Report(GIT)

GIT, EMP (PVT) LTD

NDES, EP/08/7102 Page 1

FREFACE

This report is based on Industrial training undergone from 01/04/2011 at

Electro Metel Pressing (Pvt).LTD , Panagoda , as the General Industrial Training .

According to the Training Programmed I had the Opportunity of having

an excellent training knowledge about panel board wiring ( power & control wiring) . The

report gives a brief description of working gained an also includes the relevant theoretical

facts earned during my training period.

From: To:

EMP (PVT) LTD 01/04/2011 01/02/2012

K.V.C.H KUMARA

EP/08/7102

NATIONAL DIPLOMA IN ENGINEERING SCIENCES

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ACKNOLEDGEMENT

Many great People contributed to success my general industrial training. So I should express my heartiest thanks for all of them.

Firstly I would like to thanks the principal, the deputy principal, lectures & all of staff members of IET for their valuable guidance.

My special thanks go to Mr.M.W.W.Weerarathna (Electrical training HOD in IET) for giving me valuable advices.

I would like to thanks this is a great event to after my thanks to the members of the final Inspection section (Testing Department) regarding help which I received from them during my training period.

I am grateful to the Mr. Thusitha Gnasekara , Head of Electrical , all other engineers & all other staff of the Electrical Department for their willing encouragement and valuable guide & help of at all times.

I would like to thanks Mr. Chandrananda Diyunuge , Chairmen of EMP group of companies , Mr. T Suresh kumara, Managing Director of EMP group of companies & Mr. Chandima hevanadugala, AGM of EMP (Pvt) Ltd and their staff.

Finally I should Thanks to my family members & my friend to support me & All the others who gave a helping hand in numerous ways to make this a success.

K.V.C.H .Kumara

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Contents - Part a (industrial training report)

Chapter 01 - Introduction of Establishment

1.1 EMP Group of companies 09.

1.1.1 EMP (PVT) LTD. 09.

1.1.2 Range of service of other members 10

1.2 The vision & mission 11

1.3 Organization chart of EMP (PVT) LTD 12

1.4 Organization chart of electrical assembly section 13

1.5 Logo 14

Chapter 02 - Protective Function

2.1 Circuit Breakers 16

2.1.1 Operation of circuit breakers 16

2.2 type of circuit breakers 17

2.2.1 Miniature circuit breakers 18

2.2.1.1 Tripping curves 19

2.2.2 Molded case circuit breakers 20

2.2.2.1 Technical data of MCCB 21

2.2.2.2 Tripping accessories of MCCB 22

2.2.3 ELCB &RCCB 24

2.2.4 Air circuit breakers 26

2.3 Need for circuit protection 27

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2.3.1 Current & Temperature 27

2.3.2 Overloads 28

2.3.3 Short circuit 29

Chapter 03 - Control Component

3.1 Introduction 32

3.2 ELR 32

3.2.1 Connection diagram of ELR 33

3.2.2 Application 34

3.3 EFR 35

3.3.1 Connection diagram of EFR 35

3.4 PFR 37

3.4.1 Connection diagram with UVT 40

3.4.2 Connection diagram with shunt 41

3.5 Relays 42

3.6 Timers 44

Chapter 04 - Protective Devices

4.1 Surge arrestors 46

4.1.2 Operating Terminology 48

4.2 Lighting rods 50

4.2.1 Introduction 50

4.2.2 Installation of lightning rod 51

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4.2.3 Grounding 52

4.3 Earthing system 52

4.3.1 System classification 53

4.3.1.1 TN network 54

4.3.1.2 TT system 56

4.3.1.3 IT system 57

Chapter 05 - Cables & Lugs

5.1 Introduction 59

5.2 cable Specification 59

5.2.1 Cable structure 60

5.2.2 Current rating of cable 63

5.3 Color code of cable 65

5.4 Voltage drop 65

5.4.1 Derating factors 66

5.4.2 Steps of calculating the cable for given load 67

5.5 Cable Laying 67

5.5 Bimetal lugs 68

Chapter 06 - Bus Bars

6.1 Introduction 71

6.2 Current rating of bus bars 72

6.3 Common bus bars 73

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Chapter 07 - Panel Board & Panel Test

7.1 introduction 75

7.2 IP Protection of a panel 76

7.3 Panel Testing 80

7.4 Testing equipment 81

7.4.1 Test bench 81

7.4.2 Primary injector 82

7.4.3 Clip on ammeter 83

7.4.4 High voltage insulation tester 85

Chapter 08 - Motor starters & ATS panel

8.1 motor starter panel 88

8.1.1 DOL starter 88

8.1.2 Star – delta starter 89

8.1.3 Auto transformer panel 92

8.2 ATS panel 95

Chapter 09 - Capacitor Bank

9.1 Design 99

9.2 Uses of HRC fuse 101

9.3 Uses of capacitor contactor 102

9.4 calculation of size of capacitor bank 102

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Part b – Presentation

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Chapter 01

Introduction of Establishment

1.1 EMP Group of companies

1.2 The Vision & Mission

1.3 Organization Chart of EMP (Pvt) Ltd

1.4 Organization Structure of Electrical Assembly Section

1.5 Logo

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1.1 EMP Group of companies

EMP Group of Companies was found in Templeburge industrial

Estate in 1992 and it was first known as Electro Metal Pressings (PVT) LTD. In year 2002

it was taken Over by present management and on 28th July 2006 it was incorporated as

EMP Group Of Companies. Today EMP is a group with 6 members which are spreading

their Hands all over the business and manufacturing world. The groups of members are

as follows.

Electro Metal Pressings (PVT) LTD (EMP)

EMP Projects Lanka (PVT) LTD (EPL)

EMP Engineering (PVT) LTD

AKLAN (PVT) LTD

EMP PVC (PVT) LTD

OMATA Water Management (PVT) LTD

SENAS plywood (PVT) LTD

1.1.1 Electro Metal Pressings (PVT) LTD

Electro Metal Pressing (Pvt) Ltd is establish in 1992 in sri lanka as a leading

panel fabricating, assembling & contracting company in the field of Electrical

Engineering.

They at their company will keep eye from initial stages to final stages, so that their

customers can be satisfied. They also consider time management so that their product is

can be delivered to their customers in time, Quality, Safety, and Reliability is their first

priority.

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Today, EMP manufactures switch boards up to 6000A to IEC 439-1 standards,

custom designed products for electrical installations made in compliance with

international standards; in addition company also manufacture and install high quality

low voltage and medium voltage Distribution switchboards, motor control panels,

control panels, reactive power compensation capacitor banks, cable ladders, trays &

trunking’s, sub distribution panels. This has gained a reputation in the industry as a

company that caters to the demands of commercial and industrial installation.

1.1.2 Range of service of other members

Among other companies, AKLAN is the sole agent for LS Industrial Systems

which Manufactures & distributes all type of circuit breakers, PLC control units,

and Electronic equipments all over the world. EMP PVC manufactures quality conduits &

PVC Pipes in mass scale. OMATA designs the water management systems &

provides ideal solutions for the market. SENAS plywood manufactures plywood

Boards to the Sri Lankan market.

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1.2 The Vision & Mission

Vision

To provide total solution in the

Engineering & construction industry in compliance

With evolving international standards

Mission

In keeping with the commitment to

Continuous improvement of our engineering products,

To deliver high quality & gain fulfillment

Thru’ satisfaction

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1.3 Organization Chart of EMP (Pvt) Ltd

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1.4 Organization Structure of Electrical Assembly Section

HEAD OF SWITCH BOARD &

ASSEMBLING

ELECTRICAL ENGINEERS

QUALITY ASSURENCE OFFICER

DRAUGHTS MAN 01/02/03

ASSEMBLING

CHARGE HAND

LEADERS

TECHNITIONS TRAINEES

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1.5 Logo

Figure 1(a). Logo of EMP, EPL & EMP Engineering

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Chapter 02

Protective Function

2.1 Circuit Breakers

2.2 Type of Circuit Breakers

2.3 Need for Circuit Protection

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2.1 Circuit Breakers

A circuit breaker is an automatically operated electrical switch designed to

protect an electrical circuit from damage caused by overload or short circuit. Its basic

function is to detect a fault condition and, by interrupting continuity, to immediately

discontinue electrical flow. Unlike a fuse, which operates once and then has to be

replaced, a circuit breaker can be reset (either manually or automatically) to resume

normal operation.

2.1.1 Operation of Circuit Breakers

All circuit breakers have common features in their operation,

although details vary substantially depending on the voltage class, current rating and

type of the circuit breaker.

All circuit breaker perform the following functions

SENSE when an over current occurs

MEASURE the amount of over current

ACT by tripping the circuit breaker in a time frame necessary to prevent damage

to itself and the associate load cables

The circuit breaker must detect a fault condition; in low-voltage

circuit breakers this is usually done within the breaker enclosure. Circuit breakers for

large currents or high voltages are usually arranged with pilot devices to sense a fault

current and to operate the trip opening mechanism. The trip solenoid that releases the

latch is usually energized by a separate battery, although some high-voltage circuit

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Electrical_network

http://en.wikipedia.org/wiki/Overcurrent

http://en.wikipedia.org/wiki/Short_circuit

http://en.wikipedia.org/wiki/Fuse_%28electrical%29

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breakers are self-contained with current transformers, protection relays, and an internal

control power source.

Once a fault is detected, contacts within the circuit breaker must open to

interrupt the circuit; some mechanically-stored energy (using something such as springs

or compressed air) contained within the breaker is used to separate the contacts,

although some of the energy required may be obtained from the fault current itself.

Small circuit breakers may be manually operated; larger units have solenoids to trip the

mechanism, and electric motors to restore energy to the springs.

The circuit breaker contacts must carry the load current without excessive

heating, and must also withstand the heat of the arc produced when interrupting

(opening) the circuit. Contacts are made of copper or copper alloys, silver alloys, and

other highly conductive materials. Service life of the contacts is limited by the erosion of

contact material due to arcing while interrupting the current. Miniature and molded

case circuit breakers are usually discarded when the contacts have worn, but power

circuit breakers and high-voltage circuit breakers have replaceable contacts.

2.2 Type of Circuit Breakers

Circuit breakers can be categorized to several types.

MCB

MCCB

ELCB & RCCB

ACB

OCB

VCB

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Among above all types 1-4 types are commonly used.

2.2.1 Miniature Circuit Breaker (MCB)

MCB (Miniature Circuit Breaker) is a circuit breaker with optimum

protection facilities of over current and short circuit only. These are manufactured for

fault level of up to 10KA only with operating current range of 6 to 125 Amps (the

ranges are fixed). It is available as single pole, double pole, three pole, and four pole

MCB’s. These are used for smaller loads -electronic circuits, house wiring etc. As MCB

reacts for both over current & short circuit, it avoids over heating in case of excess

current & provides fire protection.

Figure 2 (a) single poles, double pole, and three pole mcb’s

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2.2.1.1 Tripping Curves

Every MCB have a specified tripping curve, B, C, D or sometimes very

specialized Curve that varies from MCB brand to brand (e.g. -: K & Z curves of ABB

breaker). B, C & D curves are defined in IEE regulations. The relationship between

current and tripping time is usually shown as a curve, known as the MCB's trip

characteristic. The most important curves are B, C and D.

Type B MCBs react quickly to overloads, and are set to trip when the current

passing through them is between 3 and 5 times the normal full load current. They are

Over current region

Short circuit region

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suitable for protecting incandescent lighting and socket-outlet circuits in

domestic and commercial environments (resistive loads), where there is little risk of

surges that could cause the MCB to trip.

Type C MCBs react more slowly, and are recommended for

applications involving inductive loads with high inrush currents, such as fluorescent

lighting installations.

Type C MCBs are set to trip at between 5 and 10 times the normal full

load current. This type is generally used.

Type D MCBs are slower still, and are set to trip at between 10 and 20

times the normal full load current. They are recommended only for circuits with very

high inrush currents, such as those feeding transformers and welding machines.

K curves can also be used for motors and transformers but have improved

thermal characteristics at 1.05 to 1.2 times the rated current. The Z curves provide

protection to semiconductors, with instantaneous trip values at two to three times

the rated current.

2.2.2 Molded Case Circuit Breakers (MCCB)

MCCB’s (Molded Case Circuit Breakers) are designed for protection of low

voltage distribution systems. They are suitable for application as main breakers & for

Protection of branch & feeder circuit & connected equipment. MCCB’s provide

Protection of short circuit & overload protection. For all circuit elements including

Cables, motors etc. They are designed for used in control centers, panel boards &

Switch boards. They suit the requirement of lighting distribution & other power

Circuits.

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Figure 2(b) MCCB’s

2.2.2.1 Technical Data of MCCB

It is vitally important to know the parameters of a MCCB that are essential

when we selecting a proper MCCB. All the technical data of a MCCB is printed in the face

Plate and it is vitally important to know the meanings of them.

Voltage Ratings of MCCB

a) Rated Operational Voltage (Ue) -:

The nominal line to line voltage of the system should not exceed Ue

b) Rated insulation Voltage (Ui) -:

The highest operating voltage that will not cause a dielectric strength

failure. The rated insulation voltage is used as a parameter for dielectric

strength tests. The rated insulation voltage must always be higher than

the rated operating voltage (Ue).

c) Rated Impulse Withstand Voltage (Uimp) -:

The voltage on which clearance distances are based. The value of transient

peak voltage the circuit breaker can withstand from switching surges or

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lighting strikes imposed on the supply .e.g. Uimp = 8kV, Tested at 8kV

peak with 1.2/50μs impulse wave.

Current Rating of MCCB

d) Rated Current (In) -:

The current which the circuit breaker will carry continuously under specified

conditions and on which the time/current characteristics are based. Unless

otherwise stated in is based on a reference ambient temperature of 30 degrees

centigrade.

e) Ultimate Breaking Capacity (Icu) -: The maximum fault current which can flow through without damaging the

equipment. The calculated prospective fault current at the incoming terminals of

the circuit breaker should not exceed Icu.

f) Service Breaking Capacity (Ics)-: The maximum level of fault current operation after which further service is

assured without loss of performance.

2.2.2.2 Tripping Accessories of MCCB

Unlike RCDs (Residual Current Devices) MCCB has a tripping method, which

can operates fully mechanically. Even though power is not supplied to the breaker, if it is

In one position it can be tripped using the trip button. But RCD cannot be tripped when

The power isn’t supplied as its tripping method works from residual current (through an

electrical signal mechanical system is energized). There is also a method to do the

Tripping function of a MCCB by using electrical signals (current). For this we have to

Use the tripping accessories, shunt coil & UVT coil which is normally mounted in the

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Right hand seat of the case of the MCCB. Protection relays are connected to these

Coils.

a) Shunt Trip -:

When a current passes through the shunt coil it passes tripping signal to the MCCB. In

the normal operation no current must be gone through shunt coil. If power flow

continuously through a shunt coil, it will burn. So current to the shunt coil

is supplies from outgoing of the breaker.

Figure2(c). Shunt coil

b) UVT Trip -:

When current doesn’t pass through the UVT coil it passes tripping signal to the MCCB. So

to switch on a breaker with UVT coil, the coil must be provided a voltage. So it must be

connected to the incoming of the breaker.

Figure2 (d). UVT Coil

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2.2.3 ELCB & RCCB

a) Earth Leakage Circuit Breaker (ELCB)

An Earth Leakage Circuit Breaker (ELCB) is a safety device used in electrical

installations with high earth impedance to prevent shock.

Many electrical installations have relatively high earth impedance. This may

be due to the use of a local earth rod (TT systems), or to dry local ground conditions.

These installations are dangerous and a safety risk if a live to earth fault

current flows. Because earth impedance is high,

not enough current exists to trip a fuse or circuit breaker, so the condition

persists un cleared indefinitely

The high impedance earth cannot keep the voltage of all exposed metal to a

safe voltage; all such metalwork may rise to close to live conductor voltage.

These dangers can be drastically reduced by the use of an ELCB or Residual-current

device (RCD).

There are two types of ELCB:

voltage operated and,

Current operated.

Voltage-operated ELCBs were introduced in the early 20th century, and provided a

major advance in safety for mains electrical supplies with inadequate earth impedance.

ELCBs have been in widespread use since then, and many are still in operation.

Current-operated ELCBs are generally known today as RCDs (residual current device).

These also protect against earth leakage, though the details and method of operation

are different.

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When the term ELCB is used it usually means a voltage-operated device. Similar devices

that are current operated are called Residual-current devices.

b) Residual Current Circuit Breaker – (RCCB)

Figure2 (e). Two pole & Three Pole RCCB

Commonly use for protection from electrical shocks. If 30mA (Mentioned allowable

difference) current deference In Live and Neutral lines It automatically Trips.

Incoming supply from above or below, To ensure proper test button functionality of

four-pole RCCBs operated as two-pole devices, connect terminals 5 and 7 or, as the case

may be, 6 and 8. In the case of a 3-phase circuit with Un 127/230 V (without neutral

conductor N) terminals 4 and 8 have to be bridged.

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2.2.4 Air Circuit Breakers (ACB)

ACB(air circuit breaker) is an electric protecting apparatus which is installed

between an electric source and load units in order to protect a load unit and a load line

from an abnormal current generated on an electric circuit and to perform distribution

function for changing the electric power line to another line. The electrical systems in

Residential, commercial and industrial applications usually include a panel board for

Receiving electrical power from a utility source.

The power is then routed through over current protection devices to

designated branch circuits supplying one or more loads. Electrical power distribution

systems and their components need protection from numerous types of malfunctions,

including over current conditions, overvoltage conditions, under voltage conditions,

reverse current flow, and unbalanced phase voltages. If a MCCB is used instead of an

ACB it is essential to connect protection relays to protect load from above malfunctions.

Generally ACB is available from 1200A to 6400A for low voltage applications.

Air circuit breakers include operating mechanisms that are mainly exposed

to the environment. Since the air circuit breakers are rated to carry several thousand

amperes of current continuously, the exposure to convection cooling air assists in

keeping the operating components within reasonable temperature limits. A typical air

circuit breaker comprises a component for connecting an electrical power source to

electrical power consumer or load. The component is referred to as a main contact

assembly. A main contact is typically either opened, interrupting a path for power to

travel from the source to the load, or closed, providing a path for power to travel from

the source to the load. In many air circuit breakers, the force necessary to open or close

the main contact assembly is provided by an arrangement of compression springs.

In many air circuit breakers, the mechanism for controlling the compression springs

Comprises a configuration of mechanical linkages between a latching shaft and an

Actuation device. The actuation device may be manually or electrically operated. In a

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Common construction of a low voltage air circuit breaker, the movable contact is

Mounted on a contact arm that is pivoted to open the contacts by a spring powered

Operating mechanism triggered by a trip unit responsive to an over current condition

In the protected circuit. Various accessory devices are used with such air circuit

Breakers to provide auxiliary function along with over current protection. One such

Accessory is the bell alarm accessory that provides local and remote indication as to

The occurrence of circuit interruption.

2.3 Need for Circuit Protection

2.3.1 Current and Temperature

Current flow in a conductor always generates heat. The greater the

current flow, the hotter the conductor. Excess heat is damaging to electrical

components and conductor insulation. For that reason, conductors have a rated

continuous current carrying capacity. Over current protection devices, such as circuit

breakers, are used to protect conductors from excessive current flow. These protective

devices are designed to keep the flow of current in a .circuit at a safe level to prevent

the circuit conductor’s from overheating.

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Excessive current is referred to as over current. The National Electrical Code

(NEC®) defines over current as any current in excess of the rated current of equipment or

the amp city of a conductor It may result from overload, short circuit, or ground fault

(Article. 00-Definitions).

2.3.2 Overloads

An overload occurs when too many devices are operated on a single

circuit, or a piece of electrical equipment is made to work harder than it is designed for

example, a motor rated for 10 amps may draw 20, 30, or more amps in an overload

condition. In the following illustration, a package has become jammed on a conveyor,

causing the motor to work harder and draw more current. Because the motor is drawing

more current, it heats up Damage will occur to the motor in a short time if the problem

is not corrected or the circuit is shut down by the over current protector.

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2.3.3 Short Circuits

When two bare conductors touch, either phase to phase or phase to

ground, a short circuit occurs. When a short circuit occurs, resistance drops to almost

zero. Short circuit current can be thousands of times higher than normal operating

current.

Ohm’s Law demonstrates the relationship of current, voltage, and

resistance. For .example, a 240 volt motor with 24 Ω of resistance would normally draw

10 amps of current.

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When a short circuit develops, resistance drops. If resistance drops to 24 milliohms,

current will be 1 0,000 amps.

The heat generated by this current will cause extensive damage to connected

equipment and conductors. This dangerous current must be interrupted immediately

when a short circuit occurs.

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Chapter 03

Control Component

3.1 Introduction

3.2 Earth Leakage Relay

3.3 Earth Fault Relay

3.4 Phase Failure Relay

3.5 Relays

3.6 Timers

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3.1 Introduction

When manufacturing a panel board it is essential to have some protective

methods other than breakers which provide additional protection to the panel board,

Equipments that are connected to the panel board and the user. For this case protective

Relays and other protective devices such as surge arresters and fuses can be used.

When considering about protective relays, it doesn’t act a protective function alone. It

Needs some tripping accessories mounted in a MCCB such as described in chapter

01, to provide the protective function. As panel board is the heart of the distribution

System of building it is vitally important to have protective methods.

3.2 Earth Leakage Relay

Figure3 (a). Earth leakage Relay with CBCT

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ELR (Earth Leakage Relay) ensures the protection of electrical

installations and person against direct and indirect contacts. ELR is designed on an

electronic basis, which ensures the monitoring of earth fault currents. When the fault

current rises above the selected level, the outputs of the product operate depending on

the relay selected, it can have either fixed or adjustable settings for selectivity purposes.

Both minimum leakage current and also the tripping current can be adjusted in an ELR.

This is an advantage of an ELR than a RCCB.

To operate an ELR it must be connected to a CBCT (Core Balance

Current Transformer).The function of an ELR is as follow (Figure 3.1). It is known that at

Any instant the vector sum of currents in 3 phase balanced supply is equal to zero.

So at normal condition, total vector sum of currents in four wires (3 phases and

Neutral) must be zero. So at normal conditions no current should be generating in the

CBCT. When a leakage happens then there will be a leakage current and ultimately

Vector sum of current through CBCT will not be equal to Zero and as a result of

That the current will be induced in the CBCT. This current provides a signal to ELR

And it begins to operate and closes its normally open contact. Then there will be a

Current through the shunt coil and then shunt coil passes a tripping signal to the

MCCB. (It is known that if there is a current through a shunt coil it will provide a

Tripping signal to a MCCB). ELR is used with MCCBs with current rating less than

250A.

3.2.1 Connection diagram of ELR

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3.2.2 Application

a) Generator control panel

b) Distribution control Panel

c) Protection Systems

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3.3 Earth Fault Relay

Figure 3(b). EFR

EFR (Earth Fault Relay) is used for protecting from earth faults and use with

MCCBs with current rating greater than 250A. The function of EFR is as same as ELR, but

More sensitive than ELR. Instead of a CBCT, four separate CT’s are used to connect An

EFR. It is an Electronic Trip Unit, designed to protect the Electrical installation in Case of

faults or leakage currents beyond a preset level. The trip delay is adjustable.

3.3.1 Connection diagram of EFR

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Figure3(c).EFR connection diagram

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3.4 Phase Failure Relay

Figure 3(d).PFR

When we design power panels it is essential to protect circuit from

unhealthiness of power supply. In 3-phase systems there should protection from phase

failures so that Phase Failure Relays (PFR) are used, in here we discussed how PFR works

with the three phase motor.

If, for any reason, the motor windings draw more current than they are rated for,

excess heat is generated, causing deterioration of the motor insulation. This

deterioration is irreversible and cumulative. Eventually, the windings will short to the

motor housing, causing motor failure. The reaction time of thermal overload units may

be too slow to provide effective protection from the excess heat generated by high

current. A phase failure relay, by limiting the over current will help to:

Increase motor life

Reduce the very costly repair or replacement of motors

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Minimize downtime due to motor problems

Reduce the risk of electric shock or fire due to the shorting out of motor windings

Phase Failure Detection

A phase failure may occur because of a blown fuse in some part of

the power distribution system, a mechanical failure within the switching equipment, or

if one of the power lines open. A three-phase motor running on single phase draws all of

its current from the remaining two lines. Attempting to start a three-phase motor on

single phase will cause the motor to draw locked rotor current and the motor will not

start. The reaction time of thermal overload units may be too slow to provide effective

protection from the excessive heat generated in the motor windings when a phase

failure occurs.

Protecting a three-phase motor against phase failure is difficult because a

lightly loaded three phase motor operating only on single phase will generate a voltage,

often called regenerated voltage or back EMF, in its open winding almost equal to the

lost voltage. Therefore, voltage sensing devices which monitor only the voltage

magnitude may not provide complete protection from a phase failure which occurs

when the motor is running. A greater degree of protection can be obtained from a

device which can detect the phase angle displacement accompanying a phase failure.

Under normal conditions, the three- phase voltages are 120 degrees out of phase with

respect to one another. A phase failure will cause a phase angle displacement away from

the normal 120 degrees.

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Phase Reversal Detection

Phase reversal can occur when maintenance is performed on motor-

driven machinery, when modifications are made to the power distribution system, or

when power restoration results in a different phase sequence than before the power

outage. Phase reversal detection is important if a motor running in reverse may damage

the driven machinery or injure personnel. The National Electric Code (NEC) requires

phase reversal protection on all equipment transporting people, such as escalators or

elevators.

Voltage Unbalance Detection

Voltage unbalance can occur when incoming line voltages delivered by

the power company are of different levels, or when single-phase loads such as lighting,

electrical outlets and single-phase motors are connected on individual phases and not

distributed in a balanced way. In either case, a current unbalance will result on the

system which shortens motor life and diminishes motor efficiency. An unbalanced

voltage applied to a three-phase motor can result in a current unbalance in the motor

windings equal to several times the voltage unbalance. This will increase the heat

generated, a major cause of rapid deterioration of motor insulation.

Under voltage

Under voltage may occur if the power supplied by the local power

company is overloaded, causing the voltage to drop, which is known as a brown out. An

under voltage condition can also occur in remote areas at the end of long power lines.

As the voltage available to the motor is decreased, the current drawn by the motor

increases, resulting in generated heat which deteriorates the motor insulation.

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3.4.1 Connection Diagram with UVT coil

Figure 3(e) PFR with UVT coil

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3.4.2. Connection Diagram with shunt coil

Figure3(f). PFR with shunt coil

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3.5 Relays

A relay is an electrical switch that opens and closes under the control of

another electrical circuit. In the original form, the switch is operated by an

electromagnet to open or close one or many sets of contacts.

Figure 3 (g). Parts of a relay

Relays are widely used in control circuits. They are used for

switching multiple control circuits, and for controlling light loads such as starting coils,

indicator lights, and audible alarms. The operation of a control relay is similar to a

contactor. When power is applied from the control circuit, an electromagnetic coil is

energized. The electromagnetic field pulls the armature and movable contacts toward

the electromagnet closing the contacts.

When power is removed, spring tension pushes the armature and movable

contacts away from the electromagnet, opening the contacts. A relay can contain

normally open, normally closed, or both types of contacts. The main difference between

a control relay and a contactor is the size and number of contacts. The contacts in a

control relay are relatively small because they need to handle only the small currents

used in control circuits. There are no power contacts. Also, unlike a contactor, each

contact in a control relay controls a different circuit. In a contactor, they all control the

Parts of a Relay

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starting and stopping of the motor. Some relays have a greater number of contacts than

are found in the typical contactor.

Figure 3(h). Inside view of relay

Contact Point of 14 pin Relay

NO NC NO NC NO NC NO NC

Common Point

NO – Normally Open Contact Point

NC – Normally Closed Contact point

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3.6 Timers

Figure 3 (i). Timers

A time relay has two major functions: On-delay and Off-delay timing.

On-delay and Off delay timers can turn their connected loads on or off, based on

how the timer’s output is wired into the circuit. On-delay indicates that once a timer has

received a signal to turn on, a predetermined time (set by the timer) must pass before

the timer’s contacts change state.

Off-delay indicates that once a timer has received a signal to turn off, a

predetermined time (set by the timer) must pass before the timer’s contacts change

state.

Figure 3(j) Symbol of off & on delay Timer

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Chapter 04

Protective Devices

4.1 Surge Arrestors

4.2 Lighting Rods

4.3 Earthing System

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4.1 Surge Arrestors

Figure 4(a). Surge Arrestor

4.1.1. Introductions

The original lightning arrester was nothing more than a spark air gap with

one side connected to a line conductor and the other side connected to earth ground.

When the line-to-ground voltage reached the spark-over level, the voltage surge would

be discharged to earth ground.

The modern metal oxide arrester provides both excellent protective

characteristics and temporary overvoltage capability. The metal oxide disks maintain a

stable characteristic and sufficient non-linearity and do not require series gaps.

Due to the broad nature of this subject, this paper will concentrate on the application of

the gapless metal oxide arrester to circuits and systems rated 1000 V and greater.

The lightning arresters and ground wires can well protect the electrical

system against direct lightning strokes but they fail to provide protection against

travelling waves, which may reach the terminal apparatus. The surge arresters or surge

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diverters provide protection against such surges. A lightning arrester or a surge diverter

is a protective device, which conducts the high voltage surges on the power system to

the ground.

Surge protection of electrical equipment is a very important part of the

electrical system design.

Lightning strikes are not the only sources of voltage surges in the

electrical system. The following are a few of the more frequently encountered causes of

transient voltage surges:

Surge voltages associated with switching capacitors

Surge voltages due to a failure in equipment insulation resulting in a short circuit

on the distribution system

Surge voltages associated with the discharge of lightning arresters at other

locations within the facility

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4.1.2 Operating Terminology

Generally Surge arrester is assembled at the incoming side of an every

main Distribution board. The construction concept of a surge arrester is as shown below.

Figure 4(b) - Construction Concept of a Surge Arrester Fig 4(b). (i) Shows the basic form of a surge arrester. It consists of a

spark gap in series with a non-linear resistor. One end of the arrester is connected to

the terminal of the equipment to be protected (generally a distribution board) and

the other end is effectively grounded. The length of the gap is so set that normal

voltage is not enough to cause an arc but a dangerously high voltage will break down

the air insulation and form an arc. The property of the non-linear resistance is that

its resistance increases as the voltage (or current) increases and vice-versa. This is

clear from the voltage current characteristic of the resistor shown in Fig 4(b)(ii).

Under normal operation, the lightning arrester is off i.e. it conducts

no current to earth or the gap is non-conducting. On the occurrence of over voltage,

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the air insulation across the gap breaks down and an arc is formed providing a low

resistance path for the surge to the ground. In this way, the excess charge on the line

due to the surge is harmlessly conducted through the arrester to the ground instead of

being sent back over the line. It is worthwhile to mention the function of non-linear

resistor in the operation of arrester. As the gap sparks over due to over voltage, the arc

would be short-circuited on the power system and may ground the surge. Since the

Characteristic of the resistor is to offer low resistance to high voltage (or current), it

gives the effect of short-circuit. After the surge is over, the resistor offers high resistance

to make the gap non-conducting.

But though a lightning has the strength about 200kA, generally a surge

arrester of 10kA is assembled in a main panel & 5kA for a branch panel for the

protection (or otherwise only one 20kA surge arrester for the main panel & no surge

arresters for branch panel). This is a contradiction. Let’s clear this, consider below figure.

Figure 4(c) - Anatomy of a Surge

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Suppose a surge of 210kA occurs on a 3 phase transmission line. Then for a

single phase the surge will be70kA. In the transmission line it can flow through both

Directions. So the surge for one side will be 35kA. The arrester of distribution

transformer then diverts about 20kA to the ground. When the rest of the surge,

15kA meets the main panel surge arrester, it will be diverted to the earth (if possible

Capacity of a surge arrester) or the rest part of the surge will be grounded by branch

Panel surge arresters.

4.2 Lighting Rods

4.2.1 Introduction

A lightning rod or lightning conductor is a metal rod or

conductor mounted on top of a building and electrically connected to the ground

through a wire, to protect the building in the event of lightning. If lightning strikes the

building it will preferentially strike the rod, and be conducted harmlessly to ground

through the wire, instead of passing through the building, where it could start a fire or

cause electrocution.

A lightning rod is a single component in a lightning protection system. In

addition to rods placed at regular intervals on the highest portions of a structure, a

lightning protection system typically includes a rooftop network of conductors, multiple

conductive paths from the roof to the ground, bonding connections to metallic objects

within the structure and a grounding network.

The rooftop lightning rod is a metal strip or rod, usually of copper or

aluminum. Lightning protection systems are installed on structures, trees, monuments,

bridges or water vessels to protect from lightning damage. Individual lightning rods are

sometimes called finials, air terminals or strike termination devices.

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Figure 4(d). Diagram of a simple lightning rod system

4.2.2. Installation of a lightning rod

The lightning rod must be installed in an appropriate angle to protect

the building. This protection angle varies according to the capacity of the lightning.

Generally, lightning arrester is fixed in a height that includes the building in 45 degrees

of angle. According to top area of the building multiple arresters may be used. Lightning

rods must be placed at regular intervals, preferably 20 feet apart, at most. The end rods

Should be installed within at least one foot of the end of the roof, though two feet, at

Most is acceptable. The most suitable, but most cost way of fixing over head shield is

The Faraday cage, copper plate net with 2x2 square feet squares. But as this is very

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High in cost, a copper tape is run around the top of the building & bottom of the

Building. Then these two rounds are connected with copper tape (by all four sides or

At least two sides).

4.2.3. Grounding After proper grounding is connected, the earth resistance must be smaller

than 10 ohms. Depending on the earth resistance numbers of grounding rods are varied.

At least 2 rods are grounded at a distance same as the depth of the rod for grounding.

Depending on the size of your house, at least 2 groundings will be needed. If the building

is larger in perimeter than 250 feet but less than 350, the building needs three

groundings. If the perimeter is between 350 and 450 feet, it needs four, and so on.

The groundings should be at opposite corners of the house, if possible. If the

copper rods are not enough for decreasing resistance then a copper plate have to be

used. It must be laid in the ground such that the copper plate will make 30 degrees angle

to vertical axis.

4.3 Earthing System

In an electricity supply systems, an earthing system defines the

electrical potential of the conductors relative to that of the Earth's conductive surface.

The choice of earthing system has implications for the safety and electromagnetic

compatibility of the power supply. Note that regulations for earthing (grounding)

systems vary considerably between different countries.

A protective earth (PE) connection ensures that all exposed conductive

surfaces are at the same electrical potential as the surface of the Earth, to avoid the risk

of electrical shock if a person touches a device in which an insulation fault has occurred.

It ensures that in the case of an insulation fault (a "short circuit"), a very high current

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flows, which will trigger an over current protection device (fuse, circuit breaker) that

disconnects the power supply.

A functional earth connection serves a purpose other than providing

protection against electrical shock. In contrast to a protective earth connection, a

functional earth connection may carry a current during the normal operation of a device.

Functional earth connections may be required by devices such as surge suppression and

electromagnetic-compatibility filters, some types of antennas and various measurement

instruments. Generally the protective earth is also used as a functional earth, though

this requires care in some situations.

4.3.1 System Classifications

The earthing system can be classified to following three system networks using the two-

letter codes.

a) TN System

b) TT System

c) IT System

The first letter indicates the connection between earth and the power-

supply equipment (generator or transformer):

T: direct connection of a point with earth

I: no point is connected with earth (isolation), except perhaps via high

impedance.

The second letter indicates the connection between earth and the electrical

device being supplied:

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T: direct connection with earth, independent of any other earth connection in

the supply system;

N: connection to earth via the supply network.

4.3.1.1 TN network

In a TN earthing system, one of the points in the generator or transformer

is connected with earth, usually the star point in a three-phase system. The body of the

electrical device is connected with earth via this earth connection at the transformer.

Figure 4(e) TN network

The conductor that connects the exposed metallic parts of the consumer is

called protective earth (PE). The conductor that connects to the star point in a three-

phase system, or that carries the return current in a single-phase system, is called

neutral (N).

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Three variants of TN systems are distinguished:

a) TN−S: PE and N are separate conductors that are connected together only near

the power source.

Figure 4(f). TN-S System

b) TN−C: A combined PEN conductor fulfills the functions of both a PE and an N

conductor.

Figure 4(g). TN-C System

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c) TN−C−S: Part of the system uses a combined PEN conductor, which is at some

point split up into separate PE and N lines. The combined PEN conductor typically

occurs between the substation and the entry point into the building, whereas

within the building separate PE and N conductors are used. In the UK, this system

is also known as protective multiple earthing (PME), because of the practice of

connecting the combined neutral-and-earth conductor to real earth at many

locations, to reduce the risk of broken neutrals - with a similar system in Australia

being designated as multiple earthed neutral (MEN).

Figure 4(h) TN−C−S System

4.3.1.2 TT System

In a TT earthing system, the protective earth connection of the

consumer is provided by a local connection to earth, independent of any earth

connection at the generator. (Using in Sri Lanka)

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Figure 4(i) TT System

4.3.1.3 IT System

In an IT network, the distribution system has no connection to earth at all,

or it has only a high impedance connection. In such systems, an insulation monitoring

device is used to monitor the impedance

Figure 4(j) IT System

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Chapter 05

Cables & Lugs

5.1 Introduction

5.2 Cable Specification

5.3 Color Code of Cable

5.4 Cable Selection (Voltage drop)

5.5 Cable Laying

5.6 Bimetal Lugs

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5.1 Introduction

In an electrical system, cables are used for carrying electrical currents.

Most times core of these cables are made of copper or Aluminum to conduct current

with minimum voltage drop. Most cables have a protective insulation to protect the

cable & also to protect living beings from dangerous voltages. Types of cables are differ

according to the,

Current go through (cable size)

Purpose they are used

Place (indoor or outdoor)

Protection level required

Etc.

Mainly the cable types can be categorized to below groups. General Cables (cables which are used for general purposes)

Flexible Cables

Aluminum Cables (Bare conductors)

Armored Cables

Unarmored Cables

Auto Cables

Coaxial Cables

Telecommunication Cables

5.2 Cable Specification

As previously said types of cables that are used is differs from various reasons.

Generally bare conductors are used for the transmission & distribution of low,

Medium & high voltage. Armored & unarmored cables are used for the distribution of

Electricity with in cities, factories & buildings. They are directly laid in ground where

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Excessive mechanical stresses likely to occur. Though the armored cables don’t need

Any excess protection, unarmored cables must be provided some additional protection.

Other major type of cable used in low voltage distribution in rural & semi urban areas

Is ABC (Arial Bundled Conductors) Cables. These are only few things about cables.

5.2.1 Cable Structure

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From above figures it can be seen that some cables are consists of

several strands. It can be observed that though the cables have same cross sectional

area if the number of strands of cable is higher than the other it can carries a larger

current than other one. This incident happens because of electrons. Normally charges

(here electrons) stays in the surface of any conductive element. The numbers of strands

are increased means that the surface area of the cable is increased. That means it can

take more electrons (current). So, than other cables of same size flexible cables can take

larger currents.

5.2.2. Current Rating of a Cable

Current ratings for wires differ from manufacturer to manufacturer, though

they are almost similar. Below shows the approximated current ratings for given wire

sizes under standard conditions.

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According to these current ratings appropriate earth cables have to be selected.

According to IEC regulations, selection of protective earth cable is as follows.

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5.3 Color Code of cables

OLD NEW

Red L1 Brown

Yellow L2 Black

Blue L3 Gray

Black N Blue

Green/Yellow PE Green/Yellow

5.4 Cable selection

According to voltage drop

In many instances this may well be the most onerous condition to affect cable

sizes. The Regulations require that the voltage at the terminals of fixed equipment

should be greater than the lower limit permitted by the British Standard for that

equipment, or in the absence of a British Standard, that the safe functioning of the

equipment should not be impaired. These requirements are fulfilled if the voltage drop

between the origin of the installation and any load point does not exceed the following

values (IEE Regulations) (Table 5a).

Accompanying the cable current rating tables are tabulated values of

voltage drop based on the mille-volts (mV) dropped for every ampere of design current

(A), for every meter of conductor length (m), i.e.

Volt drop = mV/A/m

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Table5a. Voltage Drop Values

Or fully translated with I b for A and L (length in meters):

5.4.1 Derating Factors

All the cables in the market are marked for a current that it can carry under

standard conditions. But always these standard conditions cannot be kept practically, in

a construction. So if a cable is selected according to the requirements (current)

according to our assemble method there can be variations of current. The factors that

are affecting for above variations are called as de rating factors. They are,

Ambient temperature

Ground temperature

Depth of lying

Soil Thermal resistivity

So if a cable is being selected, we must consider de rating factors which are

mentioned in cable catalogues.

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5.4.2 Steps of calculating the cable for given load

Let, we are given to calculate suitable cable size for a machine which have

known power consumption, Known input voltage. And also the distance from power

supply to load (L) is provided. Then,

Using the given data, calculate the load current I.

Select a wire that is a little bigger to carry I (I wire > I)

Then multiply the rated current of selected wire with all the de rating

factors.

Find whether,

I wire x de rating factors < I

If so select next bigger wire size. If not select that wire

Then calculate the voltage drop of wire & nominal voltage drop & see

whether it is ok.

5.5 Cable Laying

When a cable is being laid it is important, but generally forgotten factor is

cable bends. As per IEEE regulations according to cable diameter, the internal radii of

cable vary as follows.

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Table 5b. Cable Radiation(r) Variation with Cable Diameter (D)

5.6 Bimetal Lugs

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Whenever aluminum cable is to be terminated on copper bus bar or

copper contact, if aluminum lug is used then contact between terminal lug and copper

bus bar being of dissimilar metals, galvanic action takes place. Also if copper lug is used

then contact between aluminum cable and barrel of copper terminal lug is of dissimilar

metal and hence the galvanic action takes place. In order to prevent dissimilar contact

and to avoid galvanic action it is always advisable to use copper aluminum Bi-Metal lugs.

In Bi-Metal lugs barrel of the lug is of aluminum and the head or palm of the lug is of

Copper.

This ensures contact between aluminum cables to terminal lug is of

Aluminum and contact between terminal lug to copper bus bar or contact is of copper.

Thus contact between dissimilar metal is avoided and contact between similar metal is

Established. Thus Bi-Metallic or galvanic action is completely eliminated and hence

Durable joint is achieved.

Electrolytic copper head / palm is friction welded to electrolytic

aluminum barrel. At the interface, copper molecules and aluminum molecules

intermingles with each other and form durable bond. Similarly if aluminum cable is to be

joined with copper cable then Bi-Metal in line connectors are to be used. Here for

aluminum cable aluminum barrel is provided and for copper cable copper barrel is

provided. Copper and aluminum barrels are friction welded. Depending upon application

Bi-Metal terminals, in line connectors, pin type connectors etc are manufactured.

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Chapter 06

Bus Bars

6.1 Introduction

6.2 Current Rating of Cupper Bus Bars

6.3 Common Bus bars (using with mcb’s)

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6.1 Introduction

Figure 6(a) Bas bar set

A bus bar in electrical power distribution refers to thick strips of

copper or aluminum that conduct electricity within a switchboard, distribution board,

substation, or other electrical apparatus.

The size of the bus bar is important in determining the maximum amount of

current that can be safely carried. Bus bars can have a cross-sectional area of as little as

10 mm² but electrical substations may use metal tubes of 50 mm in diameter (1,000

mm²) or more as bus bars.

Bus bars are typically either flat strips or hollow tubes as these

shapes allow heat to dissipate more efficiently due to their high surface area to cross-

sectional area ratio. The skin effect makes 50-60 Hz AC bus bars more than about 8 mm

(1/3 in) thick inefficient, so hollow or flat shapes are prevalent in higher current

applications. A hollow section has higher stiffness than a solid rod, which allows a

greater span between bus bar supports in outdoor switchyards.

A bus bar may either be supported on insulators, or else insulation may

completely surround it. Bus bars are protected from accidental contact either by a metal

enclosure or by elevation out of normal reach. Neutral bus bars may also be insulated.

Earth bus bars are typically bolted directly onto any metal chassis of their enclosure. Bus

http://en.wikipedia.org/wiki/Image:Busbars.jpg

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bars may be enclosed in a metal housing, in the form of bus duct or bus way, segregated-

phase bus, or isolated-phase bus.

Bus bars may be connected to each other and to electrical apparatus by

bolted or clamp connections. Often joints between high-current bus sections have

matching surfaces that are silver-plated to reduce the contact resistance. At extra-high

voltages (more than 300 kV) in outdoor buses, corona around the connections becomes a

source of radio-frequency interference and power loss, so connection fittings designed

for these voltages are used.

6.2 Current Rating of Cupper Bus Bars

B.B. Size

(mm*mm)

Cross Section Area

(mm2)

Weight

Kg/m

Approximate AC rating

Approximate

Imperial Size free Air

(A)

Still Air (A)

20*10 25*10 30*10 40*10 50*10 60*10 80*10 100*10

20*6 25*6 30*6 40*6 50*6 60*6 80*6 100*6

200 250 300 400 500 600 800 1000

120 150 180 240 300 360 480 600

1.785 2.232 2.678 3.571 4.464 5.356 7.142 8.428

1.071 1.339 1.607 2.142 2.678 3.214 4.285 5.356

480 580 700 800 1060 1200 1525 1800

885 460 535 675 815 955 1220 1480

535 645 795 995 1200 1355 1735 2065

430 515 595 755 910 1065 1355 1670

3/4˝ x 3/8˝ 1˝ x 3/8˝ 1 ¼˝x 3/8˝ 1 ½ x 3/8˝ 2˝ x 3/8˝ 2 ½˝ x 3/8˝ 3˝ x 3/8 4˝ x 3/8˝

3/4˝ x 1/4˝ 1˝ x 1/4˝ 1 ¼˝ x 1/4˝ 1 ½˝ x 1/4˝ 2˝ x 1/4˝ 2 ½˝ x 1/4˝ 3˝ x 1/4˝ 4˝ x 1/4˝

Table 6a. Current rating of bus bars

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6.3 Common Bus bar (Using with mcb’s)

These types of Bus Bars are used to connect MCBs,

The advantages of this bus bar system are:

30% Installation time savings

Panel space savings

Reduced maintenance

High electrical ratings

Figure 6(b). Common bus bars

With Out Bus Bar System

hgshg

With Bus Bar System

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Chapter 07

Panel Board & Panel Test

7.1 Introduction

7.2 IP Protection of a panel

7.3 Panel Testing

7.4 Testing Equipment

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7.1 Introduction

A panel board (or distribution board) is a component of an electricity

supply system which divides an electrical power feed into subsidiary circuits, while

providing a protective fuse or circuit breaker for each circuit, in a common enclosure.

Normally, a main switch, and in recent boards, one or more Residual-current devices

(RCD) or Residual Current Breakers with Over current protection (RCBO), will also be

incorporated. Rather than providing separate protection systems, it is easier to use a

panel board.

The main advantage of a panel board is, all the outgoing power circuits &

incoming power can be controlled at a single location. Since panel boards are with

protection systems it supplies overall protection to its subsidiary circuits. When a

construction of a high rise building or a factory, it is easy to use panel boards & sub DB’s

& also panel boards provides high protection & neat electric work for the building.

Figure 7(a). Distribution System of a Four Story Building

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7.2 IP Protection (Ingress Protection) of a Panel A two-digit number established by the International Electro Technical

Commission is used to provide an Ingress Protection rating to a piece of electronic

equipment or to an enclosure for electronic equipment. The protection class after

EN60529 is indicated by short symbols that consist of the two code letters IP and a code

numeral for the amount of the protection. IP XX (e.g. – IP 54)

The two digits represent different forms of environmental influence:

The first digit represents protection against ingress of solid objects.

The second digit represents protection against ingress of liquids.

The larger value of each digit, the greater the protection. As an example, a

product rated IP54 would be better protected against environmental factors than

another similar product rated as IP42. IP rating tables are as below.

IP First number - Protection against solid objects

Table 7a IP First number - Protection against solid objects.

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IP Second Number – Protection against liquid

Table7b. IP Second Number – Protection against liquid According to above two charts it can be seen that there must be some ways

to increase the protection of a panel Board. They are,

Equal thickness of powder coating according to the standards – Insulate

enclosure to prevent hazards up to some level in case of a fault condition

Doors for panel boards with properly assembled & earthed

Cover plates which are tailor made for the panel – provides additional

Protection after door is opened

Insulation of the Bus bars & Perspex sheets – provides additional protection

After cover plates are removed

Panel earthling – to ground in case of fault current

Using glands in cable cable entries

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Figure 7(b) Panel board with cover Plate

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Figure 7(C) Panel inside view without cover plate

7.3 Panel Testing

After assembling the panel it comes to check the quality called panel testing.

Panel testing consist physical/Mechanical Tests and Electrical Tests, there are

Physical / Mechanical Tests

Looks -( Neat & Clean)

Firmness of terminal strips, terminals, and Holding bolts

Connections - Marking & Position

Labeling - Rating plate data shall be legible as specified

Overall dimension - As per customer's specs or our standard drawings

Proper arrangement of cables

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Electrical Tests

Continuity (use Clip on ammeter)

Proper working of switches, breakers, meters, indicators & act

Working of circuit is tested by using Load bank or current supply unit (such as

overload tripping, phase failure tripping & acts)

Meager Test

7.4 Testing Equipment

7.4.1 Test Bench

Figure 7(d) Test Bench

Can be used test bench for following Functions’

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Continuity test

Ammeter & KWH load test

Give a Supply for panels AC or DC

AC: 230v - 440v

DC: 12v- 48v

Can be give both CEB & Generator Supply at same time

Can be Measure panel voltage

7.4.2 Primary Injector

Figure 7(e). Primary Injector

Usage of Primary Injector

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Current Transformer Test

I. Polarity Test

II. Secondary current Test (against Primary Current)

Ammeter & KWH load test

MCB & MCCB load Test

EFR load Test

7.4.3 Clip on Ammeter

Figure 7(f) Clip on Ammeter

The digital clamp meters have a four digit L.C.D. and are available in

different versions for maximum currents of 200 A, 1000 A and 2000 A. They feature auto

ranging and auto-zeroing and can measure a.c., d.c., pulsed and mixed currents.

Additional functions include the measurement of voltage, resistance, continuity and a

diode test.

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The overall accuracy of 1,3% of the measured value has been achieved by utilizing the

latest microprocessor technology, plus the use of a true RMS measuring technique. This

accuracy even applies when harmonics or complex waveforms are present

The clamp meters have additional ranges of 400 V, 600 V, 400 Ω, 4 k Ω

and allow diode tests as well as continuity tests with an integrated buzzer. Simply by

pushing a button, it is possible to freeze the last value measured or to display the peak

value on the four digit 12 mm high liquid crystal display. The analogue outputs of this

can be connected to an oscilloscope, chart recorder, data logger or other

measuring/recording equipment. A true RMS output is also available.

The traditional measuring method for taking current

measurements by inserting a shunt resistor or a current transformer has inherent

disadvantages, such as the necessity to break the circuit conductor. The modern,

competitively priced Hall Effect clamp-on MultiMate’s offer the user many advantages

including the measurement of d.c. currents and non-sinusoidal waveforms.

The high accuracy current measurement capability and full multimeter

functionality of the series satisfy a wide range of applications in service, maintenance

and installation of machinery and industrial equipment. These battery powered

instruments can be used for automotive diagnostics and current measurements in

converter driven motors, current networks, electric vehicles, generators, switch mode

power supplies, power electronics, electroplating plants and welding equipment.

In addition they are suitable for measuring high-voltage currents and the ripple

on power supplies.

Typical application areas include the analysis of current distribution in

multiple grid systems, the determination of peak demand in current networks and the

measurement of the battery supply current in uninterruptible power supplies.

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The analogue output feature allows current waveforms to be displayed on an

oscilloscope and true RMS values of current to be recorded on a chart recorder.

7.4.4 High Voltage Insulation Tester

The traditional instrument became the industry standard 5

kV tester. It is battery-powered, housed in a rugged case and has a large, simple white-

on-black scale. These instruments show results and test options on a large, clear

analogue/digital scale for both practicality and precision. A built-in timer makes both

spot tests and PI testing easier to carry out. They are powered by a built-in rechargeable

lead-acid battery which can be charged directly from any supply from 95 V to 265 V. All

testers incorporate a guard terminal to allow surface leakage to be removed.

Pre-set standard test voltages at 500 V, 1000 V, 2500 V and 5000 V are

supplemented with a variable test voltage in 25 V steps. These top of the range units

also allow measurement of resistance to 5 TΩ, leakage current to 0,01 nA and can

display capacitance at the end of a test to 10 μF.

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This is designed for testing the insulation of high voltage electrical equipment

and the wide voltage range also allows it to be applied to low voltage equipment.

Generators, motors, transformers, cables and switchgear all require

effective maintenance and the test techniques on the Megger range give valuable

diagnostic information. ‘Spot’ Insulation tests that are the most widely used, check on

the general condition of electrical insulation, called up in most standards covering

equipment design, testing, installation and maintenance.

Insulation suffers from gradual steady decline, as well as occasional sudden

damage; the effects of dirt, grease, moisture, vibration and chemical attack can be

tracked through the recording of Polarization Index tests which remove the temperature

dependence of raw Insulation Resistance measurements.

For finding more localized insulation problems, some megger includes both Step

Voltage and Dielectric Discharge tests.

Step Voltage identifies local weak spots because they respond differently

as the electrical stress is increased, while the Dielectric Discharge test can show up a

single bad layer in multilayer insulation.

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Chapter 08

Motor Starters & ATS Panel

8.1 Motor Starter Panel

8.1.1 DOL Starter

8.1.2 Star-Delta Starter

8.1.3 Auto Transformer tarter

8.2 ATS Panel

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8.1 Motor Starter Panel

8.1.1 Direct on line starter (DOL) Starter

A direct on line (DOL) or across the line starter starts electric motors by

applying the full line voltage to the motor terminals. This is the simplest type of motor

starter. A DOL motor starter also contain protection devices, and in some cases,

condition monitoring. Smaller sizes of direct on-line starters are manually operated;

larger sizes use an electromechanical contactor (relay) to switch the motor circuit. Solid-

state direct on line starters also exist.

A direct on line starter can be used if the high inrush current of the

motor does not cause excessive voltage drop in the supply circuit. The maximum size of

a motor allowed on a direct on line starter may be limited by the supply utility for this

reason. For example, a utility may require rural customers to use reduced-voltage

starters for motors larger than 10 kW.

DOL starting is sometimes used to start small water pumps,

compressors, fans and conveyor belts. In the case of an asynchronous motor, such as the

3-phase squirrel-cage motor, the motor will draw a high starting current until it has run

up to full speed. This starting current is commonly around six times the full load current,

but may as high as 12 times the full load current. To reduce the inrush current, larger

motors will have reduced-voltage starters or variable speed drives in order to minimize

voltage dips to the power supply

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Figure 8(a). Power & Control Diagram of DOL Starter

8.1.2. Star Delta Starter

To decrease the starting current cage motors of medium and larger sizes

are started at a reduced supply voltage. The reduced supply voltage starting is applied in

the Star Delta methods. This is applicable to motors designed for delta connection in

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normal running conditions. Both ends of each phase of the stator winding are brought

out as six terminals. For starting, the stator windings are connected in star and when the

Machine is running the switch is thrown quickly to the running position by automatically

(It can be done manually also), thus connecting the motor in delta for Normal operation.

The power diagram of Star Delta starter is shown below.

Figure 8(b). Power circuit of star delta starter

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When the motor is started in the star connection, the phase voltage of

the motor is reduced by a factor of √3. The starting line current of the motor will be

reduced to a 1/3 value of DOL Delta starting. And ultimately power of the motor will be

reduced to a factor of 1/3. A disadvantage of this method is that the starting torque

(which is proportional to the square of the applied voltage) is also reduced to 1/3 of its

delta value.

Note that all six terminals of the motor are connected to wires. No

copper bars are used to configure the Delta connection; it is automatically done by the

contactors according to the control circuit. At the starting moment, line contactor & star

Contactor is energized. After a time delay while star contactor is being de-energized,

The Delta contactor will be energized & work as a DOL Delta motor. The control

Circuit of star delta starter is as below.

Figure 8(c). Control diagram of star delta starter

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8.1.3 Auto Transformer starter

This method also reduces the initial voltage applied to the motor and

therefore the starting current and torque. The motor, which can be connected

permanently in delta or in star, is switched first on reduced voltage from a 3-phase

tapped auto - transformer and when it has accelerated sufficiently, it is switched to the

running (full voltage) position. The principle is similar to star-delta starting and has

similar limitations. The advantage of the method is that the current and torque can be

adjusted to the required value, by taking the correct tapping on the autotransformer.

This method is more expensive because of the additional autotransformer

and uses this Starter for motors above 80kW. Consider figures 8(d) & 8(e). In this control

system, firstly star contactor will be energized. Soon after the transformer contactor will

be energized. Then after a time delay while main contractor is energized the star

contactor will be energized. At this moment, motor have got the full load. Then after a

time delay, transformer contactor also will be de energized.

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Figure 8(d). Control Diagram of an Auto Transformer Starter

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Figure 8(e) Power Diagram of an Auto Transformer Starter

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8.2 ATS (Automatic Transfer Switch)

Transfer switches are critical components of any emergency or

standby power system. When the normal (preferred) source of power is lost, a transfer

switch quickly and safely shifts the load circuit from the normal source of power to the

emergency (alternate) source of power. This permits critical loads to continue running

with minimal or no outage. After the normal source of power has been restored, the

retransfer process returns the load circuit to the normal power source. Transfer switches

Are available with different operational modes including:

Manual

Automatic

Most of the times both of above are available as one unit according to the

customer requirements. ATS is mostly a relay logic control unit, but sometimes available

as programmable logic control unit. The typical control diagram of an ATS is as below.

The main items that are used in ATS are contactors with electrical & mechanical

Interlocks. Two coupled contactors with mechanical interlocks doesn’t energize at the

Same time. If one contactor is energized then automatically other contactor will be de

energized. That means at any moment path is provided for only one source, not the

both of them.

Consider figure 8(f). The task of the timer T1 is, to wait a given time to observe

Whether there is any failure again in the main supply (To avoid continuous switching

In case of a back to back failures when generator runs) T2 timer is used to provide a

Delay to energize CEB side. And T3 timer is used to provide a delay to energize

Generator contactor (This is in case of a little time failure. To avoid the starting of a

Generator for a little time failure)

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Figure 8(f). Typical Control Diagram of ATS

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Figure 8(g). ATS CCT of auto & manual Operation

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Chapter 09

Capacitor Bank

9.1 Design

9.2 Uses of HRC fuse

9.3 Uses of capacitor contactor

9.4 Calculation of size of cap. bank

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9.1 Design

Capacitor banks are mainly installed to provide capacitive reactive

compensation/ power factor correction. The use of capacitor banks has increased

because they are relatively inexpensive, easy and quick to install and can be deployed

virtually anywhere in the network. Its installation has other beneficial effects on the

system such as, improvement of the voltage at the load, better voltage regulation.

Normally in factories or other high power consuming places, most

probably there will be a consumption of inductive load. Inductive voltage means that

there must be a lagging power factor. In order to reduce the tariff & utilization of power

the power factor must be taken near to 1. That means power factor angle must be taken

to zero. To do this we supply a capacitive load to compensate the inductive load. This is

the system of a capacitor bank.

The power factor regulator combines comprehensive operation with user-

friendly control setting. It uses numerical techniques in computing the phase difference

Between the fundamentals of current and voltage, thus precise power factor

measurement is achieved even in presence of harmonics. The power factor regulator is

designed to optimize the control of reactive power compensation. Reactive power

Compensation is achieved by measuring continuously the reactive power of the system

And then compensated by the switching of capacitor banks. The sensitivity setting

Optimizes the switching speed. With the inbuilt intelligent automatic switching

Program, the power factor regulator further improves the switching efficiency by

Reducing the number of switching operations required to achieve the desired power

Factor.

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Figure 9 (a) Wiring Diagram of a Capacitor Bank

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9.2 Uses of HRC fuse

Figure 9 (b) HRC fuse

In electrical system fuse acts as protection device and depending on

application different type of fuse is to select. Out of these different type of fuses HRC is

also one of the type and it stands for “High Rupture Capacity". This type of fuses

normally used where some delay is acceptable for protecting the system. it has a

advantage of current limiting feature. So it is used for protection of contactors which

may melt for higher value of current. H.R.C fuses acts as secondary protecting devices

[back up protection]. This type of fuses normally used where some delay is acceptable

for protecting the system. That means this fuse will not burn out for a current pulse & as

aresult of this it identifies a fault current & an inrush current separately. So these fuses

are used in series with motors & surge arresters.

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9.3 Uses of Capacitor Contactors

Many customers use power-factor correction capacitors to increase the

efficiencies of their overall power systems. When switching capacitors in and out of the

power system, the switching device (contactor) can experience initial in-rush currents

near 180x the nominal current. This high current can reduce the life of the contactor.

The Capacitor Contactors include early-make auxiliary contacts that bring pre-charge

resistors into the circuit to handle the high in-rush currents.

Figure 9 (c) Capacitor Contactor

9.4 Calculation of size of cap. Bank

Calculation and selection of required capacitor rating

Qc = P* tan(a cosα1)-tan(a cosα2)

Where,

Qc = required capacitor output (kvar)

α1 = actual power factor

α2 = target power factor

P = real power (KW)

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The table below shows the values for typical power factor in accordance with

the above formula.

0.7 0.75 0.8 0.85 0.9 0.92 0.94 0.96 0.98 1.0

A.P.F

0.40 1.27 1.41 1.54 1.67 1.81 1.87 1.93 2.00 2.09 2.29

0.45 0.96 1.10 1.23 1.36 1.50 1.56 1.62 1.69 1.78 1.98

0.50 0.71 0.85 0.98 1.11 1.25 1.31 1.37 1.44 1.53 1.73

0.55 0.5 0.64 0.77 0.90 1.03 1.09 1.16 1.23 1.32 1.52

0.60 0.31 0.45 0.58 0.71 0.85 0.91 0.97 1.04 1.13 1.33

0.65 0.15 0.29 0.42 0.55 0.68 0.74 0.81 0.88 0.97 1.17

0.70 0 0.14 0.27 0.40 0.54 0.59 0.66 0.73 0.82 1.02

0.75 0 0.13 0.26 0.40 0.46 0.52 0.59 0.68 0.88

0.80 0 0.13 0.27 0.32 0.39 0.46 0.55 0.75

0.85 0 0.14 0.19 0.26 0.33 0.42 0.62

0.90 0 0.06 0.12 0.19 0.28 0.48

The required capacitor output may be calculated as follows:

Select the factor (matching point of actual & target power factor) – k

Calculate the required capacitor rating with the formula:

Qc = k*P

Example:

Actual power factor = 0.7

Target power factor = 0.96

Real power (P) = 500kW

Qc = k*P

Qc = 0.73 * 500kW

Qc = 365kvAR

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GENERAL INDUSTRIAL TRAINING REPORT

Name : K.V Chamal Harsha Kumara

Address : 439/c, Miriswatta , Ittapana

Course : National Diploma in Engineering Sciences

Field of Engineering : Electrical (Power) Engineering

Registration NO : EP/08/7102

Name of Establishment : Electro Metal Pressing (PVT)LTD.

……………………………. ………………………………….

Date The officer in- charging

…………………………… …………………………………..

Date General Manager

Report(GIT)

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