Valve arrester RVO-10

The RVO-10 U1 arresters are designed to protect against atmospheric overvoltage insulation of AC electrical equipment with a frequency of 50 and 60 Hz. They are made for networks with any neutral earthing system.

Specifications:
Mains voltage class, effective value, kV: 10;
Rated voltage (Unr), effective value, kV: 12.7;
Pulse breakdown voltage at pre-discharge time from 2 to 20 μs, kV, not more than: 48;
Leakage current at rectified voltage equal to the rated voltage, mA, not more than: 0.6;
The length of the leakage path of the outer insulation, cm, not less than: 447;

The valve arrester RVO-10 U1 is a protective device of a suspension-support design, which consists of a multiple spark gap and a working resistor. The multiple gap of the arrester, in turn, consists of several single, and the resistor consists of a series of wilite disks. The multiple spark gap is connected in series with the operating resistor. Hermetic porcelain case reliably protects the internal elements of the arrester from various environmental influences.
A special property of wilt is its non-linear resistance, which decreases with increasing current. It allows you to pass a large current with a smaller voltage drop. Valve arresters got their name just because of this property. The advantages of valve arresters also include noiseless operation and the absence of gas or flame emissions.

Due to the fact that vilite changes its characteristics when moistened, the resistor is hermetically sealed from the external environment. During overvoltage, a spark gap breaks through.

The purpose of the operating resistor is to reduce the value of the follow current to a value that can be successfully extinguished by spark gaps.

Requirements for arresters RVO-10 U1
After the passage of the current pulse, the spark gap turns out to be ionized and is easily broken through by the rated phase voltage. A short circuit occurs to the ground, in which a current of industrial frequency flows through the arrester, which is called accompanying.
The follow current can vary over a wide range. In order to avoid turning off the equipment from the relay protection, this current must be switched off by the arrester in the shortest possible time (about a half-cycle of the industrial frequency). The following requirements are imposed on the arresters.
The volt-second characteristic of the arrester must go below the characteristic of the protected object and must be flat;
The spark gap of the arrester must have a certain guaranteed electrical strength at industrial frequency (50 Hz) and with pulses;
The remaining voltage on the arrester, which characterizes its limiting capacity, should not reach dangerous values for the isolation of the equipment;
The follow current with a frequency of 50 Hz must be switched off in a minimum time;
The arrester must allow a large number of operations without inspection and repair.

The principle of operation of the arrester RVO-10
The operation of the valve arrester RVO-10 in normal mode is silent. The principle of operation is that under the influence of lightning and switching surges, the valve arrester RVO-10 passes currents dangerous for equipment to the ground, thereby protecting electrical equipment from failure.
The valve arrester is connected directly to the current-carrying part and to the ground, but there is no ground fault. This property is explained by the fact that in the normal mode of operation of the RVO-10 valve arrester, its electrical circuit is not closed due to the presence of gaps in the spark gaps.
When an overvoltage appears in the network, a breakdown occurs in the spark gap, thereby actuating the working resistor. Due to its non-linearity, the working resistor sharply reduces its resistance and passes current through itself to ground, blocking the path to the equipment.

Diagnostics of arresters RVO-10
The serviceability of valve arresters is checked during scheduled inspections: periodic tests, inspections after accidents, preventive tests, scheduled revisions, repairs. Inspections should be made after short circuits, thunderstorms and automatic shutdowns.

Possible defects of arresters
The main requirement for the arrester is the tightness of the design, since the RVO-10 valve arrester is too sensitive to the effects of moisture on its internal parts. When the spark gaps are moistened, this is reflected in a decrease in the breakdown voltage, drops accumulated in the spark gaps simply close the electrical circuit and this leads to its failure. Humidification can be caused by depressurization of the housing: damage to the porcelain jacket or loss of tightness due to loose rubber seals due to improper assembly or improper transportation. Non-linear series resistor disks are also sensitive to moisture. Due to moisture in the working resistor, the valve coefficient increases and the value of the bandwidth decreases. There are cases when moistening led to the overlap of the working resistors, and as a result, this leads to the destruction of the RVO-10 valve arrester.
Solving the problem of tightness. The tightness of the design of the RVO-10 valve arrester is ensured by a porcelain jacket and seals made of ozone-resistant rubber. These structural elements withstand vacuum pressure of -0.4 atm, thereby not letting in air that contains moisture.
RVO-10 arresters are manufactured in accordance with TU U 31.2-22820979-002:2007.

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