Complete Guide to DEIF GPU-3 Generator Protection Unit

Complete Guide to DEIF GPU-3 Generator Protection Unit

The reliability and flexibility of generator protection devices are directly related to power supply safety and equipment life in ship electric propulsion systems, marine engineering platforms, and land emergency power stations. The GPU-3 (Generator Protection Unit) launched by DEIF is a compact, fully digital microprocessor protection unit designed specifically for the protection, control, and monitoring of synchronous and asynchronous generators. Its rich protection functions, modular hardware architecture, and powerful programmable logic (M-Logic) make it an ideal choice for systems ranging from simple standalone to complex parallel systems. This article is based on the official technical data manual of GPU-3, and systematically reviews the protection functions, hardware structure, selection and configuration, communication interfaces, and engineering applications, providing a practical technical reference for electrical design engineers and on-site service personnel.

Product positioning and core features

GPU 3 is an independent generator protection device with a complete set of three-phase voltage/current measurement circuits (fully isolated) built-in, which can independently complete all-round protection of the generator. The core design concept is "on-demand configuration" - users can expand from the basic protection unit to a complete generator set controller with advanced functions such as synchronous grid connection, engine control, voltage regulation, analog output, etc. by selecting different software authorizations and hardware cards according to actual project needs.

List of Key Features:

Standard protection library: covering over 20 protection functions such as reverse power, overvoltage/undervoltage, overclocking/underfrequency, overcurrent (including definite time/inverse time), voltage imbalance, current imbalance, demagnetization, overexcitation, etc. (all corresponding to ANSI standard numbers).

Independent display and operation: Standard detachable display unit (DU-2), supports cabinet door installation (standard 3-meter cable), and can be expanded with up to two additional display screens or operation panels (AOP-1/AOP-2) through CAN bus.

Self diagnosis and redundancy: power on periodic self check, display in plaintext and drive status relay in case of fault; The engine control option includes a backup shutdown channel with independent power supply and processor, enabling safe shutdown in case of main processor failure.

M-Logic Micro PLC: A visual logic editor based on free PC software that allows users to assign specific functions or logic conditions to any input/output, enabling customized interlocking and control without the need for an additional PLC.

Full class society certification: meets the specifications of major classification societies and UL/cUL listings, and adapts to harsh marine environments.

Detailed explanation of comprehensive protection function

The protection functions of GPU 3 are organized according to ANSI standard numbering, and all protections have independent action values, delay, and on/off settings. Some protections also support multi-stage tuning (such as overcurrent 6-stage, undervoltage 3-stage, etc.) to meet the sensitivity and selectivity requirements of different operating conditions.

Protection function ANSI number can set segment number Typical applications

Generator reverse power of 32 2 segments to prevent stalling of the prime mover and protect the turbine/diesel engine

Generator overcurrent (timed/inverse time limit) 50/51 6-section+1-section inverse time limit phase to phase short circuit and overload protection, inverse time limit is used for thermal overload

Voltage dependent overcurrent 51V segment 1 reduces overcurrent setting at low voltage to improve sensitivity

Overvoltage/undervoltage (generator) 59/27 2-stage/3-stage prevention of excitation system failure or abnormal grid voltage

Over frequency/under frequency (generator) 81 each with 3 abnormal frequency protection segments to prevent turbine blade fatigue

Independent monitoring of grid connected busbars with over/under voltage and over/under frequency in multiple sections 59/27/81 to ensure grid connection conditions

Bus voltage imbalance 60 1 section detection bus side asymmetry fault

Current imbalance 46/60 1-stage protection generator stator winding asymmetric overheating

One section of demagnetization/overexcitation 40/32RV to prevent excitation system failure from causing generator out of step or iron core supersaturation

Reverse reactive power/leading phase 40 (power dependent) 1 section limits the generator from absorbing excessive reactive power from the system

In addition, the optional A package (power grid protection package) can also provide:

Time dependent undervoltage (27t)

Undervoltage and low reactive power (27Q)

Vector jump (78)

Frequency change rate (ROCOF, 81)

Positive sequence voltage low (27)

Directional overcurrent (67)

These features enable GPU 3 to not only serve as generator protection, but also as grid protection for grid connection points, meeting the requirements of distributed generation or islanding detection.

Hardware architecture and slot configuration

The GPU 3 adopts a standard 8-slot backplane structure, and each slot can accommodate different functional cards. Users can flexibly configure according to their ordering options. The following table summarizes the standards and optional functions for each slot:

Slot standard features optional features (option code)

#1 power supply (8-36V DC, 11W), 1 status relay, 5 relay outputs, 2 pulse outputs (kWh/kvarh), 5 digital inputs -

#2-H2 (Modbus RTU), H3 (Profibus DP), H8.2 (External I/O Module CAN), H9.2 (RS-232 Modbus)

#3- M12 (13 x digital input, 4 x relay output)

#4- M14.4 (4 x relay output), E1/E2/EF2/EF4/EF5 (various analog/relay combination GOV/AVR output)

#5 AC measurement (voltage, current, isolation) -

#6-F1 (2 × 0-20mA transmission output), M13.6 (7 × digital input), M14.6 (4 × relay), M15.6 (4 × 4-20mA input)

#7- Engine interface board (optional, including MPU input, multi-purpose input, start/stop relay, CAN communication)

#8-M13.8/M14.8/M15.8/M15.8 (same as # 6 expansion), H8.8 (Beckhoff I/O module CAN)

Key option combination precautions: Options in the same slot are mutually exclusive (e.g. E1 and E2 cannot be selected simultaneously), and some software options depend on hardware (e.g. voltage control D1 requires an analog output board). Engineers should refer to the "Hardware Overview" and option exclusion table provided by DEIF when selecting models to avoid conflicts.

Synchronization, engine control, and display layout

4.1 Synchronous grid connection function (option G2)

After selecting the synchronization function, GPU 3 can detect the voltage difference, frequency difference, and phase angle difference between the generator and the bus, automatically issue a closing command, and exit the regulation after closing, only retaining the protection function. This function is suitable for situations that require parallel or grid connection, without the need for additional synchronization relays.

4.2 Engine Control and Protection (Option Y7 or Y1)

This option requires the installation of an engine interface board (located in slot # 7), which has an independent power input (terminal 98/99, 8-36V DC, 5W) and an independent processor that can independently execute emergency shutdown in the event of a main CPU failure. Onboard resources include:

Magnetic electric speed sensor input (MPU, 0.5-70V AC, 10-10000Hz)

Three sets of multi-purpose inputs (configurable as 0-20mA, Pt100/Pt1000, RMI, 0-40V DC or digital input with wire breakage monitoring)

Multiple digital inputs (remote start/synchronization, remote unload/stop, start permission, operation feedback, etc.)

Relay outputs for startup preparation, starting motor, running coil, shutdown coil, etc. (all with wire breakage detection)

Two redundant CAN interfaces (for internal communication or J1939 engine interface)

This option allows the GPU -3 to function not only as a protector, but also as a complete generator set controller, especially suitable for automated cabins or unmanned power stations.

4.3 Display Layout Options

According to the order, there are three standard layouts for the display interface:

Y5 (GB control): Only displays generator circuit breaker control and measurement, suitable for pure protection applications.

Y7 (Engine Control): Emphasize engine start/stop and operating status.

Y1 (engine+GB control): The most complete interface, providing both engine and circuit breaker operations.

In addition, AOP-1 (16 programmable LEDs+8 buttons) or AOP-2 (with status relay, CAN communication) can be optionally selected for remote control panel, which can connect up to 5 AOP-2.

Communication interface and integration capability

GPU 3 supports multiple communication protocols, making it easy to integrate into upper level monitoring systems (SCADA/PLC):

Modbus RTU (Option H2): Two wire RS-485, capable of connecting to fieldbus networks, transmitting measurement values, alarms, and control commands.

Profibus DP (option H3): Suitable for mainstream PLC systems such as Siemens to achieve high-speed data exchange.

Ethernet TCP/IP (Option N): Supports Modbus TCP/IP, EtherNet/IP, and can send SMS/email alerts for remote operation and maintenance.

CAN bus: Built in two CAN channels (slot # 7 standard), supporting internal multi machine communication (for load distribution between multiple GPUs -3 or PPM -3), and optional H5/H7 for direct communication with engine ECU (J1939, MTU MDEC, etc.).

All communication interfaces are isolated from the measurement circuit to ensure reliability.

Technical parameters and engineering adaptability

6.1 Measurement and Accuracy

Voltage measurement: 100-690V AC (phase to phase), accuracy level 1.0, capable of withstanding 4 times rated continuous and 80 times 1-second overload.

Current measurement: 1A or 5A CT input, power consumption per phase 0.3VA, overload capacity 4 × In continuous, 20 × In for 10 seconds.

Frequency range: 30~70Hz.

Temperature effect: ± 0.2% full-scale/10 ℃.

6.2 Power Supply and Power Consumption

Main power supply (terminal 1/2): 12/24V DC nominal (8-36V DC operation), maximum power consumption of 11W, built-in 10ms power-off hold (drops from 24V to 0V).

Engine interface power supply (terminal 98/99): independent power supply, maximum 5W, isolated from the main power supply.

6.3 Environment and Machinery

Working temperature: -25~70 ℃ (-25~60 ℃ with N option included, UL limit 55 ℃).

Storage temperature: -40~70 ℃.

Altitude: 0-4000m, derating is required for distances above 2000m (voltage ≤ 480V for 3W4 wiring, ≤ 690V for 3W3).

Vibration and Shock: Meets IEC 60068-2-6 and IACS UR E10, capable of withstanding 30g/11ms shock (durability).

Protection level: IP20 for the host and IP40 for the display unit (up to IP54 with added sealing gasket, meeting marine requirements).

6.4 Input/Output Characteristics

Digital input: Bidirectional optocoupler, conduction threshold 8-36V DC, turn off<2V, typical impedance 4.7k Ω.

Relay output: 250V AC/30V DC, 5A (resistive), capable of continuous 2A or short-term 4A (5s/15s duty cycle).

Analog output (optional): 0-20mA or ± 20mA, active output (internal power supply), maximum load of 500 Ω, update rate of 250ms (transmission) or 100ms (regulation).

Multi functional input (slot # 7): can connect Pt100/Pt1000, 0-20mA, RMI (0-1700 Ω), 0-40V DC, with an accuracy of ± 1%, and has the ability to detect wire breakage.

Selection and configuration examples

DEIF divides GPUs into three basic models (variants):

01: With display unit, standard delivery (including 3-meter cable).

02: No display unit (suitable for integration into existing display systems).

03: Equipped with display unit and option F1 (2-channel analog transmission output).

On this basis, users can add the desired options, such as:

Synchronization function required → Add G2

Need engine control → add M4 (hardware board) and Y1/Y7 (display layout)

Modbus communication required → add H2

High precision measurement at level 0.5 is required → add Q1

IP54 protection is required → add L (indicating sealing gasket)

Selection example (from manual):

2912110030-03 GPU-3 Marine03 M4 Y1 H2

Indicating display, F1 output, engine control board, engine+circuit breaker display layout, Modbus RTU communication.

Debugging, Configuration, and Maintenance Tips

PC Tool: DEIF provides Multi line 2 PC Utility software (USB connection) for free, which can monitor all measurement values online, modify parameters, update firmware, and customize logic using M-Logic editor.

Parameter download and backup: It is recommended to upload and save the complete parameter file before debugging for quick recovery in case of failure.

Synchronization parameter setting: If synchronization is enabled, it is necessary to carefully set the pressure difference, frequency difference, closing lead angle, etc. to avoid impact.

Broken wire monitoring resistor: When the digital input enables broken wire monitoring, the external contacts must be connected in parallel with a 270 Ω± 10% resistor, otherwise the system will report a "broken wire" fault.

Shielding and grounding: Communication lines, MPU lines, and analog signal lines should use shielded twisted pair cables, with the shielding layer grounded at one end, and the terminal resistance (such as 120 Ω for CAN) connected as needed.

Regular self check: GPU -3 power on self check, and relay/output testing can also be manually triggered through the menu during operation to ensure circuit integrity.