Contents A. 220/132 KV & 400 KV SUB-STATION

1. Definition 2. Introduction

B. About the substation

B.1 Construction –Site Selection & Layout

C. Equipment in a 220KV & 4 0 0 K V Substation

1) Bus- bar 2) Insulators

a) Pin type insulators

b) Suspension type insulators

c) Strain type insulators

3) Isolating Switches 4) Circuit breaker

a) SF6 Circuit break er

b) Air Circuit breaker

c) Oil Circuit breaker

5) Protective relay 6) Instrument Transformer

i . Current Transf ormer

ii . Voltage Transformer

7) Metering and Indicating Instrument

8) Miscellaneous equipment

9) Power Transformer

a) autotransformer

10) Lightening arrestors

11) Line isolator

12) Conductors

I. Bundled conductors

II. Ground wires

13) Wave trap

14)Communication in power system

A) Telecommunication

I. Microwave Communication System

II. Fibre Optic Communication System

III. Power Line Carrier Communication System

B) SCADA system

A .1) Definit ion of sub - s t a t i o n : -

“The assembly of apparatus used to change some

characteristics (e.g. Voltage ac t o d c freq. p.f. etc) of

electric supply is called sub-station”.

A . 2 ) Introduction : - The present day electrical power system is a.c. i.e. electric

power is generated, transmitted and distributed in the

form of Alternating current. The electric power is produce

at the power station, which are located at favorable places,

generally quite away from the consumers. It is delivered to

the consumer through a large network of transmission and

distribution. At many place in the line of power system, it

may be desirable and necessary to change some

characteristic (e.g. Voltage, ac to dc, frequency p.f. etc.) of

electric supply. This is accomplished by suitable apparatus

called sub-station for example, generation voltage (11KVor

6.6 KV) at the power station is stepped up to high voltage

(Say220KVt o 1 3 2 KV) for transmission of electric power.

Similarly near the consumer‟s localities, the voltage may

have to be stepped down to utilization level. This job is again

accomplished by suitable apparatus called sub-station.

B ) A b o u t t h e s u b s t a t i o n : - Panki Thermal Power Station is located at Panki in Kanpur district in the

Indian state of Uttar pradesh , about 16 km from Kanpur . It has an installed

capicity of 220 Mega Watts.

The Central government has commissioned a 210 MW unit at Panki Power

Station.

At PTPS, 2x110 MW BHEL made coal fired turbo generating units are

presently in operation. These 110 MW machines were manufactured,

supplied and commissioned by M/s BHEL, during 1976-77 with features of

reheating and regenerative feed heating. The Steam Generator is balanced

draft, radiant, dry bottom, single drum, natural circulation, vertical water

tube type construction with skin casing and semi direct type of firing

system. Apart from the above 110 MW units, 2x32 MW Russia made turbo

generating units were also installed at PTPS in 1967-68, however these units

have become obsolete and permanently closed now after running for about

30 years.

The most important of any substation is the grounding

(Earthing System) of the instruments, transfor mers etc. used in

the substation for the safety of the operation personnel as well as

for proper system operation and performance of the protective

devices.

An earthes system comprising of an earthing mat buried at a

suitable depth below ground and supplemented with ground rods

at suitable points is provided in the substations. These ground the

extra high voltage to the ground. As it is dangerous to us to go

near the instrument without proper earth. If the instruments

are not ground properly they may give a huge shock to anyone

who would stay near it and also it is dangerous for the costly

instrument as they may get damaged by this high voltage.

B . 1 ) S i t e S e l e c t i o n & L a y o u t 2 2 0 K V & 4 0 0 K V S u b s t a t i o n : -

2 2 0 K V S u b -Station forms an important link between

Transmission network and Distribution network. It has a

vital influence of reliability of service. Apart from

ensuring efficient transmission and Distribution of

power, the sub-station configuration should be such that

it enables easy maintenance of equipment and minimum

interruptions in power supply. Sub-Station is

constructed as near as possible to the load center. The

voltage level of power transmission is decided on the

quantum of power to be transmitted to the load center.

Selection of s ite :-

Main points to be considered while selecting the site for Grid

Su b-Station are as follows:

i) The site chosen should be as near to the load center as possible.

ii) It should be easily approachable by road or rail for

transportation of equipments.

iii) Land should be fairly leveled to minimize development cost.

iv) Source of water should be as near to the site as possible. This is

because water is required for various construction activities

(especially civil works), earthing and for drinking purposes etc.

v) T h e s u b -station site should be as near to the town / city but

should be clear of public places, aerodromes, and Military / police

installations.

vi) The land should be have sufficient ground area to accommodate

substation equipments, buildings, staff quarters, space for storage

of material, such as store yards and store sheds etc. with roads

and space for future expansion.

vii) Set back distances from various roads such as National

Highways, State Highways should be observed as per the regulations

in force.

Viii While selecting the land for the Substation preference to be

given to the Govt. land over private land.

ix) The land should not have water logging problem.

x) Far away from obstructions, to permit easy and safe approach

/ termination of high voltage overhead transmission lines.

B . 2 ) E q u i p m e n t i n 2 2 0 K V & 4 0 0 K V S u b - St at ion : -

The equipment required for a transformer Sub-Station

depends upon the type of Sub-Station, Service

requirement and the degree of protection desired.

220K V EHV Sub-Station has the following major

equipments.

1 ) B u s - b a r :-

When a no. of lines operating at the same voltage have to

be directly connected electrically, bus-bar are used, it is made up of

copper or aluminum bars (generally of rectangular X-Section) and

operate at constant voltage.

The bus is a line in which the incoming feeders come into a nd

get into the instruments for further step up or step down. The first

bus is used for putting the incoming feeders inLAsingleline.There

may be double line in the bus so that if any fault occurs in the

one the other can still havethe current and the supply will not

stop. The two lines in the bus are separated by a little

distanceby a Conductor having a connector between them. This is

so that one can work at a time and theother works only if the first

is having any fault.

Bus bars:-

b

2 ) I n s u l a t o r s : -

The insulator serves two purpose. They support the conductor (or

bus bar) and confine the current to the conductor.

The most commonly used material for the manufactures of

insulators is porcelain. There are several type of insulator (i.e.

pine type, suspension type etc.) and there used in Su b-Station will

depend upon the service requirement.

Ceramic insulators

Glass insulators

a) PIN INSULATOR:- Offering an extensive range of 11KV, 22KV and 33 KV pin insulators that

are fabricated from high grade raw material as per the demand of various

electrical industries. Pin insulators it is supported on a pin and provide a

means to hold the insulator to the pin and provide a means to secure the

conductor to the insulator. We offer these pin insulators at varied standard

and customized specifications at cost efficient rates.

11 KV PIN INSULATORS

Our range of 11KV pin insulators encompasses RR / PN / 1105, RR / PN /

1103, RR / PN / 1104 and RR / PN / 1102 which are available in different

technical specifications. These highly efficient pin insulators are less

vulnerable to damage and can normally withstand the line voltage for a

considerable time with ease.

RR / PN / 1105 RR / PN / 1103

RR / PN / 1104

RR / PN / 1102

VOLTAGE CLASS 22 KV AND 33 KV

Pin insulators in voltage class 22KV and 33KV have found application in

varied industries and are widely used in low cost distribution lines. Our

pin insulator is designed to secure the conductor to itself. Top quality pin

insulator includes RR / PN / 2201, RR / PN / 3301, RR / 004 / 22 PIN and

RR / 003 / 33 PIN.

RR / PN / 2201 RR / PN / 3301

RR / 004 / 22 PIN RR / 003 / 33 PIN

b) SUSPENSION INSULATORS:-

Suspension insulators are made of multiple units, with the number of unit

insulator disks increasing at higher voltages. The number of disks is

chosen based on line voltage, lightning withstand requirement, altitude,

and environmental factors such as fog, pollution, or salt spray. Longer

insulators, with longer creepage distance for leakage current, are required

in these cases.

Suspension type insulators:-

C) STRAIN INSULATORS :-

A strain insulator is an insulator that provides both large electrical

insulation and a large load-bearing capacity. A typical strain insulator is a

piece of glass or porcelain that is shaped to accommodate two cables or a

cable shoe and the supporting hardware on the support structure (hook

eye, or eyelet on a steel pole/tower). The shape of the insulator maximizes

the distance between the cables while also maximizing the load-bearing

transfer capacity of the insulator. When the line voltage requires more

insulation than a single insulator can supply, strain insulators are used in

series: A set of insulators are connected to each other using special

hardware. The series can support the same strain as a single insulator, but

the series provides a much higher effective insulation.

Strain type insulators:-

3) I s o l a t i n g S w i t c h e s : -

I n S u b - Station, it is often desired to disconnect a part of the

system for general maintenance and repairs. This is accomplished by

an isolating switchor isolator. An isolator is essentially a kniff

Switch and is design to often open a circuit under no load, in other

words, isolator Switches are operate only when the line is which they

are connected carry no load. For example, consider that the isolator

are connected on both side of a cut breaker, if the isolators are to be

opened, the C.B. must be opened first .

3 pole switch:-

4 ) C i r c u i t b r e a k e r : -

A circuit breaker is an equipment, which can open or close a

circuit under normal as well as fault condition. These circuit

breaker breaks for a fault which can damage other instrument in the

station.It is so designed that it can be operated manually (or by

remote control) under normal conditions and automatically under

fault condition.There are mainly two types of circuit breakers

used for any substations. They are

(a) SF6 circuit breakers;

(b) air circuit breakers;

(c) oil circuit breakers.

For the latter operation a relay wt. is used with a C.B. generally bulk

oil C.B. are used for voltage upto 66 KV while for high voltage low oil

& SF6 C.B. are used. For still higher voltage, air blast vacuum or

SF6 cut breaker are used.

(a) SF6 CIRCUIT BREAKER :-

The use of SF6 circuit breaker is mainly in the substations

which are having high input kv input, say above 220kv and more.

The gas is put inside the circuit breaker by force i .e. under high

pressure.

When if the gas gets decreases there is a motor connected to the

circuit breaker. The motor starts operating if the gas went lower

than 20.8 bar. There is a meter connected to the breaker so that it

can be manually seen if the gas goes low. The circuit breaker uses

the SF6 gas to reduce the torque produce in it due to any faul t in

the line. The circuit breaker has a direct link with the

instruments in the station, when any fault occur alarm bell rings.

SF6 ckt breaker diagram:-

(b) AIR CIRCUIT BREAKER :-

These type of breakers employ „air blast‟ as the quenching medium.The

contacts are opened by air blast produced by the opening of blast valve.The

air blast cools the arc and sweeps away the arcing products to the

atmosphere.This rapidly increases the dielectric strength of the medium

between contacts and prevents from re-establishing the arc.Consequently

the arc is extinguished and the flow of current is interrupted.

(c ) OIL CIRCUIT BREAKER :-

A high-voltage AC electrical switch whose main contacts are located in a

space filled with mineral (transformer) oil. Upon interruption of the

electric circuit, an electric arc forms between the contacts of the circuit

breaker. Because of the high temperature of the arc the oil is evaporated

rapidly and oil vapors are partially decomposed, liberating ethylene,

methane, and other gases. A gas bubble is formed in the arcing zone; the

pressure in the bubble may be as high as several dozen mega newtons per

sq m. The arc is then extinguished, both because of its elongation upon

parting of contacts and because of intensive cooling by the gases and oil

vapor.

Low oil ckt breaker diagram :-

5) P r o t e c t i v e r e l a y :-

A p r o t e c t i v e relay is a device that detects the fault and initiates

the operation of the C.B. to isolate the defective element from the

rest of the system”. The relay detects the abnormal condition in the

electrical circuit by constantly measuring the electrical quantities,

which are different under normal and fault condition. The electrical

quantities which may change under fault condition are voltage,

current, frequency and p hase angle. Having detect the fault, the

relay operate to close the trip circuit of C.B.

Relay diagram:-

6 ) Instrument Trasformer: -

The line in Sub-Station operate at high voltage and carry

current of thousands of amperes. The measuring

instrument and protective devices are designed for low

voltage (generally 110V) and current (about 5A). Therefore,

they will not work satisfactory if mounted directly on the

power lines. This difficulty is overcome by installing

Instrument transformer, on the power lines. There are two

types o f instrument transformer.

i ) C u r r e n t Transformer : -

A current transformer is essentially a step-down

transformer which steps-down the current in a known

ratio, the primary of this transformer consist of one or

more turn of thick wire connected in series with the line,

the secondary consist of thick wire connected in series

with line having large number of turn of fine wire and

provides for measuring instrument, and relay a current

which is a constant faction of the current in t h e l i n e .

Current transformers are basically used to take the

readings of the currents entering the substation. This

transformer steps down the current from 800 amps

to1amp. This is done because we have no instrument for

measuring of such a large current. The main use of his

transformer is

(a) distance protection;

(b) backup protection;

(c) measurement.

Current transformer(CT) diagram:-

i i ) V o l t a g e T r a n s f o r m e r : -

It is essentially a step– down transformer and step down the

voltage in known ratio. The primary of these transformer consist

of a large number of turn of finewire connected across the line.

The secondary way consist of a few turns and provides for

measuring instruments and relay a voltage which is known

fraction of the line voltage.

Potential transformer(PT) diagram:-

7 ) Metering and Indicating Instrument :-

There are several metering and indicating Instrument (e.g.

Ammeters, Volt- meters, energy meter etc.) installed in a

Substation to maintain which over the circuit quantities. The

instrument transformer are invariably used with them for

satisfactory operation .

8 ) Miscellaneous equipme nt:-

In addition to above, there may be following equipment in a

Substation :

i ) Fuses

i i ) Carrier - current equipment

i i i ) S u b -Station auxiliary supplies

9) Power Transformer : -

There are three transformers in the incoming feeders so that the

three lines are step down at the same time. In case of a 220KV or

more KV line station auto transformers are used. While in case of

lower KV line such as less than 132KV line double winding

transformers are used.

a) Autotransformer :

Transformer is static equipment which converts electrical energy

from one voltage to another. As the system voltage goes up, the

techniques to be used for the Design, Construction, Installation,

Operation and Maintenance also become more and more critical.

If properc a r e i s exercised in the installation, maintenance and

condition monitoring of the transformer, it can give the user

trouble free service throughout the expected life of equipment

which of the order of 25-35 years. Hence, it is very essential that the

personnel associated with the installation, operation or

maintenance of the transformer is through with the instructions

provided by the manufacture.

Autotransformer taping:-

10) Lightening arrestors:-

Lightening arrestors with earth switch lightening arrestors after

the current transformer are used so as to protect it from

lightening i.e. from high voltage entering into it. This lightening

arrestor has an earth switch, which can directly earth the

lightening. The arrestor works at 30° to 45° angel of

the lightening making a cone. The ear th switch can be operated

manually, by pulling the switch towards ground. This also helps in

breaking the line entering the station. By doing so maintenance

and repair of any instrument can b performed.

Different types of lighning arrestors:-

It is a device used on electrical power systems to protect the

insulation on the system from the damaging effet of

lightning. Metal oxide varistors (MOVs) have been used for power

system protection since the mid 1970s. The typical lightning arrester

also known as surge arrester has a high voltage terminal and a

ground terminal. When a lightning surge or switching surge travels

down the power system to the arrester to the ground.

11) Line isolator :-

The line isolators are used to isolate the high voltage

Flow throughthe line into the bus. This isolator prevents the

instruments to get damaged. It also allows the only needed voltage

andrest is earthed by itself. In electrical engineering, a disconnector or

isolator switch is used to make sure that an electrical circuit can be

completely de-energised for service or maintenance. Such switches are

often found in electrical distribution and industrial applications where

machinery must have its source of driving power removed for adjustment

or repair. High-voltage isolation switches are used in electrical substations

to allow isolation of apparatus such as circuit breakers and transformers,

and transmission lines, for maintenance.

12) Conductors:-

Aluminium conductors reinforced with steel (known as ACSR) are

primarily used for medium and high voltage lines and may also be used for

overhead services to individual customers. Aluminium conductors are

used as it has the advantage of lower resistivity/weight than copper, as well

as being cheaper.

While larger conductors may lose less energy due to lower electrical

resistance, they are more costly than smaller conductors. An optimization

rule called Kelvin's Law states that the optimum size of conductor for a

line is found when the cost of the energy wasted in the conductor is equal

to the annual interest paid on that portion of the line construction cost due

to the size of the conductors. The optimization problem is made more

complex due to additional factors such as varying annual load, varying cost

of installation, and by the fact that only definite discrete sizes of cable are

commonly made.

I. Bundle conductors :-

Bundle conductors are used to reduce corona losses and audible noise.

Bundle conductors consist of several conductor cables connected by non-

conducting spacers. For 220 kV lines, two-conductor bundles are usually

used, for 380 kV lines usually three or even four.

Bundle conductors are used to increase the amount of current that may be

carried in a line. Due to the skin effect, ampacity of conductors is not

proportional to cross section, for the larger sizes. Therefore, bundle

conductors may carry more current for a given weight.

A bundle conductor results in lower reactance, compared to a single

conductor. It reduces corona discharge loss at extra high voltage (EHV)

and interference with communication systems. It also reduces voltage

gradient in that range of voltage.

Double conductors four conductors

II. Ground wires :-

Overhead power lines are often equipped with a ground conductor (shield

wire or overhead earth wire). A ground conductor is a conductor that is

usually grounded (earthed) at the top of the supporting structure to

minimise the likelihood of direct lightning strikes to the phase conductors.

Shield wires on transmission lines may include optical fibers (OPGW),

used for communication and control of the power system.

13) wave trap:-

It is also called "Wave trap". It is connected in series with the power

(transmission) line.It blocks the high frequency carrier waves (24 KHz to

500 KHz) and let power waves (50 Hz - 60 Hz) to pass through. It is

basically an inductor of rating in Milli henry (approx 1 milli Henry for 220

KV 1250 Amp.).

Wave trap diagram:-

14) Communication in Power System

Following are mainly three inter-related areas of functions in UPPTCL for

management of power system:

A) Telecommunication

B) SCADA- Supervisory Control and Data Acquisition System.

A) TELECOMMUNICATION

There are three different types of telecommunication systems in UPPTCL

i.e.

i. Microwave Communication System,

ii. Fibre-optic Communication System,

iii. PLCC-Power Line Carrier Communication.

Voice Frequency (VF) channels of all these systems have been

integrated/interconnected to make a hybrid communication system.

Microwave & Fibre Optic are multi-channels communication systems and

are also called 'Wideband communication system'. PLCC is single channel

communication system. A brief overview of these three types of

telecommunication system of UPPTCL is as below:

I. Microwave Communication System

Microwaves travel in 'Space' and any object in the path can obstruct

communication system. Microwave is called 'line-of-sight' communication

system. As such, its antennas are mounted on high towers so that even

trees should not obstruct path of microwaves. UPPTCL is using frequency

band between 2.3 GHz to 2.5 GHz. The height for antenna are calculated by

taking into account many factors, such as, distance between two locations,

path clearance, height from sea level of these locations, tropical area,

reflection points, and so on. As such, height of towers varies from location

to location. Tower heights at our microwave stations range from 30 to 110

meters. Starting from Muzaffarnagar (220KV substation Nara), in the

north-west, to Rihand (Pipri), in south-east of UP, 33 microwave stations

have been established. A list of microwave stations with height of towers

has been given at the end of this write-up. This covers a route length of

over 1000 Km.

II. Fibre Optic Communication System

It is new communication system and has been introduced in UPPTCL since

2001. Optical fibre cable, in the form of 'Optical Fibre Composite Ground

Wire' (OPGW), has been installed on transmission towers by replacement

of earth wire. Earth wires of following five transmission lines, total route

length of 408 Km., have been replaced:

'Optical Line Terminal Equipment' (OLTE) have been manufactured by

Fujitsu, Japan and have been installed at eight sub-stations (Muradnagar,

Moradabad, C.B.Ganj, Unnao, Panki, Sahupuri, Sarnath & Azamgarh). The

electrical signal of 2Mb/s or 34Mb/s, as the case may be, from OLTE is

connected with Primary Multiplexing equipment supplied by 'Nokia'

Finland. Its NMS provides operational support for the 'Fibre Optic

Transmission System' (FOTS). For testing, commissioning & maintenance

'FLEXR' and 'FLEXR Plus' computer software programmes have been

provided. 'FLEXR' is used for initial settings of OLTEs of fibre optic

network. Similar to microwave NMS, 'FLEXR Plus' helps in remote

diagnosis, operation and maintenance of fibre optic network. For complete

communication control system, a NMS100 system has installed at NRLDC,

New Delhi, which is in position to diagnose faults of whole northern

region.

OPGW has been manufactured by Farukawa, Japan. They have done

replacement work, on live (hot) lines, by using a unique installation

technology. The OPGW in our system has got twelve (12) 'Dual Window

Single Mode' (DWSM) type fibres in it. Optical signals of 1310 or 1550

nanometer (nm) wavelength are being used. Only two fibres are required

for a multi-channel link between two stations. One fibre is used for

transmitting optical signal and second for receiving from other end. In our

system two fibres have been used for 'Normal' communication path and

two fibres for 'protection' path. Fibre optic communication system has got

a wide bandwidth transmission capability. Two fibres are sufficient for

providing more than one lakh telephone channels on both sides. As such, a

high-speed data, containing large volumes of information can be

transmitted at low cost.

III. Power Line Carrier Communication

System

Power Line Carrier Communication (PLCC) is a single channel

communication system in which its channel (300 to 3400 Hz) is divided

into two parts i.e. speech band is generally kept 300 to 2400Hz or 300 to

2000Hz and rest is used as data band. Due to narrow speech band in PLCC,

voice of poor quality is available in comparison to wideband

communication system. In this system, signal travels on the transmission

line from one end to other end. Transmitter output (Radio Frequency

signal) is fed to the transmission line through a Coupling Capacitor or CVT.

RF power output is in frequency band from 70 KHz to 500 KHz. Inductors,

called 'Wave Traps' are used at the ends of the signals. PLCC is also used

for line protection signal. Protection signals are transmitted through PLCC

system for tripping circuit breaker of other end of transmission line.

UPPTCL has a wide network of PLCC links. Presently, its number of PLCC

links are about 550.

Plc block diagram:-

B) SCADA SYSTEM

In SCADA system measured values, i.e. analogue (measured value) data

(MW, MVAR, V, Hz Transformer tap position), and Open/Closed status

information, i.e. digital data (Circuit Breakers/Isolators position i.e. on/off

status), are transmitted through telecommunication channels to respective

sub-LDCs. For this purpose Remote Terminal Units (RTUs) at 400KV,

220KV and few important 132KV sub-stations have been installed. System

values & status information below 132 KV have not been picked up for data

transmission, except for 33KV Bus isolator position and LV side of

generators. Secondary side of Current Transformers (CT) and Potential

Transformer (PT) are connected with 'Transducers'. The output of

transducers is available in dc current form (in the range of 4mA to 20mA).

Analogue to digital converter converts this current into binary pulses.

Different inputs are interleaved in a sequential form and are fed into the

CPU of the RTU. The output of RTU, containing information in the form of

digital pulses, is sent to subLDC through communication links. Depending

upon the type of communication link, the output of RTU is connected,

directly or through Modem, with the communication equipment. At

subLDC end, data received from RTU is fed into the data servers. In

general, a SCADA system consists of a database, displays and supporting

programmes. In UPPTCL, subLDCs use all major functional areas of

SCADA except the 'Supervisory Control/Command' function. The brief

overview of major 'functional areas' of SCADA system is as below:

1. Communications - Sub-LDC's computer communicates with all RTU

stations under its control, through a communication system. RTU polling,

message formatting, polynomial checking and message retransmission on

failure are the activities of 'Communications' functional area.

2. Data Processing - After receipt of data through communication system it is

processed. Data process function has three sub-functions i.e. (i)

Measurements, (ii) Counters and (iii) Indications.

'Measurements' retrieved from a RTU are converted to engineering units

and linearised, if necessary. The measurement are then placed in database

and are checked against various limits which if exceeded generate high or

low limit alarms.

The system has been set-up to collect 'Counters' at regular intervals:

typically 5 or 10 minutes. At the end of the hour the units is transferred

into appropriate hour slot in a 24-hour archive/history.

'Indications' are associated with status changes and protection. For those

statuses that are not classified as 'alarms', logs the change on the

appropriate printer and also enter it into a cyclic event list. For those

statuses, which are defined as an 'alarms' and the indication goes into

alarm, an entry is made into the appropriate alarm list, as well as in the

event list and an audible alarm is generated in the sub-LDC.

3. Alarm/Event Logging - The alarm and event logging facilities are used by

SCADA data processing system. Alarms are grouped into different

categories and are given different priorities. Quality codes are assigned to

the recently received data for any 'limit violation' and 'status changes'.

Alarms are acknowledged from single line diagram (or alarm lists) on

display terminal in LDCs.

4. Manual Entry - There is a provision of manual entry of measured values,

counters and indications for the important sub-station/powerhouse, which

are uncovered by an RTU or some problem is going on in its RTU,

equipment, communication path, etc.

5. Averaging of Measured Values - As an option, the SCADA system supports

averaging of all analogue measurements. Typically, the averaging of

measured values over a period of 15 minutes is stored to provide 24 hours

trend.

6. Historical Data Recording (HDR) - The HDR, i.e. 'archive', subsystem

maintains a history of selected system parameters over a period of time.

These are sampled at a pre-selected interval and are placed in historical

database. At the end of the day, the data is saved for later analysis and for

report generation.

7. Interactive Database Generation - Facilities have been provided in such a

way that an off-line copy of the SCADA database can be modified allowing

the addition of new RTUs, pickup points and communication channels.

8. Supervisory Control/Remote Command - This function enables the issue of

'remote control' commands to the sub-station/powerhouse equipment e.g.

circuit breaker trip command. Though, there is provision of this function

in this system, yet it is not used in U.P. As such, related/associated

equipment have not been ordered.

9. Fail-over - A 'Fail-over' subsystem is also provided to secure and maintain

a database of devices and their backups. The state of the device is

maintained indicating whether it is 'on-line' or 'failed'. There is a 'backup'

system, which maintains database on a backup computer and the system is

duplicated.

SLDC Lucknow has a large and active 'Mimic Board' in its Control room.

This mimic board displays single line diagram of intra State transmission

system i.e. grid network of 400KV, 220KV and important 132KV sub-

stations, transmission lines, thermal & hydro powerhouses. Outgoing

feeders, shown in the mimic board, have 'achieve' (LED display) colored

indications, of three different colors, to show the range of power flow at

any moment i.e. 'Normal', 'Nominal' or 'Maximum' of its line capacity.

UPPTCL's transmission network is expanding rapidly and thereby number

of RTUs is also increasing. For new substations and lines, displays in active

and passive forms are required to be made in the Mimic diagram. But,

Mimic Board has a limitation that it cannot incorporate/add large volume

of displays for substations/power houses/transmission lines in 'active'

form due to space constraint and congestion. Due to this Mimic Board is

going to be supplemented with a Video Projection System (VPS) at SLDC,

Lucknow in near future. Also in SLDC & subLDCs, displays of single line

diagrams of RTU sub-stations/power house are viewed on VDUs of large

size (21").

Transmission & reciver block diagram :-

Scada system diagam:-