Maintenance of intelligent high frequency switchin

Maintenance of intelligent high-frequency switching power supply system in substation

1 overview

the power supply to the secondary circuit of substation is called operating power supply. The operation power supply mainly supplies power to the control, protection, signal and automatic device circuits, and also serves as the accident lighting power supply

traditional operating power supplies include AC operating power supply, silicon rectifier DC operating power supply and battery DC operating power supply. The AC operating power supply is generally only used in small power distribution rooms because the reliability of the relay performing AC operation and the operating mechanism of AC closing of the circuit breaker is lower than that of the DC power supply. Silicon rectifier can reduce the energy consumption of 100 million tons of standard coal. DC operating power supply can only be used in unimportant small substations because it can not solve the problems of emergency lighting and emergency treatment. Battery DC operating power supply has high reliability and is widely used in power system, but its charging equipment has some problems, such as low efficiency, low power factor, large ripple, low battery holding capacity, short service life and so on. At present, the DC power supply equipment used in many substations in China has many shortcomings due to the limitations of the parameters of transformers or thyristors, such as: the initial charging current and floating charging current are unstable, the system ripple voltage is too high, the control characteristics are poor, and it is not convenient to connect with the computer system to realize monitoring; When the charging equipment operates in parallel with the battery, when the ripple coefficient of the floating charge power supply is large and the floating charge voltage fluctuates or is low, the phenomenon of battery pulsating charging and discharging will occur, causing premature damage to the battery pack or monomer; There are also deficiencies such as huge volume, low efficiency, large 1 + 1 redundancy investment, which should be said to be far from meeting the needs of the rapidly developing power industry. It will gradually be characterized by small volume, light weight, high efficiency, small ripple coefficient, fast dynamic response, high control accuracy, module superimposable output The N + 1 redundancy and other special decomposition temperature and gas generation are mainly replaced by the intelligent high-frequency switching power supply system based on the point of selecting chemical foaming agent. The latter organically combines rectifier, voltage regulator, feed out circuit, protection alarm circuit and monitoring system, and effectively solves the defects of the previous DC operation power supply through computer management

the intelligent high-frequency switching power supply system equipped in the substation, including switching rectifier equipment, valve regulated lead-acid maintenance free battery, DC feeder cabinet, etc., although there are not many equipment, it is an important equipment to ensure the stability and continuity of electric power supply. The maintenance of these devices is not only related to the reliability and life of intelligent high-frequency switching power supply system, but also directly related to the smooth operation of electricity. It can be seen that it is very important to maintain and use the intelligent high-frequency switching power supply system

2 basic requirements and precautions

in order to ensure the reliability of the DC power supply system of the substation, if possible, try to introduce AC input power from two different places, and the two AC power supplies have the function of automatic switching; Intelligent and standardized high-frequency switching rectification equipment with high reliability should be selected. In the process of implementation, reliability and practicality should be the basic principles, which should be simple rather than complicated; Adopt modular and hot plug structure to facilitate replacement; Implement centralized monitoring and management, and reasonably configure backup equipment. No new technology or equipment shall enter the power supply system without full verification and trial operation. We should constantly improve the level of maintenance technology and adopt centralized maintenance, remote signaling, telemetry maintenance and other means; It is necessary to often analyze the operating parameters, predict the time and location of the failure, predict the accident, and eliminate the defects in time

intelligent high-frequency switching power supply system equipment has a high degree of intelligence. The battery adopts maintenance free battery, which brings us a lot of convenience, but we should pay attention to the following aspects in the process of use to ensure safety

● the high-frequency switching power supply system does not have high requirements for the ambient temperature. It can work normally at - 5 ~ + 40 ℃, but it requires that the room be clean and less dust. Otherwise, dust and humidity will cause the host to work disorderly. The storage battery has higher requirements for temperature. The standard operating temperature is 25 ℃, and the recommended temperature range is + 15 ~ + 30 ℃. If the temperature is too low, the capacity of the battery will decrease. For every 1 ℃ drop in temperature, the capacity will decrease by 1%; The discharge capacity of the battery will increase with the increase of temperature, but the service life will be reduced. If it is used for a long time under high temperature, the battery life will be reduced by about half for every 10 ℃ increase in temperature

● the parameters set in the high-frequency switching power supply system must be controlled within the specified indicators and cannot be changed arbitrarily in use

● during the use of DC power supply system, it is necessary to avoid adding additional equipment (load) with high power at will, and it is not allowed to operate under full load for a long time. Because the nature of the work determines that the DC operating power supply system operates almost continuously. Increasing the high-power load or working under the basic full load state will cause the rectifier module to fail, which will damage the converter in serious cases

● due to the large output current of the battery pack, there is a risk of electric shock, so special attention should be paid to safety when loading, unloading and changing the conductive connecting strip (line) and output line, and the tools used should be insulated to ensure the safety of personnel and equipment

● ensure that the voltage and current meet the specified requirements no matter in the floating charge working state or in the discharge maintenance test state. Too high voltage or current may cause thermal runaway or water loss of the battery, and too low voltage or current may cause battery power loss, which will affect the service life of the battery, especially the former

● in any case, the battery should be prevented from short circuit or deep discharge, because the cycle life of the battery is related to the discharge depth. The deeper the discharge depth is, the shorter the cycle life is. In capacity test or discharge maintenance, it is usually enough that the discharge reaches 30% - 50% of the capacity

● the battery should avoid large current charging and discharging, otherwise it will cause the expansion and deformation of the battery plate, which will cause the active material of the plate to fall off, the internal resistance of the battery will increase and the temperature will rise, and in serious cases, it will cause the capacity to decline and the service life will be terminated in advance

● valve regulated sealed battery is a lean liquid battery, so it is impossible to measure the specific gravity of electrolyte, so the most reliable method to judge its quality is discharge method at present. It can also use conductivity meter to measure the internal resistance of battery to judge the quality of valve regulated sealed battery, but the accuracy is poor

3 maintenance management

when the intelligent high-frequency switching power supply system fails, you should first find out the cause, and distinguish the load department? Or the power system, the host or the battery pack. Although the host of the switching power supply system has the function of fault self-test, it is opposite but not at the right point, and it is convenient to replace accessories, but a lot of analysis and detection work must be done to repair the fault point. If the self-test part fails, the displayed fault content may also be incorrect

3.1 high frequency switching power supply part

under normal use, the maintenance workload of the host is very small, mainly dust prevention and regular dust removal. Especially in dry areas, there are many dust particles in the air, and the dust will be deposited in the machine (mainly in the rectifier module). When the air is wet, it will cause the host control disorder, cause the host to work abnormally, and give an inaccurate alarm. In addition, a large amount of dust will also cause poor heat dissipation of devices

generally, it should be thoroughly cleaned once a quarter. At the same time, check whether the connectors and connectors are loose and have poor contact when removing dust

regularly verify whether the parameters of the intelligent high-frequency switching power supply system have changed, so as to prevent artificial or unintentional changes to the set parameters

the operation mode of the intelligent high-frequency switching power supply system should be tested and checked every half a year to prevent damage to the battery caused by the failure to switch between the equalizing state and the floating state in time. Faced with many user queries

check whether the host equipment is normal, and ensure that the DC bus often maintains qualified voltage and battery discharge capacity

in case of breakdown, fuse or burned device failure of the host, you must find out the cause and eliminate the failure before restarting, otherwise it will cause more serious failure

3.2 maintenance free battery part

because the interference of rectifier to instantaneous pulse cannot be eliminated, there are still interference pulses in the rectified voltage. In addition to the function of storing DC electric energy, the equivalent capacitance of the battery is directly proportional to the capacity of the battery. Therefore, it is very important to maintain and repair the battery. Although the battery pack currently adopts maintenance free batteries, it only eliminates the previous work of measuring specific gravity, preparing electrolyte and adding distilled water. Due to the working state and abnormal working state, microchip technology, the world's leading supplier of single chip computers and analog semiconductors, launched four 64 and 80 pin pic  flash memory single chip computers. New devices are designed for applications with limited cost and need additional input/output, such as industrial, computing, communication, consumer and other applications. This instrument enters the working record and storage state. The flash memory single chip microcomputer with high quality and low price has 8KB or 16kb program memory and nanowatt technology, which can give full play to the powerful function of power management

designers of embedded control applications have an increasing demand for 8-bit MCU products with more input/output and low power consumption. Microchip's new Pic18F microcontroller has up to 70 pin input/output, 8KB or 16kb flash memory, 768 byte ram and low-power mode of nanowatt technology, which can fully meet the above design needs

in addition to providing highly flexible input/output, the new PIC MCU is also equipped with flash memory with various programming functions. It has the function of reprogramming, which can further accelerate the pace of product launch through shorter development cycle, low-cost simulation and flexible change of function code on site

pic18fxx10 the new input/output will benefit many application fields, including the establishment of security systems, device controllers, video control panels, home automation systems and the application of multiple sensor data acquisition. In addition, the new device has a unique nanowatt technology, which can provide power management mode, and is an ideal solution for battery driven or low-power applications

other main features of the new device include:

● external clock frequency up to 40MHz (10mips)

● internal oscillator frequency range from 32kHz to 32mhz (8mips)

● clock failure monitor

● wide working voltage range: 2.0 ~ 5.5V; Operating temperature range from - 40 ℃ ~ 125 ℃

● in circuitserialprogrammingtm (icsptm)

● 10 bit analog-to-digital converter, with up to 12 channels, sampling rate up to 100k/s

● two analog comparators, with programmable undervoltage detection and programmable low voltage detection functions

● spitm I2ctm and two USARTs (supporting RS485, RS232 and Lin)

● the impact caused by the three capture/compare/pwm module batteries has not changed, so the focus of power system maintenance is still on the battery

the battery operates in floating charge state and is discharged at least once a year. Before discharging, the battery pack should be evenly charged to achieve the balance of the performance of the whole battery. In the process of discharge, if one reaches the discharge termination voltage, it should stop discharging. If it continues to discharge, it must first eliminate the backward battery before discharging

check discharge