DEIF GPU/2/GS | Genset Protection Unit, 2nd Gen

Description

Product Introduction

That remote telecom site in Nevada—the one with the three diesel gensets in parallel—had a nuisance trip every time they started the third set. The protection relay would trip on “reverse power” even though the set wasn’t loaded yet. The local tech had already swapped the CTs, the wiring, even the genset controller. I drove out, looked at the GPU/2/GS settings, and found the reverse power threshold set to 2% of rated. On a no-load start, the genset motored briefly—2% was too sensitive. Bumped it to 5%, problem gone. The relay was fine. The settings weren’t.

The DEIF GPU/2/GS is a second-generation generator protection unit from DEIF, built for stand-alone or parallel genset applications. It monitors all three phases continuously: voltage (phase-to-phase and phase-to-neutral), frequency, and phase sequence. It has four programmable relay outputs that can be set for alarm or trip on any of the measured parameters. The “GS” suffix indicates it’s the general-purpose version with standard protection functions—no built-in reverse power measurement (that requires external transducers), but it can accept an external 4-20 mA signal for that. The front panel has a backlit LCD showing all measured values and a keypad for programming. It’s a workhorse unit—simple, reliable, and still found in thousands of genset control panels worldwide.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

A protection relay gets a full functional test. Here’s our process.

1. Incoming Verification
   • Match the model: GPU/2/GS. (There’s a GPU/2/GSR with reverse power built-in—different unit.)
   • Visual inspection: Check the front lens for scratches. Look at the terminal block—no cracks.
   • Inspect the enclosure for dents or bent mounting tabs.
2. Power-On Self-Test
   • Apply 24V DC auxiliary power.
   • Watch the display—it should light up, show the software version, then go to measurement mode.
   • No error messages, no flickering display.
3. Voltage Measurement Test
   • Apply three-phase voltage from a calibrated source (we use a Fluke 6105A).
   • Test at 100V, 230V, 480V, and 690V (phase-to-phase).
   • Verify displayed values are within ±0.5% of the source.
   • Test phase sequence: swap two phases, verify the relay detects and alarms.
4. Frequency Measurement Test
   • Vary the source frequency from 45 Hz to 65 Hz in 0.1 Hz steps.
   • Verify displayed frequency matches within ±0.1 Hz.
   • Test under/over frequency trip points by ramping slowly—measure actual trip vs setpoint.
5. Analog Input Test
   • Connect a 4-20 mA calibrator to the analog input.
   • Program the input for reverse power scaling (e.g., 4 mA = -100 kW, 20 mA = 0 kW).
   • Inject 4, 12, and 20 mA—verify the displayed power value matches within 1%.
6. Relay Output Test
   • Program each relay for a different function (e.g., relay 1 = overvoltage trip).
   • Force a trip condition, verify the relay changes state and the front LED indicates.
   • Measure contact resistance—<100 mΩ.
7. Isolation Test
   • 500V megger between voltage inputs (shorted) and auxiliary supply terminals—>10 MΩ.
   • 500V megger between relay contacts and chassis ground—>10 MΩ.
8. Thermal Soak
   • 4 hours at 55 °C in a thermal chamber, running with 480V applied.
   • Monitor displayed values for drift—must stay within spec.
9. Final QC & Packaging
   • QC sticker with test date and operator initials.
   • Wrap in anti-static bag.
   • Double-box with foam padding.
   • Test report included—voltage/frequency accuracy, relay timing.

Field Replacement Pitfalls

I’ve swapped these in power plants, data centers, and offshore rigs. Here’s where people go wrong.

❗Voltage Input Connection
The GPU/2/GS measures phase-to-phase voltage. If you wire it phase-to-neutral (in a delta system), the readings will be off by a factor of √3. Check your system configuration before wiring.

CTs for Reverse Power
The “GS” version doesn’t have built-in CT inputs. If you need reverse power protection, you must use an external transducer (4-20 mA output) and wire it to the analog input. Don’t assume it’s built-in.

Relay Programming
The relays are programmable. If you replace a unit without uploading the old configuration, the new one will have factory defaults—which might not match your application. Always back up the settings from the old unit (via the front panel or software) before replacement.

Auxiliary Supply
It needs 24V DC auxiliary power. If you assume it’s powered from the measured voltage (like some old analog relays), it won’t power up. Check the connections.

Phase Sequence
The GPU/2/GS detects phase sequence. If your generator has the phase rotation wrong (A-B-C vs A-C-B), the relay will alarm. Swap any two phases to fix it.

*Nail these five, and your GPU/2 will protect that genset for decades.*

New Original vs. Refurbished: Why It Matters

“New Original (New Surplus)” means this unit was manufactured by DEIF, packed in its original box, and never installed. The display has zero hours, the relays have never cycled, and the electrolytic capacitors in the power supply have zero hours.

Refurbished risk in plain terms
A refurbished GPU/2 often comes from a decommissioned genset. It may have run for years in a hot engine room. The display may be dim (backlight aging), the relays may be worn, and the power supply capacitors may be near end-of-life. A refurbisher tests it at room temperature and calls it good. Six months later, in a hot cabinet, it fails.

Real cost of a refurbished failure
If this relay fails to trip on overvoltage, you could destroy the generator’s insulation. The cost of rewinding a medium-voltage generator dwarfs the price difference. If it nuisance trips, you lose backup power—critical for data centers or hospitals.

What we provide as proof

• DEIF box (or photos).
• Serial number recorded.
• Test report with voltage/frequency accuracy.
• Relay timing measurements.
• 12‑month warranty.

Pricing context
We’re priced 35% above the cheapest “pulled” GPU/2s and 20% below DEIF’s current list price. That pays for the full calibration, the 4‑hour thermal test, and the warranty that covers replacement if a relay fails.

Performance Benchmarks & Test Results

Test conditions: 480V AC, 60 Hz input, 24V DC auxiliary, ambient 24 °C.

We keep the full test data—ask, and we’ll email the PDF.

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