Jyoti Limited

Switch Gears

   Features

Retrofitting Medium Voltage Old
       MOCB Switchgear with VCB

UPGRADING TECHNOLOGY
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.

MOCBs, using oil as an arc quenching and insulating medium, have following limitation.

  • Frequency and level of maintenance are high.

  • Limited operational and short-circuit operational life.

  • Vulnerable to fire hazards associated with oil.

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.

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.

PIONEERING EFFORTS
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.

MOCBs VIS-A-VIS VCBs - ADVANTAGES
Jyoti has undertaken 'Retrofitting' of MOCBs with VCBs aggressively as if offers following advantages:

  • Cheaper and simpler alternative for the old installation, where service-life is almost over.

  • Benefit of vacuum technology made available with minimum installation cost.

  • Frequency of maintenance drastically reduced.

  • 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.

The concept of 'Retrofitting' developed at Jyoti does not call for replacing the entire switchgear. This eliminates large investment because it does not require:

  • Modification in foundation.

  • Change in the power cable route.

  • Change in the control cable route.

  • Shutdown, which would result in loss of power generation and consequently loss in production.

 

Jyoti undertakes 'Retrofitting' i.e. changing the MOCBs of any make and type by VCBs either 


('Jyoti' MOCB Truck)

-by offering one-to-one replacement


(Rear and front view of 'Jyoti' One-to-One VCB)

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.

                            OR
-by offering cassette type draw-out units

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.

FIELD EXPERIENCE
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

INTRODUCTION

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)

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.

UNIQUE FEATURES OF ‘JYOTI' RING
MAIN UNIT

  • Suitable for both Indoor and Outdoor applications.

  • Three position, load-break, fault-make switch immersed in oil is easily accessible for maintenance.

  • Drive mechanism of load-break, fault-make switch located outside oil tank, any problem in mechanism can be attended, without opening the oil tank.

  • Transformer feeder is provided with Vacuum Circuit Breaker (VCB) instead of fuse-switch combination.

  • Integral earth switch with suitable interlock is also provided.

      Advantages of using VCB

  • Less maintenance.

  • Greater safety of personnel, as changing of fuse in liquid insulating medium in conventional system is prone to accidents.

  • Recurring cost of replacing the fuse eliminated.

  • 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.

  • Very high mechanical and electrical life as compared to fuse-switch.

APPLICATION

‘JRM’ series Ring Main Units are designed for medium voltage ring network such as:

  • Public and industrial distribution network up to 12 kV

  • Protection of transformers 25 to 2000 kVA and higher ratings.

  • Power distribution for both indoor and outdoor installations from transformer sub-stations.

       

Copyright © 2004 Jyoti Ltd.