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CPU functional diagram

CPU functional diagram

TVERTSA 900 pipeline cathodic protection system includes:

  • metal cabinet with a circuit breaker, electric power meter, electrical socket for power converter, lightning protector, tamper-proof controls and a group of clamp connectors;
  • power converter with controller and GSM modem;
  • dipole aerial (for TVERTSA 900 CPU);
  • Tvertsa-monitor control point software (designed for TVERTSA 900 CPU);
  • power cable;
  • cabinet lock key.

Technical solutions implemented in power converter provide high reliability and cost-efficiency and minimize CPU maintenance expenses. It was obvious that 900W impulse converter would require an effective cooling system, which was going to be the major challenge for engineers.

Technical solutions described below helped to successfully accomplish the mentioned tasks:

  1. Basic material of CPU cabinet is aluminium shape, which is also used as a cooler. This enables to maintain an appropriate temperature regime inside the cabinet without using forced ventilation in the Russian mid-latitude climate. Adding a ventilator to the cooling circuit enabled to increase CPU temperature durability. Ventilator internal control mechanism extends its service period over 10 years, which is an operational life of the unit itself.
  2. Pulse bridge converter provides high efficiency and capacity, low electromagnetic interference along with automatic protection against shot circuits, power disruptions and unit overheating.
  3. Alphanumeric LCD screen allows viewing many CPU operational parameters and helps to considerably reduce unit dimensions.
  4. Build-in active power factor corrector controls the input current so that the current waveform is close to a sine wave. It also provides minimal phase shift between the input current and voltage (power factor not less than 0.95) and ensures suppression of input current upper harmonics (as required by GOST R 51217-99 state technical standard) to the level below 60 dB at mains voltage between 170 V and 253 V.

Figure 1 shows CPU functional diagram.

CPU Specifications

  • TVERTSA 900 cathodic protection system is a third-order standard system according to GOST 12997-84 state technical standard.
  • Power supply from AC mains, 170 253V, 50 Hz 5%.
  • Operation at the mains voltage below 170V is not permitted.
  • Cathodic protection unit is a regulated 0 - 15 A DC power supply with an output voltage below 60V.
  • Manually set output current resolution 0.2 A with the output current range of 0 3A, and - 0.5A with the output current range of 3 15A.
  • Protection voltage resolution 50mV
  • Output DC accuracy 2%.
  • Protection voltage accuracy 2%.
  • Unit maximum output power P = 0.9 kW
  • Unit power factor not less than 0.95
  • Unit efficiency > 85 % at network voltage of 220V
  • Unit input resistance in the protection voltage circuit 1.5 MO
  • Cathodic protection unit stands up well to repeated short circuits and power disruptions
  • CPU regulates current and voltage
  • CPU is equipped with automatic overheating protection at the temperature over 75 °
  • CPU is equipped with an automatic break system at the network voltage exceeding 253V
  • Cathodic protection unit is designed for 24-hour operation
  • Cathodic protection unit is a repairable and maintainable system
  • Unit dimensions 300 x 555 x 555
  • Power converter dimensions - 200x125x420
  • Unit weight converter + cabinet not more than 40 kg
  • Power converter weight not more than 12 kg
  • Increase of power can be achieved by combining two CPUs
  • Unit service life 10 years

Communication Channel and CPU Control System

GSM channel using 900/1800 mHz has been chosen as a communication channel. Today this type of communication is available in majority of Western Russia regions. Besides, with GSM channel there is no need to create extra communication channels, which considerably reduces production costs of the CPU automated control systems.

Communication between the CPU (controlled part) and a control point is made in the following way:

  1. The control point establishes connection with the CPU through a phone call and transmits all required information (setting parameters, operational programme and information enquiry) to the CPU. At the same time the CPU passes all required details to the control point.
  2. The CPU sends SMS messages to the control point.

This type of communication procedure has been chosen because it allows the control point to work in a flexible mode (24-hour operation is not required) while the CPU can transmit messages, such as emergency messages, in a non-stop mode.

Remote control is currently available for:

  • starting the CPU;
  • choosing operational mode and settings;
  • setting monitoring parameters;
  • changing control programme settings.

The CPU automatically sends SMS messages about:

  • the CPU current operational setting;
  • time of reaching full operational capacity;
  • change of the CPU operational settings (manually/remotely);
  • manual stop of the CPU operation;
  • network voltage goes beyond the permitted limits;
  • short circuits;
  • power disruption;
  • reaching temperature limits and CPU stop;
  • start of the CPU (after the emergency situation is eliminated);
  • the CPU cabinet tampering.

Communication is established through a build-in WAVECOM Q2400A (Q24EXT) GSM modem. The control point modem is available as a separate kit with a power supply. Thus, for a full-scale operation of the control point it is sufficient to have a PC and a GSM modem kit. Fixed GSM modem operating on 900/1800 MHz is available from the same manufacture as TVERTSA 900. Other types of modems, such as WAVECOM FASTRACK M1206B or M1306B modems, are also suitable for use in the control point.

Software

The CPU software system comprises converter software and TVERTSA-MONITOR control point software.

The control point software was developed as a simple and comprehensible package that can be easily operated even by unskilled PC users. The system data base was designed to use Widows Office Package capabilities as much as possible. The software was first tried on Windows-2000 and Windows XP.

The CPU was designed as an up-datable system, which is capable of adjusting to fast changing operational requirements. TVERTSA 900 is equipped with the controllers remotely re-programmable via a standard communication channel.

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