Keywords:Underground 35kV substation;Security management;Troubleshooting;Institutional building.
Introduction. The 35kV substation in the coal mine is the power supply for the underground coal mine, the office area and the living area of the workers, and all kinds of loads in the mining area depend on the safe and stable operation of the substation. If the substation has misoperation, circuit breaker tripping and other events, it will cause power outages in the corresponding power supply area, and in serious cases, it may also lead to personal accidents of substation operators and underground coal production personnel. This paper summarizes the characteristics of personnel management, system construction, equipment maintenance and anti-misoperation management of 35kV substation, and gives corresponding management suggestions for the current situation of each type, which has a certain effect on reducing electrical misoperation and improving the safety management level of substation.
1.Operational characteristics:
Because the 35kV substation for coal mines is the power supply for coal mining enterprises, there are the following characteristics in the operation process: in terms of personnel, the substation has few personnel on duty and insufficient operation skills;In terms of system, the substation management system is relatively backward and the implementation efficiency is lowIn terms of operating environment, the substation is built near the coal mine, which has the problem of coal dust pollutionIn terms of misoperation, it mainly relies on electrical misoperation. Due to the existence of the above characteristics, the potential dangers of the substation are: the operator's own professional quality or safety awareness leads to misoperation and other event management system defects that lead to long-term potential safety hazards;The equipment failure caused by the long service life of the equipment or the long maintenance period is due to the imperfect electrical anti-misoperation technology, and the operator is prone to misoperation in the case of damage to the electrical components.
2.Personnel management.
The working environment of the underground coal mine substation is relatively remote, and the personnel who have been on duty in the closed environment of the station for a long time are prone to emotional paralysis and decreased sense of responsibility, and are prone to misoperation when encountering operations or accidents. Therefore, the management mode should be changed in the operation and maintenance duty mode, and the current duty mode of 35kV substation is divided into manned duty mode and unmanned duty mode. The duty mode should consider the equipment status and transportation convenience of the substation, and for the substation with a long duty cycle, the rotation cycle should be appropriately shortened to ensure the rest time and emotional stability of the personnel on duty.
The skill level of the personnel on duty in coal mine substations is uneven, and most of the coal mine substations currently in operation are equipped with integrated automation systems, as shown in Figure 1. The integrated automation system can enable the on-duty personnel to monitor the operation status and load of the primary and secondary equipment in the station through the background, and the integrated automation system provides convenience for the on-duty personnel of the substation, and also puts forward new work content and requirements for the on-duty personnel of the substation. The integrated automation system includes the monitoring host, the MCU main control unit, the field bus and all kinds of measurement and control and protection devices, etc., in the substation inspection and inspection and maintenance, we should pay attention to the operation status of the integrated automation device, and maintain and inspect the indicator lights, LCD screens, network cables and monitoring software. For the personnel on duty who are not familiar with the operation of the microcomputer and the operation of the protection device, it is necessary to strengthen the training and increase the sense of responsibility.
Failure analysis and handling.
Due to the influence of factors such as the long production and operation life of coal mines, the expansion of mining scope and the addition and upgrading of underground electrical equipment, the equipment operation of coal mine 35kV substation has the following characteristics: first, the form of electrical main wiring is constantly changing, new intervals and old intervals coexist, and there are also retired equipment;Second, the maintenance and overhaul cycle of the equipment is not fixed, and the implementation efficiency of the overhaul plan is not highThird, there is a problem of coal dust pollution around the operating environment of the equipment, and the aging of the equipment is obvious. In view of the above-mentioned equipment problems, the following equipment maintenance and management suggestions are put forward for the lines, transformers, capacitors and DC devices of 35kV substations in coal mines.
4.1. Power cables.
The line is a bridge between the substation and the coal mine electrical equipment, and the safe and stable operation of the line is directly related to the safety of coal mine electricity, especially the line that goes straight to the underground, and is an important link related to production and personal safety. Substation operators should be familiar with the wiring mode, load situation and cable direction of all outgoing lines in the station, and should pay attention to check whether there are foreign objects hanging on the overhead lines, and should focus on checking whether the cable insulation is intact for the cable lines. In view of the common fault types of power cables, the key points of its work: first, the cable joint with resistance exceeding the normal range at the docking point is covered with a metal shielding layer;The second is to clean up the foreign objects in the cable trench in time, and regularly check the drainage and ventilation, especially in summer to avoid cable failure caused by high temperaturesThird, the new cable concealment project should be strictly accepted to avoid potential safety hazardsFourth, strictly implement the procurement standards of cables, and repeatedly confirm key parameters such as the capacity and length of cables.
4.2. Anti-misoperation management.
Anti-misoperation mainly refers to the five anti-functions of the equipment in the substation, that is, to prevent the inadvertent entry into the live interval, to prevent the accidental pulling and closing of the circuit breaker, to prevent the isolation switch with the ground wire, to prevent the load from pulling and closing the isolation switch, and to prevent the live hanging of the grounding wire. The traditional substation adopts electrical anti-mistaken locking measures, which are generally realized by changing the position of the auxiliary contact of the relay in the electrical secondary circuit. The switch cabinet in the coal mine substation has basic mechanical or electrical locking logic, such as there is a mechanical locking between the position of the circuit breaker trolley and the grounding switch, the circuit breaker trolley is not allowed to pull the grounding switch when it is in the running position, there is an electromagnetic locking between the grounding switch and the rear cabinet door of the switchgear, the grounding switch cannot open the rear cabinet door when it is divided, and the electromagnetic lock can only be opened when the grounding knife switch is closed, so as to open the rear cabinet door. The above anti-error measures are built on the equipment, and there is a risk of damage to the components of the mechanical device and electromagnetic device. Modern substations are generally equipped with microcomputer anti-error systems, as shown in Figure 2.
Through computer keys, electronic code locks, etc., the switches, capacitors, mesh doors, ground wires and other components in the station are locked to prevent misoperation, which can effectively reduce the risk of misoperation. In the management of anti-mistaken locking devices, it is necessary to improve the management system, and when it is really necessary to unlock the operation, it is necessary to perform the corresponding unlocking procedures through the safety management department to avoid unlocking at will.
4.3 capacitors.
A capacitor is a device that provides reactive power to the system, which plays a role in stabilizing the voltage and improving the power factor. The capacitor is prone to joint heating, shell deformation and oil leakage during operation, so it is necessary to pay attention to the appearance of the capacitor during the inspection, and cooperate with infrared temperature measurement to find hidden dangers in time, and the capacitor with the above phenomenon should be immediately stopped and replaced. For the capacitor bank arranged indoors, it is necessary to regularly check the lighting, ventilation and other facilities, and for the capacitor banks arranged outdoors, special attention should be paid to check whether the capacitor mesh door is intact to prevent small animals from entering.
4.4. Voltage transformer.
Frequent faults in voltage transformers include winding burning caused by ferromagnetic resonance, secondary reverse power transmission caused by improper operation, etc. In the normal operation of the power system, the voltage transformer only bears the working voltage, does not pass through the working current, and the design avoids the influence of resonance, so there are fewer defects such as heating. In some special cases, the core of the voltage transformer will be saturated, resulting in the change of the core inductance, when the voltage transformer inductance and the line pair of capacitive reactance are equal or close to the resonance, at this time, it is equivalent to the voltage transformer of the inductive reactance and the line capacitance in parallel on the bus, parallel resonance causes the voltage transformer to bear a large overvoltage, and in serious cases, it will lead to winding heating or even **.
The voltage transformer secondary reverse transmission is when a bus is overhauled, the voltage transformer of the bus is not disconnected for the second time during the power failure operation, and when other voltage transformers form a series circuit with it, the voltage transformer will send power to the bus back, resulting in the risk of electric shock to the maintenance personnel working on the bus or voltage transformer. In order to prevent this situation, one is to take safety measures during the power outage operation, open the secondary air opening, and strictly prohibit closing and power transmission when the maintenance is not completedSecond, when overhauling the knife switch, especially the bus switch, the relay protection personnel should work together with the primary maintenance personnel to ensure that the secondary circuit wiring is correct.
4.5. Main transformer.
The main transformer is the core equipment of the substation, and once it fails, it may directly lead to the loss of power in a large area of the coal mine. During the operation of the transformer, it is important to check the oil level, winding temperature and insulation envelope. In summer, the oil level of the transformer may increase due to high temperature, and in winter, the oil level may decrease due to low temperature or oil leakage. In summer or peak production season, the main transformer may run under high temperature and overload, so it is necessary to strengthen the inspection of the oil level and oil temperature of the main transformer. The main transformer may trip due to heavy gas action or differential protection action, and it is necessary to be familiar with the fault characteristics for tripping in various situations, and formulate the accident handling process and power transmission operation steps in advance.
4.6 DC units.
The DC device of the substation is the power supply for the protection device, control device and lighting, etc., and its safe and stable operation is related to the operation safety of other equipment in the entire substation. The impact of one point grounding of the DC system is not large, but when the system is grounded at two points, it is easy to misoperate or refuse to operate the protection device, resulting in load dumping or the expansion of the fault range. DC devices are prone to DC grounding faults in operation, especially in the rainy season, if the insulation is reduced, the substation operator should check each circuit and deal with it in time to avoid causing greater accidents.
4.7. Vacuum circuit breaker.
The circuit breaker commonly installed in the high-voltage switchgear in the substation is the vacuum circuit breaker, which places the working current in the vacuum bubble for arc extinguishing, which has the advantages of maintenance-free, long life, suitable for frequent operation, small size and light weight. The frequent failures of vacuum circuit breakers mainly include the decline of vacuum bubble arc extinguishing performance, short circuit or open circuit of the opening circuit, and different periods of opening and closing. In operation, because the vacuum level of the vacuum bubble is not constrained by external detection methods, it cannot be detected in time when defects occur, and the fault can only be manifested when the next circuit breaker is operated.
When the vacuum level of the vacuum bubble is reduced, it will lead to a decrease in arc extinguishing performance, which may lead to a circuit breaker** in severe cases. There are two reasons for the vacuum reduction of the vacuum bubble, one is that there is a leakage point in the corrugated tube when it leaves the factory;The second is that the distance between the installation and operation of the connecting rod is too far, which leads to problems such as bounce and overtravel in the operation of the circuit breaker. A faulty opening loop can cause the protection device to fail the fault current, resulting in field equipment burning and tripping. Common causes are burned out of the opening coil, low operating power supply voltage, deformation of the opening rod, etc. The opening and closing of vacuum circuit breakers requires professional testing tools at different stages, and there are few such detection methods in general coal mine substations, so it is difficult to detect them in the early stage.
AcrelCloud-1000 substation operation and maintenance cloud platform.
5.1 Overview.
The cloud management platform developed based on the Internet, big data, mobile communication and other technologies can meet the needs of users or operation and maintenance companies to monitor the operation status and parameters of many substation circuits, indoor environmental temperature and humidity, cable and bus operating temperature, field equipment or environmental video scenes, etc., realize a medium star of data, centralized storage, unified management, easy to use, and support users with permissions to access through various terminal links such as computers, mobile phones, pads, etc. Receive alerts and complete management work related to daily and regular equipment inspections and dispatches.
5.2. Application place.
It is suitable for the new construction, expansion and reconstruction of substation and distribution operation and maintenance systems in telecommunications, finance, transportation, energy, medical and health, culture and sports, education and scientific research, agriculture, forestry and water conservancy, commercial services, public utilities and other industries.
5.3. System structure.
The system can be divided into four layers: the perception layer, the transmission layer, the application layer and the display layer.
Perception layer: including multi-function instruments, temperature and humidity monitoring devices, camera heads, switch acquisition devices, etc. installed in the substation. Except for the camera, other devices are connected to the RS485 port of the field intelligent gateway through the RS485 bus.
Transport layer: includes devices such as on-site intelligent gateways and switches. The intelligent gateway actively collects the data of the field device layer devices, and can perform protocol conversion, data storage, and upload the data to the designated server port through the switch, and the data can be stored locally when the network is faulty, and continue to upload data from the interrupted location when the network is restored to ensure that the data on the server side is not lost.
Application layer: It includes application server and database server, if the number of substations is less than 30, the application server and database server can be configured together. The server needs to have a fixed IP address to receive the data actively transmitted by each smart gateway.
Display layer: Users can access platform information through multiple terminals such as mobile phones, tablets, and computers.
5.4. System functions.
5.4.1. Transformer status.
The transformer status supports users to query the transformer power, load rate, and other operating status data of all or a certain station, and supports ranking in ascending and descending order according to load rate and power.
5.4.2. Site monitoring.
Site monitoring includes overview, operation status, event records of the day, hourly electricity consumption curves of the day, and electricity consumption overview.
5.4.3. Monthly report on energy consumption.
The monthly report of energy consumption allows users to query the electricity consumption of the managed stations according to the total electricity consumption, substation name, substation number, etc., and the query span can be set to month.
5.4.4. O&M.
O&M displays the location and total amount of substation location on the map managed by the current user.
5.4.5 power distribution diagram.
The power distribution diagram displays the power distribution information of the selected substation, and the power distribution diagram displays the operation status and information such as switching status and current of each circuit, and supports the query of detailed operating parameters such as voltage, current, and power.
5.4.6. Video monitoring.
The video monitor displays the current real-time picture (live video), and you can view the video information in the substation by selecting a substation.
5.4.7. Power operation report.
The power operation report displays the real-time value and average value of the specified collection interval of each circuit of the selected station, the selected equipment, the operation parameters and the electric energy meter reading.
Epilogue. The 35kV coal mine substation is the power of the coal mine production, office and living area, and the safe and stable operation is the basic guarantee for coal production, office and workers' lives. This paper summarizes the characteristics of coal mine substations from the aspects of personnel, systems, equipment and anti-misoperation, and gives corresponding management suggestions for each type of characteristics, which is of certain significance for the safe and stable operation of coal mine substations.