How Protective Relay Systems Can Save Electrical Engineers

How Protective Relay Systems Can Save Electrical Engineers
Frequently found in medium and high-voltage systems, protective relays help ensure the safety and reliability of today's electrical power systems. These tools are compliant for IEC 61850 environments, can handle high burden electromechanical conditions, and are often able to test multiple scenarios in an all-in-one device. Protection test engineers utilize relay equipment throughout the lifespan of a relay to conduct any one of these three common protective relay tests:

Acceptance Testing/Troubleshooting

This is a benchmark test, often performed by the manufacturer or end-user, to verify if the device or product meets quality assurance standards. In a manufacturer setting, this test will determine if the device under test (DUT) is acceptable for sale. Troubleshooting can also help predict and assess how an electrical system may behave under certain stressors or phenomena.​


Testing that falls under this category relates to the examination of relay functions as they operate in the installation environment. Commissioning begins from the point of installation completion, where the first set of specs will be recorded and used as a point of reference later. Commissioning tests for accuracy, ratings, calibration, and conformity across the system.

Intermittent Maintenance

Regular maintenance tests are essential to protecting the integrity of a relay after commissioning. Maintenance testing helps identify any defects or corrosion that could impact the relay or cause it to fail. It’s a preventative measure that saves time and money down the line that would have otherwise been spent on costly, time consuming repairs and replacements.

As the electrical industry has grown and evolved, so too have the assortment of protective relay tools available to service electrical networks. These are just a few different protective relay systems you will likely need as a protective test or electrical engineer.

Electromechanical Relays

Traditionally, this is the umbrella category most protective relays fall under. Electromechanical relays are accurate, dependable, and reliable. There are two variations that can be described as electromechanical:

Magnetic Attraction Relays

Magnetic attraction relays react instantaneously, with no intentional time delay. They can generate with either AC or DC on the coils – therefore, relays using this principle are affected by DC component of an asymmetrical fault.

Induction Relays

This basically relates to induction motors, which come in many variations and provide accurate pickup and time-current responses for a wide range of simple or complex system conditions.

Solid-State Relays

Solid-state relays perform all the functions of electromechanical relays, but because of their circuitry and microprocessors, they can provide many additional functions. Smaller and more compact than their mechanical equivalents, solid-state relays are precise, and require less power to operate, thereby placing a smaller load burden on CTs and PTs.

Multi-Functional Relays

Many protective relay test sets these days combine multiple testing outputs/phases in one complete tool, consolidating the work needed to be done and simplifying testing for the engineer. They can alternate between unique testing needs, frequently combining single and three or more phase testing, AC and DC voltage, varying current outputs, and more.

Whatever your individual needs, today’s diverse market of protective relay test sets makes it relatively painless to find the right tool for you. If you need guidance, the experts at Advanced Test Equipment Rentals are able to assist you in narrowing down a protective relay manufacturer, make and model that will help you complete your project quickly. Please feel free to connect with our electrical rental agents directly at (800) 404-2832.