Electrical • Sensors, Relays & Switches • Ground Fault Relays

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  • Bender, Inc.

    Bender distributes a wide selection of ground fault relays, including voltage, current, and continuity relays. For AC/DC systems, the VME420 is an appropriate voltage relay that provides monitoring from 0 to 300 V; it also features operation LEDs for power and alarm and an LCD screen for easy operation. For three-phase AC systems, the company offers the VMD420, which monitors from 0 to 500 V. In total, there are 15 voltage relay models, each with a unique set of characteristics and applications. Next, the company sells seven types of current relays, including the CME420 Series for undercurrent and overcurrent in AC systems (up to 16 A), and the CSE141, which detects overcurrent in AC systems and offers programmable response values, response delays, and hysteresis using its potentiometers. Meanwhile, the GM Series is the company's line for continuity relays, meant for AC and offline systems. The sole model currently in this series is the GM420, which monitors the PE conductor in AC systems and displays on its LCD screen the resistance of the loop as well as the extraneous voltage. In addition to the products already mentioned, Bender produces SAD Series asymmetry relays, SED Series phase relays, and SFE Series frequency relays.

  • Omron

    For protection in low-voltage circuits, Omron Industrial Automation offers its K6EL DIN 48 x 48 mm ground fault relay. This product continuously monitors and detects ground faults due to deterioration of insulation in electrical devices. It supports currents from 50 A to 600 A, depending on the zero-phase current transformer (ZCT) being used, with a sensed current and non-operating current from 50% to 100% and 0% to 50%, respectively, of the rated sensed current (i.e., 50-600 A). Furthermore, in addition to remote monitoring capability (see automatic-reset models), the ground fault relays are fully compatible with through-type ZCTs, allowing for easy operation testing.

  • ABB

    A host of electromechanical relays are available through ABB, including four types of ground relays. The KDXG ground distance relay is a high speed, single-phase, reactance-style relay meant to be used in conjunction with a ground directional-unit timer relay and auxiliary current transformer Type IK in order to achieve transmission line protection.  Another option is the KRQ high speed directional overcurrent relay, used to detect ground faults on transmission lines, feeder transmission lines, and feeder circuits, and to provide directional ground fault protection in K-Dar carrier relaying schemes. Next, the KRT directional ground and timer relay is a dual polarized unit with a static two-step timer; it offers directional supervision of all tripping, and controls the switching of the KDXG from its original zone setting to zone 2 and then 3. Lastly, the SDG static ground distance relay serves a single zone, detecting faults on subtransmission or transmission lines.

  • Cincinnati Babbitt, Inc.

    The Allen-Bradley arcing ground fault detection system, which includes both a relay and a sensor, is available in Classes I and II. The relays in Class I systems, which function without high current-inhibiting circuits, support maximum line voltages of 600 V in shunt-trip circuit breaker applications, and 7,200 V in medium voltage controllers. Response time is 50 ms nominal, plus the controller drop-out time. In Class II systems, which have high current-inhibiting circuits, the ground fault relays are highly variable. There are six NEMA sizes, each supporting voltage ranges up to 575VAC. Full load current on these systems ranges from 11 A to 540 A, while horsepower ranges from 7.5 to 400 Hp.

  • Controlab Inc

    Controlab manufactures two series of ground fault relays for rapid and precise identification of the ground fault source, resulting in added protection against shock hazards, fire damage, burnt motors, and loss of production. The VT-120 is a small unit with one fixed calibrated current leak detection threshold (100 msec) and one fixed calibrated fault detection response time (500mA). By contrast, the IFT-120 has four settings for both leak detection thresholds (100mA, 300mA, 1A, 3A) and response times (30 msec, 100 msec, 1 sec, 3 sec). Both units, however, offer one normally open contact, one normally closed contact, a green LED to indicate proper 120 VAC supply, a red LED to indicate an alarm state, and connectors for a reset switch.

  • CR Magnetics

    The CR 7310 by CR Magnetics is a ground fault relay that is manufactured with many setting possibilities. Trip status options are EH, EL, LH, and LL, and supply voltage choices are 120 VAC, 240 VAC, or 24 VDC. There are a host of programmable trip ranges, as well, from 0.011-0.1 to 0.1 AAC, to 101-10 to 100 AAC, and four trip on delays: no delay, 01. to 1 sec, 0.5 to 6 sec, or 2 to 25 sec. Finally, the trip point dial can be either calibrated dial or fixed trip point, and the output options are ELR, NPN, and TRC.

  • GE Digital Energy

    GE Digital Energy offers three series of ground fault relays. The GFA Series has operating ranges that include trip currents of 10, 15, 20, and 75 A, and time delays from 0.01 to 20 sec. The self-powered units run on 50/60 Hz frequencies and their protectors provide insulation resistance exceeding 100 megohms when tested at 500 VDC. Next, the GFM Series has an adjustable operating range with trip currents from 1.5 to 65 A, and time delay from instantaneous to 36 cycles. It is designed for all polyphase applications, especially motor control, motor control centers, and high voltage starters. Finally, GE manufactures the BGFL Series with trip currents from 5-60, 30-360, or 100-1,200 A, and adjustable time delays from 0.1 to 1 sec. Unlike the models listed previously, it requires an input power of 2 VA plus shunt coil requirements. It is also designed to protect electrical equipment rather than personnel.

  • i-Gard

    I-GARD produces a comprehensive line of protective relays that can meet almost any application requirement. The Falcon model relay is designed to protect operating personnel and equipment in case of an arc by initiating a tripping signal in <1 ms. The DSP OHMNI is a high resistance grounded relay system that offers protection for up to 50 individual feeders; it also provides integral resistor monitoring, main-tie-main protection, and choice of instantaneous or time delay feeder tripping. For the mining industry, the GCHK-100 is a viable option; the relay is constructed for trailing cables up to 4,160V. Additional models include the MGFR, that has zone selective instantaneous protection from 10mA to 1,200A; the mGard, for motors, feeders, and motor controls centers from 10mA; the Sentri, which has 40 trip levels from 100mA to 1,200A; and the VIA for visual indication and alarm on ungrounded distribution systems.

  • Littelfuse

    A wide selection of ground fault relays are available through Littelfuse. For supply voltages from 12 to 30VDC there is the PGR-2601-0D, with one normally open and one normally closed relay contact, sensitive to 1 to 20mA trips and meant for use in ungrounded DC systems such as industrial 24VDC control circuits. The PGR-2601-0T and PGR-2601-0U are similar units, but with higher supply voltage of 40 to 55 VDC and 120 to 240 VDC, respectively. These models provide selectable fail-safe or non-failsafe operating modes, non-volatile trip memories in order to retain trip state, and analog outputs for external metering. Moreover, they require no calibration, and respond to trips in as little as 50 ms.

  • Skymatic Controls

    Skymatic Controls offers two models of ground fault protection relays engineered to protect industrial equipment such as motors, transformers, and feeders from low magnitude ground currents. The GFR-2 is a CSA-approved relay housed in a standard track mount DIN enclosure. It has selectable trip ranges from 0.01 to 0.12 amp (Ni-core sensor only) up to 10 to 30 amp, as well as a 50 msec operating time and repeatability better than 1%. The GFR-3 is an enhanced version of the GFR-2; it comes with a built-in self-test circuit and adjustable time delay between 0.1 and 1.2 sec. Its tripping range and repeatability are no different from the GFR-2.

  • SMC Electrical Products Inc

    SMC Electrical Product's ground trip relay is designed for use with 120VAC undervoltage or shunt trip breakers on circuits up to 25A. It is factory-calibrated to trip at 5A ground fault current through a current transformer, and features a lockout circuit and indicating light that must be manually reset should a ground trip occur. Another product offered by the company is a combination ground monitor and fault relay. In this setup, the relay monitors changes in ground wire resistance and ground fault current, and trips the circuit breaker if either increases to an unacceptable level. It monitors up to 4.5 ohms ground/pilot loop resistant, and like the model listed previously, trips at 5A ground fault current. Finally, the SGF-25 is a sensitive ground fault relay that predicts ground resistance conditions before the power circuit is energized. It uses a current transformer connected in a zero sequence configuration, and as an option, includes a remote display for monitoring the power circuit and changing the relay settings.

  • Schneider Electric

    Schneider Electric features the Vigirex ground fault relay system for protection and monitoring from 30mA to 30A. The relays and associated sensors measure the leakage current in electrical installations in order to detect levels that could damage the circuit. They can then either trigger a circuit breaker/switch (thereby interrupting the power supply) or an alarm, depending on user preference. Key features include panel or DIN-mount, a broad selection of sensors with a wide range of amperages (65 to 3,200A), and response times from instantaneous to 4.5 sec. Furthermore, the UL 1053-compliant equipment is compact enough for use in OEM equipment or branch circuits in automotive, healthcare, industrial, and semiconductor applications.