The Load Flow and Voltage Drop study is the most basic and commonly needed electrical study. The Load Flow study will show the power in kVA or Amperes that is being handled by all of the individual electrical components, e.g. transformers, conductors and panels in the system. This allows a determination of equipment rating margins and reserve capacity loading percentage. The voltage drop calculations for each bus and at all equipment will indicate if equipment supply voltages are at levels which will adversely affect equipment life or performance.
Loads can be modeled as any combination of constant kVA, constant current and constant impedance. The study will take into account tap positions on transformers and indicate where tap changes should be made.
Load Flow / Voltage Drop studies may cover conventional voltage drop analysis, loss analysis, power factor considerations, capacitor placement, long line charging effects, impact loading for motor starting and co-generation analysis.
A base-line Load Flow / Voltage Drop study should be performed anytime major changes are made to the power distribution system.
For all Load Flow and Voltage Drop Studies each regional office of PAA uses the latest SKM DAPPER software package equipped for 2000 buses. SKM is an international leader in Electrical Systems Analysis software. All PAA Engineers are graduates of SKM training.
EXAMPLE
BALANCED VOLTAGE DROP AND LOAD FLOW ANALYSIS
VOLTAGE EFFECT ON LOADS MODELED
VOLTAGE DROP CRITERIA: BRANCH = 3.0% BUS = 5%
BUS 100, DESIGN VOLTS 480, BUS VOLTS 388, %VD 19.25,
PU BUS VOLTAGE 0.808, ANGLE –1.2 DEGREES
LOAD TO BUS 110 FEEDER AMPS: 220.2 VOLTAGE DROP: 6 %VD 1.6
PROJECTED POWER FLOW 118.9 KW 87.9 KVAR 147.8 KVA PF: 0.8 LAGGING
LOSSES THROUGH FEEDER: 2.3 KW 0.2 KVAR 1.1 KVA
LOAD TO BUS 120 FEEDER AMPS: 149.0 VOLTAGE DROP: 4 %VD 0.79
PROJECTED POWER FLOW 80.3 KW 59.7 KVAR 100.1 KVA PF: 0.8 LAGGING
LOSSES THROUGH FEEDER: 1.1 KW 0.2 KVAR 1.1 KVA
LOAD TO BUS 130 FEEDER AMPS: 369.2 VOLTAGE DROP: 52 %VD 10.89
PROJECTED POWER FLOW 199.1 KW 147.5 KVAR 247.9 KVA PF: 0.8 LAGGING
LOSSES THROUGH FEEDER: 32.7 KW 11.7 KVAR 34.7 KVA