distribution transformer failures and counter measures · o transformer failure causes black-out of...
TRANSCRIPT
Distribution Transformer Failures and
Counter Measures
Dr. Katsutoshi Toda Executive Chairman,
Toshiba Transmission & Distribution Systems (India) Pvt. Ltd.
Performance, Customer Satisfaction & Profitability of any
Distribution Network completely depends on functional
performance of Distribution Transformer
Role of Distribution Transformer In Network
o A simple Internal (or) External fault which obstructs functioning of transformer in
network.
o Transformer failure causes black-out of power to the whole area.
o It can also lead to risk of fire and explosions, as the transformers contains
substantial quantity of oil.
o Though it looks simple, transformer failure will lead to chain of adverse effects
on:
End User
Distribution Utility Company
--------------------------------------------------------------------------------------------------------------------------What is Distribution Transformer Failure
Types & Sources of Distribution Transformer Failure
Improper
installation
Improper
terminations
Faulty earth
connections
Bypassing of
Protection
systems
Inadequate
maintenance
Prolonged Over
loading &
Unbalancing
Faulty design
Quality of Raw
Materials
Poor workmanship
Improper Mfg.
Process
Improper
transportation
Chances for Under-
rated Transformers
Improper
Technical Specifications
Improper
Inspection
Process
Source -2
Network OperatorSource -3
Manufacturer
Source -4
Procurement Stage
Unauthorized
Tapping
Vandalism
Oil Leakages
Faults on LV
System
Lightening
Strikes
External short-
circuit
Source -1
External Conditions
Few Examples indicating Improper Installation and Operating
Conditions
Unauthorized Tapping (Power Theft)--------------------------------------------------------------------------------------------------------------------------
Improper Termination--------------------------------------------------------------------------------------------------------------------------
Improper Earthing--------------------------------------------------------------------------------------------------------------------------
Bypassing of Protection SystemsLow voltage Terminal Connection provided directly bypassing MCCB
Failure due to Overloading--------------------------------------------------------------------------------------------------------------------------
Arcing Horns - Improper Assembly/Not used--------------------------------------------------------------------------------------------------------------------------
Failures due to Low Oil Level resulted from Oil Leakage--------------------------------------------------------------------------------------------------------------------------
0.00%
5.00%
10.00%
15.00%
20.00%
25.00%
30.00%
35.00%
Ligh
tnin
g St
rike
s
Van
dal
ism
Fau
lt o
n L
V S
yste
m
Bro
ken
Bu
shin
gs
Bu
rnt/
Bro
ken
Ro
ds
Oil
Leak
age
Acc
ide
nta
l Dam
age
Ove
rlo
ad
Faile
d o
n C
om
mis
sio
nin
g
Inte
rnal
De
fect
s
13.88%10.59%
32.19%
3.55%
9.52%11.33%
0.93%
5.42%
1.51%
11.08%
Dist. Trfr Failure Statistics in Kenya(Aug-2015 to Dec-2016)
--------------------------------------------------------------------------------------------------------------------------
Kenya Power is the main distributor of electricity in Kenya.
It has Installed around 59000 Nos distribution transformers in network
The approx. failure rate is 7-8%
(Sh
ort
Cir
cuit
)
Source: M/s. KPLC, Kenya.
What Next?
Can we really control these failures?
Counter Measures to overcome Transformer failures
Source: External Conditions
Pro
ble
m
Training on
Installation,
Operation &
Maintenance
All Technical
measures to be
incorporated in
Specifications.
Way ForwardSolution
Unauthorized
Tapping
Vandalism
Oil Leakages
Faults on LV `System
Lightening Strikes
External short-circuit
Proper Maintenance
and Checks to be
done.
Transformer should
be manufactured with
Anti-Theft
arrangements.
Aluminium Winding
may be one of the
Solutions to prevent
Vandalism
Sources of Failures & Counter Measures
Source: Network Operator
Know the Right
Practices of
Installation and
Maintenance
Improve Skill Levels
of Operation and
Maintenance Staff.
Pro
ble
m
Training for the field Engineers
and Staff.
Way ForwardSolution
Improper installation
Improper terminations
Faulty earth
connections
Bypassing of
Protection systems
Inadequate
maintenance
Prolonged Over
loading & Unbalancing
Someof the counter
measures
Sources of Failures & Counter Measures
Example Measure-1: LV Termination through MCCB for Overload Protection
Don’t
bypass
MCCB
Cables connected to transformer
LT cables towards Customer end
LT cables connected to MCCB through rubber grommet
LT cable passing through MCCB (bottom view)
LT terminals should connect through MCCB only
()
()
Do’s:
Always connect LT terminals through MCCB to
protect transformer from overloading & external
faults on LT side.
Don’ts:
Do not bypass MCCB to avoid transformer
tripping in fault conditions
()
()
Do’s Don'ts
Example Measure-2: Arcing Horns Assembling Procedures
85mm
Do’s : Ensure the assembling of top and bottom arcing horns alignment with 85mm gap for 11KV.
Don’ts: Never assemble arcing horns in misaligned or missing condition as shown in above
photos.
© 2015 Toshiba Corporation
()
Connect HT lead and terminal stem through Fuse link
Don’t Bypass Fuse link
Don’t Fix HT lead directly to terminal stem without fuse link
Do’s Don'ts
Example Measure-3: HT Fuse link connecting procedures
Do’s:Always connect HT phase leads through fuse links to avoid transformer failures due to overload or fault
currents.
Don’ts : Never Bypass or connect fuse links directly as shown in above figures.
Source:Manufacturer
Pro
ble
m
Technical Evaluation
of Manufacturing
facilities & processes
by a Competent Team
Proto Testing in 3rd
Party independent
laboratory.
Adopt Stringent FAT
Conduct Post Landing
Inspection
Way ForwardSolution
Faulty design
Quality of Raw
Materials
Poor
workmanship
Improper Mfg.
Process
Improper
transportation
Chances for
Under-rated
Transformers
Select Reliable
Manufacturer
Ensure, transformers
are manufactured as
per the Specifications.
Sources of Failures & Counter Measures
Mini Test Set-up (Upto 500kVA)(Tests: No Load & Load Loss, Impedance Voltage, Winding Resistance and Oil BDV)
(This is an example test setup for explanatory purposes only)
CONCLUSIONS
In Procurement Stage, all the Counter measures
should be taken in to Consideration
o Vendor Pre-Qualification Processes
o Product Qualification Processes
o Factory Acceptance Test
o Post Landing Inspection
o Training for field Engineers and Staff
Thank you !