DLF – Line Differential Protection Relay IEC 61850

Line differential protection relay with distance backup. Both units are suitable for lines of any voltage level, overhead or underground, multiterminal, and single or parallel circuits. IEC 61850 certified.

The DLF includes all the protection, control and measurement functions for a power line with or without series compensation, single or double breaker, and single pole or three pole tripping.

The fast differential unit, complemented by the external fault detector and the capacitive current compensation unit, protects lines with up to 5 terminals, even with a transformer in the protection zone, providing excellent reliability even in the most adverse conditions.

The breaker failure protection and synchrocheck can supervise two circuit breakers. Also, the recloser function allows sequential breaker closing using a master-slave scheme.

Key Features

  • Phase Differential Unit. Configurable with up to six three-phase current inputs, to protect 5-terminal lines with single breakers, and 3-terminal lines with breaker-and-a-half.
  • Neutral and Negative Sequence Differential Unit.  Increases sensitivity during internal faults with low current contribution, such as very resistive faults, which may not be detected by the differential phase unit.
  • External Fault Detector. Blocks the differential unit against external faults with very high CT saturation, providing exceptional security.
  • Capacitive Current Compensation. The differential unit maintains good sensitivity in cables and very long overhead lines.
  • Transformer-Line Protection Zone 
  • Multi-Terminal Fault Locator
  • 8 Distance zones. Reversible distance zones with Mho or quadrilateral characteristic. Independent characteristic selection for ground and phase-to-phase faults.
  • Communication between IEDs
    • Up to 4 ports: Communication without redundancy with up to 4 remote ends or with redundancy with up to 2 remote ends.
    • Selectable speed: from 1 x 64 kbit/s up to 2 Mbit/s.
    • Multimode or single mode FO interfaces (optional SFPs).
    • Communication with SDH multiplexers via C37.94 or via ZIV model F2MUX optical-electric converter that integrates G703 and V35 output interfaces.
    • Up to 16 digital signals can be exchanged between terminals to implement teleprotection schemes.
  • General characteristics of the “ZIV e-NET flex family”:
    • Powerful programable logic
    • 2000 event log. Up to 100 oscillography seconds
    • Alphanumeric or graphic display
    • Easy HW expansion without FW updates
    • Unused protection elements can be hidden
    • Custom mapping of physical current and voltage inputs to protection elements
    • Can be used to protect multiple bays
    • Up to 20 analog channels, 160 DI, 80 DO, and 22 LEDs
    • Bonding, RSTP, PRP and HSR redundancy
    • IEC 61850 ed. 1 & ed. 2 protocols, DNP3.0, Modbus RTU and PROCOME
    • Native process bus. Analog input cards operate as Merging Units for the CPU. Synchronized samples at 4800 Hz (as per IEC 61869-9)
    • Cybersecurity in accordance with IEC 62351 and IEEE 1686-2013 standards. RBAC, secure keys, physical and logical port disabling, cybersecurity event log, and securing of management protocols (PROCOME, HTTPS, SFTP, SSH)
    • Time synchronization by IRIG-B, SNTP and PTP (Ordinary Clock / Transparent Clock)



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