Electrical performance, excitation, control and protection.

The electrical performance of a rotating electrical machine is mostly defined by the condition of the rotor and stator windings, and the operation of the excitation system, if applicable.

Protection trips.

The machine needs to be protected with alarms and trips for abnormal running conditions, both electrical and mechanical. Some of these protections can be reset and the machine restarted directly as the fault is located.

Examples of protections that, if they give an alarm or trip, may need further investigation:

• Diode fault protection

• High temperature in bearing

• High temperature in winding or in cooling air

• Overcurrent, current and voltage unbalance, bus bar voltage

• Vibration protection

Pt-100 resistance temperature detectors.

Pt-100 resistance temperature detectors are an essential part in the machine's condition

monitoring and protection system. They are used to measure temperatures in the windings,

bearings and in the cooling air. The Pt-100 detector uses a fine platinum filament for the

temperature measurement, which can be damaged e.g. by incorrect handling or excessive

vibration.

The following symptoms might suggest a problem in a Pt-100 detector:

• Infinite or zero resistance over the detector

• Disappearance of measurement signal during, or after start up

• A significantly different resistance value in a single detector.

If a Pt-100 failure is suspected the findings should always be confirmed from the connection

box, by measuring the resistance at the detector with its cables disconnected. The findings

should by registered. For the correct measuring current see the appropriate Pt-100 detector. For resistance values at different temperatures, see Table 8-1 Temperature values for Pt-100 elements [7].

Last modified: Wednesday, 12 October 2022, 6:42 PM