US2175874A

US2175874A - Turbine protective arrangement

Info

Publication number: US2175874A
Application number: US220461A
Authority: US
Inventors: Reed J Caughey
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1938-07-21
Filing date: 1938-07-21
Publication date: 1939-10-10
Anticipated expiration: 1956-10-10

Description

Oct. 10, 1939. R. J.-CAUGHEY 2,175,874

TURBINE PROTECT IVE ARRANGEMENT Filed July 21, 1938 2 Sheets-Sheet 1 PowsR Dunccnoum. RELAY.

Inventor: IQeed J. Oaughey,

b x a/YWAM y Hi s s Attorfiey.

10, 1939- R. J. CAUGHEY 2,175,874

' TURBINE PROTECTIVE ARRANGEIENT Filed July 21, 1938 2 Sheets-Sheet 2 Fig.3.

PDWER DIRECTIONAL RELAY.

POWER D\RECTIONAL RELAY.

v Inventor FZee-d J. CauQhey,

b 561M 67) y His Attovney.

Patented Oct. 10, 1939 TURBINE PROTECTIVE ARRANGEMENT Reed J. omney, Schenectady, N. Y., aaaig'nor to General Electric Company, a corporation of New York Application July 21, ms, Serial No. 220,461

18 Claims.

The present invention relates to protective means for elastic fluid power plants and more particularly to arrangements for preventing overheating of superposed, back pressure turbines connected to electric current generators.

In enlarging older designed central stations. additional boiler capacity is usually provided which supplies steam or other elastic fluid at relatively high pressure to one or more superposed turbines which in turn exhaust to the existing low pressure header supplying operating fluid toone or more lower pressure turbines. The generators driven by the various turbines are usually connected together in parallel through the station buses to supply power to a network or other load.

Upon the occurrence of certain abnormal conditions, the flow of steam through the high pressure turbine may be reduced below that required for driving it full speed at no load. The lower pressure units may continue in operation at full or partial load either from the reduced flow of steam through the high pressure unit or from steam supplied from the lower pressure boilers. With the generators connected together, the direction of power flow will reverse through the generator of the high pressure unit to drive it as a motor and in turn drive the high pressure turbine at substantially full speed. It has been found that if a high pressure turbine is rotated at such a speed with a flow of steam being supplied thereto materially less than that normally required for driving it at no load, the internal temperature of the turbine may rise to a dangerously high value due primarily to the windage losses of the rotor.

Among the more common occurrences which may result. in the motoring of a superposed high pressure turbine through the generator are these:

(1) An accidental tripping of thehigh pressure emergency stop valve or failure of the governor control valve resulting in no flow of steam to the turbine and with the generator left connected to the line.

(2) .An abnormal rise in back pressure to the high pressure turbine due either :to an increase in the output of the low pressure boilers or faulty foperation of the reducing valve by-passing the high'pressure turbine. This increase in back pressure, operating on the back pressure regulatorof the high pressure turbine, greatly decreases the steam flow through the high pressure turbine until the; flow therethrough may reach a dangerous'minirn'um value.

(3) '.A loss or station load with the high and lower pressure turbine generators connected together. The no load flow of steam, as determined by the requirements of the low pressure turbines, would be materially less than the no 7 load flow of the high pressure turbine and hence 5 may be insumcient to prevent the overheating thereof.

(4) A sudden shut down of the high pressure boiler resulting in no flow of steam through the high pressure turbin but leaving the high pres- 10 sure turbine generator electrically connected to the buses. I

Because of the problems inherently involved in obtaining accurate indications of the rotor temperature and because of the relatively slow rate of thermal conduction through the turbine casing, means other than temperature indicating devices must be resorted to for preventing damage to the turbine blading upon the occurrence of any abnormal conditions, such as those listed, 2

likely to cause excessive heating.

It is an object of this invention to provide a new and improved arrangement for safeguarding a superposed high pressure turbine against overheating when being driven by its' generator by 5 disconnecting the high pressure turbine generator from the line in response to a predetermined reversal of power flow thereto.

It is a further object of this inventionvto provide a new and improved arrangement for pro- 30 tecting a turbine against overheating due to its being rotated by its connected generator with little or no elastic fluid flowing through it, by the elastic fluid flow through the turbine in response to a predetermined reversal of power flow to the generator so as to maintain the temperature thereof within safe limits.

' For a consideration of what I believe to be novel and my invention, attention is directed to the following specification and the claims ap- 0 pended thereto taken in connection with the accompanying drawings.

In the drawings, Fig. 1 discloses a typical superposed turbine power plant provided with one form of protective means according to my invention, and Figs. 2, a, and 4 disclose turbi he power plants of the type shown in Fig. I provided with protective means according to further modifications of my invention.

Referring to Fig. l of the drawings, III is a superposed back pressure turbine supplied with elastic fluid from the high pressure boiler ii. Suitable control valves, such as the emergency stop valve l2 and the throttle or admission valve it, are provided in the conduit ll supplying elas- Bl turbine. The exhaust from the high pressure turbine is conducted as by conduit l5, having a suitable check valve l6 therein, to the header I! to which may be connected one or more lower pressure turbines I8, or other elastic fluid consumers, through branch feeders I9. Additional elastic fluid may be supplied to the header I! from one or more lower pressure boilers 20 through conduit 2|. A connection, such as 22, having an automatic pressure reducing valve 23 therein, is also usually provided for supplying pressure turbine Ill or, in other words, the pressure in the header II. This may be accomplished by means of a back pressure regulator of a. wellknown form (not shown) for augmenting the regulation of the admission valve IS. The high and lower pressure turbines I and I6, are connected to

generators

24 and 25 which during normal operation supply power to the bus lines 26 in parallel connection through the feeders 21 and 7! respectively.

According to my invention a suitable circuit breaker indicated by a latched closed switch 29 is provided in the feeder circuit 21 having a suitable electro-magnetic closing operator 30. A power directional relay 3|, having contacts 32, is connected between the generator 24 and the circuit breaker 26 for closing an energizing circuit, including a suitable source of supply 33, for the circuit breaker trip mechanism 34 upon a' predetermined reversal of power flow from the bus lines 26 to the generator 24. Any suitable power directional relay may be used, such as that disclosed in Patent 2,110,673, A. J. Mc-

Connell, and assigned to the General Electric Company. Thus, if for any reason, such as upon the occurrence of one of the above listed conditions, the flow of elastic fluid through the turbine l0 should be reduced to the point where it will be driven-by its generator acting as a motor, the generator will be disconnected from the line before damage will be done to the turbine.

In central station operation, it is often undesirable to disconnect the generators from the station buses except in cases of absolute necessity. In a second modification of my invention shown in Fig. 21, an arrangement is provided which will effect a readjustment of the governor control means for the elastic fluid admission valves to the high pressure turbine so as to permit a suificient flow of fluid through the turbine upon the accurrence of certain predetermined abnormal conditions which conditions might-otherwise cause overheating of this tur- I0 is shown connected'to a suitable hydraulic operating motor 40 which is in turn controlled by the pilot valve 4|. The admission valve operating motor and pilot valve are normally regtic fluid from the high pressure boiler II to the ulated in a well-known manner as by a speed governor 42 which is shown as being driven through gearing '43 from the turbine shaft 44. The flyweights of the governor may be connected by link 45 to the governor beam 46 which is stationarily pivoted as at 41. Movements of the governor beam may be transmitted through link 48 to the floating lever 49 connected in the well-known manner to the stems of the pilot valve and of the operating motor.

Assume a normal condition of station operation during which the high pressure turbine is operating at partial load and at least one low pressure turbine is operating under full load,

the latter turbine receiving operating fluid exhausted by the high pressure unit. Now assuming a loss of station load, due to some extraneous reason, both turbines will tend to rise in speed. Since the high pressure turbine governor will close its admission valves by only a partial stroke, while a full stroke will be necessary to close the valves of the low pressure turbine, a slight increase of speed will normally close the valves of the high pressure unit whereas the same increase of speed will only partly close the low pressure turbine valves. Upon theresultant decrease of pressure in the header I1, the automatic by-pass valve 23 will open to pass operating fluid into the low pressure header, permitting the low pressure turbine to continue to run. The high pressure turbine will then be motored by a reversal of 'power flow to its' generator from the low pressure turbine generator. With little or no flow of elastic fluid through the high pressure turbine, it would rapidly overheat due to windage losses therein as explained above.

According to this modification of my invention, means are provided 'for biasing the high pressure turbine governor beam 46 against valve closing movements in response to a predetermined reversal of power flow to the generator 24. Such biasing of the governor beam may be accomplished by suitable control of the usual governor synchronizing spring, or by separate biasing means. As shown, a spring 50 is so arranged as to exert a force upon the governor beam 46 to oppose the valve closing movements of the governor 42. The spring 50, normally inactive, is arranged for. adjustment into a biasing position against the beam 46 by means of a suitable motor and gearing 52. The circuit 53 for the motor 5| is adapted to be energized from a suitable source of supply 54 through contacts 32 provided on the power directional relay 3|. Any'suitable means (not shown) may be provided for limiting the duration of operation of the motor 5|, or for restoring the biasing means to normal inactive position upon the resumption of normal station load conditions. By the arrangement shown, the motor 5| is energized upon a predetermined reversal of power flow through the generator leads 21 to exert a biasing force upon the governor beam 46 in opposition to the governor 42 so that the arms 'In this modiflcation a by-pass connection I -is' provided extending around the emergency stop valve l2 and the governor controlled admission valve It between the high pressure boiler and the turbine It. The by-pass connection is provided with a suitable valve 6! which is normally retained in its closed position as by spring means '82 connected to the valve operating lever 63. The valve may be opened by means of an electro-magnetic device 64, the

circuit 65 of which may be energized from a suitable --source of supply 66 through contacts 32 of the power directional relay 3!. By this arrangement upon the loss of station load and the resultant closure of the governor controlled admission valve It, as described above, the power directional relay 3| will close the contacts 32 to energize the electromagnetic operator M for opening the by-pass valve I. The by-pass connection may be of such size so that it will passan amount of elastic fluid to the turbine ll substantially equal to the no load flow required for keeping the turbine sufllciently cool. Itwill be noted thatthis arrangement will also protect the high pressure turbine against overheating upon the occurrence of conditions (1) and (2) as well as (3), as described.

In Fig. 4 is shown a further modification in which a flow of cooling elastic fluid is allowed to pass through the turbine III in the reverse direction upon the occurrence of one of the conditions outlined above. An exhaust connection 10 extending from the first stage shell is provided'with a valve H normally retained in the closed position by such means as the spring 12 connected to the operating arm 13. The valve is actuable to the open position by the electromagnetic actuating means 14 connected to the valve operating arm. 13. The normally unidirectional or check valve It in this instance is provided with an operating arm 15 to which is connected an electro-magnetic actuating device 18 for holding the valve open so as to allow fluid flow therethrough in the reverse direction. The electro-

magnetic devices

14 and 16 may be connected in parallel and arranged for simultaneous energization from a suitable source of supply-Tl through the contacts 32 of the power directional relay 3|. By this arrangement, upon the occurrence of any abnormal condition resulting in the closure of either of the valves I! or ii, or upon the failure of the boiler II, with the generator left connected to the buses, a suflicient flow of elastic fluid for maintaining the temperature of the turbine lll within safe limits may be circulated through the turbine in the reverse direction from the header l1. Upon the reversal of a predetermined power flow to the generator 24,

the check valve IE will be held open thereby allowing low pressure elastic fluid to flow from the header I'I, through the turbine III in the reverse direction and discharge through the exhaust connection 10.

Having described the'principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of theUnited States is:

'1. In a superposed power plant system, the.

. combination including a source of relatively high low pressure elastic fluid including the exhaust of said high pressure turbine, a lower pressure turbine connected to said last-mentioned source.

generators coupled to said turbines and arranged for parallel operation, means for preventing overheating of said high pressure turbine upon said high pressure turbine being driven by its generator, said means including a power directional relay responsive to a predetermined flow of power to said high pressure turbine generator.

2. In a superposed power plant system having a source of relatively high pressure elastic fluid. a high pressure turbine connected to said source. a source of relatively low pressure elastic fluid, a lower pressure turbine connected to said lastmentioned source, electric generators driven by said turbines and normally electrically connected together for parallel operation, means for preventing overheating of said high pressure turplying power to the station buses, governor means for regulating the supply of elastic fluid to said turbine, a power directional relay responsive to a predetermined flow of power to said generator, and valve means responsive to said relay for admitting elastic fluid to said turbine independently of said governor means.

4. In a superposed power plant system comprising high and low pressure turbines for normally driving parallel connected generators, the

combination including governor means for regulating the supply of elastic fluid to said high pressure turbine, a power directional relay responsive to a predetermined flow of power to said high pressure turbine generator, and valve means responsive to said relay for admitting elastic fluid to said high pressure turbine independently of said governor means.

5. In a superposed power plant system comprising high and low pressure turbines coupled to parallel connected generators, means for preventing overheating of said high pressure turbine upon its being driven by its generator, said means comprising a power directional relay responsive to a predetermined flow of power to said high pressure turbine generator and a valve adjustable by means including said relay for admitting elas tic fluid to said turbine.

65. In a power plant, an elastic fluid turbine, a generator coupled to saiditurbine, buses normally adapted to be supplied with power from said generator, elastic fluid admission valves for said turbine, a governor for regulating said valves, means for regulating the supply of elastic fluid to said turbine independently of the position of adjustment of said governor means, a power directionalrelay responsive to a predetermined flow of power from said buses to said generator for controlling said last-mentioned means.

7. In an elastic fluid power plant, a turbine, a generator normally driven by said turbine for supplying power to station buses, means for preventing overheating of said turbine upon its being driven by a reversal of power to its generator, said means comprising a power directional relay responsive to a predetermined flow of power to said generator, and valve means responsive to said -relay for admitting elastic fluid to said trically connected to common buses for parallel operation, a circuit breaker for disconnecting,

said high pressure turbine generator, tripping means for said circuit breaker, and a power directional relay responsive to a predetermined flow of power from said low pressure turbine generator to said high pressure turbine generator for energizing said circuit breaker tripping means.

9. In a superposed power plant system having a source of relatively high pressure elastic fluid, a high pressure turbine connected to said source, a relatively low pressure turbine connected to the exhaust of said first turbine,,electric generators driven by said turbines and normally electrically connected together through common buses for parallel operation, means for preventing overheating of said high pressure turbine due to Windage losses occasioned by said high pressure turbine being motored by its generator supplied with energy from said low pressure turbine generator, said means including a power directional replay responsive to a reversal of flow of energy to said high pressure turbine generator for disconnecting said last-mentioned generator from said low pressure turbine generator.

10. In a superposed power plant system com- .prising high and low pressure turbines for normally driving parallel connected generators, means for preventing overheating of said high pressure turbine upon its being driven by its generator, said means including the combination of governor means for regulating the supply of elastic fluid to said high pressure turbine, a power directional relay responsive to a predetermined flow of power to said high pressure turbine generator, and valve means normally controlled by said governor responsive to said relay for admitting elastic fluid to said high pressure turbine.

11. In a superposed power plant system comprising sources of relatively high and low pressure elestic fluid, a high pressure turbine arranged between said two sources, a generator normally driven by said turbine and supplying power to the station buses, a power directional relay responsive to a predetermined flow of power to said generator from said buses, and means responsive to said relay for admitting elactic fluid from said low pressure source to said turbine.

12. In a superposed power plant system comprising sources of relatively high and low pressure elastic fluid, a turbine arranged between said sources, a generator normally driven by said turbine and supplying power to the station buses, a power directional relay responsive to a predetermined flow of power to said generator from said buses, valve means responsive to the actuation of said relay for admitting elastic fluid from said low pressure source through said turbine in the reverse direction.

13. In a power plant, a high pressure header, a low pressure header, a high pressure elastic fluid turbine arranged between said headers, an electric generator normally driven by said turbine and supplying power to the station buses, a normally unidirectional valve for precluding flow of elastic fluid from said low pressure header to said high pressure turbine, conduit means including a normally closed exhaust valve in communication with the inlet chamber or said high pressure turbine, a power directional relay responsive to a predetermined flow of power from said buses to said generatorfor causing the opening of said unidirectional valve and said exhaust valve whereby elastic fluid is permitted to flow from said low pressure header through said high pressure turbine.

14. In combination, an elastic fluid turbine, an electric generator normally driven by said turbine connected to station buses, valve means forcontrolling the admission of elastic fluid to said turbine, a governor driven by said turbine for normally regulating said valve means, and means responsive to a predetermined reversal of power flow to said generator for effecting an increase in the supply of elastic fluid to said turbine irrespective of the position of adjustment of said governor for preventing overheating of said turbine upon said turbine being motored by'said generator.

15. In combination, an elastic fluid' turbine, governor controlled means for normally regulating the supply of elastic fluid to said turbine, an electric generator normally driven by said turbine, means for normally connecting said generator to station buses, means for preventing overheating-of said turbine upon said turbine being motored by said generator, said means comprising a device responsive to a predetermined reversal of power flow from said buses to said generator, and means controlled by said device for adjusting said governor controlled means for increasing the supply of elastic fluid to said turbine.

16. In combination, an elastic fluid turbine, an electric generator normally driven by said turbine, means for normally connecting said generator to station buses, elastic fluid admission valves for said turbine, governor means driven by said turbine for normally regulating said valves, and means responsive to a predetermined reversal of power flow to said generator for increasing the supply of elastic fluid to said turbine irrespective of the operative position of said governor means. I

17. In combination, a source of relatively high pressure elastic fluid, a turbine normally receiving elastic fluid from said source, an electric generator normally driven by said turbine for supplying power to station buses, a source of relatively low pressure elastic fluid, a header supplied with elastic fluid from said low pressure source, conduit means for normally conducting the exhaust fluid from said turbine to said header, a unidirectional valve in said conduit means for normally precluding reversal of elastic fluid flow from said header to said turbine, means responsive to a predetermined reversal of power flow to said generator, and means controlled by said last mentioned means for permitting a circulation of elastic fluid from said header through said turbine.

18. In combination, a source of relatively high pressure elastic fluid, a turbine normally receiving elastic fluid from said source, a generator normally driven by said turbine and connected for supplying power to station buses, a source of relatively low pressure elastic fluid, a header supplied with elastic fluid from said low pressure source, conduit means for normally conducting through said conduit means to said turbine, and normally closed valve means operable upon actuation of said reverse power responsive means for permitting the exhaust of said reverse fluid flow from the inlet endoi said turbine.

REED J. CAUGEJY.

CERTIFICATE OF CORRECTION.

Patent No 2,17 5,871

October 10, 1959 REED J. CAUGHEY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, second column, line 10, for "turbin" read turbine; page 2, first column, line 59, for "accurrence" read 9, for "replay" read relay; line 57, claim 11, for "elactic" read occurrence; page l first column, line 31, claim elastic;

and that the said Letters Patent shouldbe readwith this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 12th day'of December, A. D. 1959.

(Seal) Henry Van Arsdale,

Acting Commissioner of Patents.