Power distribution cabinets are divided into power distribution cabinets (boxes), lighting distribution cabinets (boxes), and metering cabinets (boxes), which are the final equipment of the power distribution system. The power distribution cabinet is a general term for the motor control center. The power distribution cabinet is used in the occasions where the load is relatively scattered and there are few circuits; the motor control center is used in the occasions where the load is concentrated and there are many circuits. They distribute the electric energy of a certain circuit of the upper-level power distribution equipment to the nearest load. This level of equipment shall provide protection, monitoring and control of the load.
1. Definition of power distribution cabinet
Respectively refer to power distribution cabinets, lighting distribution cabinets, metering cabinets and other final equipment of the power distribution system.
2. Classification of power distribution cabinets
2.1 The first-level power distribution equipment is collectively referred to as the power distribution center. They are centrally installed in the substation of the enterprise, and distribute the electric energy to the lower-level power distribution equipment in different locations. This level of equipment is close to the step-down transformer, so the requirements for electrical parameters are relatively high, and the output circuit capacity is also relatively large.
2.2 Secondary power distribution equipment is a general term for power distribution cabinets and motor control centers. The power distribution cabinet is used in the occasions where the load is scattered and there are few circuits; the motor control center is used in the occasions where the load is concentrated and there are many circuits. They distribute the electric energy of a certain circuit of the upper-level power distribution equipment to the nearest load. This level of equipment shall provide protection, monitoring and control of the load.
2.3 The final power distribution equipment is collectively referred to as the lighting power distribution box. They are far away from the power supply center and are scattered small-capacity power distribution equipment.
3. Commonly used power distribution cabinets
3.1 Main switchgear types:
Low-voltage switchgear includes GGD, GCK, GCS, MNS, XLL2 low-voltage distribution boxes and XGM low-voltage lighting boxes.
3.2 Main differences:
GGD is a fixed type, and GCK, GCS, MNS are chests of drawers. GCK and GCS, MNS cabinet drawer push mechanism is different;
The main difference between GCS and MNS cabinets is that the GCS cabinet can only be used as a single-sided operation cabinet with a depth of 800mm, while the MNS cabinet can be used as a double-sided operation cabinet with a depth of 1000mm.
3.3 Advantages and disadvantages:
Withdrawable cabinets (GCK, GCS, MNS) save space, are easy to maintain, have many outgoing lines, but are expensive;
Compared with the fixed cabinet (GGD), it has fewer outlet circuits and occupies a larger area (if the space is too small to make a fixed cabinet, it is recommended to use a drawer cabinet).
4. Installation of power distribution cabinet
The installation requirements of the distribution board (box) are: the distribution board (box) should be made of non-combustible materials; the production site and office with a small risk of electric shock can be installed with an open distribution board; Closed cabinets should be installed in poor processing workshops, casting, forging, heat treatment, boiler rooms, carpentry rooms, etc.; closed or explosion-proof cabinets must be installed in dangerous workplaces with conductive dust or flammable and explosive gases. The electrical facilities; the electrical components, instruments, switches and lines of the distribution board (box) should be arranged neatly, installed firmly, and easy to operate.
The bottom surface of the board (box) installed on the floor should be 5~10 mm above the ground; the center height of the operating handle is generally 1.2~1.5m; there are no obstacles within 0.8~1.2m in front of the board (box); the protection line is connected reliably; There shall be no bare electric body exposed outside the (box); the electrical components that must be installed on the outer surface of the board (box) or on the distribution board must have reliable screen protection.
5. Operation of power distribution cabinet
The electrical components and lines in the distribution board (box) should be in good contact and reliable; there must be no serious heating or burning. The door of the switchboard (box) should be in good condition; the door lock should be kept by a special person.
The circuit diagram of the distribution board is divided into a primary schematic diagram and a secondary schematic diagram, and the primary schematic diagram is the main circuit schematic diagram. The secondary schematic diagram is the schematic diagram of the control circuit.
Compared with the previous power distribution cabinets, the intelligent integrated power distribution cabinet has made great improvements! It is a technological innovation!
In view of the current situation that the power distribution in the computer room is prone to single point failure, it integrates the most advanced technological achievements and hardware and software design. Committed to bringing a new experience to the construction and management of power distribution in computer rooms, it is mainly used in data centers and computer rooms such as finance, telecommunications, enterprises, and governments, with a capacity range of 30KVA-160KVA. The entire power distribution system adopts a standard network cabinet and modular structure design, with rich optional accessories, and can customize personalized high-reliability products for customers according to the actual needs of the computer room.
The intelligent power distribution cabinet monitors the current of each output branch in real time, and can set the warning value of the abnormal current of each output branch. For example, if the 16A switch sets the alarm value to 14A, it will alarm when the load exceeds 14A, and the fault can be detected in advance. Or human-operated hidden dangers, to avoid overloading, the switch cuts off the power supply, causing the entire cabinet equipment to be powered off. In addition, hot-swappable circuit breakers are selected for the output branch, which has the ability to adjust the phase of the power supply, and can easily realize the flexible adjustment of the three-phase imbalance. It is also possible to increase the output branch online and replace the switch when the power is not interrupted.
6. Features of the power distribution cabinet
The product also uses a large-screen LCD touch screen to monitor all-round power quality such as voltage, current, frequency, useful power, useless power, electric energy, and harmonics. Users can see the operating status of the power distribution system in the computer room at a glance, so as to find potential safety hazards early and avoid risks early.
In addition, users can also choose functions such as ATS, EPO, lightning protection, isolation transformer, UPS maintenance switch, mains output shunt, etc., to ensure the safety and stability of the power distribution system in the computer room.
7. Operating procedures for power distribution cabinets
7.1 The power distribution cabinet is the eighth product of the ship's power distribution center and the normal operation of the equipment. Any unrelated personnel shall not flip the switch on the board.
7.2 After the generator set is started, use the speed-up switch on the power screen to manually accelerate slowly until the generator enters the normal working state, and the voltage and frequency reach the specified value before closing and sending power.
7.3 After the power distribution board enters the power distribution state, the speed-up switch of the power panel shall not be pulled arbitrarily, and the lock switch of the air circuit breaker shall not be used in non-emergency situations.
7.4 Parallel operation of generators must be operated in strict accordance with the requirements and regulations of paralleling conditions, and attention should be paid to phenomena such as reverse power (reverse current) and paralleling failure.
7.5 When shutting down, the load of the generator should be cut off first, and then stop without load, and it is not allowed to stop directly with load.
7.6 When plugging in shore power, first cut off the power switches of the shore power panel, and then check the correctness of the wiring and phase sequence. After confirming the correctness, the ship-to-shore power conversion can be implemented. Load operation is strictly prohibited.
7.7 The power distribution cabinet should be cleaned and maintained regularly so that the equipment is always in good working condition.
7.8 When the generator is working, when the engineers operate the switchboard, they should concentrate their thoughts and operate carefully to prevent accidents, otherwise they will be held accountable for personal accidents.
7.9 The charging and discharging board is the ship's emergency switchboard, and the crew on duty should check its working status frequently to ensure sufficient low-voltage power at any time, and grasp the working status of the magnetic saturation regulator through the on-board instrument.
7.10 During normal navigation, all switches on the switchboard should be connected to ensure that the generator can be started at any time and put into use at any time.
7.11 The above points are expected to be strictly observed by the wheel department members.
8. Microcomputer protection device of power distribution cabinet
On the basis of many years of application experience of domestic and foreign counterparts in power distribution microcomputer protection devices, combined with the actual characteristics of domestic comprehensive automation systems, the high-tech products of power automation that integrate protection, monitoring, control, communication and other functions are developed. Ideal electrical unit for switchgear. The product has a built-in protection library consisting of more than 20 standard protection programs, and has a complete and powerful acquisition function for the voltage and current analog and switch values of primary equipment (the current measurement is realized through the protection CT).
9. Device characteristics of power distribution cabinet
The microcomputer protection device of the power distribution cabinet is composed of high-integration, bus parallel-out chip single-chip microcomputer, high-precision current and voltage transformer, high-dielectric strength export intermediate relay, and high-reliability switching power supply module and other components. The switch cabinet microcomputer protection device is mainly used as a switch cabinet with a voltage level of 110KV and below. Power plants, substations, distribution stations, etc., can also be used as the protection and measurement and control of the voltage and current of the system in the switchgear with voltage levels between 70V and 220V.
10. Power supply of power distribution cabinet
When using diesel generator sets in normal times, it is not known that the timely power supply of generator sets is also a big question:
10.1 Inspection of start solenoid valve
When the generator is running, people have summed up a set of inspection methods of "one look, two listens, three touches, and four smells". Listening at startup is a very important step. Take the American original Cummins generator as an example, just press the start button, and it will start after three seconds. Two "clicks" are heard within these three seconds. Once the second sound cannot be heard, it is necessary to check whether the start solenoid valve is working normally. If the solenoid coil is blown out, the generator will of course not start.
10.2 Inspection of the battery pack
Since the backup power is not often put into use, whether the generator can start normally depends on the maintenance of the battery. If there is a problem with the battery pack, the more common situation is: there is voltage but no current. At this time, the sound of the solenoid valve in the starter motor can be heard, but the coupling cannot be moved. There are three reasons why the battery pack cannot stop due to problems: 1. Stop charging the battery during the test run, which will cause the battery to run out of power. 2. The mechanical oil pump is driven by a belt. The pump oil volume at the rated speed is large. However, the power supply of the battery pack is insufficient, so that the spring leaf in the shut-off valve cannot be sealed due to insufficient suction of the solenoid valve when the machine stops. Spray from the four oil outlet holes. Out of the fuel, resulting in non-stop. 3. Domestic batteries usually have a lifespan of two years and are not replaced regularly.
10.3 Inspection of diesel oil and lubricating oil
Because the unit is static for a long time, the various materials of the unit itself will undergo complex chemical and physical changes with engine oil, cooling water, diesel, air, etc., thus "putting" the unit to failure. For this reason, attention should be paid to the problem of oil. For fire safety, diesel oil tanks are usually placed in a closed room. Due to the condensation of water vapor in the atmosphere due to temperature changes, water droplets form and hang on the inner wall of the fuel tank and flow into the diesel oil, causing the water content of the diesel oil to exceed the standard. If such diesel oil enters the high-pressure oil pump of the diesel engine, it will corrode the precision coupling - the plunger, and seriously damage the unit. Generator lubricating oil has a shelf life, long-term storage, the physical and chemical properties of the lubricating oil will change, resulting in the deterioration of the lubrication state of the unit when it is working, and it is easy to cause damage to the generator parts.
11. AC and configuration of power distribution cabinet
Whether the diesel generator set generates direct current or alternating current is related to the configured generator. If it is equipped with an alternator, it will generate alternating current, and if it is configured with a DC generator, it will generate direct current.
Modern diesel generator sets, including small diesel generator sets for household backup, are generally equipped with three-phase AC brushless synchronous generators. So what is emitted is alternating current. Generally 220V, 380V AC. However, when the rotor of the machine does not reach the rated speed, the voltage and frequency of the generator will be lower.
High temperature drop grid prevention
In order to overcome the impact of high temperature weather on substation equipment, timely remove obstacles to the operation of the power grid, and ensure the safe operation of the power grid in high temperature seasons. Based on the actual situation, the electricity bureaus launched the comprehensive investigation of the high temperature prevention phase of this year's "peak summer". All enterprises also monitor the operation of their generator sets at any time!
The bureau's operation and maintenance work area combined with the actual situation, planned in advance, prevented in advance, and formulated a special work plan for preventing high temperatures in the "peak summer". Adhere to the guiding ideology of "safety first, prevention first" to prevent the substation from being completely shut down due to factors such as high temperature and heavy load, and to prevent equipment damage accidents caused by lightning strikes, overheating, and overloading of main equipment such as transformers and GIS transformers. As the focus, according to the principle of combining investigation and treatment, carry out high temperature prevention work in a planned, focused and targeted manner.
It is reported that each station (station) in the work area of the bureau has begun to monitor the load conditions of the main transformers, lines, busbars, and secondary circuits used in the jurisdiction, oil-filled and air-filled equipment Oil and gas pressure conditions, main transformer temperature rise and cooling system operation status, the operation status of used transformers, and important secondary circuits to carry out a comprehensive inspection of the temperature measurement, and record the heavy load circuits, high node temperature equipment, and defective equipment, and Make good records and be aware of them, so as to carry out targeted analysis and maintenance and prevention work in combination with weak links.
The special work on high temperature prevention for the "peak summer" requires that the comprehensive investigation phase of the "peak summer" prevention work in the substation operation and maintenance work area should be fully completed before June 27, and the key tracking stage will continue until September 30. day. Deploy at the same time. On the basis of daily inspection work, each station (station) should combine: heavy load lines, transformers, secondary AC and DC circuits; main transformer temperature rise, cooling system operation status; contact temperature measurement, oil and gas equipment Pressure sealing conditions; environmental temperature changes; special operation mode, equipment defect elimination; municipal important power protection tasks and other actual conditions to narrow the scope of work, focus, rhythmic, and targeted organization of special inspections and patrols to eliminate high-temperature weather Abnormal equipment to ensure safe operation.