20/01/2026 BY
IN Uncategorized

SYMAP® LD (Line Differential Protection) is a high-precision digital protection relay from Stucke Elektronik, specifically designed to protect power cables and overhead lines in complex power grids.

1 It is the primary choice for ensuring the selective and high-speed clearing of faults on critical interconnecting lines.

1. Product Description

SYMAP® LD utilizes the Current Differential principle (ANSI 87L) as its primary protection method.

By comparing the current entering one end of a line with the current leaving the other end, it can detect internal faults with extreme sensitivity while remaining completely stable during external faults (through-faults).

Because it monitors both ends of the protected zone, it requires a dedicated communication link (pilot wire or fiber optic) between the two SYMAP® units at each end of the line.

2. Technical Parameter Table

CategorySpecification
Power Supply24V DC (Standard) or 110V/230V AC/DC (Optional)
Primary ProtectionLine Differential Protection (87L)
Backup ProtectionDirectional Overcurrent (67), Distance (optional), Earth Fault (51N)
Communication LinkFiber optic (via converter), Pilot wire, or RS485 dedicated link
SynchronizationGPS or communication-based time synchronization for phase comparison
Tripping TimeInstantaneous (< 30ms for internal faults)
Analog Inputs3-phase current + 1 neutral current; 3-phase voltage
MonitoringCT supervision, communication channel monitoring
InterfaceGraphic LCD with localized menus and status LEDs
Operating Temp-20°C to +70°C

3. Related Models

The SYMAP® LD is often used in pair with other units or specific communication modules:

SYMAP® LD-Standard: For standard cable protection in industrial loops.

SYMAP® LD-FO: Equipped with integrated fiber optic interfaces for long-distance line protection.

SYMAP® LD-G: A hybrid version that combines line differential with generator or feeder backup functions for specific shipboard topologies.

4. Application Cases

Marine Ring Main Systems: Protecting the vital cable links between the fore and aft switchboards on large vessels or cruise ships.

Offshore Power Links: Protecting the subsea cables connecting offshore platforms or wind turbines to a central hub.

Industrial Microgrids: Ensuring selective protection in closed-loop or “mesh” networks where standard overcurrent relays cannot achieve proper coordination.

Data Centers: Protecting the high-reliability feeders between different power modules to ensure zero-downtime fault isolation.

5. Product Advantages and Features

Absolute Selectivity: Only trips if the fault is located within the protected cable segment, preventing unnecessary blackouts in other parts of the system.

High-Speed Fault Clearing: Since it does not rely on time-grading (waiting for downstream relays), it clears faults much faster than standard overcurrent relays.

Bi-directional Protection: Ideal for networks with multiple power sources where fault current can flow in either direction.

Channel Supervision: Constantly monitors the communication link between the two relay ends; if the link fails, it automatically switches to a backup “Directional Overcurrent” mode.

3-CPU Security: Built on Stucke’s fail-safe hardware platform, ensuring that a single component failure does not disable the protection logic.

6. Other Models in the Same Series

The SYMAP® platform provides a unified HMI and software environment for the entire plant:

SYMAP® G / ECG: Generator and Engine management.

SYMAP® F: Feeder protection (time-graded).

SYMAP® T: Transformer protection (Differential 87T).

SYMAP® BC: Bus-tie Control for managing busbar couplers.

SYMAP® Y / M: Motor and Pump protection.2