Solutions   for   Protecting   andManaging   the   Electrical   Network

DDL 800

DC Line Protection and Fault Detector for Railways

DDL800 performs monitoring of railway and tramway catenaries on DC electrical networks. DDL800 acts according to rate of rise overcurrent criteria and includes a deicing monitoring function. A voltage protection is available as well as many operating functions such as a cable thermal image, a recloser with substation management and the check of the correct operation of the ultra fast circuit breaker.
The optional line test equipment EDL (consult us) confirms the fault elimination before authorizing the closing of the circuit breaker. As well as the usual protection functions, NP800 relays provide monitoring, measurement and recording of the electrical quantities of the network.
The relays can be set locally, using either the keypad and display or the RS232 port, or remotely using the RS485 port. Setting, reading, measurement and recording are all available locally or remotely.


  • Presence and lack of catenary voltage (P.L.V.)
  • Substation and catenary voltage comparison ΔU)
  • Voltage drop monitoring (ΔUL)
  • Catenary voltage monitoring [27DC] [59DC]
  • Recloser management on external trip
  • Overcurrent protection [76-1] [76-2]
  • Rate-of-rise overcurrent protection (di/dt)
  • Delta I current step protection (ΔI)
  • De-icing differential protection [87]
  • Upstream current detection (monitoring of current flowing to substation)
  • Cable thermal image [49DC]
  • Four shot recloser [82]
  • High speed circuit breaker failure [76BF]
  • Sensors monitoring (S.M.)
  • Latching of the output contacts [86]
  • Programmable line test before reclosure (with optional EDL interface, see application guide)


  • Configuration and parameter setting by local MMI or SMARTsoft
  • Real time measuring of electrical values: display with primary values of voltage, current and differential current
  • 2 setting groups, locally or remotely selectable
  • Self-diagnosis : RAM, ROM, EEPROM, output relays, A/D converters, auxiliary supply, cycles of execution of the software, hardware fault
  • 7 output units / 8 programmable digital input
  • Event recording: 200 / 250 locally recorded events with 10 ms resolution
  • Disturbance recording according to Comtrade format: storage of the last 12 records
  • 4 user programmable LEDs
  • Communication by Modbus®


  Device Doc. Type Lang. Ref. Index
DDL 800 Leaflet EN A433 C
DDL 800 Connection/Definition Diagram EN D40679 A