SEL-300G Generator Relay

Apply the SEL-300G for comprehensive protection and control of small, medium, and large generators.

Features and Benefits

Limit Equipment Damage

Apply complete phase and neutral protection together with 100-percent stator ground fault detection. Specify optional unit differential and thermal monitoring for important machines. Use out-of-step, loss-of-excitation, overexcitation, frequency, and directional power elements for detection of abnormal operating conditions. Accurately detect generator field grounds. Make settings and check connections with ACSELERATOR® QuickSet™ SEL-5030 Software. Specify the optional synchronism check function for supervision of paralleling operations.

Increase Generator Availability

Simplify fault and system disturbance analysis with oscillographic event reports and a Sequential Events Recorder (SER). Monitor real-time and accumulated off-nominal frequency, run-time hours, full-load hours, and other important quantities. Minimize separate metering devices by using voltage, current, power, power factor, and energy metering capabilities. Monitor up to 12 machine temperatures using the SEL-2600 Series RTD Modules.

Provide Secure Remote Control and Monitoring

Use Modbus®, ASCII communications, and SEL Fast SER capabilities for control, monitoring, and alarm purposes. Control relay operation and initiate or block automation sequences from remote or local control systems using serial port commands.

Making Electric Power Safer, More Reliable, and More Economical®

Functional Overview

The SEL-300G Relay integrates numerous protection and monitoring functions. A functional overview diagram illustrates these capabilities, including:

• 52: Circuit Breaker status
• 24: Volts-per-Hertz protection
• 25: Synchronism Check
• 27: Undervoltage protection
• 59: Overvoltage protection (Phase, Ground, Negative Sequence)
• 81: Frequency protection
• 87: Current Differential protection
• 64F: Field Ground protection
• 49: Thermal protection
• 32: Directional Power protection
• 78: Out-of-Step protection
• 40: Loss-of-Field protection
• 46: Negative Sequence Overcurrent protection
• 50/51G: Ground Overcurrent protection
• 21P/C: Phase Mho or Compensator Distance protection
• 51V/C: Voltage Restrained/Controlled Time-Overcurrent protection
• 60: Loss-of-Potential protection
• 50N: Neutral Overcurrent protection
• 51N: Neutral Time-Overcurrent protection
• 87N: Neutral Current Differential protection
• 59N: Neutral Overvoltage protection
• 64G: 100-Percent Stator Ground fault protection

Additional features include SELOGIC® Control Equations, Event Reports, Sequential Events Recorder (SER), Breaker Wear Monitor, Station Battery Monitor, Modbus®, ASCII, Fast SER, Binary, and Distributed Port Switch Communications, Remote and Local Control Switches, High-Accuracy Metering, Off-Frequency Operation Time Accumulators, and Field Ground Detection (optional functions marked with *).

Complete Generator Fault Protection

Limit equipment damage and speed repairs with high-speed protection for all types of phase and ground faults. Current and voltage elements, combined with optional differential protection, make the SEL-300G suitable for all generator sizes and configurations.

• Current and voltage elements protect large and small machines against damaging faults.
• Optional differential protection provides sensitive and fast protection for generators and unit transformers. Harmonic blocking provides security when transformers are in the generator differential zone.
• 100-percent stator ground fault protection uses fundamental and third-harmonic voltage signals.
• Continuously measure field-to-ground resistance using the SEL-2664 Field Ground Module. Accurately detect field ground faults whether the generator is operating, stopped, or de-energized.

A diagram illustrates the generator winding and element coverage areas for 100-percent stator ground fault protection, showing 'Dead-Band' zones for 64G1 (59N) and 64G2, with a grounding transformer at the 0% point.

Complete Generator Fault Protection (cont.)

Dual-element loss-of-field protection prevents rotor heating and system instability from abnormally low excitation.

A diagram illustrates apparent impedance (R vs. X) with operating zones (Zone 1, Zone 2) and characteristic lines (e.g., 40Z2P = Xd, 40Z1P = 1.0 pu), representing dual-element loss-of-field operating characteristics with a negative Zone 2 offset.

Event Analysis, Recording, and Alarming

Speed repair and troubleshooting to reduce costs and get units back online. Identify root cause for emergency and triggered shutdown of generators and prime movers using detailed event reports. Program recordings of voltage and current waveforms with internal relay and external monitor points for an accurate record of operations and events.

• Improve operation analysis with a timed record of the last 512 operations of 96 different internal and external events.
• Use the built-in SER to verify startup and shutdown sequencing, routine and emergency operations, and timing of alarms.

A table lists generator terminal events, including date, time, element, and state, such as 'FAULT_TRIP', 'FIELD_BKR OPENED', '64G1 Deasserted', '86_TRIP RESET', and 'INAV_ENR_SCHM ARMED'.

Receive instant alarm messages triggered by selectable relay events using SEL Fast SER messaging.

Use the ACSELERATOR QuickSet Software Event Viewer or the more advanced ACSELERATOR Analytic Assistant SEL-5601 Software to clearly view and understand system faults. Records can be up to 180 cycles long.

A waveform plot displays phase currents (IA, IB, IC) and their associated protection elements over cycles, illustrating a phase-to-phase fault captured by the SEL-300G, analyzed using ACSELERATOR Analytic Assistant.

The ACSELERATOR QuickSet HMI simplifies configuration and troubleshooting.

Simplified Setup and Troubleshooting

• Use ACSELERATOR QuickSet to customize your generator protection, set and edit relay configuration, settings, and logic.
• View the HMI screens in ACSELERATOR QuickSet to check wiring polarity and connections.

System Backup Protection

• Use phase mho or compensator distance elements for secure system protection with stable reach looking through a delta-wye transformer.
• Apply voltage-restrained or voltage-controlled overcurrent relaying for reliable system fault response.

Abnormal Operation Protection

• Use the SEL-300G to measure and store accumulated off-nominal frequency data for proactive maintenance operations.
• Protect against damage from inadvertent energization. The SEL-300G instruction manual provides complete SELogic® control equation settings to activate protection when the generator is offline.

A graph plots Frequency (Hz) against Time (minutes), defining operational zones: Continuous Operation, Restricted Operation, and Prohibited Operation. This feature helps prevent vibration or damage with flexible alarms for off-nominal frequency.

General Specifications

AC Voltage Input

• 80–208 V_LL nominal for four-wire wye voltage input
• 80–140 V_LL nominal for three-wire delta voltage input
• 300 V_LN continuous limit for three-phase, four-wire wye connection
• 300 V_LL continuous limit for three-phase, three-wire delta connection
• 365 Vac for 10 seconds
• 300 V continuous, V_N-N neutral voltage input
• 300 V continuous, V_S-NS synch voltage input
• Burden: 0.13 VA @ 67 V; 0.45 VA @ 120 V; 0.80 VA @ 300 V

Power Supply Ratings

• 125/250 V: 85–350 Vdc or 85–264 Vac
• 48/125 V: 38–200 Vdc or 85–140 Vac
• 24/48 V: 18–60 Vdc
• 25 W maximum for all supplies

AC Current Inputs

• 5 A nominal: 15 A continuous, 500 A for 1 second, linear to 100 A symmetrical, 1250 A for 1 cycle. Burden: 0.27 VA @ 5 A; 2.51 VA @ 15 A.
• 1 A nominal: 3 A continuous, 100 A for 1 second, linear to 20 A symmetrical, 250 A for 1 cycle. Burden: 0.13 VA @ 1 A; 1.31 VA @ 3 A.

Standard Control Input and Output Ranges

• 24, 48, 110, 125, or 250 Vdc
• Standard configuration provides 6 inputs and 8 outputs, <5 ms pickup, <8 ms typical dropout time, 30 A make, 6 A continuous duty.
• Additional interface I/O board may be selected with standard inputs and high-current interrupting outputs.

Operating Temperature

• -40° to +85°C (-40° to +185°F)
• (Note: LCD contrast impaired for temperatures below -20°C)

Conformal Coating

Make the world's most reliable relays even tougher. Add an extra level of protection to printed circuit boards with optional conformal coating.