Date post: | 09-Jan-2016 |
Category: |
Documents |
Upload: | mallikarjun-reddy |
View: | 27 times |
Download: | 1 times |
of 12
Slide 1
MV & LV Capacitor Sizing1Fundamental Circuit Elements
Resistor Current in phase with Voltage
InductorCurrent lagging voltage by 90 deg
CapacitorCurrent leading voltage by 90 deg
Basics....Capacitor Sizing2Electrical Power has 2 components
Active PowerPower used for the functional output requirements
Reactive PowerPower consumed by load to meet its magnetic field requirement
Reactive Power....Capacitor Sizing3What is Power factor
Cosine of the angle by which apparent power (KVA) is out of phase with respect to active Power
Basics....Capacitor Sizing4Overloading of transformerHigher voltage drop throughout systemIncrease I2R lossesIncreased rating of equipmentHigher kVA demandLevy of Penalty by EBs
Effect of reactive Power on the system....Capacitor Sizing5KVA = (kW2 +kVAR2)Cos = kW / kVA ie. kW/ (kW2 +kVAR2)
As we can see as the power factor increases the reactive power reducesHence power factor improvement is the key to reduction of reactive power. The best method for this is using capacitors
Some more basic formulas....Capacitor Sizing6KVAR requirementType of compensationWhere to compensate
Selection of capacitors....Capacitor Sizing7HV level or LV levelCapacitor at individual loads or central compensationGroup compensationLoad characteristicsReactor required
Where to compensate....Capacitor Sizing8Fixed (For HT motor terminals)Variable ( LT bus level )
Type of compensation
Capacitor Sizing9Calculation LT capacitor
KVAR required = Connected load x Demand factorDemand factor = [Tan (cos-1 initial pf) - Tan (cos-1 Final pf)]
KVAR requirement
Capacitor Sizing10Calculations - HT capacitor
KVAR requirement
Capacitor Sizing11Capacitor kVAR should be less than the No load kVA of the motorIn case series reactor is used, capacitor voltage to be increased to account for reactor voltage drop
Points to be noted
Capacitor Sizing12