3kV Cabinet Housed Traction Rectifier

7/17/2019 3kV Cabinet Housed Traction Rectifier

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EZB - U 3 kV Cabinet-housed Traction Rectifier

Elektrizace železnic Praha a.s.



The tract ion rectifier in a box housing was developed in

cooperation with ČKD Elektrotechnika, a.s. The twelve-pulseddiode rectifier with still-air cooling is designated for feedingthe direct-current overhead traction lines 2 – 3 kV DC/IT. Thestandard version, which is manufactured and supplied, servesDC 1 500 A current, with overload capacity of Class V pursuantto ČSN EN 60146-1-1. The recti fier is s tored in two steel boxes of the total dimensions:width 2 × 1 200 mm, height 2 000 mm and length 1 600 mm.Each box contains one part of the converter block (connection:3-phase Graetz bridge; 3 000 V, 750 A) located upon a carriage(a hauling part). The external dimensions of the rectifier wouldallow for its installation in a converter station, together with a

switchboard of the EZB 3 kV DC type, which together form acompact unit.

The rectifier carriage

is designated for the purposes of the hauling of the rectifierblock in and out of the box; the connection of the power unit isvia contact heads and their opposite knife contacts. Before thecontact heads connection to the AC and DC power units by wayof knife contacts, there is a connection of the „dead“ parts ofthe carriage to the protection system of the transition converterstation by way of a grounding contact. The carriage movement isdriven by an electric motor, as far as the fully inserted position,and the full sliding out to the other direction. In emergency, e.g.,during a controlling voltage outage, the rectifier carriage can behauled manually (with help of a crank). Furthermore, there are

openings located in the front steel sheet cover, which allow for

natural air cooling of the converter block. The carriage moves withhelp of side guides inside the box. In the inserted position, thecarriage is fi xed with help of driving mechanism of the extensiblepart.

The rectifier block

is composed of a three-arm converter (2 × 3-phase, with a 30 deg.phase shift). A converter arm consists of two series-connectedpellet diodes cooled by heat tubes. The value of the single-diodecut-off voltage equals 6 kV. Each diode is complete with an RCelement limiting the commutating overvoltage. The converter

block is designed for still-air cooling; therefore, the space insidethe box above the converter is open and it ser ves as a ventilationflue. The converter is connected in the input side (AC) by way ofCu connecting bars, which are linked by way of contact headsso that, connected to the secondary rectifier transformer layerwinding, it forms a three-phase bridge connection. The outputside of the block, i.e., the plus and the minus pole tappings withvoltage of 3,3 kV DC, is performed also by way of connecting barslinked to contact heads. The converter block, the connecting barconnection, and the contact heads, are installed upon a carriage.

The rectifier box

comprises a steel sheet structure designated to provideprotection against dangerous contact voltage of the live partsand to hold a set of the mechanical and electric equipment of the



rectifier. The box is divided into three basic spaces, i.e., a space

with the carriage carrying the rectifier block; the space (locatedin the front of the box) housing the equipment consisting ofauxiliary circuits and the supervisory control and data acquisition(SCADA); and the space (located in the rear part of the box) forthe power connection of the rectifier, also housing the relevantovervoltage protection and voltage and current measuringequipment. It is possible, upon request, to place a disconnector

of the plus or the minus poles of the output voltage from therectifier to that space. The front lower part of the box offersspace for the carriage. The space for the carriage is separatedfrom the rear part of the box with help of an insulating barrierwith openings for the contact heads. The openings will close withhelp of mechanisms controlled by the mechanism, which pushesthe carriage out of the box so that the live part of the rec tifier are

covered with an insulating partition when the carriage is out. The space for the auxiliary circuits and the supervisory controland data acquisition (SCADA) equipment is in the switchboard,covered with the front door, which also carry the control andvisualisation panel and an analyser of temperature of thetransition transformer. This space also houses the programmablelogic controller (PLC) for the entire converter, and also theprotective, interconnecting and connecting parts of auxiliarycircuits. The rear part of the box must be accessible by the staffbecause its upper part contains a door with a peephole for visualcontrol of the position of the disconnector. If the disconnector isinstalled, that door contains a small opening in the lower part of

the door allowing for access to the manual (emergency) drive ofthe disconnector. The opening is fitted with an end-limit switch,which makes sure that the rec tifier unit primary switch is off, andthus ensuring non-operational switching of the disconnector,including in emergency. The lower part of the box is fitted with

a steel sheet cover. The upper rear part of the box holds RC

elements designed to limit overvoltage from the AC feeder, i.e.,from the rectifier transformer. The RC elements are protectedagainst overcurrent with help of high-voltage fuses. The samespace also contains a DC overvoltage arrester. The rear part ofthe box also contains knife contacts connecting to the contactheads on the carriage guides and both DC bus bars allowing forconnection with the second converter box and the main 3,3 kVDC bus-bar of the converter. In that part, too, a protective FeZnwire, cross-sectioned 120 mm2, is installed, connected to the„dead“ portions of the box, which should be connected to allboxes and to the protective system of the converter.

Rectifier control

it may be performed from three places, i.e., local, remote,and central controls. Remote and central controls requirethe installation of electric drives in some selected switchinggargets. Power supply to the controlling and auxiliary circuits isprovided for with help of a 2-110 V DC/IT system; upon specialrequest, it also is possible to apply a 2-48 V DC/IT system.Under local control, the switching on and off of the individualswitching gargets, i.e., the disconnectors hooked up to the plusand the minus poles and the rectifier unit primary switch, isusually performed from the 22 kV switchboard with help of therelevant controllers and the state of the apparatuses is shownthere, too. Also, local control may be performed directly fromthe converter box with help of a control panel communicatingwith a programmable logic controller (PLC) rather than from the22 kV switchboard. In the standard regime, the programmablecontroller ensures all functions of the converter, i.e., transfer ofdata (communication with the controlling PLC) serving the remoteas well as the central control of the unit, including the controllingfunction (switching on and off, switching over to “local”, “remote”,and/or “central” control) and visual (e.g., of defects). At thesame time, the PLC implements functions relevant for ensuringthe blocking conditions. In the standard version, the PLC may beconnected to allow transfer of data under the remote and central

controlling functions subject to the installation of a metallic or anoptical fibre connection.



The following blocking conditions are stipulated and guaranteedby the controlling circuits, in order to ensure the correct operation

of the converter and safe operation of the electrical equipment: When the primary switch is on, it is not possible to switch on the

disconnectors hooked up to the positive or the negative polesof the rectifier unit;

When the primary switch is on, it is not possible to slide out thecarriage with the converter block;

During a controlling voltage outage when the signallingof a diode puncture does not work, the primary switch isautomatically switched off.

The primary switch cannot be switched on, or it would not hold inthe “ON” position, as long as:

The carriage with the converter block has not been dulyplugged in;

The rear door of the box, the emergency manual control doorof the plus or the minus pole disconnectors, or the carriageemergency control door, are not duly closed;

Increased temperature of the converter diodes is signalled; The input alternating side of the conver ter is not live.

Electrical parameters

Nominal voltage on the converter input side ULN

2 500 V AC

Nominal frequency on the converter input side f n 50 Hz

Nominal permanent rectified voltage UdN

3 300 V

Highest permanent rectified voltage UdM

3 600 V

Highest short-time rectified voltage UdM

3 900 V

Nominal permanent rectified current IdN

1 500 A

Short-circuit resistance Ipk

: - Out of nominal load 12 kA/10 ms,

- without load 7,0 kA/100 ms

17 kA/10 ms

9,5 kA/100 ms

Short-circuit resistance ICM

15,3 kA

Nominal load losses 10,04 kW

Overload capacity 150 % 2 hours, 200 % 1 min.

Cooling still-air

Coverage IP 20/ above IP 00

Converter power connection 2 × 3-phase bridge

Output direct voltage undulation 12-pulsed

Number of series connected diodes in the converter arm 2 pieces

Number of parallel connected diodes in the converter arm 1 piece

Auxiliary circuits voltage 110 V DC / 30 W max.

Elektrizace železnic Praha a.s. Tel.: 00420 296 500 111nám. Hrdinů 1693/4a Fax: 00420 296 500 700

140 00 PRAHA 4 – Nusle E–mail: [email protected]

Czech Republic www.elzel.cz

3kV Cabinet Housed Traction Rectifier

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