News & Events

Energy Saving Scheme at Mahagenco Power Plant

Mr. Praveen Khisti of Anand Technomarketing Pvt Ltd has implemented two projects. These are as follows:

1. Cooling Tower Variable Frequency Drive (VFD) Application in MSPGCL Khaperkheda (210MW)

Power Circuit of VFD Panel

Energy Saving Scheme for Cooling Tower Fans

Heat rejected in condenser for conversion of exhaust steam to water by removing its latent heat is carried away by the cooling water to the cooling tower where the heat removed from cooling water is rejected to atmosphere.

Heat to be rejected by cooling tower depends on unit load and the proportional steam flow. Also the cooling effect of cooling tower depends on (Dry bulb & wet bulb) temperature of surrounding atmosphere. As both the unit load and atmospheric temperatures vary, the need arises to vary the speed of cooling tower fans depending on process requirement.

In Khaperkheda Thermal Power Station, the scheme is delivering very good results under guidance of Hon. Chief Engineer. Before implementation of the scheme operator used to manually operate fans. The CT fans MCC was one Kilometer away from the operator cabin and it was practically impossible to continuously regulate requirement of CT Fans depending on unit load or the atmospheric temperature.

As per this scheme a VFD is installed on one 90 KW motor of cooling tower fan. As per process requirement, the speed of this fan varies from 400 RPM (min) to 1480 RPS (max). One more chartless recorder with 4 output relays is installed on this VFD panel for switching of four more CT fans depending on speed of VFD.

When the VFD speed rises as per process requirement and reaches up to maximum value, one of the four CT Fans is switched on. As it is obvious that when speed of VFD is increasing more cooling is required as per process conditions (e. g. increase in unit load & steam flow). When VFD speed reaches to its maximum value four (4) other CT Fans as sequentially made on as per demand with appropriate time delays between switching.

Similarly when unit load is reducing or atmospheric temperature drops down during night time the VFD speed reduces. When VFD speed reaches to its minimum value, CT fans are switched off one by one as per demand with appropriate time delay. Total saving due to switching off of CT fans and VFD from 13.09.2013 to 28.09.2013 is 68,435 kWhr.

2. Wobbler Scheme at Khaperkheda Thermal Power Station

Wobbler is a sort of vibro feeder which feeds coal to the coal crusher. The wobbler consists of a roller which gives vibratory motion to the coal so that larger and small chunks of coal are guided into the coal feeder. The major problems faced by the Engineers of Mahagenco – Khaperkheda unit was the high starting kick of the wobbler motor when the coal was loaded on to it which was sometimes hazardous to human life as the high kick would result into fire in the control panels.

Hence the system needed a soft start which required a high torque. The problem was identified and a Danfoss VFD of 45kw rating was installed on the wobbler motor of 30 kw rating. It was observed that the soft pickup of the wobbler motor allowed the coal debris to fall on the crusher slowly hence avoiding choke ups of the coal feeder. Also the current drawn by the motor got reduced with torque enhancement of the motor.

The panel was provided with selectable Direct On Line (DOL) as well VFD operations. DOL is to be used when VFD is under maintenance/breakdown. The control circuit of VFD was designed such that it could be operated from Control Room as well as from buttons on the panel, the selector switches were provided for the purpose on the panel.

This installation is working very satisfactorily and has reduced the hazard and risk to human life and costly equipment.