Rotor Ground Detection System | AT-8600

Ground Fault Detection for Synchronous Generators

AT-8600 rotor ground setection systemThe Rotor Ground Detection System Model AT-8600 provides continuous wireless detection of insulation faults on the field windings of brushless generators and motors, combining advanced ground fault measurement techniques with the latest innovations in digital telemetry.




  • Continuous online monitoring of faults while rotating or at standstill
  • Non-intrusive end of shaft mounting
  • Fixed ground alarm threshold of 10k ohm
  • Built-in self-diagnostics, malfunction alarm, and open-wire detection enhance operator confidence in proper functioning of system


  • Allows for scheduled maintenance when ground fault is detected
  • Continuous monitoring of rotor ground faults on generators and motors

Reducing Your Risk

The Rotor Ground Detection System Model AT-8600 provides reliable, continuous, wireless detection of insulation faults on the field windings of brushless generators and motors. Advanced ground fault measurement techniques combined with the latest innovations in digital telemetry detect field ground faults before a catastrophic failure occurs, reducing the risk of unscheduled outages and allowing predictive maintenance procedures to be performed. Undetected field ground faults can result in severe damage to rotor insulation and forgings. Such faults can lead to costly rotor repairs and prolonged forced outages. The Rotor Ground Detection System provides operators with a valuable tool for early detection of these faults. Maintenance can be performed at scheduled outages, allowing implementation of a back-up plan prior to shutdown.

The system connects to the field negative terminal and the shaft ground to measure the insulation resistance of the field winding. Unlike other ground detectors, the alarm threshold always represents a fixed level of fault severity and does not change with fault location or excitation voltage. LED diagnostic indicators and self-test capabilities enhance operator confidence in the proper functioning of the system. The Rotor Ground Detection System Model AT-8600 gives operators of generators or synchronous motors with brushless exciters peace of mind and the assurance that a ground fault is not causing hidden damage that could lead to an unexpected and costly long-term outage.

AT-8600 pickup coil rotor ground setection system

Pickup coil

AT-8600 mounted transmitter rotor ground detection system

Rotor-mounted transmitter

AT-8600 receiver rotor ground detection system

Receiver in NEMA 4 enclosure

Rotor Connections Field Negative Terminal
Rotor Earth/Ground
Field Voltage
     Measurement Range 0 to 750 VDC
     Maximum Transient without Damage 1500 V for 5 seconds
Receiver Output Indicators
     Alarms Ground Fault and optional System Malfunction, 2–Form C relay 6 A / 250 VAC contacts
     LEDs LED Indicators to aid in identifying a ground fault, malfunction, or self-diagnostic status
Power 100–200 VAC, 50/60 Hz, or 24 VDC
     Receiver Alarm Outputs
     Ground Detection Alarms when insulation resistance falls below 10k ohm (± 10%) User-adjustable alarm delay from 5 seconds to 22 seconds
     Malfunction Alarms when there is a loss of power, failure of receiver, loss of data, open wire detection
     Alarm Interfaces Form C relay 6 A / 250 VAC
Ambient Temperature -40 °F to 194 °F (-40 °C to 90 °C) at Transmitter Module/Pickup Assembly -40 °F to 140 °F (-40 °C to 60 °C) at Receiver Unit
Axial Travel ± 0.25 in (± 6.5 mm) from nominal operating position
Rotor Speed 0 to 3600 RPM nominal; 4320 RPM Max