AVR – Automatic Voltage Regulator

In an increasingly demanding market in terms of Quality of Electric Energy, the rules for parameter   definition and acceptable supply limits are becoming more stringent. There is a growing need for tools capable of meeting this reality and affording adequate voltage regulation.

Within this context, Treetech’s New Voltage Regulator Relay AVR offers   a solution that goes beyond the traditional and well-known “90” relays. The AVR is fitted with unprecedented resources in order to afford better control of load voltage limits, allowing the most stringent requirements to be addressed and met.

Main Features:

• Applicable to Power Transformers with load tap changers (LTC) and Single Phase Voltage Regulators;

• IED (Intelligent Electronic Device), suited for integration in supervision or monitoring systems through RS485 and RS232 ports (Modbus standard, DNP).

• Six independent sets of voltage regulation parameters, activated by way of hour programming (internal clock) or external dry contacts;

• Internal clock with hour, minute and second, day, month and year, plus day of the week;

• Independent activation times for voltage above or below the range adjusted;

• Defined timer types (constant time) or Inverse Curve;

• Linear timer with independent adjustments by ranges of voltage deviation;

• Compensation for line drop by adjustments to Resistance and Reactance or by the simplified voltage drop percentage method (compensation Z);

• Five signal relays with programmable functions and operation types (NO/NC);

• Analog output for remote reading of voltage, current or tap position (optional).  Configurable output range: 0…1, -1…1, 0…5, -5…5, 0…10, -10…10, 0…20, -20…20, or 4…20mA;

• Multi-measurement function: voltage readings for transformer and load, deviation of voltage, current, active, reactive and apparent power, load %, power factor and frequency;

• PT/ CT phase difference adjustable from 0 to 330º, allowing any type of PT/CT connection;

• Blocking of LTC in case of over-current or under-voltage.  Selectable activation in case of over-voltage: block of LTC or quick voltage reduction;

• High luminosity VFD (Vacuum Fluorescent Display) display type, readable under any lighting or temperature conditions;

• Operating temperature -40…+85ºC, allowing the device to be installed in outdoor panels;

• Universal power input, from 38 to 265Vdc/Vac 50/60Hz;

• User password protected programming menus.

• Communication by optical fibre, using external electrical-optical converter;

• Non-volatile memory for storage of measurement readings, LTC operations and alarm events. User selects variables for storage (maximum of 30 variables) and whether reading to be stored is instant value, average value, minimum or maximum for the interval;
• Position Measurement

Input for reading of position of LTC by way of potentiometer sensor, with compensation for cable resistance and error detection. Associated functions:

– Programming of output current for remote tap reading;

– Manual command of LTC, local (front panel) and by way of serial communication;

– Limitation of LTC excursion band (minimum and maximum taps allowed) and memorizing of maximum and minimum positions reached since last reset;

– Protection against undue operation of tap changer: tap changer block in case of undertaking operations not initiated by AVR.

• Parallelism by Master-follower Method

Same as for Position Measurement, plus parallel control for up to 6 three-phase transformers using the Master-Follower method.  Parallelism for up to 6 single-phase transformer banks using AVR together with Treetech’s SPS Parallelism Supervisors (1 AVR + 2 SPS per bank);

• Parallelism by Circulating Current

Parallelism control for up to 6 transformers using the Minimum Circulation Current method, with blocking by excess circulating current;

• Tap Changer Maintenance

Same as for Position Measurement, plus:

– LTC operation counter, with warning for high number of operations;

– Integration of commuted current squared, with warning for high I² sum values;