RU64990U1 - ELECTRICAL TERMINAL GROUNDING BUS - Google Patents

Abstract

The utility model “Grounding bus with an electrical threshold of connection” is intended for connecting the enclosures of electrical equipment of pipeline transport facilities subject to cathodic protection against corrosion to protective grounding. Widely used metal grounding buses are known for connecting electrical equipment enclosures to protective earth. At facilities subject to cathodic protection against corrosion (oil, gas, product pipelines, tanks, etc.), protective earths connected to the valve body of the valves and pumps, tanks, etc. using metal tires, impede the normal operation of the electrochemical protection of objects. Metal buses divert most of the protection current to the ground and, as a result, shorten the life of the anode earthing switches of the cathodic protection stations and protectors; reduce the value of the protective potential of the object to an unacceptable value; make it difficult to diagnose the state of the protective coating of pipelines and tanks. To exclude undesirable effects on the protected objects, the bus is made integral, at least one part of the bus is a metal conductor, and the other part, connected in series with the metal conductor, is a threshold device that connects the protected object to protective ground when it reaches the magnitude of the voltage on the object casing of the set threshold value. The grounding bus with an electrical connection threshold (SHZEPP) consists of a metal conductor 1 and semiconductor diodes 2 and 3 connected in opposite-parallel fashion. For the assembly of ShZEPP, mounting contacts 4 are used. It is allowed to use welding instead of bolted joints when installing ShZEPP. The threshold device 5 is, in the particular case, two semiconductor diodes placed in the housing. In other versions of the threshold devices, instead of diodes, dynistors, thyristors, as well as low voltage arresters are used. Using the utility model allows to prevent the diversion of most of the protection current to the ground; extends the service life of the tread or anode ground electrodes of cathodic protection stations; eliminates the reduction in the value of the protective potential of the object to an unacceptable value due to grounding of objects; facilitates the diagnosis of the protective coating of pipelines and tanks.

Description

Grounding bus with electrical connection threshold. MPC-7 rubric index

The technical field to which the utility model belongs.

The utility model relates to electrical engineering and can be used in devices containing electrical equipment to be earthed.

The level of technology.

Widely used metal grounding buses are known for connecting electrical equipment enclosures to protective earth. At facilities subject to cathodic protection against corrosion (oil, gas, product pipelines, tanks, etc.), protective earths connected to the valve body of the valves and pumps, tanks, etc. using metal tires, impede the normal operation of the electrochemical protection of objects. The following disadvantages are inherent in metal tires used in facilities subject to cathodic corrosion protection:

- divert most of the protection current to the ground and, as a result, shorten the life of the anode earthing switches of the cathodic protection stations and protectors;

- reduce the value of the protective potential of the object to an unacceptable value;

- make it difficult to diagnose the state of the protective coating of pipelines and tanks;

In addition, at facilities subject to cathodic protection against corrosion, there are contradictions between the requirements for the cathodic protection potential of pipelines and tanks (clause 5.1 of GOST R 51164-98) and the requirements of clause 3.3 of GOST 12.2.007.0-75, clause 1.7. 49 of the Rules of the Electrical Installation Device (ПУЭ) on mandatory protective grounding to prevent the possibility of hazardous voltage appearing on objects in the event of an accident or lightning overvoltage.

A typical connection diagram of protective earth to the valve body of the valve using a metal bus is shown in figure 1.

The essence of the utility model.

The utility model was created with the aim of expanding the operational capabilities of the grounding bus due to the implementation of its composite. At least one part of the grounding bus with an electrical connection threshold (SHZEPP) is a metal conductor, and the other part, connected in series with a metal conductor, is a threshold device (PU), which connects the protected object to protective ground when

the achievement of the voltage value on the object body of the established threshold value.

A conventional metal grounding bus directly connects the enclosures of the electrical equipment to the ground electrode, which is undesirable, since the protective current of the tread or cathodic protection station (SCZ) connected by one pole to the protected object is closed through a relatively small ground resistance to the other pole. Most of the protection current is not spent on protecting the facility, but is a waste of energy. In addition, the protection current destroys the tread or anode ground of the cathodic protection station. Grounding conductors directly connected with the objects of protection make it difficult to diagnose the state of the insulation coating of objects and reduce the value of the protective potential to an unacceptable level. A threshold device that connects the protection objects to the ground electrode when the voltage value on the object casing reaches the set threshold value, eliminates these disadvantages. Under normal (operating) voltage on the protected object, the protection current is spent almost exclusively on protecting the metal of the object from corrosion.

The use of a composite bus with an electrical connection threshold allows achieving several technical results:

- prevents the removal of most of the protection current to the ground;

- extends the service life of the tread or anode grounding conductors of cathodic protection stations;

- eliminates the reduction in the value of the protective potential of the object to an unacceptable value due to grounding of objects;

- facilitates the diagnosis of the protective coating of pipelines and tanks.

The use of SHZEPP eliminates the contradiction between the requirements for the potential cathodic protection of pipelines and reservoirs (Clause 5.1 GOST R 51164-98) and the requirements of Clause 3.3 GOST 12.2.007.0-75, clause 1.7.49 of the PUE on mandatory protective grounding to prevent the possibility of occurrence dangerous voltage at the facilities in the event of an accident or lightning overvoltage.

The list of figures drawings.

The drawings are presented on two sheets.

The drawings show:

Figure 1. Connection diagram of protective earth to the body of the pipeline valve motor.

Figure 2. Grounding bus with electrical connection threshold. The circuit is electrical in principle.

Figure 3. Current-voltage characteristic of a semiconductor diode.

Figure 4. Current-voltage characteristic of a pair of diodes connected in counter-parallel.

Figure 5. Electrical schematic diagram of a threshold device.

Figure 6. Current-voltage characteristic of the threshold device.

Information confirming the possibility of implementing a utility model.

The grounding bus with an electrical connection threshold (Fig. 2) consists of a metal conductor 1 and semiconductor diodes 2 and 3 connected in counter-parallel. For the assembly of ShZEPP, mounting contacts 4 are used. It is allowed to use welding instead of bolted joints when installing ShZEPP. The threshold device 5 is, in the particular case, two semiconductor diodes placed in the housing.

Consider the operation of a threshold device. Known current-voltage characteristic of a semiconductor diode (figure 3).

The voltage U _{d of} positive polarity applied to the diode causes the current to increase through the pn junction not from zero, but when a certain value is called a threshold voltage (U _pore ). For silicon diodes, U _then has a value of the order of 0.7 V. When the diodes are turned on in parallel, the current-voltage characteristic acquires a symmetrical character (Fig. 4).

The threshold voltage (U _pu ) is determined by the type and number of diodes or threshold devices connected in series. Schematic diagram of PU shown in Fig.5.

The diagram shows the options for sequentially switching on threshold devices consisting of pairs of on-parallel connected diodes or diode circuits connected in series. Current-voltage characteristic of the threshold

a device consisting of several pairs of counter-parallel connected diodes or diode circuits, shown in figure 6.

At normal (operating) voltage at the protected object, the protective potential ( _Upr ) is less than U _pu , the current in the protective ground circuit is practically absent, and the protection current is spent only on maintaining the _{Uprot of the} object. In the event of an emergency at the protected facility (insulation breakdown or atmospheric overvoltage), the voltage rises to U _pu , the pn junctions of the diodes are opened for electric current and there is no dangerous voltage at the protected facility. The maximum current of the diodes is selected on the basis of the maximum operating current of the protection of the cable power line of the motors connected to this SHZEPP.

Because electric motors operate on alternating current, counter-parallel connection of diodes is used to exclude the possibility of life-threatening voltage at the object with a certain polarity of the supply voltage. The maximum value of U _PU does not exceed 42 V in accordance with the requirement of GOST 12.2.007.0-75. In other versions of the threshold devices, instead of diodes, dynistors, thyristors, as well as low-voltage arresters are used.

Bibliographic data.

1. GOST 12.2.007.0-75. Interstate standard. Occupational safety standards system. Electrotechnical products. General safety requirements. The publication is official. Moscow, IPK Standards Publishing House, 2003

2. GOST R 51164-98. The publication is official. Moscow, Standards Publishing House, 1998

3. Rules for the installation of electrical installations. 7th edition. Moscow, publishing house NTs ENAS, 2002

Claims (1)

A grounding bus with an electrical connection threshold, designed to connect the enclosures of pipeline transport electrical equipment to protective grounding, characterized in that in order to save energy spent on cathodic protection of objects, increase the service life of protectors and anode grounding conductors of cathodic protection stations, and prevent a decrease in the value of protective potential by grounded areas below the set level and facilitate the diagnosis of the condition of the protective coating, the bus is made at the same time, at least one part of the bus is a metal conductor, and the other part, connected in series with a metal conductor, is a threshold device that connects the protected object to protective ground when the voltage value on the object’s body reaches a value not lower than the maximum standard the value established by the requirements of cathodic protection and not higher than the normative value established by the requirements of electrical safety.