RU2117184C1 - Wind-electric generating plant for cathodic protection of pipelines - Google Patents

Abstract

FIELD: corrosion protection of oil, gas, and water intake wells. SUBSTANCE: current- conversion system includes polarization-voltage pulse amplitude shaping unit; pulse length is found from equation

, where τ_p is pulse length; τ_pot is time required to shape permissible potential U_max; U(t) is current value of polarization voltage. EFFECT: enlarged service life of anodic grounding electrodes. 1 dwg

Description

 The invention relates to the field of electrochemical protection against soil corrosion of underground oil and gas pipelines.

 It can also find application for the cathodic protection of oil and gas wells, water pipelines and other structures of the oil, chemical and construction industries.

 A common way to protect underground structures (pipelines, wells, etc.) from soil corrosion is through comprehensive protection using insulation coatings and cathodic polarization.

 The main parameter characterizing cathodic protection is the minimum tube-to-ground potential difference, which is minus 0.85 V for the copper-sulfate reference electrode. The maximum allowable potential difference of the pipe-to-ground circuit at the point of attachment of the negative electrode (cathode) of the current source to the pipe should be no more than minus 1.5 V, since an increase in the potential difference negatively affects the connection of the insulation coating with the pipe [1].

 Currently, the most widely used as a current source of electrochemical protection of pipelines are network current sources. However, 6-10 kV long-distance power lines (power lines) used to power cathode stations are very expensive due to their long length and difficult climatic conditions, for example, for conditions of Novy Urengoy in the Tyumen Region, 1 km of a power line cost more than 200 mil. rubles. In this regard, taking into account the significant wind energy resources of regions with an average annual wind speed of 4 m / s or more in which the pipelines are located, cathodic protection wind farms are promising, the specific cost of which for protecting 1 km of the pipeline is 1-2 orders of magnitude lower compared to network sources.

 The wind power cathodic protection station is an autonomous energy source, which is especially important in conditions of a long length of oil and gas pipelines.

 Closest to the invention in technical essence is a wind electric cathode station (VKS) [2] containing a wind wheel, a generator, a battery and a current converter.

 The principle of VKS operation is as follows: kinetic wind energy rotates a wheel with an alternator, which converts mechanical energy into electrical energy. The alternating current in the current transformer is transformed and rectified. Direct current is used for cathodic polarization, while the minus of the current source is connected to the pipeline, and the plus to the anode earthing. Due to the pulsating nature of the wind, a backup unit with a battery is provided in the VKS. The battery is charged from the converter and in calm weather it automatically performs the functions of a cathodic protection current source.

The main disadvantage of this wind farm, taken as a prototype, is its low reliability. This is due to the fact that continuous direct current electrochemical protection causes the rapid dissolution of anode grounding conductors. For example, when using a constant current of 30 A for cathodic polarization, the mass loss of the steel electrode can be 10 kg / A.year. [1]
The objective of the invention is to increase the reliability of electrochemical protection of pipelines.

 The technical result of the invention is to increase the service life of anode grounding conductors.

где
τ_и - длительность импульса;
τ_п - время формирования максимально допустимого потенциала U_м;
U_t - текущее напряжение поляризации.The task and technical result are achieved in that the cathodic protection wind farm, including a wind turbine, generator, battery pack and electric current conversion system, in contrast to the prototype, is equipped with a unit for generating the amplitude of the polarization voltage pulses, the duration of which is determined by the expression

Where
τ _and - pulse duration;
τ _p - the time of formation of the maximum allowable potential U _m ;
U _t is the current polarization voltage.

 Thus, the invention meets the criterion of "novelty."

 Using the invention will achieve a result that meets the need.

 Thus, the invention meets the criterion of "inventive step".

 The drawing shows a diagram where the unit for generating the amplitude of the pulses of the polarization voltage contains: two electronic keys 1 and 2, a control circuit for electronic keys 3, two comparators 4 and 5, two sources, a threshold voltage of 6 and 7, and a copper sulfate reference electrode 8.

 The principle of operation of the circuit for generating the amplitude of the polarization voltage pulses is as follows.

Constant voltage from the rectifier of the wind farm through an electronic switch 1 is supplied to the pipeline and anode ground electrodes. There is a polarization process. The change in the potential "pipe-soil" is controlled by a comparison electrode 8, the signal from which is supplied through a key 1 to one of the inputs of the comparator 4, to the other input of which a threshold voltage minus 1.5 V from source 6 is applied. At the moment of equal voltage U _m = U _{t the} comparator 4 generates a signal to the key management circuit 3, the signal of which breaks the circuit of the key 1, switches the circuit of the key 2 and turns off the current in the pipeline-anode earthing circuit. In this case, the duration of τ _{and the} polarization voltage pulse is equal to the time τ _{p of the} formation of the maximum allowable potential (minus 1.5 V) at the pipe-ground boundary.

 When the current is turned off in the pipe-to-ground circuit, a depolarization process occurs, causing a decrease in potential, which is controlled by the comparison electrode 8. The signal from the comparison electrode 8 is fed to one of the inputs of the comparator 5, the other input of which is supplied from the threshold voltage source 7 minus 0 , 85 V.

 At the moment of equal potentials, the comparator 5 generates a signal that breaks the circuit of the key 2 through the control circuit 3, commutates the circuit of the key 1 and returns the device for generating the amplitude of the polarization voltage pulses to the initial state.

 It is known [3] that the ratio of the time of the polarization process to the time of the depolarization process is of the order of 0.1 or less. Therefore, the use of a circuit for generating the amplitude of polarization voltage pulses makes it possible to increase the service life of anode earthing switches by 10 or more times, and therefore, the reliability of electrochemical protection compared to a wind power plant [2], adopted as a prototype.

 In the absence of wind, electrochemical protection is carried out from storage batteries. Due to the high polarization current, the battery capacity of the well-known wind-power cathode station [2], which continuously supplies the pipe-anode ground electrode circuit, lasts for a day. The use of a circuit for generating the amplitude of polarization voltage pulses will reduce the energy consumption, increase the operating time of the batteries, and thereby increase the reliability of electrochemical protection.

 In addition, the use of cathodic protection in the proposed wind farm of the unit for generating the amplitude of the polarization voltage pulses allows us to take into account seasonal changes in the electrical resistivity of the soil and automate the process of electrochemical protection of the pipeline.

 References.

 1. Instructions for the design and calculation of electrochemical protection of trunk pipelines and field facilities. -M .: VNIIST, 1980, p. 37-53.

 2. Sidorov V.V. Wind power stations for cathodic protection of pipelines. The mechanization and electrification of agriculture, N 2, 1983, S. 54-55. - prototype.

 3. Nikitenko EA Automation and telecontrol of electrochemical protection of gas pipelines. -M .: Nedra, 1976, p. 28-31.

Claims (1)

A cathodic protection wind farm including a wind turbine, a generator, a battery pack and an electric current conversion system, characterized in that the current conversion system comprises a unit for generating the amplitude of the polarization voltage pulses, the duration of which is determined by the expression

where τ _and is the pulse duration;
τ _p - the time of formation of the maximum allowable potential U _m ;
u (t) is the current polarization voltage.