Transcript Increasing the Life Cycle of Existing Grids to Avoid High

Increasing the life cycle of
existing grids to avoid high
replacement costs of new systems
By
S.R.Sethi
Member
Delhi Electricity Regulatory Commission
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Power system is a seamless system from generator to consumer.
Transmission system and sub-transmission is the integral part
of the system.
Cost of transmission system is almost 50% of that of generating
system.
Though as per depreciation norms, generating system and
transmission system have the same life but in actual practice,
transmission
system
is
not
replaced
but
only
augmented/components replaced with the latest technology
such as circuit breakers, CT,CVT, & PTs.
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The equipment which is required to be
upgraded for increasing the life cycle of the
transmission system are as follows:
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Earthing system to be re-inforced depending upon the
erosion effect and to take into account the increased fault
level in the system.
Circuit breakers which were conventionally oil circuit
breakers were replaced with Minimum oil, Air blast and
now replacement with SF6 breakers which are maintenance
free.
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CT, CVT and PTs are to be replaced
depending upon various requirements
of the fault level, Metering and aging of
the equipment.
Aging of the equipments where paper
insulation is immersed in oil are viz. (a)
Power
transformer,
(b)
Current
transformer, (c) CVT and PTs.
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Checking of the Tan delta value of such
equipment yield the health of the
equipment.
Infra red scanning of the switch yard on
monthly basis helps to detect in
incipient fault in such equipments apart
from hot spot on connectors of the
switch yard.
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Thermo graph of Transformer during heat run test
compared with field measurement is quite indicative of
incipient faults.
Life of transformers can be enhanced by carrying out the
nitrogen cycling for removal of water and restoring the
health of paper and wood insulation periodically at an
interval of say ten years or as per diagnostic tests.
Replacement of insulating oil (need based) would also
enhance the life of the transformers.
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Control cables are one of the major source of
problems after the insulation becomes brittle
and replacement of cables is not an easy job in
an existing sub-station.
Replacement
of
Electro
mechanism
relays/static relays with numerical relays
conforming to IC 61850 along with automation
of the sub-station based upon bay control unit
system
would
reduce
control
cables
requirement.
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Bay control units are installed in each of the
bay where the relays are also provided in the
outdoor kiosk, Co axial or Optical fiber cable
is brought to the control room for operations
of the sub-station equipment.
Even remote operation of the sub-station
from master stations could be achieved.
These are not only cost effective but are
necessary for upgrading the life of the
existing sub stations.
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Painting of structures and proper upkeep
of the civil works can increase the life of
the sub-station.
Increasing Power carrying capacity of
Transmission and Sub transmission lines
with the aluminum alloy conductors, it is
possible to use the same Towers with
higher
current
carrying
capacity
conductors for optimum utilization.
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Right of way for new lines within the urban areas are
extremely difficult and most of the Transmission
projects get delayed due to right of way problems.
Right of way problems in cross country poses
problems of environmental clearance and the wrath of
the land owners for laying up the new towers which
nevertheless reduces the value of the land.
Incidentally, Electricity Act does not provide any
compensation for the right of way of the transmission
lines.
Since cities in India were not planned in the
manner they have developed over a period
of time, space for sub stations is becoming
non-existent and wherever available is at
prohibitive costs.
Thus increasing the life of
existing substations and upgrading equipment
with the latest technology is the only solution in
such Metro cities and towns.
Cost of
refurbishment could be a fraction of cost of new
sub-station and is thus an optimal solution.
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Indoor substations and underground substations
is the future of Transmission and Distribution
Sub-stations.
As per the provisions of Electricity Rules
installation of Oil Type Transformers below first
basement is not permitted. Solutions need to be
found out for installation of Oil Type
Transformers. One solution could be to put the
GIS Sub Station underground while the
Transformers could be installed on the ground
level to take care of the requirements of the IE
rules for safety.
Thank You