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O PERATORS OF power generating equipment realize that it is desirable from a system control point of view to have all speed governors on their interconnected systems with reasonably similar steady-state characteristics. Normal load changes then would be shared by all units in proportion to their ratings and the action of supple mentary controllers would be uniform. This would result in smaller deviation of frequency and load distribu tion from the desired values. Most attempts to make all prime movers on a system respond to system changes in proportion to their ratings have been confined to setting all speed governors so that they have equal steady-state speed regulation. Tests show that the response of prime movers to changes in system frequency or to the action of supplementary controllers is of a random nature and has little relation to machine rating or steady-state speed regulation. This article outlines the factors that contribute to the random nature of prime mover response and indicate how testing programs for existing units, as well as future design changes of governing systems, can produce a major improvement. Variations in the response of prime movers to changes in system frequency or to the action of supplementary con trollers are caused by diff'erences in the dead band and in the steady-state incremental speed regulation of the speed ui 3 10 ω 2 AVER OUTP \GE 0 iTFOf LASI VALV lOXi ί 44 OWER / / 1 L / /

merit of bushing, 4, can be read accuratel} 7 on a vernier dial, 3 (a.), at the test station. In order to prevent tripping of the unit, while testing, a look-out switch, 8, is used to open the trip circuit and to close the test-light circuit. This switch is operated by the locking lever, 5, which must be pulled to release the testing mechanism. The switch, 8, will reset automatically when the testing mechanism is returned to neutral position. The testing mechanism is also used to measure the thrust-plate wear by comparison of test records. Initially, the testing mechanism serves to set the device in correct position. APPENDIX 4 Oil-Jet Relay Pressure Regulator Principle. The heart of the oil-jet rela}' regulator is, as its name implies, an oil jet. This oil jet originates in an ejecting nozzle from which it proceeds across the free air to the receiving nozzle which is of the same diameter as the ejecting nozzle. Ap-proximate^' in the middle, the free oil jet is influenced by a jet deflector in form of a knife edge, suspended on the pressure-sensitive element of the regulator. Fig. 14 illustrates the operation of the oil jet.

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Three variables must be controlled on a double-automatic extraction turbine—speed (or power output), and the two process-header pressures—by controlling the flow of steam at different pressure levels. This has been done in a satisfactory manner on a large number of extraction turbines. However, the designs which had been developed for turbines of 50,000-kw capacity and smaller were not suitable for a turbine nearly five times as large, and a completely new control-system design had to be created.