Improving the Efficiency of Auxiliary Cooling Water Pump and Auxiliary Sea Water Booster Pump in Thermal Plant using Variable Frequency Drive

Abstract

I. INTRODUCTIONWe Examined the North Chennai Thermal Power Station (NCTPS) Stage-I and we observed that, the cooling water systems are usually designed with full capacity flow rate to cope with the all possible situation where the machinery is running at full load. Because of this the majority of cooling systems are oversized in relation to the actual requirements. If one can measure the actual requirement and regulate the pump's pressure or flow so that it matches the current requirement, the pump will use less energy and this therefore, does not need to be produced on board, with less fuel being consumed as a result. About a third of the world's electrical energy is consumed by electric motors in fixed-speed centrifugal pump, fan and compressor applications. The processes, in the form of liquid or gas flow, are typically driven by large electric motors with the power demand following affinity laws. Pumps are devices that deliver a pressure increase to liquid and it's a largest consumer of energy in the industrial sector. The pump provides the energy necessary to drive the fluid (water) through the system and overcome friction and any elevation difference. Driving the pumps with fixed speed motors and controlling them at partial loads either by throttling or mechanically by fluid coupling decreases the power plant's efficiency tremendously. When large flows must be controlled and motor energy consumption is significant, varying the motor's speed is the answer. In order to reduce maintenance costs and further improve the plant 's efficiency, the pump drive systems were upgraded with a variable speed converter (VFC) system or called a variable frequency drive (VFD). Controlling pumps by adjusting speed avoid wasting energy. Variable speed drives in a pump system are now a mature technology, which can generate large benefits to the user in cost savings and reliability improvements, in the right applications. Pump's drive means a sequence of energy conversions from electrical input power to mechanical output power and then to hydraulic power (figure 1). Each conversion is described by his specific equations and reference frames. [1,2,3,4,5,6] The theory of operation of pumps can be characterized by the affinity laws: