Categories: Automata and RCD
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What are overvoltage and undervoltage releases and how are they used?

 

Undervoltage and overvoltage releases are one of the types of additional devices for circuit breakers. They are designed to disconnect the load in the event of a voltage deviation from the nominal 220V. In this article I will talk about the method and circuit of connecting these devices, their advantages and disadvantages.

IEK PMM47 undervoltage release

What is it and what is it for?

Undervoltage and overvoltage release is one of the devices designed to control circuit breaker. Almost every modern modular machine can connect additional devices. To do this, there is a plug on the side of the machine, unscrewing which you will see a lever for connecting such devices to the mechanical part of the power contact drive.

Connecting the release to the machine
Position off and on

If you press this lever with the cocked flag of the machine (ON), it will turn off. Additional devices, such as this trip units and various devices, block contacts, for example, for signaling an accident.

The undervoltage and overvoltage release is an electronic device that monitors the voltage level in the network, if it goes beyond the set limits, it turns off the circuit breaker


Overview of characteristics and wiring diagrams on the example of IEK PMM47

One of the most common options is the PMK47 model from IEK, it has the following characteristics:

  • rated supply voltage 230 (V);

  • operating voltage range 50 - 275 (V);

  • triggered when the voltage in the network is less than 165 ± 10 (V) and more than voltage 265 ± 10 (V);

  • shutdown time when triggered at a minimum voltage of 0.2 - 0.5 (sec.);

  • when triggered from a maximum voltage of 0.05 - 0.15 (sec.);

  • the number of on-off cycles - at least 10,000 times.

The lower and upper voltage levels, at which the operation occurs, are not adjusted, at the same time they are at acceptable levels, therefore this fact cannot be considered a drawback.

The principle of operation is that in РММ47 the electronic circuit monitors the voltage level in the circuit, when it goes beyond the nominal values, power is supplied to the solenoid, it drives the pusher (it resembles a retractable car starter). The pusher mechanically acts on the plastic lever moving it.

If the voltage rises or subsides and the release trips, you cannot turn on the machine until you click on the “Reset” button, because after operation the mechanism remains in this position and it is supposed to manually return to the original position.

The end of this lever is brought out of the housing and with its help docking with a circuit breaker occurs. It is the lever of the independent trip that drives the automatic shutdown mechanism. Thus, a connection can be made with both single-pole and three-pole machines.

When docking the trip unit with an automatic machine, you need to put the automatic machine flag in the “off” position, indicated as “O”. (ON - “I”)

After docking with the machine, you need to connect the phase to the release (the one that comes out of the machine!) and zero. Zero is needed to measure voltage. However, there are no contacts inside the trip unit; it is used only as a drive to turn off the machine.

Connection diagram of the IEK PMM47 minimum and maximum voltage release
Connection diagram for the release from the manufacturer's instructions

Connection to a three-pole circuit breaker is similar. The need to connect the “output” phase from the machine to the terminals of the trip unit is due to the fact that after the machine is turned off, the trip unit must also be de-energized - otherwise the solenoid in it and the electronic circuit will fail.

Disassembled device

Are there any alternatives?

At first, RMM-47 produces not only IEK, but also the company Ekf. It has slightly different characteristics, instead of the limiting 165 and 265 volts, the operating voltage range of 170-270V is selected.

RMM-47 from EKF

EKF also has an alternative line AV-AVERES, where both the releases of the maximum and minimum, and only the minimum voltage are presented, as well as a number of other devices for connecting to the circuit breaker (additional and signal contacts).

AV-AVERES releases

Company TDM also produces RMM-47, a device similar in characteristics to IEK, and the difference is not the reset button, but the flag as on the machines themselves. Similar devices are produced by different manufacturers to ensure mechanical and overall compatibility with their machines.

PMM-47 by TDM

Well-known manufacturers such as ABB, for example, independent releases were also not spared, they are called "auxiliary elements for circuit breakers" in the catalogs, devices belong to the line System pro m compact and as the manufacturer claims, they are suitable for all series, for example, S200, F200, DS200. But unlike previous manufacturers, releases of either the minimum or maximum voltage (separately) are presented here.

ABB Company Directory:Accessories and ABB Accessories


Author's opinion on undervoltage / overvoltage releases

The device is certainly worthy of attention and can be successfully used where high and low voltage is infrequent, for example, to protect against phase imbalance. For the reason that circuit breakers are not designed to constantly turn on and off.

That is, if in your house voltage surges and deviations from 220V are in the order of things and happen almost every day, then you should pay attention to a variety of voltage relay and if necessary, increase their switching ability to use contactor (starter). In addition, the releases do not have the ability to adjust the thresholds, while almost all voltage relays have this option, in addition, in most cases, you can manually set the reset time.

See also at e.imadeself.com:

  • Additional devices for circuit breakers
  • Automatic switches of the A3700 HEMZ series
  • Characteristics of circuit breakers
  • Thermal circuit breaker release
  • About electrical protection devices for "dummies": automatic switches ...
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    Comments:

    # 1 wrote: Alex gall | [quote]

     
     

    The device is certainly worthy of attention and can be successfully used where high and low voltage is infrequent, for example, to protect against phase imbalance.

    There is a more understandable and clear definition of the need for machines with such releases - where there is a danger of a break in the neutral wire. First of all, it is important for power supply from overhead lines, in any case, this is stated in the PUE p. 7.1.21. Here, at the entrance to the building from three-phase overhead lines (in the ASU), it is recommended to put machines with such releases. That is, on three-phase inputs with a PEN conductor, from which different consumers are powered. On a single-phase input into an apartment or in a private house, they are not needed at all, here only a voltage relay can help. And guessing how often you have increased or decreased voltage is a dumb thing.

     
    Comments:

    # 2 wrote: | [quote]

     
     

    Alex gall,
    Isn't that what I said? Or do you see a fundamental difference between a zero break and a phase imbalance? By the way, will this circuit work in the event of a zero break, in your opinion? It may not work, just as it happens with electronic RCDs, but this is more a danger when the input is cut off from zero, and not in a riser.

    It was about the fact that you can’t turn the machine into a relay by installing this device in the village, where there can be 150 and 250 volts at the beginning or end of the line. There you need to install a pH.

    In any case, thanks for the link to the PUE clause. For some reason I did not know about its existence, or rather did not take it into account.

     
    Comments:

    # 3 wrote: Alex gall | [quote]

     
     

    I said only what I wanted to say))) That is, I specified the reason why there is a need to put an automatic machine with such a release.
    The reason you indicated in the article seemed to me slurred and even controversial. Well what does it mean:

    It can be successfully used where over and under voltage is infrequent, for example, to protect against phase imbalance.

    How do you define “often or not often”? Once a year, a month, a week a day? What should be understood as "often"?
    We need specifics, which is just indicated in the PUE. The use of such releases for everyday life on any other occasion looks ridiculous, regardless of whether the voltage jumps frequently or rarely in the network.
    The task of the described release is to disconnect the network at the entrance to the building in emergency mode (open PEN conductor) if this network is 4-wire (i.e. three phases and a conductor) and single-phase consumers are powered from it.
     

    Or do you see a fundamental difference between a zero break and a phase imbalance?

    Of course I see.
    The phase imbalance is quite an operating mode for a three-phase network with single-phase loads. For everyday life, this is a common thing.
    But a zero break is an emergency mode for the network, which requires its immediate shutdown. Especially if it is not just a neutral wire, but at the same time it is used as a protective wire in the TN-C-S system. That is why the machines with the described releases are placed only at the input. It can be said at the boundary of TN-C and TN-S systems. So that behind the zero point (PEN conductor), the voltage is turned off. Because otherwise it will appear on the housings of electrical appliances through a protective conductor.
    If the power system is pure TN-S, then there isn’t much point in this.
    If PEN is cut off in the riser, such a release will also work if the machine with it is installed as an input in the floor board, from which several apartments on different phases are powered. What is not done in practice, but it is theoretically possible precisely as protection against the zero point loss of the riser.

    I hope the meaning is clear - PEN break - the voltage is removed from the phases and the voltage across the conductor common to all PE apartments from the floor board to electrical appliances in the apartment will not go.
    But in practice, the nanny option is used without fail only at the entrance to the building from the overhead line, where similar accidents are most likely.

    As for the voltage relay - it has a different task than the max / min release. Not just because the machine is not designed for frequent tripping, but also because it is more convenient for protecting electrical appliances from dangerous voltage fluctuations and has several important advantages.
    But the PH will not be able to protect against the appearance of voltage on the device case when PEN breaks in the case described above.
    That is, the functions of the devices are different.

     
    Comments:

    # 4 wrote: Sergei | [quote]

     
     

    Alex gall,
    Everything is clear and to the point.

     
    Comments:

    # 5 wrote: | [quote]

     
     

    Alex gallDo you need specifics? Read the PUE, I also love to read it. Most people do not understand the presentation in this document. In addition to specialists like you, hundreds of thousands of people visit the site who don’t understand what’s what. I said in the article that you should not turn the machine into a launch vehicle, and if you are afraid of jumps, distortions and burnouts - put a launch vehicle.

    Of course, installing a trip unit at the entrance to the apartment is not entirely justified. Still, this is for the ASU, but if you take into account the form factor of these particular devices, it is oriented towards using relatively weak machines, which are not the fact that they will be used in the ASU of the same many floors (some have fuses in general) ... For , we shall call asractically, there are other devices of "large" automata.

    Personally, it’s not entirely clear to me why the manufacturer gives examples of using them with 1p AB.

    The article is written in order to tell an ordinary person (NOT ELECTRICIAN) about this product, so that he knows whether he chooses the correct protective devices for the electrical panel (which I personally do not approve of, professionals should do everything). The functions that it performs are described.

    Regarding your opinion about phase imbalance and breakage / burning out. Do you understand what it comes from? Judging by the context, you understand much better than most "specialist commentators."

    Naturally, there can be no symmetry in everyday life, as well as perfect contact in the neutral conductor along the entire length from the transformer substation to the end consumer. Accordingly, there is always a bias, the question is to what extent - a couple of volts or a couple of tens. In the first case, this is normal, and in the second it is already emergency.

    The allowance for the appearance of potential on the case is completely and completely agree. But the LV can work out if the asymmetry is strong and the voltage goes beyond the settings. And it may not work because the voltage is within the limits. Especially if the owner rude them to extreme positions.

    I propose not to continue the discussion, because I wrote about the use of this product in an apartment electrical switchboard (when I compared it with the LV), but you describe the CORRECT use of the release on the input to the object (it doesn’t matter which object we are talking about).

    Simply, if it is not correct to understand the words of the manufacturer, then we will receive, in each group, a release from the unfortunate installers.

    Thank you for completing the information presented in the article, it is constructive, logical and justified!