Energy-saving measures for Power Distribution System Loss Reduction

The distribution network line loss has a great harm. This paper introduces the technical measures for reducing losses and saving energy in the distribution system, and works with the management measures for reducing losses and saving energy in the distribution system. We believe that this can effectively reduce losses and save energy.

Overview

In China's existing power system, voltage-level power transmission and transformation systems above 35 kV are mainly responsible for long-distance power transmission. l0kv and 380/220 V voltage-level power transmission systems are the main bodies of power distribution systems and are most closely related to users. Power loss (active and reactive power) may occur when electric power is transmitted through wires, switches, transformers, and other devices ), and generate energy loss (active and reactive power) in the corresponding time ). The line loss rate of the distribution system refers to the ratio of the loss of active power in the distribution process to the total power obtained by the system within a period of time.

Power loss usually includes two parts: technical power loss and management power loss. Technical line-loss power is the direct loss of power on the transmission equipment during transmission, mainly including power loss in distribution line wires and transformer winding which is proportional to the square of current, also known as load loss; the loss of transformer and the loss of capacitor and Cable Insulation media, the loss of power meter voltage and coil, and the loss of Transformer Core, also known as the loss of no-load. Technical power loss can be reduced by taking corresponding technical measures. The management of power loss is caused by the statistical management of metering, including the comprehensive error of various electric meters, error copying, missed copying and calculation errors, and equipment leakage; the organization and management measures are required to avoid and reduce power loss caused by non-Table electricity usage and electricity theft.

1
Hazards of distribution network line loss

1.1
Fever is the most prominent problem caused by Line Loss

The heating process is the process of converting electric energy into thermal energy, resulting in the loss of electric energy. The heating causes the conductor temperature to rise, and promotes the accelerated aging of insulation materials, shortening the service life, reducing the degree of insulation, and causing thermal breakdown, this will lead to power distribution system accidents. For example, the lifetime reduction rate of Transformer Insulation Material at 140 ℃ and 128 T will be times that of conventional operating temperature (98 ℃. In particular, when the capacity of power distribution lines in a building is insufficient, heating is often the direct cause of electrical fire.

Heating has the most obvious influence on the contact part. Many faults in the distribution network are caused by the resistance fever at the contact. In general, the contact resistance at the contact point is often greater than the resistance of the material at both ends. Even under normal load current, serious fever may occur, which increases the contact resistance of the conductor and produces a vicious circle, eventually, the contact is burned out, causing a fault. The combination of the crimping position of the overhead line and the middle joint of the power cable is often a frequent accident.

1.2
The line loss of the power distribution system results in a great waste of energy.

The line loss of the power distribution system is not converted into useful energy and is wasted. In addition, energy is also required to distribute heat by means of ventilation and cooling. According to statistics, the general distribution network line loss rate is between 3% TB and TB ~ 2. Serious cases may reach 10% or even higher. This not only means the loss of power, but also represents a large waste of energy and more pollution to the environment. Therefore, the economic loss caused by the line loss of the distribution system is reflected in all aspects of power generation, supply and use. If no measures are taken to reduce the Line Loss Rate of the power distribution system, it will inevitably have a negative impact on the national energy utilization, environmental protection, and the economic benefits of enterprises. As the power demand continues to grow, power loss will also increase. Each power enterprise must start from the overall situation and reduce line losses technically and in management.

2
Technical measures for reducing loss and saving energy of power distribution system

2.1
Proper use of Transformer

The flexible cabling mode should be selected based on the electricity usage characteristics of the production enterprises, and the load adjustment can be carried out in a timely manner with the load rate of each transformer to ensure that the transformer runs in the optimal load status. The three-phase load of the transformer is balanced. unbalanced operation not only reduces the output, but also increases the loss. Energy-saving transformers should be used, such as amorphous alloy transformer. The no-load loss of the S9 series is only 25% ~ 30%, suitable for places with low annual utilization hours of transformer.

2.2
Pay attention to and make reasonable compensation for Reactive Power

The active transformer consumes several to dozens of times the active power. The transmission of reactive power in the power grid causes a large amount of active power loss. In a general distribution network, reactive power compensation is installed in the transformer's low-voltage 0.9 V system. It is generally considered that compensation for the load power factor to 0.95-is in place, the reactive compensation for transformer is ignored, that is, compensation for l0kv High Voltage Side.

Reasonable Selection of reactive power compensation methods, compensation points and compensation capacity can effectively stabilize the system voltage level and avoid active network losses caused by a large amount of Reactive Power Transmission over long distances. Capacitor Reactive Compensation for the distribution network is usually concentrated, distributed, and local; the automatic capacitor switching mode can be divided by bus voltage, reactive power direction, power factor, load current size, and day and night time, the specific selection should be determined based on the characteristics of the load electric usage and pay attention to the following issues:

(1)
Single-phase Reactive Power Compensation or automatic phase-based reactive power compensation should be taken into account for a large proportion of single-phase loads in high-rise buildings or residential gathering areas, in order to avoid other two-phase over-compensation or under-compensation when reactive power compensation is made by the one-phase sampling signal, this will increase the loss of the distribution network and will not achieve the purpose of compensation.

(2)
After the parallel capacitor is installed, the harmonic impedance of the system changes, which will play a amplification effect on the harmonic of a specific frequency. This will not only affect the life of the capacitor, but also cause more serious harmonic interference. Therefore, when there is a large Harmonic Interference and the reactive power needs to be compensated, a filter device should be added.

2.3
Rebuild the low-voltage distribution line to expand the current loading level of the wire

Based on the selection principle of the wire section, the minimum cross-section wire meeting the requirements can be determined. However, in the long run, the selection of the minimum cross-section wire is not economical. If the theoretical minimum cross-section wire is added to the first to second grades, the cost saved by the decrease in line loss can be fully recovered within a short period of time. Active Power Loss of wires:

Px = 3ijsr0l × 10-6 (kW)

Formula: IJS-computing current,;

R0-wire resistance, 12/km;

L-wire length, M.

After the wire section is increased, the line loss decreases:

△Px = 3ijs △r0l × 10-6 (kW)

△Wx = 3ijs △r0lt × 10-6 (kWh)

Formula medium: △px-loss active power loss reduction value, kW;

△Wx-the value of reducing active power loss of the line, kWh;

△R0-line resistance reduction value, 12/km;

T-line operation hours, H.

When the hourly price is set to B yuan, the price of the two adjacent section cables is different from that of the E Yuan per meter. After the cross section is increased, the cost of the reduced Line Loss m and the investment of the increased line N are respectively:

M = △wx × B (yuan)

N = E × L (yuan)

If M = N, the cost savings are equal to the increase in investment:

T = E/3ijs △r0b × 10-6 (h)

Assuming that the VV22-0.6/lkv four-core cable is buried, the calculation current is the corresponding load flow when the ambient temperature is 30 ℃, and the power-saving effect after the cross section is increased is shown in the following table:

The above calculation only takes into account the active power loss of the line, and does not take into account the effect of the decrease in temperature after the Section increases. When the cross section is increased, the line reactive power loss will also decrease.

Because the service life of the wire is generally over 10 years, the economic benefits of increasing the energy saving and Loss Reduction of the cross section are very significant.

2.4
Reduce contact quantity and Contact Resistance

In the power distribution system, the connections between conductors are common and the number of connection points is large, which is not only a weak link in the system, but also an important factor that causes the increase of line loss. Attention must be paid to the construction technology of lap joints to ensure close contact with the conductor, and anti-falling agents can be used to reduce the contact resistance in a small way. Pay special attention to the overlap between different materials.

2.5
Energy-saving lighting appliances

According to statistics, lighting in developed countries accounts for more than 10% of total power consumption. With the continuous improvement of living conditions and the gradual improvement of lighting requirements in public places, the ratio of lighting power consumption increases year by year. Light sources can be reasonably arranged based on architectural layout and lighting locations, and lighting methods and types can be selected as an effective method to reduce loss and save energy. For example, the luminous flux of a 20w electronic energy-saving Lamp is equivalent to that of a 100w incandescent lamp. Promote efficient and energy-saving electric light sources, replace inductance Ballasts with electronic ballasts, and replace electronic splitters, delayed switches, optical control switches, sound control switches, and inductive switches to replace the seesaw switches in public places, it will greatly reduce lighting energy consumption and line loss.

2.6
Adjust power usage load to maintain balanced power usage

Adjust the operation modes of power equipment, rationally distribute loads, reduce power consumption during peak periods of the power grid, and increase power consumption during low periods of the power grid; transform the unreasonable local distribution network to maintain a three-phase balance, so that the power consumption of industrial and mining enterprises is balanced, reduce Line Loss.

3
Management measures for reducing loss and saving energy of Distribution System

3.1
Indication Management

The electricity management department should conduct theoretical calculation of Line Loss and compare it with the actual situation to obtain reasonable line loss indicators, the indicators are issued to all grass-roots departments on a yearly, quarterly, and monthly basis and included in the economic responsibility system assessment. In addition, the assessment of small line loss indicators such as the actual electric meter copy rate, voltage pass rate, capacitor rate, capacitor input rate and energy-saving activity should also be carried out. The rewards and punishments should be clearly defined to mobilize the management enthusiasm of employees.

3.2
Reactive Power Management

In addition to normal power factor assessment, some users only care about whether the power factor is greater than 0.9, and do not pay attention to reactive power failover, you can choose to install a two-way Reactive Power Meter for users with high power consumption and power factor close to 1. select a suitable Capacitor switching basis based on the characteristics of electricity usage.

3.3
Harmonic Management

With the increase of non-linear electricity load in the power grid, such as rectifying equipment, Electric Smelting Equipment, electric locomotive, energy-saving appliances, fluorescent lamps, televisions, and computers, harmonic pollution in the power distribution system is becoming increasingly serious. Harmonic not only reduces the power factor of the system, but also produces thermal effects in equipment and lines, resulting in power loss. Therefore, the electricity management department should detect the existence of harmonic waves and the degree of pollution in the system, so as to be aware of it and take harmonic suppression measures when necessary.

3.4
Metering Management

Correct energy measurement is not only the basis for reducing line losses, but also the basis for assessing technical and economic indicators. The power meter should be regularly checked and verified, and the rate should be adjusted in time to reduce the comprehensive error of the energy metering device. The power meter of key parts should adopt advanced full electronic power meter as much as possible, and promote the collection system as much as possible.

3.5
Statistical Analysis

Conduct Line Loss Statistics by partitioning, partitioning, and voltage levels, regularly analyze the current situation of Line Loss, analyze problems in voltage and reactive power work, and propose improvement measures to ensure the completion of line loss indicators. Keep the line loss rate curve for months and years, and master the active power, reactive power flow, power factor, voltage, and line loss of the system, it provides a basis for the next year's load growth, power quality improvement, system economic operation, and the formulation of damage reduction measures.

4
Conclusion

Energy Saving for Power Loss Reduction of distribution networks can not only reduce users' electricity fees, improve economic efficiency of enterprises, but also explore power supply capabilities of distribution equipment, which is extremely beneficial to national energy utilization, environmental protection, and resource optimization. It should be highly valued by the supply and electricity departments. While adopting traditional energy-saving measures to reduce losses, we should increase investment in science and technology to improve the technical level and management level of electricity management.