Basler D4N3H1U Intertie Protection System – Comprehensive Generator Grid-Connection Protection

The Basler D4N3H1U is a digital protection relay specifically designed for intertie applications, where a generator or distributed generation (DG) system connects to a utility grid. Revision D brings enhanced processing speed and additional logic features. It monitors electrical parameters on both the generator and utility sides to detect abnormal conditions and trip the intertie breaker when necessary.

Protection Functions

• Anti-islanding detection (under/over frequency and voltage)

• Directional overcurrent (67) and directional power (32)

• Voltage vector shift or rate-of-change-of-frequency (ROCOF) for island detection

• Overvoltage (59) and undervoltage (27) with time delay

• Overfrequency (81O) and underfrequency (81U)

• Loss-of-mains (LOM) protection per IEC 62116

Advanced Features

• Programmable logic equations for custom tripping schemes

• Event recorder with 1000+ events and waveform capture

• Communication: Modbus, DNP3, IEC 61850 GOOSE

• Front-panel HMI with graphical display and keypad

• Multiple setting groups for different grid codes

Technical Specifications

• Voltage Inputs: 120 VAC or 400 VAC (selectable)

• Current Inputs: 1 A or 5 A CTs

• Auxiliary Supply: 24–250 VDC or 100–240 VAC

• Tripping accuracy: ±2% for frequency, ±1% for voltage

• Operating temperature: -25°C to +70°C

Installation and Wiring

The D4N3H1U is housed in a 4U high, 19-inch rack-mountable chassis. Rear terminals are provided for all inputs and outputs. The relay includes multiple binary inputs and trip relays, with self-supervision outputs.

Setting and Commissioning

Settings are entered via the front panel or through Basler's BESTCOMS software. The relay includes a test mode that allows simulation of all protection elements without actual tripping. Commissioning involves verifying phase angle between generator and grid, and testing each protection function with secondary injection.

Applications

This relay is essential for cogeneration plants, wind farms, solar PV inverters, and any distributed generator that must island upon grid loss. It complies with IEEE 1547 and UL 1741 for grid interconnection.

Maintenance

Self-diagnostics continuously monitor hardware health. Firmware updates are possible via communication port. Annual functional testing is recommended.

Conclusion

The Basler D4N3H1U Intertie Protection System provides the highest level of safety and reliability for grid-connected generators, ensuring seamless and compliant operation.