Interview With a Product: Littelfuse's EL731 AC/DC Sensitive Earth-Leakage Relay

This weekly Q&A will feature some of your favorite products uncensored and without their packaging.

Welcome to the inaugural edition of Interview With a Product. This weekly Q&A will feature some of your favorite products uncensored and without their packaging. Today, our interviewee is the EL731 AC/DC Sensitive Earth-Leakage Relay from Littelfuse. Thanks for joining us.

Littelfuse EL731 AC/DC Sensitive Earth-Leakage Relay: It’s great to be here.

Plant Services: What industry are you designed for?

L: Well, I'm created to detect low level ground faults in plants and equipment using VFDs, so I'd have to say any industry with electrical systems using high resistance grounding and variable frequency drives.

PS: So what exactly do you do?

L: I'm designed to detect ground currents, even in resistance-grounded electrical systems, down to 0 Hz.

PS: What sets you apart from the competition?

L: Well, the proliferation of variable-frequency drives (VFDs) creates difficult problems with ground fault detection. Ground fault detection is difficult on VFDs, especially at very low current; undetected ground faults can escalate into phase-to-phase faults. It is extremely difficult to reliably detect an earth fault on a VFD-driven motor load. Nuisance or false trips can be caused by noise on loads or feeders without a VFD, and on-board VFD ground-fault protection doesn‘t work in high-resistance grounded systems.

That's where I come in.

I'm made for protecting VFDs that may operate at low speeds, during which AC current approaches DC. I'm engineered to provide ground-fault protection in VFDs from 0 to 15000 Hz in one device.

PS: That's fascinating. What are some of your best features?

L: I can be installed in place of an existing ground fault relay without replacing the current transformer. Two CTs are required for the entire frequency range, or one CT can be used for only low- or high-frequency detection.

PS: Why should someone buy you?

L: I have a temperature input, metering capabilities, password-protected alarm and trip settings. An Ethernet communications port is also optional.

PS: How would people at your company describe you?

L: Well, Tony Locker has said that I'm the first relay to adequately address the common challenge of detecting ground faults in VFDs operating at low speed. He's quite the charmer.

PS: It looks like you're blushing a bit. Tell us more about Littelfuse.

L: Littelfuse is a leader in circuit protection, and they offer the industry’s broadest and deepest portfolio of circuit protection products and solutions. Littelfuse devices protect products in virtually every market that uses electrical energy, from consumer electronics to automobiles to industrial equipment. They're a great company to work for.

PS: And now it's time for a fun question. What is your favorite word?

L: Safety.

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