Well-known cathodic protection transformer station with automatic adjustment output current and potential. Produced by the Don Research and Production Enterprise, Rostov-on-Don.
The UKZT-A cathodic protection device is intended for cathodic protection of underground metal objects from electrochemical corrosion.
In its design, dimensions, and 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, gas service personnel are able to independently repair these stations. The maximum that operators require from the manufacturer is new control boards. Sometimes they repair control boards themselves.
- Disadvantages - typical: heavy weight, dimensions, low efficiency, low power factor, high level pulsations...
Technical characteristics of UKZT-A cathodic protection stations.
| Parameter | UKZT-A OPE (UKZT-AU) | ||||
| 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 network AC: voltage, V frequency, Hz | 220 ± 22 50 ± 1.25 |
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| Power consumption, kV●A, 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 | 0,7 | ||||
| Range of changes in rectified voltage, % | 5 … 100 | ||||
| Output current stabilization accuracy, % | ± 2.5 | ||||
| Accuracy of protective potential stabilization, % | ± 2.5 | ||||
| Range of stabilization of protective potential, V | - 3,5 … 0 | ||||
| Climatic version | U1 according to GOST 15150 | ||||
| Weight, kg, no more | 25 | 55 (62) | 55 (62) | 60 (75) | 65 (80) |
| Overall dimensions, mm, no more | 400 x 320 x 500 | 450 x 380 x 600 (450 x 380 x 830) | |||
| Installation dimensions, mm | 385 x 270 D 12.5 (4 holes) | ||||
Device design.
The cathodic protection station type UKZT-A consists of a metal casing, inside of which the following are located on a hinged panel: power transformer, control board, diode bridge, instrument panel.
The device is cooled by natural air. Cooling air enters through louvres at the base of the housing and exits through louvres on the side walls.
UKZT-A cathodic protection device diagram.
The power part of the cathodic protection station UKZT-A is made according to the circuit of a single-phase bridge rectifier with two control thyristors.
Schematic diagram of the UKZT-A station.
The control board operates on the principle of a phase-pulse thyristor regulator with stabilization of the output current and potential.
Schematic diagram of the UKZT-A station control board.
The control circuit 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 supply regulator ± 10 V (VT1, VT2).
The control board is powered by an alternating voltage of 2 x 15 V from transformer T2. The voltage from the transformer winding is rectified by bridge VD1, smoothed by capacitors C1, C2, and stabilized by zener diodes VD2, VD4. To increase the load capacity, emitter followers VT1, VT2 are used, at the output of which voltages of + 10 V and – 10 V are generated, necessary to power the entire circuit.
The rectified unsmoothed voltage through the divider R11, R12, R6 is supplied to the input of the inverter DD1.1. As a result, short pulses of positive polarity are formed at its output, corresponding to the moments when the network voltage passes through 0. The pulses are used to synchronize the control device with the supply network.
A reference current source is assembled on transistor VT3, LED VD5 and resistor R8. This current charges capacitor C4. At the moments when the sinusoid of the supply network passes through 0, pulses from the output of element DD1.1 open the bit switch VT4. Thus, a sawtooth voltage with an amplitude of 4 V is formed on capacitor C4, synchronized with the phase of the supply network.
A comparator is assembled on the operational amplifier DA1. One of its inputs receives a reference sawtooth voltage from 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 comparator DA1, rectangular pulses of adjustable duration are formed. The onset of the pulses coincides with the moment when the reference voltage becomes more voltage comparison, 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 increase noise immunity, pulses from the output of the comparator are supplied to an RS trigger (DD1.2, DD1.3). The other trigger input receives reset pulses from DD1.1. Low level The signal at the output of the trigger 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 operate (DD1.4, DD1.5). It produces short pulses of 10 μs with a period of 10 kHz. Pulses through element DD1.6 arrive at the base of transistor VT5, which controls 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 thyristors VT1, VT2 depends on the comparison voltage. This means the average 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 specified parameter and the real one. This is done using the DA2.2 comparison amplifier. One input of the amplifier receives a specified voltage from resistor R5, and the other receives a voltage proportional to the stabilization parameter. The output voltage of the comparison amplifier is supplied to comparator DA1.
The current measuring amplifier DA2.1 amplifies the voltage of the current shunt RS and supplies it to the comparison amplifier DA2.2.
The potential signal amplifier is designed according to a circuit that compensates for common-mode interference with voltages up to 200 V. The DA2.4 amplifier is an amplifier with a differential input. Amplifier DA2.3 compares the voltage of the measurement inputs with the ground voltage of the station and generates a compensating voltage at the inputs of DA2.4.
Telemechanics for UKZT-A stations.
To work with UKZT-A devices as part of a GSM telemetry system, controllers are required that can be connected directly to the output and current shunt of the station. Such controllers are produced by NPP SIEL, Novocherkassk.
Controllers make it possible not only to transmit station operating parameters to the control center, but also to control the operation of the station.
Certificate of cathodic protection device UKZT-A.
V-OPE-TM rectifiers are designed for cathodic protection of underground metal structures from electrochemical corrosion.
Automatic stabilization and maintenance of protective current and potential at a given level. The output voltage ripple factor is no more than 3%.
Scope of application
Enterprises various types 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 exposed to stray currents from electric rail vehicles.
Technical characteristics of Rectifiers V-OPE-TM
| 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 | V-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 | 0,8 | |||||
| 6. Single-phase supply voltage, 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. Range of regulation of the protective potential setting, V | -0,5...-3,5 | |||||
| 11. Current ripple at the output with filter, no more than, % | 3 | |||||
| 12. Number of automatic starts, times | From 2 to 6 | |||||
| 13. Current or potential stability, % | ±2.5 | |||||
Design features of V-OPE-TM rectifiers
- The circuit design of the V-OPE-TM1 and V-OPE-TM2 rectifiers is the same. This version of the design of rectifiers provides for their use:
- 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 placement category 1, intended for installation outdoors.
- Rectifier V-OPE-TM-2, climatic version U placement category 2, designed for installation in switchgears for cathodic protection (UKZV and UKZN) and other enclosed spaces.
- Degree of protection against contact with live parts and impact environment IP34, and built-in electronic components IP44 according to GOST 14254-96.
- The rectifiers have the ability to connect to various telemechanics systems for remote control and monitoring:
- the magnitude of the measured potential difference, output voltage, output current;
- cumulative metering of consumed electricity;
- remote installation of the protective potential (in automatic mode of maintaining the protective potential);
- remote installation of protective current (in automatic protective current stabilization mode);
- 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”, “SupeRTU4”, “SKAT”, “ELSI-2000”, “TELUR”.
- Stable operation in climatic zones over a wide range of ambient temperatures: from minus 45°C to +45°C.
- Increased protection against mechanical damage. The thickness of the steel case is 2mm.
- Powder coating significantly increases the corrosion resistance of the housing.
- The special, vandal-resistant design of the locks ensures a tight fit of the outer door and protection from unauthorized access.
- Reliable alarm system against unauthorized access.
- The technical resource has been increased to 100,000 hours, service life to 20 years.
Additionally, an operating time counter is installed, indicating the time the supply voltage is supplied to the rectifier and the rectifier is in the on state.
Set:
The V-OPE rectifier is supplied complete with a copper-sulfate reference electrode ENES-1, ENES-MS-2.
V-OPE-TM rectifiers provide:
- Specified electrical parameters when the supply voltage changes from 176V to 242V, as well as operability when the supply voltage changes from 150V to 270V.
- Automatic activation in a given mode when the mains voltage disappears and reappears (during power outages).
- Drainage of stray currents from the protected structure to the anode grounding conductor (current drainage) in the absence of supply voltage.
- Stable operation during load shedding and loading.
- Effective protection against overloads and short circuits in the load circuit.
- Effective protection against atmospheric (lightning) overvoltages from the supply voltage and load inputs.
- Accounting for the time of presence of a protective potential on a structure, with a value not less than the specified one.
- Economical energy consumption due to high energy performance and cumulative electricity metering with 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 protective current (output current stabilization);
- manual setting of output voltage (current);
- uncontrolled rectifier;
- adjustable rectifier;
- adjustable output current (voltage) stabilizer;
- cyclic interruption of the load current, to measure the polarization potential, based on signals from the remote control system or from the built-in timer.