Cathodic protection stations in the energy meter operation. Rectifiers automatic for cathodic protection in-op. Ukzt-a cathodic protection device diagram

Well-known cathodic protection transformer station with automatic adjustment of output current and potential. Produced by NPP ”Don”, Rostov-on-Don.

Cathodic protection device UKZT-A is designed for cathodic protection of underground metal objects from electrochemical corrosion.

In terms of its design, dimensions, energy parameters, the UKZTA device is similar. The only difference is that the UKZT-A station operates in modes of automatic maintenance (stabilization) of the output current or potential.

The advantages and disadvantages are the same as those of other cathodic protection.

Advantages - simplicity of circuit and design. As a rule, the maintenance personnel of gas facilities are independently capable of repairing these stations. The maximum that operators require from the manufacturer is new control boards. Sometimes they repair the control boards themselves.
Disadvantages - typical: heavy weight, dimensions, low efficiency, low power factor, high ripple level ...

Technical characteristics of UKZT-A cathodic protection stations.

Parameter	UKZT-A OPE (UKZT-AU)
Parameter	0,3	0,6	1,2	3,0	5,0
Rectified current, A - mode 1 - mode 2	25±2.5 12 ± 1.2	25±2.5 12 ± 1.2	50±5 25±2.5	63 ± 6.3 32±3.2	100±10 50±5
Rectified voltage, V - mode 1 - mode 2	12 ± 1.2 25±2.5	24±2.4 48 ± 4.8	24±2.4 48 ± 4.8	48 ± 4.8 96 ± 9.6	48 ± 4.8 96 ± 9.6
Output power, kW	0.3 ± 0.03	0.6 ± 0.06	1.2±0.1	3.0±0.3	5.0±0.5
Power supply - single-phase AC network: voltage, V frequency, Hz	220±22 50±1.25
Power consumption, kVA, no more	0,34	0,86	1,71	4,3	7,14
Efficiency in nominal mode, %, not less	70
Power factor in nominal mode, not less than	0,7
Rectified voltage range, %	5 … 100
Output current stabilization accuracy, %	±2.5
Protection potential stabilization accuracy, %	±2.5
Protective potential stabilization range, V	- 3,5 … 0
Climatic performance	U1 according to GOST 15150
Weight, kg, no more	25	55 (62)	55 (62)	60 (75)	65 (80)
Overall dimensions, mm, no more	400x320x500		450 x 380 x 600 (450 x 380 x 830)
Mounting dimensions, mm	385 x 270 D 12.5 (4 holes)

Device design.

The UKZT-A type cathodic protection station consists of a metal case, inside of which, on a folding panel, there are: a power transformer, a control board, a diode bridge, and an instrument panel.

Cooling device - natural air. Cooling air enters through louvers at the base of the cabinet and exits through louvers on the side walls.

Scheme of the cathodic protection device UKZT-A.

The power part of the cathodic protection station UKZT-A is made according to the scheme of a single-phase bridge rectifier with two control thyristors.

Schematic diagram of the UKZT-A station.

The control board works on the principle of a phase-pulse thyristor controller with stabilization of the output current and potential.

Schematic diagram of the control board of the UKZT-A station.

The control scheme consists of the following nodes:

reference voltage generator (VT3, VT4);
comparison element (DA1);
pulse generator (DD1);
comparison amplifier (DA2.2);
current signal amplifier (DA2.1);
potential signal amplifier (DA2.3, DA2.4);
board power regulator ± 10 V (VT1, VT2).

The control board is powered by 2 x 15 V AC from transformer T2. The voltage from the transformer winding is rectified by the VD1 bridge, smoothed by the capacitors C1, C2, and stabilized by the zener diodes VD2, VD4. To increase the load capacity, emitter followers VT1, VT2 are used, at the output of which voltages + 10 V and - 10 V are formed, which are necessary to power the entire circuit.

Rectified unsmoothed voltage through the divider R11, R12, R6 is fed to the input of the inverter DD1.1. As a result, short pulses of positive polarity are generated at its output, corresponding to the moments when the mains voltage passes through 0. The pulses are used to synchronize the control device with the mains.

A reference current source is assembled on transistor VT3, LED VD5 and resistor R8. This current charges the capacitor C4. At the moments when the mains sinusoid passes through 0, the pulses from the output of the element DD1.1 open the bit key VT4. Thus, a sawtooth voltage with an amplitude of -4 V is formed on the capacitor C4, synchronized with the phase of the supply network.

A comparator is assembled on the operational amplifier DA1. A reference sawtooth voltage is supplied to one of its inputs from the capacitor C4. The other input is supplied with voltage from the output regulator R5 (in manual mode), or voltage from the output of the comparison amplifier DA2.2 (in automatic mode). At the output of the comparator DA1 rectangular pulses of adjustable duration are formed. The beginning of the pulses coincides with the moment when the reference voltage becomes greater than the comparison voltage, and the end of the pulse coincides with the end of the half-cycle of the network. When the comparison voltage changes from 0 to -4 V, the pulse duration changes from maximum to minimum. To improve noise immunity, pulses are fed from the output of the comparator RS trigger (DD1.2, DD1.3). The other input of the trigger receives reset pulses from DD1.1. A low signal level at the trigger output corresponds to the presence of a pulse at the input of the comparator.

A low signal level at the trigger output allows the generator to work (DD1.4, DD1.5). It generates short pulses of 10 µs with a period of 10 kHz. The pulses through the element DD1.6 are fed to the base of the transistor VT5, which controls the optothyristors VD11, VD12.

Because the beginning of the pulse train corresponds to the moment when the reference voltage of the comparator exceeds the comparison voltage, then the switching phase of the thyristors VT1, VT2 depends on the comparison voltage. And hence the average value of the voltage across the load. By changing the comparison voltage with resistor R5, you can adjust the voltage across the load.

In automatic mode, to stabilize the current or potential, it is necessary to set the comparison voltage in proportion to the difference between the given parameter and the real one. This is done using the comparison amplifier DA2.2. A predetermined voltage from resistor R5 is supplied to one input of the amplifier, and a voltage proportional to the stabilization parameter is supplied to the other. The output voltage of the comparison amplifier is supplied to the comparator DA1.

The current measuring amplifier DA2.1 amplifies the voltage of the current shunt RS and feeds it to the comparison amplifier DA2.2.

The potential signal amplifier is made according to the scheme with compensation of common-mode interference with voltage up to 200 V. The DA2.4 amplifier is an amplifier with a differential input. The DA2.3 amplifier compares the measurement input voltage with the station ground voltage and generates a compensating voltage at the DA2.4 inputs.

Telemechanics for UKZT-A stations.

To work with UKZT-A devices as part of the GSM telemetry system, controllers are required that allow connection directly to the output and current shunt of the station. Such controllers are manufactured by NPP SIEL, Novocherkassk.

The controllers allow not only to transfer the parameters of the station operation to the control room, but also to control the operation of the station.

Passport of cathodic protection device UKZT-A.

V-OPE-TM rectifiers are designed for cathodic protection of underground metal structures against electrochemical corrosion.

Automatic stabilization and maintenance of protective current and potential at a given level. The output voltage ripple factor is not more than 3%.

Application area

Enterprises of various types of activities that have underground metal structures: main pipelines (gas pipelines, oil pipelines, product pipelines and other pipelines for various purposes), public utilities, storage tanks and other similar objects located in various soils, incl. in soils with increased aggressiveness, as well as in areas affected by stray currents from rail electric vehicles.

Specifications of V-OPE-TM Rectifiers

Name of parameters	V-OPE-25-24-U1	V-OPE-42-24-U1	V-OPE-42-48-U1	V-OPE-63-48-U1	V-OPE-84-48-U1	B-OPE- 104(100)-48-U1
	2	3	4	5	6	7
1. Output rated power, kW	0,6	1,0	2,0	3,0	4,0	5,0(4,8)
2. Rated rectified current, A	25	42	42/24	63/33	84/42	104(100)/52(50)
3. Rated rectified voltage, V	24	24	48/96	48/96	48/96	48/96
4. Efficiency, in nominal mode, not less than, %	78	83	87	88	87	90
5. Power factor in nominal mode, not less than	0,8
6. Voltage of a single-phase supply network, V	220(-70/+50)
7. Rated frequency of the supply network, Hz	50±3
8. Number of phases	1
9. Adjustment range of rectified current and voltage, %	0...100
10. Adjustment range of the protective potential setting, V	-0,5...-3,5
11. Current ripple at the output with a filter, no more than, %	3
12. Number of automatic activations, times	2 to 6
13. Stability of current or potential,%	±2.5

Design features of V-OPE-TM rectifiers

The circuit design of V-OPE-TM1 and V-OPE-TM2 rectifiers is the same. This version of the design of the rectifiers provides for the use of them:
- as a standalone product
- in systems equipped with a telemechanics complex (adapted to work with various telemechanics options).
Rectifier V-OPE-TM-1, climatic version U, location category 1, designed for outdoor installation.
Rectifier V-OPE-TM-2, climatic version U, location category 2, is designed for installation in switchgears for cathodic protection (UKZV and UKZN) and other enclosed spaces.
Degree of protection against contact with current-carrying parts and from environmental influences IP34, and built-in electronic components IP44 according to GOST 14254-96.
Rectifiers can be connected to various telemechanics systems for remote control and monitoring:
- values of the measured potential difference, output voltage, output current;
- accumulative metering of consumed electricity;
- remote setting of the protective potential (in the automatic mode of maintaining the protective potential);
- remote installation of protective current (in automatic mode of stabilization of protective current);
- remote setting of the rectifier output voltage (in manual mode of setting the output voltage);
- unauthorized access inside the rectifier.
The V-OPE rectifier is adapted to the main telemechanics systems: UNK-TM, Magistral2, STN-3000, SuperRTU4, SKAT, ELSI-2000, TELUR.
Stable operation in climatic zones in a wide range of ambient temperatures: from minus 45°С to +45°С.
Increased protection against mechanical damage. The thickness of the steel case is 2mm.
Powder coating significantly improves the corrosion resistance of the case.
The special, vandal-resistant design of the locks ensures a snug fit of the outer door and protection against unauthorized access.
Reliable tamper alarm system.
Increased technical resource up to 100,000 hours, service life up to 20 years.

Additionally, an operating time counter is installed, indicating the time the power supply voltage is applied to the rectifier and the rectifier is in the on state.

Set:

The V-OPE rectifier is supplied with a copper sulfate reference electrode ENES-1, ENES-MS-2.

V-OPE-TM rectifiers provide:

The specified electrical parameters when the supply voltage changes from 176V to 242V, as well as the performance when the supply voltage changes from 150V to 270V.
Automatic inclusion in operation in the set mode at loss and reappearance of mains voltage (during interruptions in power supply).
Removal of stray currents from the protected structure to the anode ground electrode system (drainage of currents) in the absence of mains voltage.
Stable operation during load dump and surge.
Effective protection against overloads and short circuits in the load circuit.
Efficient protection against atmospheric (lightning) surges from the supply voltage and load inputs.
Accounting for the time of the presence of a protective potential on the structure, the value of which is not less than the specified one.
Economical energy consumption due to high energy performance and cumulative electricity metering by a built-in electronic meter.
Low level of radio interference, not exceeding the values established by GOST R51522-99.

V-OPE rectifiers can operate in the following modes:

automatic maintenance of the measured potential difference at a given level in the range of values from minus 0.5V to minus 3.5V;
automatic maintenance of the protective current (stabilization of the output current);
manual setting of output voltage (current);
uncontrolled rectifier;
adjustable rectifier;
adjustable output current (voltage) stabilizer;
cyclic interruption of the load current, for measuring the polarization potential, according to the signals of the telemechanics system or from the built-in timer.