communication power supply system

 

1. Brief introduction of communication power supply system

 

Communication power supply is an important part of the entire communication system. Just like the heart of the human body, the power supply quality and reliability of power supply equipment will directly affect the entire communication system and its quality.

 

Communication power equipment and facilities mainly include: AC mains lead-in lines, high and low voltage internal power supply and distribution equipment, diesel generator sets, rectifiers, battery packs, DC converters, UPS, and various AC and DC power distribution panels, etc., forming one Complete power supply system, reasonable control, distribution, and transmission to meet the requirements of communication equipment.

 

1.1 Composition and function of high and low voltage power distribution system

 

Generally, the input voltage of the communication enterprise substation is 10KV, so the high-voltage transmission electric energy needs to be reduced to 10KV from 35KV to 220KV to the telecommunications enterprise.

 

High and low voltage power distribution system equipment function: lead high voltage (10KV) into the high voltage incoming cabinet, metering cabinet, lightning protection cabinet, and outgoing cabinet to the high voltage side of the transformer.

 

The role of low-voltage power distribution equipment: the low-voltage side of the transformer enters the low-voltage incoming cabinet through the capacitor compensation cabinet and several outgoing cabinets, and the function is to concentrate and distribute electric energy.

 

Low-voltage (380/220) power distribution cabinet (panel)/low-voltage switch cabinet is a device that connects step-down transformers, low-voltage power supplies, and AC loads. It can complete the conversion between mains and backup power, load splitting, protection, measurement, alarms, etc. Function.

 

1.2 Mains classification

 

■The first type of mains power supply is the introduction of one power supply line from two stable and reliable independent power sources. The two circuits should not have power outages for maintenance at the same time, the average number of power outages per month should not be more than one, and the average time to failure per time should not be more than 0.5h. The two power supply lines should be equipped with automatic standby mains power input devices.

 

■Class II mains power supply lines allow planned maintenance and power outages. The average number of power outages per month should not be more than 3.5, and the average time to failure should not be more than 6h. The power supply shall meet the requirements of one of the following conditions:

 

a. A stable and reliable ring network is formed by two or more independent power supplies and one power supply line is introduced.

 

b. Lead a power supply line from a stable and reliable independent power supply or from a stable and reliable power transmission line.

 

■Three types of mains power supply is the introduction of one power supply line from one power supply. The power supply line is long, there are many users, the average number of power outages per month should not be more than 4.5, and the average time to failure should not be more than 8h.

 

■Four types of mains power supply shall meet the requirements of one of the following conditions:

 

a. One power supply is introduced into one power supply line, and the power is often cut off day and night, the power supply is not guaranteed, and it cannot meet the third-class city power supply requirements.

 

b. There is seasonal long-term power outage or no utility power is available.

 

1.3 Classification of power supply systems

 

1.3.1 DC power supply system

 

The DC power supply system is a power supply system that provides DC (basic) power to the communication bureau (station). According to the latest "General Technical Requirements for Power Supply System of the Communications Bureau (Station)" promulgated by the Ministry of Industry and Information Technology:

 

■－48V and ±24V are DC basic power supply.

 

■ Among them, -48V is the preferred basic power supply.

 

■±24V is the transitional power supply (phased out and no longer used in newly built systems). In practical applications, if ±24V or other DC voltage power supplies are necessary, the -48V basic power supply is generally converted into ±24V or other DC voltage power supplies by means of a DC-DC converter.

 

1.3.2 Centralized power supply system

 

The communication power system is composed of high and low voltage power distribution systems, transformers, low voltage power distribution, diesel generator sets, rectifiers, AC and DC power distribution panels, UPS power supplies, battery packs, converters, and communication equipment power distribution panels.

 

 

1.3.3 Distributed power supply system

 

1.3.4 Hybrid power supply system

 

 

1.4 Introduction to the functions of each part of the power supply system

 

■Substation: 10KV (6KV) is introduced from the city power to the high-voltage power distribution system cabinet (incoming, measuring, outgoing)-transformer (down to 380V) --- low-voltage power distribution cabinet (incoming, compensation, outgoing distribution).

 

■Oil generator set: As a backup power supply for the mains, it outputs 380V AC power to the low-voltage power distribution cabinet through a switch and the mains for switching.

 

■AC power distribution panel: distribute 380/220V AC power.

 

■Rectifier: rectify 380/220V alternating current and transform it into -48V direct current.

 

■DC power distribution panel: Distribute -48V DC power to the DC power distribution panel or DC power equipment of each communication equipment room.

 

■UPS power supply: Provide uninterrupted AC power. Output 220V/380V AC power supply.

 

■Battery: Provide AC and DC backup power supply, provide -48V power supply for rectifier; provide 380/220V power supply for UPS.

 

■DC converter: Convert -48V power supply into DC power supply of different voltage levels required by the equipment, such as: -12V, -24V, +60, -60V, 110V, etc.

2. DC Power Distribution System

 

2.1 Operation mode of DC power supply system

 

The operation mode of the DC power supply system of the exchange office adopts -48V full-float power supply mode. That is, when the mains power is normal, the AC mains is first rectified by the high-frequency switching power supply, and then floats the battery pack and supplies power to the communication equipment;

 

When the mains power (fault) is out of power and the generator set is not started to supply power, the battery pack is discharged to provide DC uninterrupted power supply to the communication equipment, and the allowable discharge time is generally 1 to 2 hours;

 

When the power supply of the generator set or the mains is restored, the DC power supply system is first charged with constant voltage and current limiting, and then switched to the floating charging mode for power supply.

 

The operating mode of the DC power supply system of mobile base stations (or optical cables, microwave relay stations) generally also adopts -48V full-floating power supply. That is, when the mains power is normal, the rectifier module on the combined switching power supply frame is floated in parallel with the battery and supplies power to the communication equipment;

 

When the mains (fault) is out of power and the mobile generator set is not powered, the battery pack is discharged in parallel to supply power to the communication equipment;

 

When the power supply of the generator set or the mains is restored, the DC power supply system is first charged with constant voltage and current limiting, and then switched to the floating charging mode for power supply.

 

2.2 Equipment of DC power supply system

 

The DC power supply equipment in the exchange office mainly consists of a high-frequency switching power supply rectifier and its supporting AC power distribution panel, DC power distribution panel, battery pack, and DC-DC converter.

 

Communication stations such as mobile base stations or optical cables and microwave relays usually use a combined switching power supply that integrates AC power distribution, switching rectifiers, and DC power distribution because the DC load is usually small.

 

2.2.1 Switching power supply

 

1) Switching power supply rack

 

Only the rectifier function does not have the DC power distribution and battery input functions, and the DC screen can form a large-capacity DC power supply system.

 

2) Combined switching power supply

 

The rack has a complete rack including rectification, AC and DC power distribution, battery input, control, etc., and is used for systems with smaller capacity.

 

3) Working principle of switching rectifier

 

 

4) Main features of switching power supply:

 

Light weight and small size.

 

High efficiency (above 90%).

 

High power factor (greater than 0.92).

 

The voltage stabilization accuracy is as high as 0.2%.

 

Low noise.

 

Easy to maintain.

 

Strong reliability.

 

Easy to expand.

 

Easy to debug.

 

It is convenient to realize centralized monitoring and unattended operation.

 

Low requirements for AC input power.

 

High degree of automation.

 

There is high frequency harmonic interference.

 

The control circuit is complicated.

 

2.2.2 AC power distribution panel

 

 

AC power distribution panels used for high-frequency switching rectifiers and other communication electrical equipment, mainly as AC power access and load distribution.

 

With the introduction of two AC power sources, the main and standby power sources can be converted. The circuits that require automatic conversion of the two AC power sources must have reliable mechanical and electrical interlocking.

 

The output load branch can be determined according to the needs of different electrical equipment.

 

For the distribution panel with lighting branch, there should be guaranteed AC lighting branch and DC accident lighting branch, and automatic conversion device.

 

It has over-voltage, under-voltage, and lack of equal warning functions, as well as over-current, lightning protection and other protection functions.

 

The AC screen should be able to provide monitoring quantities that reflect the quality of the power supply and the working status of the AC screen itself, such as three-phase voltage, current value, mains power supply status, main branch output status, etc., and send it to the monitoring module.

 

2.2.3 High frequency switch rectifier frame

 

 

The high-frequency switch rectifier frame is mainly composed of several rectifier modules and monitoring modules to form a single frame.

 

The high-frequency switching rectifier rectifies the AC power introduced from the AC power distribution panel to the DC working power required by the communication equipment. Its output terminal is connected to the DC power distribution panel, and is connected to the battery pack and the communication equipment through the corresponding terminals of the DC panel. Float charging the battery pack and supply power to the communication equipment.

 

2.2.4 Monitoring module

 

It is an intelligent device in the high-frequency switching power supply system, which uniformly manages the operation of the system.

 

This module monitors, controls and manages the operating status of the switch rectifier module, AC and DC power distribution panel and battery in real time through an internal communication interface and according to a predetermined working procedure.

 

It is incorporated into the upper-level monitoring and management system through the RS232/485 external interface, sending and receiving corresponding information, and executing the commands of the monitoring system.

 

The storage of various parameters and operating information is completed. The maintenance personnel adjust the operating parameters on site, and display the operating status and parameters of the system in real time.

 

2.2.5 DC power distribution panel

 

The DC power distribution panel is located between the rectifier and the communication load, and is mainly used for the access of the DC power supply and the distribution of the load, that is, the output of the rectifier, the access of the battery pack and the distribution of the DC load branch.

 

The main functions are:

 

Can be connected to two sets of batteries.

 

The load splitting and capacity can be determined according to the actual needs of the system.

 

It has over-voltage, under-voltage, over-current protection, low-voltage alarm and output surge absorption device.

 

The battery charging and discharging circuit and the main output branch can be monitored.
 

The DC power distribution part used by the mobile base station has low voltage and battery cut-off protection functions.

 

2.2.6 DC power distribution cabinet

 

 

2.2.7 DC-DC converter

 

 

DC-DC converter (DC-DC) is a DC conversion device that transforms basic DC power into other voltage types.

 

At present, the DC basic power supply voltage of communication equipment is specified as -48V. Since there are still -24V (communication equipment) and ±12V, ±5V (integrated circuit) operating power supplies in the communication system, it is necessary to pass the -48V basic power supply The DC-DC converter converts to a DC power supply of the corresponding voltage type for use by various devices.

 

 

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