Domestic power supply is characterized by low reliability and unsatisfactory quality of electricity. This is due to outdated electrical networks, wear and tear of equipment, low performance of energy converters, transients at sources and users of electricity, natural and climatic factors. In such conditions, uninterruptible power systems are urgently needed to ensure the operation of consumers of both the first and other categories.
For owners of apartments and houses, stable operation of the power grid is also important. Stopping the work of household appliances is not the biggest of troubles. Much more important is the trouble-free functioning of life support systems, in particular the heating system, if it directly depends on the power supply. Uninterruptible power supply UPS (UPS) comes to the rescue - a device that protects electrical receivers from shutdown due to the accumulation of electricity in batteries (batteries) and guaranteesthe required power quality (PQ) in stand-alone and network modes of operation.
Before charting an approach to powering loads without failure, one should know what kind of failures can be expected from domestic power networks.
Power failures in electrical networks
Undervoltage is a frequent occurrence in power supply. But it does not particularly predominate over the increased, which is also common. At night, the voltage is stable, during the day it decreases, and in the evening, when most of the loads are turned off, it increases.
Unstable frequency is also a failure, although quite rare. When the network load is high, it can drop to 45 Hz, which leads to significant signal distortion that negatively affects the operation of the UPS. Some devices treat the frequency reduction as an accident and the battery may drain quickly.
Complete blackouts are not uncommon. Electricians don't care much about electronics and can suddenly shut down a building. An instant power outage is enough to lose information on a computer. Power outages can occur when networks are overloaded. Therefore, it is important how reliably the UPS system delivers uninterruptible power.
UPS classification
They are grouped into three groups:
- Low-power UPS for connection through electrical outlets. The execution is desktop or floor, and the power ranges from 0.25 to 3 kW.
- Devices of medium power - from 3 to 30 kW - contain a block of sockets built into the inside, or are also switched on through groupssockets in the power supply network of consumers from the control panel. Devices are made for placement both in offices and in separate equipped rooms.
- High power UPS - from 10 to 800 kW. They are located in electrical rooms. They are collected in groups and created energy systems of high power - up to several thousand kW.
UPS types
There are currently 4 types of UPS (UPS). The properties common to all are:
- filtering from impulses and noise;
- waveform dewarping;
- voltage stabilization (not all models);
- keep the battery charged;
- When the UPS battery runs out, it will first give an alarm and then turn off the consumer.
Off-line UPS
The principle of operation of devices of this modification is to supply the consumer from the existing network and instantly switch to autonomous backup power in emergency situations (4-12 ms). They are simpler and cheaper than other types.
UPS normally switches to internal battery.
When operating from the mains, the device suppresses noise with impulses and maintains the voltage at a given level. Part of the energy is spent on recharging the battery. In the case of network operation in non-standard mode, the consumer switches to battery operation. Each UPS model determines in its own way the need to switch to this mode. Battery life depends on battery characteristics and power consumption of the load. In the event of a discharge of the backup power supplya command is given to turn off the consumer. If the mains voltage reaches a normal level, the UPS switches to normal mains operation and battery charging starts.
Line Interactive
Line interactive ups are equipped with stabilisers, which work continuously and provide infrequent battery connection.
The device interacts with the network by controlling the amplitude and shape of the mains voltage.
When the voltage decreases or increases, the unit corrects its value by switching the taps of the autotransformer. In this way, its nominal value is maintained. If the parameter is out of range and the switching range is no longer sufficient, the UPS switches to battery backup. The unit can be disconnected from the main power when a distorted signal is received. There are models that correct the voltage waveform without switching to battery operation.
Ferroresonant UPS
The device contains a ferroresonant transformer that acts as a voltage regulator. Its advantage is the accumulation of energy in the magnetic field, which is released during switching within 8-16 ms. This period of time is sufficient for the UPS to enter a new mode of operation.
The transformer performs the additional function of a noise filter. Input voltage distortion does not affect the output waveform, which remains sinusoidal.
Double Conversion UPS
Double energy conversion deviceworks on the principle of rectifying the mains voltage, and then again turns it into a stabilized variable. A more powerful rectifier is used here, which not only recharges the battery, but also supplies the inverter with a stabilized DC voltage.
From the output of the device, an alternating stabilized voltage is supplied to the load.
When double conversion is not enough to correct the mains voltage, additional charge is supplied from the battery to the inverter. Switching does not occur, but the mode is already different.
When the inverter fails, it switches to mains operation via bypass. The choice of a double conversion UPS for private use is irrational due to large energy losses. This type of protection is used by organizations where high reliability of equipment is required.
Types of systems
Uninterruptible power supply systems can be centralized or distributed. In the first case, one UPS operates for the entire building or a separate floor, which can cope with all loads.
Distributed uninterruptible power systems include several protection devices, each of which works on one computer or other piece of equipment. They are quite effective.
The advantages of a distributed system are as follows:
- UPS is selected specifically for a single device that is the most important or operating in harsh environments.
- The system cangradually build up, starting with server protection and moving to workstations.
- Failed UPS can be replaced with other less important system elements.
- Low-power UPS does not need to be installed and maintained by special personnel.
- Ability to connect to a conventional power outlet through sockets.
- UPS are applied independently.
Centralized uninterruptible power systems include high-level UPS, which better protect the equipment. Despite their high cost, overall cost savings are achieved, as one device is cheaper than several. But for simple computers, the system will cost more, since its maintenance requires highly qualified personnel or the services of specialized firms that install and maintain uninterruptible power systems.
It is required in the following cases:
- computers are the main load of the network;
- some organizations need very reliable systems like banks;
- consumers differ significantly in power: computer system, emergency lighting, communications, security system.
What to look for when choosing a UPS?
When choosing an uninterruptible power supply system, there are several important factors to consider. We list the main ones.
What is equipment protected from?
First of all, it is necessary to measure the voltage in the electrical network. The minimum cycle in duration will be a day. He is the mostreflects the operation of the electrical network. If you have to work on weekends, you need to get information on the weekly cycle, during the day and night.
It is important to determine the maximum and minimum voltage, as well as the power and pulse frequency in the network. The instrument can be a digital oscilloscope or a recorder.
The easiest way for the user is to take voltage measurements, during which, in his opinion, the voltage reaches a maximum and minimum. Do not ignore the weekend.
If the landlord has powerful equipment, it is necessary to measure the voltage in the home network when it is turned on and off. You should find out how often the power is turned off in the mains at home and for what reasons. It is important to have a ground wire in the apartment. In this case, you should find out how securely it is connected to the floor board bus.
Type of protected equipment
Compiling a list of equipment that requires the use of a UPS. In this case, you need to know the power consumed by each device. It is enough to determine its nominal value, which is in the technical specifications. Some equipment sometimes consumes maximum energy, several times higher than the nominal value. You should set a power reserve for it.
Autonomy period
Here it is important to determine for what period it is possible to safely store data or complete the necessary technological operations (transfer of information, saving files, receiving messages).
Essential Personnel
Depending on the complexity of the system requireda certain staff of specialists for its operation. This must be clarified in order to correctly calculate all costs. The price of the protection system should not exceed 10% of the cost of the main equipment.
UPS for home
For an average cottage, an uninterruptible power supply system UPS (UPS) with a capacity of about 15 kW is convenient. To ensure autonomous operation for 2-3 hours, you need 4 batteries with a total capacity of 2000 Ah. They allow you to accumulate electricity of about 7 kWh.
In the house, the most important are the heating system and household appliances with a computer. The cost of the UPS depends on the power, the number of batteries and the manufacturer. For the boiler, you can purchase a 360 W source at a price of 7 thousand. For the whole house, you will need a UPS power of up to 15 kW, the price of which is more than 70 thousand rubles.
In addition to the converters, batteries are needed, which need to be changed periodically. UPS for the home costs a round sum. Uninterruptible power supply systems are especially costly.
Despite this, you can save on the repair of other equipment. In addition, there are alternative options using generators. Sometimes you can get away with installing voltage stabilizers, which cope with many tasks, including the correct shutdown of equipment.
Modern UPSs are equipped with a clear interface. On the display, you can monitor the operation of the system, where the main parameters are input and output voltage, power consumption, operation scheme, battery charge.
Which UPS to choose depends on the needs of the user. A home computer may have enough power for the duration of its shutdown. For uninterrupted operation of the boiler for 8-9 hours, you will need a 1 kW protective device with three batteries of 65 Ah.
Conclusion
Uninterruptible power supply systems are designed to provide autonomous operation of electrical appliances and electronic equipment for a short time. The main indicator is the power of the UPS and the capacity of the battery. It is advisable to choose equipment containing a voltage stabilizer.
Battery life depends on the characteristics of the battery and the power consumed by the load. In the event of a discharge of the backup power source, a command is given to turn off the consumer. If the mains voltage reaches a normal level, the UPS switches to normal mains operation and starts charging the battery.
