First things first. Planning for the future Initially, the following conditions of the existing electric system are analyzed to determine the need to build new or improve existing substation facilities.
Dependant on the real estate available. Location of the facility. For example, down town redevelopment may require a certain look. Politicians and upper management may not want to see and exposed conductors. This drives cost and substation design.
To minimize the effects of these surges, electrical system is protected by lighting arresters but they do not completely eliminate the surge.
Requires design and analysis of step and touch potentials.
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.
Several large earthquakes causing millions of dollars in damage prompted IEEE standard 693 Seismic Design for Substations which represents a major change in requirements.
Have to have a good strong document
Circuit breakers are generally located so that each generator, transformer, bus, transmission line, etc., can be completely disconnected from the rest of the system. Circuit Breakers must have sufficient capacity so that they can carry momentarily the maximum short-circuit current that can flow through them, and then interrupt this current; they must also withstand closing in on such a short circuit and then interrupting it according to certain prescribed standards
When two or more capacitor banks are in parallel on a common bus, the back-to-back switching of a bank against one or more already energized banks can produce high peak transient in-rush current values. Typically, these currents can exceed the available fault current levels previously present at the bus. The relatively high level and short duration of these currents can damage substation and control equipment necessitating that appropriate precautions be taken during the design process. Care must be taken to estimate capacitor bank transient currents, based on ANSI/IEEE C37.012-1979
Dominant technology is vented lead acid. Poor performance of (VRLA) in the 80’s and 90’s. New technologies such as lithium ion and ultra capacitors may be the way of the future.
These CT’s have a high failure rate. Are in a very bad spot if they fail. Not IEEE 693 compliant
An electric substation automation system is an interface between the substation and its associated equipment to provide and maintain operations and control. Utilities face a increasing pressure for greater system reliability and customer satisfaction. Substation Automation ensures power system stability, fast load restoration, advanced fault notification and fault analysis. Intelligent Electronic Devices (IEDs) are a part of the substation automation system. IED is a generic name that covers protection, control, metering and monitoring devices that use microprocessor-based technology. IEDs may resemble the traditional meter or protective relay, but are significantly enhanced and cannot be easily compared to earlier technologies.
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. 1 03/27/12
Design Objectives•Achieve reliability andflexibility•Satisfy electric systemrequirements•Minimizing investmentcosts 2 03/27/12
Needs DeterminationThe existing “Electric System” is analyzed todetermine the need to build new or improve existingsubstation facilities. 3 03/27/12
Analysis Paralysis Through the planning process, system studies are conducted in order to properly design the substation. 5 03/27/12
Costs Substations are capital-intensive construction projects that require long term strategic planning. 6 03/27/12
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 7 03/27/12
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 standardsIEEE 1427 Guide for Recommended Electrical Clearances and Insulation Levelsin Air Insulated Electrical Power Substations. 8 03/27/12
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 03/27/12
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 03/27/12
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 12 230kV = 900 BIL 03/27/12
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 13 03/27/12
Structure LoadsDesigned for mechanical and electrical forces.Seismic loadsDead loads Line support, switches, insulators, phase wires, potential transformersWind loadsOperating loadsShort circuit forces 14 03/27/12
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 15 03/27/12
Essential Ground Design Elements IEEE 80-2000 Guide for Safety in AC Substation Grounding1. 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 03/27/12
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 17 03/27/12
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 18 03/27/12
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. 19 03/27/12
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. 20 03/27/12
Seismic ThoughtsIEEE 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 03/27/12
Material & EquipmentSpecifications IEEE A document that specifies, in a complete, precise, and verifiable manner, the requirements, design , behavior, or other characteristics of a system component. 22 03/27/12
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 24 03/27/12
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. 25 03/27/12
Disconnect SwitchesIsolate major equipment from the electricsystem and provide a visible open.Non-load breaking device designed to open andclose an electric circuit. 26 03/27/12
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 27 03/27/12
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 28 03/27/12
Station BatteriesBatteries provide control power to switching andsubstation components in times of an Ac power loss.All critical control power comes from the DC System. 29 03/27/12
Instruments and MetersCurrent Transformer…An instrumenttransformer intended to have its primarywinding connected in series with theconductor carrying the current to bemeasured or controlled 30 03/27/12
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. 31 03/27/12
Substation Communications Fiber optics is the communication backbone that interconnects the substations for line relaying. 32 03/27/12
Substation 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:3. Delay/Deterrence4. Detection5. Assessment6. Communication7. Response 34 03/27/12
Testing hits the mark CommissioningYou The End Thank Tests 35 03/27/12
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