Discussion on the configuration of metering and re

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Discussion on the configuration of metering and reactive power compensation devices for well irrigation distribution transformer

Abstract: most of the distribution devices of rural well irrigation distribution transformer have been out of repair for a long time, and lack of reactive power compensation equipment. Therefore, optimizing the configuration mode of rural well irrigation distribution transformer metering and reactive power compensation devices, and making this technology widely used, will have a significant effect on rural power distribution loss reduction and energy saving, and improving the safety and economic benefits of rural power customers

key words: reactive power compensation of distribution transformer 1 introduction there are 13151 sets of 806000 KVA special distribution transformers for well irrigation in rural power distribution in Yuncheng City. The property rights of these equipment basically belong to users. Most of their distribution equipment have been in disrepair for a long time, and lack of reactive power compensation, which is difficult to meet the requirements of rural power management and improving the economic benefits of rural power customers. Rural well irrigation and distribution substation is a relatively stable seasonal load, and its supporting measurement and reactive power compensation equipment transformation should not only meet the relevant provisions of national or power industry standards, but also obtain the maximum economic benefits with a higher performance price ratio. Therefore, the reasonable selection of the metering and reactive power compensation configuration mode of huamaoze well irrigation distribution transformer, chairman of rural Chengdu Jiahao group, and the promotion and application of this technology play an important role in standardizing the management of rural power consumption and improving the safety and economic benefits of rural power distribution. 2 function selection 2.1 automatic switching mode at present, there are roughly three modes of capacitor automatic switching device: contactor switching, thyristor switching, thyristor zero crossing switching and contactor combination mode. It is difficult to control the large impulse current caused by "zero crossing" switching by using the contactor to switch the capacitor, and the contactor contact is easy to be damaged; Using silicon controlled rectifier instead of contactor can make the switching process without impulse current, but the long-term operation of silicon controlled rectifier causes heating and generates certain harmonics, and its impact resistance is poor, which often causes damage to silicon controlled components; After the thyristor is used to complete the switching process, the contactor can be put into operation. When the system current is small, it can also be used to send the command to switch the compensation capacitor, so as to prevent repeated switching and avoid the thyristor heating and impulse current damaging the contactor contact. This method is an ideal switching mode at present. 2.2 harmonic analysis "harmonic" and "reactive power reverse transmission" should be paid attention to when installing reactive power compensation devices in special distribution transformers for rural distribution well irrigation. Firstly, the capacitor has certain anti harmonic ability, and the excessive harmonic component will affect the service life of the capacitor; Because the capacitor amplifies the harmonic, the harmonic interference of the system is more serious. Therefore, the control link of dynamic reactive power compensation is more vulnerable to harmonic interference and control failure; Secondly, reactive power reverse transmission is not allowed in the power system, because it will increase the losses of lines and transformers and increase the burden of lines. At present, some low-voltage reactive power automatic switching control devices have adopted Fourier transform technology to monitor the great progress made in the implementation of intellectual property strategy, innovation encouragement, achievement protection, information utilization, etc. in recent years. Measure the harmonic content of electricity. Once it exceeds the allowable value, in addition, withdraw from the capacitors that have been switched, so as to ensure that the capacitors will not be damaged when the harmonics are too large. 2.3 main electrical wiring according to statistics, the capacity of rural well irrigation distribution transformer is generally 31 or even can output a constant torque of 5KVA and below. The main electrical wiring of its power distribution device should be as simple as possible to save primary equipment such as air switch, current transformer, lightning arrester, etc. The power distribution device should adopt HR type knife fuse switch as the general short-circuit protection, and the outgoing line should adopt the configuration mode of fuse plus air switch; Low voltage bus adopts lightning arrester as lightning protection or absorbs overvoltage; Use voltmeter and commutation switch to measure the phase and line voltage of three-phase power supply; Use an ammeter to measure the load current; Use the power factor monitoring table to monitor the change of power factor; In order to reduce the circuit loss, the secondary lead of distribution transformer can adopt bundled conductor or cable; See Figure 1 for the main electrical wiring of well irrigation and distribution power transformation and distribution device of 100kVA and above. 1ta, 2ta: 0.2 level current transformer QF: HR knife fuse switch qs: air switch f: lightning arrester 1fu-5fu: fuse C1-C3: parallel compensation capacitor bank JK: capacitor automatic switching controller D: thyristor contactor combined automatic switching device wh: active energy meter varh: reactive energy meter a: ammeter V: voltmeter cos φ: Power factor monitoring table 1hd-4hd, BD: signal light figure 1 electrical main wiring diagram of 100kVA and above well irrigation distribution and distribution device 2.4 electric energy measurement management. About 30% of the metering devices used for Rural Well Irrigation Distribution and cash flow are old models. After the metering meters are replaced with DD862 series, the meter loss will be reduced; Since most of the rural well irrigation distribution transformers are located in the field, it is very difficult to monitor the power consumption. In order to prevent power theft, it is necessary to install glass fiber reinforced plastic or plastic anti stealing boxes on the low-voltage terminals of the distribution transformer, and package the terminals and leads. The trial effect is obvious. 2.5 structure and installation Rural Well Irrigation Distribution and transformer metering and reactive power compensation power distribution devices adopt the box structure installed separately from the distribution and transformer; The shell is divided into ordinary steel plate and stainless steel plate. When made of ordinary steel plate, the thickness shall not be less than 2.0mm, and the surface shall be sprayed with plastic. When made of stainless steel plate, the thickness shall not be less than 1.5mm; The box should be of vertical structure. The electric energy metering device must be set in different boxes. The power distribution device and the metering box door should be equipped with anti-theft locks, and the incoming and outgoing terminals should also be equipped with anti-theft nuts. 3 benefit analysis 3.1 power saving benefit reactive compensation capacity QC value is the reduction value of electric reactive power, and the reduction of line loss caused by it can be calculated by reactive economic equivalent KQ: △ w=qckqh △ w -- annual power saving (kW · h) h -- operating hours qc-- reactive compensation capacity kq-- reactive economic equivalent (kw/kvar), generally choose kq=0.04 ~ 0.08, take the annual operating hours of reactive compensation capacitance as 3000h, kq=0.06, The current rural classified Comprehensive Drainage and irrigation electricity price is 0.32 yuan/kw · h. The annual energy-saving benefits of typical 50KVA and 100kVA well irrigation distribution transformers are calculated in Table 1. Distribution transformer capacity distribution transformer system annual power saving (kw.h) annual power saving benefit (yuan) 50KVA S7, S9 series 540 172.8 100kVA S7, S9 series 7200 23043.2 investment payback period investment payback period T (year) is the ratio of the total investment of reactive power compensation device to the saved electricity charge. Taking 100kVA well irrigation distribution transformer as an example, the price D of reactive power compensation device (with automatic compensation controller) is roughly 18

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