What is a surge suppressor?
Arresters are designed to protect electrical appliances and equipment from the effects of high-voltage voltage pulses. Due to the simplicity of design and reliability, they are widely used in the field of energy supply. These protection devices replaced the outdated, very bulky valve arresters. Unlike its predecessors, the principle of operation of the limiter is not to use spark gaps. Non-linear resistors made of a material based on zinc oxide are used as the main working element in the arrester.
The primary and main element of what the surge suppressor consists of is a varistor, which acts as a nonlinear variable resistor. Structurally, the arrester consists of varistors placed in a housing made of porcelain or high-strength polymer. The design of the limiter is made taking into account the conditions ensuring explosion safety in case of currents short circuit. Depending on the purpose and installation location, the arrester can be made in various versions. For the limiters used to protect power lines and equipment of industrial facilities, a contact bolt is provided on the housing cover for connecting to the network, the set of arrester includes a base plate isolated from contact with the ground.
Devices designed to protect against peak voltage surges of the electrical household of an apartment or a country house are very compact, have an attractive design, and are also equipped with a device for mounting on din rail. Depending on the category of complexity, they can be equipped with an indication of operating modes and remote control.
The device of a modular surge suppressor is shown in the photo:
- Replaceable Varistor Module
- Varistor module wear indicator
- Clamp notches
Principle of operation
The operating principle of the arrester is explained by the nonlinear nature of the current-voltage characteristics (CVC) of the varistors. For their manufacture, a material is used where zinc oxide is used in a mixture with oxides of other metals. Due to the composition of this mixture, a column assembled from varistors is a combination of parallel and sequential inclusions of p-n junctions, which determines the nature of the current-voltage characteristics of nonlinear limiter resistors.
When the voltage characteristics of the network correspond to the rated values, the limiter is in the non-conductive state. The magnitude of the current in the varistors has meager values and is explained by capacitive nature. When a voltage pulse appears in the network, the value of which can cause a breakdown of the insulation of electrical equipment, a significant current pulse will occur in the circuit of non-linear resistors of the arrester, in accordance with their current-voltage characteristics. Ultimately, this reduces the amount of overvoltage to parameters that are safe for trouble-free operation of the equipment. When the voltage in the network normalizes, the arrester returns to non-conductive mode again.
Types of arrester
The design of surge arresters offered by manufacturers to power engineers is very diverse, they are distinguished by the following characteristics:
- Type of insulation (porcelain or polymer).
- Constructive execution (one or several columns).
- The magnitude of the operating voltage.
- The location of the limiter.
If we talk about surge suppressors installed on a DIN rail, then the devices are initially divided into single-phase and three-phase. In addition, modular arrester (they SPD), are divided into three main classes: B, C and D. Class B limiters are installed at the entrance to the building, C - directly in the switchboard of the apartment or house, D - for separate equipment that needs to be protected from interference if they could not cope with it Class B and C arrester. You can learn more about modular surge arresters from the video:
- Maximum acting voltage. Under this concept, it is necessary to understand the magnitude of the highest voltage value at which the limiter is able to maintain its operability without a time limit.
- The rated voltage is equivalent to the value which the arrester can withstand for 10 minutes.
- Conductivity Current. The magnitude of the current in the circuit of nonlinear resistors during the period of exposure to the nominal values of the applied voltage. As a rule, it has a meager value.
- Rated discharge current. Parameter that defines the classification of the limiter in lightning conditions.
- Estimated switching overvoltage current. Current value that defines the classification for switching overvoltages.
- Current throughput. The value is equivalent to the line discharge class.
- Resistance to short circuit. The category of the arrester's ability to withstand short circuit currents while maintaining the integrity of the containment.
The protection of the electrical facilities of administrative buildings, apartment buildings and enterprises is vested in the relevant services of energy companies, and it is the responsibility of the homeowner to protect his home from the undesirable consequences of a lightning discharge. Currently, this issue is being resolved simply. Specialized stores offer a wide selection of surge arresters of varying degrees of complexity and price range.
The figure below shows the connection of the arrester to a single-phase network and the symbol in the diagram. It is not difficult to connect a surge protector to the home electrical network, but it is better to entrust the specialist to carry out this operation if you do not have experience in electrical work.
Finally, we recommend that you watch a video on which the design and principle of operation of non-linear surge arresters is graphically examined:
So we examined the device, purpose and principle of operation of the surge suppressor. As you can see, there are various types and designs of these devices, so you can choose the right option for your own application conditions.
It will be interesting to read:
the video is not completely correctly described, the arrester does not protect from phase imbalance, there is a voltage relay for this