Protective Relay Testing and Maintenance

ETT performs acceptance and maintenance testing of Electromechanical, Solid state, and Microprocessor relays.

We have experienced field technicians and the equipment required to set or program, depending on Electromechanical or Microprocessor, test and calibrate all makes and styles of protective relays, including meters. You can be confident that your protective relays and meters will be properly set up and functioning properly. If there are any defects, we will work to help YOU get them resolved.

Types of Relay Testing

The type of testing required for each relay varies by which stage of a project are you in. Is this new construction? Have these relays been placed in service? Are you looking to set up a maintenance program? Below will explain a little about our types of testing.

1.) Acceptance Tests

New installed relays that have not been placed in service. A coordination study needs to be provided by an Engineering Firm. Our field technicians will not “guess or recommend” when it comes to protection. We care about the equipment operators and the equipment.

2.) Maintenance Tests

Maintenance testing applies to relays that have already been in service on energized equipment. Relays are typically installed on medium and high voltage equipment. Relays that are installed on low voltage equipment are usually utilized as voltage protection for automatic transfer schemes.

Some of the steps involved in maintenance are:
  • Inspection and burnishing of contacts (Electromechanical Relays)
  • Automatic self-test of relay (Microprocessor Relays)
  • Adjustments checked.
  • Trip breaker via relay output contact
  • Screws checked for tightness.
  • Covers cleaned.
  • Tests performed As Found and As Left
  • Types of Relays Tested

3.) Repairs

Sometimes, repairs can revive a relay. Some equipment manufacturers offer warranties that replace the defective components. These warranties can be limited, or lifetime depending on the manufacturer. We can help lead you to the best and most efficient option.


What can ETT do for you?

The following is a partial list of relays that ETT tests:

Microprocessor-Based: This relay is most typically related to a computer. It utilizes a microprocessor to compute and initiate the necessary actions to provide protection.

  • Schweitzer Engineering Laboratories – SEL Series (SEL-751, SEL-300, SEL-411, SEL-587Z, etc.)
  • General Electric – UR Series & SR Series Relays (Multilin 750, 850,etc.)
  • ABB – MMCO, Transformer Protection and Distribution Protection Units (TPU & DPU)
  • Siemens – SIPROTEC Series (7UMxxx, 7SJxxx, etc.)

Solid-State: A solid state relay is made up of semiconductors instead of mechanical parts.

  • General Electric – SLD-41, SLD-51, STV, etc.
  • ABB (Westinghouse) – 25, 27, 59, 27/59, LCB-II, etc.
  • Basler – BE1 Series; -27, -59, -27/59, -25, -51, -81 O/U

Electro-Mechanical: This relay consists of an electromagnetic coil and a mechanical movable contact that operates on a disk.

  • General Electric – BDD, CEB, CEH, CEY, CFD, CFVB, GCX, GCY, GGP, IAC, IAV, ICW, IJC, PJC, PVD, etc.
  • ABB (Westinghouse) – CO, CV, HU, IRP, KAB, KC, KD, KDTG, KDXG, SC, SV, TD, etc.

Want to learn more about the benefits of testing? Check out these case studies from the ETT Blog: