On the small pumping station and electrical design of environment protection and energy economy

[Abstract] article in accordance with the relevant norms of electrical design of pumping procedures, combined with practical experience in electrical design of proposed pumping station in the small to be considered in all aspects of environment protection and energy and economic balance between different economic and technical programs comparison and analysis of energy saving and cost factors to be considered, to determine the electrical design and equipment selection were analyzed.

[Paper Keywords] small economic environment protection and energy balance station
With the continuous improvement of the level of agricultural modernization, agricultural production and increasing reliance on the use of water conservancy facilities, the Dongting Lake area, the pumping power Paiguan role is especially important.

Small pump station has the following characteristics: close to the irrigation area, irrigation and flexible: Engineering Simple, investment, effective, and the low-pressure unit-based, stand-alone capacity of small, varying the number of installed units, as little as 1 set, more to the more than ten construction funds are mainly dominated by the country to vote, local self-supplemented.

As the degree of local self-financing in place can not guarantee the construction of small and medium sized funds are often stretched station, same time. To improve the economic and social efficiency of pump operation. In the pumping station must be considered green energy, which is often associated with economic Phase contradiction. Therefore, need to seriously consider in the design and affordable green energy balance. The design to meet the economic requirements of environmental protection as far as possible, while energy saving equipment and measures. The following pumping stations designed according to their years of experience. Talk about several aspects of electrical design environment protection and energy balance and reduce the cost of the factors to be considered.

One voltage level to determine
With the completion of rural power grids, electricity supply is now the radius of farmers are generally not large. There are a supply voltage 35kV, 10kV and 0.4kV. Which 0.4kV power supply due to current, the line loss and the use of copper increased significantly, while the 10kV supply voltage can significantly reduce the wear and tear, but also the economy than 35kV power supply, should be preferred. Generally speaking, in order to save investment, the pump station near the 10kV or 35kV line passed. should be received by the T way to obtain power by the system, when there is no line nearby is really necessary or can not meet the requirements set up green when it is considered private from a nearby substation erection of 10kV line.

Determination of the main terminal 2
Based mainly on small pumping station main terminal and running characteristics of the load nature of the decision. Because of the nature of small pumping stations are three loads and loads of smaller capacity, high voltage power supply side of the line generally use simple economic - Transformer Connection: When using two or more transformers to run, they can be a single bus tie line, the choice of transformer turns ratio, impedance voltage, and wiring group should be the same and the same or similar capacity (the capacity ratio should not exceed 3:1), while , ask for circulation to avoid the transformer and load loss caused by uneven distribution of the impact of the transformer, so as not to parallel operation of multiple transformers.

Motor voltage side can be a single bus or a single bus segment form. When the installed base of more days, taking into account the flexibility of operation, the motor bus voltage wiring can be a single bus segment, respectively, then multiple motors and other powered equipment.

3, the choice of major equipment
(1) the choice of distribution transformers.

Choice in the design of power distribution transformers. In addition to fully consider its performance parameters, should be based on electricity load, reasonable choice of transformer capacity, the economic operation of transformer. Not only saving, but also can improve the power factor. In theory, when the transformer load loss in the running when the load loss is equal to the highest efficiency, it is difficult to do in the actual operation. Practice can be the main consideration in the economic operation of transformer to run the best curve or curves in economic operations, and this is the number of transformer units, capacity and performance parameters are closely related.

Has expressly provided the State out of high energy transformers. Promote S9 Series, SIO, S11 series of energy-saving transformer. SIO, S11 and S9 series transformer series were compared: less wear and tear (especially the no-load loss), lower noise, the price difference with the S9 series not, the purchase of S10, S11 series transformer, only to run for 25 years, will be able to return for compensation through energy spread. Therefore, the design should be preferred or S11 Series S10 Series power distribution transformers.

Transformer capacity to select appropriate, neither too large (an increase of one-time investment, increase the loss), nor too small (can not meet the power requirements, losses are often high). Generally speaking, the proper selection of transformer capacity, so that transformer load rate 31 = o. 5 to about 0.6, the minimum active power loss, when the transformer load rate of 13 = 0.75 ~ 0.8, the power factor maximum, when the transformer load rate 13-o. 45 plus. 75 time more efficient, more economical in all aspects, so. Design should try to keep the transformer load rate 31-_o. 45 plus. 8 or so.

Reasonable to determine the number of transformer units. Can take care of both flexibility and economy. When pumping station installed a few more (usually more than 5), the load was unstable and longer intervals. Or low pressure is the main 0.4kV When the transformer capacity of more than 1250kVA (GB50053-94 provides a single main transformer capacity of not more than the general 1250kVA), may consider selecting more than one transformer, to increase the flexibility of operation, low voltage distribution lines to reduce power loss, voltage loss and non-ferrous metal consumption in the pumping unit capacity greater focus and run the load reasonable, or may choose a single large-capacity transformer, small capacity in the pumping station. the case of large load fluctuation can be adjusted by selection of transformer capacity to reduce energy loss.

If funds are limited, can only choose a transformer, it is desirable depending on the time of load operation, according to the maximum load and to consider the longest running time under load so that the transformer is the principle of running the economy the capacity of the transformer, the increase in cost is high. Only determined by the maximum load capacity of the transformer, through the operation of a reasonable schedule to achieve maximum economic operation of the transformer.

Practice often choose two transformers, two sets of equipment to run, then each transformer capacity should be calculated load by 60% -70% of their choices, two transformers each other dark alternative. Assumed the same model pump station for the 8 units, 8 machine running the longest time, the transformer load during normal operation rate of B are as follows:
13 = (40/70)% (40/60)% 57.1% 66.7% a
31 = (10o/140)% ~ (10o, 120)% 71.4% ~ 83-3%
Basically meet the requirements of economic operation. An increase in investment is not large. And. Transformer failure in a case, regardless of ability to overload the transformer will be able to take up the case load of power for most tasks.

(2) motor choice.

Reduce the motor power loss is the main way to improve motor efficiency and power factor. Therefore, the design should be used first in high-efficiency motor Y Series: Second, the electrical voltage level is generally based on unit capacity and the technical and economic comparisons to determine when the unit capacity of less than the selection of low-voltage motor 200kW, 300kW higher than the selection of high-voltage motors, unit capacity (200 ~ 300) kW select low or high pressure when the motor is determined by the technical and economic comparison, and finally, a reasonable choice motor capacity. to the load close to the rated load and leave appropriate margins, then the motor close to the optimum operating point. maximum operating efficiency and power factor.

Choice of structure should focus on the design of the motor are compared: the squirrel-cage motor structure is simple, durable, reliable, easy maintenance, low price, while the winding motor complex, more difficult to maintain, the price is high, but the wound rotor windings can be implemented by then the price level, easy to maintain the frequency sensitive rheostat to improve the starting performance, smooth the motor, starting torque is large, so many small and medium pumping stations are used to improve wound motor starting performance. But around line of squirrel-cage motor prices are a lot of expensive motor, and the use of frequency sensitive rheostat starting power factor is low. With soft start technology matures, prices drop. If the use of squirrel-cage motor pump with soft start mode, but may reduce the cost and improve the starting performance, and power savings. Therefore, in the use of low-voltage induction motor design should be given priority when the squirrel-cage motor (directly or soft-start ), for large-capacity high-voltage motor, the pump should be preferred at low speed synchronous motor to improve power factor.

(3) the choice of conductors and cables.

The size of conductor and cable cross-section, a direct impact on the size of investment and energy consumption: cross-section selection was smaller, non-ferrous metals and reduce the investment in savings, but the energy loss increases, and vice versa, while reducing power consumption, but consumption and non-ferrous metals investments increases. Therefore conductor, the cable cross-section in addition to meet the specification requirements. Should be in investment, consumption and energy loss between non-ferrous metals reached an optimal choice.

Generally based on the load conductor material properties, environmental conditions and economic loss and comprehensive consideration of factors such as choice of copper or aluminum, in the choice of insulation for low voltage cables, for the same cross-section VV YJV series cables are generally more a series of large cable carrying capacity above grade. YJV used in the current larger series cable series cable VV than more economical choice, but also more environmentally friendly. reposted elsewhere in the Research Papers Download http://www.hi138.com (4) switching devices choice.

Switchgear relatively little energy-saving potential, the selector switch in the design of pumping station equipment, mainly from the economic point of view on the reliability and environmental considerations.

High-voltage switchgear can be drop-out fuse, circuit breaker or a combination of electrical appliances. In general, the following criteria to select the economically optimum: For less than 400kVA transformer capacity, the design selection of drop-out fuse. Capacity (400 - 800) kVA transformer within. using common type of load switch - fuse combinations, capacity (800 ~ 1250) kVA transformer within. selection of frequently-type vacuum breaker or load switch - fuse combinations. capacity greater than 1250kVA transformer vacuum circuit breaker is used.

When the outdoor transformer capacity shall be provided in the 800kVA and above the heavy gas trip protection or control request remote operation of the Pumping Station, designed by combined electrical shunt trip should be configured to automatically switch the load to achieve rapid sub-gate, while for overload protection tripping purposes. so when the heavy gas and overload protection the way through the trip without having to load switch fuse burning, with certain technical and economic significance.

Pump voltage circuit breaker should be protected by economic and reliable object based on different principles to choose: the motor should choose an economic and reliable Dwl5 series motor protection circuit breaker: For the main transformer protection of low voltage distribution lines, should choose the sub-capacity High power distribution protection circuit breaker, such as ME, AE, etc., for the small-capacity motors, and other small loads can be used MCCB. As pumping station as a distribution, usually choose the more economical heat Magnetic will be able to meet normal operational requirements, it is not recommended to choose electronic. circuit breaker installation option fixed or drawer, drawer type selection can be canceled due to knife switch, so the economy is not bad.

4 form to determine distribution
Users outside the high-voltage power distribution equipment, or indoor optional equipment. In practice, mainly based on land area and the main substation, vice factory space constraints, consider the economy to determine. No matter what form, must be considered as close as possible to the load center power distribution equipment, to shorten the distribution lines, and reduce line the power loss, voltage loss and non-ferrous metals consumption.

As the boxes become strong with a complete, small, small footprint, can penetrate the load center, improve power quality, reduce line losses, reduce the transmission cycle, site selection flexibility, environmental adaptability, easy installation, safe and reliable operation and less investment and a series of advantages, therefore, after carrying out technical and economic comparison of small and medium voltage power distribution equipment, pumping station could be considered complete outdoor box-type substation.

Low-voltage power distribution equipment within the general mining customers in the form of low voltage switchgear. Since GGD series of low voltage switchgear cabinet with a standardized, inexpensive, safe, reliable, and many other advantages, therefore, for the medium and small pumping stations, the general design can be used GGD series of economic and reliable as a low-voltage switchgear.

5 ways to determine starting
Starting equipment directly start simple, start fast, but great harm: the impact on the power grid caused, to the device pose a threat to safe and reliable operation, shorten its life, while too large starting current will heat the motor windings to accelerate the insulation aging, affecting the motor life and cause great loss of starting power. Especially when frequent starts and stops neatly.

Compared with traditional decompression starting mode, the soft starter to small size, the torque can be adjusted to a smooth start, the impact of small and has the advantages of soft-stop function has been more and more applications. Because no rush current is free to non- level adjusted to the best start-up current, so it is suitable for various pump load.

Three-phase Thyristor soft starter is a new electronic soft starter, relative to the magnetron and automatic liquid resistance soft starter has more superior performance. Relative to the drive with a lower price, with a starting current of small (and may need to set the starting current ratio), the voltage regulator can be the advantages of continuous smooth. When designed with soft start function should be given priority choice is simple, lower price easy to operate, there are several operational status Thyristor Soft starter with voltage ramp start. In addition to achieve soft-start, the variable load conditions in the pump, the motor running at light load, but also has the effect of energy saving light load (without the bypass contactor), the contactor bypass mode can also use a soft starter to start more than one motor, thus greatly reducing the time investment.

Meanwhile, the three-phase thyristor voltage soft starter also has many protection functions: overload protection, phase protection, overtemperature protection and other functions, eliminates the need for thermal relays and other equipment, can read the motor's operating parameters , which can reduce the sensors and instrumentation, it also significantly reduces costs.

In summary, for the squirrel-cage induction motor, when the lower capacity of the units to meet the requirements direct starting, full voltage can be used directly to start, when the request does not meet the direct starting. Priority three-phase thyristor soft starter soft start voltage: For wound rotor induction motor circuit preferred way to start the string frequency sensitive rheostat for the synchronous motor is usually a direct start.

6 reactive power compensation and other
Improve the power factor to reduce energy loss and improve the quality of power supply is of great significance. In general, through a reasonable selection of equipment to improve the natural power factor to achieve, can not meet the requirements or the costs too high, must be reactive compensation, improve the load and power factor, reduce equipment capacity and power loss, voltage stability, improve the quality of power supply.

In addition, the speed and flow is proportional to the power and flow rate proportional to the cube, when the pump flow rate decreases, the power of the cube by a substantial decline in traffic, the use of soft start the motor speed control mode with the combination of methods can further reduce power consumption : lighting the way in the pumping station and equipment selection, using the general lighting and enhance the lighting combination, mature and affordable selection of high light efficiency, long life, good color rendering light source, lamps and ballasts (fluorescent or compact T5, T8 fluorescent lamps, large areas using high-pressure sodium lamps and metal halide), also on the energy balance and economy.

At the same time. Reasonable choice of control and protection and other equipment, the use of AC operating power supply (with UPS), at the same time meet the performance requirements pump can save cost, so in the selection of saving products have greater room for maneuver. Reposted elsewhere in the Research Papers Download http://www.hi138.com