Hydropower Preventive Monitoring Action Plan MIRCEA GRIGORIU 1, MARIUS-CONSTANTIN POPESCU 2 1 University POLITEHNICA Bucharest, 313 Spl. Independetei, Bucharest, ROMANIA 2 University of Craiova, ROMANIA 3 Universty Constantin Brancus, Targu Jiu, ROMANIA mircea.grigoriu@gmail.com, popescu.marius.c@gmail.com http://www.hydrop.pub.ro Abstract: Hydropower generators operation can be automatically optimized based on a correct determination of the main performance indices. The same approach is operable for rehabilitation studies. The most important application refers at small and very small hydropower stations, operating completely automatically, and individual or in a waterfall. There were established resistors parameters, adjustment characteristics, efficiency characteristics at different operation regime, and main types of losses at different regime. It is generated a computer of modeling process, considering these parameters, utilizable in mentioned applications. The numerical example is presented for a small hydropower generator type HVS 288/159-8, working in a hydropower station on the Jiu River. Key-Words: Hydropower, Components, Parameters evaluation, 1 Introduction Available hydraulic energy of power station placed on a water course can be expressed by the relation W h =ρ g V H (1) where: W h - energy [J], H - specific energy [m], V - water flow mass expressed in [m 3 ], ρ - water density in operation conditions [kg/m 3 ], g - gravitation acceleration [m/s 2 ]. Or, using an old and not standardized expression: W h = 9. 81 V H (1 ) where: V - water mass expressed in [kg f]. Hydraulic power represents the energy changed by the water with the turbine rotor and has the expression P h =ρ g Q H (2) where: P h - hydraulic power, offered by the water flow to the turbine. Q - water flow rate [m 3 /s], Electrical power offered by the generator to the network has the expression: P =η (3) el P h where P e - electric power, offered by the hydro turbine to the network. η - generator-turbine ensemble efficiency. The efficiency can be divided: in turbine efficiencyη t, transmission efficiencyη tr, and electrical generatorη. Ensemble efficiency is a t tr g g η = η η η (4) where η - is the total efficiency. a It is obvious that the final generated electrical power is in direct dependency with the total efficiency. Consequency, the generator efficiency is one of the main research directions, taking into consideration the main types of losses. There are specific methods to evaluate the whole efficiency, or focussing on the main types. 2 Determining Performance indicators ISSN: 179-595 265 ISBN: 978-96-474-159-5
The purpose of the work is to establish a method for the correct parameters evaluation in an appropriate form, and to compare these parameters with the parameters indicated by the provider. The numerical example is presented for a small hydropower generator type HVS 288/159-8, working in a hydropower station on the Jiu River. The result application could be in operation monitoring and in refurbishment undertaken. To establish the performance indices of a hydro test using a package structured as follows: determination of Ohm resistance of rotor windings in cold state, raising the idle characteristics and three-phase symmetrical short circuit of the generator, raising characteristic in V and P =, clearance adjustment characteristic, determining environmental warming stator winding stator and rotor winding to a total of four operating regimes, determining the actual PQ diagram for hydro and determining the nominal yield and the conventional yield curve. Function tests will be conducted under thermal load stabilized at different levels of active and reactive power at rated power factor (cosφ n ). After running the generator tests, maximum load active and reactive power and thermal considerations yield curve of the conventional generator. Temperature of stator winding and stator core is determined by measuring the temperature resistance that fitted generator mounted in notches generators. 2.1 Rotor winding resistance determination To determine the resistance of rotor winding is necessary to measure the reference temperature θ of winding. For this, a precision thermometer.1 C set on copper runner after the generator has reached the ambient temperature appreciatively after about 24 hours of downtime. The resistance value R θ to a value other than that measured temperature thermometer is determined by the relationship: R θ =R θ (235+θ)/(235 +θ ) (5) where R θ is the resistance at θ reference temperature; R θ is resistance at the reference temperature θ. Rotor winding temperature in the samples heat-stable operating system is determined by resistance change method using the relationship: θ=(r θ -R θ )R θ (θ +235)+θ (6) The resistance of the winding rotor at the corresponding temperature θ is determined each time by the method of voltmeters and ampeters. To this end, after determining the heat and after reading the other parameters, it will stop the generator and rotor resistance R will measure θ. Measurement will be made in less than three minutes from the stop so that the temperature θ is determined as close to the real one. Temperature of stator winding and stator core is determined by measuring resistance temperature transducer is equipped with generator mounted in notches generators and using the data obtained experimentally was prepared Table 1. Table 1 Parameter UM Hidrogenarator designed mess HG Rotor winding at 13 C Ω,28,219 8 Rotor winding at 75 C Ω -,186 7 Rotor winding at 15 C Ω -,15 6 Reactant P u.r.,148 Reactant Syncron x d u.r. 1,196 1,436 Short circuit report U n şi -,95,74 f n Excitation report U n şi f n A - 342 Idling voltage at V 53 54 excitation U n şi f n Excitation electrical A - 385 current at idling and short circuit at I n Excitation voltage at V - 61 short circuit ati n Normal current cosφ n A 69 687 Current efficiency P n cosφ n % 97,77 96,87 2.2 Adjustment features evaluation Feature adjustable tension builds to a different voltage rating to obtain the corresponding characteristic Voltage (U n ) and the nominal frequency (f n ) will recalculate feature nominal terms using the following relations: I ex =I ex.mas +( U n /f n f mas /U mas -1) I ex.on (7) I ex.n =U n /f n f.mas /U I ex.mas (8) where the excitation current I ex is corrected, I ex.mas current excitation is measured at lifting adjustment feature, f mas is frequency measured at lifting tuning feature, U mas is the voltage measured at lifting tuning feature, I exn. current excitation is idling properly rated voltage and frequency of idling not translated ISSN: 179-595 266 ISBN: 978-96-474-159-5
curve, I ex.mas current excitation is measured at raising nominal voltage characteristic corresponding goals and f mas, U mas are frequency voltage that measured at raising idle feature. Corrected value of excitation current (I ex ) corresponds to a current value corresponding stator current excitation is measured and presented in Table 2 for different levels of power. Table 2 P Q U Uex Iex I MW MVAr V V A A 1,1-16,97 1,22 92 555,2 96 1, -16,28 1,15 9 543,2 92,95-14,2 1,5 84 56,9 82,95-12,47 9,98 8 482,8 7 1,1-1,39 9,94 74 446,6 6 1, -7,97 9,88 68 41,4 48,9-5,2 9,85 62 374,2 36,9-3,12 9,87 54 325,9 2,95 -,35 9,82 48 289,7 1, +3,46 9,75 38 229,3 2 1, +4,5 9,68 36 217,3 26 Measuring values and adjustment of the excitation current are presented in Table 3 and fig.1. Table 3 Nr. I I ex măs. I ex U f Cosφ crt. recalc. A A A KV Hz 1. 251,5 5 2. 138 55,2 55,8 9,9 5,895 3. 148 555,2 568,6 1,1 5,915 where: P, Q are the active power reactive in relative units, U f is the basic tension in relative units, E d is the longitudinal electric voltage in relative units, synchronous reactance X d is longitudinal, synchronous reactance Xq is transverse, and θ is the internal angle. The origin of excitation current has coordinates P =, Q =- U f ² x Q. Natural static stability limit is determined using the criterion dp/dq, resulting in internal angle values following relations: Q = arcos[1/8(-a + a²+32)] (11) a = (E d /U f ) 2X q /(X d -X q ) (12) Practical limit of static stability is determined by graphic method of natural limit for a reserve of 1%. Limit heat supplying sub excited duration is determined by special similarity to determine the actual limit. The limit is determined as indicative. This limit is the straight line joining points of coordinates: P = P n, Q =-.15 S n P =, Q =-.5 S n. (13) Operating thermal limits under the indicative (if any) is determined from the condition of mentaining mechanical temperature allowable stator windings and core, as follows: - The experimental diagrams θ r = f (I ex ²), with θ = f (I ²) and θ Fe = f (I ²) at cosφ = cosφ n circuit runner is determined that the stator corresponding maximum allowable temperature for insulation class and the stator core (12 C for winding and stator core 13 and C to carry out these rotor). Fig.1. Adjustment characteristic 2.3 Determination of PQ diagram For the preparation diagram P=f(Q) for hydroelectric generator will use the relations: P=(U f E d /X d ) sinθ+u f ²/2(1/X q -1/X d )sin2θ (9) Q=(U f E d /X d ) cosθ+u f ²/2(1/X q -1/X d )cos²θ-u f ²/X q (1) Fig.2: Characteristic thermal stator winding and stator core of hydro generator Temperature values are given in the technical manual generator. ISSN: 179-595 267 ISBN: 978-96-474-159-5
- Calculating the maximum active and reactive power according to: S = 3 IU, P = Scosφ, Q = S ²-P ² (14) Values of active power, reactive and apparent are presented in Table 4. Table 4 Regim P Q S cosφ I MW MAV MVA - A r 1 25, 12,47 27,93,895 166 2 2,2 1,5 22,56,895 13 8 3 15,2 7,62 17,,894 1 4 23,8 1,39 26,,915 148 Regim U f I ex U ex R r kv Hz A V Ω 1 9,7 5-1 - 2 9,9 5 53,2 86,1622 3 9,9 5-73 - 4 1,1 5 555,2 92,1657 Fig.3: Standard PQ diagram in three modes of operation (idle non excited the rated speed, idle speed and voltage excited to rated the generator terminals and went to a landing load power), the winding Indus resistance and the excitation winding, heating characteristics obtained experimentally induced and the winding of the winding excitation characteristics idle and three phase short circuit, symmetric permanent terminals and resistance Potties. Efficiency values determined for a conventional hydro power of 3.6 MW are presented in Table 5 and the corresponding conventional yield curve is shown in Fig. 4. K 1/4 2/4 3/4 4/4 cosφ -,9,9,9,9 I A 468 935 143 187 I ex A 484,1 55,2 629,5 76,5 P m+vent kw 424,2 424,2 424,2 424,2 P fe kw 285,7 285,7 285,7 285,7 P cu1 kw 5,78 23,8 51,97 92,32 P cu ex kw 39,37 5,86 66,57 83,86 P aex kw 6,95 8,89 11,75 14,8 P s kw 3,63 14,47 32,58 57,89 ΣP kw 765,6 87,3 872,8 958,8 P kw 765 153 2295 36 η conv % 88,99 94,72 96,2 96,87 K 1/4 2/4 3/4 4/4 cosφ - 1 1 1 1 I A 468 935 143 187 I ex A 445,5 482,7 541, 65, P m+vent kw 424,2 424,2 424,2 424,2 P fe kw 285,7 285,7 285,7 285,7 P cu1 kw 5,78 23,8 51,97 92,32 P cu ex kw 33,34 39,14 49,17 61,49 P aex kw 5,88 6,91 8,68 1,85 P s kw 3,63 14,47 32,58 57,89 ΣP kw 758,5 793,5 852,3 932,5 P kw 85 17 255 34 η conv % 91,8 95,33 96,66 97,25 Table 5 2.4 Efficiency evaluation In accordance with conventional standards in force output of the generator is determined using the loss separation method, using the general relationship definition. η = 1 P charged / (charged P + ΣP loss) (14) The yield will be determined for 25, 5, 75 and 1% of rated load, considering that the terminal voltage, frequency and power factor are nominal values. The quantitative determination of individual losses and efficiency for all modes of load is obtained by calculation using the following experimental: losses caused by calorimetric method Fig. 4. Efficiency characteristic 2.5 Determination of losses ISSN: 179-595 268 ISBN: 978-96-474-159-5
2.5.1 Determination of Mechanical losses Mechanical losses are determined by calorimetric method to test idle non excite. Radial-axial bearing losses are fully included in the total loss of the generator, and the radical camp lower losses are distributed between the generator and turbine rotating sub-assemblies in proportion to the masses. Is determined by calorimetric method to test idle excited with rated voltage at the terminals induced. It is considered to be proportional to the square metallic suport B induction in δ. For reference to another value than the existing tension in the test is a used relationship: P Fe2 = P Fe1 (B δ2 / B δ1) ² = P Fe1 (E δ1 / δ2 E) ² (16) E ² = δ (U + X p I sinφ) ² + (X P I cosφ) ² (17) where δ E is the corresponding electric voltage induction in metal support B δ, U, I are the voltage and current induced on the beam, cosφ is the power factor and X p is the Potier reactance; proportional to the square of the induced current, so with a single experimental determination, they can be calculated for any value of the induced current: P s1 = s2 P (I 2 / I 1) ² (2) where: P s1 are determined by calculating the losses for the induced current I 1 and P s2 are losses due to current I 2 in experimentally induced. 2.5.5 Determination of Joule effect losses in the windings of excitation P = R Cu.ex ex ex ² I 1-3 [kw] (21) in which R ex is the excitation current for a given system load measured or calculated by standard methods using one of the characteristics idling three phase short circuit and value reactants Potier. The operation of the generator empty (I = ) result is δ = U, then: P Fe2 = P Fe1 (U 2 / U 1 ) ² (18) Using relationship (18) is the correction iron losses if the sample excited empty terminal voltage has nominal value. 2.5.3 Determination of Joule effect losses in the winding Indus Joule effect losses are determined by the relationship: Cu1 P = 3R 1 I 1 ² 1-3 [kw] (19) where: R 1 is a phase induced resistance temperature of 75 º C and I 1 is the current phase of the Indus 2.5.4 Determination of additional losses in Pregnancy Is determined by deducting losses and mechanical ventilation, the iron losses, the losses by Joule effect losses in the windings and excitation system of the total losses measured by calorimetric method in operation under load. Are considered to be Fig.5: Thermal charactristic 2.5.6 Determination of losses in equipment Excitation This category includes all losses except the installation of the stator winding losses (circuits, thyristor converter, and transformer excitation). It is considered an overall yield of the plant excitation η ex = 85% and we have: P ex = P Cu.ex (eg 1-η) / η ex (22) 2.5.7 Determination of losses evacuated by Coolers ISSN: 179-595 269 ISBN: 978-96-474-159-5
The value of losses carried cooling air flowing through heat exchangers resulting relationship: P = 4.18 c t Q [kw] (23) where c is the specific heat of air [m ³ / s] given by c =.37 (273 + θ it) H/76 [kcal / m ³ degree] (24) where H is the cooling air pressure [mm Hg column], θ would be out of the cold air temperature rise [ C], t is warmer temperatures m [ C], and Q is the cooling air flow [m ³ / s]. Cooling air flow is determined by the relationship: Q = v m S n [m ³ / s] (25) where: V m is the average air speed [m / s], S is the active area of cooler [M ²], and n is the number of coolers. elements of the generator at rated load is 17 º C for winding the stator, stator core 94 º C to 72 C for winding and rotor when the cooling air temperature is 4 C. If the cooling air temperature is lower temperatures the References: [1] Gheorghiu I.S., Tratat de maşini electrice, Vol.4, Maşina sincronă, Ed. Academiei, 1972. [2] Cioc I., Proiectarea maşinilor electrice, Ed. Didactică şi Pedagogică, 1994. [3] Drăgănescu O., Încercările maşinilor electrice rotative, Ed. Tehnică, 1987. [4] Gavrilă M., Popescu M.C., Maşini şi instalańii hidropneumatice, Tipografia UniversităŃii din Craiova, 1994. [5] Jerve G.K., Încercările maşinilor electrice rotative, Ed. Tehnică, 1972. [6] Popescu M.C., Gavrilă M., Maşini şi instalańii hidropneumatice, Îndrumar de laborator, Reprografia UniversităŃii din Craiova, 1992. [7] Popescu M.C., Maşini şi instalańii hidropneumatice, Îndrumar de proiect, Reprografia UniversităŃii din Craiova, 1993. [8] **** Cartea tehnică a unui hidrogenerator cu puterea de 3,6 MW. Air speed is measured with digital anemometer surface coolers and derived parameters are presented in Table 6. Regim cosφ I ex Z I ex θ ar θ r θ r - A ka Z o C o C o C 1,895 - - 22,8 - - 2,985 53,2,28 2,5 35,2 14,7 3,894 - - 2,5 - - 4,915 555,2,31 21,3 41,1 19,8 Table 5 3 Conclusions Since completion of the work to the following conclusions: - Hydro genitor can operate at rated power factor and rated on a permanent basis, without exceeding the maximum allowable temperature for insulation class of active elements; - Values of temperatures that reach active ISSN: 179-595 27 ISBN: 978-96-474-159-5