OPN-6 overvoltage limiter

Surge arrester OPN-6 is designed to protect the electrical equipment of switchgears from atmospheric and switching surges in electrical networks with a voltage of 6 kV AC, frequency 48 - 62 Hz with isolated or compensated neutral.

SPECIFICATIONS

Mains voltage class, effective value, kV - 6;

The highest long-term permissible operating voltage (Unr), effective value, kV - 6.9; 7.2;

Throughput current, A - 300; 400; 550;

Remaining voltage with a current pulse of 1/10 µs, amplitude of 10 kA, kV, not more than - 22.9;

Leakage distance, mm - 292;

The non-linear surge suppressor OPN-6 is a column of several series-connected highly non-linear metal oxide varistors made on the basis of zinc oxide, enclosed in a polymer insulating housing.

The polymer body of the limiter consists of a fiberglass cylinder and a protective tracking-erosion-resistant coating (ribbed tire) made of silicone rubber applied to the surface of the cylinder.

The polymer housing is closed from above and below by flanges intended for mounting the limiter and its connections to the network and grounding.

IMPULSE VOLTAGES AND REASONS FOR THEIR APPEARANCE

Often the cause of failure of electrical equipment is the presence of voltage pulses. Impulse voltages can be conditionally divided into internal and external. Internal impulse voltages, as a rule, arise when switching reactive (capacitive, inductive) loads, during breakdown, etc. The greatest threat is posed by voltage impulses that occur when an inductive load is disconnected. In these situations, the optimal choice of a varistor is not difficult - it is only necessary to calculate (or determine experimentally) the shape and duration of the voltage pulses. In the worst case, situations can be simulated and the effectiveness of the varistor protection can be tested. External impulse voltages are those whose sources are outside the system protected by the varistor.

Some reasons for such situations:

  - galvanic interaction with high voltage sources;

  - switching in networks (full switching on/off of voltage, switching on and off of compensating capacitor units, etc.);

  - lightning discharges (may cause harm at a distance of up to 20 km);

  - the influence of inductance (manifested when the neutral is short-circuited, especially in networks with long cable connections).

VARISTOR AS THE BASIS OF A SURGE REDUCER

The main component of the OPN-6 surge arrester is undoubtedly a varistor. A varistor is a resistor whose resistance depends on the voltage applied across it. It has a symmetrical current-voltage characteristic. The resistance value decreases with increasing voltage, and when an overvoltage occurs, a sharp decrease in resistance occurs (“short circuit” mode). Connected in parallel with the electronic device or circuit to be protected, the varistor serves as a low-resistance shunt, limiting the voltage and preventing it from increasing further. The varistor protects against overvoltages of all kinds and thus protects electronic equipment from failure. With the response time of a semiconductor protective diode or zener diode, the metal oxide varistor is one of the most advanced protective devices.

When a high-voltage pulse occurs, the resistance of the varistor decreases sharply to fractions of an ohm and shunts the load, protecting it and dissipating the absorbed energy in the form of heat. In this case, a pulsed current can flow through the varistor, reaching several thousand amperes. Since the varistor is practically inertialess, after the disappearance of the interference, its resistance again becomes large. Thus, the inclusion of a varistor in parallel with the protected device does not affect the operation of the latter under normal conditions, but dampens dangerous voltage pulses

DESIGN AND OPERATING PRINCIPLE OF OPN-6 OVERVOLTAGE REDUCER

Surge arrester OPN-6 incorporates the following main elements: a block of varistors, electrodes, a fiberglass pipe, a shirt made of track-erosion-resistant rubber, and conclusions. Varistors are the basis of the OPN-6 surge arrester. They are made from zinc oxide with the addition of other metal oxides by pressing. After pressing, the ends of the cylindrical varistors are metallized by aluminum sputtering, and the side is covered with a dielectric glaze. The operation of other devices depends on the current-voltage characteristics of the varistors of the OPN-6 surge arrester. OPN-6 surge arrester electrodes are an intermediate link between varistors and apparatus outputs. The terminals are intended for fastening the surge arrester to current-carrying conductors and to ground wires.

TESTING OF LIMITERS OPN-6 FOR TRACKING AND EROSION RESISTANCE

To check surge arresters OPN-6 for tracking erosion resistance, tests are carried out . Tests related to tracking erosion resistance are carried out on fully assembled devices. The tests shall be carried out in a chamber equipped with a high voltage input, supplied with a conductive water supply, with high air humidity. The dimensions of the chamber must be such that the distance from the OPN-6 surge arrester to the walls of the chamber is at least 0.6 m. When testing the surge suppressor OPN-6, a voltage of 5 kV must be applied to its jacket. For testing apparatuses, a transformer is required that creates a leakage current.

The determination of the tracking-erosion resistance in the OPN-6 surge arrester is carried out in an aqueous solution of CaCl2 with a concentration of 250 g/l. During testing, the humidity of the air must be at least 90%. Voltage to the insulating surface of the OPN-6 surge arrester must be applied in steps of 20% of the value of the tested voltage for periods of at least 3 minutes.

When partial discharges are attenuated, additional moistening of the jacket of surge arresters OPN-6 with a CaCl2 solution should be carried out, with the voltage turned off for no more than 5 minutes. Additional humidification is carried out no more than 8 hours after the voltage relaxation.

Since surge arresters OPN-6 of our production are designed to work in an atmosphere with 4 degrees of pollution, the tests must be carried out for 500 hours. During the test, it is allowed to take breaks, but not more than 24 hours, provided that the humidity is maintained at least 80%. Every 8 hours, it is allowed to remove voltage from the shirt of the OPN-6 surge arrester for inspection. The duration of the break should not exceed one hour. If, as a result of tests, no damage was noted on the surface of the surge arrester jacket or no defects were found as a result of control tests, the OPN-6 surge arrester is considered to have passed the test.

STORAGE OF OPN-6 OVERVOLTAGE REDUCERS

Manufactured surge arresters OPN-6 can be stored both in packaging and without it. The devices should be stored in rooms where the values of humidity and temperature do not differ significantly from the values of temperature and humidity of the air outside.

The design of surge arresters OPN-6 allows their storage even on the street, the main requirement is that there is protection from precipitation in the form of canopies. There are also no special requirements for the ambient temperature, the main thing is that it be in the range from -50 to + 50 ° С. If surge arresters OPN-6 are planned to be stored for a long period, then every two years it is necessary to re-preserve the devices. Only the metal parts of the apparatus are subject to preservation. Preservation is carried out with CIATIM lubricant.

After receiving the surge arrester OPN-6, we analyze it, carry out tests, if the data obtained during the measurements of its characteristics are beyond the permissible limits, we will send you a new surge arrester OPN-6.

We deliver orders throughout Ukraine, except temporarily occupied territories and war zones. Delivery is carried out by transport and logistics companies chosen by you.

The terms of delivery of the order depend on the availability of goods in the warehouse. If at the time of placing the order, all the selected goods are available, then we will deliver the order within a few days, depending on the remoteness of your region. If the ordered product is not in stock, the maximum delivery time of the order may be several weeks. But we try to deliver orders to customers as quickly as possible, and 90% of customer orders are shipped within the first almost immediately. In the event that part of the goods from your order did not arrive at the warehouse after the specified period during the discussion with the manager, we will definitely inform you about it.

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