NATIONAL TRANSMISSION AND DESPATCH CO.
LTD
BOOK OF PROTECTION AND
INSTRUMENTATION TRAINING PROCEDURES
(TSG PROTECTION AND INSTRUMENTATION FIELD
TRAINING SKILLS UPGRADING TRAINING
PROGRAM)
TSG TRAINING CENTRE NKLP LAHORE
TSG NTDC P&I SKILLS UPGRADING TRAINING PROGRAM
TABLE OF CONTENTS
Sr. No.
1
2.1
2.2
2.3
2.4
2.5
2.6
COURSE CONTENTS
Introduction
Safety Principles
Electric Shock
First Aid
Artificial Respiration
Low Voltage hazards
Grounding and Bounding, Absolute Limits of
Approach, Use of PPE
2.7
2.8
2.9
15
Permit to Work(PTW)
17-22
Practical project on PTG installation, first aid and 23-25
artificial respiration.
P&I Tools and T&P like clamp on ampere 26-64
meter,secondary injection set,universal set,C&DF test
set, energy meter set and CT analyser along with relay
test performas for different kind of protection in field.
Bus bar diffrantial literature and performa for 65-88
inspection at grid station.
Teleprotection and cross trip protection scheme along 89-100
with check sheet during field visit.
Electrical drawings for AC,DC schematic and wiring 101-120
drawing for demonstration
Annunciation and alarm system
121-131
Breaker failure relay literature and test performa for 132-162
testing during OJT
Batterey and batterey charger theory along with Vol-II
inspection sheets for checking / calibration of battery
charger in field.
Energy meter theory and testing procedure for single VOL-III
and
three
phase
energy
meters
(Electromechanical/Numerical)
3
4
5
6
7
8
9
12
Page No.
1-5
6-12
13
14
14
15
15
TSG NTDC GRID MAINTENANCE SKILLS UPGRADING TRAINING
PROGRAM
1.
INTRODUCTION
Technical Services Group (TSG), was established in 1985 under the technical
assistance and financing of Canadian International Development Agency
(CIDA) under CIDA/WAPDA Project Phase-II. The Project Phase-II was a
continuity of the already completed CIDA/WAPDA Project Phase-I, under
which the GSO Training Center Tarbela was established in 1980, to meet with
the requirements of technical training of Grid System Operation (GSO) staff.
The objectives of TSG were to set up a pool of technical experts to improve the
performance of Grid System through consultancy services and providing
training for capacity building of the workforce of GSO in all the three major
disciplines:
Grid station maintenance,
Protection and instrumentation (P&I) maintenance,
Transmission lines maintenance.
CIDA/WAPDA Project Phase-II was completed in 1990, since then TSG was
working indepedantly.
At present (in line with the original strategy) the P&I training has two
semesters. The first semester covering theory of protection relays and lab work
at GSO Training Centre Tarbela, whereas the second semester covering on-job
P&I training at TSG Training Centre, NKLP, Lahore.
Maintenance has become nowadays an important factor due to many reasons.
Economic and legal considerations are among the most significant, for example
extending the service life, reducing life cycle costs, reducing downtimes, safety
aspects and environmental protection regulations. In addition to the purchase
costs, the profitability of switchgear and controlgear in both the high and
medium-voltage systems depend above all on the calculated operating costs for
the entire service life.
Therefore, to meet with the current requirements of up-gradations in the
electromechanical technologies, emerging modern trends of maintenance,
standards/specifications and awareness of the technical staff of grid stations
these training manuals have been revised.
It is mandatory for the user of this manual that he must possess theortical
knowledge of electromechnical/solid state/numerical relays and has completed
semester-1 of the P&I training at GSO Training Center Tarbela.
TSG NTDC P&I SKILLS UPGRADING TRAINING PROGRAM
2.
CONCEPT OF MAINTENANCE
1.
WHAT IS MAINTENANCE?
The term “maintenance” is encountered frequently, though it is used with
different meanings. Its overall concept includes inspections, scheduled
maintenance and corrective/non-scheduled maintenance. As per IEC
standard/specifications, maintenance is the combination of all technical and
administrative actions, including supervision actions, intended to retain an item
in, or restore it to, a state in which it can perform a required function. The
proper maintenance also ensures correct operation of grid station equipment
permanently over its design life, even longer if it is justified economically and
technically. Generally the maintenance work is categorized as scheduled
maintenance and non-scheduled maintenance.
1.1.
SCHEDULED MAINTENANCE
The preventive maintenance carried out in accordance with an established time
schedule. Scheduled maintenance covers all measures aimed at retaining the
design state of the technical equipment belonging to a system and may take
place as and when required or in regular/fixed intervals of time. Scheduled
maintenance includes such activities as cleaning and washing, conservation,
lubrication and where necessary amending or replacing parts subject to wear
and tear. Scheduled maintenance also involves preparation of maintenance
schedules, carrying out the specified work and dealing with feedback relating to
this work.
1.2
NON-SCHEDULED MAINTENANCE
Non-scheduled/corrective maintenance is often not in accordance with an
established time schedule and usually needs a result of malfunction or
unexpected defect. Non-scheduled/corrective maintenance covers all measures
aimed at restoring the designed state of the technical equipment belonging to a
system. Repair works and part replacement are typical types of corrective
maintenance. It also involves planning, handling requests for
performing/checking and evaluating the necessary measures (functional tests
etc.). It is worth mentioning that an effective preventive maintenance program
always minimizes emergency maintenance, breakdowns and damages of grid
station equipment.
2.
PREVENTIVE MAINTENANCE PROGRAMME
The responsibility of carrying out maintenance work always lies with the owner
of the equipment i.e., NTDC. The company is under an obligation to observe all
the valid rules and specifications. The specifications of maintenance work must
be based on certain requirements, standards, specifications and the guidelines
supplied by the manufacturer. The main activities of a comprehensive
preventive maintenance programme are as under:
2.1
MAINTENANCE INTERVALS
There are three main criterias, which determine the maintenance intervals for
protective equipment:
- The recommended time and service period
- The number of operations
It is a universal practice that most of the Relays testing work is carried out on
the criteria of recommended time periods of service life of the protective
equipment (daily, weekly, monthly, quarterly, annually, 5 to 10 yearly, 20
yearly, etc.). Maintenance is carried out rarely on the criteria of rate of
operations.
Regular or scheduled inspections, scheduled maintenance, non-scheduled
maintenance all are the basic features of a preventive maintenance program.
2.2
INSPECTION
Visual inspection/investigation of the principal features of control gear and
other equipment in service belonging to a system carried out, without
dismantling, to evaluate the actual status. Inspections are also described as,
walk around visual inspection from distance keeping in view the safe limits of
approaches. Shutdown of the equipment is not involved normally. On the bases
of inspection data, short and long-range work programs for carrying out
preventive maintenance are prepared to meet with the best possible level of
operational availability and reliability of the protective system.
Overhauling may be categorized, as minor overhauling and major overhauling,
depending upon the specific instructions of the manufacturer and / or local
experience and policy of the company.
TSG NTDC GRID MAINTENANCE SKILLS UPGRADING TRAINING
PROGRAM
3.
JOB PLANNING
OBJECTIVE:
You will do job planning for routine and emergency grid maintenance jobs from
start up to completion of the job, following the procedure and steps given
below.
A)
JOB PLANNING PROCEDURE AND STEPS
Job Planning is the name given to the process of thinking to pool ideas or
opinions to do some job in a safe and efficient way. The job may be
routine and preventive maintenance work or an emergency work. Jobs are
executed more efficiently and effectively when jobs are planned well and all
concerned know what is expected. The key points to do consider for planning a
job are as given below:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Follow the work program.
Arrange testing procedures.
Arrange equipment manual and drawings.
Arrange previous testing records.
Arrange the spare parts, if required.
Arrange T & P and test equipment needed.
Estimate and arrange to meet the expenditure involved.
Estimate the number of man-hours and the length of .time required to
complete the job.
Arrange to get co-ordination of the other work groups ( grid maintenance,
T/L etc.), if needed.
Arrange shut down of the equipment to be worked on, if needed (refer procedure for
PTW).
.
Inspect job site to look for:
11.1 Hazards,
11.2 What equipment is to be de-energized to get safe working clearances?
11.3 Isolation points & grounding facilities.
11.4 What types of aerial devices (i.e. scaffold, bucket truck, ladders and
cranes) are required?
11.5 Is there enough room/space for aerial devices and the ground condition
permits to be fix/move them.
11.6 Approach roads condition.
11.7 Other information of job site that you think necessary for execution of the
job.
12.
Conduct a tailboard conference or meeting with the crew member to brief
them and ensure that each person knows what to do.
13.
Conduct a job safety analysis. The purpose of job safety analysis is to
uncover inherent or potential hazards, which may encounter in the work
environment and develop possible ways in which the electrical hazards
can be eliminated or effectively controlled.
TSG NTDC GRID MAINTENANCE
SKILLS UPGRADING TRAINING
PROGRAM
4.
JOB SAFETY AWARENESS AND
SAFETY CODE
OBJECTIVE
You will get safety awareness and follow
the prescribed safety rules, guidelines
while on work for your own safety, of
fellow workers, and of the company’s
property following the safety information
given hereunder. It is the responsibility of
man-incharge and of each crew member to
constantly be on the lookout for safety
hazards and to take definite steps to
eliminate or control all identified hazards.
4.1 INTRODUCTION
Prior to undertaking, any of the
maintenance procedures outlined in this
manual, proper work protection shall be
established as necessary in accordance
with the company’s Safety Code. All work
activities shall comply with applicable
safety rules and regulations. In addition to
the above, a safety hazard identification
exercise shall be undertaken.
In a work place, hazards are always
expected to the workers and/or the
equipment. The unsafe acts and unsafe
conditions increase the chances of
accidents whether fatal or non-fatal. Flow
of unwanted energy also presents
accidents. Safety can be achieved only
through intelligence, cooperation and an
understanding of adherence to safety
measures. The theme of safety policy of the
companies should be as follows:
“No Operating Condition or Urgency
of Service Can
Ever Justify
Endangering the Life of Anyone”
4.2 FUNDAMENTALS OF THE SAFETY
The electricity companies i.e. NTDC,
DISCOs, GENCOs, etc. must have a welldefined safety programme to provide safe and
healthy
environment
to
their
workers/employees with the following
objectives:
- The prevention of accidents, injuries and
weaknesses of professional skill shall be
integrated into all aspects of every work
activities performed for or on behalf of
company.
- All levels of management and supervision
shall be responsible for providing a safe
working environment as well as elimination
of the factors causing health hazards. They
shall also be responsible for provision of
adequate protective equipment, tools and
devices for the safe execution of works and
shall contribute for the development in
performing their work so as to ensure their
safety.
- Management shall provide adequate training
to employees in phases so that they become
well acquainted to perform the assigned
works safely.
- All persons whether employees of
companies or contractors working on a site,
shall comply with the applicable safety
legislation of the Government of Pakistan. In
addition, they shall comply with safe working
practices of their companies, already
established, to ensure their own safety as well
as fellow workers.
- Contractors working at sites involving
electrical hazards shall perform the work with
specially trained personnel following the
procedures
generally recoganized
by
companies to be safe and adequate for work
in proximity to live electrical apparatus.
equipment being made live.
- Specific safety requirements for contractors
shall be written in the contract documents.
- All levels of management and supervision
shall organize and administer a safety
programme to develop safety culture among
the employees. The safety directorate shall
promote and monitor safety programmes on
regional, circle and divisional levels in
company.
4.3
IMPORTANT DEFINITIONS
Circuit means and arrangements of devices
or media through which electric current can
flow.
Conductor means a component intended to
carry electric current.
Danger Notice means, a notice attached to a
live electrical apparatus, calling attention to
the danger of touching or interfering with
such apparatus.
Accident is the result of an unwanted energy
flow OR the result of any unsafe-act or
unsafe-condition
that
persists
during
execution of work.
Dead means de-energized and earthed.
Approved used in this code means approved
by company.
Earth means, the conducting mass of the
earth whose electric potential at any point is
continuously taken as zero.
Apparatus device or assembly of devices
that can be used as an independent unit for
specific function.
Authorized Person means a person who is
authorized to perform the duties pertaining to
his employment, the authorization being by
an officer of company, empowered for that
purpose.
Barrier is a temporary non-conducting
obstacle that is placed to limit the distance
that the workers can reach or approach to
anything that is at a different electrical
potential from them OR a means to control
energy flow.
Body Internal Resistance is the resistance of
the body after the skin has been punctured.
Bonding is the process of electrically
connecting conductive objects together to
bring them to the same electric potential.
Caution Notice means a notice attached to
dead electrical apparatus to prevent such
De-energized means, disconnected from all
sources of electricity.
Earth Connection means a metallic
conductor for connecting electrical equipment
to earth.
Earth Mesh means a network of a copper
conductor burried in the earth and connected
with earth mass through earth electrodes to
control step and touch potential and to
provide easy earth connection to the
equipment.
Electric Shock is the sensation and muscular
spasm caused by electric current flowing
through the body. Effects of electric shocks
are mild tingling sensation, severe muscular
contractions, respiratory paralysis, heart
stoppage and death.
Electrocution is the death caused by electric
current flowing through the body.
Equipment means any item used for such
purposes as generation, conversation,
transmission , storage, distribution are
utilization of electrical energy such as
machines, transformers, apparatus, measuring
instruments, protective devices, appliances,
etc.
Hazard is the potential for an unwantedenergy-flow to occur OR any unsafe-act or
unsafe-condition that may cause an accident
to the worker or damage to property.
Hot or Live (or alive) means electrically
energized.
Human Body Resistance is the skin
resistance and the major contributor to total
body resistance at voltages below 600 volts
AC. Factors that affect skin resistance are
pressure of contact, contact surface area,
duration of contact and moisture content of
the contact surface area.
Insulated is a term used to describe a device
or medium isolated from earth or other
potential by an insulating material. However,
it shall not be considered safe to touch unless
proper
personal
insulating
protective
equipment is used or apparatus or line is
made dead.
Insulating Protective Equipment is
protective equipment made of rubber or other
approved insulating material used during
work on energized lines or equipment.
Insulator is a component designed to support
and insulates a conducting body.
Nominal Voltage means a suitable
approximate value of voltage used to
designate or identify a system.
Personal Protective Equipment (PPE) is an
equipment used/ worn by a worker for his
safety during work.
Potential is the degree of electrification at a
point in an electric circuit with respect to
some other point of reference such as earth.
Step Voltage The potential difference
between two points one meter apart on the
earth’s surface in the direction of maximum
potential gradient.
System means an electrical system in which
all the conductors and apparatus are
electrically connected to a common source of
voltage.
Touch Voltage The potential difference
between a grounded metallic structure that
can be touched and a point one meter away
on the earth’s surface. Voltage between
conductive
parts
when
touched
simultaneously by a person or an animal.
Working Clearance is the minimum distance
that workers shall approach anything that is at
a different potential from them.
Working Space is the amount of room
required for live conductors to perform a job
safely.
4.4
BASIC SAFETY GUIDE LINES
Personal safety is a primary feature of our
daily work, whether at home or office or field
so all the employees of the company, mainly
the un-trained and having multi-nature jobs,
must become familiar with these basic safety
guidelines.
General Principles: Accident prevention can
be accomplished only through possessing and
applying safety know how and whole hearted
cooperation of all members of the
organization. Learn and understand the
following five basic principles in job safety to
deal with the hazards:
IDENTIFY the Hazards.
ELIMINATE the hazards wherever
practical.
CONTROL the hazards when they cannot be
eliminated.
PROTECT against injuries in case a hazard
gets out of control.
MINIMIZE the severity of an injury, if an
accident has occured.
-Neither management and supervision, nor
the Safety Code can prevent accident without
the help of each employee.
-Unsafe workers are a danger to themselves,
their fellow workers, the public property and
the equipment with which they work. Due
care and attention to all safety rules and
devices is essential not only to prevent injury
to the workers but also to protect equipment.
-Capable and mentally alert employees will
avoid accidents by learning all they can about
their work, using proper safeguards,
protective equipment, and avoiding shortcuts
and make shift work methods.
-Good operation is safe operation. This is true
for both employees and equipment. A job
done safely is job done efficiently.
-Accidents do not “just happen”. Accidents
are the natural result of unsafe conditions or
unsafe acts, usually a combination of both.
Machinery and equipment generally are
manufactured to perform safely within limits
of design. In fact, statistics show that more
then 90% of accidents are due to the human
element, such as failure to use safety devices
and observe safety rules and procedures.
UNSAFE CONDITIONS: Some examples
of unsafe conditions which may cause
accidents are:Improper Guarding such as unshielded
moving parts of machine, in-barricaded floor
openings and excavation, unenclosed high
voltage equipment, lack of protective
equipment and insufficient warning signs etc.
Defective Material or equipment such as
mushroomed-head chisels, split handles,
deteriorated poles, poorly manufactured or
weak equipment.
Hazardous Arrangements such as those due
to poor housekeeping at work locations,
unsafe planning or inadequate working space.
Insufficient Light unsuitable location
producing glare or objectionable shadows.
Improper Ventilation such as insufficient
change of air or presence of harmful vapor,
dust or gas.
Unsafe Clothing that fits loosely and can
become entangled in wires and machinery,
and failure to use goggles, proper shoes and
insulated gloves or sleeves.
Unsafe Design and Construction due to
deviations from standard design and
specifications and poor workmanship.
UNSAFE ACTS: Some examples of unsafe
acts which may cause accidents are:
Operating Without Authority or Warning
such as closing switches without authority,
operating hoists and trucks without warning,
failure to place warning signs or signal man
where needed, failure to block equipment
against unexpected movement, failure to
observe work clearance procedures.
Operating or Working at Unsafe Speed
such as driving too fast, throwing material or
tools to another worker, jumping from
vehicles or platforms or running.
Making Safety Devices Inoperative such as
removing guards from machines, using
oversize fuses, blocking safety valves,
bypassing interlocks and isolating fire
protection etc.
Use of Unsafe Equipment or Improper Use
of Equipment such as using dull cutting
tools, mushroom-head chisels, and pipe
extension on wrenches not designed for them,
or the wrong tool for the job, or using hands
instead of hand tools.
- Noise energy,
- Pressurized fluid energy.
Unsafe Loading such as overloading cranes
and winches, carrying too heavy load.
Wrong or improper use of this energy can
cause accidents. The flow of wanted energy is
consumed in accomplishment of work e.g.
current flow in conductor, mechanical energy
in rotating machine, etc. Where as flow of
unwanted energy is a hazard e.g. making
inadvertent electrical contact, being caught in
rotating machinery, etc.
Placing or Leaving Objects where they are
likely to fall.
Mixing Improper Packing or combining
chemicals to form a dangerous mixture.
Taking Unsafe Position or Posture such as
working on live conductors from above
instead of below, walking under suspended
loads or too close to openings, lifting while in
awkward position, entering areas where there
are dangerous gases or fumes, passing on
curves of hills, riding on running boards or
other unsafe places on vehicles.
a) Body mechanics safety awareness
Body mechanics energy is derived from the
use of the body muscles and from the action
of gravity on the body. Normal activities such
as walking, bending, twisting, etc. and the
more work-oriented activities such as lifting,
carrying, pushing, pulling and climbing, are
examples.
Working on Equipment without Taking
Proper Precautions such as installing and
removing temporary earth, cleaning, oiling or
adjusting moving machinery, and working on
or near live electrical equipment.
Body mechanics injuries may be such as
pulled muscles, slips and falls on the same
and different levels. Other injuries may also
be caused by:
Distracting, Teasing or Startling such as
practical joking, horseplay, quarrelling or
annoying.
-A falling injury from a platform or tower due
to involuntary muscular response to an
electric shock.
Failure to Use Safe Clothing or Protective
Equipment such as failure to use insulated
gloves, hard hat or goggles.
-From striking another object due to
involuntary muscular response to a sudden
high intensity noise level, operation of an air
blast breaker, or release of a high-pressure
fluid.
4.5 DIFFERENT FORMS OF ENERGY
COMMONLY INVOLVED IN DOING
WORK AND THEIR SAFETY ASPECTS
b) Electrical energy safety awareness
Different forms of energy that we commonly
encounter in our every day work have been
identified as:
The basic injury hazard from electrical energy
is caused by the flow of current through the
body, which may be established by:
- Body mechanics,
- Electrical energy,
- Chemical energy,
- Mechanical energy,
- Heat energy,
- Light energy,
-direct physical contact,
-spark-over or flashover,
-electromagnetic induction,
-electrostatic induction.
In the work environment, hazards from subsequent absorption through the lungs.
electrical energy may be encountered when:
These substances include gases like carbon
monoxide, finely divided particulate matter
-working on electrical equipment,
like asbestos dust, and suspended liquid
-working adjacent to live electrical
droplets like hydrochloric acid mist. Gases
equipment.
absorbed into the lungs pass directly into the
blood and may replace necessary oxygen, thus
The electrical hazard i.e. flow of current causing asphyxiation. Other substances,
through the body may result in:
which enter the lungs, can eventually enter
the bloodstream and be deposited in the bones
-damage to the body tissues caused by the or organs.
heat produced by the current flow,
-malfunction of vital body organs,
-Toxicity
-body mechanics injury because of unplanned A toxic effect can result from a one time
physical movement.
exposure or from a long-term exposure. In
this context, it should be noted that some
c) Chemical energy safety awareness
chemicals used in industry are known to cause
cancer.
Chemical energy is the energy released when
an element or combination of elements d) Mechanical energy safety awareness
interacts with other matter. Hazardous
chemicals are those chemicals that can react Mechanical energy is the energy in an object
with or be accumulated in body tissue, because of its position or motion.
altering it either temporarily or permanently. Because of its position, such as charged
A potential hazard exists when employees springs, elevated objects, and because of its
work with chemicals, or where chemicals are motion, such as rotating objects, moving
stored.
objects.
The harmful effect to the body varies with the
chemical type, the concentration, length or
exposure, and in some cases, individual
reaction to the chemical. These effects may be
apparent immediately or develop over
extended periods of time. Handling of used
SF6 gas, Electrolyte of lead acid D.C battery
cells (dilute sulphuric acid-H2SO4) requires
special precautionary measures.
Mechanical energy may be found in
practically all work areas and activities, for
example:
-Gastrointestinal Absorption
Toxic materials, if swallowed, can damage
the gastrointestinal tract. They are absorbed
through the stomach and intestines, causing
damage to vital organs such as heart, liver,
kidneys and brain.
-Portable tools – wrenches, grinders, chain
saw, and hand drill.
-Mobile equipment – truck, forklift,
snowmobile, crane, tele-lift.
-Stationary machinery and equipment – lathe,
drill, press grinder, compressor.
-Structures – scaffold, ladders, storage bins,
towers.
-Winds and wind age - handling material in
-Absorption through the Lungs
the wind, wind blows dirt in your eyes,
Most industrial poisonings occur because of pressure differentials in buildings (doors),
inhalation of a harmful substance and truck doors slamming on your fingers.
e) Heat and Cool energy safety awareness
Heat is a form of energy, which may be more
commonly identified as “hot’ or “cold”.
Man’s body temperature is 98.6oF (38oC),
therefore, anything higher is considered as
hot, and anything lower is considered as cold.
Frostbite and/or sunburn are two fairly
common examples or the results of excessive
heat-cold and hot.
Some other forms of heat energy are:
-open fires (heaters),
-hot liquid (molten solder),
-hot metals (welding, engine exhausts),
-dry ice,
-Bare metals – extreme cold,
f) Light energy safety awareness:
-Materials and interaction with other energy
forms
Ultraviolet radiation causes physical and/or
chemical changes in some materials. This
may result in hazardous conditions because of
adverse changes to the electrical or chemical
properties of the materials. For example:
-polypropylene rope,
-Rubber gloves and electrical cover-up,
-Hoses,
-Gasket material,
-Live-line tools,
Oxygen produces ozone in the presence of
ultraviolet radiation. Cleaning fluids and
solvents (chlorinated hydrocarbons) produce
toxic gases like phosgene.
Flashes may cause involuntary movements.
The eyes have to be given time to adjust to
lighting changes (welding arc).
Light energy is a form of electromagnetic
radiation very close in wavelength to
ultraviolet radiation, which is invisible. The
effects of intense visible light and invisible g) Noise energy safety awareness
ultraviolet radiation on vision, skin, some
material, or other energy forms may create a Noise is defined as unwanted sound. It does
hazard such as:
not have to be loud. It could be the noise of a
truck, jet engine or a dripping tap. Our safety
-Vision
concern is the prolonged exposure to
The eyes may be damaged by exposure to excessive noise that can cause permanent
ultraviolet radiation from such sources as hearing damage.
welding, power switching, the sun, and
unjacketed mercury vapor lamps. The damage The delicate inner ear is the part that is
may be temporary or permanent depending on damaged by repeated exposure to noise. The
radiation intensity, length of exposure, type of degree of damage to the hearing ability is
eye protection worn, and the angle at which dependent upon the noise intensity, frequency
the radiation strikes the eye. Extreme damage and duration of exposure.
may result in blindness.
A hazardous noise area exists if the following
Excessive visible light or glare causes condition can be identified:
temporary loss of vision and may cause
discomfort in the eye, eye fatigue and -If you have difficulty in carrying out normal
headache. It rarely causes permanent damage. conversation.
Gas welding and electric welding with out -If you experience head noises or ringing in
proper protection of eyes is a serious hazard.
the ear after noise exposure.
-If you experience temporary loss of hearing
after being exposed for several hours to the
noise.
h) Pressurized fluid energy safety
awareness (liquid and gases)
4.6 ELECTRIC SHOCK
Electric shock is the after effect of electric
current flow through the body by application
of the voltage across the body. Some
conditions that can cause this are:
The term “fluids” applies to all substances
that offer no resistance to change of shape.
Fluids are divided into two classes – gases -direct physical contact with an energized
and liquids. Gases are easily compressed; conductor or component where a current from
liquids are virtually incompressible.
the source through the body to ground.
A pressurized fluid in either gas or liquid
form, has stored energy. Because gases are
very compressible, considered amounts of
energy can be stored up under pressure. A gas
under pressure can be turned into a
pressurized liquid; but when released from its
containment, the liquid rapidly returns to the
gaseous state.
-spark-over or flashover from an electric
source to the body with a resultant current
flow through the body to ground.
Where the pressure on a fluid is below normal
atmospheric pressure, it is termed to be under
vacuum.
In the source-body-ground circuit source
voltage, circuit resistance, contact resistance,
body resistance and the earth resistance or the
main variables that affect the flow of current
through the body.
-electromagnetic and / or electrostatic field
when bridge a human body, an electric may
flow through the body without physical
contact or arcing.
The safety considerations for pressurized
fluids energy are the hazards from the
uncontrolled release of the stored energy.
Basic Hazards to human beings as a result of
electric shock are the followings:
Some examples of pressurized fluids energy
in the work environment are: Liquid -The sensation of the shock alone can cause
petroleum gases, high-pressure air and oil an involuntary movement that can cause
lines, bottled gases, aerosol cans, and vacuum physical harm due to bumps, slips, falls, etc.
tanks.
-Physical damage to the body caused by the
Pressurized fluids may react with many other heat generated by the current passing through
energy forms:
the body.
-Ceasing of the functioning of vital body
Chemical energy - The gases may be toxic.
organs caused by the passage of current.
Heat energy - The gases may be flammable
and explosive.
-Physical damage to the body in the form of
Noise energy - The sudden release of high- external burns caused by the ultraviolet light
pressure fluids could result in damaging noise produced by an electrical arc.
levels.
Mechanical energy Struck by a flying 4.7 RESUSSITATIOIN AND FIRST AID
object as a result of the high-pressure fluids
being released.
Resuscitation or Artificial Respiration means
revival of an unconscious person to life i.e.
rising again from dead or restoration to life.
First aid is the immediate care of the injured
or sick person. Basic first aid is essential for
the treatment of injuries, which may
accompany electric shock. The treatment of
bleeding wounds and burns is essential for the
preservation of life after successful
resuscitation is achieved.
Principles of first aid (the three P’s)
-Preserve life,
-Promote quicker recovery,
-Prevent further aggravation of the wound.
Air is an example of this. Under normal
condition, dry air is a fairly good insulator,
however, when it is sufficiently by an electric
potential it can become ionized. In ionized
state, it becomes a good conductor.
Electrical conductors and their component
parts are designed so that they have sufficient
clearance from ground, such that the
intervening air is not stressed on the point
where it becomes a conductor. However,
when you bring the ground plane closer to the
conductor by tools or parts of your body,
there is always the danger that you overstress
the intervening air to the point where it
conducts i.e. an arc is former across the air
path.
Scope of first aid (the four D’s)
In this manner, you do not have to touch a
Diagnosis- Find out what is wrong by live component in order to receive a shock.
history, signs or symptoms.
The limit of safe approach considers this
Decide- On extent of treatment, remove cause phenomenon. The staff required to work in an
of the injury.
environment influenced by electrical energy
Do it- Promptly and calmly.
have been classified based on their
Dispose- off
the casualty: Send to do knowledge, training and experience and safe
doctor, hospital or home as conditions may limits of approach according to different
warrant.
levels of voltage established. These
classifications are as given below: Priority of treatment ((the three B’s)
1)
Work
by
unqualified/untrained
Breathing- Apply artificial resuscitation as workers: Unqualified and untrained persons
soon as possible.
shall not be allowed to approach, or work, or
Bleeding- Apply dressing to control or stop allow any material or equipment to approach,
bleeding.
closer to exposed live electrical apparatus
Burns- Apply dry dressing and transport to than the distances given in table 1.
medical aid as soon as possible to prevent or
to lessen shock.
2)
Work by qualified/trained workers:
The worker’s position in relation to the
4.8 CLASSIFICATIOIN OF WORK IN exposed live electrical apparatus shall be
THE ENVIRONMENT INFLUENCED BY established such that movement of his body or
conducting tools or equipment will not result
ELECTRICAL ENERGY
in any encroachment upon the distances given
Every substance is to some degree a in table 1.
conductor of electricity. Metals are good
conductors-insulators
are
very
poor 3)
Work by especially qualified/trained
conductors. Under the stress of electric workers:
The
person-in-charge
shall
potential, some poor conductors can take on carefully study the work location, and the
changes that make good or better conductors. possible extreme accidental or unplanned
movements of workers and any conducting For specially 750 to 15 0.31 m (1 ft)
tools and equipment, which they may be trained
000
using. The extreme boundary of the resulting Workers
required work area shall not encroach nearer
-do15 000 to 0.46
m
to exposed live apparatus than the absolute
50 000
(1.5ft)
limits of approach given in table 1. These
-do50 000 to 0.92 m (3 ft)
absolute limits of approach must never be
150 000
reduced unless the work is being done by
-do150 000 to 1.22 m (4 ft)
qualified employees having appropriate in the
250 000
use of protective equipment, such rubber
-do250 000 to 2.75 m (9 ft)
gloves, hose, hoods or barriers, or in
550 000
accordance with approved bare hand, live line
maintenance procedures.
Table 2: Safe limits of approach for Un4)
Un-insulated boom-type equipment insulated boom-type equipment e.g. mobile
e.g. cranes, power shovels, aerial ladder, cranes, etc. while working in vicinity of live
pole derricks, etc. Only qualified personnel electrical apparatus
shall use equipment of types as said above
near live electrical apparatus. All work shall Description
Nominal
Limits
of
be done in accordance-approved procedures, of
Phase
to Approach
and the distances from live apparatus given in Equipment
Phase
table 2 shall always be maintained.
Voltage
Table 1:
Safe limits of approach for
Range
workers while working in vicinity of live
(Volts)
electrical apparatus
For cranes 750 to 15 3.05 m (10
and power 000
ft)
Classification Nominal
Limits
of
shovels
of Workers
Phase
to Approach
-do15 000 to 3.05 m (10
Phase
50 000
ft)
Voltage
-do50 000 to 3.05 m (10
Range
150 000
ft)
(Volts)
-do150 000 to 4.58 m (15
For untrained 750 to 150 3.05 m (10
250 000
ft)
workers
000
ft)
-do250 000 to 6.10 m (20
-do150 000 to 3.58 m (15
550 000
ft)
250 000
ft)
For Aerial 750 to 15 0.92 m (3
-do250 000 to 6.10 m (20
Frames and 000
ft)
550 000
ft)
ladders
For
trained 750 to 15 0.92 m (3
-do15 000 to 1.22 m (4
workers
000
ft)
50 000
ft)
-do15 000 to 1.22 m (4
-do50 000 to 2.44 m (8
50 000
ft)
150 000
ft)
-do50 000 to 1.53 m (5
-do150 000 to 3.05 m (10
150 000
ft)
250 000
ft)
-do150 000 to 2.14 m (7
-do250 000 to 4.58 m (15
250 000
ft)
550 000
ft)
-do250 000 to 3.66 m (12
550 000
ft)
Table
4:
Conversion
of commonly used
Table 3:
Minimum
clearance
o
overhead lines (at 150 F/65.5oC)
Weight/mans
DESCRIPTION
400V & BELOW 11KV & 33KV
ft(m)
ft(m)
19 (5.8)
20 (6.1)
b) Along a Street
17 (5.2)
20 (6.1)
c) Across Private
15 (4.6)
15 (4.6)
Across Country
a) Across Street or
intersection
and places
inaccessible to
vehicularTraffic
-
-
- Inside Station Limit
31(9.5)
33(10.0)
- outside Station Limit
23(7.0)
25(7.6)
- Vertical
8(2.4)
12(3.7)
- Horizontal
4(1.2)
6(1.8)
Bottom/Earth Part of
2(0.61)
6(1.8)
Telegraph Lines
4(1.2)
6(1.8)
400 Volt Lines and
2(0.61)
6(1.8)
11KV Lines
-
4(1.2)
33KV Lines
-
6(1.8)
66KV Lines
-
-
132KV Lines
-
-
220KV Lines
-
-
500KV Lines
-
-
Rivers and Major
132KV
Pressure
220KV
ft(m)
1 Ton ft(m)
=
ft(m)
1000
Kg
20(6.1)
1 Kg 22(6.7)= 23(7.0)
2.204
Pound (lb)
1 lb
= 0.453
Kg
500KV
ft(m)
Atmosphere
27(8.2)
(standard) =
101.325
Kpa
= 14.7 psi
Length
Property, Footpath
Roads and Highways
66KV
factors
Canals from H.F.L
Railway Track
Building Part
Lines (Insulated
services, Guys,
Earth Wire etc.)
Below
1 micron
micro meter
1 mil
26(7.9) 26(7.9)
25.4 m
30(9.1) 30(9.1)
1 inch
2.54 cm
1 mm
34(10.4)
0.03936(11.0)
inch
26(7.9)
1 foot28(8.5)
0.305 m
1 m 17(5.2)
15(4.6)
3.280 20(6.1)
foot
15(4.6)
1 mile11(3.4)
7(2.7)
1.609 km
Gauge pressure
= 1.0 = Actual pressure+
= Atmosphere
31(9.45)
pressure
30(9.1)
30(9.1)
=
1 bar
= 100
= Kpa = 0.1 Mpa
37(11.3) 39(11.9)
1 Kpa
= 10
mbar
29(8.8) = 30(9.1)
1 Mpa
= 10
bar
20(6.1) = 25(7.6)
1 bar
= 14.5
25(7.6)
30(9.1)
psi = 1.02 Kg/cm2
13(4.0) = 15(4.6)
1 psi
= 0.07
2
Kg/cm
Force/moment
of 1 Kg/ cm2 = 14.21
psi
force/torque
9(2.7)
11(3.4)
13(4.0)
15(4.6)
1 Torr
=
7(2.1)
9(2.7)
11(3.4)
13(4.0)
1 Kg
= 133.328 Pa = 1.33
mbar
9.806 N
7(2.1)
1 Pa
=
1 N 9(2.7) 11(3.4) = 13(4.0)
7(2.1)
9(2.7)
11(3.4)
13(4.0)
0.0075 torr
0.102 Kg
1 Kpa
= 7.5
10(3.0)
1 Lb 12(3.7) 14(4.3) = 16(4.9)
m torr
4.448
N
12(3.7)
14(4.3)
16(4.9)
1 mbar
= 0.75
1- N
16.5(5.0)= 18(5.5)
torr
0.224
Lb22(6.7)
=
1 pound foot
= 1 psi
6.894 Kpa
1.355 Nm
=
1 Nm
= 1 Kpa
0.145 psi
0.749 lb.ft
1 Kgm
= 1 Kg/ cm2 =
98.066 Kpa
9.806 Nm
=
1 Nm
= 1 Kpa
0.010 Kg/Cm
0.102 Kgm
26(7.9)
1 Kgm
7.336 lb.ft
1 lb.ft
0.138 Kgm
Temperature
C=(F-32)x5/9
F=(Cx9/5)+32
= 1 Kg/litre = 10.1
Pound per gallon
= 1 Pound per gallon =
0.099 Kg/litre
1 atm
=
29.98 inch of Hg at
20oC
14.9 Psi
= 76
cm of Hg at 20oC
Vacuum
= (-)ve
pressure < 1 atm
1 torr
= 1 mm
o
Hg at 20 C
1. PTW introduction
TSG NTDC P&I SKILLS UPGRADING
TRAINING PROGRAM
5.
PERMIT TO WORK (P.T.W)
OBJECTIVE:
You will arrange shutdown of a power
equipment at a grid station for maintenance
purpose. After getting approval of shutdown
from the competent authority, you will
get/cancel Permit to Work (PTW) and you
will use the recommended work protections
to perform maintenance work safely by
observing the procedure given and the
applicable safety rules.
As per WAPDA/PEPCO rules, any type of
schedule/non-scheduled maintenance work on
any power equipment at a grid station must be
arranged by an authorized person. Before
starting work, the authorized person will get
approval for shut down of the equipment
from the competent authority. Then after
approval of the competent authority, the
authorized person himself or the other
authorized person will obtain Permit to Work
(PTW) from the shift engineer/shift in charge.
After having PTW and following the
instructions therein, he will start the work and
cancel PTW after completion of the work. A
properly issued PTW and instructions therein
implemented provide sufficient work
protection. Severe and fatal accidents result
by ignoring minute activities in this process.
2. Description of PTW
PTW
is
a
legal
document
of
WAPDA/PEPCO, which is issued in the
name of an authorized person to perform
maintenance work on power equipment. A
PTW has two copies double side printed
red & white (Reference copy attached).
When issued one copy is left in the PTW
book as office copy and the second is
handed over to the person in whose name it
is issued and the same he will return to the
issuing authority after doing the work or
when he wishes. Station operator cannot
make any switching operation on the
equipment, which is under PTW until he
does receive back the PTW duly signed by
the person in whose name it was issued.
3. How to Apply for Shutdown
The applicant must be an authorized person
(XEN/DM, AE/AM, Test Inspector / Lab
Assistant). For scheduled work, apply a
written request at least 72hours before the
date/time of the requisite work to be done.
For non-scheduled/emergency work there is
no restriction of pre-apply time. The
application/written request must contain the
following information (refer to single line key
diagram of the grid station):
- Equipment nomenclature in the application
(voltage level, control number, controlled
equipment).
- Equipment location (name of grid station).
- Nature of maintenance work (routine,
special, major or minor maintenance).
- Dates and timings for work.
Hereunder is given a specimen of the
application/written request for arranging
shutdown of an equipment.
From: Senior Engineer/Dy. Manager
220 KV G/S NTDC, New Kot Lakhpat
Lahore
To: NPCC/RCC
Islamabad/Jamshoro
Subject:
SHUT DOWN
A shut down is required on 132 KV Circuit
Breaker' KLP-4 controlling KLP-Saidpur
circuit at New Kot Lak Pat Grid Station for
the purpose of major overhauling of the
circuit breaker. This shut down is required
on dated _________ from _____ hours to
______ hours.
Please approve the shut down and inform
this office accordingly.
Signature
Copy to all concerned.
The shutdown has been approved and you
have been informed, now get PTW and
start work.
4. Procedure for Issuance of PTW
The following steps should be followed for
getting PTW:- Ask the shift engineer or shift in charge
station operator to issue a PTW on the
concerned equipment in your name.
- Station operator after his satisfaction will
isolate the equipment to be going under
PTW through local or remote switching
operations
- If applicable he will provide PTGs on the
equipment or will ask you to provide PTGs
before starting work.
- He will write the nomenclature of the
equipment on which it is safe to work on
front page of the PTW (upper column).
- He will also write (lower column) where
and on which points he has installed PTGs or
ask you to do the same.
- He will put his signature at the specific
space and ask you to receive your copy of
PTW.
- You must read the entries made by station
operator in his portion (front page of PTW)
and verify that equipment nomenclature,
isolation points and matter of the PTGs are
clear and correct. (refer grid station single
line key diagram).
- Then write your name, designation, date,
time in front column of backside of the PTW,
put your signature and receive your copy.
4.1. Return PTW after doing the Job
- After completion of the maintenance
work wind up your T&P and local safety
precautions (barriers, caution tags etc.)
- Remove PTGs.
- Ask the station operator to put caution
notice (reference copy attached) duly filled
and signed by him, on the control switch of
equipment mentioned in PTW.
- Tell your crew to stay clear of the
equipment because now it is no more safe
to work on.
CAUTION NOTICE
Caution notice is also a legal document of
WAPDA/PEPCO which is to be put on
controlling switch-gears, switching in those
the equipment under PTW can become live.
- Go to Control Room and fill up second
column (clearance certificate) of backside
of PTW. Now the equipment, which was
under PTW, is ready from your side for
putting in service.
CAUTION TAG
Caution tag is also a type of caution notice
but it has no legal value. This can be in any
form of a warning sign to be put on the
auxiliary supply control. switches. In our
system isolation switches on auxiliary
supplies (AC, DC, CT, PT supply, etc.) are
not provided normally in the equipment local
control cubical but in control room building,
so in case the isolation of these supplies is
required ask the operator also to put caution
tags on these switches.
4.3 Cancellation of PTW
- Now go at equipment site, have a walk
around from ground level and check isolation
points carefully and verify that these are as
mentioned in PTW, otherwise have them
corrected by the issuing authority.
- After having your complete satisfaction of
isolation and of your crew, install PTGs at
the desired points,
- Put barrier around the work area and
caution tags at the requisite locations.
Barrier may be a physical one or warning
signs.
- Perform the maintenance work.
- Now the station operator after his
satisfaction will cancel the PTW by making
entries in third column.
- Station operator will remove caution
notices after getting your signature therein
and making other - entries in caution
notices.
PTW (Permit to Work) Specimen
NATIONAL TRANSMISSION AND
DESPATCH COMPANY LTD
PERMIT-TO-WORK
It is safe to work on the following apparatus
which is dead, isolated from all live
conductors, and is earthed. All other parts are
dangerous.
_____________________________________
________________________
3.___________________________________
__________________________
_____________________________________
________________________
State below exactly the apparatus on which it
is safe to work:
Signature:
___________________Designation:
_______________________
1.
_____________________________________
_______________________
Date ________________________Time
________________________(Hrs)
PTO
_____________________________________
________________________
2.
_____________________________________
_______________________
_____________________________________
________________________
3.
_____________________________________
_______________________
_____________________________________
________________________
State below exactly at what point (s) the
apparatus is connected to earth:
1.___________________________________
__________________________
_____________________________________
________________________
2.___________________________________
__________________________
(Back side of PTW Form)
RECEIPT OF CLEARANCE
This form after being signed for the work to
proceed must be retained by the authorized
person in charge of the work until the work is
suspended or completed.
I hereby declare that I am the authorized
person in charge of work, for which the
apparatus mentioned hereon has been made
dead.
Signature_______________
Designation
__________________________
Date ____________________
Time
_________________Hrs)_____________________________________
_________________________
RETURN OF CLEARANCE
The apparatus mentioned hereon must not be
again made live until this Form has been
signed and returned by the authorized person
in charge of the work. In case where more
than one Permit-to-Work has been issued for
the same apparatus, it must not be again made
live until all forms have been signed and
returned by all the authorized persons in
charge of the work.
I hereby declare that all men under my charge
have been withdrawn and warned that it is no
longer safe to work on the apparatus specified
in this Form, and that gear, tools, temporary
earth connections are all clear, leaving that
portion of the apparatus upon which my men
have been working ready for placing into
commission.
Signature______________
Designation
__________________________
Authorized person in charge of the work
Date _____________________
Time
_______________________(Hrs)
_____________________________________
_________________________
CANCELLATION OF CLEARANCE.
TO MAKE IT LIVE WILL KILL THEM
No:
___________
Aerial
Line
_____________________________________
______________
Electrical
Apparatus
_____________________________________
_______
Working
party
in
charge
____________________designation
____________
(name)
This Caution Notice placed on controlling
switchgear at ________________
(time)
on ________________
(date)
I hereby declare this Form cancelled
Signed by Shift In charge
Signature__________________ Designation
________________________
Date ________________________
Time
_______________________(Hrs)
Note:
This Form, duly completed, must be kept for
record by the RE/AE/AM according to
instructions.
Work
being
done
_____________________________________
__________
Caution Notice Specimen
NATIONAL TRANSMISSION AND
DESPATCH CO LTD.
This Caution Notice removed from the
controlling switchgear in the presence of
_______
_____________________________________
_________________________
(name)
In charge of the, working party at
_____________________ on __________
(time)
(date)
Signed by In charge working party
Designation _____________________
CAUTION
MEN WORKING ON THIS APPARATUS
Signed by Shift In charge
TSG
NTDC
P&I
SKILLS The application of portable temporary
ground (P.T.G) to isolated electrical
UPGRADING TRAINING PLAN
6.
PORTABLE
GROUND (P.T.G)
TEMPORARY
OBJECTIVE
You will apply/remove Portable Temporary
Grounds (P.T.G) on/from isolated, electrical
equipment following the procedure given and
observing the safety precautions.
equipment in preparation for work is a
most important safety practice. P.T.Gs
provide essential safety not only to the
worker but also to the equipment, so it is
important that the reasons for grounding
an
electrical
equipment
are
well
understood. Grid maintenance work is
always performed on electrical equipment
with the equipment in isolated and
grounded state. Grounding of the
equipment to be worked upon is
accomplished by installing portable
temporary grounds on both or all sides of
the supply sources.
P.T.Gs provides a low resistance power
circuit between the electrical equipment
and station ground mesh. If due to an
accident or by mistake the equipment
being worked on is energized, then the
P.T.Gs provide a high capacity, low
resistance circuit between phases and
station ground if they are used correctly.
The P.T.Gs maintains this circuit until the
primary or back up protection relaying
senses the fault and disconnects the power
source.
2. Protection Provided by Properly
Installed P.T.Gs
The following protections and safe
conditions are automatically achieved if
P.T.Gs are provided on the input and
output connection sides of the equipment
to be worked upon:
- Positive proof of isolation
Drain
of
(Electromagnetic
potentials)
1. Introduction
induced
potentials
and
Electrostatic
- Guards against the danger of accidental
energization of the equipment being
worked on
- Ensures that non-current carrying
metallic parts of equipment remains at
ground potential
3. Fittings and Accessories of P.T.G Set
Grounding Cables: A PTGs set has 3
separate grounding cables. The length of
cable may vary according to the
requirement but must not exceed 15 feet in
length. 4/0 AWG (13.46 mm diameter)
stranded extra flexible copper cable is
recommended to be used as a P.T.G. cable
when fault currents are less than 34000
amps. 2/0 AWG stranded extra flexible
copper cable can be used when the fault
currents are less than 22000 amps.
The jacket or cover of the cable is only to
protect the copper strands from mechanical
damage and should not be relied upon for
insulation purpose.
Ground-End Clamp: The "Tee" handle
clamp is the most commonly used groundend clamp.
Line-End Clamp: The most commonly
used line end clamps are "All Angle
Clamp" and "C Clamp”. Both the "groundend" and "line-end" clamps must have the
same current rating as of the grounding
cable.
Grounding Stick: An approved epoxy
stick or any other insulated stick is used to
apply and remove P.T.Gs.
4. Procedure to Apply PTGs
A thumb rule to apply P.T.Gs is:
GROUND-END CLAMP MUST BE
ATTACHED TO THE STATION
GROUND SYSTEM FIRST AND
TAKEN OFF LAST
- Check the P.T.Gs hardware (cables,
clamps) and grounding stick for good
condition.
- Physically check and verify the isolation
of the electrical equipment to be worked
on with an approved tester or by an
approved method e.g. line teasing.
- Select a suitable ground conductor and
clean it with wire brush to remove
corrosion if any.
- Apply ground-end clamp at the cleaned
ground conductor. The clamp jaws must
fully cover the conductor and be tight.
Note. If installation of ground-end clamp
on station ground conductor is not possible
directly, then copper stirrups made of 4/0
solid copper can be used at that particular
location.
- Lay down the grounding cable on the
ground, fix up line end clamp into the
grounding stick hook and tight it fully.
- Open the line-end clamp jaws enough to
be put on the line conductor.
- Lift holding on only to the ground stick
to a vertical position. Get assistance from
a second person with a ground stick if
necessary
- With a firm grip of your hand on stick raise it
up and put the line-end clamp on the line
conductor by adjusting the jaw opening of
clamp so that it fully covers the line
conductor. Tighten the line-end clamp by
rotating the stick anti clockwise. Before
tightening it fully, turn it around the conductor
to remove corrosion, otherwise the line
conductor should be cleaned with line end
wire brush before applying P.T.Gs line-end
clamp on it.
- In the same way apply the remaining P.T.Gs.
- After having the P.T.Gs been applied, the
grounding cables should not be allowed to
swing but should be tied to the structure and
fastened with a nylon rope.
5.
Procedure to Remove P.T.Gs
A thumb rule to remove PTGs is:
WHILE REMOVING P.T.G.s, FIRST
REMOVE LINE-END CLAMP AND
THEN REMOVE GROUND-END CLAMP
- Untie the wrapped/fastened ground cables.
- To remove P.T.Gs, fix up ground stick hook
in to line-end clamp and rotate the stick
clockwise until the line conductor is fully
released. Then take off the clamp and lower it
to the ground gently. Take off the grounding
stick from line-end clamp.
- In the same way remove all the line-end
clamps.
- Then take off all the ground-end clamps.
- Coil all the P.T.Gs and tie each coil with a
piece of nylon rope.
6. Safety Precautions for Handling P.T.Gs
- While applying and removing P.T.Gs, safety
shoes, hard hat, eye protection flash goggles
and leather gloves must be worn.
- Avoid touching the ground cables when
installed.
- In damp or wet weather insulated rubber
gloves must be worn while applying and
removing P.T.Gs.
- Grounding stick must always be inspected
for good condition before use and held
away from body while in use.
- Potential testing on the equipment
concerned should be performed before
applying P. T. Gs. This can be done by
using approved potential testers, or by
touching the line conductor wish the
metallic head of grounding stick and then
slowly removing it. If a potential is present
a "buzzing sound" will be heard. This is
known as "teasing" a circuit. Potential
testing is necessary while applying P.T.Gs
in gas insulated switchgears (GIS).
- Some high voltage circuits may appear to
be live when teased due to induced
potentials.
- It is not necessary to test for any electrical
potential when the equipment is obviously
isolated.
- Safe limits of approach must always be
considered while applying and removing
P.T.Gs.

m
3
5
2
0
0
S
i
o
6
2
0
S
3
0
L
1
1
1
1
1
1
1
1
1
r
=
i
O
Z
2
0
L
3
P
U
B
L
I
C
A
T
I
O
N