Improper relay logic threatens your electrical assets and investments

Four programmable relay logic settings that will improve protection and add value

05/06/2014


In the event of an electrical system fault, the protective relay system isolates the affected components while maintaining stability within the rest of the grid distribution system. Many utilities and industrial facilities are replacing aging electromechanical and solid-state relays with new generation microprocessor-based relays that deliver many benefits including self-testing and diagnosis, reduced maintenance, simplified regulatory compliance, arc flash mitigation, event recording and reporting capabilities, and improved protection.

While microprocessor-based relays have vast potential functionality, many of the relays’ capabilities and advantages often go unrealized. This happens for a number of reasons, including:

  • Lack of owner awareness: Custom relay configuration has only recently become an option.
  • Simple oversight: Owners may overlook the need for relay customization and programming during the estimating, bidding, and specification processes.
  • Lack of knowledge and expertise: Engineers may not have the skill levels needed to program relays, or the designers and installing electricians may be unfamiliar with the relay’s capabilities.
  • Complexity issues: Custom programming can sometimes cause the system design to become overly complex. For simple applications, the effort needed to configure all the available features would not be worthwhile.

Unfortunately, relay capabilities have outpaced industry skill levels. Often a relay is installed as a direct replacement for aged or defective equipment and the subsequent logic programming is performed by personnel unfamiliar with the new equipment. Improperly programmed relay logic can lead to a wide range of protection system problems. For example, inappropriate logic settings can lead to repeated system misoperation, nuisance tripping, unplanned shutdowns, and production interruptions becoming a source of frustration for asset and facility managers. In these cases, managers often revert to the default logic settings just to keep the system running. While this is a tempting quick fix to a frustrating situation, this practice can ultimately result in even greater costs if the equipment is not adequately protected.

The key to leveraging the full range of microprocessor-based relay capabilities and optimizing system protection is to work with integration engineers that have the expertise to properly configure each relay to meet the utility or facility’s unique objectives. They consider the many differing needs of owners, engineers, utilities, and equipment manufacturers and then balance those with the requirements of local jurisdictions and industry standards (JCAHO, MSHA, NERC, FERC).

Within this framework, integration engineers begin to apply power system studies, such as short circuit, coordination, arc flash hazard, motor starting, and load flow analysis, to customize protection for each application. Ultimately, the relay system is easy to use, reliable, and only as complex as needed.

While project requirements will obviously be unique for each facility or utility that upgrades to microprocessor-based relays, there are at least four programmable relay settings that every facility should consider to improve their protection scheme and add value to the system.

1. Self-monitoring and diagnostics

Simplification of the control system through the reduction of necessary components and single points of failure is a tremendous benefit which can be further compounded by adding real-time monitoring and failure alert functionality. However, these benefits can only be realized if custom logic has been programmed and tested.

The reduction of necessary hardware components can be accomplished when previously installed hardware (e.g., 86 lockouts or 62 auxiliary timing relays) is emulated with customized logic programmed in the relay. For example, an 86 lockout relay previously installed as hardware can now perform the exact same functionality through operator interaction with the front panel display of the protective relay. Through the reduction of separate hardware components, the number of single point failures decreases, thereby increasing the robustness and reliability of the electrical system.


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