Closed-Loop Testing for Protection Systems – Conprove
The reliability and continuity of operation in electric power systems depend directly on the proper functioning of protection systems. In this context, IEDs (Intelligent Electronic Devices) play a fundamental role, as they are responsible for detecting, isolating, and signaling faults in real time. However, to ensure that these devices are operating effectively, they must be subjected to rigorous testing that simulates real operating conditions of the electrical system. This is where closed-loop testing comes into play.
Why perform closed-loop testing?
For many years, open-loop tests with steady-state signal injection were sufficient to validate relays and IEDs. However, this type of testing does not cover dynamic aspects of the electrical system, such as:
Current transformer (CT) saturation;
Ferroresonance;
Switching transients;
Harmonics;
Frequency variations;
Interactions between protection devices.
These phenomena, often present under real fault conditions, are not properly reproduced in conventional tests. Consequently, it becomes impossible to evaluate the actual behavior and response of IEDs under complex events. Therefore, closed-loop testing has been gaining ground as an essential methodology in protection engineering.
What is closed-loop testing?
Closed-loop testing consists of a complete simulation of the electrical system, including its sources, loads, lines, transformers, and protection devices, with all elements interacting with each other in real time. In this approach, the system is modeled with a high degree of fidelity, and different contingency scenarios are applied, such as single-phase, phase-to-phase, and three-phase faults, faults with resistance, and load imbalances.
The key characteristic of these tests is feedback: the device under test (IED) not only receives simulated signals (voltages and currents) but also interacts with the modeled system, influencing its behavior and being influenced in return. This continuous interaction is what defines the “closed loop.”
Conprove equipment and tools for closed-loop testing
To enable testing with this advanced approach, Conprove provides complete solutions that integrate high-performance, flexible, and precise hardware and software. Key recommended products include:
CE-67NET: Compact tester for testing and diagnostics in digital substations with full support for IEC 61850 / IEC 61869 standards.
CE-MNET4: Versatile tool capable of performing network testing and diagnostics in digital substations based on IEC 61850 / IEC 61869 standards.
CE-6707: Portable instrument, ideal for both field and laboratory use.
CE-6710: Universal multifunction tester with 6 current channels and 4 voltage channels.
CE-7012: Universal multifunction tester with 6 current channels and 6 voltage channels, capable of performing primary-level tests.
PS Simul: Software for power system modeling and electromagnetic transient simulation.
Benefits of closed-loop testing with Conprove
By using Conprove equipment and software, closed-loop testing becomes more accessible, reliable, and effective. Key benefits include:
Comprehensive analysis of the dynamic behavior of IEDs;
Verification of interactions between system elements;
Identification of failures to operate or undesired operations;
High accuracy in simulating real events;
Reduction of operational failures in the field;
Integration with relays from different manufacturers;
Compatibility with IEC 61850 and conventional protocols.
Additionally, the use of closed-loop testing directly contributes to the validation of protection engineering, increasing the reliability of the electrical system and promoting safer and more stable grid operation.
Conprove: Innovation at the service of electrical protection
Conprove is a pioneer in the development of national technologies for testing and simulation in electric power systems. With over 40 years of experience in the sector, it offers solutions that serve everything from research laboratories to utilities, industries, and protection and control engineering companies.
All products are supported by specialized technical assistance, periodic software updates, and customized training. This ensures that customers have all the support needed to achieve maximum performance from their testing tools.
