Calculations:Electrical Design Guideline: Difference between revisions

Latest revision as of 16:11, 10 November 2023

Electrical Design Calculations Guideline

Figure 1 Power Line

Electrical design calculations guidelines establishes minimum requirements for generating electrical calculations on projects. Electrical calculations should be made for all projects that include electrical components. Design calculations may be made either manually or by computer programs. At a minimum, the following types of calculations should be made where applicable:

* Load calculations

* Conductor sizing

* Conduit sizing

* Motor branch circuit sizing

* Power factor improvement

* Transformer primary and secondary circuit sizing

* Voltage drop

* Motor starting voltage dip

* Short circuit analysis

* Lighting levels

* Grounding in substations where step potentials are of concern

* Harmonic distortion analysis

* Cable pulling calculations

* Generator capability/motor starting.

Basic Requirements for Electrical Calculations

The following are basic requirements for electrical calculations:

Non-computer generated calculations must be on standard project calculations sheets.
Calculations generated by computer programs must conform with the following procedures:
1. Include all heading information on each sheet
2. Insert comments wherever possibly to clarify concepts and actions taken in the computer input
3. Provide clear documentation of electrical geometry, support conditions, load application, and load requirements
4. Provide where practicable sketch of model indicting nodes, materials, connectivity, etc.
5. Provide electronic copy on CD or other suitable device of analysis input and output with hard copy calculations.
6. Provide manual checks of pertinent results (e.g. service size, main feeder voltage drop) for computer generated output.

Calculations:Electrical Design Guideline/Basic Electrical Engineering Formulas

@@ Line 28: / Line 28: @@
 ## Provide manual checks of pertinent results (e.g. service size, main feeder voltage drop) for computer generated output.
-=== Basic Electrical Engineering Formulas ===
-==== List of Symbols ====
-''V'' - Voltage (volts)
-''I'' - Current (amps)
+{{SUBPAGES:{{FULLPAGENAME}} |depth=1|linked=true|sep=<br>}}
-''R'' - Resistance (ohms)
-''X'' - Reactance (ohms)
-''Z'' - Impedance (ohms)
-''W'' Real Power (watts)
-''θ'' - Phase angle whose cosine is the power factor
-''eff'' - Efficiency
-==== Direct Current (DC) Formulas ====
-'''Basic Formulas'''
-===== Resistance =====
-: <math>R={V \over I}</math>
-: <math>R={V^2 \over P}</math>
-: <math>R={P \over I^2}</math>
-===== Volts =====
-: <math>V=I \times R</math>
-: <math>V={P \over I}</math>
-: <math>V=\sqrt{P \times R}</math>
-===== Power =====
-: <math>P=V \times I</math>
-: <math>P=I^2 \times R</math>
-: <math>P={V^2 \over R}</math>
-===== Current =====
-: <math>I={P \over V}</math>
-: <math>I={V \over R}</math>
-: <math>I=\sqrt{P \over R }</math>
-==== Alternating Current (AC) - Single Phase ====
-''Note: V denotes line to neutral voltage.''
-'''Basic Formulas'''
-Impedance '''''Z''''' (''ohms'')
-: <math>Z={V \over I }= \sqrt{R^2+X^2}</math>
-Volts '''''V''''' (''volts'')
-: <math>V={I \times Z }</math>
-Real Power '''''P''''' (''watts'')
-: <math>P=V \times I \times cos \phi</math>
-Power Factor
-: <math>pf=cos \phi</math>
-: <math>pf={P \over S}</math>
-Apparent Power '''''S''''' (''volt-ampere'')
-: <math>S=V \times I</math>
-Reactive Power '''''Q'''''  (''volt-ampere-reactive'')
-: <math>Q=V \times I \times sin \phi</math>
-Real Power '''''P''''' (''watts'')
-: <math>P=V \times I \times cos \phi</math>
-Voltage Drop
-: <math>V_d=2 \times (I \times R \times cos \phi + I \times X \times sin \phi)</math>
-where:
-:: <math>V_d</math> = voltage drop
-:: <math>cos \phi</math> = load power factor
-:: <math>sin \phi</math> = load reactive factor
-:: <math>X</math> = reactance
-:: <math>R</math> = resistance
-==== Alternating Current (AC) - Three Phase ====
-''Note: V denotes line to neutral voltage.''
-'''Basic Formulas'''
-Apparent Power '''''S'''''
-: <math>S=\sqrt {3} \times V \times I</math>
-: <math>S=\sqrt { P^2 + Q^2}</math>
-Real Power '''''P'''''
-: <math>P=\sqrt{3} \times V \times I \times cos \phi</math>
-Reactive Power '''''Q'''''
-: <math>Q=\sqrt{3}\times V \times I \times sin \phi</math>
-Power Factor '''''pf'''''
-: <math>pf={P \over S}</math>
-Voltage Drop
-: <math>V_d=\sqrt{3} \times (I \times R \times cos \phi + I \times X \times sin \phi)</math>
-where:
-:: <math>V_d</math> = voltage drop
-:: <math>cos \phi</math> = load power factor
-:: <math>sin \phi</math> = load reactive factor
-:: <math>X</math> = reactance
-:: <math>R</math> = resistance
-==== Motors ====
-horsepower (hp) = 746 watts.
-'''''Note''': Motor hp rating relates to motor mechanical output. To determine motor input kVA requirements, the motor efficiency and power factor must be accounted for. In general, for preliminary or rough load calculations, assume:''
-kVA of electrical input power for 1 hp of motor.
-'''''Example'''''
-'''''Condition''': A motor control center with a total connected horsepower of 337 hp can be assumed to require 337 kVA of input power. This is a conservative value, particularly for larger motors.''
-:: Torque  = (hp x 5250)/revolutions per minute (rpm)
-:: <math>Torque = {hp \times 5250} \over {RPM}
-:: Fan hp  = (cubic feet per minute [cfm] x pressure)/(33000 x eff)
-:: Pump hp = (gallons per minute [gpm] x head x specific gravity)/(3960 x eff)
-''Motors (Single Phase) ''
-hp = (V x I x eff x pf)/746
-''Motors (3 phase) ''
-Synchronous Speed: ns  =  (120)(Frequency)/(# of Poles)
-( )
-V I 3 eff pf
-hp
-=== Sample Calculations- ===
-'''Under Construction'''