RTF – Automatic Voltage Regulator (AVR) IEC 61850

Voltage regulation for up to 5 power transformers in parallel.

Parallel transformer regulation by master-slave, circulating current and negative reactance methods.

It also includes line voltage drop compensation.

Key Features

  • Voltage Regulation. Maintains the transformer output voltage at the setpoint value, calculating the difference between the measured voltage and the setpoint voltage and comparing it with a threshold level to decide whether to send commands to the tap changer. The first tap change command has a time delay based on an inverse curve or a fixed time. Subsequent commands always have a fixed time delay.
  • Line Voltage Drop Compensation. A compensation based on the measured current and the voltage drop between the transformer and the load, that provides stable voltage under load. The compensation can be calculated by two methods: LDC-Z or LDC-R & X.
  • Parallel Transformers Regulation. Parallel transformer regulation can be achieved by the following methods:
    • Master / slave
    • Circulating current
    • Negative reactance

The first two methods in the list allow voltage regulation for up to 5 parallel transformers using GOOSE messaging (IEC 61850 ed 1 and 2).

  • Tap Indication and Monitoring. The active tap can be read by digital inputs (directly or in BCD code), by an analog current transducer or by a Resistor Chain. Tap monitoring permits to generate alarms corresponding to irregular or extreme tap positions and to failures after tap change commands.
  • 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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