RU2706344C2 - Method of protection of technical devices in explosion hazardous areas from static electricity without shunting of cathodic protection potential - Google Patents

Abstract

FIELD: electrical equipment.

SUBSTANCE: invention relates to the electrical equipment. Invention is based on the task of developing a method of protecting technical devices in explosive areas from static electricity without shunting the potential of cathodic protection, which will make it possible to ensure safety of operation of technical devices in explosion hazardous areas without considerable increase of current density in cathodic protection system. Physics of the invention consists in increasing the introduced resistance to the grounding circuit by series connection of the active resistance, wherein the resistance rating is selected so as to ensure the following conditions: static charge draining from the technical device; maximum reduction of current density in the cathode protection system flowing through the grounding circuit.

EFFECT: present invention can further be implemented in form of active resistance (wire resistor) arranged in tight explosion-proof housing, to which a resistor with a thermal switch can be connected in parallel to compensate for increasing resistance of the grounding device during soil freezing by parallel connection of resistance at temperature reduction, as well as integrating circuit for floating of alternating component and protective element against overvoltage.

2 cl, 1 dwg

Description

A method of protecting technical devices in hazardous areas from static electricity in which static electricity flows from a protected technical device to an earthing device, characterized in that it increases the impedance of the ground circuit by sequentially including active resistance, thereby reducing the current density of the cathodic protection system flowing down grounding system.

State of the art

To increase the service life of underground gas pipelines using cathodic protection systems, they form a constant negative potential of about 1 V.

For installation on pipelines of technical devices (technological valves, purge plugs, etc.), it is usually taken out, where an explosive zone is formed.

As a result of friction during transportation of explosive atmospheres, the indicated technical devices generate an electrostatic charge, the electrical breakdown of which can lead to fire.

Currently, to protect these technical devices from static electricity, they are grounded by direct connection to the grounding device of the object, which leads to a significant increase in currents and instability of the operation modes in the cathodic protection system due to seasonal changes in the resistance of the grounding device.

A known method of preventing the accumulation of electrostatic charges in emulsions during oil production and transportation (RU (11) 2488627 (13) C1). The invention relates to a method for preventing the accumulation of electrostatic charges in emulsions during oil production and transportation using neutralizing devices, while at the stage of oil collection, antistatic surfactants are introduced into the well, and later, demulsifiers are dosed at the stage of oil preparation. Its disadvantage is the complexity and high cost of implementation.

A known method of preventing the formation of static electricity, based on the use of a device in which a three-phase stator creates a rotating magnetic field and an additional stationary electric field between the input metal pipe and the discharge metal strings (RF Patent No. 2351100. A method of neutralizing static electricity in a substance flow).

The disadvantage of this method is that it requires energy to create an additional stationary electric field, the device has large overall dimensions and can be mounted only at the entrances to the tanks.

A known method of preventing the accumulation of electrostatic charges using devices to neutralize static electricity, which uses the principle of corona discharge [High-voltage converter of static electricity IZN1 Company "SMC Corporation", converter of static electricity ZAO "Bearing-service"]. The disadvantage of this method is the energy consumption for the ionization of the medium, as well as the inability to use these devices in production systems and pipeline transport of hydrocarbons. This method is especially dangerous in explosive facilities due to the threat of ignition of an explosive atmosphere.

The closest in technical essence and the achieved result is a method of preventing the accumulation of electrostatic charges using a static charge converter in a liquid (RF Patent No. 1355100. A static charge converter in a liquid), in the neutralization chamber of which there is a rod discharge electrode with needles. The neutralization process occurs due to ionization processes developing near the discharge electrode and needles in the presence of a significant potential difference between the liquid filling the chamber and the discharge electrode.

The disadvantage of this technical solution is that with a slight potential difference between the liquid and the discharge electrode, i.e. at low values of electrification of the emulsion, the neutralization process will not occur. The use of neutralizers does not prevent the phenomenon of electrification of oil, but only allows you to remove from the oil-water mixture already generated electrostatic charges.

The basis of the invention is the task of developing a method of protecting technical devices from static electricity without shunting the potential of cathodic protection, which will ensure the safety of operation of technical devices in hazardous areas while ensuring a decrease in current density in the cathodic protection system.

The physics of the action of the invention consists in grounding technical devices through active resistance, and the resistance rating is chosen so as to provide conditions:

- runoff of static charge from a protected technical device;

- maximum reduction of current density in the cathodic protection system flowing through the ground circuit.

The operation of the device is illustrated in figure 1. The active resistance circuit 1 (can be implemented as a wire resistor) provides a drain of static charge from the protected technical device 2. The active resistance circuit 3 (resistor) with a thermal switch 4 connected in parallel provides compensation for the increase in the resistance of the grounding device when freezing of the soil by the parallel inclusion of resistance at lower temperatures. The integrating circuit 5 provides minimal resistance for the draining of the variable component (induced currents) to the grounding device to ensure electrical safety. The protective element 6 against overvoltage (discharger, varistor, protective diode) provides suppression of overvoltage when exposed to interference caused by lightning discharges and short circuits. According to the PUE, the grounding device cannot have high values of capacitance and inductance, therefore, in the calculations, the reactive component can be neglected.

Technical results are achieved in that, in contrast to the direct connection of the technical device with the grounding system, this invention prevents the increase in current density in the cathodic protection system.

Information sources

1. RD 39-22-113-78 “Temporary rules for protection against manifestations of static electricity in industrial plants and oil and gas industry”.

2. STO Gazprom 9.0-001-2009 “Protection against corrosion. Design of electrochemical protection of underground structures. ” Open Joint Stock Company Gazprom.

3. Electrical Installation Rules, Edition 7.

4. GOST 12.1.030-81 Electrical safety. Protective grounding, grounding.

Claims (2)

1. A method of protecting technical devices in hazardous areas from static electricity, in which a static charge is drained from the protected technical device to a grounding device, characterized in that the total resistance of the ground circuit is increased by sequentially switching on the active resistance, thereby reducing the current density of the system cathodic protection flowing into the grounding system. 2. The device for implementing the invention according to claim 1, comprising an earth circuit of the protected technical device, characterized in that an active resistance is connected in series, to which a resistor with a thermal switch can be connected in parallel to compensate for the increase in the resistance of the grounding device during freezing of the soil, as well as an integrating circuit for dripping of a variable component, and a protective element against overvoltage, while the device is made in a sealed explosion-proof housing.

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