BHARAT HEAVY ELECTRICALS LIMITED

Frequently Asked Questions

Hydro Turbines
Electrical machines
Medium Voltage Switchgear

Q. What are the types of turbines manufactured ?

BHEL manufactures Pelton, Francis, Kaplan, Reversible,Bulb, S-type and Mini-Micro turbines.

Q. What is your turbine orientation ?

Usually conventional turbines of 5MW and above unit ratings are of vertical orientation. Mini-micro turbines,
Tubular & Bulb turbines are of horizontal orientation.

Q. Do you under-take EPC/turnkey contracts (Engineering Procurement Constructia) including Civil works.

Yes we undertake EPC/turnkey contracts.

Q. Do you supply spares for non BHEL sets ?

Yes.

Q. What is your state of technology level ?

BHEL turbines are of world class level.

Q. Does BHEL undertake R&M activities ?

BHEL has a rich experience of BHEL & non BHEL sets.

Q. What other activities related to hydro turbines are carried out ?

We design, manufacture and supply all associated turbine auxiliaries such as governor, cooling mater
system etc.

Electrical machines

Q. What are the short circuit level of various terminal boxes provided by BHEL?

   For PSTB 44 KA/0.25 sec.
   For Flame Proof TB 26.2 KA / 0.25 sec.

Q. What is the service life of antifriction bearings?

The L10 life of bearings is generally 40000 hrs.

Q. What is the service life of sleeve bearings?

The service life of sleeve bearings is infinite subject to proper maintenance.

Q. What is `MICALASTIC` insulation?

   It is proprietary system developed by Siemens AG, Germany. It includes both resin rich and resin poor
   system followed by VPI. For medium range machines (upto 1500 KW / 4p) , the resin rich system is
   the most optimum insulation system.

Q. Difference between resin rich & resin poor insulation system?

   In resin rich insulation system, the resin Content of the basic insulation is higher and self Containing,
   while in resin poor system the resin content is lower and it is supplemented by subsequent impregnation
   under vacuum and pressure.

Q. What is Mixed Frequency testing?

The mixed frequency testing is basically used for determining the temperature rise a machine for which
direct loading is not possible due to orientation or test plant limitations.

   In this method, the electrical power at two different frequencies is fed to the motor. Mixing of two frequencies
   is motor results into a flow of rated current to the machine winding. The current is adjusted by adjusting the
   voltage and frequency of auxiliary source. The test is covered in IEC-37 / IEEE-12 / Draft IEC.

Q. Whether any certification is needed for Type N (Ex `n`) motor?

As per IS:9628 , Certificate from statutory agency is not necessary. Only self Certification by manufactures
is sufficient.

Q. What Can be the largest rating of a flame proof motor?

   The largest flame proof motor can be manufactured upto 1500 kw , 4P. Above this rating pressurized (Ex`p`)
   motor is the best option is zone 1 Hazardous areas. The Ex`p` motor can be supplied for one entire range
   of machines.

Medium Voltage Switchgear

Q. Does BHEL, Bhopal makes Vacuum, oil and SF₆ breakers ?

BHEL, Bhopal is in the field of Switchgear Manufacturing since 1960. Presently BHEL, Bhopal makes
Medium Voltage Switchgears of Vacuum type.

   BHEL, Bhopal stopped manufacturing oil switchgears since 1995. SF₆Switchgears are not manufactured
   by BHEL, Bhopal for medium voltage application however BHEL, Hyderabad, INDIA manufactures SF₆
   circuit breakers in the range of 72.5 KV to 400 KV.

Q. Does BHEL Bhopal offers switchgear with Integrated digital devices / numerical relays for Protection metering and control ?

Yes. BHEL offers switchgears with conventional relays (Electromagnetic and static) as well as with
communicable numerical relays as specified by user.

Q. How a loss of Vacuum can be verified in Vacuum switchgear ? What are its consequences ?

   Circuit breakers having vacuum Interrupters have been in service for over 30 years and have proved to be
   extremely rugged and reliable device however like any man-made device they can also fail. In the field,
   the best way to verify vacuum is to carryout high voltage P.F. withstand test. Manual checking by
   disconnecting moving contact of Vacuum Interrupter from Mechanism and manually pulling on moving contact
   which requires a force proportional to area of contact is a rough guide but not final confirmation of full vacuum.

   Behavior of vacuum circuit breaker in case of failure of Vacuum Interrupter is similar to any other breaker having
   arc quenching media as oil or SF₆. The advantage incase of vacuum interrupter failure is that it does not have
   violent bomb like blast which is more likely in SF₆ and oil media.

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