Transmission lines

Protection relays

In addition to high-quality products, we are committed to providing
industry-leading support and service to our customers.

AQ 210 and AQ 250 – Protection relays for the most demanding applications

Both AQ 210 and AQ 250 series provide optimal solutions for any electrical protection and control application, from utilities and power plants to wind power and heavy industry applications (offshore, marine) as well as industrial and institutional electrical systems. The series offer both integrated and segregated protection control, monitoring, and measuring solutions that include complementary and powerful monitoring, measuring, communication, and diagnostics information.

The AQ 250 series has many advantages: it offers a large full-color display that you can configure yourself, and is equipped with up to 14 expansion slots for option cards (compared to the six in AQ 200). AQ 250 is therefore ideal for applications that require a more integrated functionality.

All our protection relays are easy and fast to configure which reduces engineering costs, while the devices’ unique modularity reduces the lifecycle costs of your installation. The latest technologies give protection and control engineers new options and open a whole new dimension of protection and control!

The AQ 210 and AQ 250 series provide…

  • complete line, feeder, capacitor bank, transformer, generator, and motor protection applications.
  • the perfect choice for the most demanding protection applications (including rotating machines).
  • a future-proof solution for distributed protection and control.

Read more about our AQ 210 and AQ 250 protection devices in our product catalog.

AQ 300 – Protection relays for high-performance protection

The AQ 300 protection relay series combine a powerful and modern design with decades of proven relay protection history. The series provides a long-term technology solution for all transmission protection and control applications, extending to sub-transmission and distribution levels.

We offer a complete selection of line distance and differential protection, distributed and centralized busbar protections, and multi-winding transformer protection. Additionally, comprehensive generator protections and bay control units are available.

The AQ 300 series provides…

  • a full range of solutions for any high-performance protection application, especially for transmission.
  • high scalability with both standard and customized configurations, as well as additional I/O slots.
  • an intuitive HMI, a high recording capacity, and an integrated WEB server feature.

Read more about our AQ 300 protection devices in our series flyer.

Read more below ⇒

Patented ultra-accurate measurement technology and algorithm

Within a single device you get a unique combination of up to 0.2 % power and energy measurement accuracy, a full dynamic measurement range as well as measurement and protection that is independent from frequency.

Highlights of the key features in our patented protection relay technology:

  • Combined protection and metering applications by our very accurate measurement technology, allowing for better than 0.2 % for energy and power measurements.
  • A high sampling rate of 3.2 kHz to protect and monitor network transients.
  • Versatile and very sensitive earth fault protection for any type of system earthing, including our patented intermittent earth fault protection for compensated networks.

Our innovative measurement and protection algorithms have been proven effective in power grids since 2013.

Read more about what others have achieved with our products in our references.

Want to book a discussion? Contact us!

Protect and connect your distributed generation resources safely

Adding any inverter-driven generation to a power grid (whether wind or solar) also adds complexity to the grid’s protection. The AQ 200 series (AQ 210 and AQ 250) is an excellent candidate for protecting your renewable assets and their interconnections.


  • Sub-cycle start and trip times for both current-based and voltage-based protection.
  • 6…75 Hz ultra-accurate frequency tracking for dependable frequency protection and load shedding.
  • Effective Ethernet-based relay-to-relay communication schemes.
  • Up to 31st harmonic monitoring.
  • Sub-harmonic filtering capabilities.

Maximum performance without compromises in user friendliness

The latest technologies give protection and control engineers new options and open a whole new dimension of protection and control.

Fast, accurate, and user-friendly:

  • Combined protection and metering applications with up to 0.2 % power and energy accuracy.
  • Versatile and very sensitive earth fault protection for different types of system earthing.
  • A high sampling rate of 3.2 kHz for recording network transients.
  • Up to 100 disturbance records with maximum resolution.
  • Up to 15,000 events in flash memory.
  • Seamless communication with various protocols: IEC 61850, IEC 104, IEC 101, IEC 103, Modbus TCP/RTU, DNP 3, SPA, and OPC UA.

Innovative features guarantee the maximum use of the protection devices:

  • Guided wizards, sophisticated setting aids, a highly customizable HMI, file storage for supportive documents, extensive user log information, and much more.
  • The AQtivate 200 setting and configuration software can be downloaded free of charge.

Read more detailed descriptions of Arcteq innovations and other features in our product catalog!

Offering industry-leading customer service

We are an independent, family-owned company with a focus on protection relays and arc flash protection systems. We are an agile companion with reliable delivery times, and all our products are manufactured in our headquarters in Vaasa, Finland.

About us:

  • Over 50,000 protection devices and 100,000 arc flash sensors installed in more than 50 countries all over the globe.
  • Sales and support in all continents through our own offices and through partners around the world.
  • One of the fastest growing companies in global protection and control business.
  • Part of Ensto Group, an international family business, bound by a common purpose: making better life with electricity. Sustainably.

We invest heavily in continuous research and product development to address the challenges raised by the changes in power grid technology and sustainable energy systems. Our mission is to help enable the safe and reliable supply of energy by enhancing power system protection.

In addition to high-quality products we are committed to providing our customers industry-leading support and service. Our average after-sales response time is under two hours. We can also offer a quick response to development requests – with us three years can be cut down to one.

Laajasalo reference case


Sähkönjakeluhäiriö Laajasalossa 23.8.2022

Helen Sähköverkko Oy:llä oli elokuussa laaja sähkökatko koskien alussa 12878 asiakasta Laajasalon sähköaseman syöttöalueella. Keskimäärin tämän keskeytyksen kesto oli 88 min, pisimmillään vajaat 2,5 tuntia.

Want to know more?

Do you want to hear more about the possibilities of our protection relays solutions? Contact our sales team or ask us for an offer. We will be delighted to walk you through our solutions.



Happy Holidays!

It’s that time of the year again…as the year is coming to its end, we would like to thank you, our customers and partners, for supporting us and for making power distribution safer and more reliable around the world. Let’s let the closeness of family and friends renew our spirits this festive season.

From all of us at Arcteq we wish you the very best during the holiday season and beyond.