc by lengthening and cooling
the arc before interrupting at current zero
 Live or dead tank design
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25. Gas insulated Switchgear “GIS”
C37.123-1991 IEEE guide to specifications for GIS
 Conductors are enclosed in a metallic housing in which a
compressed gas sulfa hexafluoride (SF-6) is the primary
insulating system
 Compact, multi-component assembly of breakers and buses.
 No live parts meets arc flash requirements.
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26. Disconnect Switches
Isolate major equipment from the electric
system and provide a visible open.
Non-load breaking device designed to open and
close an electric circuit.
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27. Capacitor Banks
Primary purpose is power factor correction.
Back-to-back switching can produce high peak
transient in-rush current values.
These currents can exceed the available fault current
levels at the bus.
These currents can damage substation equipment
Appropriate precautions taken during the design
process.
Capacitor bank transient currents, based on
ANSI/IEEE C37.012-1979
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28. Control house
 Located to minimize cable lengths
 Cable entry method basement or cable
trench.
 Grade higher so that water runs away.
 Provides weather proof and temperature
control for equipment.
 Control panels grouped by voltage level and
sized for future expansion.
 Block wall offers best design and cost.
 Location of Station Batteries
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29. Station Batteries
Batteries provide control power to switching and
substation components in times of an Ac power loss.
All critical control power comes from the DC System.
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30. Instruments and Meters
Current Transformer…An instrument
transformer intended to have its primary
winding connected in series with the
conductor carrying the current to be
measured or controlled
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31. Environmental Concerns
 Storm water runoff occurs when precipitation
from rain flows over the ground.
 Hard surfaces like driveways, sidewalks, and
streets prevent storm water runoff from
naturally soaking into the ground.
 All new construction shall have storm water
provisions so rain water settles into the
ground and does not flow out to the street.
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32. Substation Communications
Fiber optics is the communication backbone that
interconnects the substations for line relaying.
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33. Substation Automation
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34. Substation Security
NERC requires utilities to implement physical
security measures at their critical substations to
safeguard personnel and prevent unauthorized
access to critical assets and control systems.
 Physical security typically comprises five distinct
systems:
3. Delay/Deterrence
4. Detection
5. Assessment
6. Communication
7. Response
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35. Testing hits the mark
CommissioningYou
The End Thank Tests
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