SUBSTATION LAYOUT AND ACCESSORIES
& BUSBAR ARRANGEMENT Part A : SUBSTATION LAYOUT Single line diagram
CONTENTS Part A : SUBSTATION LAYOUT Single line diagram Substation Switchyard Accessories Lightning Arrestor CVT Earthing switch Wave trap Isolator Current transformer Circuit Breaker Power Transformer Reactors and capacitors Other Switchyard Equipments PART B: BUSBAR ARRANGEMENT
PLCC SCADA PART B: BUSBAR ARRANGEMENT Single bus system Single bus system with bus sectionalizer Double bus system Double breaker bus system One and a half breaker bus system Main and transfer bus system Double bus system with bypass isolator Ring main bus system PART- A SWITCHYARD LAYOUTING CLASSIFICATION OF SUBSTATIONS
Based on working Generating substation (step up s/s) Grid substation Switching substation Secondary substation a) sub transmission voltage b) primary distribution c) distribution substation Based on structure Outdoor conventional air insulated substation (AIS) Indoor substation Compressed air insulated G I S SINGLE LINE DIAGRAM LIGHTNING ARRESTOR Alightning arresteris a device used on electricalpower systemsto protect theinsulationon the system from the damaging effect oflightning. Metal oxide varistors (MOVs) have been used for power system protection since the mid 1970s. The typical lightning arrester also known assurge arrester has a high voltage terminal and a ground terminal. Current from the surge is diverted around the protected insulation in most cases to earth. PICTURES OFSURGE DIVERTER (LIGHTNING ARRESTOR) CVT Capacitor Voltage Transformer(CVT), CapacitanceCoupled Voltage Transformer(CCVT) To step downextra high voltage signals and provide alow voltage . For measurement or to operate aprotective relay. EARTHING SWITCH Earth Switch is used to discharge the voltageon the circuit to the earth for safety. Earth switch is mounted on the frame of the isolators. It is located for each incomer transmission line and each side of the busbar section. Connected in series with the power (transmission) line.
LINE TRAP (WAVE TRAP) Connected in series with the power (transmission) line. It blocks the high frequency carrier waves (24KHz to 500KHz) and letpower waves (50 Hz - 60 Hz) to pass through. It is basically an inductor of rating in Milli henry (approx 1 milli Henry for 220 KV 1250 Amp.). It has three main components:- 1. Main coil. 2. Tuning Device. 3.Lightning Arrestor. ISOLATOR Disconnector orIsolator switchis used to make sure that an electrical circuit can be completely de-energised for service or maintenance. Isolator is anoff-loaddevice. Types of Isolators are 1. Central rotating, horizontal swing 2. Centre-Break 3. Vertical swing 4. Pantograph type CURRENT TRANSFORMER Current transformers are used for Stepping down current for measurement, protection and control. Current transformers are of two types 1. Protective CT 2. Measuring CT CIRCUITBREAKERS ACircuit breakeris an automatically operatedelectrical switchdesigned to protectanelectrical circuitfrom damage caused byoverloadorshort circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinueelectrical flow. All circuit breakers have common features in their operation, although details vary substantially depending on the voltage class, current rating and type of the circuit breaker. Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit. Small circuit breakers may be manually operated; larger units havesolenoids to trip the mechanism, and electric motors to restore energy to the springs. Different techniques are used to extinguish the arc
: Lengthening / deflection of the arc : Intensive cooling (in jet chambers) : Division into partial arcs : Zero point quenching : Connectingcapacitorsin parallel with contacts in DC circuits High-voltage breakers are broadly classified by the medium used to extinguish the arc Bulk oil Minimum oil Air blast Vacuum SF6 BUSBAR Busbars receive power from incoming circuits and deliver power to outgoing circuits. POWER TRANSFORMERS Power Transformers are used to step up or step down a.c. voltages and to transfer electrical power from one voltage level to another. SHUNT REACTORS Shunt Reactors are used for long EHV transmission lines to control voltage during low load period. Shunt reactors is also used to compensate shunt capacitance of transmission line during low load periods. Usually Shunt reactors are unswitched. SEREIS REACTORS Series reactors are used to limit short circuit current and to limit current surges associated with fluctuating loads. Series reactors are located at the strategic locations such that the fault levels are reduced. SHUNT CAPACITORS Shunt capacitors are used for compensating reactive power of LPF. They are used for improving the power factor. It is also used for voltage control during heavy lagging power factor loads. Theyare located at the receiving stations and distribution substations. They are switched on during heavy loads and switched off during low loads. SERIES CAPACITOR Series Capacitors are used for some long EHV a.c. lines to improve power transferability. They located at the sending end / receiving end of the lines. Theyare provided with by pass circuit breaker and protective spark gaps. NEUTRAL GROUNDING EQUIPMENT
Neutral Grounding Equipment are Resistors and reactors. They are used to limit the short circuit current during ground fault. They are connected between neutral point and ground. OTHER SWITCHYARD EQUIPMENTS
. MARSHALLING KIOSKS . STATION EARTHING SYSTEM . POWER CABLES . CONTROL CABLES . INSULATORS . METERING, RELAY AND CONTROL PANEL . SUPPLY SYSTEM POWER LINE CARRIER COMMUNICATION
PLCC is mainly used for telecommunication, tele-protection and tele-monitoring between electrical substations through power lines at high voltages, such as 110 kv, 220 kv, 400 kv. The voice signal is converted/compressed into the 300 Hz to 4000 Hz range. It is known as: Power line Digital Subscriber Line (PDSL) mains communication power line telecom (PLT) power line networking (PLN) Broadband over Power Lines (BPL) WHAT IS SCADA ? SCADA stands for Supervisory Control And Data Acquisition. It is not a full control system, but rather focuses on the supervisory level. It is a purely software package that is positioned on top of hardware to which it is interfaced. ( via Programmable Logic Controllers(PLCs)) . The SCADA systems are arranged to perform the following tasks.
Data Collection (Data Acquisition) Data transmission (telemetry) Scanning, Indication, Monitoring, Logging. Control and indication. Ensure sequential events. Data presentation, display, reporting Execution of operating, commands: on/off,raise/lower. Network supervision, alarms and report any uncommon change of state. PART B BUS BAR ARRANGEMENT CONDUCTOR USED FOR BUSES
All Aluminum conductor (AAC) All Aluminum alloy conductor (AAAC) Aluminum conductor with aluminum alloy reinforced (ACAR) Aluminum conductor with steel reinforced (ACSR) SINGLE BUS SYATEM Advantages: 1.Simple in Design 2.Less Expenditure
Disadvantages: 1.In case of bus fault or bus bar isolator fault or maintenance total Substation is out of service. 2.In case of maintenance of transformer circuit breaker the associated transformer has also to be shut-down. Similarly for Line also. SINGLE BUS WITH BUS SECTIONALISER
Advantages: 1. One complete section can be taken out for Maintenance without disturbing the continuity of other section. 2. If a fault occurs on one section of the Bus, that faulty section alone will be isolated. Disadvantages: It will be a little more costly with the addition of one isolator and some cases with Circuit breaker, C.Ts and C&R panel. DOUBLE BUS SYSTEM Advantages:
: Double Bus Bar Arrangement increases the flexibility of system. Disadvantages: :The arrangement does not permit breaker maintenance with out interruption. DOUBLE BREAKER BUS SYSTEM
Advantages: There is no need of bus coupler as because the operation is done by breakers instead of isolator Disadvantages: Most expensive as it involves additional breaker, CTIsolators etc for each circuit. ONE AND A HALF BREAKER BUS SYSTEM
Advantages: During any fault on any one of the buses, that faulty bus will be cleared instantly without interrupting any feeders in the system since all feeders will continue to feed from other healthy bus. Disadvantages: This scheme is much expensive due to investment for third breaker. MAIN AND TRANSFER BUS SYSTEM
Switching operation: 1.First close the isolators at both side of the bus coupler breaker. 2. Then close the bypass isolator of the feeder which is to be transferred to transfer bus. 3. Now energized the transfer bus by closing the bus coupler circuit breaker from remote. 4.After bus coupler breaker is closed, now the power from main bus flows to the feeder line through its main breaker as well as bus coupler breaker viatransfer bus. 5. Now if main breaker of the feeder is switched off, total power flow will instantaneously shift to the bus coupler breaker and hence this breaker will serve the purpose of protection for the feeder. 6. At last the operating personnel open the isolators at both sides of the main circuit breaker to make it isolated from rest of the live system. DOUBLE BUS SYSTEM WITH BYPASS ISOLATOR
Advantages: It permits breaker maintenance without interruption of power which is not possible in double bus system but it provides all the advantages of double bus system. Disadvantages: It however requires one additional isolator (bypass isolator) for each feeder circuit and introduces slight complication in system layout. RING BUS SYSTEM Advantages:
It provides a double feed to each feeder circuit, opening one breaker under maintenance or otherwise does not affect supply to any feeder. But this system has two major disadvantages. Flexibility for breaker maintenance Each breaker removable without disconnecting load Only one breaker needed per branch, Each branch connected to network by two breakers All change-over switching done with circuit-breakers & hence flexible. THANK YOU