DEIF LSU-112DG Generator Load Share / Paralleling Unit

Description

Product Model: LSU-112DG
Product Brand: DEIF
Product Series / Type: Uni-Line Load Sharing / Paralleling Series

Key Features:

• Built-in frequency and power transducers, allowing internal measurement of generator output (voltage, current) and derivation of active power.
• Modes: standalone (frequency control), paralleling (power/frequency sharing) or grid parallel (power control).
• Outputs: dual relays for speed control (increase/decrease) plus outputs to paralleling lines for frequency (FS) and power (PS).
• Other features: LED status indicators, unload input, reference input control, DIN-rail or base mounting.

Role & System Context

In multi-generator installations, power plants, or standby power systems, one key challenge is load-sharing and smooth parallel operation of generator sets. DEIF’s LSU-112DG is designed to be the control logic between generators: it ensures generators share the load proportionally, maintain frequency, and cooperate smoothly in parallel or grid-tie modes.

Unlike simple governors that respond only locally, the LSU-112DG measures its own generator’s voltage, current, and (implicitly) power, and propagates frequency (FS) and power (PS) signals across all parallel units. These signals are used by each unit to adjust speed and load in a coordinated fashion. With proper calibration, a 100 kW unit and a 150 kW unit can share 250 kW in a 2:3 ratio—unless a “derating” setting is applied to adjust for prime mover or engine limitations.

It also supports standalone frequency control, meaning in island mode (no grid), each generator can maintain frequency by itself if it’s the only unit online. When synchronized to a grid, it can operate in power control mode, letting it maintain power output while the grid holds frequency.

Because the LSU-112DG includes its own measurement (voltage and current sensors internally), fewer external transducers are needed for many installations. But for unbalanced load cases or special configurations, the internal measurement can be bypassed in favor of external 4–20 mA transducers.

You will often find LSU-112DG units mounted on DIN rail or base, close to generator control panels or in auxiliary control cabinets, connected to engine governors, breaker logic, and paralleling buses.

Technical Features & Benefits

Internal Measurement & Transducer Logic

• The built-in power and frequency transducer uses the internal current and voltage measurements to compute instantaneous active power (I × cos φ).
• For 3-phase installations, the standard coupling is 1W3 (one-element 3-phase, 3-wire, balanced load).
• If the load is unbalanced or complex, you may connect an external power transducer (4–20 mA) to terminals 31/32, bypassing the built-in transducer.
• The system supports external frequency transducers if higher stability or calibration is desired. Otherwise internal frequency measurement is used.

Control Output & Regulation

• Two control relay outputs (SG ▲ and SG ▼) drive speed commands: one to increase speed, one to decrease it. These relays typically interface with the engine’s governor control (mechanical or electronic).
• The regulation is a P (proportional) controller: the unit uses a proportional band (Xp), minimum ON time (TN), and period time (TP) settings to tailor response.
• There is a deadband region where small deviations do not cause control action, to prevent hunt or chatter.
• The unload input allows the unit to bring the generator to zero power (e.g. when a unit is taken offline), and disconnect it from the paralleling lines.

Paralleling / Sharing Lines

• FS (Frequency Sharing Line): each LSU-112DG broadcasts its frequency deviation (or setpoint) to the paralleling bus, enabling each unit to see others’ frequency state and adjust accordingly.
• PS (Power Sharing Line): each unit also shares its computed power or setpoint, so that load can be allocated proportionally.
• The outputs on FS and PS are analog lines (–5 V to +5 V) corresponding to deviation ranges, with typical nominal value at 5 V under unity power factor.

Protection, Self-Monitoring & Indicators

• The LSU-112DG includes a self-monitoring function: it verifies that the embedded microcontroller and firmware are operating. A solid green POWER LED implies normal operation; a flashing green (2–3 Hz) implies fault condition.
• A status output (terminals 17/18) opens if the supply is lost or the program is malfunctioning.
• LED indicators are also provided for voltage presence (UG) and “activated” control (unload or sharing active) states.

Technical Specifications Table

Below is a concise spec table excerpted from the DEIF LSU-112DG data sheet and installation instructions.

Installation & Maintenance Insights

From field practice and instructions in DEIF’s manual, here are tips and cautions when using LSU-112DG:

Mounting & Physical Installation

• Mount the unit on a horizontal 35 mm DIN rail, or secure it via base mounting screws. Avoid tilting the rail when multiple units are stacked.
• Leave at least 50 mm clearance above and below the unit when mounting adjacent relays or modules to allow airflow and heat dissipation.
• The DIN rail must be horizontal when multiple units share the rail; misalignment may affect calibration or reference stability.

Electrical Wiring & Connections

• Voltage input (Un): connect line inputs to terminals 24 / 26 for standard coupling (1W3 or 1W) per wiring diagrams.
• Current input (IL1): standard current transformers connect to terminals 28 / 29. If internal transducer is not used, external transducer on 31/32 should be wired (4–20 mA).
• Unloading contact: wire a potential-free N/O relay to terminals 33 / 34 to implement zero-power unload control.
• Reference / control input: terminal 35 (Ref) and 36 (⊥) handle 0.5–5 V signals for local power control mode. If unused, short to common.
• Paralleling lines: connect FS (term 38) / FS common and PS (term 40) / PS common to shared lines among all parallel units.
• Relays: SG ▲ (43/44) and SG ▼ (45/46) contacts must interface via external relays when driving DC pilot motors. Always include transient suppression across external relay coils.

Always ensure inputs do not exceed 110 % of nominal values (voltage or current), as that could impair measurement accuracy or trigger internal protection.

Commissioning & Settings

• Set nominal frequency (50 Hz or 60 Hz) and calibrate Xp (proportional band) and TN (minimum ON time) to match governor dynamics. Improper tuning can cause instability or hunting.
• Use the derating potentiometer to adjust output share capacity relative to machine size—in multi-unit setups, this ensures proportional load sharing.
• Test with intentional load changes and verify that the system rebalances load properly. Monitor FS and PS lines for consistent analog signaling.
• Validate the self-monitoring function: a steady green LED means healthy operation; a flashing LED (2–3 Hz) indicates a fault.

Maintenance & Diagnostics

• Periodically check wiring terminations (voltage, CT, relays) for tightness, corrosion, or damage.
• Use the status output and fault LED signals to detect early issues.
• If module misbehaves, isolate by powering it down and test each section (voltage, current, relays) separately.
• Keep a spare LSU-112DG (or compatible replacement) on hand—critical units in power plants must not remain offline long.