Description

GE Multilin SR750-P5-G5-S5-HI-A20-G-E

I. Overview

The GE Multilin SR750-P5-G5-S5-HI-A20-G-E is an integrated protection relay specifically designed for critical power equipment such as generators, transformers, busbars, and transmission lines. It integrates protection, monitoring, control, and communication functions in one unit, serving as a core safeguard for the safe operation of power systems. This device can real-time collect core operating parameters of equipment, including current, voltage, and power. It judges the equipment's operating status through built-in precise protection algorithms. When faults such as short circuits, overloads, ground faults, overvoltages, and undervoltages occur, it can trigger protection actions within milliseconds to cut off the faulty circuit. Meanwhile, it records fault information and uploads it to the monitoring system, providing comprehensive support for equipment fault traceability and operation and maintenance optimization.

With its modular configuration, strong anti-interference capability, and wide scenario adaptability, this device is widely used in fields such as power systems, petrochemicals, metallurgical smelting, and industrial manufacturing. It can not only adapt to the excitation fault protection of generators but also meet the overexcitation and differential protection needs of transformers. It is a key component for achieving precise equipment protection and efficient management in complex power networks.

II. Technical Parameters

III. Functional Features

1. Protection Function Library for Multi-Equipment Adaptation: It has built-in dedicated protection modules for generators, transformers, busbars, and lines, covering more than 20 protection functions such as short circuit (instantaneous/short delay/long delay), overload (inverse time/definite time), ground fault (zero-sequence current/residual current), overvoltage, undervoltage, overexcitation, differential protection, loss of excitation protection, and reverse power protection. It supports configuring protection logic through software. For example, loss of excitation and reverse power protection can be enabled for generators, and overexcitation and differential protection can be enhanced for transformers. It can adapt to the protection needs of different equipment without replacing hardware.
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3. High-Precision Multi-Dimensional Monitoring and Data Recording: Equipped with a 24-bit high-precision AD conversion chip and a high-speed data processing unit, it real-time collects 18 operating parameters including three-phase current, three-phase voltage, active power, reactive power, power factor, electrical energy, and harmonic content (2nd to 21st order). The data update rate reaches 20 times per second, enabling accurate capture of parameter mutations at the moment of a fault. The built-in large-capacity data logger can store 500 event records (including fault type, occurrence time, and parameter data) and 20 fault waveform records (1 second before and after the fault), with an event timestamp accuracy of 1ms, providing a complete data chain for fault root cause analysis.
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5. Flexible Control and Interlocking Logic: It integrates programmable logic control (PLC) function, supporting custom interlocking logic through a graphical programming interface to realize control functions such as equipment start-stop, fault linkage, and standby equipment switching, without the need for additional independent PLC. For example, an interlocking logic can be programmed as "trigger an alarm when the transformer oil temperature is ≥100℃, and cut off the power supply after a 5-second delay and start the cooling system when the temperature is ≥110℃", improving the level of system automated operation and maintenance. It supports linkage with equipment such as excitation devices and speed governors to achieve coordinated protection and control of generators.
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7. Intelligent Communication and Remote Operation & Maintenance: It supports multiple mainstream industrial communication protocols and can be seamlessly connected to SCADA systems, DCS systems, or smart power platforms, enabling functions such as remote monitoring of operating parameters, remote configuration of protection settings, and remote push of fault information. Equipped with a web visualization interface, operation and maintenance personnel can view real-time data, download fault records, and perform parameter calibration through a browser without installing dedicated software. It supports online self-inspection of equipment status, allowing remote monitoring of the status of components such as relay contacts and communication links to achieve preventive maintenance.
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9. Strong Anti-Interference and High-Reliability Design: It adopts industrial-grade high-stability components and enhanced electromagnetic compatibility design, passes the IEC 61000-4 series EMC tests, and has anti-interference capabilities of ±15kV for electrostatic discharge and ±2kV for surge, enabling stable operation in high-interference environments such as metallurgical workshops and chemical plants. It has built-in hardware self-inspection and software fault-tolerance mechanisms, which real-time monitor key components such as power supply, AD conversion circuit, and relay output. If a fault is detected, it immediately issues an alarm and records it, while ensuring that core protection functions are not affected. The Mean Time Between Failures (MTBF) is ≥300,000 hours.

IV. Working Principle

1. Signal Collection and Preprocessing: On-site current transformers (CT) and voltage transformers (VT) collect the three-phase current and voltage signals of the equipment. These signals are subjected to overcurrent, overvoltage protection, and filtering processing through the isolation and conditioning circuit (2500V AC optoelectronic isolation) inside the module to filter out high-frequency interference. At the same time, auxiliary sensor signals such as temperature and speed are connected through dedicated interfaces and preprocessed to ensure that the input signals meet the requirements of AD conversion.
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3. Analog-to-Digital Conversion and Data Calculation: The preprocessed analog signals enter the 24-bit high-precision AD conversion chip, which converts them into digital signals and transmits them to the main microprocessor. The microprocessor calls dedicated algorithms to calculate parameters such as active power, reactive power, and harmonic content, stores the real-time data in the database, and updates the panel LCD display and communication buffer simultaneously to ensure real-time data synchronization.
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5. Protection Logic Judgment and Action Execution: The microprocessor real-time compares the calculated parameters with preset protection settings (such as short-circuit current threshold, overvoltage threshold) and custom logic. When it detects that parameters exceed the standard (e.g., current reaches the short-circuit threshold) or logic conditions are met (e.g., oil temperature exceeds the limit), it immediately triggers a protection action: drives the trip relay to cut off the equipment power circuit, and triggers the alarm relay to issue an audible and visual alarm at the same time. If triggered by control logic (such as interlocked start of standby equipment), it drives the corresponding control relay to execute the preset operation.
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7. Information Recording and Communication Upload: When an action occurs, the microprocessor synchronously records the event type, occurrence time, parameters before and after the action, and fault waveform, and stores them in non-volatile memory (data is not lost when power is off). At the same time, it uploads real-time data, fault information, and equipment status to the upper-level monitoring system through the communication interface according to the preset protocol. If it receives a control command from the upper-level system (such as remote modification of settings), it executes the command after verification and feeds back the execution result.
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9. Self-Inspection and Fault-Tolerance Guarantee: The main microprocessor continuously runs a self-inspection program, regularly calibrates the AD conversion accuracy, and detects the status of relay contacts and the connectivity of communication links. If AD conversion drift is found, it automatically starts the calibration process; if a relay fault is detected, it switches to the standby circuit (optional); if communication is interrupted, it maintains the normal operation of local protection functions and records the fault, ensuring that equipment protection is not affected by communication faults.
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V. Common Faults and Solutions