What is a substation? What is a substation?

Location for automatic protective devicesInterconnects transmission linesPermits switching of system equipment. Directs flow of power Detects and isolates faulted system

components.

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A properly planned and designed substation is essential for the reliable operation of the electric system.

Design ObjectivesDesign Objectives

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•Achieve reliability and flexibility

•Satisfy electric system requirements

•Minimizing investment costs

Needs DeterminationNeeds Determination

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The existing “Electric System” is analyzed to determine the need to build new or improve existing substation facilities.

Design Design ConsiderationsConsiderations

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Analysis ParalysisAnalysis Paralysis

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Through the planning process, system studies are conducted in order to properly design the substation.

CostsCosts

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Substations are capital-intensive construction projects that require long term strategic planning.

BudgetingBudgeting

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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Basic single line designBasic single line design

Develop a single line of the station and bus configuration.

General concept of substationPhysical layout and location of major

equipment and steel structuresEquipment and materials specifications Electrical and safety clearances based on

IEEE standards

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IEEE 1427 Guide for Recommended Electrical Clearances and Insulation Levels in Air Insulated Electrical Power Substations.

Bus Configurations Bus Configurations

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Physical layoutPhysical 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

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Substation FootprintSubstation Footprint

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

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IEEE 1427™, “Guide for Recommended Electrical Clearances and Insulation Levels in Air Insulated Electrical Power Substations.

Basic Impulse Level (BIL)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 230kV = 900 BIL 04/12/23

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Component SpacingComponent Spacing

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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

Structure LoadsStructure LoadsDesigned for mechanical and electrical forces.Seismic loadsDead loads

Line support, switches, insulators, phase wires, potential transformers

Wind loadsOperating loadsShort circuit forces

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FoundationsFoundations

Foundations transmit loads from structures and equipment to soils

Many soil types require different designs.Identify geotechnical information requiredSoil boring plan and specificationsLab testingGeotechnical reportConcrete design

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Essential Ground Design ElementsEssential Ground Design Elements

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

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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.

IEEE 80-2000 Guide for Safety in AC Substation Grounding

Step and TouchStep and TouchPrimary 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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Protective RelayingProtective 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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Protection ZonesProtection 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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Surge protectionSurge protection

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.

1. Evaluate significance of facility being protected.2. Evaluate geographical thunderstorm exposure.3. Design suitable system of protection. 4. Evaluate the cost and effectiveness of the design.

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IEEE Std. 998-1996, Guide for Direct Stroke Shielding

Seismic ThoughtsSeismic Thoughts

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.

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IEEE Std 693 - 2005 IEEE Recommended Practice for Seismic Design for Substations

Material & Equipment Material & Equipment SpecificationsSpecifications

IEEEA 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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TransformersTransformers

Oil cooling230-69kV Wye-Delta Connection +/- 30 degrees69-12kV Delta-Wye Connection +/- 30 degrees

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IEEE C57.12.36, Standard Requirements for Liquid-Immersed Distribution Substation Transformers

Air insulated Circuit breakersAir 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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Gas insulated Switchgear “GIS”Gas insulated Switchgear “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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C37.123-1991 IEEE guide to specifications for GIS

Disconnect SwitchesDisconnect Switches

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Non-load breaking device designed to open and close an electric circuit.

Isolate major equipment from the electric system and provide a visible open.

Capacitor BanksCapacitor Banks

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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

Control houseControl houseLocated to minimize cable lengthsCable 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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Station BatteriesStation BatteriesBatteries provide control power to switching andsubstation components in times of an Ac power loss.

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All critical control power comes from the DC System.

Instruments and MetersInstruments and Meters

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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

Environmental ConcernsEnvironmental 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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Substation CommunicationsSubstation Communications

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Fiber optics is the communication backbone that interconnects the substations for line relaying.

Substation AutomationSubstation Automation

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Substation SecuritySubstation SecurityNERC 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:

1. Delay/Deterrence 2. Detection3. Assessment4. Communication5. Response

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Testing hits the mark

The End Thank YouCommissioning TestsCommissioning Tests04/12/23

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