basic substation training

Basic Substation Training

By Kelvin Tang4 June 2009

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•Basic substations•Why do we need them?•Different configurations•Availability•Design parameters•Function of main components•Cost drivers

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What is a Substation?

SUBSTATION - A facility that steps up or steps down the voltage in utility power lines. Voltage is stepped up where power is sent through long-distance transmission lines. It is stepped down where the power is to enter local distribution lines. - California Energy Commission Dictionary

An electricity substation is a place, which allows electricity to go from one part of the production system to another. -Cambridge International Dictionary

Subsidiary station in which electric current is transformed. -Merriam Webster’s Dictionary

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What is a Substation?Outdoor Substation is an open type of structure for supporting high-voltage air-insulated power equipment. – NEMA SG 6

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Why do we need a substation?Substations are entities that integrate the power system (Generation, Transmission, and Distribution).

They provide:-Transformation-Switching-Tie Points-Sectionalizing-Protection-Compensation

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Design Objective:

The substation design objective is to provide maximum reliability, flexibility, and continuity of service and to meet these objectives with the lowest investment costs that satisfy system requirements. – Standard Handbook for Electrical Engineers

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Design Considerations:

•Voltage Level•Load Capacity•Environmental Considerations•Site Space Limitations•Transmission Line right-of-way Requirements•Safety•Maintenance and Operation•Expandability•Cost•Reliability

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Types of Substations:

•AIS – Air Insulated Substation•GIS – Gas Insulated Substation•Hybrid – SF6 and Air•Modular Substation•Standard Substation•Mobile Substation•Distribution Substation (34-138 kV HV; 2.4-34.5 kV LV side)•Transmission Substation (230-745 kV HV; 34-230 kV LV side)•Switching Substation (Transmission SS without transformer)

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AISAdvantages Disadvantages

Easy access to bus and equipment for inspection and repair

Equipment are subject to weather conditions, animals, vandalism, contamination

Lower cost Requires more real estateDesign and material flexibilityEasy to expandEasy to replace equipment

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Basic Substation TrainingTypes of Substations:

AIS

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GISAdvantages Disadvantages

Reduced space requirements Higher costLess exposure to contamination Requires clean work area for assemblyHV Bus physically protected Expensive repairFlexible layout and Expansion Requires special training for operatorsNo concern about clearances to ground Spare parts are specializedCan be installed indoors

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Basic Substation TrainingTypes of Substations:

GIS

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Configurations of Substations:

•Single Bus•Segmented Single Bus (Single Bus with Sectionalizer)•Main and Transfer Bus•Double Bus, Single Breaker•Double Bus, Double Breaker•Ring Bus•Breaker and a Half

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Configurations of Substations:Single Bus

Advantages DisadvantagesLeast cost Bus fault causes a complete substation

outageExpandable Minimal flexibility for maintenanceSimple protection scheme Expansion requires complete outageSimple operationLess real estate requirements

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Configurations of Substations:Segmented Single Bus

Advantages DisadvantagesIncreased reliability Higher cost (more breaker / switches /

relaying)More operational flexibility (fault on the bus will de-energize only half of the SS)

More equipment to maintain

Maintenance can be done in one bus while the other is energized.

Outage can occur on several lines of the same bus

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MAIN AND TRANSFER BUS

Increased relaying complexity

Main and Transfer BusAdvantages Disadvantages

Circuit breaker can be readily removed from service for maintenance

Extra circuit breaker

Relatively low cost for increased flexibility Requires a switching procedure for transferring a line to another breaker

Failure on the main bus may cause a complete outage of the substation

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Complicated switch operationEach circuit can be connected to either busComplicated relaying

Tie breaker fault causes outage on the entire substation

Each bus can be isolated for maintenance

Double Bus, Single BreakerAdvantages Disadvantages

One breaker per line Extra breaker for couplingProvide more flexibility Bus fault or breaker failure will disconnect

all circuit connected to this bus

Requires additional switches

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Possibility of losing half of the substationHigh availability and reliability

Double Bus, Double BreakerAdvantages Disadvantages

Each breaker can be serviced without disconnecting the circuit

Two breaker per circuit

Either bus can be serviced without interruption of power

Highest cost

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RING BUS

Difficult expansionNo main bus

Requires a potential transformer in each circuit

One breaker per circuit

During fault only two breaker are trippedDuring breaker failure three breaker are trippedAll switches is done with breakers

Ring BusAdvantages Disadvantages

Low cost Fault during a breaker maintenance causes a ring separation

Each breaker can be maintenance without outages

Automatic reclosing and protective relaying rather complex

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Either bus can be taken out of service

Bus failure causes no outage

Complex reclosing and protection schemesBus breaker failure removes only one circuit

All switching done with breakersSimple operation

High availability

Breaker and a halfAdvantages Disadvantages

Most flexible operation High costHigh reliability More breakers

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Availability of a Substation:

AVAILABILITY. Describes the reliability of power plants. It refers to the number of hours the Turbines are available to produce power divided by the total hours in a year. - The Sun's JoulesIs the percent of the time that a unit is available to produce power whether needed by the system or not. It is a measure of overall unit reliability. It is equal to 100% less percentage oftime of forced outage less percentage of time on scheduled outage. – Standard Handbook for Electrical Engineers

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Reliability of a Substation:

Reliability Engineering. The probability that a product will be operational after a period of usage or over a specified time period, based on testing of the product under a prescribed operation and operating environment – Harcourt Dictionary

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Reliability of a Substation:

RELIABILITY - Electric system reliability has two components: adequacy and security. Adequacy is the ability of the electric system to supply the aggregate electrical demand and energy requirements of the customers at all times, taking into account scheduled and unscheduled outages of system facilities. Security is the ability of the electric system to withstand sudden disturbances such as electric short circuits or unanticipated loss of system facilities. Energy Terms Dictionary

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Reliability of a Substation:System reliability consists of two elements: dependability and security. Dependability is the certainty of correct operation in response to system trouble, whereas security is the ability of the system to avoid misoperation with or without faults. Dependability can be checked relatively easily in the laboratory or during installation by simulated tests or a staged fault. Security, on the other hand, is much more difficult to check. A true test of system security would have to measure response to an almost infinite variety of potential transients and counterfeit trouble indications in the power system and its environment. A secure system is usually the result of a good background in design, combined with extensive model power system and can only be confirmed in the power system itself and its environment. – ABB Protective Relaying Theory and Applications

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Basic Substation TrainingWhy High Voltage Product?

-High voltage products perform different important functions in the power system.-Connect, Detect, Protect and Correct:-connect the various parts in a substation.-Detecting & monitor the operating levels of current and voltage for accurate energy measurement.-protect the power system.-correct the voltage and power factor.

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Basic Substation TrainingComponents of a Substation:

Circuit breakers: Protects and isolates the power system from faulted lines and equipment. Has the ability of operate under load

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Disconnect Switches: Provides a visual means of isolating a circuit. Usually operated without load

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Grounding Switches: Provides a path from phase to ground

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Current Transformers: Device used for measuring the primary current of the system

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Components of a Substation:

Potential Transformers: Device used for measuring the primary voltage of the system

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Coupling Capacitors Voltage Transformer: Device used for measuring the primary voltage and sometimes also in conjunction with the Line Trap for telecommunication applications

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Line Traps: Used in Power Line Carrier application for telecommunication between substations

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Lightning Arresters and/or gaps: Device that provides a controlled point for diverting a surge or overvoltage, thereby protecting equipment

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Power Transformers: Provides transformation of electric power from one voltage level to another at constant power

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Shunt reactors: Used on long transmission line systems to limit the voltage during breaker operation

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Current-limiting Reactors: Used to limit the short circuit level of a sub-transmission system

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Station buses and insulators: Used to route the electrical energy within the SS

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Grounding System: Protects people and electrical equipment during normal or fault situation, and provides a solid voltage reference point

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Series Capacitors: Used in EHV systems to increase power flow capacity and system stability

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Shunt Capacitors: Used for compensating a reactive load and for regulating the voltage

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Auxiliary Power System: Provides the electricity needed to insure the proper operation of the substation. (Ex.: Auxiliary Transformer, Load Center, Motor Control Center, AC Distribution Panel, DC Distribution Panel, Battery Bank, Battery Charger, etc.)

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Control and Protection System: Provides means to electrically operate the equipment of a substation from a remote location and also protects the HV equipment in the event of a fault. (Ex.: Protection Relays, Control Panel, Control Panel Accessories e.g., control switches, test switches, indicating lights, etc.)

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Design Parameters:

Voltage:

(V) Term used to designate electrical pressure or force that causes current to flow. – Dictionary of Electronics

VOLTAGE. The difference in electrical potential between any two Conductors or between a conductor and ground. It is a measure of the electric energy per electron that electrons can acquire and/or give up as they move between the two conductors. – The Sun’s Joule

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Design Parameters:

Current:

Current - The flow of electrons through a complete circuit. –Smart.com

Measured in amperes, it is the flow of electrons through a conductor. Also know as electron flow. – Dictionary of Electronics

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Design Parameters: Power:Amount of energy converted by a circuit or component in a unit of time, normally seconds. Measured in units of watts. (joules/second). – Dictionary of electronics

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Design Parameters: Power:POWER The rate at which energy is consumed or produced. It is expressed in Watts (W). A 1-watt source supplies energy at the rate of 1 Joule per second. (A 100-watt lamp consumes energy at the rate of 100 joules per second; the human body involved in normal activity is rated at about 100W, a significant proportion being used to drive the brain). The Sun radiates energy at the rate of about 70 million watts per square meter ofits surface; at the equator the Earth receives a mean annual solar energy flux of around 1,400 watts per square meter. - The Sun’s Joule

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Civil Design Parameters: Codes:UBC – Uniform Building CodeSBC – Standard Building CodeBOCA – Building Officials Code AdministratorsIBC – International Building CodeASCE – American Society of Civil EngineersNESC – National Electrical Safety CodeNEMA SG6 – National Electrical Manufacturer AssociationIEEE – International Electrical and Electronic Engineers Code

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Civil Design Parameters: Seismic Zone:Can be measured on:Zone 1, Zone 2, Zone 3, Zone 40.1G, 0.2G, 0.3G m/s2

From the “No Seismic” to the “Max Seismic” Zone there may be up to 50% (Breakers and Transformers) difference in the foundation and structural design

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Civil Design Parameters: Wind:Old Code: 70-150 mph New Code: 90-180 mph

Wind Load = 0.0256 x V2 x factor x S

It is the biggest load in a substation structure (except for breakers and transformers)

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Civil Design Parameters: Ice:Varies from 0”-1.5”

This load can double the normal weight of Conductors and Rigid Buses

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Civil Design Parameters: Soil Properties:Soil can vary from a swamp to rocky.

The volume of the foundations can vary up to 100% and the cost up to 200% due to these properties

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Civil Design Parameters: Water Table:Water must be pumped out of the foundation before pouring concrete on it

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A substation may cost from < 1 million dollars up to tens of millions

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Acknowledgements:

For the support and information sharing, thanks to:

• Juliano Braz• Sylvester Phang• Wong Weng Woi• Sankaran-T Arasu

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Bibliography:1. G. Balzer, B. Boehle, K. Haneke, H. G. Kaiser, R. Pohlmann, W.

Tettenborn, G. Voss, ABB Switchgear Manual, Tenth Edition

2. W. A. Elmore, ABB Protective Relaying Theory and Applications

3. D. Fink, H. Beaty, Standard Handbook for Electrical Engineers, Thirteenth Edition, McGraw Hill, 1993

4. ABB Power Technologies, High 5, http://www49.de.abb.com/

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basic substation training

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