Presentation on theme: "PRESENTATION ON SUBSTATION DESIGN"— Presentation transcript:
1 PRESENTATION ON SUBSTATION DESIGN FRANCIS ARTHUR
2 Substation There are four major types of electric substations: Switchyard at a generating station:These facilities connect the generators to the utility grid and also provide off-site power to the plant.Customer Substation:Functions as the main source of electric power supply for one (or more) business customers. The technical requirements and the business case for this type of facility depend highly on the customer’s requirements.
3 Substation Switching Substation: Facilitate the transfer of bulk power across the network. Their feeders typically originate from generating switchyards. They enable the transmission of large blocks of energy from the generators to the load centers.Distribution Substation:Provide the distribution circuits that directly supply most electric customers.
5 Substation Design Challenge Optimal technical performance at least cost.Design ConsiderationsLow life cycle costSafetyStandardization (Equipment and Station Configurations)
6 Substation Configurations Single BusAll elements (transformers and transmission lines) are directly connected to one busAdvantagesCost of construction is relatively lowDisadvantagesReliability is lowLow Operational Flexibility (E.g Outage required on associated element for maintenance of switchgear)Suitable Where:Load & Availability requirements are low
7 Substation Configurations Typical Single Line DiagramTypical Layout
8 Substation Configurations Main and Transfer BusAll elements (transformers and transmission lines) are directly connected to Main busAdvantagesCost of construction is relatively lowOperational Flexibility Higher than single bus scheme due to Transfer Bus and Tie Breaker (Outage is not required on associated element for maintenance of switchgear)DisadvantagesReliability is lowSuitable Where:Load & Availability requirements are low
9 Substation Configurations Typical Single Line DiagramTypical Layout
10 Substation Configurations Double Bus Single BreakerConnects each circuit to two buses, and there is a tie breaker between the buses.AdvantagesCost of construction is relatively lowReliability Higher than Main & Transfer bus scheme (Bus fault limited to affected bus due to availability of tie breaker)DisadvantagesLow Operational Flexibility (E.g Outage required on associated element for maintenance of switchgear)Suitable Where: Load Transfer & Improved Operating Reliability are Important
12 Substation Configurations Double Bus Double Breaker SchemeInvolves two breakers and two buses for each elementAdvantagesIncreased reliability (Bus fault does not affect any element)Increased Operational Flexibility (E.g No outage required for maintenance of circuit breakers)DisadvantagesCost of construction is relatively highSuitable Where: reliability and availability of the circuit is a high priority.
13 Substation Configurations Typical Single Line Diagram
14 Substation Configurations Ring BusAll breakers are arranged in a ring with elements connected between two breakers.AdvantagesIncreased reliability (Bus fault limited to affected section & faults to individual elements do not affect others)Increased Operational Flexibility (E.g No outage required on associated element for maintenance of switchgear)DisadvantagesCost of construction is relatively highSuitable Where: reliability and availability of the circuit is a high priority.
15 Substation Configurations Typical Single Line DiagramTypical Layout
16 Substation Configurations Breaker and a Half Bus SchemeConfigured with a circuit between two breakers in a three-breaker line-up with two busesAdvantagesIncreased reliability (Bus fault does not affect any element)Increased Operational Flexibility (E.g No outage required for maintenance of circuit breakers)DisadvantagesCost of construction is relatively high but justifiable due to above advantagesSuitable Where: reliability and availability of the circuit is a high priority.
17 Substation Configurations Typical Single Line DiagramTypical Layout
18 Substation Equipment Categories of Equipment: Switchgear Power TransformersCapacitor Banks & SVCInstrument TransformersProtection and Control EquipmentAuxiliariesSCADA and Communication
19 Switchgear Disconnector Switch with Earthing Blade Disconnector Switch Without Earthing Blade
20 Disconnect SwitchMechanical device that conducts electrical current and provides an open point in a circuit for isolation.Disconnect switches are also installed to by pass breakers or other equipment for maintenance.They are designed for no-load switching.Key RequirementsOpen and Close reliably whenever necessaryCarry current continuously without overheatingTo remain in the closed position under fault current conditions
22 Circuit BreakerA mechanical switching device capable of making , carrying , and breaking currents under normal circuit conditions and also breaking currents under specified abnormal conditions such as a short circuit.
23 Surge ArrestersDevices deployed to protect power system equipment from being subjected to lightning or switching surges.
24 Power TransformerA transformer is an electrical device for converting ac power at a certain voltage level into ac power at a different voltage, but at the same frequency.Inductively couples load to the power system at different voltages.
25 Capacitor BanksDeployed for local reactive power compensation at the load.Required for voltage support and reduction of transmission losses.
26 Static Var Compensators (SVC) Deployed for dynamic local reactive power compensation at the load.Required for voltage support and reduction of transmission losses.Relies on power electronic and other static controllers to enhance control and increase power transfer capability.
27 Instrument Transformers Current TransformerVoltage Transformer
28 Instrument Transformers A high precision transformer designed to:Provide input into measurement and/or control equipment.Examples: Voltmeters Ammeters Watthour Meters, Relays.Transform currents or voltages from a usually high value to a value easy to handle by protective relays and instruments.
30 Protection & Control Equipment Dedicated Protection panels for transmission lines, power transformers or capacitor banks.Protection Equipment ensure speedy isolation of equipment in the event of fault by initiating commands to circuit breakers based on set current or voltage limits.Control Equipment facilitate the control of switchgear either from the control room or at the switchyard.
31 Substation Auxiliaries Substation auxiliaries encompass all systems that make the operating voltages of 415Vac, 125Vdc and 48Vdc available at the substation. It includes the following:Auxiliary Transformers (usually 34.5/0.415kV, 100 (or 250kVA)Diesel generator setsSolar Power Systems125Vdc Rectifiers & 125Vdc Battery Banks48Vdc Rectifiers & 48Vdc Battery BanksAutomatic Change over switchesAC & DC Distribution Boards
34 Substation Auxiliaries 48Vdc RectifierChange Over Panel
35 RectifierA rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. (Source: Wikipedia)
36 Substation Auxiliaries AC Distribution PanelDC Distribution Panel
38 SCADA & CommunicationPLC is the superimposition of various signals (ie. data, voice, Fax etc.) on the power line at different frequencies thus relying on the power line as the carrier of the signals.Functions:Provides means of high speed fault clearing through use of communication schemes to confirm faulted line section.Aids in implementation of breaker failure schemesAids in remote control requirementsGoal:To transmit a signal of high quality to the receiving end such that the receiver can interpret the signal.
39 SCADA & Communication Transmitters & Receivers The carrier transmitters and receivers are usually mounted in a rack or cabinet in the communication room. (Egs. ETL & FOX panels).
40 SCADA & Communication Line Tuners Works in conjunction with the coupling capacitor to provide a low impedance path for the carrier energy to the transmission line and a high impedance path to the power frequency energy.
41 SCADA & Communication Line Traps Directs the carrier signal off the substation bus towards the remote line terminal.Presents a high impedance path for the carrier energy towards the bus thus directing onto the remote line terminal.The coil of the line trap presents a low impedance path to the power frequency.
42 SCADA & Communication RTU A remote terminal unit (RTU) is a microprocessor-controlled electronic device that interfaces objects in the physical world to a distributed control system or SCADA (supervisory control and data acquisition) system by transmitting telemetry data to a master system, and by using messages from the master supervisory system to control connected objects. (Source: Wikipedia)
44 Substation GroundingSubstation grounding is a means of channeling excessive fault currents to ground with the view to preventing damage to equipment and protecting personnel from being subjected to unsafe potentials.It is achieved with a mat made up of horizontal interconnected bare conductors and ground rods to which all equipment structures are bonded.The grounding system includes all of the interconnected grounding facilities in the substation area, including the ground grid, overhead ground wires, neutral conductors, underground cables, iron rods in foundations etc.
45 Substation Grounding Reasons for Grounding It provides a means of dissipating electric current into the earth without exceeding the operating limits of the equipment.It provides a safe environment to protect personnel in the vicinity of grounded facilities from the dangers of electric shock under fault conditions.
46 Substation Grounding Circumstances for Human Electric Shock Relatively high fault current to ground in relation to the area of the grounding system and its resistance to remote earth.Soil resistivity and distribution of ground currents such that high potential gradients may occur at points at the earth surface.Presence of a person at such a point, time, and position that the body is bridging two points of high potential difference.Absence of sufficient contact resistance or other series resistance to limit current through the body to a safe value under the above circumstances.Duration of the fault and body contact and, hence, of the flow of current through a human body for a sufficient time to cause harm at the given current intensity.
47 Substation Grounding The Design Problem? To provide a safe condition for personnel within and around the substation area by limiting voltages to safe values.To provide an adequate earthing system at minimum cost.
50 Insulation Coordination Over voltages introduce stress to the power system insulation.Insulation coordination is a combination of measures to prevent the breakdown of insulation.It is a means of achieving technically acceptable level of insulation that is matched to the level of surge protection.It comprises the following systems:Electrical ClearancesInsulation Levels
54 Insulation Coordination AdvantagesReliable operation of high voltage systemsMinimized equipment damageReduced outagesReduced Operational Losses
55 Lightning Protection Effects of Lightning in Electrical Installations Introduces over voltages and damage to non-restoring (solid) insulationExtreme local heating (vaporization of material, explosion)Direct strikes generate fields and large mechanical forcesGenerates electromagnetic (EMI) and radio frequency interference (RFI) which disturb telecommunication equipment and low voltage digital (and analogue) signal equipment.