IEEE Std 1129 pdf free download
IEEE Std 1129 pdf free download.Online Monitoring of Large Synchronous Generators (10 MVA and Above).
4. Brief description of degradation mechanisms, online monitoring methods, and instrumentation
4.1 Stator frame
Typically, stator frames for machines within the scope of this standard are made of fabricated steel. There are significant structural ditierences in the design and construction of frames for cylindrical-rotor versus salient-pole generators. There are also major differences in the design and construction of frames for horizontal versus vertical machines. In the case of horizontal machines with cylindrical rotors, two major types of frames exist: one in which the core is permanently attached to the frame, called an integral frame, and another in which the core is constructed in a fabricated steel cage that itself is inserted into the frame. The cage supporting the core can be also considered part of the frame. Also, in many air-cooled machines the core is mainly supported-attached to the bedplate while the enclosure is designed primarily to contain and control the flow of air.
In all generators, the main purpose of the frame is to provide support to the core, as well as to anchor the machine, by transmitting stator tangential torques to the foundation. In most generators, the frame also includes an outer cover (the casing) to contain the cooling air or hydrogen. Air or hydrogen coolers are inserted inside or supported above, below, or at the sides of the frame. Some air-cooled machines do not have heat-exchangers.
4.1.1 Frame vibrations
Pro hkn Description: There are number of problems that can develop with the frame, such as cracks, distortion, loose footing, and excessive vibration. Frame issues are normally detected during periodic maintenance inspections. In most cases, the frame is the less problematic component of a large generator, thus monitoring is unusual. In those cases where monitoring is applied, the parameter tracked is vibration. Vibration of the frame can be the result of a problem intrinsic to the frame (such as cracks, distortion, or loose footing), but in most cases it is due to other component problems.
InslrumenWi,on: Frame vibration is tracked with the help of vibration probes mounted on the frame inside or outside the casing in one location or several locations. Triaxial probes may be used but are not necessarily required for this application.
4.1.2 Presence of liquids
Problem Description: Free liquids (water and/or oil) inside the casing or in the winding itself are the result of undesirable leaks from coolers, bearings or hydrogen seals, and from inner-cooled coils (by oil or water). These free liquids have the potential to challenge the integrity of the insulation of the core laminations and the coils and create corrosion on metal components, loosen stator wedges and coil packing (by oil), and block the flow of cooling gas (by oil and/or water). Loss of liquids can also cause loss of lubrication, cooling, and the failure of hydrogen seals. Furthermore, in machines with open enclosures oil can combine with dust from the surrounding environment and clog cooling air passages.
Instrumentation: One of the methods for monitoring for the presence of free liquids in the machine is by collecting them at the bottom of the casing and removing them from the machine via drain lines. These drain lines may be fitted with sight glasses andlor detector circuits generating alarms in the presence of liquids. The sight glass can be considered a monitoring function as defined in Clause 3.IEEE Std 1129 pdf download.
