Littelfuse Announces a Complete Line of Protection Relay Products

New line includes Ground Fault Protection Relays, Motor Protection Relays, Feeder Protection Relays, Resistance Grounding Systems, and Supplemental Monitoring products.

CHICAGO, Illinois, August 10, 2009 - Littelfuse, Inc. (NASDAQ/NGS: LFUS) announced a complete line of POWR-GARD® Protection Relay products that increase worker safety and protect equipment by detecting hazardous electrical conditions before any damage occurs. POWR-GARD's protection relays are based on the leading product line in the mining industry and for the past 20 years have been proven to withstand the harshest conditions and meet the most stringent safety requirements. The new POWR-GARD protection relays are designed to improve safety and reduce downtime in industrial applications.

Each year Arc-Flash incidents in industrial facilities cause an average loss of more than $500,000 per event. According to IEEE, 90% of those Arc-Flash incidents are caused by ground faults. Littelfuse's POWR-GARD Ground Fault Protection Relays detect ground faults as they develop and alert personnel before a catastrophic event occurs. To significantly reduce the risk of Arc-Flash, safety managers can use Littelfuse's POWR-GARD Resistance Grounding Systems to physically limit ground fault currents to safe levels.

Littelfuse POWR-GARD Protection Relays address electrical problems in a various industries and environments-from the harshest conditions in petrochem and wastewater treatment facilities to the sterile environments of semiconductor manufacturing plants and hospitals. Typical applications are electrical circuits containing transformers, generators, switchgear, panelboards, variable frequency drives, motors, pumps, feeder lines, and grounding resistors.

The new line features 20 protection relays and systems and is described in a comprehensive 62-page catalog, including a 22-page technical overview section. To download a copy of the catalog visit

Littelfuse also launched "Ask the Expert" technical support email All technical questions are answered by Professional Engineers within 24 hours.

Importance of Ground Fault Protection

Ground faults are unintended conductive paths from a high potential line to ground, generally caused by deterioration in insulation. Many buildings built more than 25 years ago have ungrounded electrical systems. This means that when a ground fault develops, it will be difficult to locate and will typically lead to other problems such as transient overvoltages, which create unsafe conditions and can cause equipment damage.

Even in grounded systems, grounding problems such as electrical faults and short circuits will occur over time. They are most commonly caused by insulation breakdown, connections coming loose, or failures due to external factors, such as moisture, dust, vibration, or corrosive environments. Often, short circuits start as a low-leakage current that is left undetected and eventually escalate to a fire, an Arc-Flash incident or a Shock Hazard.

Types of Protection Relays

Ground Fault Relays improve the safety of workers by minimizing the conditions that may lead to Arc-Flash incidents and maximizing the uptime of critical operations by avoiding nuisance tripping. Some relays are prone to nuisance tripping, which means they disconnect power and interrupt critical processes when no fault is present. This costs an enormous amount of time and man-hours trying to locate the problem. To avoid the nuisance tripping that occurs with conventional ground fault relays, maintenance workers tend to increase trip points well above sensitive levels. This practice, although very common, is extremely dangerous as the settings are dialed up so high that the relay will trip well after the damage has occurred.

Littelfuse Ground Fault Relays use an advanced filtering technology that allows for early detection of developing ground faults, without the nuisance tripping common in many competing products. The Littelfuse relays can be used in ungrounded, solidly grounded, and resistance-grounded systems to protect critical, high-value equipment, and to meet National Electrical Code requirements for protection of ungrounded electrical systems (NEC 250.21B), solidly grounded systems (NEC 250.95), and resistance-grounded systems (NEC 250.36). The relays also have communications for remote monitoring.

Resistance-grounded systems are power systems with a resistor inserted between the system neutral and ground. This limits any ground-fault current to a predetermined, acceptable level. IEEE Std. 141-1993 states that there are no Arc-Flash hazards associated with ground fault currents if the ground fault current is limited to 5A. Simply by using a Resistance-Grounded System, safety managers can lower the risk of Arc-Flash incidents by 95 percent. However, if the resistor in the system fails, which usually goes undetected until a problem occurs, the system becomes ungrounded. To solve this problem, the Littelfuse Resistance Grounding Systems have an optional feature that continuously monitors the integrity of the resistor to ensure that the system is operating as intended.

Motor Protection Relays prevent expensive damage to motors caused by overloads, jams, phase loss or imbalance, as well as heat from non-electric sources, heavy startups or excessive operational cycles. Littelfuse Motor Protection Relays offer dynamic thermal curves, integrated protection, metering, and data logging functions that extend motor life and maximize process efficiency. A wide range of POWR-GARD Motor Protection Relays are available to protect any size motor. In addition, Littelfuse's products are user friendly and easy to program.

Feeder Protection Relays protect feeder circuits from overcurrent, ground faults, phase loss or other detrimental conditions. POWR-GARD's Feeder Protection Relays provide essential data for predictive and preventive maintenance, thereby extending the life of equipment, increasing its effectiveness, and improving safety.

Supplemental Monitors work together with existing protection to enhance electrical system safety and performance. Littelfuse Supplemental Monitors look for specific conditions, such as insulation breakdown, open ground conductor or resistor failure. Typically, monitors are added to existing protection, such as fuses, circuit breakers or protection relays to provide a low-cost solution to a dedicated problem.


Most POWR-GARD® Protection Relay products are available from stock; if not, the typical lead-time is 2-3 weeks ARO.

For More Information

For more information on POWR-GARD® Protection Relay products, or any of Littelfuse's circuit protection devices, visit the Littelfuse website at or call the Littelfuse Technical Support line at 1-800-832-3873.

About Littelfuse

As the worldwide leader in circuit protection products and solutions with annual sales of $531 million in 2008, the Littelfuse portfolio is backed by industry leading technical support, design and manufacturing expertise. Littelfuse products are vital components in virtually every product that uses electrical energy, including automobiles, computers, consumer electronics, handheld devices, industrial equipment, and telecom/datacom circuits. Littelfuse offers Teccor®, Wickmann® and Pudenz® brand circuit protection products. In addition to its Chicago, Illinois, world headquarters, Littelfuse has sales, distribution, manufacturing and engineering facilities in Brazil, China, England, Germany, Hong Kong, India, Ireland, Japan, Korea, Mexico, the Netherlands, the Philippines, Singapore, Taiwan and the U.S.

For more information, please visit Littelfuse's web site at


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