AQ-S255 Bay control device


The AQ-S255x bay control device can be applied to demanding control applications. AQ-S255x comes with full current, voltage, power and energy measurement capabilities. The relay can be equipped with up to eleven (11) I/O or communication cards, depending on the requirements of your application. The logic programming is powerful and easy to use, and it further expands the device’s application range towards more demanding control needs. The HMI is large and can be freely programmed, and it provides a quick visualization of the status of objects, alarms and events. AQ-S255x communicates using various protocols, including the IEC 61850 substation communication standard.

The AQ-S255x bay control device comes in two variants: the “A” variant (AQ-S255A) includes all the current, voltage, power, and energy measurement capabilities mentioned above, while the “B” variant (AQ-S255B) also includes the innovative automatic voltage regulator that allows you to control more than one transformer at the same time.


  • A bay control device with extensive I/O.
  • Synchrocheck for up to three (3) circuit breakers.
  • Optional power and energy measurement accuracy of up to 0.2 %.
  • Parallel voltage regulator for controlling 1+ transformers at the same time (AQ-S255B).

Technical data

  • Circuit breaker failure protection (CBFP; 50BF/52BF)
  • Resistance temperature detectors (RTD)
  • Voltage memory
  • Programmable stage (PGx>/<; 99)

  • Number of objects to control and monitor: 10
  • Number of indicators to monitor: 20
  • Number of setting groups: 8
  • Auto-recloser (0 → 1; 79)
  • Synchrocheck (ΔV/Δa/Δf; 25)

  • Number of object to contol and monitor: 10
  • Number of indicators to monitor: 20
  • Number of setting groups: 8
  • Automatic voltage regulator – parallel control (AVR; 90)
  • Auto-recloser (0 → 1; 79)
  • Synchrocheck (ΔV/Δa/Δf; 25)

  • Phase, sequence and residual currents (IL1, IL2, IL3, I01, I02)
  • Phase, sequence and residual voltages (UL1, UL2, UL3, U12, U23, U31, U0)
  • Frequency (f)
  • Power (P, Q, S, pf) and Energy (E+, E-, Eq+, Eq-)
  • Power and energy class 0.5
  • Power and energy measurement accuracy of up to 0.2 % (optional)
  • Current transformer supervision
  • Voltage transformer supervision (60)
  • Total harmonic distortion (current)
  • Total harmonic distortion (voltage)
  • Fault locator (21FL)
  • Measurement recorder
  • Measurement value recorder
  • Event recorder (max. 15 000 permanent event records)
  • Disturbance recorder (max. 100 records á 5 seconds at 3.2 kHz sampling)

  • Current inputs: 5
  • Voltage inputs: 4
  • Digital inputs (fixed): 3
  • Digital outputs (fixed): 5
  • Number of empty slots: 11
  • Digital inputs: +8/16/24/32/40/48/56/64/72/80/88 (optional)
  • Digital outputs: +5/10/15/20/25/30 (optional)
  • Milliampere I/O module (4 mA outputs + 1 mA input)
  • Communication media (see "Communication" below)
  • External I/O modules (see "Accessories" below)

  • Communication inputs
  • RJ-45 100 Mbps Ethernet (front panel, fixed)
  • RJ-45 100 Mbps Ethernet and RS-485 (rear panel, fixed)
  • 2 x RJ-45 100 Mbps Ethernet with an IRIG-B input (optional)
  • 2 x ST 100 Mbps Ethernet with an IRIG-B input (optional)
  • 2 x LC 100 Mbps Ethernet (PRP/HSR) (optional)
  • RS-232 serial fiber (PP/PG/GP/GG) (optional)
  • Communication protocols
  • IEC 61850 (edition 1)
  • IEC 60870-5-101/104
  • IEC 60870-5-103
  • Modbus/RTU and Modbus/TCP
  • DNP3
  • SPA

  • AX007 External 6-channel 2-/3-wire RTD input module (pre-configured)
  • AX008 External 8-channel thermocouple and mA input module (pre-configured)
  • AX013 Raising frame (120 mm)
  • AX014 Raising frame (40 mm)
  • AX015 Wall mounting bracket

Additional material

Application Drawing

An application image for AQ-S255A bay control device, with one version drawn according to IEC standard symbols and the other according to IEEE/ANSI standard symbols.

Related products

Ask for an offer or more information

We provide a comprehensive range of services through our own skilled staff and a global network of partners.