Experience in the operation and adjustment of electrohydraulic governors of hydraulic turbines

Abstract

In the USSR electrohydraulic governors of turbines began to be used instead of hydromechanical governors at the end of the 1950s. At present six modifications of electrohydraulic governors (EHG-s) differing not only in basic design but also in the block diagram are presently operating at Soviet and foreign hydroelectric stations along with hydromechanical governors. Despite these differences, a large part of the functional components of all EHG modifications are of the same type. The characteristics of the operation of two of them --the floating control component and automation scheme --are examined below for the example of governors of type ]~GRK-2M and I~GRK-1T.One of the differences of the floating control device in an EHG from the dashpot in hydromechanical governors is the absence in it of limitation of the action of the RC output signal. This leads to the need to supplement the EHG scheme with automatic devices intended for eliminating the consequences of this characteristic. However, the uncoordinated or untimely action of these automatic devices in a number of cases control leads to the incorrection action of the system.According to the specifications of the State Standard (GOST) 12405-81 governors should provide "stable automatic control of the unit during operation under no load, under an isolated load, and in the power system, during load drops and surges," i.e., the correct action both in steady and transient operating regimes of the unit. In modern power systems the units operate, as a rule, in a no-load, idling regime during synchronization and in a power regulating regime (with frequency offset behavior), usually in a group active power control (GAPC) system. At the same time, a large number of units, along with these regimes, can operate also in a frequency control regime in a region isolated from large power systems.To adapt the control system in these operating regimes of the unit, special measures are provided for in the EHG which are realized automatically during the transient. Thus, for example, during drops of the load automatic switching occurs by disconnection of the generator switch from the load floating control component to the idling floating control component, the set values of which were chosen beforehand from the condition of providing stability of the control system during idling operation of the unit and providing a minimum time of synchronization. Upon disconnection of the generator switch conversion of the mechanism changing the opening (MCO or MCP) to a position at which the signal from it is compensated by the signal of the sensor of the opening of the gate apparatus (to the "idling" position) is also accomplished automatically.As a rule, the set values of the idling floating control component (B t and Td) are small, and therefore the slowing action of the floating control component is small, and if the mechanism changing the frequency (MCF) is not in the extreme position "to increase" and conversion of the MCP acts, control is realized despite the absence of limitation of the...