Voltage Drop Study And Analysis

VOLTAGE DROP STUDY AND ANALYSIS

In an electric circuit the existing energy of a voltage supply decreases as electric current travels through the components that does not supply voltage i.e. passive elements of an electrical circuit. This is called Voltage Drop. Each point in a circuit can be assigned a voltage thats proportional to its electrical elevation, so to speak. Voltage drop is simply the arithmetical difference between a higher voltage and a lower one. The National Electrical Code states that a voltage drop of 5% at the furthest receptacle in a branch wiring circuit is acceptable for normal efficiency

There are two methods by which voltage drop study and analysis can be done:

1. Manual
2. ETAP

Voltage drop of the circuit conductors is calculated by multiplying the complete resistance of the circuit conductors by the current through the circuit:

VD = I x R

I = Load in amperes

R = Resistance of the conductor

This method cannot be used for 3 phase circuits.

The voltage drop of circuit with already installed conductors can be calculated by:

VD = 2 * K * Q * I * D/CM - Single Phase

VD = 1.732 * K * Q * I * D/CM - Three Phase

VD = Volts Dropped

K = Direct Current Constant

Q = Alternating Current Adjustment Factor

I = Amperes

D = Distance

CM = Circular-Mils

Since 1970s, ETAP has been a significant designing podium utilized for designing, analyzing, and optimizing electrical power systems. ETAP is a completely assimilated Electrical software solutions comprising of load flow, arc flash, short circuit and more. Its flexible performance makes it apt for all companies in any shape or form.

Operation Technology, Inc. is the developer of ETAP, the most wide-ranging analysis software for the simulation, design, operation, control, monitoring and automation of power systems. ETAP is the industry leader used worldwide in all types and sizes of power systems such as manufacturing, oil and gas, steel, mining, cement, and more.

We can approximate the voltage drop along a circuit as:

Vdrop= |Vs| - |Vr| ~ IR·R + IX·X

Where, Vdrop= voltage drop along the feeder

R= line resistance

X= line reactance

IR= line current due to real power flow (in phase with the voltage)

IX= line current due to reactive power flow (90 degree out of phase with the voltage)

The biggest fault happens under leading power factor and heavy current. The approximation has an error less than 1% for an angle between the sending and receiving end voltages.

This estimation brings two crucial factors about voltage drop into the light:

Resistive load: At large power factors, the voltage drop is related directly to the resistance of the conductors. The resistance plays a crucial role, even though the resistance is generally less than the reactance.

Reactive load: At medium or small power factors, the voltage drop relates mostly to the reactance of the conductors. Because the reactance is usually larger than the resistance, the reactive load causes most of the voltage drop. Poor power factor significantly increases voltage drop.