1.1 INTRODUCTION
With the development of society, people are more and more dependent on the electric power, the power has gradually become a basic national economic industry, it has a very important role in the development of the whole social economy [1]. Distribution line loss, directly reflects the power supply enterprise management level, reduce the loss of distribution network directly improve the economic efficiency of enterprises. Line loss management, has always been the emphasis and difficulty of line loss management, effectively reduce the power loss of distribution network, line loss management is a long-term goal, but also the power supply enterprise line loss management of large and medium-sized city on [2]. In order to effectively reduce the energy loss, and the main influence factors through in-depth analysis of distribution network line loss, find out the weak link of the power grid, and from the perspective of technology and management of the specific measures to reduce the line loss of distribution network, so as to improve the level of economic operation of grid.
1.2 composition of distribution line loss
In the process of transmission and distribution of electric power, the active power loss and power loss generated by all the components in the power grid are referred to as line losses. In general, the line loss can be divided into technical line loss and management loss [3].
1.2.1 technical line loss
The technical line loss, also known as the theoretical line loss, is based on the parameters of the equipment and the load situation of the network. Technical losses can be divided into 2 categories: variable loss and fixed loss.
1 variable line loss, variable line loss is generally due to the power line of the transformer device in the copper wire and lead, etc., and its power consumption is not fixed, may change at any time.
2) fixed line loss, power loss caused by fixed line loss is the main transformer capacitor device, power meter equipment caused by the loss, the loss and energy in theory is fixed [4].
1.2.2 managed loss
Management line loss is unknown loss, also known as other line loss, mainly due to regulations, work management and other unknown factors in the process of power supply in the run, run, drip, leakage, etc., resulting in power loss. Including customer default electricity, measurement error and business electricity stealing electricity meter, the leakage and other aspects of the omission of copy.
Relationship between 1.2.3 technical line loss, management line loss and actual line loss
After the power supply and power line equipment are determined, the technical line loss is stable in a certain value for a long time. The actual line loss is based on the technical line loss, which is formed by the management line loss.
1.3 causes of line loss
The construction of the national power grid makes the distribution network in our country gradually improved, the coverage area is wider and wider, and the scope of application is more and more big. Line loss management is one of the most common, but also the most critical issue [5], the causes of abnormal line loss are mainly the following points:
1.3.1 circuit design is not reasonable
Due to city planning and city transformation process is unreasonable, often caused by the distribution network has a lot of problems in the circuit design, some areas of the line like a cobweb out of order, sometimes can not tell what the line is for which area, this imperceptibly let energy produced a loss. Moreover, many of the long life of the equipment, has been unable to meet the current demand for electricity, and some may even exist hidden dangers, affecting the distribution network line loss management [6].
1.3.2 three-phase load imbalance caused by high line loss
Increase the power loss of distribution transformer. Distribution transformer is the power supply equipment of low voltage power grid, which will cause the loss of distribution transformer when it is running under the condition of unbalanced three-phase load. Because the power loss of the distribution transformer varies with the unbalance of the load [7].
1.3.3 reactive power compensation and compensation capacity issues
