Capacitors in the distribution network on the application of

Reactive power compensation, in the power supply system from the increase in the role of the grid power factor, reactive power compensation can reduce the power supply transformer and transmission line losses, improve power efficiency and improve power supply environment, so the reactive power compensation device Power supply system in a very important and indispensable position to choose a reasonable compensation device can be done to minimize the network losses, improve the quality of the grid. On the contrary, such as selection or improper use may cause Gongdian system, voltage fluctuations, harmonics increases and other factors.

First, the formation of reactive power
AC through pure resistance when the power is turned into heat, but through pure capacitive or purely inductive load, when not acting, that does not consume power, reactive power is, of course, the actual load, not may be pure or purely capacitive load inductive load, are generally mixed load, so that when the current through them, there is some power is not acting, that is, reactive power, power factor is less than 1 at this time, in order to improve energy utilization, it is necessary for reactive power compensation.

Second, the use of reactive power compensation to improve the role of power factor
First, improve the supply of equipment utilization. Apparent power in the power supply device S certain circumstances, the power factor COSΦ the greater the power supply equipment can take more active load (P = S * COSΦ.

Second, to improve transmission efficiency when the power load (P) is constant, because (P = UI * COSΦ, voltage U does not change, COSΦ greater, then the current I the smaller the current I in the loss of the smaller lines.

Third, improve the quality of supply. Current I the smaller the line voltage loss in the smaller end of the line voltage can be better guaranteed.

Fourth, improve transmission security. Current I is small, the line to reduce fever, improve the safety of transmission lines.

Third, the compensation capacity of selected
For the most minute amount of 1500 rpm and 3000 rpm motor with a rated capacity (kW30% disability 0.5 (kvar estimation methods can be quickly and easily find the required compensation capacitor capacity to 30kW motor as the standard, if the motor capacity is less than 30kW each increase 0.5kvar. capacity greater than 30kW of each is reduced 0.5kvar.

General rural distribution network in the capacitance of the fast algorithm:
Motor: Random compensation - Qc = (0.95-0.98 √ 3IoUn
Io - motor excitation current, Un - motor rated voltage.

An ordinary motor for irrigation and drainage: a randomized compensation - Qc = (0.5-0.6Pn
Pn - irrigation motor rated active power.

Fourth, the reactive power compensation with the general approach
Low-voltage reactive power compensation we normally use three main methods: random compensation, compensation and tracking with the compensation device. Following is a brief description of these three methods of compensation for the scope and use of the advantages and disadvantages of the types of compensation.

First, the random compensation compensation is based on individual random electrical equipment requirements for reactive power will be single or multiple low-voltage capacitor spread and connected with electrical equipment, which share a circuit breaker with electrical equipment by control, protection devices and motor while switching randomly compensation applies to compensation for individual high-capacity and continuous operation (such as medium-sized induction motor reactive power consumption, to complement the main reactive excitation. in this way may be better to limit rural network reactive peak load.

Random compensation benefits are: electrical equipment run-time, reactive power compensation input, electrical equipment outage, the compensation equipment out, without causing reactive send down, and do not need frequent adjustments compensate for capacity with less investment, accounting for bit small, easy to install, configure, convenient and flexible, easy maintenance, accident rate and so on.

Second, with the device compensation with the compensation device is a low-voltage capacitor through the low pressure switch will be connected to the secondary side of distribution transformers, distribution transformers with no-load reactive power compensation reactive power compensation. With a change in light or no load reactive power load at the transformer no-load excitation is mainly reactive power, power distribution transformer no-load reactive power load of the rural network is the main part of the light load distribution transformers, this part of the loss is the ratio of total electricity supply large, resulting in an increase in electricity price, electricity is not conducive to the Tongwangtongjia.

With compensated by the advantages: simple wiring, easy maintenance and management, can effectively compensate for distribution transformer no-load reactive power, reactive power limit rural power base-load, so that part of the local balance of reactive power, thereby enhancing the distribution transformer efficiency and reduce non- power network losses, high economy, is commonly used in reactive power compensation means.

Third, the tracking compensation tracking compensation refers to the reactive power compensation switching device as a control and protection devices, low-voltage capacitor compensation in large user 0.4kV bus on the compensation. For more than 100kVA dedicated distribution users can replace random, with the device two kinds of compensation, the compensation effect.

Tracking compensation has the advantage of flexible operation mode, run less maintenance than the first two compensation relatively prolonged life expectancy, more reliable, but the disadvantage is that complex control and protection devices, relatively large initial investment, but when the three compensation way the economy close to, the preference should be given to track compensation.

Fifth, the economic compensation
Compensation effect from the point of view, the compensation current can be decreased after the power 1 / 3 or more, and some even dropped 50%, the Taiwan area can reduce the line loss is basically 2-4 percentage points lower loss can play a better effect. Turn affixed to the free download http://www.hi138.com
In the grid, line or variable transformer power loss is:
P = I2R × 10-3
Assuming a 50kVA transformer, the main load of five 7.5kW three-phase asynchronous motor, the monthly power supply 20000kwh, line loss of 7.2%, after the reactive power compensation of the original power factor cosΦ1 = 0.7, to cosΦ2 = 0.9.

Improve the load power factor and reduce line losses of the relationship:
△ P% = [1 - (cosΦ21/cosΦ22)] × 100%
Where
cosΦ1 - the original load power factor, cosΦ2 - after the power factor compensation
Variable loss reduction:
△ P% = [1 - (cosΦ21/cosΦ22] × 100%
= [1 - (0.49/0.81] × 100%
= 39.51%
Loss of power month: 7.2% × 20000 = 1440kwh
The total loss to reduce electricity consumption: 39.51% × 1440 = 569kwh
Power tariff by 0.63 yuan / kWh, the monthly savings in electricity:
0.63 × 569 = 358.47 元 Links to free download http://www.hi138.com