Overview
EN 50123-7-2:2003 is a CENELEC European Standard for railway applications - fixed installations - D.C. switchgear. It defines requirements for isolating current transducers and other current measuring devices used in d.c. traction systems. These transducers normally sit between a sensor on a live conductor or rail and the secondary device, providing galvanic insulation between input and output. This part is to be used in conjunction with EN 50123-1:2003 and was approved by CENELEC in 2002.
Key topics and technical requirements
- Scope and application: Devices for fixed installations in DC traction systems, intended to feed measuring and/or protection equipment.
- Electrical characteristics:
- Insulation level equal to the main circuit and in accordance with EN 50123-1.
- Frequency response from DC up to at least 1 kHz.
- Preferred secondary signals: voltage (0–10 V) or current (e.g. 4–20 mA).
- Accuracy, linearity, output impedance and phase shift must suit designated use (measurement vs protection).
- Thermal, overload and short-time withstand requirements; rated continuous thermal current and specified short-time withstand currents.
- Requirements for auxiliary power indicators and electronic self-checking where applicable.
- Transducer types covered:
- Isolating current transducers
- D.C. shunts (characteristics such as rated current, output signal, overload capability)
- Hall-effect sensors (additional parameters like number of Hall devices)
- Mechanical requirements: Enclosure options (metal or insulating), mounting and insulation for proximity to live conductors.
- Information exchange: Supplier/purchaser responsibilities for specifying conversion ratio, insulation levels, overloads, linearity, di/dt capability, residual offset, burden, etc.
- Tests and compliance:
- Dielectric (power-frequency, and impulse tests where U > 2.5 kV)
- Calibration/linearity tests across 0–1.2 Ith (measurement) or 0–2 Ith (protection)
- di/dt response type tests
- EMC testing per the EN 50121 series
Practical applications and users
- Typical users: railway electrical engineers, switchgear designers, manufacturers of current transducers and sensors, procurement/specification engineers, test laboratories, and maintenance teams.
- Practical uses:
- Accurate current measurement for monitoring and control in DC traction substations and switchgear
- Inputs for protection relays and control systems requiring galvanic isolation
- Integration into fixed installations where EMC, insulation coordination and di/dt response are critical
Related standards
- EN 50123-1:2003 (general requirements for D.C. switchgear)
- EN 50121 series (EMC for railway applications)
- EN 50124-1 (insulation coordination / overvoltage categories)
Keywords: EN 50123-7-2, isolating current transducers, current measuring devices, d.c. traction systems, railway switchgear, galvanic insulation, calibration test, dielectric test, EMC.