| Features |
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| Retrofitting Medium Voltage
Old MOCB Switchgear with VCB |
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| UPGRADING TECHNOLOGY |
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| For medium voltage range (upto 36kV),
utilities in india have been using Minimum
Oil Circuit Breakers(MOCBs) at power
generating and distribution centres
for more than 30 years. |
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| MOCBs, using oil as an arc quenching
and insulating medium, have following
limitation. |
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Frequency and level
of maintenance are high. |
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Limited operational and short-circuit
operational life. |
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Vulnerable to fire hazards associated
with oil. |
|
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| Advantage of new technology. viz.
Vacuum, with its superior dielectric
and arc interruption properties, has
not only eliminated all the limitation
of MOCBs, but also made the circuit
breaker more compact and highly reliable.
Utilities, therefore are adopting vacuum
technology for their new installations,
indoor as well as outdoor upto 36kV. |
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| Hence , to ensure reliable , uninterrupted
power supply and reap the benefits of
vacuum technology. It is imperative
to upgrade the technology of existing
installations with MOCBs, so that they
transmit and distribute power efficiently
with minimum outage and interruptions.
'Retrofitting' old MOCB switchgear with
VCB is the cost effective alternative,
which make will improve the life and
reliability of switchgear without going
for large investment. |
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| PIONEERING EFFORTS |
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| Jyoti has been in the forefront of
Medium Voltage switchgear since early
sixties, having technical collaboration
with erstwhile Calor-Emag of West Germany.
Jyoti has supplied more than 20,000
MOCBs to thermal power stations, petrochemical
complexes, refineries and transmission
& distribution sub-stations of various
state electricity boards in India. Keeping
pace with technological changes, Jyoti
entered into technical collaboration
with Toshiba Corporation, Japan in mid
eighties for manufacturing a wide range
of Vacuum Circuit Breakers. Jyoti has
manufactured more than 12,000 nos. of
VCBs till date and they are working
satisfactorily. |
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| MOCBs VIS-A-VIS VCBs - ADVANTAGES |
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| Jyoti has undertaken 'Retrofitting'
of MOCBs with VCBs aggressively as if
offers following advantages: |
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|
Cheaper and simpler
alternative for the old installation,
where service-life is almost over. |
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Benefit of vacuum technology
made available with minimum installation
cost. |
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Frequency of maintenance drastically
reduced. |
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No need to store large quantity
of costly spare of MOCB which
may not be available because its
manufacturing has been tapered
off. |
|
Installation can be provided
with increased load current and
fault level as VCB is quite compact
compared to MOCB of similar fault
level. However, corresponding
specializations of CT as well
as support system requirement
should be taken in to consideration. |
|
In case of expansion with VCB
technology, 'Retrofitting' of
old MOCB panel will eliminate
the need of simultaneous maintenance
of two different equipment. |
|
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| The concept of 'Retrofitting' developed
at Jyoti does not call for replacing
the entire switchgear. This eliminates
large investment because it does not
require : |
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Modification in
foundation. |
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Change in the power cable route. |
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Change in the control cable
route. |
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Shutdown, which would result
in loss of power generation and
consequently loss in production. |
|
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|
Jyoti undertakes
'Retrofitting' i.e. changing
the MOCBs of any make and type
by VCBs either |
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|
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| - by offering one-to-one replacement |
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|
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| (Rear
and front view of 'Jyoti' One-to-One
VCB)
|
|
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| In this arrangement, the MOCB is replaced
by VCB on the same truck, retaining
the same interlocks. It is just removing
the MOCB truck and replacing it with
VCB truck. Panel does not require any
modification, nor does the foundation
or cable route calls for any change.
And of course, NO Shutdown. The MOCB
truck can be retained as a spare for
emergency. The operators, who are familiar
with the working of MOCB, can easily
deal with new VCB without undergoing
ant training. |
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| OR |
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| - by offering cassette type
draw-out units |
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In
this arrangement, VCB truck is
offered with complete safety interlocks,
shutter, contact shrouds etc.
as per new design. The breaker
compartment is totally segregated
from busbar and cable compartment.
The unit is quite sturdy and able
to withstand all kinds of forces
that develop during short circuit
test.
This arrangement is preferred
when interlocks are required to
be changed or when segregation
of VCB compartment is necessary.
This arrangement, however, requires
related changes in panel and may
call for shutdown for a short
period.
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| FIELD EXPERIENCE |
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| Jyoti Ltd. has successfully carried
out 'Retrofitting' of nearly 1000 MOCBs
with VCBs in last decade at number of
installations. The performance of switchgear
at these sites has been quite satisfactory.
The response from customer is highly
encouraging. The utilities with existing
MOCB installations are increasingly
going for 'Retrofitting' for upgrading
their equipment, since the cost of 'Retrofitting'
is less than 50% of the cost of new
VCB panel installation. Together with
improving the performance, reliability
and also the fault level in many cases,
'Retrofitting' offers the most cost-effective
solution. |
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| Ring Main Unit |
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| INTRODUCTION |
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| Jyoti Ltd. has been in the forefront
of switchgear technology for over four
decades. It has a well established R&D
Center and full-fledged manufacturing
facilities which provide a wide range
of quality products and services conforming
to Indian and International standards,
Jyoti now introduces yet another state-of-the-art-product
– RING MAIN UNIT (RMU) |
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| RMU is an answer to the need arising
out of space limitation for compact
switchgear. It ensures continuous power
supply. Ring bus configuration provides
greater flexibility in distribution.
Supply can be restored from any adjacent
section. Faulty section can be easily
isolated, leaving the healthy sections
continue to operate. This allows maintenance
to be carried out in faulty section
without disturbing other sections. |
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| UNIQUE FEATURES OF ‘JYOTI'
RING MAIN UNIT |
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Suitable for both
Indoor and Outdoor applications. |
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Three position, load-break,
fault-make switch immersed in
oil is easily accessible for maintenance. |
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Drive mechanism of load-break,
fault-make switch located outside
oil tank, any problem in mechanism
can be attended, without opening
the oil tank. |
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Transformer feeder is provided
with Vacuum Circuit Breaker (VCB)
instead of fuse-switch combination. |
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Integral earth switch with suitable
interlock is also provided. |
|
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| Advantages of using VCB |
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Less maintenance. |
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Greater safety of personnel,
as changing of fuse in liquid
insulating medium in conventional
system is prone to accidents. |
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Recurring cost of replacing
the fuse eliminated. |
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In case of fault, breaker trips
and power supply is restored by
just pressing a button. This reduces
downtime and reduces the customer
minutes loss. |
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Very high mechanical and electrical
life as compared to fuse-switch. |
|
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| APPLICATION |
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| ‘JRM’ series Ring Main
Units are designed for medium voltage
ring network such as: |
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Public and industrial
distribution network up to 12
kV |
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Protection of transformers 25
to 2000 kVA and higher ratings. |
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Power distribution for both
indoor and outdoor installations
from transformer sub-stations. |
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