24-07-2014, 03:04 PM
RAJASTHAN RAJYA VIDHYUT PRASARAN NIGAM LIMITED , 400 KV GSS SURPURA , JODHPUR (RAJ.) A PRACTICAL TRAINING REPORT
RAJASTHAN RAJYA.docx (Size: 93.78 KB / Downloads: 29)
INTRODUCTION
In the beginnig of the electrical age, electricity was generated,transmitted and distributed in the form of direct current and voltages were low. with the development of transfer,ac system has become predominant . the present day large power systems has been possible only due to adoption of ac system.
The present day electrical power generator system is ac . the electrical power is produced at power stations which are located at favorable places quite away from consumers. it delivers to consumers through large network of trasmission and distribution . for the further distribution of electrical supply grid station plays an important role.
Sometimes it becomes necessary to use dc, at the time, ac can be converted to dc by the use of rectifiers. int the short ac is of utmost importance.
Discription about single line diagram
Figure attached shows key diagram fo a typical 400/220/132 kv surpura grid station.
The diagram of this grid station is explained as under:-
• There are six 400 kv incomig lines connected to the bus bars. Each incoming lines is capable of suppling the sub station load. All these lines can be loaded simultaneously to share the grid station load the three lines arrangement increases the reliability of the system. In case there is a break down of one incoming line, the continuity of supply can be maintain by the other line.
POWER TRANSFORMER
• Tranformer is a static device that transfers electrical energy from one circuit to another through inductiverty coupled conductors the transformer’s coils.
• Transformer can be either step-up or step-down transformer.
• In gss five power transformers are used.
• Secondary coil trun connected to load and primary coil trun connected to power source.
CONSERVATOR
Conservator with valiation of temperature there is corresponding variation in oil volume. To account for this, an expansion vessel called conservator is added to hemp with a connecting pipe to main tank. In smaller transformers this vessel is open to atmosphere through dehydrating breathers in large transformer, an air bag is mounted inside the conservator with inside bag open atmosphere through breathers and outside surface of bag in contact with oil surface.
ON – LOAD TAP-CHANGER
On-load tap changers are employed to change the turn ratio of the transformer to regulate system voltage while transformer is delivering normal load. With the introduction of on-load tap changer, operating efficiency of electrical system has considerably improved.
Tapping in 16 equal of 1.25% each provided at common end of series winding for ±10% voltage variation of 400KV side voltage
TRANSFORMER FIRE PROTECTION
A special fixed pipe system connected to a reliable source of fire protection water supply and equipped with water spray nozzles for specific water discharge and distribution over the surface or area to be protected. The piping system is connected to the water supply through an automatically actuated deluge valve, which initiates flow of water. Automatic actuation is achieved by operation of automatic detecting equipment installed along with water spray nozzles.
INSTRUMENT TRANSFORMERS
The lines sub station operate at high voltage and carry current of 1000 of amperes. The measuring instruments and protective devices are designed for low voltages ( for generally 110 volts ) and currents ( about 5 a ) .therefore, they not work satisfactory if mounted directly on the lines this difficulty is overcomes by installing instrument transformers on the power lines. The function of his instrument transformers is to transfer voltage or current in the power lines to values which are convenient for the operation of measuring instrument and relays. There are two types of instrument transformers viz ;
CAPACITOR VOLTAGE TRANSFORMER
A capacitor voltage transformer (cvt) is a transformer used in power systems to step-down extra high voltage signals and provide low voltage signals either for measurement or to operate a protective relay. In its most basic from the device consists of three parts : two capacitors across which the voltage signal is split , an inductive element used to tune the device to the supply frequency and a transformer used to isolate and further step-down the voltage for the instrumentation or protective relay.
CONTROL ROOM
in surpura gss not only remote control carry the appropriate mean ny which circuit breaker may be open or close but also indicating device, indicating lamps, isolating switches, protective relays, secondary circuit and wires are located here and most important “ no load tap changer “ for transformer is available. There is a panel for synchronizing. Different panel are located at different stages and on each control panel switch is provied on the board.
Colors of signals are synchronized as follows:-
• Red- for circuit breaker or isolator switch is in closed position.
• Green- for circuit breaker is in open condition.
• Amber- indicates abnormal condition.
POWER LINE CARRIER COMMUNICATION SYSTEM (PLCC)
Whenever some breakdown occurs in the transmission network at any place, the message to rectify the fault must be sent to all sub station. Quickness is the first priority .the ordinary telephone network cannot be used as it already overloads and remains engaged. Therefore, the same power lines, which carry energy, are used for this purpose. The signal is modulated by hf carrier and is send as radio waves through the power lines. This system is known as power line carrier communication system
DC SYSTEM
DC SUPPLY (220 volt) is the heart of G.S.S. it energized all protection and relays system. All the protection system at the G.S.S. is based of DC system, because if we have no AC in that case only protection system will be continuously in the circuit . so for this prupose the battery are used at G.S.S.
CONCLUSION
With an ever increasing demand of electricity , electrical ingineer worldwide keeps looking for aways , to improve , not only generation of electricity but also its transmission and distribution.
Traning at 400 kv gss surpura , jodhpur gives the nsight of the real instruments used. There are many instruments like transformer , ct , pt , cvt , la , relay , plcc , bus bars , capacitor bank , insulator , isolators , control room , battery room etc.
There are various occasion when relay operate and circuit breaker open , load shedding , shut down , which has been heard previously.
To get insight of the substation , how things operate , how things operate , how things manage all is learned there. Practical traning as a whole proved to be extremely informative and experience building and the things learnt at it would definitely help a lot in snapping the future ahead a better way.