Rectifiers for traction substations 600...3300 V

Maintainability:

• the lowest maintenance;
• easy access to the circuit components for simplification of technical maintenance;
• application of maintenance-free contact joints technology in the power part of rectifiers;
• controlled diodes pressure load due to application of calibrated crimping components for “diode-cooler” assembly.

Cost saving:

• long lifetime and a high level of technical and performance characteristics due to application of modern high-quality, reliable and safe components;
• space-saving overall dimensions.

Application areas:

• metro, city electric transport and railways 600...3300 V DC traction substations;
• industrial and metallurgical enterprises, mining and processing works departmental railways 1650, 3300 V DC traction substations.

Power diodes

Pill power diodes of 25-26th class for current of 2500...3000 A are applied in the rectifiers. Two diodes are connected in series in each arm of rectifier providing high reliability and long operation life in "diode-diode" circuit rectifiers. The current is force-divided between parallel branches by means of effective magnetic dividers providing division of current between parallel branches not worse than 5%.

Voltage surge protection

Power semiconductor devices are protected against internal and external switching surges with RC-circuits and varistors in “diode-diode” circuit rectifiers. A damping capacitor is installed parallel to each power diode for surge protection in "diode-fuse" rectifier. The rectifier is protected with RC-filter (on DC side) against overvoltages from traction side and with varistor panel from power supply side.

Protection against short circuits

Rectifier are designed to withstand external short circuit without damages up to MV circuit breaker tripping. In “diode-diode” rectifier reach-through breakdown is excluded due to installation of two diodes in series into arms. In “diode-fuse” rectifier protection against internal short circuits is carried out due to power fuses, installed in series with each diode. Rectifiers are produced for various semiconductor devices failure modes (T, F and R modes) according to EN 50328.

Withdrawable and fixed rectifiers are equipped with microprocessor control and diagnostics system with displaying information about state of each diode on the visualization panel according to the following criteria: “normal operation”, “parameters derating” (for “diode-diode” design), “breakdown”, as well as about the diode temperature. Control system is carried out on the basis of SOTA controller, that meets IEC 61131 series of standards for PLC, and provides support of IEC 61850 protocol.

Monitoring of each diode parameters is carried out continuously during operation of the rectifier. Diagnostics according to the specified criteria allows significantly increasing failure-free operation of the rectifier. In case of diode parameters changing to critical for this circuit level, the power diode should be replaced without its breakdown. In case of one diode breakdown, the “diode-diode” rectifier continues its operation without power loss till replacement of the broken diode.

Information about state of the rectifier and its components is displayed on visualization panel, mobile devices (smartphone, tablet) or on the computer display via Web interface or special software. Mnemonic symbols of rectifier diodes, graphs of reverse voltage distribution between diodes and arms temperature is displayed. The communication with the MV switchgears protection devises and the upper level SCADA system is implemented in the rectifier.

We offer a new development — highly reliable withdrawable rectifiers providing compactness, simplicity and ease of maintenance. Withdrawable rectifiers include fixed cabinet and withdrawable power unit connected by contacts system.

Main advantages of withdrawable rectifiers:

• easy access to components and one-side maintenance with narrow front;
• safe operation; safe separation of power unit from busbar compartment with special back panel;
• high power with compact dimensions;
• rigid base providing easy manual maneuvering of power unit, steady structure and level floor;
• reliable step worm drive providing accurate performance of any speed and positioning task, as well as self-locking in any position;
• rectifier dimensions are optimal for use in a DC-board with DC cubicles.

Modern dry transformers with RESIBLOC^® windings, capacity from 630 kVA, with various combinations of high (HV) and low (LV) voltages are supplied as traction transformer. Transformers have original design of HV and LV windings made of wire and foil. Windings are shrouded with epoxy-impregnated fiberglass string.

Main advantages of transformers:

• reliable operation in highly contaminated and humid environment, at low temperatures;
• windings dynamical resistance to mechanical stress is 650-750 N/mm^2_;
• compliance with the basic standard for transformer equipment IEC 60076-11 and VDE 0532;
• low noise level;
• fire safety and environmental compatibility, self-extinguishing in case of external flame or electric arc, with no release of toxic gases. All materials are non-combustible and do not sustain combustion process;
• availability of vibration-absorbing devices;
• windings and magnetic circuit temperature control;
• "cold" start with maximum load;
• minimum maintenance;
• high resistance to dynamic loads under overloads and short circuits.

Rectifiers are manufactured both for indoor and outdoor arrangement. In case of outdoor arrangement control and diagnostic system is located separately and installed indoors or in a cabinet with regulated environment.

Rectifiers are manufactured with air natural and forced cooling. Forced air cooling is actually combined natural air and forced air cooling. Rectifier operates with natural cooling under loads lower or close to rated ones. In case of risk of overheating under overloads, fans are switched on and forcedly cool diodes. Fans switch off automatically in a period of time after overload disappearance.