Most modern protective devices with the most complete functionality are designed for installation in the power supply panel of all consumers, in an apartment or office. This option is convenient in terms of installation work, especially in new buildings, but it has significant drawbacks:
- It is not possible in many old apartments, where the power supply board is taken out and locked, and if installed inside, then there is simply no place to install a protection device.
- If the installation is provided (with an additional shield or in other ways), it is necessary to foresee the complexity of the situation when suddenly the whole apartment is de-energized, the light goes out (below, from the text it will be clear that this can happen quite often, especially in rural terrain). It is good if the protection device has a low turn-on delay. And if 5-10 minutes and it is unknown to the household? And if the voltage steadily increased slightly above the set point, which is typical for horticultural and rural networks?
- At the moment of switching on after a power outage with a large number of consumers turned on, a refrigerator, a washing machine, other kitchen appliances, a TV (often 2, 3), a computer, etc. a strong current surge occurs, which can lead to operation of the machine. Replacing it with an automatic machine with a higher current setting is dangerous, especially in houses with aluminum wiring and branching by twisting wires, since the current of possible short-circuits may not lead to the operation of the machine and the wires may melt, this is a disaster for hidden wiring.
Thus, this option is more suitable for stable power grids with very rare dips and overvoltages and for small (in terms of energy consumption) office and industrial premises.
For apartments, however, it can be considered more preferable stabilizer installation. But again, not for the whole apartment, but for individual consumers who need to be protected from both overvoltage, and from its decrease - as a rule for refrigerators. As for modern electronic equipment. placed in rooms, many already know that it has internal stabilizers that allow a wide range of supply voltages, from about 130 to 250 V. Therefore, it makes no sense to protect it with any external stabilizers. Here, special overvoltage protection is required, starting already from 253 V (the upper limit according to GOST on the quality of power supply), with good filtration from microsecond pulses. To solve this problem, for many years, both the simplest (for example, "adapters") and the most high-quality filter-splitters with a constant (factory) or changeable (by the Consumer) setpoint for operation from an increase voltage. A review of such devices can be easily done on the Internet, so there is no point in listing them with any comments. Let's move on to the main issue that this article is devoted to, to consider approaches to solving the problem of protection against overvoltage.
The modern generation of the most functional protective devices was determined by the task of electrical protection of refrigerators, - two settings were required, for increasing and decreasing the voltage, and automatic switching on with a certain delay. Therefore, controllers and the corresponding display and programming elements began to be used. There were also devices that plugged into an outlet, for example, the Uniel UBR-16VR-1G35 / MDA relay.
As for the main function, - overvoltage protection, although they have become more convenient and of high quality in terms of filtering and varistor protection against impulses, they retained the main disadvantage is the automatic shutdown of consumers when the voltage rises more than a certain fixed settings. As I noted above, according to the current GOST mains voltage deviation should not exceed 253 volts. However, many networks, especially rural and horticultural ones, have frequent and long-term excess of this value. Therefore, protective device manufacturers provide for setpoint adjustments up to 270 V and even higher. At the same time, it is not profitable for manufacturers of electronic equipment to provide high reliability up to this level of supply voltage. Thus, the 253 - 260 volt zone of the most probable prolonged overvoltage is, one might say, the zone unspoken and for many Consumers unknown, but technically real conflict of interests of Consumers and Manufacturers. As a representative of the first party and having a fairly long experience in the development of so-called volt-machines, I resolved this conflict as follows.
Given the increasingly lower power level consumed by consumer electronic equipment and noted above the irrationality of protecting the entire apartment with one device, or many stabilizers, I took as a basis such algorithm: starting from the maximum voltage according to GOST, the device must extinguish its excess by means of active ballast and only with an input value of the order of 265 - 270 V, when its long duration is already unlikely, and the heat release on the ballast is already too high, the device should instantly disconnect the load.Shutdown should also occur when the ballast radiator overheats.
To reduce the heat release as much as possible, the damping should be dynamic (amplitude), that is, only along the "tops" of the sinusoid. This algorithm was implemented in a fairly simple circuit, using analog and key elements of widespread use, that is, without significant costs. Structurally, it is convenient to mount the device in a typical junction box about 100x100 mm in size, which is commonly used for electrical wiring. Below are photos of two main options for a load power of the order of 500 - 1000 watts.
In my creative workshop, a very convenient "thermo-breaker" for the devices under consideration was also developed - an automatic machine, instantly (several. ms) disconnecting the load (based on the breaker with a button, which is widely used in filters).
Unfortunately, the current crisis situation does not allow Manufacturers of protective devices spend money on new developments. My attempts on this score have not been crowned with success for this very reason. But, if you look at the market through the eyes of a far-sighted Manufacturer, who is also aware of the noted and other shortcomings of existing models, then you see an imminent rapid decline in demand. It is necessary to update the models that take into account the state of the existing power grids and the interests of the general consumer, especially in rural and suburban areas. So the author is waiting for proposals in this regard from the far-sighted managers of the companies.
Contacts for feedback: A. Vasiliev, engineer, e-mail [email protected]
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