DC logger for AC supplied trains

In the Netherlands, two different traction energy supply systems are in use on mainline railways. The standard supply voltage for railway lines is 1500 Vdc. The newly built Betuweroute freight line and the high-speed line Amsterdam-Rotterdam-Antwerp however have been electrified with 25 kV, 50 Hz. It was anticipated that under specific fault conditions, stray currents from a DC line could flow in the return circuit of a nearby AC line, exposing for example transformers to DC effects. Prolonged exposure to DC effects may damage the main transformer on board of a train. In order to assess the risk, on-board measurements may be required.

In order perform such measurements relatively easily, EMPEQ has developed a portable data logger which can be placed on board of any train permitted to run on a 25 kV electrified line in the Netherlands.

The instrument is equipped with a number of high-precision Direct Current Transformers (DCCTs). One DCCT is mounted on each of the cables connecting the main transformer’s return connection to the return current brushes of the train or locomotive.

The instrument logs the DC component in 10-second intervals. It is equipped with a GSM modem to transmit measured data to a remote server and to send an alarm SMS if a pre-set level of DC is exceeded.

Technical specifications:

Supply voltage

110 Vdc

Type of DCCT

LEM IT400-s

Number of DCCTs


Max. current per DCCT

400 Arms

DC accuracy

± 50 mA

Logging interval

10 seconds

The instrument has been successfully tested against the following EMC standards:

EN61000-6-4:2007  Generic emission standard for industrial environments

EN61000-4-2:1995  Electrostatic discharge immunity

EN61000-4-3:2006  Radiated electromagnetic field immunity

EN61000-4-4:2004  Electrical  Fast Transient (EFT)  immunity

EN61000-4-5:2006  Surge Transient immunity

EN61000-4-6:1996  Conducted Radio-frequency disturbances immunity

EN61000-4-8:1993  Power frequency magnetic field immuity

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