Thyristor Controlled Rectifiers (TCRs)

Depending on power, a Thyristor controlled fixed rectifier includes one or two cabinets with power thyristors, fuses, protection, control and monitoring components. It is supplied by a dry three-winding converter transformer.

Tablet power thyristors are used in the rectifier. High-speed power fuses are installed in series with each thyristor to provide protection against internal short circuits. Cooling is natural air.

The rectifier also provides protection of power semiconductor devices against internal and external switching overvoltages. Protection against internal switching overvoltages is provided by RC circuits, against external overvoltages - in combination: RC circuits and varistors.

The rectifiers are equipped with microprocessor control and diagnostic system based on SOTA® controller, conforming to IEC 61131 series of PLC standards and supporting IEC 61850 protocol.

MC-POWER module is connected to SOTA® controller to control thyristor bridge.

HMI is provided by an operator panel in the form of 7-inch TFT touchscreen display, allowing the user to exchange data with the control system. Operator's panel provides:

• output of operation mode messages;
• output of warning and emergency messages;
• selection of rectifier control mode;
• setting, change and saving of parameters settings;
• rectifier event logging;
• testing of separate rectifier units;
• connection of rectifier with telecontrol system.

Power supply systems with TCRs suppose relatively high output voltage from substations and reduced losses in DC traction network. This solution applied in the conventional transport systems, allows significantly increase the distance between substations, that depends on voltage-current characteristics slope, DC network loop resistance, as well as on train traffic density.

Application of energy-efficient power supply based on TCR can significantly reduce the number of substations required for a conventional system with diode rectifiers. That allows reducing costs on materials, as well as on building of substations.

Withdrawable thyristor rectifiers are designed for construction of urban electric transport traction substations with load current electronic switching. These devices include rectifier and switchgear functions.

Thyristor rectifiers provide switching of a wide range of load currents without electromechanical system and without an arc, i.e. electronic switching is achieved by thyristors opening pulses removing.

Benefits:

• power supply from the rectifier to the load is fully controlled in all operating modes;
• implementation of “line test” function in traction network without additional equipment;
• easy inspection and maintenance due to application of withdrawable component;
• no plasma emission at short-circuit currents interruption, since the switching is done with thyristors, as a result - no combustion products and their deposits;
• reduction of fire hazard due to absence of plasma generation open sources.

Withdrawable thyristor rectifier is based on standard arrangement of separate compartments common for many switchgear units:

• automation and control compartment - low-voltage compartment with control and diagnostic system components;
• withdrawable unit compartment - power part of thyristor rectifier;
• busbar compartment - includes AC and DC busbars. The compartment is divided into several isolated compartments, allowing safe access for power cables maintenance even under voltage on power busbars.

Division into compartments also allows safe maintenance of high-voltage measuring circuits and standby disconnector, located in busbar compartment.

Withdrawable unit has three positions:

• operating;
• control;
• maintenance.

Withdrawable unit moves automatically from operating to control position with the help of low-power electric drive, without any effort from the operating personnel. At the same time, operational safety is guaranteed by electromechanical interlocks system and organizational measures.

Withdrawable rectifiers are equipped with microprocessor control and diagnostic system based on SOTA® controller and MC-POWER module.

Similar to traditional switchgear, withdrawable thyristor rectifiers protect traction network by continuous monitoring and analysis of current and voltage variations dynamics in traction network and issuing rectifier tripping commands in case protective functions set parameters are exceeded.

SOTA® control system generates and saves two types of fault waveforms (current and voltage waveforms) each time one of protections trips:

• “Fast track” (time coverage depth is 100 ms);
• “Slow track” (time coverage depth is 100 s).

Types of electronic protection (ANSI code):

• instantaneous overcurrent (50);
• time overcurrent protection (76);
• current rate of rise protection;
• current increment directional protection;
• overvoltage protection (59);
• undervoltage protection (27);
• time/current protection (49);
• rectifier failure;
• DDL protection;
• impedance protection.