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Development of recommendations to support the level of reactive power compensation in electrical networks

Content

Introduction

In modern times become acutely the question of energy savings. For most industrial electrical power is the primary source of energy. So to get the issue of reducing transmission losses and power consumption. In many areas there is a process of development of energy-saving technologies aimed at efficient use of industrial systems and processing plants. The main power consumers in any enterprise are: electric motors and transformers. Their principle of operation is based on the creation of an electromagnetic field, which requires the consumption of reactive power. But does not produce reactive power of useful work, but only leads to an additional load lines, which reduces the power factor, leading to an increase in active power losses due to heat conductors. Also, the presence of reactive power level affects the voltage and power quality, which leads to additional losses in the conductors, increasing the charge power supplier, etc.

1. Relevance of the topic

The relevance of the topic is determined by the need to reduce customer costs by reducing the consumption of reactive power and reduce possible with compensating devices - correction systems, synchronous condensers, STK - which are installed on the tires low voltage substation consumer. These devices can reduce the cost for the consumption of reactive power and voltage increase tire substation.

2. The scientific importance

The cost of electricity is a significant part of the cost of production. Therefore, reactive power compensation, which will reduce energy losses and reduce the company's costs for its consumption, has expediency and is one of the priorities in the development of energy-saving technologies

3. Modern reactive power compensation devices

To improve energy efficiency need to use more fuel-efficient ways of generation, transmission and consumption. Exceptions are the factors leading to the emergence of losses, will lead to a more rational use of electrical systems. One solution to this problem is to increase the power factor. Is most effective at compensating devices connected as close as possible to the inductive load.

The most promising means of reactive power compensation active-inductive loads are cosine capacitors and capacitor banks (CS). Condensing units are widely used in network and power supply systems and industrial enterprises of power virtually all levels not only in the form of individual, group and centralized power factor correction (PM), as well as baluns, filters, combined (symmetry-balancing, filtering and baluns, etc. etc.) devices, capacitive transducers parameters of electric power, etc. In general, the state of CG medium voltage in Ukraine, can be described as deplorable: mostly unregulated KU, without proper protective equipment (reactors and so on.), Often with environmentally harmful capacitors (impregnated trichlorodiphenyl), produced until the mid 80's . requiring immediate replacement and special disposal. The task of the introduction of modern high-efficiency CHP is becoming more urgent.

European manufacturers of condensing units have achieved a high level and can offer a capacitor-frequency power reaches 1MVar with nominal voltages up to 24kV.

Schemes switching capacitors in the star used in installations with a continuously variable PM (containing a thyristor controlled reactors) and filtrokompensiruschih devices comprising one or several chains of series-connected capacitors and reactors of filter tuned to the specific frequency of the higher harmonic components. These settings allow for simultaneous compensation of RM, partial suppression present in compensated networks harmonics that distort the sinusoidal voltage and other functions. KU single-phase adjustable choke dekompensiruyuschim applied on voltage 27 kV (for railways). KU series compensation capacitors can be manufactured with high overload capabilities. Three-phase and cosine filter capacitors usually issued up to a voltage of 12 kV. In automatic KU with a rated voltage of 12.6 kV often use a stepwise inclusion of three-phase capacitors, although in some cases more effective is the inclusion of single-phase capacitors in the star. Switching levels KU, usually produced by vacuum contactors. To reduce the inrush current during switching launchers used (damping) Reactors (English - inrush reactors), commercially available from 0.05-0.1 mH inductors for nominal currents of capacitors 50-200 A.

In an increasing number of cases, the use of CG in a degraded the quality of electricity in accordance with GOST 13109-97 are commonly used:

  • Capacitors with non-nominal voltages (eg 6.6 and 11 kV instead of 6.3 and 10.5 kV) to work in a positive (higher than nominal) voltage variations,

  • Antiresonance inductors (also called "detyuningovymi" - Engl. - Detuned reactors) with coefficients often detuning (the same: the error / sedation) 7 and 14% (corresponding to the resonant frequency "choke-capacitor" 189 and 134 Hz) for reduce the capacitor overload currents of higher harmonic components

  • Controllers and other safety devices, controlling the respective capacitor overload, surge suppressors, etc.

  • In the case of substantial non-sinusoidal voltage applied additionally customized filtering devices.

    In today's security systems KU, working in conditions of deviations and non-sinusoidal voltage devices are used (blocks) control:

  • The overpressure inside the condenser as a corresponding sensor that is installed in the capacitor casing,

  • state of the external fuse to avoid asymmetrical modes, such as through the use of special holders with display and alarm response,

  • THD (waveform distortion), the voltage (THDU) and current (THDІ), including overload selected harmonic components,

  • The amount of equity and current KU input voltage for the devices CU tripping in case of exceeding the maximum allowable voltage and current values of capacitors,

  • Voltage vacuum contactors coils for protection against dangerous regime neustroychivogo contact (contact bounce) at low voltage, temperature capacitors and / or the interior of the CC,

  • current imbalance is a scheme with the inclusion of single-phase capacitors in more than one star (for protection operation from the appearance of the asymmetry of capacity in the branches of KU).

    • For registration and the proper functioning of the protection KU commonly used flexible devices at the same time asking for all of the control functions. At the same time, partial control can perform both individual devices and modern regulators capacity KU. Last, commonly called "power factor controllers", including can control how THDU, and THDІ, as well as individual harmonic components of domestic current KU (with such adjustments are respectively two inputs for measuring circuits). Regulators are also applied without control of its own current KU, calculating overcurrent corresponding level of regulation largest THDU. In the case of considering the simultaneous exposure to the elements KU several indicators of the quality of electricity in the protection device or controller KU important to have the possibility of correcting the maximum current value: for example, reduced voltage can be tolerated somewhat too high overload currents harmonic elements, etc. It should be noted that the sensitivity current regulator has reached the 2 mA. Electrical Market in Ukraine, especially in recent times, brimming with new modifications of regulators, differing not only the components and functions, but also new approaches to the construction of the control algorithms. In most cases, conventional regulators based algorithm is to regulate the magnitude and sign of RM, which is usually determined by the current of one phase and a line voltage between the other two phases of three-phase network. In the case of unbalance voltage / current, current transformers, as is generally done in phase with minimal current (in order to avoid overcompensation mode in the other phases), although this appears appropriate underdosing RM. To compensate for the RM significantly asymmetric modes should be used single-ended circuits KU, including circuit consisting of three groups of single-phase capacitors of different capacities, which are governed by special algorithms special types of regulators [1,2].

    4. A review of research and development on the subject.

     

    Method of calculating the optimum power compensation systems mimnimum terms of reduced costs [3,4,5].

    The calculation for the SS "Commune".

    Where Зmin the minimum cost;

    Ен – the coefficient of the economic efficiency of capital investments, taking 0.25;

    Кку и КВ – the cost of KU and switches, respectively

    Иconst – fixed costs;

    Иvar – variable costs;

    П – charge for reactive power flows..

    According to the daily (winter and summer) load schedule PS "commune" is determined daily fee of RM flows at different power ratings KU.

    Table 1 - The daily fee for reactive power flows in the winter for T1

    SS Qky, MVar*h 7-22 h. с 23-6 h. Wp, MW*h tgϕ Kϕ П1, thnd.grn П2, thnd.grn П, thnd.grn ΣПw
    WQ п, MVar*h WQ ген, MVar*h WQ п, MVar*h WQ ген, MVar*h
    Communa

    		0,9 0 3,43 0 2,9 26,6 -0,24 1 0,17748 0 0,17748 37,8
    0,75 0 1,18 0 1,55 26,6 -0,10 1 0,09486 0 0,09486 20,2
    0,6 3,32 0 1,18 0,03 26,6 0,17 1 0,093636 0 0,093636 19,9
    0,45 6,81 0 2,59 0 26,6 0,35 1,01 0,19176 0,001918 0,193678 41,3
    0,3 5,57 0 2,54 0 26,6 0,30 1,0025 0,165444 0,000414 0,165858 35,3
    0,15 7,82 0 3,85 0 26,6 0,44 1,0361 0,238068 0,008594 0,246662 52,5
    0 10,07 0 5,2 0 26,6 0,57 1,1024 0,311508 0,031898 0,343406 73,1












    Table 2 - The daily fee for reactive power flows in the summer for T1

    SS Qky, MVar*h 7-22 h. с 23-6 h. Wp, MW*h tgϕ Kϕ П1, thnd.grn П2, thnd.grn П, thnd.grn ΣПw
    WQ п, MVar*h WQ ген, MVar*h WQ п, MVar*h WQ ген, MVar*h
    Communa

    		0,9 1,14 1,51 0,43 1,91 29,9 -0,06 1 0,14892 0 0,14892 22,63584
    0,75 2,49 0,61 0,88 1,01 29,9 0,06 1 0,13056 0 0,13056 19,84512
    0,6 4,13 0 1,33 0,11 29,9 0,18 1 0,118116 0 0,118116 17,95363
    0,45 6,38 0 2,57 0 29,9 0,30 1,0025 0,18258 0,000456 0,183036 27,82154
    0,3 8,63 0 3,92 0 29,9 0,42 1,0289 0,25602 0,007399 0,263419 40,03968
    0,15 10,88 0 5,27 0 29,9 0,54 1,0841 0,32946 0,027708 0,357168 54,28947
    0 13,13 0 6,62 0 29,9 0,66 1,1681 0,4029 0,067727 0,470627 71,53538














    Table 3 - The daily fee for reactive power flows in the winter for T2



    SS Qky, MVar*h 7-22 h. с 23-6 h. Wp, MW*h tgϕ Kϕ П1, thnd.grn П2, thnd.grn П, thnd.grn ΣПw
    WQ п, MVar*h WQ ген, MVar*h WQ п, MVar*h WQ ген, MVar*h
    Communa 0,9 1,35 0,3 2,16 0,06 65,9 0,05 1 0,075276 0 0,075276 16,03
    0,75 3,48 0,03 3,45 0 65,9 0,10 1 0,141372 0 0,141372 30,11
    0,6 5,73 0 4,8 0 65,9 0,16 1 0,214812 0 0,214812 45,75
    0,45 7,98 0 6,15 0 65,9 0,21 1 0,288252 0 0,288252 61,40
    0,3 10,23 0 7,5 0 65,9 0,27 1,0004 0,361692 0,000145 0,361837 77,07
    0,15 12,42 0 8,85 0 65,9 0,32 1,0169 0,433908 0,007333 0,441241 93,98
    0 14,73 0 10,2 0 65,9 0,38 1,1225 0,508572 0,0623 0,570872 121,60



    Table 4 - The daily fee for reactive power flows in the summer for T2

    SS Qky, MVar*h 7-22 h. с 23-6 h. Wp, MW*h tgϕ Kϕ П1, thnd.grn П2, thnd.grn П, thnd.grn ΣПw
    WQ п, MVar*h WQ ген, MVar*h WQ п, MVar*h WQ ген, MVar*h
    Communa

    		0,9 0 3,89 0,5 2,15 24,7 -0,22 1 0,14178 0 0,14178 21,6
    0,75 0,18 1,06 0,7 0,55 24,7 -0,03 1 0,051612 0 0,051612 7,8
    0,6 1,06 0,44 1,06 0 24,7 0,07 1 0,043248 0 0,043248 6,6
    0,45 3,16 0,29 2,41 0 24,7 0,21 1 0,113628 0 0,113628 17,3
    0,3 5,26 0,14 3,76 0 24,7 0,36 1,0121 0,184008 0,002226 0,186234 28,3
    0,15 7,36 0 5,11 0 24,7 0,50 1,0625 0,254388 0,015899 0,270287 41,1
    0 9,61 0 6,46 0 24,7 0,65 1,16 0,327828 0,052452 0,38028 57,8





    The calculation of variable costs, is charge power losses in the system. Taking into account only the loss in transformers substations.

    Annual electricity losses calculated by the formula:

    где - losses in the windings of the transformer,

    ΔРст – iron loss transformer.

    Number of hours of maximum losses τm defined by the formula:

    where Тм – the number of hours of use of the maximum load.

    The value of Tm is determined from the annual electricity consumption

    где Рmax – maximum power.

    For the conditions of the Donbass accepted that the number of winter days in a year is 213 days, and the summer - 152, then [6,7]:

    The value of Tm and τm Transformer Substation "The Commune" is shown in the Table. 5

    Table 5 - Results of calculating Tm and τm

    Тр-р

    Daily consumption of e / p, MWh

    Wyear, MWh

    Рмax, MWh

    Тм, h

    τм, h


    Winter

    Summer





    Т1

    26,6

    29,9

    10210,6

    2,08

    4908,9

    3312,1

    Т2

    65,9

    24,7

    17791,1

    3,76

    4731,7

    3123,9



    The results of calculation of annual energy losses are given in Tables 6 and 7.

    Table 6 - Annual electricity losses for T1.
    Qky Pmax Qmax S, MWh dPмd, kWh dWt, MWh Иvar, thnd.
    0,9 2,08 1,09 2,09 1,544 120,68 82,1
    0,75 2,08 1,09 2,11 1,572 120,82 82,2
    0,6 2,08 1,09 2,14 1,617 121,04 82,3
    0,45 2,08 1,09 2,18 1,677 121,33 82,5
    0,3 2,08 1,09 2,22 1,752 121,70 82,8
    0,15 2,08 1,09 2,28 1,844 122,15 83,1
    0 2,08 1,09 2,35 1,952 122,68 83,4



    Table 7 - Annual electricity losses for T2
    Qky Pmax Qmax S, MWA dPмд, kW dWt, MWh Иvar, thnd.
    0,9 3,76 1,09 3,76 3,60 130,13 88,5
    0,75 3,76 1,09 3,78 3,62 130,23 88,6
    0,6 3,76 1,09 3,79 3,65 130,38 88,7
    0,45 3,76 1,09 3,81 3,69 130,58 88,8
    0,3 3,76 1,09 3,84 3,75 130,84 89,0
    0,15 3,76 1,09 3,88 3,82 131,15 89,2
    0 3,76 1,09 3,91 3,89 131,52 89,4



    Results costing 3 are shown in Table 8 and 9.

    Table 8 - Results of calculation for T1
    .
    Qky Kky Kв Иconst Иvar П 3
    0,9 50,032 32 11,81261 82,06308 60,43908 174,8228
    0,75 62,606 64 18,23126 82,15703 40,0503 172,0901
    0,6 56,376 64 17,33414 82,30414 37,8981 167,6304
    0,45 34,418 32 9,564192 82,50444 69,07487 177,748
    0,3 28,188 32 8,667072 82,75791 75,36736 181,8393
    0,15 21,196 32 7,660224 83,06456 106,8285 210,8523
    0 0 0 0 83,42438 144,6809 228,1053



    Table 9 - Results of calculation for the S T2.
    Qky Kky Kв Иconst Иvar П 3
    0,9 50,032 32 11,81261 88,49153 37,58 158,3965
    0,75 62,606 64 18,23126 88,5565 37,96 176,3965
    0,6 56,376 64 17,33414 88,65825 52,33 188,415
    0,45 34,418 32 9,564192 88,79677 78,67 193,6346
    0,3 28,188 32 8,667072 88,97207 105,38 218,065
    0,15 21,196 32 7,660224 89,18415 135,07 245,2114
    0 0 0 0 89,433 179,40 268,8314



    Construct the dependence of costs on the power W KU.

    Figure1 - Relation 3(Qbk) for T1(number of frames 5 dalay time 10s, size 9kB)

    Figure 1 -Relation

    3 (Qbk) for T1(number of frames 5 dalay time 10s, size 9kB)

    Figure2 - Relation 3(Qbk) for T2

    Figure 2 Relation
    3 (Qbk) for T1

    From figure it can be concluded that the optimum power for KU is Qbk T1 = 0.6 Mvar.



    5.The final part

    The novelty of this work lies in a comprehensive approach to solving the problem of reactive power compensation. The technique and the program will select the optimal use of capacitor banks. Thus, when considering the level of cost KU, installation is economically feasible. Further research is necessary to determine the optimal amount of regulatory effectiveness ratio, the rules on maintenance payments KU, the cost of electricity consumed.

    On the moment of writing this abstract the master's work was not completed. Its final variant can be obtained from the author or the scientific adviser after December 2013.

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