Relay protection of the residential electrical network. Scheme, description

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Relay protection of the residential electrical network

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Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network, uninterruptible power supplies

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Voltage instability in regional power lines, unfortunately, is not so rare. Especially during strong winds, when the wires of overhead power lines-0,4 can overlap. Because of this, electrical, radio and television equipment, included in the apartment network, suffers, where the voltage can suddenly become equal to, say, 100 V or, conversely, 350 V. However, I have not been worried about my household appliances for five years now, since self-made relay automation reliably protects it from abnormal voltage in the network.

The circuit diagram of such a machine is so simple that anyone can implement it. It is only necessary to acquire an electromagnetic starter of the PME-2/1 type (PMA-3102 is also suitable), two RN-53/200 voltage relays, a start button in a protective case designed for reliable switching in electrical circuits, a "neon" light bulb and three resistors MINT. A voltmeter with a scale from 0 to 400 V will not hurt either - to control the voltage at the entrance to the apartment network.

Relay protection of the residential electrical network
Schematic diagram of the automatic relay protection of the apartment network against voltage drops in power lines

Before assembling the circuit, both RN-53/200 relays undergo a slight modification. They remove the wires coming from pins 4 to the rectifier bridges, and resistors are installed between pins 2 and 4. A typical electromagnetic starter is converted into a low-noise switching device, for which the mating ends of the magnetic circuit are carefully cleaned and adjusted to each other, the fixed parts of the contactor are fixed to the board not directly, but through a shock-absorbing (for example, foam rubber) gasket.

Installation of the circuit breaker hinged. The wire for it is preferably used copper (although aluminum is not excluded) with a cross section of 1,5-2,5 mm2 (the choice is based on the nominal operating current in the network).

Naturally, this takes into account the rules of electrical and fire safety. The mounting plate on the shield is installed higher, next to the electricity consumption meter and fuses, in order to completely exclude accidental contact with the details of the machine in the future.

The operation of a properly installed protective system usually does not cause any complaints from users. By the glow of a neon light bulb (and even more so by readings of a voltmeter that differ from zero), they judge the presence of voltage at the entrance to the apartment network and conclude whether it is worth turning on the home load.

If the BV1 button is pressed with abnormal and, then the K1 starter will not turn on, and its open additional contacts will not let "dangerous" electricity into the house. In other cases, EV1 will provide voltage (through normally closed K3.1 "maximum control" relays and connected as a result of operation of the "minimum control" relay K2.1) to the starter coil K1. Turning on, the latter will close the power contacts K1.1, supplying a "phase" to the house.

The trip voltage of the "max control" relay should ideally be set to 242 V. This is the so-called setting. Taking into account local conditions, it, of course, may be slightly higher than the recommended value. remaining, however, within reason. Well, it is desirable to bring the return voltage ("falling off") of the "minimum control" relay to a level of 180-200 V.

Then everything goes on as usual. With an increase and above the setting, the "control to the maximum" relay is activated, opening the short circuit contacts. 1 in the power circuit of the magnetic starter coil. If the voltage supplied to the input buses suddenly drops, then the “minimum control” relay “falls off”, which entails the disconnection of K2.1. As a result, with both voltage anomalies, the coil K1 of the magnetic starter is de-energized. This means that the K1.1 power contacts will disconnect and the entire home network will turn off.

The efficiency of the machine is determined by the speed of operation of the voltage relay and the time of "disappearance" of the contactor of the starter.

Author: V.Karnaukh

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