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Electricity distribution :
- Law e ff ecting ac power distribution:P=((I)^2)*R. So transmission needs to be done at high voltage,low current level to avoid power loss. General information:
- In Pakistan di ff erent ratings based transmission lines has been established,e.g 11kv,66kv,32kv,220kv,500kv.
- In future program ,Bhasha Dam ,s transmission network is planned to be at 750 kv.
- (^) In U.S 1200kv transmission lines are also established. In general at generating sites, voltage is step up for transmission then again step down at feeders for consumers use. Setup at P.O.F: Sources:
- Power house: 14 MW at 11kv Peak load=32MW
- (^) IESCO(WAPDA):18-20 MW at 132kv
Wapda,s load supply substations are located as: ->SS East(2 step down transformers with rating of 10/ MVA) ->SS West(2 step down transformers with rating of 10/ MVA) ->SS North(1 step down transformers with rating of 10/ MVA) ->IN P.O.F :11KV & Above---- F 0E 0 HT 400v & Below-- F 0E 0 LT
Transmission within P.O.F: Maximum transmission via underground transmission system. Two types of cable used:
PILC:
Transmission outside P.O.F:(at 400 v)
- Overhead system used.
- Voltages are step down to 400v & transmitted via PVC cables. PVC cable:(poly venyl chloride cable) Low voltage copper conductor PVC cable is widely used for home appliances wiring,internal wirings for lightening circuits in factories & in power supply for office automation.
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Diagrammatic representation of Transmission
& distribution :
Visit to 132 KV Primary substation(from
WAPDA):
Components:
132 kv circuit breakers Isolator switches Lightening arrestors Current transformer(CT) Potential transformer(PT) Power transformer
- Isolaters/disconnectors: A disconnector or isolator switch is used to make sure that an electrical circuit can be completely de-energised for service or maintenance.
For protection.
- It step down the current level to be safely measured via meters.
- In case of error at other than within power transformer,CT will experience current di ff erence & will energize di ff erential relays to trip the circuit. .
- CT works with secondary shorted to avoid arcing.
PT:
use to measure very high voltages use for protection & metering purposes..
WEST1:
- C.T,s ratio :600/5A
- (^) P.T,s ratio:11000/110v Power factor:0. Power transformer: 132kv/11kv
- Buckle relay:
In case of any fault within power transformere.g winding fault,oil is cinverted to gas on expansion ,energizes the gas operatedrelay called buckle relay to trip the circuit.
Normally o ffl oad tap changing is used for voltage improvement
- Oil used for cooling & insulation
- Breather:space in oil tank sucks air,it(if humid) may cause hydration of oil & decrease it,s dielectric strength,. To avoid it,air is fi rst pass through silica for dehydration.
->feeder protection relays (between two substations ) are also deployed.di ff erential relay HO4 is used. ->for transformer CDG(over current realy) is used.
In some phases p.o.f ,distribution system used while in other phases WAPDA,s distribution system installed.
LT overhead lines:
General diagram:
- LT shalke insulator: It insulates the pole from the line for safety. It is used at start & at end point of line.
- HT disc insulator: Similar role as shakle,but used in HT lines(2 HT overhead lines are in P.O.F).
- LT Pin insulator:similar role as shakle,but used at mid distribution poles.
- HT pin insulator:similar role as LT pin , but used at HT lines.
- Steel tubler pole: Material of pole:steel Shape :tubler(tube like)
- Armd cable:
It is the main supply cable(400v) supported by pole.
- Distance b/w two poles =150 ft
- Length of pole:30ft(25 ft above the ground) Underground fault tracer machine(FOSTER SET):
- 220v supply to machine.
- Other equipmentsare:ground phone Battery Head phone It has two parts: I. TDR(time domain re fl ector) It works on Murray loop test. A method of localizing a fault in a cable by replacing two arms of a Wheatstone bridge with a loop formed by the cable under test and a good cable connected to the far end of the defective cable. It give approximate distance of fault. II. (^) Surge generator: Pulses discharges at fault points.
Street light control panel : Radiation efficiency=energy radiated in visible spectrum/total energy radiated
A2 General supply tarrif (commercial ):(rates wihout taxes)
Some motor ratings at P.O.F:
- Squirrel cage induction motor Kw: Rpm: V:415+-6% Hp: A: 3 phase f=50. Ambient temp:40.c Delta connected
- (^) Induction motor Insulation class :B Frame:c- B.H.P= V:
A:
Rpm:1500/ f=50. Connection:star
Water distribution: Flow diagram:
BPH(booster pump house) visit:
- Minimum water depth :5 feet
- (^) Analysis test /3 months
- Bacterial test /month: Criteria for the test:
of coliforms for 100ml(treated water)=1-
of coliforms for 100 ml(untreated water)=less than 10
Water treatment plant(Filter):
