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Ing. Aneta Sčebelová
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Rail transport

When operating rolling stock, very high requirements are placed on the operability and continuity of energy supply from the traction battery. It is also necessary to ensure the full functionality of stationary elements around the railway track. All this is possible by a number of HIG insulation monitoring devices made by HAKEL company.


Our solutions

  1. Mobile part – Traction battery
    Traction battery is an essential element of all rolling stock. The safety, communication and the most necessary control technology of the rolling stock are supplied from the DC voltage of the traction battery. Due to this, very high requirements are placed on the operability and continuity of power supply from the traction battery.

    The standard solution to prevent unexpected power supply fall-out from the traction battery is to operate this power supply system as isolated from the vehicle body. Any emerging insulation breakthrough on the vehicle body should be monitored and signalled to the vehicle control unit (VCU) well in advance before the insulation breakthrough may cause a short circuit in the power supply.

    HAKEL company has developed a range of HIG**VDC/T products for traction battery monitoring. These are insulation monitoring devices that meet the requirements of EN 50155 and IEC 61557-8 standards. The specialty of these insulation monitoring devices is that they monitor the insulation resistance in the positive pole of the IT power supply system against the body and separately in the negative pole against the body. Devices therefore provide two numerical data on the two insulation resistances. This is especially useful when looking for insulation breakthrough, where the service team can only inspect a specific half of the traction battery voltage distribution.

    We distinguish two basic product lines, namely HIG**VDC/T and HIG**VDC/T-L. These two series differ in the measured range of the insulation resistance. HIG**VDC/T line monitors the insulation resistance in a range of 5 to 990 kΩ, HIG**VDC/T-L line monitors the insulation resistance in a range of 2 to 550 kΩ. If the measured resistance value is lower than the measured range, status “<5“ respectively “<2“ kΩ is signalled.

    HIG**VDC/T devices are intended to monitor 12, 24, 48, 72 and 110 V DC voltage, are powered from the measured system and communication with VCU is possible by using RS485 bus bar or relay outputs. Devices meet OT3 temperature class (according to EN 50155). If the requirement for a temperature class is higher, device HIG99 can be used. HIG99 meets OT4 temperature class and allows communication with VCU through CAN bus bar.
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  2. Mobile part – Traction container and drive units
    A traction container is a device that usually contains a galvanically isolated unit of a multi-quadrant, power converter, which serves to regulate the traction motors of the electric traction vehicle themselves. Usually, the traction container contains one converter, which drives one to two traction motors.

    Due to higher safety and reduction of EMC/EMI influences, each traction container is designed as an isolated system, galvanically separated from the vehicle body as well as from the input voltage. From the design point of view, an isolated HF system is created by an isolating transformer, followed by part of the rectification by a multi-quadrant rectifier, which creates a direct current intermediate circuit, and the inverter itself, which supplies the required value of alternating voltage and variable frequencies for the traction asynchronous/synchronous motor. The isolated system of the drive unit is therefore in most cases a combined AC/DC isolated system. That is, a system that contains a galvanically connected alternating and direct current part and insulation fault may occur on both systems.

    In these cases, AC/DC type insulation monitoring devices are used to monitor the insulation. These devices are able to detect insulation breakthroughs both on the AC side (i.e., motor side) and on the DC side (i.e., inverter intermediate circuit side).

    HAKEL company uses the HIG99 insulation monitoring device for these purposes. These are insulation monitoring devices that meet the requirements of EN 50155 and IEC 61557-8 standard. The measured range of insulation resistance of this device is 1 kΩ to 10 MΩ and the device is supplied with 24 V DC independent low voltage. From the point of view of the measured system, the permissible voltage is 1 000 V DC / 710 V AC (10 to 440 Hz). If it is necessary to monitor the higher network voltage, it is necessary to use a HIG-CD 1k8 coupler, which allows up to twice the voltage of the measured system. HIG99 device allows to inform about the insulation status via relay or HIG99 KM CAN communication module can be used for direct connection to the CAN bus bar with the CAN OPEN protocol.

    In terms of location, we recommend selecting the place where the insulation status fault is most likely to occur as the connection point of the insulation monitoring device. In the case of the traction container, it is the AC side, because the most common cause of insulation fault in the drive unit is usually the traction motor insulation disruption.
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  3. Mobile part – CES, auxiliary drives and passenger compartment
    Modern cars, not only railway transport, usually generate a voltage of 3x 400 V / 50 Hz from the heating coupling distribution. This industry standard allows vehicle manufacturers to use common industrial components, for example, frequency converters for fans drive.

    3x 400 V / 50 Hz network is usually created by the so-called Central Energy Source (CES). These are HF transformer, rectifier, direct current intermediate circuit and inverter with a fixed frequency of 50 Hz. However, it is also possible to come across different approaches (e.g., LF isolating transformer at the inverter’s output). Thus formed three-phase system is left as galvanically isolated, both from the input voltage and the vehicle body. It is therefore an IT type power supply system. Great advantage of this approach is safety of passengers who are allowed to power their own appliances from this system, through the 230 V socket.

    In order to ensure that the power supply system is actually separated from the vehicle's body, the insulation monitoring devices are used. Devices have the task of notifying the emerging insulation breakthrough in advance, before systems’ insulation resistance drops below the dangerous limit.

    HIG99 is recommended type of insulation monitoring device. It's AC/DC type, thus, the type of insulation monitoring device that is able to detect insulation fault even in direct current parts of CES. This device can be connected to the train control system via CAN bus bar, when HIG99 KM CAN communication module is used. Then the insulation monitoring device provides service information about the current status of the insulation resistance.

    Another HIG99 advantage is the possibility to use the function of remote unblocking (disconnection) of the device from the measured system. This is used in cases where it is possible to connect more wagons (every wagon has its own CES) and thus create one galvanically interconnected 3x 400 V / 50 Hz network throughout the whole trainset, where CES work in parallel, or some may be completely turned off. Only one insulation monitoring device must remain active in such cases, other devices must be disconnected from the power supply system. The insulation monitoring device is an active device whose presence affects the measured IT power supply system and mutual operation of multiple isolation monitoring devices on one IT power supply system is excluded – there would be mutual influencing between the measurements. Device can be unblocked by a command via CAN bus bar or by a logic input.

    It is possible to use HIG93T insulation monitoring devices if it is not required to monitor the status of CES direct current part. HIG93T in cooperation with TL400T inductor also enable monitoring of the 3x 400 V / 50 Hz system.
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  4. Stationary part – Security and communication technology
    Railway infrastructure is largely built on isolated systems. IT systems can be found both in power supply traction converter stations and in security technology at rail crossings and signals. They can be found on both track and station security and communication systems.

    Voltage conditions on these power supply systems are different, we encounter low DC voltage networks for backup accumulators, but also with a 3x 6 000 V distribution to supply non-traction consumption along a wide railway track. This means, it is necessary to solve each application individually. HAKEL company has developed a wide range of insulation monitoring devices for these purposes.

    We recommend HIG93 insulation monitoring device for AC systems with nominal voltage up to 230 V AC. This device is designed to monitor insulation resistances in the range of 5 to 900 kΩ and is voltage independent of the measured system. This means that the device is able to measure the insulation status of the IT power supply system even in its voltage-free condition. This is typically used on critical infrastructure such as security technology, when it is necessary to know the fault-free condition of the insulation before switching on the system itself.

    If the measuring range is unsuitable, HIG94 series devices can be used. HIG94 devices have a measuring range from 200 kΩ to 5 MΩ. Or conversely HIG93L series is designed for low insulation statuses, i.e., from 0,1 to 90 kΩ.

    A series of TL* adjusting devices are available to the customer, if it is necessary to monitor a voltage higher than 230 V. These adjusting inductors allow to connect insulation monitoring devices of HIG93 and HIG94 series to higher voltages, typically 3x 400 V, 3x 500 V, up to 3x 6 000 V voltage.

    HIG**VDC series is intended for direct current networks, security and communication technology. This series includes devices for 12, 24, 48, 72 and 110 V DC distribution. Measuring ranges of this series are always 5 to 990 kΩ, eventually 2 to 550 kΩ for HIG**VDC-L series.

    All devices (AC and DC) are standardly equipped with a display for operation and setting, then with RS485 bus bar, for reading measured quantities and with relay outputs, for logic information about the insulation resistance status.
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  5. Stationary part – Heating of switches
    In order to be able to operate the railway traffic safely even in the winter months, it is necessary to deal with the formation of icing and snow layer between the tongues of switches – rail switches in the track. If the icing is not solved, there is a risk that the rail switch tongue will not settle to the end position and thus the end of switch will not be realized. This would not endanger security in itself, but it would lead to a restriction in traffic. To prevent this, electric heaters are installed to switches. Heaters usually automatically detect icing in the winter months (or at least low temperature and humidity) and in the case of electric heaters of switches (EHS) removes icing by using resistance heater elements.

    There are two ways to power an EHS. It is either a supply from a non-traction line (typically 3x 6 000 V / 50 Hz) or a supply from a trolley wire, traction line (typically 25 kV / 50 Hz or 3 kV DC). In both cases, the voltage is too high to be safely used to power the heating rods. For this reason, EHSs with reducing, isolating transformers / galvanically isolated converters are installed in the rail track.

    Because the heating rods are installed directly in the track, a great mechanical stress and insulation degradation occurs here. Therefore, there is a risk of a conductive connection between the heating system and the rail and thus the formation of a dangerous contact voltage. This risk can be monitored well in advance using an insulation monitoring device.

    EHS output voltage is usually single-phase 230 V / 50 Hz. We recommend using devices of HIG93/T series, If the source is a classical transformer. These devices are certified up to operating temperatures of -25 °C. If the customer requires a higher level of temperature resistance, or wants to monitor the direct current part of a possible inverter, HIG99 device type can be used, which is certified up to -40 °C.

    Both of these types of insulation monitoring devices have two fault levels and two output relays. Thanks to this, it is possible to monitor on one output relay information about the deteriorated, but yet faultless insulation resistance. On the second relay it is then possible to monitor the fault insulation status. This relay can then, when a fault is detected, disconnect the heating source from the heating rods and bring the EHS to a safe condition. All this information can be signalled to the control room both by relay and by RS485 bus bar.
    Nahrávám ...
    By ticking this box you will give us the information that you are not sure about the correctness of your selection. However, it is necessary to send an inquiry.