Quite often, even in modern houses and apartments, the voltage in electrical circuits and networks can jump in fairly large limits. Naturally, such leaps will adversely affect the operation of household appliances and its durability. To prevent such situations, use a voltage monitoring relay. The cause of such jumps may be a wire break or sagging, as a result of which the phase wire touches the zero wire. In just a few seconds, even before the protection works, computers, refrigerators, televisions, and other household appliances can burn out.
What is a voltage monitoring relay? This is a multi-pole device (from two to four poles), which is designed to automatically turn off and turn on various electrical devices (heaters, refrigerators, radio receivers, etc.). For automatic control in a voltage control relay, specially programmed microprocessors and microcontrollers are used, which are also sensors of temperature, current, voltage, voltage drop, and are also responsible for the process of disconnecting the device and the time it is turned off.
It should be clarified that according to the design and the conditions of use, depending on the number of phases, a single-phase and a three-phase voltage monitoring relay is distinguished. Three-phase protects electrical devices from overloads and from the possibility of load sagging in the event of an error in phase rotation, measures the effective values of phase and linear voltages in electrical networks with isolated or dead-grounded neutral, controls the switching device of the load supply circuit (in particular, the coil of the magnetic starter). Both the three-phase voltage monitoring relay and the single-phase device monitor the power contacts of the magnetic starter or contactor both before and after switching the load on and off, and monitor the condition of serviceability and operability of these contacts. The device turns off in case of burning or sticking of contacts. The voltage monitoring relay can turn on after a user-specified time after troubleshooting.
The relay works quite simply. Using the buttons on the case, it is necessary to set the threshold (maximum and minimum) voltage values at which the circuit will break. The default values are 170 V and 240 V. By default, the relay will trip after 0.02 seconds. Such a high speed disables the voltage before the devices and equipment are hit. However, the voltage monitoring relay does not protect against lightning strikes.
There are two types of such relays: for one outlet and for the house in general. The latter are the most common. Devices differ in load and permissible current strength.
When choosing and installing the voltage monitoring relay yourself, you should pay close attention to the installation instructions. By and large, the connection schemes are the same, however, depending on the manufacturer, some details may vary.