T e s t i n g &Cm m i s s i o n i n ge p o r t f"66/33 b
-t a t i o n "
By:
Olakha Sub-Station, SMD Semtokha.
i
ACKNOWLEDGEMENT
I would like to express profound gratitude to the then Officiating
General Manager Mr. Nima
Dorji for placing me at the up gradation works at 66/33 KV Olakha
substation without which, I
wouldn’t have been able to come out with this report. This provided
me an opportunity to learn
regarding the testing and commissioning of various switch gears, no
sooner I graduated from the
college. The placement was very appropriate and at the right
time.
I wish to extend sincere gratitude to Mr. Chandan Kamti Chatterjee,
Testing Engineer, IPPL for
teaching me all the practical aspect of the 'Testing and
Commissioning' works and also the
theoretical part of the same which are beyond the coverage in the
books, which he explained
through his 22 years of field experience in 'Testing and
Commissioning'. I am indebted for his
effort in revisiting my report and for making necessary correction
and addition.
I would also like to offer sincere appreciation which is due to the
staff members of SMD
Semtokha and Olakha Substation. Amongst the various persons who
have helped me in this
endeavor, I would like to mention the following: Mr. Sonam Tobgay
(Manager), Mr. Tandin
Gyeltshen, Mr. Sonam Norbu and Mr. LB Rai.
I gratefully acknowledge the extensive literature referred during
the course of writing this report.
Last but not the least I would like to thank all those who have
assisted me directly or indirectly in
coming out with this report.
ii
ABSTRACT
This primary goal of this report is to provide in a simple and more
of conventional way of
conducting the testing of various switchgears and the system. This
report 'Testing and
Commissioning Report of 66/33KV Olakha Sub Station' describes
about the various testing that
are required to be done before commissioning of a substation. It
contains in a lucid way, a
concise presentation of various technical data and parameters that
were obtained while in field
testing. This report intends to serve as a history of Olakha
substation in terms of its technical data
and could be used as future reference while testing however the
data may vary with different
instruments used and the way it is conducted.
This report is also equipped with the practical and pictorial
circuit diagram of the exact field
testing that was done while in the course of testing. Theories have
been provided for every
experiment based on the practical hands on experience.
The materials presented in this report are intended to serve as a
platform from where young and
enthusiastic technical people could enhance their learning and
explore in the area of testing and
commissioning. However it could be used as reference by the one who
already have the
experience.
I would like to solicit the readers' kind suggestions and feedback
regarding the report so that I
could come up with better one in future.
List of Figures
Figure 1 Experimental set up for checking the winding resistance
................................................ 3
Figure 2 Experimental set up for CT Ratio
check ........................................................................
14
Figure 3 Experimental setup for ratio test of PT and
CVT ...........................................................
23
Figure 4 KPV Testing of Current
Transformer ............................................................................
29
Figure 5 Surge Monitor Testing
...................................................................................................
38
Figure 6 SF6 Circuit Breaker Testing SCOT M3K
Timer ............................................................
41
Figure 7 SF6 Circuit Breaker Testing with Circuit Breaker
Operational Analyzer .................... 42
Figure 8 Measurement of Transformer's winding resistance
.......................................................
49
Figure 9 Various testing on
Transformer .....................................................................................
57
Figure 10 Conditioning of Transformer Oil
.................................................................................
67
Figure 11 Winding Resistance Check of 33kv CT &
PT ...............................................................
79
Figure 12 Ratio Check of 33kv
CT ...............................................................................................
80
Figure 13 High POT Test (CABLE HV TEST)
.............................................................................
93
Figure 14 Inverse-Time, Very-Inverse Time and Extremely-Inverse
Time characteristics. ....... 100
Figure 15 Testing of IDMT Relays
.............................................................................................
101
Figure 16 System Stability Testing
.............................................................................................
114
CT Ratio Check
.........................................................................................................................
13
Knee Point Voltage Test (KPV Test) of Current Transformer
................................................. 27
Surge Monitor Testing
..............................................................................................................
38
Transformer Winding Resistance
..............................................................................................
48
Winding Resistance and Ratio Check of 33kv CT & PT
.......................................................... 78
High Pot Test (Cable HV Test)
.................................................................................................
92
Relay Testing (Over Current Protection)
................................................................................
100
Stability Testing Report
..........................................................................................................
113
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 1
Checking the Winding Resistance of CT, PT & CVT Bs
T #1:T n i e Ln e i d eBs T #2:T n Jm i n a Ln e i d eCT #1:CT n i
e Ln e i d eCT #2:CT n Jm i n a Ln e i d eC#1 :C n i e Ln e i d
eC#2 :C n r a n s f o r m e r Ii d eC#3 :C n Bs Cu p l e r i d eC#4
:C n Jm i n a Ln e i d eC#5 :C n r a n s f o r m e r IIi d
eA:
1. To check the Secondary Winding Resistance.
2. Insulation Resistance (IR) checks of primary-earth and
secondary-secondary
winding by using Megger (2.5KV-5KV).
3. Secondary insulation resistance value check of
secondary-earth and secondary-
secondary terminals.b j e c t i v e s : 1. To check the
resistance of secondary winding (CT, PT and CVT) and compare
with that of name plate rating.
2. To check if there is any short circuit or leakage to
ground from primary winding.
To check if there is any short circuit between primary and
secondary windings.
3. To check if there is any leakage or short circuit between
the secondary winding
and the earth. To check if there is any short circuit between the
secondary
windings.Ist r u m e n t s s e d : Sl. no Description Specification
Quantity Remarks
1 Megger 2.5KV-5KV, 0-10000Mohms, Waco,
Type 485/08-09, Sl. no. 933090 1
2 Megger 1KV, 0-200Mohms, Waco,
Sl. no. 91611 1
Motwane 1
4 Connecting wires ---------------------------------------------
APR
NB: Megger uses Ohm's law V=IR. It gives DC voltage and the
current which flows through the
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 2
PT Core 1, Core 2 and Core 3 of PT
Secondary Winding Terminals Earth Link
T e s t p p l i e d o;
Cr c u i t i a g r a m 2a
Rph Yph
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 3
IR Value check (Meggering)
Secondary Winding Resistance Check
Ep e r i m e n t a l e t p :
Earth
Figure 1 Experimental set up for checking the winding
resistance
Multimeter
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 4
P r o c e d u r e :1.S e c o n d a r y i n d i n g e s i s t a n c
e a. Remove the earth terminal from three phases of PT from
the lower side of the
box. Make sure there is no connection from the PT to
earth.
b. Use the Multi meter as ohmmeter and measure the
winding resistance of the
respective secondary windings and of respective phases.
c. Tabulate the reading and compare with the
standard/manufacturer value.2.Is u l a t i o n e s i s t a n c e s
h e c k (Mg g e r i n g ). a. Connect the Megger terminal to
primary winding and earth terminal. Apply 5KV
by Meggering and note down the readings as shown by
Megger.
NB: Since primary winding is on HV (66KV) side we need to
apply high voltage i.e. 5 KV.
b. Keeping one of the Megger terminals connected to the
primary, connect the other
terminal to the various secondary winding one by one. Apply 5KV by
Meggering
and note down the subsequent readings.3.S e c o n d a r y n s u l a
t i o n e s i s t a n c e s h e c k (Mg g e r i n g ). a. Use
lower rating Megger (1KV) for testing. This is because output
voltage from
the secondary windings is 110V, so we cannot apply very high
voltage, otherwise
the windings will get burned.
b. Connect the Megger to secondary 1- earth terminal,
followed by secondary 2-
earth and secondary 3-earth terminals respectively. Apply 1 KV by
Meggering
and note down the subsequent readings.b s e r v a t i o n s :
• If there is any short circuit between the windings or
earth, then the Megger will show
zero value.
• Else Megger will show some deflections indicating the
insulation resistance value.
• Megger gives DC output
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 5
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 6
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 7
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 8
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 9
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 10
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 11
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 12
P r e c a u t i o n : • Safety of the experimenter, the first
preference.
• Never start Meggering if both the terminals is being
caught by performer
• Always discharge by connecting the terminal to earth so
that the experimenter is free of
shock.Cn c l u s i o n : From this test it is proved that there
isn't any leakage or short circuit connection from primary to
earth through the casing. Neither is the secondary windings
touching the casing or with each
other nor the primary winding is in contact with the secondary
windings. The Potential
transformer is perfectly right.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 13
CT Ratio Check C#1:C n i e i n e i d eC#2:C n
r a n s f o r m e r Ii d eC#3:C n Bs Cu p l e r i d eC#4:C n Jm i n
a Ln e i d eC#5:C n r a n s f o r m e r IIi d eA:Ratio Test on
various Current Transformers.b j e c t i v e : To check the
ratio of primary to secondary current under loaded condition and
compare
with the name plate rating.T h e o r y : Current transformers (CTs)
of all sizes and types find their way into substations to provide
the
current replicas for metering, controls, and protective relaying.
CT performance is characterized
by ratio correction factor (turns ratio error), saturation
voltage, phase angle error, and rated
burden. Bushing CTs are installed in power equipment. They
are toroidal, having a single primary turn (the power
conductor), which passes through their center. The current
transformation ratio results from the number of turns wound on the
core to make up the
secondary. More than one ratio is often provided by tapping the
secondary winding at multiple turn's ratios. The core
cross-sectional area, diameter, and magnetic properties determine
the CT's
performance. Metering CTs are designed with core
cross-sections chosen to minimize exciting current effects and are
allowed to saturate at fault currents. Larger cores are provided
for
protection CTs where high current saturation must be avoided
for the CT to faithfully reproduce
high currents for fault sensing. The exciting current of the larger
core at low load is not considered important for protection.
Core#1 : Metering.
Earth fault, Differential).
Core#4 : Bus Bar Protection Zone
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 14
C u
r r e n
t T r a
n s f o
r m e r
Clamp Leaker
Clamp meter
Junction Box
Ist r u m e n t s s e d: Sl. no Description Specification Quantity
Remarks
1 Auto Transformer 0-260V, 50Hz 1
2 Loading Transformer 230V,50Hz-7.5KVA, 1V/T 1
3 Multimeter AC/DC, Analog, Multi-range 1
4 Clamp leaker DC-10A, Motwane 1
5 Clamp meter Kyoritsu, DCM, Model 2002 1
6 Connecting wires -----------------------------------------
APR
Figure 2 Experimental set up for CT Ratio check
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 15
P r o c e d u r e : 1. Set up the experiment as shown in the
circuit diagram.
2. Make the connections in the junction box so as to get the
CT ratio 300/1A. Connect the
first terminal and the middle one so that we get the ratio 300/1A
i.e. 1S1-1S2, 2S1-2S2,
etc. Never leave any CT secondary open.
3. Load the primary with certain percentage of full load
current. Increase the load current in
steps of 25%, 50%, 75% and 100% of the rated primary current.
Observe it on the clamp
meter held on the primary side.
4. With the help of clamp leaker measure the current on the
secondary side, on each core
and note down the readings.
5. Put off the power supply and then make the connections in
junction box so as to get
600/1A CT ratio. Connect first terminal and the last terminal i.e.
1S1-1S3, 2S1-2S3, etc.
6. Load the primary with 12.5%, 25%, 37.5% and 50% of the
rated primary current and
check the values on the clamp meter.
7. With the help of clamp leaker, measure the current in each
core i.e. secondary side. For
simplicity note down the readings for half core first and then go
for full tap readings.
8. Repeat step 1-7 for other two phases also.P r e c a u t i
o n : i. Safety the first priority.
ii. Never open the secondary terminal of the Current
Transformer while it is on loaded
condition.
iii. Make the connections tight.
iv. To avoid over heating of the primary connections, give
100% primary input for the
lowest tap and 50% primary input for the full tap.R e s u l t s :
The results are being tabulated for each current transformer. The
actual ratio given on the
name plate is 300-600/1A. The ratio replicates the name plate
rating when the applied
load current approaches the name plate rating. The errors are more
when 12.5% and 25%
of the total load current is applied. However as we apply more and
more towards the
actual load value, the ratio is almost near the actual ratio. The
accuracy of CT is
expressed in terms of its ratio from its true ratio. This is called
ratio error and is expressed
as;
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 16
1.C#1, i e Ln e i d e (Ic o m e r #1)C#1, 11-12, 300/1ADt e
:22/10/09, h u r s d a y , 4:40m , u n n y . R-Sl.no. OC
2373/1/5/08, Y-Sl.no. OC 2373/1/12/08, B-Sl.no. OC 2373/1/10/08%f a
t e dr i m a r yCr r e n t(A)Ap l i e dr i m a r yCr r e n t(A) S e
c o n d a r y Cr r e n t (A)-h a s e Y -h a s e B-h a s e
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 17
2.C#2, r a n s f o r m e r #1i d e (Ic o m e r #1)C#2, 11-12,
300/1ADt e :22/10/09, h u r s d a y , 4:55m , u n s e t . R-Sl.no.
OC 2373/1/15/08, Y-Sl.no. OC 2373/1/9/08, B-Sl.no. OC 2373/1/1/08%f
a t e dr i m a r yCr r e n t(A)Ap l i e dr i m a r yCr r e n t(A) S
e c o n d a r y Cr r e n t (A)-h a s e Y -h a s e B-h a s e
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 18
3.C#3, Bs Cu p l e r i d eC#3, 11-12, 300/1ADt e :23/10/09, Fi d a
y , 9:50m , u n n y . R-Sl.no. OC 2373/1/7/08, Y-Sl.no. OC
2373/1/8/08, B-Sl.no. OC 2373/1/6/08%f a t e dr i m a r yCr r e n
t(A)Ap l i e dr i m a r yCr r n t(A) S e c o n d a r y Cr r e n t
(A)-h a s e Y -h a s e B-h a s e
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 19
4.C#4, Jm i n a Ln e i d e (Ic o m e r #2)C#4, 11-12, 300/1ADt e
:22/10/09, h u r s d a y , 6:00m , Dr k . R-Sl.no. OC 2373/1/14/08,
Y-Sl.no. OC 2373/1/2/08, B-Sl.no. OC 2373/1/16/08%f a t e dr i m a
r yCr r e n t(A)Ap l i e dr i m a r yCr r e n t(A) S e c o n d a r
y Cr r e n t (A)-h a s e Y -h a s e B-h a s e
(A) Ratio % error (A) Ratio % error (A) Ratio % error25%750.24
312.50 4.17% 0.23 326.09 8.70% 0.23 326.09 8.70%50%1500.50 300.00
0.00% 0.49 306.12 2.04% 0.49 306.12 2.04%75%2250.76 296.05 -1.32%
0.74 304.05 1.35% 0.74 304.05 1.35%100%3001.01 297.03 -0.99% 1.00
300.00 0.00% 0.99 303.03 1.01%C#4, 11-13, 600/1A12.5%750.11 681.82
13.64% 0.11 681.82 13.64% 0.11 681.82 13.64%25.0%1500.24 625.00
4.17% 0.23 652.17 8.70% 0.23 652.17 8.70%37.5%2250.36 625.00 4.17%
0.35 642.86 7.14% 0.36 625.00 4.17%50.0%3000.49 612.24 2.04% 0.50
600.00 0.00% 0.49 612.24 2.04%C#4, 21-22, 300/1A25%750.24 312.50
4.17% 0.24 312.50 4.17% 0.24 312.50 4.17%50%1500.50 300.00 0.00%
0.50 300.00 0.00% 0.50 300.00 0.00%75%2250.76 296.05 -1.32% 0.76
296.05 -1.32% 0.75 300.00 0.00%100%3001.01 297.03 -0.99% 1.02
294.12 -1.96% 1.00 300.00 0.00%C#4, 21-23, 600/1A12.5%750.11 681.82
13.64% 0.10 750.00 25.00% 0.11 681.82 13.64%25.0%1500.24 625.00
4.17% 0.24 625.00 4.17% 0.24 625.00 4.17%37.5%2250.36 625.00 4.17%
0.36 625.00 4.17% 0.36 625.00 4.17%50.0%3000.50 600.00 0.00% 0.50
600.00 0.00% 0.49 612.24 2.04%C#4, 31-32, 300/1A25%750.24 312.50
4.17% 0.24 312.50 4.17% 0.24 312.50 4.17%50%1500.50 300.00 0.00%
0.50 300.00 0.00% 0.50 300.00 0.00%75%2250.76 296.05 -1.32% 0.75
300.00 0.00% 0.75 300.00 0.00%100%3001.01 297.03 -0.99% 1.01 297.03
-0.99% 1.01 297.03 -0.99%C#4, 31-33, 600/1A12.5%750.11 681.82
13.64% 0.11 681.82 13.64% 0.11 681.82 13.64%25.0%1500.24 625.00
4.17% 0.24 625.00 4.17% 0.23 652.17 8.70%37.5%2250.36 625.00 4.17%
0.36 625.00 4.17% 0.35 642.86 7.14%50.0%3000.49 612.24 2.04% 0.50
600.00 0.00% 0.50 600.00 0.00%C#4, 41-42, 300/1A25%750.24 312.50
4.17% 0.24 312.50 4.17% 0.24 312.50 4.17%50%1500.50 300.00 0.00%
0.50 300.00 0.00%0.50 00 0.00%
50% 150
0202962895(0500008(-1273()28Tc[(300)67(00)-1377297758098400055
TD00024Tc(050)Tj27377-00055TD00026Tc[(300)6
7(00)-114974(000%)5()]T758508200055TD00024Tc[(050)51()]TJ28962-0
0055TD00026Tc[300)67(00)f05(714%)49()]TJET66362155327
350011272ref6636185532 7351272ref6128255 327351272
reff1884553273500112 72ref884189455327 350011272ref88418945532
7350011272ref884 189455327350011272 ref8841894553273500112
72reff997814553273500112 72reff33261455327 80011272ref46674145532
780011272ref40784 145532780011272 ref553561998047998
1278re98196188BT1098070
0103047Tf910021-)7(4)4601Tm41792Tw[(500%)8(22-13772(000%)5()]TJ9191
00210120002000500038(-1273(99Tc[(300-10021-)7(4)4601Tm41112400055TD00024Tc(0
50)Tj27377-00055TD005011278 ref351272ref6128255
32755TD0050112724ref4(0 00%278r1272r5f663616553276
Tc[(3002ref617)]T55327351272reff188653 804812 78ref222541996538
040011278ref18865 380400112 78re72ref653 804812 78ref2272ref6538
0481278ref223(16128255-418(15327(1reff17
8001189403(16128255-411(150011415784189455327
3500112712()]TJ/TT51Tf997760 ()]TJ/TT51Tf997760(
)]TJ/TT51Tf997760()]TJ/TT51Tf9 97760()3471998 0479981278re
981333500112
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 20
5.C#5, r a n s f o r m e r #2i d e (Ic o m e r #2)C#5, 11-12,
300/1ADt e :23/10/09, Fi d a y , 10:20m , u n n y . R-Sl.no. OC
2373/1/3/08, Y-Sl.no. OC 2373/1/18/08, B-Sl.no. OC 2373/1/4/08%f a
t e dr i m a r yCr r e n t(A)Ap l i e dr i m a r yCr r e n t(A) S e
c o n d a r y Cr r e n t (A)-h a s e Y -h a s e B-h a s e
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 21
Cn c l u s i o n : From this experiment, it is proved that the name
plate ratio replicates the field test report.
However the name plate ratio matches the field test ratio at 100%
of the actual load current for
lowest tap. For the full tap 50% of the actual load current was
provided. The ratio came close to
name plate rating at the 50% of the full load current. From this I
conclude had we applied the full
load current we will be getting exact replicate of the name plate
rating. We couldn't apply full
load current on 600/1A tap as the primary wire was getting heated
up. More or less the obtained
results are correct.
The ratio error of a CT depends on its exciting current. When the
primary current increases, the
CT tries to produce corresponding secondary current, and this needs
a greater secondary emf,
core flux density and exciting current. A stage comes when any
further increase in primary
current is almost wholly absorbed in an increased exciting current
and thereby the secondary
current hardly increases at all. At this stage CT becomes
saturated. Thus the ratio error depends
on saturation.
An accuracy of 2-3% of the CT is desirable for distance and
differential relays, where as for
many other relays, a higher percentage can be tolerated. When the
primary current increases, at a
certain value the core commences to saturate and the error
increases. The value of current at
which the error reaches a specified error limit is known as its
'Accuracy Limit Primary Current'
or saturation current. The ratio of accuracy limit primary current
and the rated primary current is
known as rated accuracy limit factor (ALF) or saturation factor,
the standard value of which are
5,10,15,20 & 30.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 22
Ratio Test of CVT and PT CT#1:Cp
a c i t i v e o l t a g e r a n s f o r m e r (i e Ln e i d e
)CT#2:Cp a c i t i v e o l t a g e r a n s f o r m r (Jm i n a i d
e )T #1 :o t e n t i a l r a n s f o r m e r f Bs (r a n s f o r m
e r #1i d e )T #2 :o t e n t i a l r a n s f o r m e r f Bs (r a n
s f o r m e r #2i d e )A:
To find the ratio of primary voltage to the subsequent
secondary voltage and then
compare with the given ratio in the name plate rating.b j e c t i v
e : To measure the voltage of three cores of each phase on
the secondary winding and check
if the ratio is alright upon doubling the applied voltage on
primary side.Ist r u m e n t s e d Sl. no Description Specification
Quantity Remarks
1 Auto Transformer 0-260V, 50Hz 1
2 Transformer 230V-3000V, 50Hz 1
3 Multimeter AC/DC, Analog, Multi-range 1
4 Multimeter DM3540A (Motwane) 1
5 Connecting wires ---------------------------------------------
APR
6 1- Supply 230V, 50Hz 1h e o r y :Potential transformers are
used to reduce the system voltage level low enough to
suit the ratings of protective relays. The voltage rating of
protective relay is usually 110V. The %
error is given by;
100
Where K= Nominal voltage ratio, Vs= Secondary voltage and
Vp=Primary voltage.
The accuracy of PTs used for meters and instruments is only
important at normal system voltage
where as PTs used for protection requires errors to be limited over
a wide range of voltages
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 23
Secondary Voltage Measurement
T e s t p p l i e d o /x p e r i m e n t a l e t p;
Capacitive Voltage Transformer
Figure 3 Experimental setup for ratio test of PT and CVT
Circuit diagram
1
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 24
P r o c e d u r e: 1. Set up the connection as shown
below.
2. Connect one wire from HV side of transformer to the top of
CVT.
3. Connect the other to the earth.
4. Adjust the voltage from the auto transformer so that 1KV
is available on the secondary
side of transformer which is shown on the voltmeter. (In fact we
are applying 1KV to the
primary winding of CVT).
5. Connect a multimeter (Voltmeter) to the core 1, core 2 and
core 3 of each phase of CVT
upon the application of 1KV to the primary and note down the
reading.
6. Repeat the same for other two phases.
7. Repeat step 4 so that we get 2KV on the secondary side of
the transformer and follow
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 25
Bs T #1(r a n s f o r m e r #1i d e )Dt e :19/10/09, Mn d a y ,
11:35m , u n n y . R-Sl.no. OP 2373/1/7/08, Y-Sl.no. OP
2373/1/3/08, B-Sl.no. OP 2373/1/4/08r i m a r y () S e c o n d a r
y ()-h a s e Y -h a s e B-h a s eCr e 1Cr e 2Cr e 3Cr e 1Cr e 2Cr e
3Cr e 1Cr e 2Cr e 10001.709 1.706 1.706 1.670 1.670 1.724 1.701
1.682 1.681R a t i o 585 586 586 599 599 580 588 595 595%Er o
r-2.5% -2.33% -2.33% -0.17% -0.17% -3.33% -2.0% -0.83%
-0.83%20003.29 3.29 3.29 3.25 3.26 3.26 3.30 3.30 3.30R a t i o 608
608 609 615 614 614 606 606 606%Er o r1.3% 1.3% 1.5% 2.5% 2.33%
2.33% 1.0% 1.0% 1.0%Bs T #2(r a n s f o r m e r #2i d e )Dt e
:19/10/09, Mn d a y , 11:35m , u n n y . R-Sl.no. OP 2373/1/5/08,
Y-Sl.no. OP 2373/1/6/08, B-Sl.no. OP 2373/1/8/08r i m a r y () S e
c o n d a r y ()-h a s e Y -h a s e B-h a s eCr e 1Cr e 2Cr e 3Ce
1Cr e 2Cr e 3Cr e 1Cr e 2Cr10001.75 1.75 1.75 1.78 1.78 1.78 1.70
1.74 1.74R a t i o 571 571 571 562 562 562 588 575 575%Er o r-4.83%
-4.83% -4.83% 6.3% 6.3% 6.3% 2.0% 4.17% 4.17%20003.30 3.31 3.31
3.37 3.37 3.37 3.38 3.38 3.38R a t i o 606 604 604 594 594 594 592
592 592%Er o r1.0% 0.67% 0.67% -1.0% -1.0% -1.0% -1.3% -1.3% -1.3%b
s e r v a t i o n:
1. From the result obtained the ratio of primary to secondary
voltage is within the range
607-626 where as the actual ratio are 600. The experimented ratio
is slightly greater than
the actual value.
110/√ 3 600
There is slight error which may be because of the inaccuracy of
voltage applied from the
transformer. However the results are fairly correct.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 26
P r e c a u t i o n: • Safety of the experimenter, the first
preference.
• Always take the reading after it reaches a stable
value.
• Always avoid parallax error while noting the reading.
• Always give proper connection to CVT and to earth.Cn c l u
s i o n : From this test it is seen that the ratio of primary to
secondary voltage is fairly correct with
maximum of 6.5% error. For Lab test an error of ±5% is the accepted
while for the field test an
error of ±15% is accepted. The error can be eliminated by using
more accurate meter, and
applying the accurate voltage. Since the analog meter was used for
noting the reading on the
primary side, may be exact voltage wasn’t applied, parallax
error might have introduced in the
process. However the result doesn’t deviate much from the
exact value thus the name plate rating
is ok.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 27
Knee Point Voltage Test (KPV Test) of Current Transformer C
#1 :Ic o m i n g n e C (i e Ln e )C#2 :C n r a n s f o r m e r Ii d
eC#3 :Bs Cu p l e r CC#4 :Ic o m i n g i n e #2C (Jm i n a Ln e
)C#5 :C n r a n s f o r m e r IIi d eA:Knee Point Voltage Testing
of Current Transformers.b j e c t i v e : This test should
confirm that at any case the saturation point shouldn’t lie before
100% of
KPV. It may occur at 110% or higher, doesn’t matter but saturation
point shouldn't occur
before 100% of the KPV. If saturation point occurs before
100% of KPV then the relays
will operate before reaching its set value (100%) which is not
desirable.
To find the saturation point of CT i.e. at what point of voltage it
get saturated.
Compare the obtained saturation point with that of the name plate
rating.T h e o r y : Knee point voltage is the point on the graph
obtained between voltage and current beyond which
the current rise is very sharp when voltage in increased slightly.
When the applied voltage is
increased in steps the current also rises in certain step. When the
knee point voltage is reached
then the current shoots up beyond its normal increasing step.
Therefore in this test we see
whether the KPV given on the name plate is correct or not. If the
saturation point is reached
before the actual KPV then the relays are going to trip
before fault occurs. In fact the relays
should trip upon reaching KPV or later. Therefore for proper
coordination and tripping or relays
KPV should be checked accurately. Since minimum KVP at lowest tap
is provided for core 3 &4
of CT, so we test KPV for only these cores.
V
I
KPV
0
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 28
Ist r u m e n t s e d: Sl. no Description Specification Quantity
Remarks
1 Auto Transformer 0-260V, 50Hz 1
2 Transformer 230V-3000V, 50Hz 1
3 Multimeter AC/DC, Analog, Multi-range 1
4 Clamp leaker DC-10A, Motwane 1
5 Connecting wires ---------------------------------------------
APR
Name plate rating
P r o c e d u r e: 1. Set up the connection as shown
below.
2. Apply certain percentage of Knee point Voltage to Core #3
and Core #4 and then note
down the readings as shown by clamp leaker.
3. Repeat the same step for other two phases.
4. Compare the readings.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 29
AV Meter
T e s t p p l i e d o/x p e r i m e n t a l e t p :
Figure 4 KPV Testing of Current Transformer
1
l y
Junction box
Clamp leaker
Cr r e n t r a n s f o r m e r #1 Sl.No. 2373/1/5/08
Sl.No. 2373/1/12/08
Sl.No. 2373/1/10/08Cr r e n t r a n s f o r m e r #3 Sl.No.
2373/1/7/08
Sl.No. 2373/1/8/08
Sl.No. 2373/1/6/08
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 30
Primary
(650V)
T e c h n i c a l e r m s: Name plate rating :Mn i m u m Ke e
o i n t o l t a g e t o w e s t a p =325 There are two tapping in
each core of CT. Therefore in this case lowest tap refers to the
tapping
between one end and the middle point. So at full tapping the
Knee Point Voltage will be the
double of the KPV of lowest tap.
KPV for Core#3 and Core#4
Knee Point Voltage is available for only core #3 and core #4. This
is because these cores are
specifically designed for protection class core. For protection
class core, saturation of current is
very important and need to protect the equipment from over current.
Whenever the current
reaches its saturation point, relay should trip off. Therefore
these cores have Knee point Voltage,
before which saturation shouldn’t occur.
Accuracy rating for Core#1 and Core#2
However this is not the case with core#1 and core#2. These cores
are specifically designed for
metering purposes, where accuracy is of much importance. If
saturation point exists for these
cores then when the current increases beyond certain value, the
meter will stop reading, in fact
the meter should record whatever the amount of current drawn.
Therefore these cores are rated at
0.2 class of accuracy.
For half the winding of each core, the rated KPV is 325V therefore
for full winding the rated
KPV is 650V. More the number of turns, greater will be the voltage
and lesser will be the
current, thereby the ratings 325V, 60mA and 650V, 30mA.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 31
R e s u l t s :1.Ic o m i n g i e i n e C, C#1C#1, 31-32, 325,
60At/2Dt e :19/10/09, Mn d a y , 3:30m , u n n y . R-Sl.no. OC
2373/1/5/08, Y-Sl.no. OC 2373/1/12/08, B-Sl.no. OC 2373/1/10/08%f
KV Ap l i e d o l t a g e ()-h a s e (A)-h a s e (A)B-h a s e
(A)25%81.257.31 8.22 7.7950%162.5010.99 12.43 12.0875%243.7516.31
20.34 19.45100%325.0029.98 40.00 36.70110%357.5045.90 71.00
67.80C#1, 31-33, 650, 30At/225%162.503.65 3.97 3.7650%325.005.55
6.31 5.9175%487.507.46 9.69 8.88100%650.0011.93 18.55
15.39110%715.0015.79 25.77 23.10C#1, 41-42, 325, 60At/225%81.257.54
8.25 8.3450%162.5011.95 12.74 13.1675%243.7517.14 19.55
20.42100%325.0031.26 42.50 39.50110%357.5053.90 70.30 72.60
For demonstration of saturation current, 400V was being
applied to B-phase and the current
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 32
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 33
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 34
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 35
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 36
81.25
162.5
243.75
325
357.5
400
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250
( ) Cr r e n t (A)
KV Cr v e Ca r a c t e r i s t i c KPV Curve
162.5
325
487.5
650
715
0
100
200
300
400
500
600
700
800
0 5 10 15 20 25
( ) Cr r e n t (A)
KV Cr v e Cr a c t e r s t i c s KPV Curve
Ga p h i c a l Aa l y s i s o r C#1, 41-42, 325, 60A, B-h a s
e
C#4, 41-43, 650, 30At/2, -h a s e
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 37
P r e c a u t i o n : • Safety of experimenter and the teams
the first priority.
• Always take the readings after it has settled to a
particular value.
• Make sure that no heavy equipment like welding machines,
are operating from the same
source from which testing is being done.
• Always note the name plate reading and then perform the
experiment.Cn c l u s i o n : From this experiment it is proved
that the saturation point of current doesn’t occur below 100%
of KPV. In fact it occurs beyond 110% of the rate KPV. Therefore
this equipment is safe to use.
If the saturation point occurs before 100% of KPV then the relays
connected to it will operate
under normal conditions also. When the saturation point occurs, the
current rises to a very high
value, crossing the set point of relays which makes it to trip off,
thus protecting the equipments.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 38
D : 13/10/09Dy : TuesdayT i m e : 5:45pmW e a t h e r
: Sunset
Surge Monitor Testing A :To check the
deflection in the surge monitor.b j e c t i v e :To find out
whether the surge monitor is working or not.Ist r u m e n t s e d :
Sl. no. Description Specification Quantity Remarks
1 Megger 1KV, 0-200Mohms, Waco, Sl. no. 91611
1
2 Connecting Wires ----------------------------------ARe s t p p l
i e d o/e s t e t p;
Lightening Arrester Surge Monitor
Model : SMT2B3R
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 39
P r o c e d u r e: 1. Connect positive terminal of the Megger
to the top portion of the surge monitor as shown
above.
2. Connect the other terminal to the earth terminal.
3. Start Meggeringb s e r v a t i o n: • When voltage
(1KV) was applied to the surge monitor by Meggering, the pointer
inside
the surge monitor started deflecting.
• In some case the pointer didn’t deflect indicating that the
monitor is not working.P r e c a u t i o n : • Safety of the
experimenter, the first priority.
• Never start Meggering if both the terminals is being
caught by performer
• Always discharge by connecting the terminal to earth so
that the experimenter is free of
shock.Cn c l u s i o n : From this test we can know whether the
surge monitor is working or not. If there is no deflection
then it is proved that the surge monitor is not working and need to
be replaced. If the indicator
inside the surge monitor starts to deflect upon the application of
voltage then it is proved that the
surge monitor is working.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 40
SF6 Circuit Breaker Testing CB#1 :Cr c u
i t Be a k e r n Ic o m e r #1(i e Ln e )CB#2 :Cr c u i t Be a k e
r n r a n s f o r m e r #1i d eCB#3 :Cr c u i t Be a k e r n Bs Cu
p l e r i d eCB#4 :Cr c u i t Be a k e r n Ic o m e r #2(Jm i n a
Ln e )CB#5 :Cr c u i t Be a k e r n r a n s f o r m e r #2i d
eA:Testing of SF6 Circuit Breaker.b j e c t i v e :
To find out the Alarm 'Loss of SF6' at 20ºC.
To find out the General Lock out SF6 at 20ºC.
To find the closing and opening time of SF6 Circuit
Breaker.T h e o r y : The Nominal pressure of SF6 gas at 20ºC is
6.0 bars. When the loss of SF6 gas occurs below
certain set value it gives an alarm indicating less SF6 gas. So we
need to attend to it by refilling.
If we fail to attend to the alarm, then when the pressure of SF6
gas falls further, then Lock out of
SF6 occurs. At this point the circuit breaker neither opens nor
closes i.e. it remains in deadlock
position.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 41
Ist r u m e n t s s e d : Sl. no Description Specification Quantity
Remarks
1 SCOT M3K Time Interval Meter
Model no. 2100.02W.166, T&M Pvt. Ltd., Pune India.
1 Set
Motwane 1
Model CPS LS790B, Sl.No. 581964,
Master Earthing
(Double Earthing)
12 for trip 2
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 42
S F6Be a k e r e s t i n g i t h h e e s t i n g Eu i p m e n t f
BC( Circuit Breaker Operational
Analyzer Model 2406 HISAC, Sl. no. 3290-009).
Figure 7 SF6 Circuit Breaker Testing with Circuit Breaker
Operational AnalyzerNB:The terminals from the kit are to be
connected as given in the earlier diagram and the
wires refer the same definition.
B Po w e r u p p l yTo Circuit
Breaker
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 43
P r o c e d u r e :AT -I 1. Connect the SF6 gas pipe to the
breaker and start filling up the gas.
2. Fill up till the pressure reaches 1.0bar.
3. Check all the pipes and SF6 breaker for any leakage with
the help of Refrigerant Leak
Detector. If leakage is there, then it makes continuous beeping
sound. To find the exact
leak area, apply shampoo foam over the area. Wherever the pore is,
the bubble becomes
big and burst out.
4. Leave the Breaker at 1.0bar for few hours. If leakage is
there, the pressure falls down.
5. If there is no leakage then fill up the breaker with SF6
gas at 6.0bars.
6. At certain pressure (5.0 bars approx.) general lock out
SF6 will occur. The multimeter
connected across alarm (X1-4, K11-A1) and trip contact (X1-4,
K10-A1) will make
continuity sound.
7. Increase the pressure until it reaches certain point
(5.3bars approx.) when the multimeter
connected across alarm and trip contact stops making continuity
sound. This is the Alarm
Loss of gas pressure.
8. Still fill up the breaker with SF6 gas until the pressure
reaches 6.0bars and disconnect it.P AT -II 1. Set up the
experiment with SCOT M3K Time Interval Meter.
2. Connect the RYB terminals at the top and middle (make and
break) points and plug it to
the SCOT M3K Time Interval Meter.
3. Connect two ground wires so as to have effective
earthling. If one fails other will work.
4. Connect the control cable with the Circuit Breaker
a. Red one is DC +ive and it is the CB coil source. DC
signals flows from Breaker
to the SCOT M3K Time Interval Meter. Connect it to X1-3, 4, and
5.
b. The command (Close command and Trip command) that we
give flows to the CB
through the other two wires.
c. The yellow wire is C +ive and it is the close coil
terminal. The close command
that we punch goes through this cable to operate the CB. Connect it
to X1-17.
d. Green wire is T +ive and is the Trip coil terminal. The
trip command that we
punch passes through this wire to trip the CB. Connect it to
X-7.
5. Supply AC power to the motor so that it energizes the
spring. When spring compresses to
its set position, the limit switch disconnects the AC supply and
the motor stops, thus the
spring is charged.
6. Give the close, open-1 and close/open command
consecutively with simultaneous
recording of the time (ms).
7. Change the green terminal to X1-12 and give open-2 command
and note down the
readings.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 44
R e s u l t s : 25/10/2009, u n d a y , u n n y .66K Cr c u i t Be
a k e r F6a s i l l i n g r e s s u r e Dn s i t y Mn i t o r t a t
u sl . N.e m p e r a t u r e(C)r i p Cn t a c tLc k o u t a sr e s
s u r e(a r )g /m2t a t u s o u n d Aa r mCn t a c tLs s f F6as r e
s s u r e(a r )t a t u s o u n d 2009/IND/03/6059 20
X1-4 K10-A1
K11-A1
5.3 OKl . N. Mt o r l . N. Co s e Cl ()T r i p Ci l 1()T r i p Ci l
2() 2009/IND/03/6059 - 50.0 50.0 50.0
2009/IND/03/6060 289-087 50.4 50.3 50.6
2009/IND/03/6061 289-349 48.5 50.1 50.6
2009/IND/03/6058 289-436 50.9 50.2 50.0
2009/IND/03/6062 289-543 49.7 49.7 50.1
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 45
T e s t e s u l t f F6Cr c u i t Be a k e r Location :
Transformer#2 Side.
Serial Number : 2009/IND/03/6062. Date of Testing : 26/10/2009,
10:25am, Sunny.
Feeder Name : CB5
Type : 3AP1FG
Make : SEIMENS STC : 40KAP h a s e Co s i n g /p e n i n g i m eCo
s e (s )p e n -1(s )p e n -2(s )C/(s )
R 57 32 30 33
Y 57 32 30 33
B 57 32 30 33Cil e s i s t a n c eCi l R e s i s t a n c e () Close
coil 49.7
Trip Coil-1 49.7
Trip Coil-2 50.1
T e s t e s u l t f F6Cr c u i t Be a k e r Location : Bus Coupler
Side. Serial Number : 2009/IND/03/6061.
Date of Testing : 26/10/2009, 9:45am, Sunny.
Feeder Name : CB3 Rated Voltage : 145KV
Rated Current : 3150A
Type : 3AP1FG Make : SEIMENS
STC : 40KAP h a s e Co s i n g /p e n i n g i m eCo s e (s )p e n
-1(s )p e n -2(s )C/(s ) R 59 33 30 29
Y 58 34 31 31
B 59 33 33 33Cil e s i s t a n c eCi l R e s i s t a n c e () Close
coil 48.5
Trip Coil-1 50.1
Trip Coil-2 50.4
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 46
T e s t e s u l t f F6Cr c u i t Be a k e r Location :
Transformer#1 Side.
Serial Number : 2009/IND/03/6058.
Rated Voltage : 145KV
Rated Current : 3150A
Type : 3AP1FG
Make : SEIMENS
STC : 40KAP h a s e Co s i n g /p e n i n g i m eCo s e (s )p e n
-1(s )p e n -2(s )C/(s ) R 60 33 33 31
Y 59 34 34 30
B 62 32 32 30Cil e s i s t a n c eCi l R e s i s t a n c e () Close
coil 50.9
Trip Coil-1 50.2
Trip Coil-2 50.0T e s t e s u l t f F6Cr c u i t Be a k e r
Location : Incomer#1 Tie Line Side.
Serial Number : 2009/IND/03/6060.
Rated Voltage : 145KV
Rated Current : 3150A
Type : 3AP1FG
Make : SEIMENS
STC : 40KAP h a s e Co s i n g /p e n i n g i m eCo s e (s )p e n
-1(s )p e n -2(s )C/(s ) R 57 33 34 34
Y 58 32 33 31
B 59 32 33 33Cil e s i s t a n c eCi l R e s i s t a n c e () Close
coil 50.4
Trip Coil-1 50.3
Trip Coil-2 50.6
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 47
T e s t e s u l t f F6Cr c u i t Be a k e r Location : Incomer#2
Jemina Line Side. Serial Number : 2009/IND/03/6059.
Date of Testing : 28/12/2009, 4:15pm, Sunny. Feeder Name :
CB4
Rated Voltage : 145KV
Rated Current : 3150A
Type : 3AP1FG Make : SEIMENS
STC : 40KAP h a s e Co s i n g /p e n i n g i m eCo s e (s )p e n
-1(s )p e n -2(s )C/(s ) R 59.0 28.8 60.4 29.8
Y 57.4 30.0 58.0 31.0
B 58.2 29.6 58.4 30.4Cil e s i s t a n c eCi l R e s i s t a n c e
() Close coil 48.9
Trip Coil-1 49.0
Trip Coil-2 49.0e s u l t : • The rated time for closing is
50±8 ms; therefore the value that we obtained is within the
range.
• The rated opening time is 30±4 ms; therefore the value we
obtained is within the
permissible limit.
• The rated close-open time is 30±10 ms; therefore the value
we obtained is within the
normal range.P r e c a u t i o n : • Safety the first
priority.
• Always take the steady value.
• Connect the wires properly and tightly.
• Note down the readings properly.Cn c l u s i o n :
From this field test I came to learn that the results are correct
and the SF6 circuit breaker is safe
to use. Of course one SF6 circuit breaker on Jemina side had
leakage therefore it was replaced
and tested. Rests of the circuit breaker are working fine.
Sometimes the tripping coil gets burned
often as in case of Jemina line circuit breaker, the reason being
the flow of continuous current,
low resistance of the coil and appearance of high voltage across
its terminal. For resistance
check, apply voltage across the terminals for 15s and then check
the current obtained and cross
check with the actual value.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 48
Transformer Winding Resistance A:To find out the
Winding Resistance of Transformer and of its respective CTs.b j e c
t i v e : • To check the winding resistance of Transformer in
R, Y and B phase on HV side.
• To check the winding resistance on LV side at Tap #
9.
• To check the winding resistance of WTICT, NCT and LV phase
CT.T h e o r y :There are three current transformers in 20MVA
Transformer viz. winding
temperature indicator current transformer (WTICT), Neutral current
transformer (NCT) and LV
phase current transformers. WTICT is connected to the bellow
heater in the WTI. When
transformer is loaded the current flows through the CT and flows
through the heater coil, thereby
the temperature indicated by WTI becomes the winding oil
temperature and the winding
temperature. In no load condition the WTI temperature and the OTI
temperature are same as
indicated in the dehydration curve. NCT is located below the
neutral point in secondary winding
and for each LV phases there is CT. Tap # 9 is normal position with
turn's ratio two, so whenever
we do normal test we take tap # 9. For this test we simply use
Ohm's law.T r a n s f o r m e r 1l . o . 21067/1 WTICT : 350/5A,
CL-5, 20VA.
NCT : Core (i), 400/1A, 5P10, 10VA
Core (ii), 400/1A, 5P10, 10VA
Core (iii), 400/1A, CL-PS, Vk ≥ 800V.
Imag ≤ 100mA at Vk, RCT ≤ 1.5
LV Phase CT Core (i), 400/1A, 5P10, 10VA.
Core (ii), 400/1A, 5P10, 10VA
Core (iii), 400/1A, CL-PS, Vk ≥ 800V.
Imag ≤ 100mA at Vk, RCT ≤ 1.5
Connections: WTICT (15, 16). NCT (18, 19, 20). LV R-Ph CT (21, 22,
23), LV Y-Ph CT (24,
25, 26), LV B-Ph CT (27, 28, 29).
15-2WS7,
16-2WS8
17-2WS9
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 49
Ist r u m e n t s s e d : Sl. no Description Specification Quantity
Remarks
1 AV Meter Motwane 1
2 Multimeter Digital Multimeter DM3540A,
Motwane 1
3 Connecting wires ---------------------------------------------
APRCr c u i t i a g r a m :
N.B: Part I and II refers to connections of different
experiment.
Figure 8 Measurement of Transformer winding resistance
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 50
P r o c e d u r e : 1. Disconnect the earth terminal from the
neutral point.
2. Position the tap at 01.
3. Connect a wire to the R-phase (incoming) whose end will be
connected to +ive supply
and connect a wire from the other end and connect it to
voltmeter.
4. Connect a wire to the Y-phase (incoming) whose end will be
connected to -ive supply
and connect a wire from the other end and connect it to
voltmeter.
5. Connect an ammeter to the negative wire.
6. Switch on the power supply and note down the readings on
voltmeter and ammeter.
7. Calculate the resistance from the values observed.
8. Increase the tap to next level and repeat step 1
to7.
9. Repeat the above step for Y-B and B-R phases.
10. For LV side repeat the above step for R-N, Y-N, B-N and
B-Y, however here we need
not change the tapings. Just position at the normal tap.
11. To find the winding resistance of CT connect ohmmeter
across respective terminals i.e.
15,16,17,18,19,20,21,22,23,24,24,25,26,27,28 and 29 in our
case.
12. Record the reading.e s u l t : T r a n s f o r m e r 1, l
. N. 21067/1Dt e :3/11/09, 11:00m , u n n y .- h a s e Y -Bh a s
epo s i t i o nCr r e n t(A)ol t a g e()e s i s t a n c e()po s i t
i o nCr r e n t(A)ol t a g e()e s i s t a n c e() 01 4.40 4.00
909.09 17 4.90 3.57 728.57
02 4.48 3.98 888.39 16 4.81 3.59 746.36
03 4.42 3.96 895.93 15 4.79 3.61 753.65
04 4.42 3.91 884.62 14 4.71 3.63 770.70
05 4.50 3.88 862.22 13 4.68 3.65 779.91
06 4.50 3.88 862.22 12 4.61 3.68 798.26
07 4.52 3.85 851.77 11 4.60 3.71 806.52
08 4.59 3.82 832.24 10 4.52 3.73 825.22
09b 4.60 3.79 823.91 09b 4.50 3.74 831.11
10 4.69 3.78 805.97 08 4.49 3.77 839.64
11 4.70 3.77 802.13 07 4.41 3.79 859.41
12 4.79 3.75 782.88 06 4.40 3.82 868.18
13 4.80 3.72 775.00 05 4.38 3.84 876.71
14 4.85 3.70 762.89 04 4.31 3.86 895.59
15 4.90 3.68 751.02 03 4.29 3.88 904.43
16 4.95 3.65 737.37 02 4.22 3.90 924.17
17 5.00 3.62 724.00 01 4.20 3.92 933.33
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 51
T r a n s f o r m e r 1, l . N. 21067/1Dt e :3/11/09, 11:00m , u n
n y .B- h a s e L i d e a p #9po s i t i o nCr r e n t(A)ol t a g
e()e s i s t a n c e()h a s e Cr r e n t(A)ol t a g e()e s i s t a
n c e() 01 4.42 3.80 859.73
R-N 3.59 0.2794 77.83 02 4.49 3.79 844.10
03 4.53 3.78 834.44 Y-N 7.30 0.5730 78.49
04 4.49 3.77 839.64
06 4.69 3.73 795.31
08 4.78 3.69 771.97
09b 4.80 3.66 762.50
In LV side, the Line resistance is double to that of Phase
Resistance.
10 4.84 3.65 754.13
11 4.89 3.64 744.38
12 4.93 3.62 734.28
13 4.99 3.60 721.44
14 5.01 3.57 712.57
15 5.06 3.55 701.58
16 5.12 3.52 687.50
17 5.19 3.49 672.45T r a n s f o r m e r 1, l . N. 21067/1.Nu t r a
l C (NC)W T ICBN. i r e Cd e e s i s t a n c e ()BN. i r e Cd e e s
i s t a n c e () 18 2S1-2S2 15 2WS7
19 2S3-2S4 16 2WS8
20 2S5-2S6 16 2WS8L h a s e Cs 17 2WS9T BN.Wire Code Resistance ()
15 2WS7
21 2US1-2US2 17 2WS9
wires alternatively.
23 2US5-2US6
24 2VS1-2VS2
25 2VS3-2VS4
26 2VS5-2VS6
27 2WS1-2WS2
28 2WS3-2WS4
29 2WS5-2WS6
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 52
T r a n s f o r m e r 2, l . N. 21067/2Dt e :4/11/09, 12:40m , u n
n y .- h a s e Y -Bh a s epo s i t i o nCr r e n t(A)ol t a g e()e
s i s t a n c e()po s i t i o nCr r e n t(A)ol t a g e()e s i s t a
n c e() 01 3.62 3.150 870.17 01 3.63 3.175 874.66
02 3.68 3.130 850.54 02 3.69 3.150 853.66
03 3.70 3.110 840.54 03 3.70 3.130 845.95
04 3.62 3.090 853.59 04 3.71 3.110 838.27
05 3.76 3.060 813.83 05 3.74 3.090 826.20
06 3.79 3.037 801.32 06 3.79 3.070 810.03
07 3.80 3.018 794.21 07 3.80 3.050 802.63
08 3.85 2.998 778.70 08 3.81 3.030 795.28
09b 3.90 2.977 763.33 09b 3.84 3.000 781.25
10 3.95 2.974 752.91 10 3.89 2.990 768.64
11 3.99 2.952 739.85 11 3.90 2.960 758.97
12 4.00 2.930 732.50 12 3.92 2.940 750.00
13 4.01 2.905 724.44 13 3.97 2.915 734.26
14 4.05 2.880 711.11 14 3.99 2.892 724.81
15 4.10 2.850 695.12 15 4.00 2.869 717.25
16 4.12 2.030 492.72 16 4.02 2.844 707.46
17 4.19 2.000 477.33 17 4.09 2.813 687.78T r a n s f o r m e r 2, l
. N. 21067/2Dt e :4/11/09, 12:00m , u n n y .B- h a s e L i d e a p
#9po s i t i o nCr r e n t(A)ol t a g e()e s i s t a n c e()h a s e
Cr r e n t(A)ol t a g e()e s i s t a n c e() 01 3.58 3.190
891.06
R-N 4.32 0.352 81.48 02 3.60 3.170 880.56
03 3.62 3.140 867.40 Y-N 4.35 0.353 81.15
04 3.68 3.110 845.11
06 3.78 3.060 809.52
08 3.81 3.008 789.50
09b 3.80 3.004 790.53
In LV side, the Line resistance is double to that of
Phase Resistance.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 53
T r a n s f o r m e r 2, l . N. 21067/2.Nu t r a l C (NC)W T ICBN.
i r e Cd e e s i s t a n c e ()BN. i r e Cd e e s i s t a n c e ()
18 2S1-2S2 2.6 15 2WS7
2.6 19 2S3-2S4 2.4 16 2WS8
20 2S5-2S6 2.6 16 2WS8 1.7L h a s e Cs 17 2WS9T BN.Wire Code
Resistance () 15 2WS7 1.9
21 2US1-2US2 3.5 17 2WS9
22 2US3-2US4 2.3
wires alternatively.
23 2US5-2US6 2.6
24 2VS1-2VS2 2.4
25 2VS3-2VS4 2.5
26 2VS5-2VS6 2.8
27 2WS1-2WS2 1.2
28 2WS3-2WS4 2.4
29 2WS5-2WS6 2.4P r e c a u t i o n s : • Safety of
experimenter the first priority.
• Always adjust the DC voltage level as per the ranges of the
meters used.
• Avoid parallax error.Cn c l u s i o n : From this field
test, the winding resistances of CTs are below 1.5. As indicated on
the name
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 54
Transformer Testing (I Ce c k , a t i o Ce c k , Mg n e t
i z i n g Bl a n c e Ce c k , Mg n e t i z i n g Cr r e n tCe c k ,
e c t o r Go u p Ce c k )A: 1. To check the 'Insulation
Resistance' of the Transformer.
2. To check the 'Ratio of HV-LV winding'.
3. To check the 'Magnetizing Balance' or 'Core Balance'.
4. To check the 'Magnetizing Current'.
5. To check the 'Vector Group'. b j e c t i v e s :
To find out the insulation resistance between HV-Earth,
LV-Earth and HV-LV terminals
and to ensure there is no leakage to earth i.e. continuity
check.
To ensure that the turns ratio for each tapping is in
accordance to the name plate rating.
To ensure that the magnetic balance is not disturbed.
To observe the no load magnetizing current.
To ensure the vector group DYN 11.T h e o r y :I.Is u l a t
i o n e s i s t a n c e e s t Insulation resistance of a
two-winding transformer insulation system, HV to ground, LV to
ground, and HV to LV is determined with a Megger type of
instrument. Historically,
insulation resistance measurements are also made to assess the
amount of moisture in
transformer insulation. However, the measurement of insulation
dissipation factor has shown to be a better indicator of the
overall condition of insulation in a power
transformer.II.R a t i o e s t The purpose of this test is to
ensure that all windings have the correct number of turns
according to the design. Since the transformer is equipped with a
load tap changer (LTC),
ratio tests is also carried out at the various positions of the tap
changer(s). The objective of ratio tests at different tap positions
is to ensure that all winding taps are made at the
correct turns and that the tap connections are properly made to the
tap changing devices.
ANSI/IEEE general standard [1] requires that the measured voltage
ratio between any two windings be within ± 0.5% of the value
indicated on the nameplate. To verify this
requirement, ratio tests are performed in which the actual voltage
ratio is determined
through measurements. Ratio tests can be made by energizing the
transformer with a low AC test voltage and measuring the voltage
induced in other windings at various tap
indicated on the transformer's nameplate. More commonly,
Transformer Turns Ratio
(TTR) test sets are used for making the tests.III.Mg n e t i z i n
g Bl a n c e e s t This test is performed to ensure that the HV and
LV windings are not displaced from its
original 120º displacement from respective phases.
In this, two phase supply is applied to one of the winding and the
induced voltages on the
other two windings are measured. The voltage applied on the
windings should be the sum
of the voltage induced on other two windings. If the phase
displacements are correct then
the flux distribution on each winding will also be proportionate
i.e. upon repeating the
applied voltage to other phases too, the sum of induced voltages
should be equal to the
applied voltage. In the readings one will see the maximum value
being in the diagonal.
In case of LV side which is star connected, magnetic balance test
ensures that the
windings are not displaced with respect to the neutral point. If
windings are displaced
from each other then we say neutral is displaced, which means some
currents are flowing
in the neutral point (Earth Fault). By KCL, current flowing in the
neutral point should be
zero at balanced condition however practically it is not true.
Therefore in order to satisfy
this condition neutral point is grounded so that any current
flowing through neutral point
goes to earth. Here too the diagonal characteristic is
observed.I.Mg n e t i z i n g Cr r e n t Ce c k This test ensures
that the magnetizing current under no load condition doesn’t exceed
4%
of the rated current. When voltage is applied to the exciting or
primary winding of the transformer, a magnetizing current flows in
the primary winding which produces the flux
in the core. The flow of flux in magnetic circuits is analogous to
the flow of current in
30° Lag or +30°
Magnetizing Current
V .V e c t o r Go u p Ce c k This test is from the design point of
consideration and is required to check the vector
group indicated on the name plate of the transformer. There are
various vector groups and
in our case the transformer is Dy11. Some of the typical examples
are as follows.
The vector diagram for Dy11 is shown below.
Here, RYB forma an equilateral triangle.
R-b=R-y, Y-b=Y-y, R-Y=R-N+Y-N, B-y is the shoot point.
This confirms the Dy11 vector group test.
Dy11
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 57
Ist r u m e n t e q u i r e d :l. o Dsc r i p t i o n S p e c i f i
c a t i o n Q u a n t i t y e m a r k s 1 Motorized Megger
5KV, 0-10000M, Sl. no. 850302, WACO
1
Motwane 1
4 Testing Board MCB C16 attached, handmade 1 See picture
5 Connecting wires 2.5 sq.mm APR
6 Transformer Sl. no 21067/1, 20MVA 1
7 3- Supply 415V, 50Hz 1
8 AV Meter AC/DC Range 1
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 58
P r o c e d u r e :I.Is u l a t i o n e s i s t a n c e Ce c k
a. Connect wires from HV, LV and Earth terminals.
b. Use 5KV Motorized Megger with external power
supply.
c. Connect HV and Earth terminals to the Megger. Switch on
the power supply and
note down the readings indicated on the Megger at 15 th
and 60 th
seconds.
d. Switch off the Megger and discharge the current in the
lines used by shorting the
terminals to avoid risk of shock.
e. Connect LV and Earth terminals to the Megger. Switch on
the power supply and
note down the readings indicated on the Megger at 15 th
and 60 th
f. Repeat step d.
g. Connect HV and LV terminals to the Megger. Switch on the
power supply and
note down the readings indicated on the Megger at 15 th
and 60 th
h. Repeat step d.
i. Calculate R 15/R 60 and then tabulate the
readings.II.R a t i o e s t a. Connect the circuit diagram as
in the figure above.
b. Disconnect the neutral from Earth terminal.
c. Apply 3- power from nearby BMK to the connection
board.
d. Since the transformer has 17 taps, begin one by one.
e. Positioning the tap at 01, check the voltage at HV side,
LV side (line as well as
phase voltage) and note down the readings.
f. Increase the tap to next level and then repeat step
'e'.
g. Repeat step 'f' till the highest tap.
h. Tabulate the readings for further analysis.III.Mg n e t i
z i n g Bl a n c e Ce c k (Cr e Bl a n c e ), a p #9. a. The
experiment continues from above tests.
b. Make sure that the table for recording data is made
sequentially.
c. Switch on the power supply and always work offline.
d. Remove the HV B-phase out and then measure the voltage on
HV lines and LV
side (Line as well as phase voltages).
e. Remove the HV R-phase out and then measure the voltage on
HV lines and LV
side (Line as well as phase voltages).
f. Remove the HV Y-phase out and then measure the voltage on
HV lines and LV
side (Line as well as phase voltages). Switch off the power
supply.
g. Record the data sequentially and correctly.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 59
I.Mg n e t i z i n g Cr r e n t Ce c k (N o a d u r r e n t ), p
#9. a. Reconnect every connection as shown in the circuit
diagram.
b. Switch on the power supply but while changing
the connections switch it off.
c. Disconnect the R-phase on HV side and then measure the
current on R-phase
itself. Record the voltage on R-Y phase too. Use Clamp
leaker.
d. Reconnect R-phase and disconnect the Y-phase on HV side.
Measure the current
on Y-phase itself. Record the voltage on Y-B phase too. Use Clamp
leaker.
e. Reconnect Y-phase and disconnect the B-phase on HV side.
Measure the current
on B-phase itself. Record the voltage on Y-B phase too. Use Clamp
leaker.
f. Disconnect HV side and give the supply to LV
terminals.
g. Use clamp leaker to measure the current in the
lines.
h. Disconnect the r-phase on LV side and then measure the
current on r-phase itself.
Record the voltage on r-y phase too.
i. Reconnect r-phase and disconnect the y-phase on LV side.
Measure the current on
y-phase itself. Record the voltage on y-b phase too.
j. Reconnect y-phase and disconnect the b-phase on LV
side. Measure the current
on b-phase itself. Record the voltage on b-r phase too.
k. Observe the readings very carefully such that the
magnetizing current is not less
than 4% of the actual rated current in both the cases.V .V e c t o
r Go u p Ce c k , a p #9. a. Reconnect every connection as
shown in the circuit diagram.
b. Here we need to check the name plate rating. The
vector Group is Dy11 so we
need to prove this. Refer the vector diagram given in theory.
c. Short the R-phase of HV and LV terminals.
d. Apply voltage on HV side.
e. Check the voltage R-Y, Y-B, B-R, R-n, Y-n, R-b, R-y, Y-b,
Y-y, B-b and B-y
terminals.
f. Check if the results are matching with that given in
theory.P r e c a u t i o n s : 1. Safety of experimenter the
first priority.
2. While Meggering, always discharge the current to avoid
shock.
3. Always switch off the power supply when connecting the
circuit to avoid spark.
Insulation Resistance Values of Power Transformers (M)
Class Winding Temperatures °C
33-132KV 20°C 30°C 40°C 50°C 60°C 70°C
R15 450 300 200 140 60 40
R60 900 600 400 280 120 50
R60-Value of IR at 60sec & R15 at 15 sec. after the application
of test voltage of Megger
Courtesy: Installation, commissioning and maintenance of electrical
equipment, Tarlok Singh
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 60
R e s u l t :R ANFR ME #1, l . o 21067/1r a n s f o r m e r e s t i
n g , l . N. 21067/1Dt e :30/10/2009, 12:00m , u n n y .Is u l a t
i o n e s i s t a n c e (I)Ce c k y 5K Mt o r i z e d Mg g e r (M)
Terminals IR-R 60 IR-R 15 R
15/R 60
HV-Earth 10000+∞ 10000 1
HV-LV 10000+∞ 5000 0.5
LV-Earth 10000+∞ 8000 0.8T r a n s f o r m e r e s t i n g ,
l . N. 21067/1Mg n e t i z i n g Bl a n c e Ce c k (a p #9)r Cr e
Bl a n c e
-out R-Y(V) Y-B(V) B-R(V) r-y(V) y-b(V) b-r(V) r-n(V) y-n(V)
b-n(V)
B 416.0 318.0 98.3 213.5 65.4 148.1 120.0 93.1 28.5
R 216.7 417.0 201.6 184.5 180.1 10.19 62.5 121.3 59.9
Y 81.4 335.4 416.0 78.4 219.6 145.2 23.96 97.3 121.4T r a n s f o r
m e r e s t i n g , l . N. 21067/1Mg n e t i z i n g Cr r e n t Ce
c k (a p #9)r N Ld Cr r e n tH i d e L i d e -out
Applied Voltage(V)
Current (mA) -out Applied
Voltage (V) Current (mA)
R R-Y 417.0 R-ph 3.50 r r-y 417.0 r- ph 9.63
Y Y-B 415.0 Y-ph 2.46 y y-b 415.0 y- ph 6.30
B B-R 416.0 B-ph 2.49 b b-r 416.0
b- ph 9.82T r a n s f o r m e r e s t i n g , l . N.
21067/1V e c t o r Go u p Ce c k (a p #9), D11 Terminals
Voltage(V)
R-b=R-y, Y-b=Y-y,
B-y is the shoot point. These conditions are found correct.
R-Y 416.0
Y-B 417.0
B-R 417.0
R-N 121.8
Y-N 300.0
B-b 261.0
B-y 475.0
R-b 208.2
R-y 208.5
Y-b 259.4
Y-y 259.4
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 61
a t i o e s t f r a n s f o r m e r #1, l . o 21067/1p H ()i d e(o
l t s )L (t a r )i d e(o l t s )At u a la t i o a t i o %Er o rBB
H/Lp h Y p h Bh R p h p h Bh 01 415 415 415 189.6 191.9 189.3 109.4
110.1 110.3 2.202.19 2.16 2.19 -0.45% -1.82% -0.45%
02 413 416 416 190.8 193.3 191.2 110.6 111.2 111.4 2.182.16 2.15
2.18 -0.92% -1.38% 0.00%
03 415 415 416 193.3 194.6 193.6 111.9 112.6 112.8 2.152.15 2.13
2.15 0.00% -0.93% 0.00%
04 413 417 415 195.3 197.3 196.9 113.4 114.0 114.2 2.132.11 2.11
2.11 -0.94% -0.94% -0.94%
05 415 416 415 198.1 199.5 198.2 114.8 115.4 115.6 2.102.09 2.09
2.09 -0.48% -0.48% -0.48%
06 417 415 416 200.3 201.3 200.4 116.1 116.9 116.9 2.082.08 2.06
2.08 -0.00% -0.96% 0.00%
07 415 416 417 202.9 204.5 203.4 117.7 118.3 118.3 2.052.05 2.03
2.05 -0.00% -0.98% 0.00%
08 415 416 417 205.7 206.6 206.2 119.5 119.6 119.9 2.032.02 2.01
2.02 -0.49% -0.99% -0.49%
9b 414 415 416 208.0 209.2 208.5 120.6 121.2 121.3 2.001.99 1.98
2.00 -0.50% -1.00% 0.00%
10 417 417 418 210.0 212.3 211.5 122.0 122.5 122.3 1.981.99 1.96
1.98 +0.51% -1.01% 0.00%
11 418 416 417 213.2 215.0 214.3 123.6 124.4 124.5 1.951.96 1.93
1.95 +0.51% -1.03% 0.00%
12 414 416 418 215.7 217.3 216.8 125.3 125.5 126.2 1.931.92 1.91
1.93 -0.52% -1.04% 0.00%
13 414 415 416 218.9 220.3 219.7 126.9 127.4 127.7 1.901.89 1.88
1.89 -0.53% -1.05% -0.53%
14 417 417 416 221.9 223.3 222.7 129.0 129.2 129.5 1.881.88 1.87
1.87 0.00% -0.53% -0.53%
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 62
T R ANFR ME #2, L. N. 21067/2r a n s f o r m e r e s t i n g , l .
N. 21067/2Dt e :4/11/2009, 10:00m , u n n y .Is u l a t i o n e s i
s t a n c e (I)Ce c k y 5K Mt o r i z e d Mg g e r (M) Terminals
IR-R 60 IR-R 15 R
15/R 60
HV-Earth 6000 10000 1.67
HV-LV 5000 10000 2.00
LV-Earth 9000 10000 1.11T r a n s f o r m e r e s t i n g , l . N.
21067/2Mg n e t i z i n g Bl a n c e Ce c k (a p #9)r Cr e Bl a n c
e
-out R-Y(V) Y-B(V) B-R(V) r-y(V) y-b(V) b-r(V) r-n(V) y-n(V)
b-n(V)
B 421.0 349.0 72.60 223.3 81.6 142.0 121.7 101.7 21.03
R 209.0 422.0 213.1 182.5 183.4 477 60.0 121.8 61.40
Y 60.20 356.0 421 85.8 223.9 138.5 17.78 103.2 120.8T r a n s f o r
m e r e s t i n g , l . N. 21067/2Mg n e t i z i n g Cr r e n t Ce
c k (a p #9)r N Ld Cr r e n tH i d e L i d e -out
Applied Voltage(V)
Voltage(V) Current (mA)
R R-Y 422.0 R-ph 3.90 r r-y 422.0 r- ph 11.0
Y Y-B 423.0 Y-ph 2.00 y y-b 421.0 y- ph 6.50
B B-R 423.0 B-ph 2.20 b b-r 423.0
b- ph 11.0T r a n s f o r m e r e s t i n g , l . N.
21067/1V e c t o r Go u p Ce c k (a p #9), D11 Terminals
Voltage(V)
R-b=R-y,
R-Y 420.0
Y-B 421.0
B-R 423.0
R-N 122.10
Y-N 299.0
B-y 475.0
R-b 210.5
R-y 211.4
Y-b 261.6
Y-y 261.3
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 63
a t i o e s t f r a n s f o r m e r #2, l . o 21067/2p H ()i d e(o
l t s )L (t a r )i d e(o l t s )At u a la t i o a t i o %Er o rBB
H/Lp h Y p h Bh R p h p h Bh 01 422 421 422 191.6 190.9 191.0 110.9
111.3 110.7 2.202.20 2.21 2.21 +0.11% +0.24% +0.43%
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 64
R e s u l t: The field testing of the ratio of HV/LV at
various tapings is found correct with slight
errors.
The phase voltage of secondary is also found to be 1/√3 times that
of line voltage.
The actual ratio at normal tap is 2 i.e. 66/33KV.
It is observed in the magnetizing balance check that the maximum
voltage exists across
the diagonal element for HV and LV phase voltage.
NB: If the diagonal characteristics holds true for the phase
voltages at LV side then it
is true for HV side. Further Vector Group check will also hold
true.
The vector group check for Dy11 also proved the equations or the
vector characteristic
given. Cnc l u s i o n: From the above field test it is proved
that the results obtained are tallying with the name plate
ratings. Ratios at various taps are correct with some errors. The
windings at the core are also
balanced at 120° from each other. The magnetizing current as
observed during the field test is far
below 4% of the actual rated current. No load current should
not exceed above 4% of the actual
rated current. It is observed that in the Y phase the current is
comparatively less. The reason
being, the Y phase winding lies at the middle so the flux
gets distributed equally to other
windings too thereby resulting in low currents. Whereas in other
case very less flux gets to the
third winding (see the fig. below). The vector group is found to be
Dy11. There are a total of
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 65
Transformer Oil Testing A :Dehydration &
filtration of Transformer oil in the Transformer.b j e c t i v e :
1. To remove the moisture present in the core, windings,
tank, radiator and the conservator
tank.
2. To check the insulation resistance (IR Value) of the
Transformer using Megger and
observe the reading.
3. Check the Breakdown Voltage value (BDV) of the dehydrated
oil.T h e o r y :After the erection of Transformer at site,
dehydration and filtration of oil is very
important. Here 'Transformer Oil Conditioning Machine' is used.
There are two outlets in this
machine; one is used as incoming oil source and the other acts as
outgoing source. After
connecting one pipe to the transformer tank and the other to the
oil barrel start the machine and
fill the transformer with oil. Don’t fill it fully; as transformer
oil gets heated its volume expands.
Now connect both pipes to transformer where one draws oil
from the transformer and the other
pumps in the dehydrated oil coming from the Transformer oil
conditioning machine. There are
moistures present in core and windings. When the oil is heated, by
virtue of core and windings
being immersed in the oil, it gets heated. As a result of
this the moisture present, in the core and
windings vaporize out and gets mixed with the oil. This oil is then
passed into the oil
conditioning machine. The oil passes through 'degassing chamber' in
two stages where the oil is
set to flow in the form of fountain. When this process happens the
moisture is sent out from the
oil which is then sucked by the vacuum pump. The oil further passes
through heater and filter
vessel where the oil gets heated and gets filtered of carbon
deposits, dirt, sludge, etc. particles.
The oil is again pumped in the transformer. It heats the core and
the process continues. During
the process of Transformer Oil Conditioning, check the IR value of
the transformer every after
one hour. Theoretically the Megger value should come down and then
rise up until it attains a
stable value. When it attains stable value for multiple Meggering
then it shows that the oil is
dehydrated. Then collect sample oil for BDV test. The BDV value
shouldn’t come below 60KV.
While Meggering we go with checking the insulation resistance value
of primary-earth,
secondary-earth and primary-secondary winding (see fig. 1). The
theory behind is as follows;
Primary-Earth :Basically we are observing the change
in the characteristics of the
insulation resistance between primary winding and the earth. The IR
value of primary to earth
will be high before conditioning. When the conditioning of the oil
is started the moisture gets
removed and the value comes down. Upon further conditioning the IR
value will go up
indicating that there is no conduction path from primary to earth.S
e c o n d a r y -Er t h : Here we are checking the insulation
resistance between secondary
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 66
Time
I a l u e r y -e cI a l e e c -Er t hI a l u e r y -Er t h r i m a
r y-e c o n d a r y : The insulation resistance of
primary-secondary is observed. Upon
heating, dehydrating and filtering, the IR value should come down
and the rise up until it attains
a stable value. Thus moisture is indicated, vaporized and removed
out.
Fig. 1S a m p l e Ga p h
I R V
a l u e
0
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 67
Ist r u m e n t s s e d:l. o Dsc r i p t i o n S p e c i f i c a t
i o n Q u a n t i t y e m a r k s 1
Transformer oil conditioning machine
1 Set
Motwane 1
WACO 1
4 Connecting wires 2.5 sq.mm APRCr c u i t i a g r a m Transformer
Oil Conditioning Machine
Motorized Megger Internal diagram
Er t hLH
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 68
P r o c e d u r e :AI 1. Connect the pipes at respective
inlet and outlet of the Transformer oil conditioning
machine.
2. Connect the other end to the oil drum and the inlet to the
'Top Oil Filter Valve' of the
transformer tank.
3. Start the machine and fill up the transformer to certain
level but not fully so that when at
peak temperature of the oil the volume expanded will not
overflow the oil from the
transformer.
4. When heating the oil, please observe the source load and
the load that the one heater
absorbs. (In our case the source load was 130A whereas each heater
consumes 80A.
There are three heaters, so we were bound to switch on only one
heater.)
5. Now for dehydration and filtration, connect the pipe
connecting the oil drum to the
'Bottom Oil Filter Valve' of the transformer tank.
6. Start the machine with one heater being switched on.
7. Disconnect the earth terminal from the neutral point.
Start Meggering with HV-Earth,
LV-Earth and HV-LV and record the reading every one hour until the
readings comes
down and rise up to attain a stable value. N.B The process may go
on for two to three
days. Then put off the heater and cool the oil with machine under
running condition.
8. Take the oil sample (two bottles) for Breakdown Voltage
test. The average of six
readings obtained should be above 60KV. This ends the dehydration
and filtration test.P AT II(BD e s t ) 1. Arrange the BDV
testing kit (Automatic Oil Test Set OTS100AF/Megger)
2. Wash the oil container thoroughly with oil form one
bottle.
3. Pour the oil sample from other bottle and place it in the
testing kit.
4. Adjust the space between the electrodes to 2.5mm.
5. Keep it idle for 15minutes so that the oil sample settles
down.
6. Set the standard to IEC 156 1995 and then press the button
to apply voltage.P r e c a u t i o n : Safety of the
experimenter the first priority.
Make sure not to fill the transformer tank fully so that the
oil will not overflow when
heated at peak temperature.
Drying of a transformer must be done under continuous and
competent supervision.
Careful observation of temperature is essential during
drying as high temperature can
result in damage to the insulation.
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 69
R e s u l t s :Dh y d r a t i o n n d Fl t r a t i o n f r a n s f
o r m e r i lr a n s f o r m r #1, 20MA, 66/33K, l . o . 21067/1.Dt
e /i m eI y 5K Mt o r i z e d Mt o r(M) T e m p e r a t u r e
(C)
Date Time HV-Earth LV-Earth HV-LV Machine oil OTI WTI Remarks
2 6 / 1 0 / 2 0 0 911:56am
10000 10000 8000 35 34 31
6 0
C .
4 : 2 0 ,
, .
1:25pm 10000 10000 10000 38 38 38
2:30pm 10000 10000 10000 42 39 40
3:30pm 10000 10000 10000 51 46 45
5:18pm 10000 10000 10000 52 48 47
6:20pm 10000 10000 10000 56 51 50
7:25pm 10000 10000 10000 60 54 52
10:30pm 8000 8000 8000 60 56 54
2 7 / 1 0 / 2 0 0 9
12:30am 8000 8000 8000 60 57 55
2:35am 7000 7000 7000 60 57 55
4:30am 7000 7000 7000 60 57 55
6:30am 7000 7000 7000 60 57 55
8:30am 7000 7000 7000 60 57 55
9:30am 7000 8000 9000 60 58 58
10:30am 8000 10000 10000 60 59 59
11:30am 9000 10000 10000 60 59 59
12:30am 7000 9000 10000 60 59 59
1:30pm 7000 9000 10000 60 60 60
2:30pm 7000 9000 10000 60 60 60
3:30pm 8000 10000 10000 60 60 60
4:30pm 8000 10000 10000 60 60 60
5:30pm 8000 10000 10000 60 59 60
6:30pm 8000 10000 10000 60 59 60
7:30pm 8000 10000 10000 60 59 60
8:30pm 8000 10000 10000 60 59 60
9:30pm 8000 10000 10000 60 59 60
10:30pm 8000 10000 10000 60 59 60
11:30pm 8000 10000 10000 60 59 60
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 70
Dhy d r a t i o n n d Fl t r a t i o n f a n s f o r m e r i lr a n
s f o r m e r #1, 20MA, 66/33K, l . o . 21067/1.Dt e /i m eI y 5K
Mt o r i z e d Mt o r(M) T e m p e r a t u r e (C)
Date Time HV-Earth LV-Earth HV-LV Machine oil OTI WTI Remarks
2 8 / 1 0 / 2 0 0 9
12:30am 8000 10000 10000 60 59 60
1 : 3 0 ,
, . 2 : 1 0 , M
.1:30am 8000 10000 10000 60 59 60
2:30am 8000 10000 10000 60 59 60
3:30am 8000 10000 10000 60 59 60
4:30am 8000 10000 10000 60 59 60
5:30am 8000 10000 10000 60 59 60
6:30am 8000 10000 10000 60 59 60
7:30am 8000 10000 10000 60 59 60
8:30am 8000 10000 10000 60 59 60
9:30am 8000 10000 10000 60 59 60
10:30am 8000 10000 10000 60 59 59
11:30am 8000 10000 10000 60 59 59
12:30pm 8000 10000 10000 60 59 59
2:30pm 10000 10000 10000 60 56 56
3:30pm 10000 10000 10000 60 55 56
4:30pm 10000 10000 10000 60 54 56
5:30pm 10000 10000 10000 60 54 55
6:30pm 10000 10000 10000 60 52 54R a d i a t o r sa d i a t o r p e
n (i m e)Co s e (i m e) R e m a r k s 1 10:15am 10:50am Al a d i a
t o r s p e n e d n 28/10/2009t6:30m . Ha t e r w i t c h e d f f n
d o o l i n gf h e i l t a r t e d i t h a c h i n e n d e ru n n i
n g o n d i t i o n . Mch i n e t o p p e d t29/10/2009t 9:45m . i
l a m p l e a k e no r BD e s t t MD, e m t o k h a .
OLTC Filtration started at 4:00pm till
6:00pm on 29/10/2009.
2 11:00am 11:40am
3 12:30pm 1:30pm
4 1:30pm 2:40pm
5 2:40pm 3:10pm
6 3:10pm 3:40pm
7 3:40pm 4:10pm
8 4:10pm 4:40pm
9 5:10pm 5:40pm
10 6:10pm 6:30pm
66KV/33KV, Olakha Sub Station, Thimphu.
[email protected]
Page 71
0
2000
4000
6000
8000
10000
12000
I T i m e
T r a n s f o r m e r i l Ca r a c t e r i s t i c Cr v eH-Er t h
Transformer Oil Characteristic
Curve
Bea k d o w n o l t a g e e s t f h e a m p l e i l a k e n r o m r
a n s f o r m e r#1.Dt e :29/10/2009, 10:55m t e m t o k h a .Ep e
r i m e n t e r :e m a Jm p e l . Eu i p m e n t :At o m a t i c i
l e s t e t (T S 100AF/Mg ge a d i n g s T i m e (Mu t e s ) BD(K)
1
st Reading 5 84.8
6 th
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 72
0
2000
4000
6000
8000
10000
12000
Transformer Oil Characteristic Curve LVEarth
Transformer Oil Characteristic
Curve LVEarth
I T i m e
66KV/33KV, Olakha Sub Station, Thimphu.
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Page 73
Dhy d r a t i o n n d Fl t r a t i o n f r a n s f o r m e r i lr a
n s f o r m e r #2, 20MA, 66/33K, l . o . 21067/2.Dt e /i m eI y 5K
Mt o r i z e d Mt o r(M) T e m p e r a t u r e (C)
Date Time HV-Earth LV-Earth HV-LV Machine oil OTI WTI Remarks
3 0 / 1 0 / 2 0 0 9
1:00pm 10000 10000 10000 - 38 38
1 : 0 0 , F
.
A
3 : 0 0 3 1 / 1 0 / 0
9 .
2:00pm 10000 10000 10000 42 40 42
3:00pm 10000 10000 10000 43 40 42
4:00pm 10000 10000 10000 44 43 44
5:00pm 10000 10000 10000 50 48 49
6:00pm 10000 10000 10000 55 53 54
7:00pm 8000 8000 8000 57 54 55
8:00pm 8000 7000 8000 60 55 56
9:00pm 8000 7000 8000 60 56 57
10:00pm 8000 7000 8000 60 56 57
11:00pm 8000 7000 8000 60 56 57
3 1 / 1 0 / 2 0 0 9
12:00am 7000 7000 7000 60 56 57
1:00am 7000 7000 7000 60 57 58
2:00am 7000 7000 7000 60 57 58
3:00am 7000 7000 7000 60 57 58
4:00am 7000 7000 7000 60 58 58
5:00am 7000 7000 7000 60 59 59
6:00am 7000 7000 7000 60 60 60
7:00am 6000 7000 7000 60 61 61
8:00am 6000 7000 7000 60 62 62
9:00am 6000 7000 7000 60 62 62
10:00am 6000 7000 7000 60 62 62
11:00am 6000 7000 7000 60 62
62 1 / 1 1 / 2 0 0 912:00pm
7000 8000 8000 60 63 63
1:00pm 7000 8000 8000 60 63 63
2:00pm 7000 8000 8000 60 63 63
3:00pm 7000 8000 8000 60 63 63