SEMINAR REPORT
ON
400Kv GRID SUBSTATION
HEERAPURA
ACADEMIC SESSION 2013-14
SUBMITTED TO: - SUBMITTED BY:-
MR. ANOOP MAHESHWARI ROHIT NAIR
(EXECUTIVE ENGINEER ) VIT
ELECTRICAL
A CKNOWLEDGEMENT
Words fail me to express my sincerest gratitude to this esteemed organization, which has
conferred on us the privilege to pragmatically convert our theoretical knowledge into practical
viable experience. During the course of my training at 400Kv GSS HEERAPURA, JAIPUR so
many people have guided me and I will remain indebted to them throughout my life for making
my training a wonderful learning experience.
I would like to thank MR. ANOOP MAHESHWARI my project head, who gave me
opportunity to work in his department and guided me through my project from time to time. His
words were a true inspiration for me. The exposure that I have got here would not have been
possible without his kind support.
He took keen interest in my project and ensured that my tenure here is a learning experience for a
lifetime for me.
I would like to thank MR. A.P VISHNU sir and all those operators, Diploma Engineer Trainees
and my trainee colleagues with whom I had developed a special bond.
PREFACE
As per the requirement of B. Tech. Course,400Kv GSS HEERAPURA, JAIPUR (RAJ.) has
been kind enough to permit me to complete my Practical Training of 30 days.
This report prepared during the practical training which is student’s first and greatest treasure as
it is full of experience, observation and knowledge.
The summer training was very interesting and gainful as it is close to real what has been studied
in all the years through was seen implemented in a modified and practical form.
GSS is the means of connection between generating station and consumer by providing safety
and reliability of system in case of default.
This substation step down the incoming voltage power transmission to the required valve and
then is supplied to the consumer feeder or GSS done by connecting auto transformer operation
and requirement of various equipment have been include in detail , further in case of report is
the bus bar.
Arrangement of different feeder level and switch yards included information of bus bar
arrangement of different level isolator and growing substation also power transformer circuit
breaker oil, filtration plant, and compression protection control room and place are leveled.
CONTENTS
1.Introduction
2.Equipments in G.S.S.
3.Transformer
4. Bus Bar
5.Circuit breaker
6.Lightening arrestor
7.Isolator
8.Current Transformer
9.Capacitive Voltage Transformer
10.Wave Trap
11.Relays
12.Oil Testing Lab
13.Earthing
14.PLCC
15.Control room
16.Conclusion
INTRODUCTION
When India became independent, the overall installed capacity was hardly 1900 mw. During
first year plan (1951-1956) this capacity was only 2300 mw. The contribution of Rajasthan state
was negligible during 1&2 year plans the emphases was on industrialization for that end it was
considered to make the system of the country reliable. Therefore Rajasthan state electricity board
came into existence in July 1957.
In India electrical power is generated at a voltage of 11KV to 33 KV, which is taken
stepped up to the transmission level in the range of 66 KV to 400 KV Member of transmission
and switching have to be created. These are known as “SUB STATION”. Along these
transmission lines secondary substation are created where voltage is further stepped down to sub
transmission and primary distribution voltage. A substation is an assembly of apparatus, which
transform the characteristics of electrical energy from one form to another say from one voltage
level to another level. Hence a substation is an intermediate link between the generating station
and consumer. For economic transmission the voltage should be high so it is necessary to step up
the generated voltage for transmission and step down transmitted voltage for distribution. For
this purpose substations are installed. The normal voltages for transmission are 400kv, 220kv,
132kv and for distribution 33kv, 11kv etc.
The 400 kV G.S.S. HEERAPURA RAJASTHAN RAJYA VIDYUT PRASARAN
NIGAM Ltd. (R.R.V.P.N.L.) is ideally located at the Heerapura ajmer road Jaipur Rajasthan.
G.S.S. is the means of connection between Generating Station & Consumers
(Industrial & Domestic etc.) by providing safety & reliability of whole system in case of fault.
A G.S.S. is an assembly of apparatus, which transform the characteristics of
electrical energy from one form to another say from one voltage level to another level. Hence a
G.S.S. is an intermediate link between one G.S.S. to consumers. For economic transmission the
voltage should be high so it is necessary to step up the generated voltage for transmission and
step down transmitted voltage for distribution. The normal voltages for transmission are 400 kV,
220 kV, 132 kV and for distribution 33 kV, 11 kV etc.
In Rajasthan, R.R.V.P.N.L. is responsible for transmission and distribution of
electrical power all over Rajasthan.
The steps of this sub-station are:- To step down the incoming voltage of the power transmission
to a required value i.e. 400 kV to 220 kV &132 kV and further.
There are three incoming lines from different four sub-stations.
These are:-
• Heerapura is connected to Bassi via two lines of 400kV named Bassi1 and Bassi2.
• Heerapura is connected to 400kV Merta line.
• Heerapura is connected to 400kV Hindaun line.
EQUIPMENTS IN G.S.S
2.1 EQUIPMENTS AVAILABLE IN THE HEERAPURA400kV G.S.S. JAIPUR, RAJASTHAN
• Transformer(400kV)
I.D. NO. MAKE CAPACITY VOLTAGE(kV) CURRENT
ILT-1 TELK 250MVA 400/200/33 361/656A
ILT-2 DO DO DO DO
ILT-3 DO DO DO DO
ILT-4 DO 315MVA DO 455/828A
• C-Transformer(400kV)
SR.NO.
ID.NO. MAKE
TYPE VOLTAGE(kV)
RATIO
1. SCTA,SCTTA,SCTTB,SCTB
WS ATS 400/2
420/630/142 2000/1000/300/1
2. 4CTA,4CTTA,4CTTB,4CTB
DO DO DO DO
3. 2CTA,2CTTA DO DO DO DO 4. 2CTB,2CTTB ABB TMBRL
-420DO 455/828A
• C.V.Transformer(400KV)
SR.NO. ID.NO MAKE/TYPE RATIO BURDEN CLASS SEC,CAP
1. BASSI-1 WSI/CVE420/1425 400 200,200,100 3P,3P,0.5 80,000PF 2. BASSI-2 DO DO DO DO DO 3. BUS-1 DO DO DO DO DO 4. BUS-2 DO DO DO DO DO
• C.V.Transformer (220KV)
S.No
ID.NO. MAKE/TYPE RATIO BURDEN CLASS SEC,CAP
1. BUS-D CROMPTON 220/3KV/110/3,110,110/3V
200,100,100
5/3P,3P,3P 48,400PF
2. BUS-E WSI/CVE/245
DO 200,200,200
3P,3P,3P/0.5
DO
3. BUS-F DO DO DO DO DO 4. PHULER
ADO 220/3kV/110,110/3V 200,200 0.5,0.5 DO
5. KTPS-1 HBB245-N 220/3KV/110/3,110V DO DO DO 6. KTPS-2 CROMPTON 220/3kV/100/3,110/3V DO DO DO 7. KOTA-3 WSI DO DO DO DO
• Circuit Breaker (400kV)
SR.NO.
ID.NO.
.MAKE TYPE VOLTAGE(KV)
CURRENT
STC DCF
SFG/HYD
1. 552A BHEL 3AT 420/520/1050,1425
2000A 40KA/1S 29,000MVA
1.3 7.5/350
2. 552T DO DO DO DO DO DO DO 3. 552B M.G.
(FRAN)FA2R DO 3150 DO DO 7/300
4. 552T NGEF S2-M420 420/610/1425 2000 DO DO 8.0/35(PN)
5. 252A BHEL 3AT3 420/520/1050/1425
2000 DO DO 7.5/250
6. 552T DO DO DO DO DO DO DO 7. 252B ABB EL(V)FS
L6-2420/1050,1425
3150 40KA/3S DO 7.0/31.5
• Circuit Breaker(220kV)
SR.NO. ID.NO. MAKE TYPE VOLTAGE(KV) CURRENT
1. 2452C NGEF S1-245 245/460/1050 2000A 2. 2352C DO DO DO DO 3. 2052C DO DO DO DO 4. 1652D DO DO DO DO 5. 1652C DO DO DO DO 6. 2259C ABB ELFSL4-1 245/1000KV DO 7. 1852C DO DO DO DO 8. 1752D DO DO DO DO 9. 1652G DO DO DO DO 10. 2252D HVV DLF-
245NC-2245/460/1050KV
DO
11. 2152D DD DO DO DO 12. 1952C ABB ELFSL4-1 245/1050KV 3150A
• Lightning Arrester(400KV)
SR.NO. ID.NO. .MAKE TYPE VOLTAGE(KV)
CURRENT
1. BASSI-1 WSI CPL 360KV 10KA 2. BASSI-2 PLPRO ALUGARD-
2DO DO
3. ILT-1 DO DO DO DO 4. ILT-2 DO DO DO DO 5. ILT-3 WSI 10KA 890KV 10KA 6. ILT-4 DO DO DO DO
• Lightning Arrester(220KV)
SR.NO. ID.NO. MAKE TYPE VOLTAGE(KV) CURRENT 1. ILT-1 ELPRD ALUGARD-
2DO DO
2. ILT-2 ELPRD ALUGARD-2
DO DO
3. ILT-3 DO DO DO DO 4. ILT-4 DO DO DO DO 5. KTPS-1 OBLUM METOVAR DO DO 6. KTPS-2 WSI CPL-2 DO DO 7. KOTA-3 WSI CPL-2 DO DO 8. PHULERA AEG 4S204 204 DO
• Isolators(400kV)
S.No. ID.NO. MAKE TYPE VOLTAGE(KV) CURRENT STC 1.
589AAAB(S/EB) S&S RC500 MGB
420/1425 2000A 40KA/1S
2.
589AL,(D/EB) DO DO DO DO DO
3.
589A,589B(S/EB) DO DO DO DO DO
4.
589BA,BB(S/EB) RADE-KONKAR
RVZ420-3-20-LD
DO DO DO
5.
689AL(D/EB) DO DO DO DO DO
6.
89VT-182(D/EB) S&S RC500MGB
DO DO 40KA/3S
7.
489BA,BC,AB,AC(S/EB) DO DO DO DO DO
8.
289BA,BB(S/EB) DO DO DO DO DO
9.
289BA,BB(S/EB) MULLER&CO
………. DO DO DO
10.
189BT(D/EB) DO ……….. DO DO DO
• Isolators(220kV)
SR.NO. I.D.NO. MAKE TYPE RATING E/B MECHANISM STC 1. 2489CC S&S RC500 2000 DEB MOTOR 40KA/3S 2. 2489CA S&S RC500 2000 SEB MOTOR 40KA/3S 3. 2489CA
AS&S RC500 2000 SEB MOTOR 40KA/3S
4. 2389CC S&S RC500 2000 DEB MOTOR 40KA/3S 5. 2389CA S&S RC500 2000 SEB MOTOR 40KA/3S 6. 2289CB SE RC500 2000 SEB MOTOR 400KA/3S 7. 2389CD S&S RC500 2000 W/EB MOTOR 40KA/1S 8. 2289CC SE RC500 2000 DEB MOTOR 40KA/3S 9. 2289CB S&S RC500 2000 D/OEB MOTOR 40KA/1S 10. 89VTF UNISO RC500 2000 SEB MOTOR 40KA/3S 11. 2289DV OBLUM 220ABSA2 8000 DEB MANUAL 20KA/1S 12. 2289DA OBLUM 220ABSA2 8000 DEB MANUAL 20KA/1S 13. 2289DC OBLUM 220ABSA2 8000 SEB MANUAL 20KA/1S 14. 2189DA OBLUM 220ABSA2 8000 D/OEB MANUAL 20KA/1S 15. 2189DC OBLUM 220ABSA2 8000 D/OEB MANUAL 20KA/1S 16. 2089DB UNISO 220ABSA2 8000 SEB MANUAL 20KA/1S 17. 2089DC UNISO 220ABSA2 8000 SEB MANUAL 20KA/1S 18. 2089DD SE 22ABSD2 8000 W/OEB MANUAL 20KA/1S 19. 2089CC SE DB 2000 W/OEB MOTOR 40KA/1S 20.. 1889CC S&S DB 2000 W/OEB MOTOR 40KA/1S 21. 1889CA ELECTRONICS DB 2000 DEB MOTOR 40KA/3S 22. 1889CB ELECTRONICS RC500 2000 W/DEB MOTOR 40KA/1S 23. 1889CD ELECTRONICS RC500 2000 SEB MOTOR 40KA/1S 24. 1889 ELECTRONICS RC500 2000 W/DEB MOTOR 40KA/1S 25. 1889 ELECTRONICS RC500 2000 W/DEB MOTOR …………. 26. 1889CC HIVELM RC500 800 W/DEB MOTOR …………. 27. 1889CB HIVELM RC500 800 SEB MOTOR …………. 28. 1889CA HIVELM RC500 800 W/DEB MOTOR …………. 29. 1789DA AMEL RC500 800 W/DEB MOTOR …………. 30. 1789DB HIVELM HPPR-
SHME3800 W/DEB MOTOR ………….
31. 1789DC HLM HPS 800 W/DEB MOTOR …………. 32. 1689GG SE HPS 2000 W/DEB MOTOR …………. 33. 1689GF SE HPS 2000 SEB MOTOR …………. 34 1689CE S&S RC500 2000 SEB MOTOR …………. 35 1689CC S&S RC500 2000 SEB MOTOR …………. 36. 1689DB S&S RC500 2000 SEB MOTOR 40KA/3S 37. 1689DD S&S RC500 2000 SEB MOTOR 40KA/3S
TRANSFORMER:
A transformer is a static electrical device that transfers energy by inductive coupling between its
winding circuits. A varying current in the primary winding creates a varying magnetic flux in the
transformer's core and thus a varying magnetic flux through the secondary winding. This varying
magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding.
The transformer is based on two principles: first, that an electric current can produce a magnetic
field and second that a changing magnetic field within a coil of wire induces a voltage across the
ends of the coil (electromagnetic induction). Changing the current in the primary coil changes
the magnetic flux that is developed. The changing magnetic flux induces a voltage in the
secondary coil.
TYPES OF TRANSFORMER :
1.Autotransformer: Transformer in which part of the winding is common to both primary and
secondary circuits.
2.Capacitor voltage transformer: Transformer in which capacitor divider is used to reduce
high voltage before application to the primary winding.
3.Phase angle regulating transformer: A specialized transformer used to control the flow of
real power on three-phase electricity transmission networks.
4.Scott-T transformer: Transformer used for phase transformation from three-phase to two-
phase and vice versa.
5.Polyphase transformer: Any transformer with more than one phase.
6.Grounding transformer: Transformer used for grounding three-phase circuits to create a
neutral in a three wire system, using a wye-delta transformer,[76][81] or more commonly, a
zigzag grounding winding.
7.Leakage transformer: Transformer that has loosely coupled windings.
8.Resonant transformer: Transformer that uses resonance to generate a high secondary voltage.
9.Audio transformer: Transformer used in audio equipment.
10.Output transformer: Transformer used to match the output of a valve amplifier to its load.
11.Instrument transformer: Potential or current transformer used to accurately and safely
represent voltage, current or phase position of high voltage or high power circuits.
BUS BARS:
There are several ways in which the switching equipment can be connected in the electrical layout of substation in a distribution system. The selection of the scheme is in general affected by following aspects.
• Degree of flexibility of operations desired.
• Importance of load and local condition freedom from total shutdown and its period desired.
• Economic consideration, availability and cost.
• Technical consideration.
• Maintenance, safety of personnel.
• Simplicity
• Provision of extension.
• Protective Zones.
With these basic requirements, there are several combinations such as
• Single bus – bar arrangement
• Duplicate bus- bar arrangement
• Ring bus
• One & a half breaker arrangement
• Mesh arrangement
• Sectionalization of bus
Of this arrangement single bus bar arrangement is employed at 400 KV GSS, Heerapura. In single bus bar arrangement bus bar is split into sections by means of a bus sectionalizer. Single bus bar is easier to use, readily is less (equipment, site procedure, understood by operators, requires less maintenance, spares holding and space). Typical installation consist of basic cubicle types, that can be combined together to form the required switgear.
CIRCUIT BREAKER:
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 interrupt current flow. Unlike a fuse, which operates once and then must be
replaced, a circuit breaker can be reset (either manually or automatically) to resume normal
operation. Circuit breakers are made in varying sizes, from small devices that protect an
individual household appliance up to large switchgear designed to protect high-voltage circuits
feeding an entire city.
Types of circuit breaker:
1.Oil circuit breaker
2.Air blast circuit breaker
3.SF6 circuit breaker
4.Vaccum circuit breaker
5.Water circuit breaker
6.Air break circuit breaker
Generally SF6 circuit breakers are used on 400KV GSS.
SF6 Circuit Breaker:SF6 circuit breakers work through arc interruption. When electrical
current exceeds a certain level (called a rating), the breaker will trip and contacts within the
circuit breaker.
As the breaker is tripped, a magnetic coil is beneath it and as the movable contact falls into the
coil the arc is elongated in a spiral caused by the magnetic coil until the SF6.
Several Characteristics of SF6 circuit breakers can explain their success:
• Simplicity of the interrupting chamber which does not need an auxiliary
breaking chamber.
• Autonomy provided by the puffer technique.
• The possibility to obtain the highest performance, up to 63 kA, with a reduced
number of interrupting chambers.
• Short break time of 2 to 2.5 cycles.
• High electrical endurance, allowing at least 25 years of operation without
reconditioning.
• Possible compact solutions when used for gas insulated switchgear or hybrid
switchgear.
LIGHTENING ARRESTOR : A protective device for electrical equipment that reduces excessive voltage resulting from
lightning to a safe level by grounding the discharge.A device designed to protect electrical
equipment from high transient voltage and to limit the duration and frequency the amplitude of
follow-current. Surge arrester are usually connected the electrical conductors of a network and
earth though they may.
Types of Lighting Arrester:
Originally, three types of surge arresters. They are:
1. Expulsion type: This type of arrester is also called ‘protector tube’ and is commonly used on
system operating at voltages up to 33kV. It essentially consists of a rod gap AA’ in series with
the protector tube. The upper electrode of protector tube is connected to rod gap and the lower
electrode to the earth.
2. Valve Type Arrester: Valve type arresters incorporate non linear resistors and are extensively
used on systems, operating at high voltages. It consists of two assemblies (i) series spark gaps
and (ii) non-linear resistor discs in series.
3. Gapless metal-oxide type: The gapless metal-oxide type arresters are the most widely used
today. The metal oxide lightning arrester is the most advanced over-voltage protector. It is
widely used as protective devices against switching and lightning over voltages in power
electrical systems such as power transformers, distributors, generators, compensation capacitors.
CHARACTERISTICS OF LIGHTENING ARRESTOR:-
STABILITY: -It should remain in operation during normal conditions even under polluted
atmosphere.
RESPONSE:-Protective device should have means of sensing the transient appearing across its
terminals very quickly.
PROTECTION:-After passes the surge current the power frequency current which is called
“power flow current” through the arrestor
ISOLATOR:
Isolator is a mechanical switch which isolates a part of circuit from system as when required.
Electrical isolators separate a part of the system from rest for safe maintenance works.
So definition of isolator can be rewritten as Isolator is a manually operated mechanical switch
which separates a part of the electrical power system normally at off load condition.
Depending upon the position in power system, the isolators can be categorized as:
Bus side isolator – the isolator is directly connected with main bus
Line side isolator – the isolator is situated at line side of any feeder
Transfer bus side isolator – the isolator is directly connected with transfer bus.
Types of Electrical Isolators:
There are different types of isolators available depending upon system requirement such as:
1. Double Break Isolator
2.Single Break Isolator
3.Pantograph type Isolator
400 KV SIDE ISOLATORS RATINGS:-
• Operating Voltage: 400kV
• Current Capacity : 2000A
• Frequency: 50 Hz
• Operator Motor: 415V ac
• The isolator used is a centre break, off load type isolator
220 KV SIDE ISOLATORS RATINGS:-
• Type: HCB
• Voltage: 220 kV
• Frequency: 50Hz
• Operating motor voltage: 415 V
• Control Voltage: 220V
CURRENT TRANSFORMER:
A current transformer (CT) is used for measurement of alternating electric currents. Current
transformers, together with voltage transformers (VT) (potential transformers (PT)), are known
as instrument transformers. When current in a circuit is too high to directly apply to measuring
instruments, a current transformer produces a reduced current accurately proportional to the
current in the circuit, which can be conveniently connected to measuring and recording
instruments. A current transformer also isolates the measuring instruments from what may be
very high voltage in the monitored circuit. Current transformers are commonly used in metering
and protective relays in the electrical power industry.
The accuracy of a CT is directly related to a number of factors including:
1.Burden
2.Burden class/saturation class
3.Rating factor
4.Load
5.External electromagnetic fields
6.Temperature
7.Physical configuration.
8.The selected tap, for multi-ratio CTs.
A Current Transformer
On construction basis that the current transformers may be divided as:
Bar type C.T.:-
A current transformer in which the primary winding consist of a bar of
suitable size and material forming an integral part of transformer. For large primary current the
bar type construction is ideal because it can meet with the burden and accuracy requirement and
the same time can have high thermal and dynamic short time factors. This type of construction is
very sturdy. This may be further sub-divided.
• Separately mounted type
• Bushing type
Wound Type C.T :-
A current transformer having a primary winding of more than one full turn
wound on core. Where the primary currents are low on the burden and accuracy requirements
are high. Primary winding consist of a number of turns normally not exceeding 5. The primary
number of turns depends on the primary current. The greater the number of turns lesser the
thermal and dynamic short time current factors.
The use of one of the other is determined by the rated current of the apparatus and the rated
burden required.
Selection of C.T.:-The following points need to be considered while selecting a C.T.
• Type.
• Number of Secondary.
• Accuracy class of each secondary.
• Rated burden.
• Accuracy limit factor.
• Short time current rating.
CAPACITIVE VOLTAGE TRANSFORMER (CVT):
A capacitor voltage transformer (CVT), or capacitance coupled voltage transformer (CCVT) is a
transformer used in power systems to step down extra high voltage signals and provide a low
voltage signal, for measurement or to operate a protective relay. In its most basic form the device
consists of three parts: two capacitors across which the transmission line signal is split, an
inductive element to tune the device to the line frequency, and a transformer to isolate and
further step down the voltage for the instrumentation or protective relay. The tuning of the
divider to the line frequency makes the overall division ratio less sensitive to changes in the
burden of the connected metering or protection devices.
The device has at least four terminals: a terminal for connection to the high voltage signal, a
ground terminal, and two secondary terminals which connect to the instrumentation or protective
relay. CVTs are typically single-phase devices used for measuring voltages in excess of one
hundred kilovolts where the use of wound primary voltage transformers would be uneconomical.
In practice, capacitor C1 is often constructed as a stack of smaller capacitors connected in series.
This provides a large voltage drop across C1 and a relatively small voltage drop across C2.
The CVT is also useful in communication systems. CVTs in combination with wave traps are
used for filtering high frequency communication signals from power frequency. [2] This forms a
carrier communication network throughout the transmission network.
A Capacitive Voltage Transformer
WAVE TRAP:
Wave Trap is the instrument which used to reduce the corona loss in transmission line in power
system and in this a parallel tuned inductor -capacitor tank circuit made to be resonant at the
desire communication it effort to utilize the same transmission between two substations for the
purpose of communication. Wave trap is a parallel tuned inductor - capacitor 'tank' circuit made
to be resonant at the desired communication frequency.
It is the effort to utilize the same transmission line between two substation for the purpose of
communications.
At this communication frequency the tank circuit provides high impedance and does not allow
to pass through them & onto the substation bus & into transformers.
It is used to trap the communication signals & send PLCC room through CVT.
Rejection filters are known as the line traps consisting of a parallel resonant
circuit ( L and C in parallel) tuned to the carrier frequency are connected in series
at each and of the protected line such a circuit offer high impedance to the flow of
carrier frequency current thus preventing the dissipation. The carrier current used
for PLC Communication have to be prevented from entering the power equipments
such as attenuation or even complete loss of communication signals. For this
purpose wave trap or line trap are used between transmission line and power
station equipment to-
Avoid carrier power dissipation in the power plant reduce cross talks with other
PLC Circuits connected to the same power station.
Ensure proper operating conditions and signal levels at the PLC transmit
receive equipment irrespective of switching conditions of the power circuit and
equipments in the stations.
Line Matching Filter & Protective Equipments
For matching the transmitter and receiver unit to coupling capacitor and power line
matching filters are provided. These flitters normally have air corral transformers
with capacitor assumed.
The matching transformer is insulated for 7-10 KV between the two windings and
perform two functions. Firstly, it isolates the communication equipment from the
power line. Secondly, it serves to match .
Figure-4.1 Line Matching Filter & Protective Equipments
Transmitter
The transmitter consists of an oscillator and a amplifier. The oscillator generates
a frequency signal with in 50 to 500 HZ frequency bands the transmitter is
provided so that it modulates the carrier with protective signal. The modulation
process usually involves taking one half cycle of 50 HZ signal and using this to
create block to carrier.
Receivers
The receivers usually consist of and alternate matching transformer band pass
filter and amplifier detector.
The amplifier detector converts a small incoming signal in to a signal capable of
operating a relatively intensive carrier receiver relay. The transmitter and receiver
at the two ends of protected each corresponds to local as far as transmitting.
RELAYS:
A relay is an electrically operated switch. Many relays use an electromagnet to operate a
switching mechanism mechanically, but other operating principles are also used. Relays are used
where it is necessary to control a circuit by a low-power signal (with complete electrical isolation
between control and controlled circuits), or where several circuits must be controlled by one
signal. The first relays were used in long distance telegraph circuits, repeating the signal coming
in from one circuit and re-transmitting it to another. Relays were used extensively in telephone
exchanges and early computers to perform logical operations.
1. Buchholz relay
It is a safety device sensing the accumulation of gas in large oil-filled transformer which will
alarm on slow accumulation of gas or shut down the transformer if gas is produced rapidly in the
transformer oil.
2.Overload protective relay
Electric motors need overcurrent protection to prevent damage from over-loading the motor, or
to protect against short circuits in connecting cables or internal faults in the motor windings .The
overload sensing devices are a form of heat operated relay where a coil heats a bimetallic stripor
where a solder pot melts, releasing a spring to operate auxiliary contacts. These auxiliary
contacts are in series with the coil. If the overload senses excess current in the load, the coil is
de-energized.
Electronic overload protection relays measure motor current and can estimate motor winding
temperature using a "thermal model" of the motor armature system that can be set to provide
more accurate motor protection. Some motor protection relays include temperature detector
inputs for direct measurement from a thermocouple or resistance thermometer sensor embedded
in the winding.
The purpose of protective relay and protective system is to operate the correct
CB‘s as to disconnect only the faulty equipment from the system as quickly as
possible. Thus minimizes the trouble caused by fault by they do occur. The
protective relay does not operate possibility of the fault on the system. Their active
starts only after the faults have occurred. It could be idea led if the protection could
anticipate and peasant faults because it is impossible to except where original case
of fault create some effects which can operate a protective relay. These are two
groups of protective relay.
1. Primary relaying equipments.
2. Back-up relaying equipments.
Primary relaying is the first line of difference whereas back up protection
relaying works. Only when the primary relaying equipments fails and also back up
relays are slow in motion condition. Another job of back relay is to act as primary
relay in case of where this is out work.
Relay must operate when it is required. Since relay remains ideal. Most of the
time proper maintenance also plays important role in improving reliability. Relay
should select fault region and isolate that section from circuit. It should also
operate required speed. It should neither be slow which may not result in damage
to the equipment nor it should too fast which may result undesired operation during
transient faults and should be sensitive to faults.
OPERATION:-
The protective relay serves for preventing tap changers and transformer from
being damage which is the part of delivering the protective relay as to be
connected in away that transformer immediately switched off captions oil
immersed transformer. Transformer break down are always precede by more or
less violent generation of gas. A broking joints produce local arc and vaporize in
the vicinity. As earth faults has the some results sudden short circuit rapidly
increased the temperature of the winding particularly the inner layer and packed oil
in vaporize. Discharge due to insulation weaken i.e. by the dehydration of the oil
produce local heating and generate gas. The generation of oil vapour or gas in
utilize to actuate a relay the relay is arranged between the transformer tank and the
separate oil conservator. The vessel is normally is full of oil. It contains two floats
if the gas bubbles are generated in transformer due to faults. They will be rise and
transfers the conservator and will trap in the upper part of the relay chamber.
Thereby displacing the oil and lowering the faults. This sinks and eventually closes
and external contacts which operates an alarm over other protection and flashover
at the bushing are not at adequately covered by other protective scheme also unless
it improves ground.
The differential scheme detects such faults and also on the leads between CTs
are power transformer provided ct’s are not mounted separately on transformer
bushing. In service internal faults operate when the relay is energizes. The
protective relay reenergized only by oil flow from the tap changer heat to the
conservator. The oil flow operates the flap value which is trapped into the “off”
position by timing mechanism. Thus the trapping switch is energized the CB’s are
operated the transformer off the line.
OIL TESTING LAB:
A)Oil Sampling:
Oil sampling is a procedure for collecting a volume of fluid from lubricated or hydraulic
machinery for the purpose of oil analysis. Much like collecting forensic evidence at a crime
scene, when collecting an oil sample, it is important to ensure that procedures are used to
minimize disturbance of the sample during and after the sampling process. Oil samples are
typically drawn into a small, clean bottle which is sealed and sent to a laboratory for analysis.
B)Oil analysis:
Oil analysis (OA) is the laboratory analysis of a lubricant’s properties, suspended contaminants,
and wears debris. OA is performed during routine preventive maintenance to provide meaningful
and accurate information on lubricant and machine condition. By tracking oil analysis sample
results over the life of a particular machine, trends can be established which can help eliminate
costly repairs. The study of wear in machinery is called tribology.Tribologistsoften perform or
interpret oil analysis data.
OA can be divided into three categories:
1. Analysis of oil properties including those of the base oil and its additives
2. Analysis of contaminants
3. Analysis of wear debris from machinery
EARTHING
Earthing is the provision of a surface under the sub station, which has a
uniform potential as nearly as zero or equal to Absolute Earth potential. The
provision of an earthing system for an electric system is necessary by the following
reason.
1. In the event of over voltage on the system due to lighting discharge or other
system fault. These parts of equipment which are normally dead as for as voltage,
are concerned do not attain dangerously high potential.
2. In a three phase, circuit the neutral of the system is earthed in order to stabilize
the potential of circuit with respect to earth.
The resistance of earthing system is depending on shape and material of earth
electrode used.
The earthing is of two principal types :-
Neutral Earthing
Equipment Body Earthing
Neutral Earthing :-
Neutral Earthing also known as System Neutral Earthing (or Grounding)
means connecting the neutral point i.e. the star point of generator,transformer etc.
to earth. In rotating machines, generator, transformer circuit etc., the neutral point
is always connected to earth either directly or through a reactance. The neutral
point is usually available at every voltage level from generator or transformer
neutral. If neutral point is not available, then the most common method used is
using a Zigzag transformer. Such a transformer has no secondary. Each phase of
primary has two equal parts. There are 3 limbs and each limb has two winding,
providing flux density under normal condition. Since the fluxes are opposite, the
transformer takes very small magnetizing current under normal conditions. During
fault, the circuit is primary side,
which provides very less impedance to the current. The grounding
transformers are short time rating. Their size is almost one tenth as compared to
power transformer.
Electrical Earthing:-
Electrical Earthing is different from neutral earthing. During fault condition,
the metallic parts of an electrical installation which do not carry current under
normal conditions, may attain high potential with respect to ground. As human
body can tolerate only I=0.165A/T current for a given time t so to ensure safety we
connect such metallic parts to earth by means of Earthing system ,which comprises
of electrical conductor to send fault current to earth. The conductor used is
generally in the form of rods, plates, pipes etc.
Earthing system ensures safety in following ways :-
1. The potential of earthen body does not reach dangerously high value about earth,
since it is connected to earth.
2. Earth fault current flows through earthing and readily causes the operation of
fuse or an earth relay.
Merits of neutral Earthing:-
1. Arcing grounding is reduced.
2. Voltage of heating with respect to earth remains at harmless value they don't
increase to root 3 times of normal value.
3. Suitable neutral point.
4. The earth fault relaying is relatively simple useful amount of earth fault current
is available to operate earth fault relay.
5. The over voltage due to lightening are discharged to earth.
6. Improved service reliability due to limitation of arcing ground and improved of
unnecessary fringing of CB.
At GSS the neutral point of power transformer is connected solidly to earth
generally the earth connection are provided which leads reliability.
Power Line Carrier Communication :-
Power Line Carrier Communication (PLCC) provides for signal transmission
down transmission line conductors or insulated ground wires. Protection signaling,
speech and data transmission for system operation and control, management
information systems etc. are the main needs which are met by PLCC.
PLCC is the most economical and reliable method of communication because
of the higher mechanical strength and insulation level of high voltage power line
which contribute to the increased reliability of communication and lower
attenuation over the larger distances involves.
High frequency signals in the range of 50 KHZ to 400 KHZ commonly known
as the carrier signal and to result it with the protected section of line suitable
coupling apparatus and line traps are employed at both ends of the protected
section. Here in Sanganer and also in other sub-station this system is used. The
main application of power line carrier has been from the purpose of supervisory
control telephone communication, telemetering and relaying.
PLCC Equipment
The essential units of power line carrier equipment consists of :-
a. Wave trap
b. Coupling Capacitor
c. LMU and protective equipments.
MERITS AND DEMRITS OF PLCC
Merits
The severity that a power line can withstand is much more than that odd
communication line due to higher mechanical strength of transmission line power
lines generally provide the shortest route between the Power Station and the
Receiving Stations.
The carrier signals suffer less attenuation, owing to large cross sectional area of
power line
Larger spacing between conductors reduces the capacitances which results in lesser
attenuation of higher frequencies.
Large spacing also reduces the cross talk to a certain extent.
The construction of a separate communication line is avoided.
Demerits
Utmost care is required to safeguard the carrier equipment and persons using them
against high voltage and currents on the line.
Noise introduced by power line is far more than in the case of communication line.
This is due to the discharge across insulators and corona etc.
Induced voltage surges in the power line may affect the connected carrier
equipment.
CONTROL ROOM
INTRODUCTION:- In Heerapura G.S.S. not only remote control carry the appropriate mean by which circuit breaker may be open or close but also indicating device , indicating lamps , isolating switches, protective relays , secondary circuit and wires are located here and most important “no load tap changer” for transformer is available. There is panel for synchronizing. Different panel are located at different stages and on each control panel switch is provided on the board. Colors of signals are synchronized as follows:
• Red – For circuit breaker or isolator switch is in closed position.
• Green - For circuit breaker is in open condition.
• Amber – Indicates abnormal condition.
There are different relays are located.
CONCLUSION
The training at grid substation was very helpful. It has improved my
theoretical concepts of electrical power transmission and distribution. Protection
of various apparatus was a great thing. Maintenance of transformer, circuit
breaker, isolator, insulator, bus bar etc was observable.
I had a chance to see the remote control of the equipments from control
room itself, which was very interesting.
So the training was more than hope to me and helped me to understand
about power system more.
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