1. 1. PURPOSE AND GENERAL CLASSIFICATION A substation is a high-voltage electric system facility. It is used to switch generators, equipment, and circuits or lines in and out of a system. It also is used to change AC voltages from one level to another, and/or change alternating current to direct current or direct current to alternating current. Some substations are small with little more than a transformer and associated switches. Others are very large with several transformers and dozens of switches and other equipment.
2. 2. SUBSTASTION can classified according to: Service Alternating current Alternating to direct current Mounting Indoor Outdoor
3. 3. Function Tap Distributing Industrial Sectionalizing Transmission-line supply Power- factor correction Frequency changer Railway, portable Direct current for light and power
4. 4. Type of apparatus Transformer Rotary converter Motor generator Frequency changer Synchronous condenser Power rectifier Control Manual Semiautomatic Automatic Supervisory
5. 5. High voltage (HV) ac: 69 kV, 115 kV, 138 kV, 161 kV, 230 kV Extra-high voltage (EHV) ac: 345 kV, 500 kV, 765 kV Ultra-high voltage (UHV) ac: 1100 kV, 1500 kV Direct-current high voltage (dc HV): 250 kV, 400 kV, 500 kV
6. 6. to be economical, transmission of large amounts of power over long distances must be done at voltages above 110,000 volts. Such substation between the 110- and 44-kv. Lines is known as a tap sub-station. -Equipment may comprise high and low tension switching equipment, transformers, and lightning arresters. A. TAP
7. 7. B. Distribution Any substation that is used to transform electrical energy to a potential that is low enough for general distribution and utilization is a distributing substation for local dist, 2 400 volts has been recognized as a standard voltage; Distribution at 6 600, 13 200 and 22 000 volts is used for longer distances and larger blocks of power.
8. 8. DISTRIBUTION SUBSTATION
9. 9. C. Industrial Large blocks of power are required by industrial plants, it often becomes necessary and advisable to install an individual substation to supply such a load direct from the main high-voltage line or secondary line of lower voltage. Equipment may comprise only switching equip, in most cases a voltage transformation is probably needed
10. 10. D. Sectionalizing In very long high-voltage large capacity lines, particularly when several circuits are run in parallel, it is often necessary to split the lines into sections, in order that proper protection to the line and service be obtained. Equipment comprise only switching equipment. In long lines it may also serve to supply power factor correcting equipment
11. 11. E. Transmission-line supply It is becoming more and more common to install the high-tension equipment of a power plant outdoors, the installation becoming nothing more than a step- up substation receiving its power at generator voltage, then stepping up its voltage and finally sending it out over high-voltage transmission lines.
12. 12. F. Power factor Correction Long transmission lines will reveal the fact that the voltage at the end of the line tends to increase as the load supplied is decreased, while on the other hand it tends to decrease as the load is increased. It is necessary to use synchronous condensers, so to control it power factor and voltage regulation may be had at the end of a long transmission line.
13. 13. Synchronous Condensers synchronous condenser is a synchronous machine running without mechanical load and supplying or absorbing reactive power to or from a power system. Also called a synchronous capacitor, synchronous compensator or rotating machinery.
14. 14. G. Frequency Changer To interconnect two systems of different frequencies it is absolutely necessary that the frequency changers be used. This type will necessitate transformers to step- down or step up the voltage supplied to or delivered from the frequency changer.
15. 15. H. Railway Substations supplying railways may be generally classified under two heads, namely, as Alternating current and Direct current Alternating current power can be more economically generated and controlled from the three phase units than single phase generators. Direct current is has been generally recognized that direct current is better suited to city railway service. the substation are generally supplied with 3-phase power and converted to direct current by means of rotary converters, motor generator sets, or power arc rectifiers.
16. 16. I. Direct Current for Light and Power There are still a few sections in some of our large cities which are supplied with direct current three wire systems. Such a supply is invariably obtained from synchronous converters. E.g.; certain types of motor loads in industrial plants, for electrolytic work, low voltage DC is absolutely essential.
17. 17. Outdoor Substation The necessary clearances b/w conductors and the space required for switches, circuit breakers, transformers, and other equipment become so great for voltages above 22 000 volts that it is generally more economical to install all such equipment outdoors.
18. 18. Indoor Substation Indoor Electrical Power Substation: In Indoor Substations is installed within the substation building. Such substations are usually for the rating of 22 kV below . Indoor Substations are preferred in heavily polluted areas and Power Substations situated near the seas (saline atmosphere causes Insulator Failures results in Flashovers)
19. 19. Indoor substation
20. 20. Transformer Power transformers raise or lower the voltage as needed to serve the transmission or distribution circuits.
21. 21. Potential transformers Potential transformers are required to provide accurate voltages for meters used for billing industrial customers or utility companies.
22. 22. Current transformers Current transformers can be used to supply information for measuring power flows and the electrical inputs for the operation of protective relays associated with the transmission and distribution circuits or for power transformers.
23. 23. These current transformers have the primary winding connected in series with the conductor carrying the current to be measured or controlled. The secondary winding is thus insulated from the high voltage and can then be connected to low-voltage metering circuits.
24. 24. Grounding Transformer A grounding transformer is intended primarily to provide a neutral point for grounding purposes. It may be provided with a delta winding in which resistors or reactors are connected.
25. 25. Rectifier A rectifier is a device used to convert alternating current to direct current.
26. 26. Rotary Converter A rotary converter is a type of electrical machine which acts as a mechanical rectifier or inverter. It was used to convert alternating current (AC) to direct current (DC), or DC to AC power, before the advent of chemical or solid state power rectification. They were commonly used to provide DC power for commercial, industrial and railway electrification from an AC power source.
27. 27. Frequency Changer A frequency changer is a motor-generator set that changes power of an alternating current system from one frequency to one or more different frequencies, with or without a change in the number of phases, or in voltage. Sometimes a converter is used to accomplish this.
28. 28. Lightning Arresters Lightning arresters are protective devices for limiting surge voltages due to lightning strikes or equipment faults or other events, to prevent damage to equipment and disruption of service. Also called surge arresters.
29. 29. A. Manual This type of control is applicable only to small- capacity substations. All the disconnecting switches, circuit breakers, and other equipment are manually controlled.
30. 30. B. Semi-automatic The majority of stations fall under this class. Control is obtained from a switchboard through mechanically or electrically remote methods, but all control is dependent upon the operator in charge at the substation.
31. 31. C. Automatic Full automatic substations have obtained a considerable favor for various purposed, particularly among railway engineers. Such substations are entirely unattended; they are started up automatically when a train comes into the range of the particular station and stopped when the train passed out of the range of the station.
32. 32. D. Supervisory In a many good cases it is desirable that the operation of a substation be under the direct control of an operator located at a considerable distance away. This can be accomplished by what us known supervisory control. By means of only three or four control wires running b/w the operator and the substation , it is possible to operate the substation very satisfactorily.