Question { Descon, 7087 }

Transformer TTR test procedure

Answer

this is a special test.refer to manufacturer.

Question { L&T, 2785 }

WHAT ARE THE DATAS REQUIRED FOR SCS SIGNAL LIST PREPARATION?

Answer

It depends on your SUB STATION CONTROL SYSTEM (SCS)
supplier and client, and load despatching authority SCADA
system.
Generally Load despatching authority demand:
I) Remote control -on-off control oF CB,STATUS OF
INDICATION,PROTECTION AL+TRIP SIGNALS ,FEED BACK SIGNAL.
OLTC COUNTER,
2) INDICATION - A,V,F,PF, MW,MVAR,

3) METERING IN -OUT MWH,MVARH,

4) sTATUS OF ALL CB,DS,ES, PLC,

5) MAIN BUS ,INCOMMING,OUT GOING.

6)SUB STATION dc VOLTAGE, UPS ALARM

7)FAULT LOGGER REPEATITION SIGNAL.

THIS IS A VERY EXPENSIVE TASK. SCS SUPPLIER MUST FINALIZE
CLEARLY,AFTER FINALIZING SIGNAL SUCH ,AS DI,DO,AI,AO ,LOGIC
SEQUENCES, SHALL PROCEED HIS WORK.
tARIFF METERS ARE VERY EXPENSIVE. SCS MUST FOLLOW LOAD
DESPATCHING REGULATION AND ITS SPECIFICATION.

Question { Siemens, 4275 }

why we not using 230kv directly why we are stepping down and
then stepping up

Answer

high voltages are safe method to trasfer power generations
bulk power .
High vloltahe are directly used in iron steel factory arc
furnaces -400kv,230kv to 60,30kv arc furnaces, where
generation source very near or long distace net work.

industries adopt bulk supply.
domestic, medium comsummers are 400v,4W,and 230v -mobile
charger ,tv,washing machines, frinders, .....

Question { GIL, 2633 }

why we define potections of Tourbo generator in Class A & B.

Answer

It is just the Client /owner/consultant choice.

As there are many protections in turbo alternater grouping
them in class A and B category indicate the severity of
faults and guess the extent of damages.
Class -A category need special attention and to be analized
cautiously.Ex- Generator differential means there is serous
trouble to identify the cause. Generator winding
damages,flash over..., It needs generator inspection and
tests. If it is ok then proceeds to Operations.
Where as Class -B an overload, overcurrent,under voltage...
secondary importance.Operational proceedure can be
followed.No need to trip units.However ,occurance of classB
protections also trips the turbo-alternator with time delay.

Question { 3417 }

without name plate detail of blower how we can find out the
HP & Rpm ? the input voltage is 230v single phase

Answer

voltage is 230v, 1ph. application being exhaust fan,supply
air fan, water pumps, . speed are generally
750,1000,1500,2800rpm.check the fan blades.3,4,6.

Question { 3105 }

in power station what is the electrical circuit length of
spacing between power transformer and lightning
arrestors,for the voltage system of
230kv,110kv,33kv,22kv,11kv?

Answer

standard says as nearaspossible. we maintain just the
outlet of power transformer bushing-10m for all
400,230,110,66,33,11kv.
we adopt counter and mA indicator in the LA grounding,
LA grounding is separately connected to main earth
grounding system

Question { 3577 }

A 150KW 440V motor is need to replace in the field instead
of faulty one. what are the main parameter should I need to
check?

Answer

150kw , 440 is a large motr. the starting current of this
induction motor will be 5-8 times depend on drive ex-fan.
and coast for 6-8s to attain full speed.
so, the new contactor shall be good quality , with
overload,instantaneous with time delay shall be selected.
Reverse rotation protection, vibrations,
Unbalnced current protection optional.
LV power cable terminal box cable connection and support.

Question { 5850 }

what are the settings is there for ABB REM543 Generator
Protection Relay

Answer

GENERALLY,WHEN THE COMMISSIONNG IS DONE WITH SHORT CIRCUIT
TEST, ALL PARAMETERS ARE SET FOR ALL PROTECTION RELAYS-
NAMELY: i) differential protection
ii) Over current,instantaneous over current

iii) Unbalanced current ( negative sequence)

iv) loss of ecxcitation.

v) reverse power

vi) Under voltage.

viii) over voltage

hence it is not necessary to repeat .

Question { Essar, 3279 }

WHAT IS DIFFRENCES DCS & PLC

Answer

DCS MEANS DISTRIBUTED CONTROL SYSTEM
PLC -PROGRAMME LOGIC CONTROL
IN A PROJECT OR REFINERY, ASSOCIATED WITH MAIN EQUIPMENT-
SUCH AS BOILER,GAS TURBINE ,STEAM TURBINE ,GENERATOR
N400,230KV SUB STATION... AND BALANCE OF PLANT EQUIPMENT-
fUEL OIL SYSTEM,FUEL GAS ,FIRE FIGHTING,WATER TREATMENT,
AUXILIARY BOILER,AIR COMPRESSOR,HVAC,RAW WATER SYSTEM.

EACH SYSSTEM IS DESIGNED BY DIFFERENT SUPPLIER WITH ITS OWN
LOGIC. tHIS IS DONE BY plc CONTROLLERS.

sO, EACH SYSTEM IS INTEGRATED WITH dcs SYSTEM.
dcs IS THE MANAGEMENT SYSTEM AND INTEGRATES ALL SUB SYSTEM .

DCS INTEGRATES ALL SYSTEM CENTRALLY. oVERALL MONITORING IS
DONE AND MAINTAINS LONG TERM EVENT RECORD.
THE ENTIRE PLANT IS OPERATED start/sTOP SEQUENTIALLY.
aLSO PERMITS DECENTRALIZED OPERATION.
AND IN

Question { 2922 }

what will be the effect of leading power factor on
turbogenerator (and system) that is running parallel with
other TG.

Answer

iT IMPROVES POWER FACTOR AND STABILTY OF GRID BUT GENERATOR
ROTOR INSULATION IS OVERHEATED,LIFE IS REDUCED.

Question { NTPC, 4055 }

How do we measure earth fault current in Generator
Transformer(20/420kv),Station Transformer(20/11 kv) and Unit
Transformers(20/11kv) for our plant system, since these
don't have any Neutral earth Fault relay connected to their
Neutral Earth?
But for Unit Service transformers(11/.433 Kv) we have an
Earth Fault Relay connected to its neutral earth.Why is such so?

Answer

I assume your generator rating is around 250-315MW.

GENERATOR TRANSFORMER IS YN-d1 or d11, 420kv power
transformer is provided with neutral bushing and solidly
grounded to earth system (U,V,W-N). YOU CAN MEASURE THE
EARTH CURRENT WITH CLAMP ON METER.

GENERATOR 20KV OUTPUT IS CONNECTED WITH lv side of
generator transformer by bus duct. there is a voltage
transformer, 2 winding y/y or three winding VT Y/y-
opendelts. This open delts voltage indicate the fault in
20kv system.

Genrator is provided with 90% and 100 % earth fault
ptortection.
Generator neutral is connected with generator neutral
grounding transformer. Generator neutral transformer
primary is connected to genrator neutral point and other N
is connected to earth. at this point ,You can measure earth
current by clamp on meter.
I assume you have a Generator circuit breaker.

Generator bus is 20kv. This sw.gr feed stn tranformer -
20/11kv system.This station 11kv feed the auxilary
transformers. Vector group of this stn transformer is D/d.

Also unit transformer is 20/11kv. this 11kv bus feed motor
and auxiliayr transformers. vector group is also D/d.

your medium voltage operates as isolated ground system

Unit service transformer is 11/.433 , thereforn vector
group is D/yn. your low voltage feeder need a nuetral.
therefore neutral is brought out. three phase 4 wire, and
230v-n .

please send the rating of transformer. we can explain you
more.

Question { 3110 }

What is the following which is printed on electrical
appratuses like AC21 ,AC 23 , etc ?

Answer

it is the contractor rating .
Refer to IEC standards as mention in the catalogs.
It is the recommendation of electrical standard to select
the device rating,type.

Question { 2831 }

WHAT IS METHOD TO DESIGN SIZE OF A 11KV UNDER GROUND CABLE
FOR A OUTGOING FEEDER FEEDING 6NOS 250KVA TRANSFORMERS WITH
5KM LENGTH OF FEEDER?

Answer

refer to any hand book power cable and IEC power cable
specification.

Question { 2594 }

Whether earthmat designning is done only for sub station or
it can be done for multy residential complexes also?
What is the size, type & arrangement of the earth grid to
be done?

Answer

No.it is done for building campus,
industries,hospitals.large campuses, tv station...

It depends on load,voltage level of source and distribution
sytem.


refer IEEE 80 hand book

Question { 3898 }

How to design grid earthing

Answer

refer to detail description -IEE80 HAND BOOK