Operation 367
into DACSs. In particular, these devices were included as part of the regular automated control and surveillance complexes delivered by Turboatom with various modifications of their K-750-65/3000 and K-1000-60/1500 turbines, as well as built into projects of DACSs for newly designed nuclear power units with K-500-65/3000 turbines. 180 Emulations of automated start-ups and load changes for such a turbine are shown in Figures 4–11 and 4–12, and the diagram of an actual start-up of this turbine at the Chernobyl power plant with experimental samples of such devices is shown in Figure 4–75.
Fig. 4–75. Cold start-up of Turboatom’s K-500-65/3000 turbine at the Chernobyl nuclear power plant with current admissible load boundaries based on the HP rotor’s monitored thermal stress state as presented to the operator
The devices shown in Figures 4–72 and 4–74 were constructed using mathematical models based on the method of approximate transfer functions. With the use of different kinds of computational techniques, other approximate mathematical models can be more convenient—for example, based on the definite difference method, which has been successfully used in many developments.
Automated control of transients, predominantly start-ups, promotes more reliable power plant operation. One of the world’s first automated devices and systems of this kind for wet-steam turbines was a start-up automaton developed for Turboatom’s K-220-44 turbine
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368 Wet-Steam Turbines for Nuclear Power Plants
and put into commercial operation at the Kola nuclear power plant as early as in the mid-1970s.181 Its control desk is shown in Figure 4–76. Presently, it looks rather archaic, with its multitude of indicators, switches, buttons, and signal lamps, because now all of their functions are performed with greater effectiveness and ergonomic comfort based on modern computer technologies. Nevertheless, the technology essence of this automaton remains quite valid.
Fig. 4–76. Control desk of the start-up automaton for the K-220-44 turbine at the Kola nuclear power plant (I: indicators for current actual and set values of controlled parameters: 1: steam pressure downstream of MSG (at the stage of prestart heating); 2: steam temperature downstream of MSR; 3: rotation speed (at the stage of running up); 4: load (at the stage of loading); II: signal panels and lamps: 5: causes of deviations from the normal technological course (stage by stage); 6: accomplishment of start-up operations (stage by stage);
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Operation 369
7: general signals for all stages (accomplishment of the stage, suspension of accomplishment, return to the previous stage, switching all the control actions off); 8: readiness to execute the set stage; III: devices controlled by the operator: 9: permission button to begin the executing stage; 10: permission button to repeat the stage operation after return to the previous stage;
11:multi-position switch of the mode which the automaton functions;
12:multi-position switch of the start-up stage; 13: set point device for the final load value; 14: input of information about accomplishment of preliminary manual operations; 15: input of permission to raise the rotation speed up to the synchronous rate (listening to the turbine is finished); IV: remote control devices, including start-up governors and position indicators for governing valves)
Source :A. S. Leyzerovich,A. D. Melamed,V. B. Kirillov, et al.182
The entire start-up process under automated control is divided into three steps: 1) the prestart heating of the main steam lines and HP valve steam-chests (for power units without a main steam gate between the reactor’s steam-generator and the turbine’s stop valves, this stage is omitted), 2) running-up to the subsynchronous rotation speed, and 3) loading to the rated or set final output.The automaton (or any other automated start-up system) should comprise special program governors and logical controllers influencing the turbine’s discrete position objects, including the start-up governors. Of importance are the collaboration between the operator and the automated devices and friendly human–machine interface.The operator should be able to trace the course of the automated operations, and the entire progression of operations should be tied to the actions accomplished by the operator.
The automaton’s running-up programs were unified for all types of start-ups (Fig. 4–77). When the generator was switched on to the grid and the loading governor was brought into operation, the turbine load was initially raised at the maximum admissible rate up to the primary load level, and then increased according to the set program (Fig. 4–78). Two types of loading programs were tested and then used in different projects: 1) a program derived from Equation 4.4, based on tracing the current value of the monitored metal temperature on the HP casing flange’s external surface and 2) a “program-in-time” of loading the turbine at the rate changed depending on the current load value (Fig. 4–67b).
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370 Wet-Steam Turbines for Nuclear Power Plants
Fig. 4–77. Experimental automated running-up of the turbine for various start-ups (1: cold start-up with vacuum of 710 mm Hg [13.7 psi]; 2: hot restart just after rolling-down; 3: hot start-up with vacuum of 600 mm Hg [11.6 psi];
A:beginning of opening HP control valves and passing heating steam to MSR;
B:signal to the operator to listen to the turbine; C: permission of the operator for further increase of the rotation speed after listening to the turbine;
D:reaching a subsynchronous rotation speed, signal to prepare the generator to be synchronized and switched on to the grid)
Source :A. S. Leyzerovich,A. D. Melamed,V. B. Kirillov, et al. 183
The loading program-in-time is presented in the form of a linear dependence for the rate of increasing the set on its current value:
• |
∂Nset |
∂Nset |
|
∂p |
• |
(4.8) |
Nset = |
∂τ |
= ∂p |
× |
∂ts |
× [tm] a + bNset |
•
where [tm] is the rate of heating up the critical element necessary to keep its leading indication at the upper admissible level (for wet-steam turbines, it is possible to neglect the influence of the metal temperature on the metal temperature conduction and take
•
[tm] = const); ∂p/∂τs is the dependence between the steam pressure and saturation temperature, which can be regarded as a linear function of pressure with an error less than 5–10% in the pressure range from 1.2 to 6.5 MPa (175–950 psi), and ∂N/∂p const is the proportional coefficient between the turbine load and heating steam pressure for the critical element.The initial load value, t inset, that can be reached with an unlimited, maximum admissible rate is set according
to the initial metal temperature of the critical element, tmin.The depen-
•
dencies Nset(Nset) and N inset(tmin) for K-220-44 turbines are presented in Figure 4–67.
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Operation 371
Fig. 4–78. Experimental automated loading of the turbine at hot (a) and warm (b) start-ups (A: switching on the loading governor; B: finish of the initial loading stage at the maximum rate; C: reaching the set final load level; tst : steam temperature in the HP steam admission chamber, tfl : metal temperature on the HP casing flange’s external surface)
Source :A. S. Leyzerovich,A. D. Melamed,V. B. Kirillov, et al.184
The ordinary loading programs-in-time have a principal disadvantage: if execution of such a program is interrupted or suspended, the controlled process thereafter differs from the optimal one in principle. This is especially typical for loading wet-steam turbines at start-ups, when the loading process is often suspended by regular operations with the reactor. If the turbine load is kept constant, the heating steam temperatures within the turbine do not vary, and the value of the leading indication (the temperature difference in the critical element) decreases almost exponentially with the time constant T After the loading process is resumed, it is possible to increase the load at the maximum admissible rate within the load range, the value of which depends on the duration, ∆τ , of the previous suspension:
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372 Wet-Steam Turbines for Nuclear Power Plants
∆N = A(N) × [1-exp(–∆ /T)], |
(4.9) |
where A(N) is the admissible step-like load change after holding the load at a constant level for an uncertainly long amount of time.
A principle block-chart of the automated device for loading wetsteam turbines during start-up is shown in Figure 4–79. The set on the turbine load, measured by the sensor (11), is worked out by the governor (2) influencing the turbine control valves (1).The set for the governor is formed by the integrator (3), which is connected through the switch (5) to pulsers (either 6 or 7) of the program and maximum upper admissible rates of loading, respectively.At the beginning stage of the loading process, until the turbine output reaches the initial value corresponding to the prestart metal temperature measured by the sensor (10), the rate of loading is set to the maximum.As soon as the turbine load reaches this value, obtained at the outlet of the nonlinear transducer (9), the logical device (8) switches over the programmer
(6) to the inlet of the integrator (3), instead of the other pulser (7). This programming device (6) is provided with positive feedback from the outlet of the integrator (3).
This system also comprises another logical device (16) influencing the switch (4) between the integrator and its pulsers. It may be done by the operator or a logical control device of a higher range (for example, if loading the reactor is suspended). In this case, the switch (14) is closed, and the dynamic converter (15) begins forming the value ∆N depending on the time length of the suspension, ∆ , according to Equation 4.9.When the process of loading is resumed, the switch (4) is closed, the switch (14) is opened, and the third logical device (12), influencing the switch (5), provides loading at the maximum rate allowable within the value of ∆N.Then the turbine is again loaded with the program rate formed by the pulser (6).
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Operation 373
Fig. 4–79. Principle block-chart of automated device for loading a wetsteam turbine during start-ups (1: turbine control valve(s); 2: executing
governor; 3: integrating set-point device for |
executing governor; 4, 5, |
14: switches; 6, 7: pulsers (as programmers); |
8, 12, 16: logic devices; |
9, 13: nonlinear transducers; 10: metal temperature sensor; 11: turbine load sensor; 15: dynamic converter)
Both of these types of programs were later used for start-up automation of other wet-steam turbines.A diagram of one of regular automated turbine start-ups at the Kola nuclear power plant is shown in Figure 4–80. The leading indication for the turbine (the temperature difference across the HP flange width) is kept close to the upper admissible level, approximately 80°C, and the reheat steam temperature after the MSR is raised in a manner providing close to optimal heating of the LP rotors. The loading process for another regular automated start-up is shown in Figure 4–71.
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374 Wet-Steam Turbines for Nuclear Power Plants
Fig. 4–80. Automated start-up of a K-220-44 turbine at the Kola power plant (A: the operator switches on the start-up automaton, and steam enters the turbine; B: the operator confirms completion of listening to the turbine, and the turbine rotation speed begins increase to the synchronous value, with the program governor for the reheat steam temperature switched on automatically; C: the turbine reaches 3,000 rpm, and the operator takes over control for synchronizing and switching on the generator; D: the operator switches the generator on, and the turbine accepts an initial load; E: the operator permits further loading; F–G: the operator suspends loading to switch on the HP feed water heaters; G: the operator increases the set final load value; H: the final load value is reached; I: the automated start-up is completed, and the operator switches off the automaton)
Source :A. S. Leyzerovich,A.S.,A.D. Melamed,V.B. Kirillov, et al.185
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Operation 375
References
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4Schwieger, First annual top plants survey. 27–70.
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7Sekine, Y. 1993. Nuclear power generation in Japan—Present status and future prospects. Proceedings of the Institute of Mechanical Engineers 207 (A4): 233–246
8Proselkov, V. N., and V. D. Simonov. 1989. Technical problems associated with participation of nuclear power plants in governing load of power systems (in Russian). Energokhozyajstvo za Rubezhom 3: 11–15
9Kirillov, V. B., and A. S. Leyzerovich. 1985. Flexibility characteristics of wet-steam turbines of nuclear power stations. Thermal Engineering 32 (7): 366–370.
10 Mizuki, F., Y. Miyamoto, and T. Seiji. 1998. Control and instrumentation for ABWR plant. Hitachi Review 47 (5): 164–167.
11Ibid.
12Arkad’ev, B. A. 1986. Operating Conditions of Steam Turbosets for Nuclear Power Plants (in Russian). Moscow: Energoatomizdat, 1986.
13 Ibid.
14 Ibid.
15 Ibid.
16Akerman, V. S., N. S. Gabrijchuk, V. B. Kirillov, A. S. Leyzerovich, et al. 1984. Results of field start-up tests for K-500 - 60/1500 turbine (in Russian)
Elektricheskie Stantsii 2: 5–10.
17 Ibid.
18 Leyzerovich, A. S., and V. B. Kirillov. 1976. Optimization of start-ups of turbines at nuclear power stations by a method of mathematical simulation. Thermal Engineering 23 (2): 30–34.
19Leyzerovich, A. S., V. B. Kirillov, S. P. Kruzhkova, et al. 1976. Investigating startup operating conditions of the K-220 - 44 wet-steam turbines at Kola nuclear power plant (in Russian). Elektricheskie Stantsii 5: 34–39.
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376 Wet-Steam Turbines for Nuclear Power Plants
20 Leyzerovich, A. S., B. L. Levchenko, and V. B. Kirillov. 1983. Mathematical investigation of variable operational conditions of the LMZ K-1000 - 60/3000 turbine. Thermal Engineering 30 (1): 20–25.
21Leyzerovich, 1997. Large Power Steam Turbines: Design & Operation
Vols. 1–2. Tulsa, OK: PennWell Publishing, 1997.
22Ibid.
23Leyzerovich, A. Optimization of start-ups of turbines. 30–34.
24Madoyan, A. A., and L. N. Kobzarenko. 1986. About expediency of motor conditions for steam turbines of nuclear power plants (in Russian).
Teploenergetika 33 (3): 8–10.
25Bergmann, D., M. Gloger, G. May, and G. Gartner. 1985. High temperature control in high backpressure LP turbines. Proceedings of the American Power Conference 47: 219–229.
26Gribov, N. N., A. S. Shemonaev, and E. S. Mandryka. 1988. Vibrational state of moving blades in the final stage of the low pressure section of a high-capacity steam turbine as a function of the volumetric flow of steam. Soviet Energy Technology 5: 24–27.
27Khaimov, V. A., P. V. Khrabrov, Y. A. Voropaev, and O. E. Kotlyar. 1991. Lowflowrate operating modes and the reliability of the T-250/300 -23.5 turbine.
Thermal Engineering 38 (11): 594–597.
28 Leyzerovich. Large Power Steam Turbines
29 Kosyak, Y. F. 1987. Development by Turboatom of turbine construction for nuclear power plants. Thermal Engineering 34 (8): 405–408.
30Jacobsen, G., H. Oeynhausen, and H. Termuehlen. 1991. Advanced LP turbine installation at 1300 MW nuclear power station Unterweser. Proceedings of the American Power Conference 53: 991–1001.
31 2004. Site work underway on Finland’s 1600 MWe EPR. Modern Power Systems 3: 30 -34.
32 Kosyak, Development by Turboatom. 405408.
33ASME. 1976. ASME Performance Test Codes: Code on Steam Turbines. ANSI/
ASME -PTC 6 -1976. New York: ASME, 1976.
34Sakharov, A. M. 1990. Heat-Rate Performance Tests of Steam Turbines (in Russian). Moscow: Energoatomizdat, 1990.
35 Pawliger, R. I., A. Roeder, E. Mueller, and Z. S. Stys. 1982. Experience in heat-rate acceptance tests of steam-turbine generators. Proceedings of the American Power Conference 44: 320–329.
36Bornstein, B., and K. C. Cotton. 1981. A simplified ASME acceptance test procedure for steam turbines. Combustion March: 40–47.
37 Ibid.
38 Pawliger, Experience in heat-rate acceptance tests. 320–329.
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