A Simulation-Based Procedure to Determine Optimum Range of Settings of Fast Valving Action of Steam Turbines to Enhance Frequency Stability

K J Lakmewan,D G Rienzie Fernando,D Prasad Wadduwage

doi:10.4038/engineer.v53i2.7409

K J Lakmewan, D G Rienzie Fernando + Show 1 more

Open Access

https://doi.org/10.4038/engineer.v53i2.7409

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Abstract

Fast Valving (FV) mechanism of steam turbines is considered to be one of the most effective actions for enhancing the security of a power system subsequent to disturbances. It plays a significant role in mitigating the impact of severe disturbances by instantly decreasing steam turbine power, thus ensuring the power system stability. There is a direct relationship between the settings of Over-Speed Protection Control (OPC) unit of steam turbines and the control functions of FV. This paper proposes a generalized simulation-based procedure to determine the optimum intermediate valve actuation timings of the FV control action. A coal-fired thermal power plant has been used as the case study and the accuracy of the settings made using the proposed approach has been demonstrated using actually happened contingencies in a real power system. Finally, it is concluded that the proper selection of actuation timings of intermediate valves for FV scheme has a significant effect on enhancing frequency stability under transient conditions.

Highlights

Today’s world is highly dependent on electricity due to growth of needs and increased number of electrical appliances
From the results of this study and manufacturer recommendations for TA, the values given in Table 4 and 5 are recommended for the fast valving settings of the coal fired thermal generator unit considered in this study
This paper presented a generalized procedure to determine optimum settings for Fast Valving (FV) action of a coal-fired thermal power plant

Summary

Introduction

Today’s world is highly dependent on electricity due to growth of needs and increased number of electrical appliances. Transient stability is the ability of a power system to maintain synchronous operation subsequent to large-magnitude disturbances such as tripping of elements due to three-phase faults [1]. Fast Valving (FV) action of a steam turbine is an accepted practice to enhance the transient stability of a power system [2]. Rapid closing and opening of steam valves is activated in a prescribed manner to reduce the turbine acceleration following a severe fault in a power system. The Intercept Valves (IV) of the steam turbines are fast closed, resulting in rapid reduction of mechanical power. This action must be initiated within a minimum time after the detection of a disturbance in the power system, followed by its reopening.

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