PRACTICAL WORK BOOK
For Academic Session 2013
ELECTRICAL POWER DISTRIBUTION &
UTILIZATION (EE-357)
For
TE (EE)
Name:
Roll Number:
Class:
Batch: 5
Department :
TALHA ARSHAD
BEE-14208
7
ELECTRICAL ENGINEERING
Semester/Term:
Department of Electrical Engineering
NED University of Engineering & Technology
SAFETY RU LES
1. Please don t touch any live parts.
2. Never use an electrical tool in a damp place.
3. Don t carry unnecessary belongings during performance of practicals (like
water bottle, bags etc).
4. Before connecting any leads/wires, make sure power is switched off.
5. In case of an emergency, push the nearby red color emergency switch of the
panel or immediately call for help.
6. In case of electric fire, never put water on it as it will further worsen the
condition; use the class C fire extinguisher.
Fire is a chemical reaction involving rapid oxidation
(combustion) of fuel. Three basic conditions when
met, fire takes place. These are fuel, oxygen & heat,
absence of any one of the component will extinguish
the fire.
Figure: Fire Triangle
B(think
If there is a small electrical fire, be sure to
use only a Class C or multipurpose (ABC)
fire extinguisher, otherwise you might make
the problem worsen.
C(think circuits):
electrical fires
The letters and symbols are explained in left
figure. Easy to remember words are also
shown.
A(think
ashes):
paper, wood etc
barrels):
flammable liquids
Don t play with electricity, Treat electricity with respect, it deserves!
Electrical Power Distribution & Utilization
Contents
NED University of Engineering and Technology
Department of Electrical Engineering
CONTEN TS
Lab.
No.
1
2
3
4
5
6
7(a)
7(b)
8(a)
8(b)
9
10
11
12
13
Dated
Title of Experiments
Parts of power cable.
Cable Size Calculation for the given
load.
Measure the High Level Voltage,
Current
and
Resistance
using
Instrument Transformers & Megger.
Operation and constructional features
of a Distribution Transformer.
Substation Equipments and its oneline diagram.
Power Factor Improvement
Using Calculux
First project on design of general
lighting scheme for an office.
Second project on design of general
lighting scheme for an office.
To design a task & accent lighting for
an office (optional).
Different types of lamps & comparing
the Illuminance level.
Calculate the charges in
Industrial/commercial bill.
Captive Power Generation (DG SetDiesel Generating Set). optional
Home Electrical Wiring
Earth Resistance and Soil Resistivity
Measurment
Page
No
Remarks
1-3
4-7
8-9
10-11
12-15
16-19
20 - 2 2
23-24
25-27
28-29
30 - 3 2
3 3- 36
3 7 - 40
41-43
4 4- 50
Prepared by: Muhammad Mohsin Aman 2012
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 01
Department of Electrical Engineering
LAB SESSION 1
Power Cable
OBJECTIVE
To dissect the power cable into it s distinguished parts.
APPARATUS
Dissected Cables
Vernier Calliper
Screw Gauge
THEORY
A cable is defined as an assembly of conductors and insulators used for the transfer of power
in densely populated urban areas. Cables are mostly laid under the ground in order not to
disturb the land beauty and to avoid using the land for power transmission purposes.
Figure: Parts of cables
PARTS OF CABLE
A cable is composed of the following parts;
Core
All cables either have a central core (conductor) or a number of cores made of strands of
Copper or Aluminum conductors having highest conductivity. Conductors are stranded in
order to reduce the skin effect.
Insulation
It is provided to insulate the conductors from each other and from the outside periphery. The
common insulating materials are Poly Vinyl Chloride (PVC) and Polyethylene.
Metallic Sheath
Metallic Sheath protects the cable against the entry of moisture. It is made of lead, some alloy
of lead or Aluminum
-1-
Electrical Power Distribution & Utilization
Lab Session 01
NED University of Engineering and Technology
Department of Electrical Engineering
Bedding
In order to protect the metallic sheath from injury, bedding is wound over it. It consists of
paper tape compounded with a fibrous material.
Armoring
It consists of one or two layers of galvanized steel wires or two layers of steel tape, to avoid
the mechanical injury. Armoring provides mechanical strength to the cable.
Serving
A layer of fibrous material, used to protect the armoring.
Figure: Cross Sectional View of Cable
Copper
S.
No
1
2
3
4
5
6
Properties
Annealed
Hard
Drawn
Resistivity at 20 C
1.72
1.78 to 1.8
(ohm-m × 10-8)
Temperature coefficient of
0.00393
0.00393
electrical resistance at 20 C
Coefficient of linear
17.0 x 10-6 17.0 x 10-6
expansion per unit per C
Thermal conductivity
384
384
W/mK
Density kg/m3
8.89 x 10-3 8.89 x 10-3
Specific heat kJ/kg K
0.394
0.394
PROCEDURE
Practical demonstration
RESULT
Cables have been studied and their operation is understood.
-2-
Aluminum
Hard
Annealed
Drawn
2.8
2.3
0.00403
0.00403
23.0 x 10-6
23.0 x 10-6
209.4
209.4
2.71 x 10-3
0.904
2.71 x 10-3
0.904
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 01
Department of Electrical Engineering
EXERCISE:
You are given three cables of unknown cross section: find out the following information
about each cable.
S.
No
1
2
3
No. of
Cores
No. of
Strands
Diameter Cross Sectional
(m)
Area (mm2)
Nomenclature
Give the definition of following terms:
1. Coefficient of linear expansion
2. Temperature coefficient
3. Thermal conductivity
4. Resistivity
5. Ampacity
Explain the following processes:
1. Annealing & Importance
2. Galvanizing
3. Vulcanizing
Give short answers to the following questions:
1. What will be the difference in size of Cu & Al conductor for same installation?
(Hints: refer table)
2. Why do we use ACSR conductors for transmission not in distribution?
3. Mostly Aluminum is used in transmission system as a conductor, why not Cu as a
conductor?
________________________________________________________________
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______________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
________________________________________________________________
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-3-
Electrical Power Distribution & Utilization
Lab Session 02
NED University of Engineering and Technology
Department of Electrical Engineering
LAB SESSION 02
Select the Appropriate Cable Size
OBJECTIVE
Select the appropriate cable size for the given load.
APPARATUS
Given Load
Cable Tables Book
THEORY
The cable selection procedures set out in this LAB SESSION will give the basic guidelines to
be followed to determine the minimum size of cable required to satisfy a particular
installation condition.
The following three main factors influence the selection of a particular cable to satisfy the
circuit requirements:
(a) Current-carrying capacity dependent upon the method of installation and the presence
of external influences, such as thermal insulation, which restrict the operating temperature of
the cable.
(b) Voltage drop dependent upon the impedance of the cable, the magnitude of the load
current and the load power factor.
(c) Short-circuit temperature limit dependent upon energy produced during the shortcircuit condition.
TASK:
Determine the size of cable required & voltage drop in the cable.
SITUATION:
A 150kW, three phase load is supplying from a 400V, 50Hz supply. The circuit is protected
using BSEN 60898 Type B circuit breaker and is situated 150m away from the distribution
board. It is run with two other power circuits and is buried in the ground at a depth of 0.8m.
There the soil resistivity is 1.2 ºC.m/W. The temperature within the installation can be
assumed to be 30 C. Calculate the size of cable required, assume armored Cu cable is used
here.
150 kW
LOAD
DB
150m
-4-
Electrical Power Distribution & Utilization
Lab Session 02
NED University of Engineering and Technology
Department of Electrical Engineering
METHOD:
STEP #01
Determine the current requirements of the circuit. This current is known as Design current,
either specified by the manufacturer or can be calculated by the formulae.
Design Current (IN) =
kilo Watt Power
Single Phase Voltage x power factor
(For 1 phase)
Design Current (IN) =
(For 3 phase)
kilo Watt Power
3 x Line Voltage x power factor
If kVA power is given the above formula will change accordingly.
If motor power is given in hp then use the conversion 1hp=746 Watts.
Here,
Design Current (IN) = _______________________ =
Amps
STEP #02
Determine the method of cable installation to be used.
Installation Conditions: The current-carrying capacity of a cable is dependent on the
method of installation to maintain the temperature of the cable within its operating limits.
Different methods of installation vary the rate at which the heat generated by the current flow
is dissipated to the surrounding medium.
Specific conditions of installation are there like cables installed with or without wiring
enclosures in air, in the ground or embedded in building materials.
STEP #03
Determine the environmental conditions in the vicinity of the cable installation, where
applicable, like
(i)
the ambient air or soil temperature
(ii)
the depth of laying rating factor
(iii)
the soil thermal resistivity rating factor
Use any cable s table book to find out the correction factor values.
Here, the correction factors from the tables:
Grouping Factor (Cg):
_______
Ambient Temperature (Ca): _______
Soil Resistivity Factor (Cr): _______
Depth of laying factor (Cd): _______
STEP #04
Apply the correction factors to determine the current carrying capacity (Ic) of the cable by
using the formula.
Current carrying capacity of cable =
Design current
-5-
.
Electrical Power Distribution & Utilization
Lab Session 02
NED University of Engineering and Technology
Department of Electrical Engineering
Correction Factors
The above factors should be applied according to the design situation.
Current carrying capacity of cable = ____Design current
.
Cg x Ca x Cr x Cd
Here,
Current carrying capacity of cable = ________________________
Current carrying capacity of cable = ______________
Minimum cable size = _____________ mm2
Finding the Protective Device Size (IF).
The design current should be no greater than the fuse rating. The fuse rating must be no
greater than the current carrying capacity of the cable. The current carrying capacity of the
cable should not be greater than the tabulated capacity of the cable i.e.
IN
IF
IC
The Worst-Case Scenario
A cable may experience various different environments along its route. For example it may
start at a switchboard, run through the switch room in a trench with a lid or steel flooring,
pass through a duct in a wall and under a roadway, run a long way directly buried and finish
on a ladder rack at the consumer. At each of these environments the thermal resistivity and
ambient temperature will be different. The environment that causes the most derating of the
rated current should be taken and used for the whole cable.
DETERMINATION OF VOLTAGE DROP FROM MILLI VOLTS PER AMP -METRE
According to IEE Regulation 522-8 of the 15th edition, it is stipulated that:
The voltage drop within the installation does not exceed a value appropriate to the safe
functioning of the associated equipment in normal service. For final circuits protected by an
over current protective device having a normal current not exceeding 100A, this requirement
is deemed to be satisfied if the drop in voltage from the origin of the circuit to any other point
in the circuit does not exceed 2.5 percent of the nominal voltage at the design current,
disregarding staring conditions.
The voltage drop can be determine using the following formula 50 for applications where
only the route length and load current of balanced circuits are known.
Voltage Drop (Vd) =
L x IN x Vc .
1000
where
Vc = the millivolt drop per ampere-metre route length of circuit, as shown in the tables for
various conductors, in millivolts per ampere metre (mV/A.m)
Vd = actual voltage drop, in volts
L = route length of circuit, in meters
IN = the current to be carried by the cable, in amperes.
Here, L = 80m
-6-
Electrical Power Distribution & Utilization
Lab Session 02
NED University of Engineering and Technology
IN = __________
Vc= __________
Department of Electrical Engineering
Amps
mV/A.m
Voltage Drop (Vd) = _________________
1000
Voltage Drop (Vd) =
Hence the selected cable of
length of 80m.
_______
i.e.
mm2 is suitable for normal current of
EXERCISE:
Repeat the above task
(i) With load 20kW at power factor 0.9.
(ii) With L = 130 m
(iii)Assume unarmored cable is used here installed in air.
Answer:
(i)
(ii)
(iii)
mm2
mm2
mm2
-7-
% of 400V.
Amps & cable
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 03
Department of Electrical Engineering
LAB SESSION 03
Measure the High Level Voltage, Current and Resistance
OBJECTIVE
Using measuring instruments measure the high level of voltage, current and resistance.
APPARATUS
Current Transformer
Potential Transformer
Megger
Clip on Ammeter
THEORY
Current Transformers
Ammeters are employed for measurement of current in
circuits. In high voltage transmission lines, it is more feasible
to use Current Transformers for measurement of current owing
to its higher range of measurement. High values of currents
flowing in the transmission lines serve as the primary circuit of
a current transformer. The high current is stepped down to a
much lower value (normally not more than 5A) which is then
measured by an ordinary ammeter. This way, an ammeter is
not exposed to high currents and voltages.
Potential Transformers
For measurement of high voltages, potential transformers are
commonly used. Difference between the potential transformers and
current transformers is that Current Transformers are connected in
series whereas Potential Transformers are connected in parallel.
Among the available range of PTs and CTs, the selection is based on
the following factors
Insulation Class
Primary to Secondary ratio
Continuous thermal rating
Service conditions
Accuracy
Clip On Ammeter
Current is measured only when an ammeter is connected in a circuit in
series. What if the current in any wire connected to a load is required to
be measured. Using an ammeter, we shall first need to disconnect the
load from the source, insert an ammeter and then measure the current.
Instead of doing all this, a clip on ammeter allows current measurement
without disconnecting the line. It operates on the concept of
transformation, as in transformers where flux linkages produce voltages.
- 8-
Electrical Power Distribution & Utilization
Lab Session 03
NED University of Engineering and Technology
Department of Electrical Engineering
Megger
Megger is a name given to an instrument used to measure large
values of resistance. Measuring resistance of machines and
devices is very helpful in determining faults like short circuits
etc. Once a machine faces a fault, its internal resistance gets
changed. Machine resistance is regularly monitored in order to
detect any internal faults occurring in the machines and other
devices.
OBSERVATION
Using Clip on Ammeter measure the current of a single phase load.
Load
Pedestal Fan (
Measured Value (A)
Using Clip on Ammeter
Calculated Value(A)
Using Formula
W)
100W bulb
Tube light ( W) with
ballast (
W)
Two 100W bulbs in parallel
Desktop PC (Personal
computer) ( W)
Using CT (current Transformer) measure the current of a given load.
CT ratio: ________
Load
Primary Current
(Using Clip On Ammeter)
Secondary Current
of CT
1000W
2000W
3000W
Using Megger find the insulation Resistance of
1.
2.
3.
4.
A new cable _____________________
An old cable______________________
Across Burnt Motor Terminals______
_________________________________
found to be___________________
found to be___________________
found to be___________________
found to be___________________
RESULT
Working of measuring instruments practically demonstrated.
- 9-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 04
Department of Electrical Engineering
LAB SESSION 04
Distribution Transformer
OBJECTIVE
To study the operation and constructional features of a Distribution Transformer
APPARATUS
Distribution Transformer
THEORY
Distribution transformer is used to convert electrical energy of higher voltage (usually 11-2233kV) to a lower voltage (250 or 433V) with frequency identical before and after the
transformation. Its main application is mainly within suburban areas, public supply
authorities and industrial customers. With given secondary voltage, distribution transformer
is usually the last in the chain of electrical energy supply to households and industrial
enterprises.
Power Transformer
CONSTRUCTION
There are 3 main parts in the distribution transformer:
Coils/winding where incoming alternating current (through primary winding) generates
magnetic flux, which in turn induces a voltage in the secondary coil.
- 10-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 04
Department of Electrical Engineering
Magnetic core material allowing transfer of magnetic field generated by primary winding to
secondary winding by the principle of electromagnetic induction.
A transformer s core and windings are called its Active Parts. This is because these two are
responsible for transformer s operation.
Tank serving as a mechanical package to protect active parts, as a holding vessel for
transformer oil used for cooling and insulation.
Transformer Accessories
Breather
Pressure relief device
Temperature Indicator
Tap Changer etc
SIGNIFICANCE OF VECTOR GROUPS
Three phase machines, such as transformers, are allotted symbols representing the type of phase
connection and the phase angle between the HV and LV terminals. The angle is described by a clockface hour figure. The HV vector is taken as 12 o clock, the reference, and the corresponding LV
vector is represented by the hour hand.
For example, a Dy11 represents;
D = HV winding is delta connected
y = LV winding is star connected
11 = clock-face reference indicating that the LV vector is at 11 o clock (30o lead)
with reference to the HV vector.
PROCEDURE
Practical demonstration.
RESULT
Complete working of the distribution transformer has been understood.
EXERCISE:
Give the purposes of following parts of Distribution Transformer
1.
2.
3.
4.
5.
Bushings
Conservator or expansion tank
Breather
Pressure relief device
Tap Changer (OFF Load)
- 11-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 05
Department of Electrical Engineering
LAB SESSION 05
Substation Equipments & One Line Diagram
OBJECTIVE
To study the major equipments of the substation and make a one-line diagram.
APPARATUS
A visit will be arranged to a sub-station.
THEORY
An electrical substation is a subsidiary station of an electricity generation, transmission and
distribution system where voltage is transformed from high to low levels using transformers.
Electric power may flow through several substations between generating plant and consumer,
and may be changed in voltage in several steps.
Feeders
The electrical distribution system begins with a source of electrical energy that must be
distributed to each and every electrical load. The starting point of this system, which feeds
electrical energy into it, is known as a Feeder. The electricity delivered by a feeder is actually
distributed to different loads in the system.
Distributors
A distributor is a conductor from which tapings are taken to the consumers. The current
through a distributor is not constant due to the tapings taken off at various places along its
length. While designing a distributor, voltage drop along its length is the main consideration
as the voltage variation limits are about 6% of the rated voltage at the consumer terminals.
Switch Gears
The term switchgear, used in association with the electric power system, or grid, refers to the
combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical
equipment. Switchgear is used both to de-energize equipment to allow work to be done and to
clear faults downstream Panels are the compartments used for switchgear arrangement.
Switching Devices A device designed to close, open, or both, one or more electric circuits.
These include
HRC fuses
Magnetic contactor
Circuit Breaker (Molded Case Circuit Breaker)
Load Break Switch
- 12-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Figure: Fuse
Lab session 05
Department of Electrical Engineering
Figure: Contactor
Figure: Circuit Breaker
One line diagram of a typical distribution system
EXERCISE:
1. Using Magnetic Contactor design and implement the DOL circuit for three phase
Induction Motor. Also explain working.
- 13-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 05
Department of Electrical Engineering
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2. Using Magnetic Contactors design a Star Delta Scheme for three phase Induction
Motor. Also explain working.
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- 14-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 05
Department of Electrical Engineering
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- 15-
Electrical Power Distribution & Utilization
Lab Session 06
NED University of Engineering and Technology
Department of Electrical Engineering
LAB SESSION 06
Power Factor Improvement
OBJECTIVE
To improve the power factor of distribution load
APPARATUS
Delta Connected Capacitor Bank (Module AZ-191b)
Multimeter
Energy Analyzer
Resistive Load Bank
Inductive Load Bank
THEORY
The ratio of the actual power consumed by equipment (P) to the power supplied to equipment
(S) is called the power factor.
P
Re alPower
PowerFactor Cos
ApparentPower S
Where;
P2
S
Q2
The power factor correction of electrical loads is a problem common to all industrial
companies. Every user which utilizes electrical power to obtain work in various forms
continuously asks the mains to supply a certain quantity of active power, together with
reactive power. This reactive power is not transformed or used by the user, but the electricity
supply company is forced to produce it, using generators, wires to carry and distribute it,
through transformers and switching gears.
Power factor correction reduces the Joule losses of the transformers and the cables upstream
of the installation point; reduction in losses, transmitted power being equal, is greater the
lower the power factor value before applying the power factor correction.
The capacitor provides the necessary leading current (-ve Q) which results in reduce line
current flowing in the system. The amount of reactive power needed is given by the following
formula.
QC
P(tan
1
tan
Q
V2
P(tan 1 tan
V2
2
)
C
C
Where,
tan 1 = tan component of initial power factor
tan 2 = tan component of improved power factor
- 16-
2
)
Electrical Power Distribution & Utilization
Lab Session 06
NED University of Engineering and Technology
Department of Electrical Engineering
Applying a star or delta-connected (three-phase load) group of three capacitors of suitable
capacity in parallel to the resistive-inductive load terminals, the capacitive current Ic
absorbed by them, which is in leading quadrature compared to the voltage Vt, opposes the
component in lagging quadrature IL reducing it to I1 or even annulling it, with consequent
decrease in the circulating line current, which takes on the value IR; the best situation is
obtained when IC = IL and I is therefore reduced to the only in-phase component IR.
Using the above relations we can show that
CY
3*C
Star connected and Delta connected capacitors, both have advantages/disadvantages too.
PROCEDURE:
- 17-
Electrical Power Distribution & Utilization
Lab Session 06
NED University of Engineering and Technology
Department of Electrical Engineering
Delta Connected Capacitor Banks (Module AZ-191b):
A
2 F three-phase capacitor bank.
B
L1-L2-L3
4 F three-phase capacitor bank.
Three-phase capacitor bank input terminals, (delta connected three
capacitors with voltage rating 450 V~).
3 single-phase inductors with rated current 1A and inductance of 100
mH.
3 x 100 k 2W resistances.
C
D
Resistive Load Bank (Module RL-2/EV):
R = 360
R = 180
R = 90
V = 220V
V = 220V
V = 220V
I = 0.6A
I = 1.2A
I = 2.4A
P = 132W
P = 264W
P = 528W.
Inductive Load Bank (Module IL-2/EV):
Z = 720
Z = 360
Z = 180
L = 2.3H
L =1.15H
L =0.58H
V = 220V
V = 220V
V = 220V
f =50Hz
f =50Hz
f =50Hz
- 18-
I = 0.3A
I= 0.6A
I =1.2A
Pa = 66VA
Pa = 132VA
Pa = 264VA
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 06
Department of Electrical Engineering
OBSERVATIONS:
Follow the connections shown in figure below and fill up the table:
P.F Correction
P.F Correction
Using 3 x 4µF
Initial Using 3 x 2µF
Load
Active Reactive Apparent
Power New
New
New
New
Combination Power Power
Power
Factor Power
Line
Power
Line
Factor Current Factor Current
RESULT
The method of power factor correction has fully understood.
- 19-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 07(a)
Department of Electrical Engineering
LAB SESSION 07(a)
Introduction to Lighting design software Calculux
OBJECTIVE
To become familiar with the basic environment of lighting design software
Calculux
THEORY
This Lab session will introduce the main feature of lighting design software and with the
environment of Calculux. Calculux Indoor is a software tool which helps lighting designers in
selecting and evaluating lighting systems for offices and industrial applications.
What can you do with Calculux Indoor?
Perform lighting calculations (including direct, indirect, total and average
illuminance) within orthogonal rooms;
Predict financial implications including energy, investment, lamp and maintenance
costs for different luminaire arrangements;
Select luminaires from an extensive Philips database or from specially formatted files
for luminaires from other suppliers;
Specify room dimensions, luminaire types, maintenance factors, interreflection
accuracy, calculation grids and calculation types;
Compile reports displaying results in text and graphical formats;
Support Switching modes and Light regulation factors;
The logical steps used for project specification save you time and effort, while the report
facility gives you the opportunity to keep permanent records of the results.
Installing the program
In order to install Calculux correctly, please stop all other applications before starting the
installation.
To install the program:
1. Start Windows.
2. Connect the USB to your USB port [Let suppose drive (K:) of your computer].
3. Follow the path K:\Calculux
4. Run the setup in the Indoor5.0b
5. Follow the instructions on screen.
Installing the database
1. Here in the folder DB, there is a database of Philips Luminaries
2. Install the database from the DB folder.
Environment of Calculux Indoor Software
When you start Calculux, the Calculux main window is displayed. This window always
contains the menu bar, and if selected, it may also contain a tool bar and/or status line. When
a project file is open and data has been entered, a 2D top view or 3D layout is shown.
- 20-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 07(a)
Department of Electrical Engineering
The menu bar contains the following menus:
1. File
6. View
2. Data
7. Options
3. Calculation
8. Window
4.Report
9. Help
5. Finance
Before Starting your First Project:
Installation of Calculux Indoor has been successful;
Vignettes have been installed;
Phillum files have been installed;
Database has been installed.
Before you start 'My First Project' first you should check the default settings of Calculux.
Checking the default settings
For 'First Project' you are going to check the following default settings:
Environment (options) (default settings concerning the program environment)
Report Setup Defaults (default settings concerning the contents and layout of the
report)
Calculation Presentation Defaults (default settings concerning the Calculation
Presentation)
Environment
Select Environment from the Options menu.
Select the Directories tab.
Check the directory settings of the Project files, Phillum files and Vignette files.
Select the Database tab.
Check the directory settings of the Database files.
Click OK to return to the Main View.
The Environment Options only have to be set after installing Calculux.
Report Setup Defaults
Select Report Setup Defaults from the Options menu.
Select the Contents tab.
In the Included box, select the chapters to be included in the report.
In the Presentation Forms box, select the presentation forms of the calculation presentation
result views.
Select
Textual Table, Iso Contour,Filled Iso Contour
Select the Layout tab.
In the Project Luminaire Information box, select in which way the luminaire luminous
intensity information is to be shown.
- 21-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab Session 07(a)
Department of Electrical Engineering
Select Show Polar Diagram
In the Installation Data box, select which elements are to be displayed in chapter 'Installation
Data' of the report.
Select Show Aiming Angles
In the General box, select which additional information is to be displayed and in which
language the report is to be created.
Click OK to return to the Main View.
Calculation Presentation Defaults
Select Calculation Presentation Defaults from the Options menu.
Select the Presentation Forms tab.
In this tab you can select the elements to be displayed in the calculation presentation result
views.
Select
Textual Table, Iso Contour, Filled Iso Contour
Select the General tab.
In the Show box, select the elements to be displayed by default in the calculation presentation
and report.
Select
Luminaires, Luminaire Code, Luminaire Legend, Drawings,Fill Color Legend,
Room,Connected Field,Connected Grid
In the Iso Contour Method box, select which Iso Contour Method will be used by default for
the calculation presentation.
Select
Relative
Select the Scaling tab.
In the Minimum Report Scale box.
Select
10
In the Sizing box, select the default sizing of the calculation presentation result views, select:
Zoomed Relative to Grid:
Factor
1.000
By setting the above scaling, the size of the defined objects in the calculation presentation
result overviews will be based on the size of the grid and the field. The size is determined by
the 'Zoom Factor'.
Click OK to return to the Main View.
Now start your first project.
- 22-
Electrical Power Distribution & Utilization
Lab session 07(b)
NED University of Engineering and Technology
Department of Electrical Engineering
LAB SESSION 07(b)
Your First Project on lighting design using CALCULUX
OBJECTIVE
First Task of First project:
Design a general lighting scheme of an office using CALCULUX. This will be your
first task of this Lab.
The details are as under:
Room Specifications
Room dimensions
Width 3.50 m
Length 5.60 m
Working Plane Height 0.80 m
Reflections
Ceiling 0.50
Height 2.70 m
Walls 0.30
Floor 0.10
Position (of Left Front side of the room)
X = 0.0
Y =0.0
Required illuminance level
General lighting 300 lux on working plane
Luminaire Specifications
Luminaire type TBS600/135 C7-60
Lamp type TL5 35W
Project Maintenance Factor 0.80
A
A
A
A
Fig: 1st Task
- 23-
Electrical Power Distribution & Utilization
Lab session 07(b)
NED University of Engineering and Technology
Department of Electrical Engineering
Second Task of the First Project:
Let suppose there is a window in the back wall of the room, two luminaries of
the Room Block arrangement have to be moved.
Add a table in the center of the room & write text on table TABLE .
A
A
table
A
A
Fig: 2nd Task
OBSERVATION:
Attach the Self generated Report with each task.
In each report following details should be there
1) Title Page
2) Table of Contents
3) Top project overview
4) Summary
5) Luminaries Details
6) Calculation Results
a) Filled ISO Contour
INSTRUCTION:
All the observation reports should be maintained in a separate file, do not staple the
report with the workbook.
- 24-
Electrical Power Distribution & Utilization
Lab session 08(a)
NED University of Engineering and Technology
Department of Electrical Engineering
LAB SESSION 08 (a)
Your Second Project on lighting design using CALCULUX
OBJECTIVE
First Task of Second Project:
The purpose of this lab is to measure the LUX level on the given working plane. This
will be your first task of this Lab.
The constructional details are as under:
Room Specifications
Room dimensions
Width 7.32 m
Length 7.62 m
Working Plane Height 0.80 m
Reflections
Ceiling 0.50
Height 3.66 m
Walls 0.30
Floor 0.10
Position (of Left Front side of the room)
X= 0.0
Y = 0.0
Illuminance level
To be measured
Luminaire Specifications
Luminaire type
FBS331/218 M6
TBS300/236 M1
Lamp Type
2xPL-L18W
2XTL-D36W
Color
840
840
Project Maintenance Factor 0.80
Luminaires Location
Red Lamps (12 in Number)
Spacing
X- Spacing = 1.2m
Y- Spacing = 1.6m
Position
X=1.20
Y=1.60
Blue Lamps (20 in Number)
Spacing
X- Spacing = 1.5m
Position
X=1.45
Y=2.20
Z=3.66
Y- Spacing = 1.6m
Z=3.66
- 25-
Electrical Power Distribution & Utilization
Lab session 08(a)
Department of Electrical Engineering
6 .5
7
7 .5
8
NED University of Engineering and Technology
A
A
A
A
5.5
6
A
B
B
B
5
B
A
A
A
A
Y(m )
4
4.5
A
B
B
B
3 .5
B
A
A
A
A
2 .5
3
A
B
B
B
1 .5
2
B
A
A
A
A
-0 .5
0
0.5
1
A
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
X(m)
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
Second task of Second Project:
In your second task
1. Group the luminaries in three separate blocks.
2. Make rectangles.
3. Make two separate grids, one for working plane & one for Table.
4. Now calculate the results.
5. Generate & Print the report.
6. Save the project.
- 26-
Electrical Power Distribution & Utilization
Lab session 08(a)
Department of Electrical Engineering
7
NED University of Engineering and Technology
B
B
B
B
B
B
B
6
B
5
Table 2
A
A
A
A
A
A
A
A
A
A
A
A
A
3
Y(m)
4
A
B
B
B
B
B
2
B
Table 1
B
0
1
B
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
X(m)
OBSERVATION:
Attach the Self Generated Report with each task of the Project.
In each report following details should be there
1) Title Page
2) Table of Contents
3) Top project overview
4) Summary
5) Luminaries Details
6) Calculation Results
a) Filled ISO Contour
INSTRUCTION:
All the observation reports should be maintained in a separate file, do not staple with
the workbook.
- 27-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 08(b)
Department of Electrical Engineering
LAB SESSION 08(b)
Third Project on lighting design using CALCULUX
OBJECTIVE:
Design a task and accent lighting for an office.
The constructional details of the office are as under:
Room Specifications
Room dimensions
Width 3.50 m
Length 5.60 m
Height 2.70 m
Working Plane Height 0.80 m
Reflections
Ceiling 0.50
Walls 0.30
Floor 0.10
Position (of Left Front side of the room)
X 0.0
Y 0.0
Luminaries Used
TBS600/135 C7-60
MASTERLINE PLUS 20W 24D [13672]
Project Maintenance Factor 0.80
- 28-
Electrical Power Distribution & Utilization
Lab session 08(b)
Department of Electrical Engineering
-0.5
0
0.5
1
1.5
2
2.5
Y(m)
3
3.5
4
4.5
5
5.5
6
NED University of Engineering and Technology
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
X(m)
OBSERVATION:
Attach the Self Generated Report with each task of the Project.
In each report following details should be there
1) Title Page
2) Table of Contents
3) Top project overview
4) Summary
5) Luminaries Details
6) Calculation Results
a) Filled ISO Contour
INSTRUCTION:
All the observation reports should be maintained in a separate file, do not staple with the
workbook.
- 29-
Electrical Power Distribution & Utilization
Lab session 09
NED University of Engineering and Technology
Department of Electrical Engineering
LAB SESSION 09
Luminescence
OBJECTIVE
Verifying the Inverse Square Law and compare the difference in output luminescence of
incandescent, fluorescent and compact fluorescent lamps.
APPARATUS
A wooden board
Connecting wires
Fluorescent Light
Incandescent Light
LUX Meter
TYPES OF LAMPS
INVERSE SQUARE LAW
The inverse-square law, which states that the illuminance at a point on a surface
perpendicular to the light ray is equal to the luminous intensity of the source at that point
divided by the square of the distance between the source and the point of calculation.
E
I
D2
Where:
E = Illuminance in footcandles
I = Luminous intensity in candles
D = Distance in feet between the source and the point of calculation
INCANDESCENT LIGHT BULBS
Incandescent light bulbs consist of a glass enclosure (the envelope,
or bulb) which is filled with an inert gas to reduce evaporation of the
filament. Inside the bulb is a filament of tungsten wire, through
which an electric current is passed. The current heats the filament to
an extremely high temperature (typically 2000 K to 3300 K
depending on the filament type, shape, size, and amount of current
passed through). The heated filament emits light that approximates a
continuous spectrum. The useful part of the emitted energy is visible
light, but most energy is given off in the near-infrared wavelengths.
- 30-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 09
Department of Electrical Engineering
Figure: Types of Incandescent Lamps
FLOURESCENT TUBE LIGHT
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite
mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then
causes a phosphor to fluoresce, producing visible light.
Compared with incandescent lamps, fluorescent lamps use less power for the same amount of
light, generally last longer, but are bulkier, more complex, and more expensive than a
comparable incandescent lamp.
Figure: Types of Fluorescent Lamps
- 31-
Electrical Power Distribution & Utilization
Lab session 09
NED University of Engineering and Technology
Department of Electrical Engineering
COMPACT FLOURESCENT LIGHTS
A compact fluorescent lamp (CFL), also known as a compact
fluorescent light bulb (or less commonly as a compact fluorescent tube
[CFT]), is a type of fluorescent lamp. Many CFLs are designed to
replace an incandescent lamp and can fit in the existing light fixtures
formerly used for incandescent.
Compared to general service incandescent lamps giving the same
amount of visible light, CFLs use less power and have a longer rated
life, but generally have a higher purchase price.
PROCDUERE & CALCULATIONS
Place different lamps on the wooden board & calculate the LUX level at different point (Approx
Results only due to some unavoidable problems).
S. No.
1
2
3
1
2
3
1
2
3
Type of Lamp
Distance from
the source
LUX
Incandescent
Fluorescent Lamp
Compact Fluorescent
Lamp
RESULT
On wooden board, make the circuitry of Fluorescent tube.
EXERCISE
Draw the circuit diagram of a fluorescent lamp showing fluorescent tube, ballast & starter.
- 32-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 10
Department of Electrical Engineering
LAB SESSION 10
Calculating the Total Cost in a Residential and
Commercial or Industrial Bill.
OBJECTIVE
You are given an Industrial or commercial Bill
Calculate the total energy cost of the utility bill.
Explain the terms used in the bill
Perform Exercise in the end of the Lab Session
Theory:
The rates of utility companies are based upon the following guidelines:
1. The amount of energy consumed [kW.h]
2. The demand rate at which energy is consumed [kW]
3. The power factor of the load.
The amount of energy consumed is measured by Energy meter and the demand of the system
during the demand interval is measured by Demand meter.
What is The Difference Between Demand and Consumption?
Demand is how much power you require at a single point in time, measured in
kilowatts (kW).
Consumption is how much energy you use over a period of time, measured in
kilowatt-hours (kWh).
Example: assume ten lights are turned on each with a 100-watt bulb. To accomplish
this, you must draw - or demand - 1,000 watts, or 1 kW of electricity from the power
grid. If you leave all ten lights on for two hours, you would consume 2 kWh of
electricity.
Demand Measurement
Demand varies by customer and month. To record demand, a special meter tracks the
flow of electricity to a facility over a period of time, usually 30-minute intervals.
Over the course of a month, the 30-minute interval with the highest demand is
recorded and reflected on a monthly bill.
Minimum Charges means a charge to recover the costs for providing customer service to
consumers even if no energy is consumed during the month.
Fixed Charges means the part of sale rate in a two-part tariff to be recovered on the basis of
Billing Demand in kilowatt on monthly basis.
Variable Charge means the sale rate per kilowatt-hour (kWh) as a single rate or part of a
two-part tariff applicable to the actual kWh consumed by the consumer during a billing
period.
Maximum Demand where applicable , means the maximum of the demand obtained in any
month measured over successive periods each of 30 minutes duration.
- 33-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 10
Department of Electrical Engineering
Sanctioned Load where applicable means the installed load in kilowatt as applied for by the
consumer and allowed/authorized by the Company for usage by the consumer.
Power Factor shall be to the ratio of kWh to KVAh recorded during the month or the ratio of
kWh to the square root of sum of square of kWh and kVARh,.
Formulae to be used:
1. Energy Charges (Rs) = No. of Units x energy charges (Rs/kWh)
2. Fuel Adjustment Charges (Rs) = No. of Units x energy charges (Rs/kWh)
3. Fixed Charges (Rs)
If MXD>50% of connected load
then
Fix Charges (Rs) = Fix charges rates x MXD
If MXD<50% of connected load
then
Fix Charges (Rs) = Fix charges rates x 50% of connected load
4. Additional Surcharge
Additional Surcharge (Rs) = No. of Units x Additional surcharge (Rs/kWh)
5. Income Tax
Applicable on Taxable Amount
Taxable Amount = Energy Charges + Fuel Adjustment Charges + Additional Surcharge +
Fixed Charges + Electricty Duty + Meter Rent + P.f Penalty
6. Sales Tax
Sales Tax = some percent of Taxable amount (See Tarrifs)
- 34-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 10
Department of Electrical Engineering
EXERCISE:
Attach the bill here:
- 35-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 10
Department of Electrical Engineering
Calculations:
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
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- 36-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 11
Department of Electrical Engineering
LAB SESSION 11
Diesel Generating Set
OBJECTIVE
To study the various components of a Diesel Generating Set
THEORY
It is common practice to provide the standby emergency source of supply at all important
installations such as large factories, railways, airports & other essential services. This is
usually achieved with the use of a captive Diesel Generator Set (DG Set).
Main Components of A Diesel Generating Set
DG Set comprises of three main parts.
Engine
This is the main prime mover (PM) for the generator and may be a gas, petrol or diesel
engine, depending upon the availability of fuel. In this LAB we will discuss the Diesel
generating Set, being used more commonly for captive power generation.
The control of power output is obtained through this PM only. It has a drooping
characteristic.
Governor
This senses the speed of the machine and performs extremely fast and accurate adjustments in
the fuel supply to the PM. In turn it regulates the speed and output of the PM within
predefined limits, depending upon the droop of the PM. The governor may be a mechanical
(manual), hydraulic or electronic (automatic) device.
Generator
Generator is responsible for changing engine power (hp or kW) into electrical power (kVA).
They also must satisfy high magnetizing current draws (kVAR) of electrical equipment.
NEMA suggests 0.8pf for standard generator.
Engine & Generator Sizing
Engines are sized according to the actual power in kW required to meet the need of the
facility. The generator on the other hand, must be capable of handling the maximum apparent
power which is measured in kVA. Thus engine provide power (kW) and frequency control,
generator influence kVA and voltage control.
- 37-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 11
Department of Electrical Engineering
Fig: A Complete DG Set
Fig: Auxiliary Fuel Tank
- 38-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 11
Department of Electrical Engineering
Fig: A front View of a Diesel Generating Set
Fig: Batteries & Battery Charger
Fig: Air Ducting
- 39-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 11
Department of Electrical Engineering
Fig: Batteries
Fig: Vibration Isolator
EXERCISE:
Household Equipments Ratings:
Fill the following table;
S. No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Item
Ceiling Fan
Computer Monitor (Size= inches)
Refrigerator
Split AC (1 ton)
Split AC (1.5 ton)
Window Type Split AC (1 ton)
Window Type Split AC (1.5 ton)
Washing Machine
Electric Iron
Microwave Oven
Television (Size = inches)
Available Fluorescent Tubes
Available CFL
Printer (Laser jet or dot matrix)
Tape Recorder
Rating (kW)
This chart is very useful in calculating the size of the generator required for your home.
Question:
Explain the following parts or terms of Diesel Generating Set:
1. Radiators
2. Fuel Tank & Base Frame
3. Canopy
4. Main Tank & Auxiliary Tank
5. Silencer & Exhaust System
6. Drain Valve & Shut-off Valve
7. Shock Vibrators
8. BHP
9. Ducting
10. Standby, Prime & Continuous Ratings
11. Batteries & Battery Chargers
12. Generator Amperage
13. Crank
14. Blower Fan
- 40-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 12
Department of Electrical Engineering
LAB SESSION 12
Home Electrical Wiring
OBJECTIVE
To make connections in home electrical wiring from services main to different
distribution boards and electrical points for appliances in a room.
APPARATUS
A large wooden board
Kilo Watt-hour Meter
Wires & Cables
Switches & Sockets
Bulbs & Fans
THEORY
Designing the home electrical wiring needs careful consideration because of safety.
For wiring in residential buildings or industrial buildings, wiring layout should be first
prepared on the drawing board.
The number of light and power points in a building is determined not only by its size,
but is also a matter of individual preference especially in the case of residential
buildings and as such the owner should be consulted for this.
The number of outlets should be adequate to ensure convenient hooking up of the
various electric operated gadgets & appliances. Minimum four outlets one per wall
should be provided in each room. Lamps & motors should normally be wires on
different circuits.
Figure: Typical Domestic Intake Arrangement
- 41-
Electrical Power Distribution & Utilization
Lab session 12
NED University of Engineering and Technology
Department of Electrical Engineering
EXERCISE
Make connection of the three phase watt hour meter with the service main and
distribute the three-phase incoming service main & neural wire to different
distribution boards & electrical points (for appliances) in different rooms of
the house.
Select cables for them.
Measure the total energy.
Also draw the circuit diagram on AUTOCAD using the standard symbols of
switch fan bulb etc.
R
Y
B
N
R+N
KWh
Meter
ROOM NO. 01
ROOM NO. 02
Wash
Room
Wash
Room
Y+N
B+N
Yellow Phase
Blue Phase
ROOM NO. 04
ROOM NO. 03
Wash
Room
Wash
Room
In Room 1,2,3 &4
1 Tube Light is there on any one of the walls.
1 Ceiling fan is there.
1 DB is there (with three switches & one socket).
In each washroom,
Only one light is there, controlled from outside the washroom.
Red Phase is feeding Room 1 & Room 2; Yellow Phase is feeding Room 3, while
Blue Phase is feeding Room 4.
- 42-
Electrical Power Distribution & Utilization
Lab session 12
NED University of Engineering and Technology
Department of Electrical Engineering
On AutoCAD/Microsoft Visio, draw the SLD of your house showing
Electrical & Civil work (Stairs, Rooms, Kitchen etc).
Make an extension board with & without fuse with three sockets & one switch
in it and show the wiring diagram with color pencil.
1
SWITCH
2
3
SOCKETS
Phase Neutral
1
2
5A
FUSE
SWITCH
SOCKETS
Phase Neutral
- 43-
3
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 13
Department of Electrical Engineering
LAB SESSION 13
Earthing
OBJECTIVE
To measure Earthing Resistance and Soil resistivity.
APPARATUS
Earth Resistance Tester
Hammer
Measuring Tape
THEORY
Earthing provides protection to personnel and equipment by ensuring operation of protective
control gear and isolation of the faulted circuit in the following cases.
Insulation puncture or failure
Breakdown of insulation between primary & secondary windings of a transformer.
Lighting stroke
Ensuring low earth resistance is important in earthing
process. In case where protection against the faulted list is
provided by mean of fuse or a circuit breaker, the total
resistance of the earth path must be low enough to enable the
operation of the protective device.
The earth electrode resistance depends upon the electrical
resistivity of the soil in which the electrode is installed,
which in turn is determined by the following factors:
1. Nature of soil
2. Extent of moisture
3. Presence of suitable salts dissolved in moisture.
TYPES OF EARTH ELECTRODES
Rod & Pipe Electrodes
Plate Electrodes
Strip or Round Conductor Electrodes
Plate Electrodes:
Plate electrodes consist of copper, cast iron or steel plate.
The minimum thickness of plate is recommended as
For cast iron
12mm
For GI or steel
6.3mm
For Copper
3.15mm
And size not less than 600mm x 600mm.
- 44-
Electrical Power Distribution & Utilization
Lab session 13
NED University of Engineering and Technology
Department of Electrical Engineering
Figure: A typical layout of Plate Electrode
The approximate resistance to ground in a uniform soil can be expressed by
R
4
2A
where p = resistivity of soil, considered uniform in
A= area of each side of the plate in m2
m.
Rod & Pipe Electrodes:
This type of earthing is more suited for a soil possessing high resistivity and the electrode is
required to be longer & driven deeper into the soil to obtain a lower resistance to ground.
The diameter, thickness and length of the pipe is recommended as follows:
Cast iron (CI) pipes - 100mm (internal diameter), 2.5 to 3 m (long), 13mm
thick.
MS pipes
- 38 to 50mm (internal diameter), 2.5 to 3 m (long),
13mm thick
Copper
-13,16 or 19mm diameter, 1.22 to 2.44m long.
- 45-
Electrical Power Distribution & Utilization
Lab session 13
NED University of Engineering and Technology
Department of Electrical Engineering
Figure: A typical arrangement of pipe electrode grounding
In this case, the approximate resistance to ground in a uniform soil can be expressed by:
R
where
R= Resistance in
l = length of pipe in cm
d = internal diameter of pipe in cm
Resistivity of Soil:
Type of soil
1.
Wet organic soil
2.
Moist Soil
3.
Dry Soil
4.
Bed rock
100
8l
ln
1
2* * L
d
Average resistivity( )
10
100
1000
10000
It has been found that the resistivity of the soil can be reduces by a chemical treatment with
the following salts.
Economical and most
Normal Salt (NaCl) and a mixture of salt & soft coke.
commonly used salts
MgSO4
CuSO4
- 46-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 13
Department of Electrical Engineering
CaCl2
Na2CO3
More common salts
Usually the mixture of NaNo3 + sea salt + coal is used in the ratio of 1:3:5
MEASURING THE SOIL RESISTIVITY:
Soil resistivity is the key factor that determines what the resistance of a grounding electrode
will be, and to what depth it must be driven to obtain low ground resistance. The resistivity of
the soil varies widely throughout the world and changes seasonally. Soil resistivity is
determined largely by its content of electrolytes, which consist of moisture, minerals and
dissolved salts. A dry soil has high resistivity if it contains no soluble salts (Figuer 1).
4 POLE METHOD
A simple way to measure the resistivity of soil is a four-pin method in which four probes are
drilled into the ground along a straight line at equal distances a and depth b. Then a voltage V
is applied to the two inner probes and a current, If, is measured in the two outer probes
(Figure 22.16). This test can also be conducted with the help of a ground tester as discussed
in Section 22.3, which normally also has a provision for this test.
The formula for measuring soil resistivity is given below;
For accurate results b
Where:
a = distance between the electrodes in centimeters
- 47-
a
20
Electrical Power Distribution & Utilization
Lab session 13
NED University of Engineering and Technology
Department of Electrical Engineering
b = electrode depth in centimeters
= Soil resistivity (ohm-cm)
Since generally
a >> b (for accurate results keep b
a
)
20
2 aR g
For Example
After inspection, the area investigated has been narrowed down to a plot of ground
approximately 75 square feet (7 m2). Assume that you need to determine the resistivity at a
depth of 15 feet (450 cm). The distance A between the electrodes must then be equivalent
to the depth at which average resistivity is to be determined (15 ft, or 450 cm). Using the
more simplified Wenner formula (
2 aR g ), the electrode depth must then be 1/20th of
the electrode spacing or 8-7/8 (22.5 cm).
For example, if the reading is R = 15
= Soil resistivity (ohm-cm) = 6.28 x 15 x 450 = 42,390
-cm
OBSERVATION:
MEASURING SOIL RESISTIVITY
Length and Resistance of Wires
Red
(ft)
Green
(ft)
Blue
Black
Test 1:
Spacing Between the Rods = S =
Depth of Rods = 1/20 of S =
Value of Resistance Measured:
Calculated Value of Resistivity:
(ft)
(cm)
(ft)
Test 1:
Spacing Between the Rods = S =
Depth of Rods = 1/20 of S =
Value of Resistance Measured:
Calculated Value of Resistivity:
(ft)
(cm)
(ft)
Test 1:
Spacing Between the Rods = S =
Depth of Rods = 1/20 of S =
Value of Resistance Measured:
Calculated Value of Resistivity:
(ft)
(cm)
(ft)
- 48-
(ft)
(ft)
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 13
Department of Electrical Engineering
MEASURING THE GROUND RESISTANCE:
The resistance of a grounding station can be measured with the help of a ground tester, which
generates a constant voltage for accurate measurement. The tester has two potential and one
current probe. The procedure of measurement is illustrated in Figure.
Measuring the ground resistance with the
help of a ground tester
Measuring the ground resistance with the
help of an ammeter and a voltmeter
3 POLE METHOD
The method for measuring earthing resistance is given below.
One of the potential probes A is drilled into the ground at about 15 m from the grounding
station G, whose resistance is to be measured. The second probe B is placed between the two.
The current lead of the meter is connected to the grounding station. The meter will indicate
some resistance, which may be noted. Two more readings are also taken by shifting the
centre probe B by almost 3 m on either side of the original location. For an accurate due of
the ground resistance, the values obtained must be same. If they are not, the probe B is still
within the resistance area of the grounding station G. Shift away probe A by another 6 m or
so and place probe B between G and A, and repeat the test. If the three readings are now the
same, consider this as the actual ground resistance of station G, otherwise shift probe A
farther away until a constant reading is obtained.
Effect of Ground Electrode Size and Depth on Resistance
Size: Increasing the diameter of the rod does not materially reduce its resistance. Doubling
the diameter reduces resistance by less than 10%.
Depth: As a ground rod is driven deeper into the earth, its resistance is substantially reduced.
In general, doubling the r od length reduces the resistance by an additional 40% (Figure 11).
The NEC (1987, 250-83-3) requires a minimum of 8 ft (2.4 m) to be in contact with the soil.
The most common is a 10 ft (3 m) cylindrical rod which meets the NEC code. A minimum
diameter of 5/8 inch (1.59 cm) is required for steel rods and 1/2 inch (1.27 cm) for copper or
copper clad steel rods (NEC 1987, 250-83-2). Minimum practical diameters for driving
limitations for 10 ft (3 m) rods are:
1/2 inch (1.27 cm) in average soil
5/8 inch (1.59 cm) in moist soil
3/4 inch (1.91 cm) in hard soil or more than 10 ft driving depths
- 49-
Electrical Power Distribution & Utilization
NED University of Engineering and Technology
Lab session 13
Department of Electrical Engineering
MEASURING EARTH RESISTANCE
Length and Resistance of Wires
Red
(ft)
Green
(ft)
Blue
Black
Test 1:
Depth of Rod =
Distance of Current Electrode =
Distance of Voltage Electrode =
(cm)
(ft)
(ft)
Color of Wire Used=
Color of Wire Used=
(cm)
(ft)
(ft)
Color of Wire Used=
Color of Wire Used=
(cm)
(ft)
(ft)
Color of Wire Used=
Color of Wire Used=
Value of Resistance Measured:
Test 2:
Depth of Rod =
Distance of Current Electrode =
Distance of Voltage Electrode =
Value of Resistance Measured:
Test 3:
Depth of Rod =
Distance of Current Electrode =
Distance of Voltage Electrode =
Value of Resistance Measured:
RESULT
Earthing process has fully understood.
- 50-
(ft)
(ft)