A modern electrician in a house or apartment represents a wide variety of technical means that require control over the supply of voltage. Power management is performed by a three-phase voltage relay, closing or opening electrical circuits in case of emergency.
The purpose of the voltage relay
Most protective devices contain electronic control relays. When the monitored parameters deviate from the specified limits, they operate by disconnecting the circuit. All relays consist of three elements. The first one is receptive. It transfers the value of the controlled value to the intermediate element, where it is reconciled with standard indicators. In case of deviations, the signal is transmitted to the actuator, which turns off the power.
Power surges during power supply, as well as breaks in the power supply circuit can cause the failure of consumer devices. In worn-out power grids, phase cohesion or the burning of the neutral wire can occur, which leads to voltage distortions from 0 to 380 V. In this case, all connected household appliances without protection can be damaged.
A three-phase voltage relay is used to instantly respond to an increase in voltage above the permissible level and to open an electric circuit. The phase is switched off when a magnetic flux occurs in an electromagnet while passing through a current winding. Using an electronic circuit, the relay is tuned to certain boundary voltage values, above which the electrical contacts in the load circuit open.
The voltage relay is installed in the apartment electrical switchboard, but there are models that are plugged into an outlet. With their help, the lower and upper limits of the voltage change are selected. It is convenient to set the range of 180-245 V, and then additionally configure so that the number of operations is not more than one per month. When the voltage in the network is constantly increased or decreased, it is advisable to install a stabilizer.
The connection of a three-phase voltage relay is necessarily done after the input circuit breaker, the value of which is selected one step less, for example, in a ratio of 32 A and 40 A.
The three-phase voltage relay is connected to the current-carrying and neutral wires of the network, as well as to the output contacts of the load connection to monitor their condition. Changing modes is done by switching jumpers on the relay terminals. When triggered, its coil is de-energized and opens the power contacts. They can be connected to the winding of the power contactor, which also works by disconnecting consumers. After a time delay, when the voltage is restored again, the relay returns to its original state, closing its power contacts.
The above diagram turns off consumers when a network problem occurs. Protection can also be built on 3 single-phase independent voltage relays. It is used for individual loads on each lead-in current-carrying wire. Power contactors are usually not used here if the load is not higher than 7 kW. The advantage of the method is the conservation of voltage in the remaining phases when one of them is turned off.
Features of common types of voltage relays
The devices differ in their functions and quality. Depending on whom, for what purpose you need such devices, they are selected and installed. Next, consider the most popular devices.
Relay RNPP-311
The device protects the network in the following accidents:
- excess voltage of the set values;
- short circuit or phase rotation disturbance;
- skewed or broken phases.
The device also monitors other network parameters and opens the load supply when they deviate from the norm. The three-phase voltage relay RNPP-311 can be configured for two control modes.
- Linear - operation by phase imbalance, when zero offset is not dangerous for the consumer.
- Phase - when the phase imbalance and zero offset are unacceptable.
On the front panel are indicators of voltage, load connection and some abnormalities. The adjustment is made by six potentiometers. The following parameters are set:
- boundary values of maximum and minimum stresses, as well as the limit value of phase imbalance;
- shutdown time delay in case of accidents;
- delay in connecting to the network after the settings are restored.
The device remains operational when zero and one of the phases or at least two remain active.
Relay RKN-3-15-08
The device serves for the following control methods:
- voltage in phases;
- "sticking" of conductors;
- violation of the order of the alternation of phases;
- voltage deviations outside the specified range.
The thresholds are set by two potentiometers. Indication allows you to control voltage, network errors and the operation of the built-in electromagnetic relay. Operating conditions are normal.
The connection diagram of the three-phase voltage relay RKN-3-15-08 is practically no different from the one given earlier. It only has a simpler setup. The three-phase price for this voltage relay is slightly lower than for RNPP-311. It is about 1,500 rubles. Different modifications of both types can vary significantly in cost, it all depends on the functionality.
ASP Series
In a separate row are the fully digital safety relays of the ASP series. In most of them it is no longer possible to find tuning elements of analog signals. Potentiometers depend on the influence of the external environment, quickly age, ratings change, and contact often disappears.
Digital devices do not contain contact mechanical parts, due to which the action of external factors is reduced, and their reliability increases. In appearance, the devices are distinguished by a digital display. Their price is higher on average, but you can find budget items.
Relay ASP-3RMT
The model is basic, and it has all the most necessary functions that a three-phase voltage relay should have. Its price is 2 times lower than other devices with built-in digital voltmeters and screens. If you do not need a display, but you need protection, the device is quite suitable for installation.
Relay ASP-3RVN
A three-phase voltage and phase control relay with a microprocessor is used to control the supply of electricity to refrigerators, air conditioners, compressors and other devices where electric motors are used. The device is convenient in that it allows you to control the voltage at each phase on the display, as well as monitor its asymmetry. Built-in memory powered by an independent source makes it possible to remember the parameters and the number of emergency shutdowns with the ability to display. This does not require special configuration skills. Additional functions are available through the control buttons.
The ASP-3RVN device is connected to the network in parallel with the load, similar to the schemes presented earlier. The device monitors the current network voltage. In the event of an accident, its contacts are opened, included in the gap of the starter winding. After connecting and supplying power, the protection relay checks for voltage. This is indicated by three LEDs. If phase rotation or cohesion is disturbed, dashes (-) are displayed on the indicator. Further, the measured phase voltages are displayed on the screen with an interval of several seconds. The corresponding LEDs light up.
In the event of an accident, the causes of its occurrence are displayed. The settings are initially factory settings, but they can be changed by pressing the appropriate buttons. If errors appear during installation, they can be reset and reset to factory defaults with the click of a button. All settings are stored in memory and can be checked.
ABB monitoring relay
One of the well-known devices for protecting electrical equipment is a three-phase voltage relay ABB. The device has established itself as one of the most reliable in violation of the voltage balance. For three-phase networks, the ABB SQZ3 device has been developed, withstanding voltages up to 400 V. A large assortment allows you to choose the right model for certain working conditions. The device allows you to control:
- mains voltage with load shedding in emergency situations;
- distortions, disappearance and correct phase rotation with signals in case of deviations.
ABB Company has established itself as a reliable supplier of high-quality electrical equipment, easy to operate and universal.
Conclusion
A three-phase voltage monitoring relay is a necessary part of the power supply system to the devices. It will reliably protect the electrical network of an apartment or house, as well as expensive electronics from power surges and distortions.