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Primary Injection vs Secondary Injection Testing for ANSI 50/51 Overcurrent Relays (Substations)
If you work around substations long enough (generation, transmission, or distribution), you’ll notice something: most protection issues aren’t “mysteries”. They’re usually a chain problem—settings, wiring, CT polarity, logic, trip circuit, breaker mechanics, or documentation that didn’t reflect what was actually in service. In my day-to-day at EuroSMC, we manufacture primary injection, secondary injection, and measurement... Learn More
Maritime protection systems on modern vessels: from theory to real-world testing
Introduction: from the single-line diagram to blackout… or reliability Electrification has turned the modern ship into a highly stressed microgrid.Integrated Power Systems (IPS) connect propulsion, hotel loads and auxiliaries to common main switchboards, often in closed-ring configurations with multiple generators feeding the same busbars. This architecture is extremely efficient and redundant, but only under one... Learn More
Understanding the Heat Run Test with Primary Current Injection
What a Heat Run (Temperature-Rise) Test Proves and Why It Matters A heat run test—also called a temperature-rise test—verifies that equipment runs within safe thermal limits under rated or near-rated load for an extended time. You circulate a controlled current through the full primary path and monitor temperature rise at hot-spot locations. This exposes loose... Learn More
Directional Relays and Relay Testing: A Practical Guide with Secondary Injection
What a Directional Relay Does and Why It Matters Directional relays are not just overcurrent devices with extra logic. They compare current from CTs with voltage from PTs to determine the fault direction. That single capability is decisive in parallel feeders, ring networks, and multi-infeed grids, where faults may be fed from both sides. I... Learn More
Understanding the IEC 61850 Protocol: A New Era in Electrical Protection and Control
Introduction The IEC 61850 protocol is an international standard designed for substation automation systems (SAS). It enables seamless communication between Intelligent Electronic Devices (IEDs), regardless of the manufacturer, providing interoperability and efficiency. Today, IEC 61850 is widely used in medium- and high-voltage substations and is gaining importance in renewable energy facilities like wind and solar... Learn More
Testing Recloser Logic: More Than Just “Did It Close?”
Once a recloser logic failed on a 33kV line during a storm. First trip was good. Second trip was good. Then it tried to reclose into a still-faulted line — and didn’t lock out. You know what happened next. Recloser that did not operate properly And on the photo above you can see a result... Learn More
How to Design a Maintenance Plan for Electrical Substations Step by Step
1. Why a Maintenance Plan? A clear maintenance plan for electrical substations boosts supply reliability, ensures personnel safety, and extends the life of critical assets. 2. Key Parameters to Build Your Own Plan Set Objectives & Scope What are your goals? (downtime reduction, regulatory compliance, cost savings) How broad is the plan? (all substations or... Learn More
Relay vs. Circuit Breaker: Key Differences and Why Both Must Be Tested
Relay vs. Circuit Breaker: Understanding Their Role in Protection Systems In substations and industrial power systems, relays and circuit breakers form the backbone of protection and control. But while both devices respond to abnormal electrical conditions, their functions are entirely different—and understanding that difference is critical for engineers in testing and maintenance. What is a... Learn More
Why Relay Testing Is Essential for the Safe Operation of Electrical Substations
Introduction At the heart of every substation lies a vital component: the protection relay. Though small, its role is huge — detecting faults and triggering disconnection before damage occurs. If it fails, the entire installation is at risk. This is why relay testing is not just a maintenance task — it’s a critical safety measure. ... Learn More
Analysis of Spain’s April 2025 Blackout: Causes, Low-Inertia Grid Risks, and Protection Solutions
1. Summary of the event On April 28th, 2025, Spain experienced a massive electrical blackout that affected the entire Iberian Peninsula, disrupting electricity supply across Spain and its interconnections with Portugal and France. According to Red Eléctrica de España (REE), the event was triggered by a sudden loss of 15 GW of generation within just... Learn More
