Inverting silicon-controlled converters for railway substations

 Application

Inverting silicon-controlled converters (hereinafter the inverters), type KTI5, with rated inverting current of 800 A, 1600 A and 2400 A, voltage of 3.8 kV are designed for delivery of excessive regenerative power from DC catenary to AC network on railway substations (hereinafter the substations) under boreal climate conditions, placement category 4 according to GOST 15150.

The product consists of

  1. KTI5 inverters consist of a control cabinet, 1 or 2 or 3 power cabinets subject to inverting current (hereinafter the CC and PC) and lead-in cabinet.
  2. The power cabinets include silicon-controlled rectifiers with protective RC-circuits, cooling fans, current and voltage sensors, thyristor control pulse amplifiers and a monitoring system. Whereby the low-voltage part (thyristor control pulse amplifiers, monitoring system and power sources) is located in the CC.
  3. The controllers included into the CC are microprocessor-based. A software written in the elements of read-only memory (hereinafter ROM) is supplied together with the inverters. The software implements algorithms for control, adjustment and protection.
  4. CC contains a diagnostics and information display system, which is based on an industrial computer. The monitor located on the CC door shows a mimic diagram, equipment operation modes, current and voltage measurement values, messages and other diagnostic information.

 

Electrical specifications

  1. Rated voltage of conversion on DC buses of substation is 3,800 V.
  2. Rated current of conversion on DC buses of substation is 1600 A.
  3. The inverters auxiliary power supply is ensured through a three-phase TN-S AC network with a rated voltage of 380 V or 220 V and a frequency of 50 Hz.
  4. Inverters allow for loads as shown in next table.
Mode Load as a % of rated current Load duration

1

2

3

4

100

125

150

200

Extended time

15 min

2 min

10 sec

At the same time, the current root-mean-square value should not exceed the nominal value during averaging time of 30 min.

  1. The inverters have continuous operation mode.
  2. The inverter maintains operational capacity in case if one of four series-connected thyristors on one arm of the bridge fails. In this case a warning signal is generated. If two thyristors fail on one arm, the emergency protection is triggered.
  3. Inverters are tested successfully according to the approved test procedure.

Protection system

The inverters have the following types of protection and blocking:

  1. thyristors protection against failure under the impact of overcurrents during emergency operation;
  2. inverters protection against rms current overload;
  3. inverters protection in case of power outage as well as interruption or unacceptable decrease of station auxiliaries voltage;
  4. protection against forced cooling termination, triggering the shutdown of inverters with adjustable time delay;
  5. overvoltage protection on thyristors during internal switching;
  6. thyristor breakdown protection;
  7. protection in case of opening PC doors amid high voltage;
  8. inverters startup blocking in case of alarming or, warning signals;
  9. protection against thyristors overtemperature;
  10. protection against loss of conduction on one arm of the bridge.

Design

  1. PC cooling is a forced air cooling with control of available air flow.
  2. Inverters have two-side access for the purpose of maintenance.
  3. The protection Rating is IP21 according to GOST 14254, except for the power busbar output point at a height of at least 2200 mm, where Protection Rating is IP00.
  4. Inverters can sustain the impact of vibration loads as per M2 group GOST 17516.1. Whereby the upper frequency range should not exceed 55 Hz.
  5. The PC doors are equipped with internal locks that can be unlocked with special keys. Power cabinets are equipped with a door lock that turns off the power circuits and does not allow to turn them on when the doors are open.
  6. Inverters meet the requirements for ergonomics and technical aesthetics in accordance with GOST 20.39.108.

Reliability

  1. The average time required to restore the operational condition of inverters using spare parts should not exceed 1 hour.
  2. The mean time to failures for inverters makes at least 10 000 hours.
  3. The total specified service life of inverters is at least 20 years.

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