The Relay Race: Choosing the Right Equipment for Your Mine

Stay Informed

Over the last fifty years or so, advancement in technology has created incredible diversity of choice in the world of generation protective relay – however, many operations are relying on the same relay systems they implemented close to thirty years ago without much thought. With options ranging from solid-state, to electromechanical and microprocessing, how can decision makers be sure that they’re using the best tool for the job?

Understanding the differences between the types of relays available and their features will help you determine if an equipment update might be necessary or simply worth considering to improve your operational processes.

Three Main Relay Types

In mining environments, the three most commonly used relay types are:

  • Solid-state relays (SSRs)
  • Electromechanical relays
  • Microprocessor relays

SSRs are considered the “old standard” in mining. They are designed to use a system of switches with each switch controlling a single process. One of their major benefits is size as they are the smallest-profile relay available allowing for the greatest flexibility in application. They are much less sensitive to vibration or shock, consume less power with lower operating voltage and produce no magnetic field or electrical noise.

Electromechanical relays offer a greater level of control than SSRs as they can rely on a power source (battery or circuit) to incorporate features such as push-to-test manual operation and time delays allowing for adjustable speeds. They might feature expandable decks to allow for additional switch poles and convertible contacts that allow for reconfiguration of standard state between closed or open. They are also safe for explosion-proof applications as they will not spark or produce other thermal effects under conditions that may ignite a gas mixture.

Microprocessor relays are they newest and most advanced technology to enter the market. They are more accurate than SSRs or electromechanical relays and requires less maintenance. Since the relay units are comprised of a single enclosed system designed to operate multiple switching functions, they are less susceptible to dirt and debris and have a lifespan of approximately 15 years.

This type of relay helps enhance personnel and equipment protection by allowing networked communication and control of an entire breaker system, including the ability to program complex control logic.

What to Consider When Replacing Relays

If the time has come to upgrade your relay system, there are several factors to consider, including:

  • Average Temperature: If the wrong relay is selected, overheating and malfunction or failure can occur in instances where the environment is extremely hot.
  • Other Environmental Factors: Consider the levels of moisture or gas in the air, as well as the amount of dirt and debris, or the presence of corrosive materials. Choose the relay that will best meet the demands of your operation.
  • Critical Need: How critical is the specific function of the relay being upgraded? Is it tied to major operational and/or safety functions, or would a certain level of downtime be acceptable? Depending on how extensive the damage from potential incidents may be, operations could be shut down for days, weeks or months, costing your company hundreds of thousands of dollars in lost production time.

Avoiding Downtime and Hazards

Although equipment upgrades can be costly and time-consuming, taking a proactive approach to evaluating and upgrading your relay system(s) when possible is the best way to prevent greater exposure to safety hazards and operational downtime. In many cases, a consultant can help conduct an audit of your existing equipment in collaboration with your maintenance or operations managers and determine any recommended next steps.


The opinions expressed in this piece are solely Eaton's. They do not necessarily represent WESCO’s views.


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