20-09-2014, 02:05 PM
FEEDERS AND ITS PROTECTION
FEEDERS AND ITS.pptx (Size: 899.45 KB / Downloads: 43)
OBJECTIVE
TO EXPLAIN ABOUT SUB STATION EQUIPMENTS
TO ANALYSE VARIOUS METHODS OF PROTECTION OF FEEDERS MAINLY DISTANCE PROTECTION
ABOUT SUBSTATION
It was started on FEB 2006.
It is located near vepanjeri which is 15km away from chittoor.
It covers an area of 56.08 acres.
Investment Cost : Rs. 57 crores.
It receives power from Kadapa-400KV and step downs to 220KV with the help of power transformer,315MVA.
The power supply to the sub-station is received from 33KV line from kottapalli mitta substation- 132/33KV
There are five outgoing feeders, in that one is 400kv and other four are 220kv,they are
400KV Feeders- Chennai
220KV Feeders- Chittoor-I , Chittoor-II,
Renigunta-I , Renigunta-II.
SUBSTATION EQUIPMENTS
LIGHTNING ARRESTERS
It is protective divice,which conducts high voltage surges to ground. discharge the surges.
WAVE TRAP
It traps the high frequency communication signals sent on the transmission line and divert them to telecom room in the sub-station.
CVT’s
It is used to measuring voltages & Protecting device.
ISOLATORS
SPECIFICATIONS:
Make :ELPRO
Type :HCB
Rated Voltage:420KV
Normal Current:2000A
CIRCUIT BREAKER
440KV Breaker
Make : ALSTOM
Medium Interruption:SF6
Rated Voltage:440KV
Operating Mechanism: SPRING(type)
Rated Breaking Current:10KA
Rated Making Current:100KA
FEEDERS
The word `feeder’ means the connecting link between two circuits.
The feeder could be in the form of a transmission line (short, medium or long) or this could be a distribution circuit.
The probability of faults occurring on the lines is much more due to their greater length and exposure to atmospheric conditions
Methods of protection
The various methods for protecting the feeders are: 1. Over current protection
2. Differential Pilot-wire protection
3. Distance protection.
Comparison between various protective schemes
Over current protection is the simplest and cheapest form of protection.
It is difficult to apply and if a change in circuit occurs, it needs readjustments.
In case where distance protection is costly, over current protection is used for phase and ground faults on station service, electric utilities (distribution circuits) and on some sub transmission lines.
Over current protection is normally used as back up protection where the primary protection is provided with distance schemes.
Advantages of distance protection
Whenever over-current relaying is found slow or is not selective, distance protection should be used.
Since the fault currents depend upon the generating capacity and system configuration, the distance relays are preferred to the over current relays.
Selection of impedance, reactance and mho relays
Reactance relays are normally preferred for ground fault relaying.
For phase fault protection:
For short transmission lines, reactance type relay is used because more of the line can be protected at high speed.
The mho type relay is most suited for long lines where especially there are more chances of severe synchronizing power surges on the system.
The impedance relay is used for protecting medium length transmission lines.
CONCLUSION
Power systems have evolved over decades. Their primary emphasis has been providing a reliable and economic supply of electrical energy to their customers. Hence all equipments are to be well Protected
Distance Protection is exclusively used for the Protection of Feeders.