Vol. 27 No. 4 CENTRE OF EXCELLENCE FOR SIMULATORS ESTABLISHED BHEL has recently established a state-of-the-art Centre of Excellence for Simulators at its Corporate Research and Development Division, at a cost of Rs. 37.8 million. The Centre of Excellence not only highlights the extant Power Plant Simulation capabilities of BHEL, but would also play a vital role in large-scale commercialization activity in this advanced area. The Centre has the facility for carrying out Dynamic Simulation Studies for Combined-Cycle Cogen Plants and Thermal Power Plants. In the recent past, many simulation studies were executed commercially for various combinedcycle cogen plants. December 2004 The Centre of Excellence features state-of-the-art Pentium workstations, Itanium servers and a large Video Display wall, to facilitate hands-on training for up to five operators at a time, supplemented by an attached lecture hall with a networked projection facility for observing the plant operation. The Virtual Power Plant model of the Centre is a promising and ideal platform for testing and evaluating the PADO (Performance Analysis Diagnostics and Optimisation) software which is emerging as a regular requirement for all the power plants of NTPC. The Virtual Power Plant model also facilitates testing of new and advanced control schemes, like Automatic Plant Startup, adaptive and fuzzy controls. The Centre implements a typical 500 MW Thermal Power Plant simulator, which is a total in-house development based on the first-principles approach, and supports a wide range of malfunctions covering the entire plant operations. In addition to the Operator Training Simulator facility, the Centre is also equipped with Controller Testing Simulator setup, for evaluating and tuning the controllers based on ProControl and maxDNA C&I platforms. Besides meeting the training requirements of power plant operation staff, the Centre also provides an ideal platform for providing the required exposure on plant operations, to the engineer trainees and commissioning staff of BHEL. The Centre of Excellence for Simulators The above facility has already been put to use in testing one such proposed advanced control scheme, viz., Free Governor Mode Operation, aimed at maintaining grid frequency at 50 Hz for obtaining better quality of power. The concerned Steering Committee comprising CEA, NTPC, BHEL & PGCIL members, suggested that the proposed scheme be checked on a simulator before implementation. Accordingly, the effects of different governor control schemes on plant parameters for different frequency patterns were studied and the scheme was finalized, using the simulator at the Centre of Excellence. Thereafter, the scheme was implemented at NTPC's Simhadri Power Plant. BHELSCAN — A DIGITAL FLAME SCANNER BHEL has developed a digital flame scanner, BHEL SCAN, for better and more reliable flame detection. In BHELSCAN, advanced technology for flame signal processing and discrimination/identification of different flames, has been introduced, by redesigning the conventional flame scanner with a totally fresh approach taking advantages of the microcontroller technology. To overcome the usage of independent flame scanners for different fuels like coal and oil, a new integrated type flame scanner, which can detect the flames of various fuels as a single scanner, has been developed. The system can be easily retrofitted with existing flame scanner head assembly. The flame scanner consists of scanner head electronics and a control unit. The head assembly of the scanner consists of a quartz lens for collection of light signal and a fibre optic cable for transmission of the light signal to the head electronics. In the head electronics, a photo diode is used to convert the light signal to electrical signal. The electrical output of photo diode is amplified by a log amplifier. The amplified signal is then compensated for background radiation of the furnace. The flame intensity component and flicker component of the signal is separated and processed for characteristic frequencies of coal and oil flames by a microcontroller-based signal processing card. The software ensures discrimination of different flames through proper detection of characteristic flicker frequency range of the flame. Salient Features • Digital Processing ensures reliability of flame detection • Improved accuracy and better response • Digital display for various parameters • 2 ½ digit LED display with display mode selection by push button • Protection EMI/RFI filter for power input • Provided with serial communication interface for communication with DCS • Fault indication is provided for short circuit & dark furnace. BHELSCAN system configuration B H E L V I S I O N 2 0 M — M I C R O C O N T R O L L E R-B A S E D E L E C T R O N I C WAT E R L E V E L INDICATOR FOR BOILERS Extensive research in level indication has culminated in the introduction of electronic water level indicating system based on conductivity principle. BHELVISION 20M, developed by BHEL, works on the above principle (difference in electrical conductivity of steam and water). The proven technology of BHELVISION 20M has been applied for the critical application of drum water level monitoring in utility and industrial boilers. application. For large-scale demonstration of this product, 24 solar geysers have been engineered, and installed at the Executive Hostel Block of ASCI, Hyderabad, for supplying hot water to the 93 hostel rooms. One solar geyser of 100 lpd capacity has been installed on the terrace connecting the four bathrooms vertically located in the four-storeyed building. The systems have been under continuous operation since January 2004, supplying hot water to the hostel rooms. ASCI has expressed satisfaction with the performance of the solar geysers. High water level leads to harmful water carryover to turbine blades. On the other hand, low water level leads to starvation in tubes leading to tube failures. BHELVISION 20M system enables proper monitoring of water level in boiler drum. Salient Features • Advanced microcontroller-based technology • International certification by CSA • 4-20mA analog output for level indication • Electrode fault identification by flashing LED • Group fault indication including indication for abnormal conditions : water above steam/ steam below water. • On-line simulation facility • Detection of electrode and cable open or short condition • Fault in one channel not affecting other channels • Component level serviceability. DISTRIBUTED HOT WATER SYSTEM THROUGH 100 LPD SOLAR GEYSERS ENGINEERED AND INSTALLED BHEL has developed and tested extensively solar geysers of 100 lpd (litres per day) capacity using thermo-syphon heat pipe principle, for domestic Distributed hot water system installed at ASCI, Hyderabad Normally, utilities of the above type are provided with centralised large water heating systems with long insulated hot water delivery lines. In comparison, the individual solar geysers installed at ASCI have eliminated lengthy water delivery lines, reducing the heat losses and thereby enhancing the performance of the system. BHEL FURTHER IMPROVES ITS a-Si DOUBLE-JUNCTION SOLAR CELL MODULES A process for large-area (2700 cm2), doublejunction amorphous silicon (a-Si) solar cell modules was developed at Amorphous Silicon Solar Cell Plant of BHEL, during 2001-2003. The power output of these modules ranged from 14-17.5 W corresponding to a maximum total area efficiency of 6.5%. Since then, various improvements have been effected in these large-area solar cell modules. These improvements have contributed to an increase of ~18% in the cell current which, in turn, has resulted in raising the module output to 18-19W from 14-17.5 W. In addition, the cost of raw material has reduced as the normal float glass used earlier as substrate has been replaced by sheet glass which is ~ 40% less expensive. BHELMHO — A STATE-OF-THE-ART E L E C T R O N I C WAT E R L E V E L SWITCH BHEL has developed water level switch, BHELMHO, based on the measurement of differing electrical conductivity of water and no-water space, without necessitating any density correction. This results in accurate and reliable level detection, rendering the BHELMHO a superior alternative to the conventional mechanical float-type level switches. BHELMHO level switch has four electrodes which sense the water level and provide indication through the system's own dedicated circuitry and output relays. A safe low excitation voltage is applied between the insulated tip and the body of the sensing electrodes. The sensor output is dependant on the conductance of the cell formed by the electrode and the body. It is compared with a reference value and the electronic circuitry discriminates between nowater and water. In addition, the electronics is capable of detecting the open and short fault conditions of the sensing system. Salient Features • Replacement for float-type switch, with no moving parts • High reliability • Wide choice of power inputs : 110V AC, 230V AC or 24V DC • Dual power supplies for enhanced availability • Square-type large LED display • Self-diagnostics and fault indications • Compact enclosure of IP55/IP65 protection class • Sensor (electrode) manufactured by BHEL, thus ensuring prompt after-sales service. Areas of Application in Power and Process Plants • De-aerator storage level • HP & LP heater columns • Main boiler drum level • Blowdown tank level • Main steam header drains • Hot and cold reheat drains • Turbine extraction drain • Hot well alarms • Generator coolant level • Turbine casing drain. Typical BHELMHO water level switch installation in HP heater Issued quarterly by the Corporate Office, Bharat Heavy Electricals Limited, BHEL House, Siri Fort, New Delhi-110049, Website : http://www.bhel.com Editor : P. Jagannathan. Associate Editor : D. Roy. Designed & Printed at NIKHIL OFFSET, New Delhi-110020. Phones : 26812316, 26810097, Telefax : 26810458 For Private Circulation only