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COMPLETELY SELF PROTECTED
DISTRIBUTION TRANSFORMER
BY :K. SUSHEEL KUMAR(06M21A0251)P. VINAY KUMAR (06M21A0257)G. MANIKANTA(06M21A0210)
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ABSTRACT
The high rate of failure of secondary distributiontransformer in power systems may perhaps bedescribed as 0ne of the tragedies of distribution
system management of present times especially indeveloping countries like India. The advent of CSPtechnology has encouraged progressivemanufactures to go in for high performance
distribution transforms which mitigate the operationand maintenance problems associated withconventional transformers. CSP technology enables
a transformer to protect itself from faults
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Aspects Covered In This
Presentation
what is CSP? & what is its purpose?
Why CSP transformer?
Reasons for failure of distribution transformer?
What is the philosophy of CSP?
Components of the CSP transformer
Major advantages of CSP transformer
Technical specification & IS specification of CSP
components.
Arriving at a conclusion
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What is CSP? & its purpose?
CSP is completely self protected transformer.
CSP is a protection system for distribution transformers.
Purpose of CSP:
It avoids major damages to the transformers by powersystem faults, by disconnecting the transformer (on eitherside) from faulty circuit.
The CSP protection system protects the transformer fromlightning, secondary faults, severe overloads and provides
visual warning of the existences of uneconomical loadingconditions
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Why CSP transformers?
Due to the higher failure rate of secondarytransformers in power system, especially indeveloping countries like India, kenya.
Short circuit faults. Excessive heat generation.
Excessive Current flow with out short circuit
faults due to change in resistance of the circuit. Protection against lightning .
Over loads on secondary.
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What is the failure rate of
distribution transformers?
In India 20%
In the west
1 to 2%
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Reasons for failure of distributiontransformers.
Changing weather conditions
Lengthy low voltage lines
Short circuit due to clashing of looselystring LV lines.
Lightning
Oil leakages Ingress of moisture etc.,
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What is the Remedy
Adopting CSPT is one of the options toreduce failure rate.
Proper maintenance
Proper design by considering atmosphericconditions
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What is the philosophy of CSP
Distribution transformer must be protected from over
loads
Electrical distribution system must be protected from
interruption in case of transformer failures
Distribution transformer should not be operated
regularly on over loads Lightning Arrestors are directly mounted on the
transformer tank to maximize surge protection
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Components of CSPT
Primary side : high voltage fuse
Secondary side : For over load secondary fault
protection
Surge arrester : for lightning protection
Signal light
Emergency control: magnetic trip Magnetic trip
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Primary ( high voltage fuse )
Power utilities in India provide a HV fuse on primaryside of a distribution transformer for systemprotection
Internally mounted
Rating determined such that it should not blow forsecondary faults and exciting current surges
Generally rated 12 times the full load current for 10msec
Connected in series with HV winding It protects the transformer from its internal faults
Protect the part of the electrical distribution system
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Secondary ( low voltage ) circuit
breaker
The low voltage circuit breaker is the centralcomponent of the CSP protectionpackage. Itprovides the entire over current protection to thetransformer.
Central component of the CSP protection package
Provides over current protection
Mounted internally
CB is of thermally operated type Responds to the secondary faults extermal to the
transformer by tripping open.
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Surge arrester
surge arrester is directly mounted to the
transformer tank.
The ground lead length is effectively zero and
maximum transformer protection is obtained.
lightning arresters are basically non linear
resistors i.e acts as resistors at operating at
voltages and as conductor at higher voltages.
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Constructional features:
Circuit breaker is an electromechanical device
and is of simple construction.
It has following major elements
Temperature sensing
Latching and tripping
Current interrupter
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Temperature sensing function:
Bi metallic strips, which are built into the breaker such thatload current flows through them.
Bi metallic strips responds thermally to the temperature oftransformer oil & temperature changes created by the flow ofload current through them
Latching and tripping function are carried out with anassembly of parts similar to those used in industrial type
If circuit breaker does trip in response to even a temporarysecondary fault, service can be restored easily by clearing thefault and re-closing the circuit breaker
Indication will be provided by the signal lamp for continuousoverload & trip
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Magnetic trip:
Certain circuit breakers are furnished with
magnetic trip which increases the opening
speed under high fault conditions.
There must be co ordination between primary
fuse element and secondary circuit breaker,
such that for any fault on the load side the
circuit breaker clears the circuit, fuse melts.
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Pressure relief device:
It operates at pre specified pressure.
Generally operates at 3.6 PSI, for corrugated
construction at 10 PSI for radiator construction
It releases the pressure at above value and
protect the tank from excess pressure.
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Technical specification:
Single phase : CRGO. Up to 167KV
AMT.. Up to167 KV
Three phase : CRGO. Up to 315 KV
AMT. Up to 315 KV
No of phases : single or three phase
Applicable standards: IS, IEC, ANSI, JIS, BS. Cooling : ONAN,OA
Insulating fluid : mineral oil to specification
Frequency : 50 or 60 HZ
Vector group : As specified Primary voltage : up to 11KV
Secondary voltage : 415, 433 volts or other
Winding material : copper or aluminum
Tappings : + or 5% or other
Impedence : as per appliclble standards
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What are the major advantages of
CSP technology
Enables a transformer to protect itself from faults
Transformer is protected from persistent overloads
not cleared by conventional protective gear.
Uneconomical over loading on a regular basis isavoided
Protection from lightning is most effective
No scope of ingress of moisture Failure due to undue pressure rise will not be there.
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Benefits
Low installation cost
Simple easy installation
Safe operation Reliable service
Low cost of operation
Clean appearance
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Is specifications of CSP components
Distribution T/F : 1180
Metal oxide surge arrester ; IEC- ANSIEEEE-C-11/1982
Circuit breaker : 13118
HV fuse link : 9385
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conclusion:
Thus CSP technology has paved the way tohigh performance distribution transformers and
better distribution management.
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