EN IEC 60034-3:2020 pdf download.Rotating electrical machines
4.10 Insulation against shaft current
Suitable precautions shall be taken to prevent harmful flow of shaft current and to earth the rotor shaft adequately. A turbine-generator shaft shall be earthed at a shaft position close to the reference end of the generator. Shaft voltage spikes caused by static excitation with controlled rectifiers shall be kept down by suitable means to non-critical values. These spikes can cause damage, for example to the bearing Babbitt, by breaking through the bearing oil film.Requirements for bearing insulation resistance to be measured during operation of the generator or compensator shall be agreed upon at the time of purchase.
4.11 Overspeed test
Rotors, i.e. main shaft and if applicable slip ring shaft or exciter shaft, shall each be tested completely assembled at 1,2 times rated speed for 2 min.
If rotor fan blades are not assembled to avoid larger windage loss at overspeed test, this can be acceptable when the mechanical strength is assured by traceability of the material which would be proven by mill test report and non-destructive test report for design requirements.
The purpose of the rotor over-speed test is verifying the mechanical integrity of the rotor. This test is not intended to indicate the in-service operating capability of the machine. The in-service over-speed withstand capability of the generator/compensator and the frequency with which such an over-speed may be applied depends upon the design of the generator or compensator.
It is necessary to consider carefully any in-service over-speed conditions which could result from sudden disconnection of full load for example. Any particular requirements shall be agreed upon.
4.12 Critical speeds
Critical speeds shall not cause unsatisfactory operation of the combined generator-/turbine-shaft train within the peed-/frequency-range corresponding to IEC 60045-1 or agreed upon otherwise. This also applies to compensator rotors.
If generator and turbine are purchased from different manufacturers, there shall be an agreement on which party is responsible for achieving the desired performance of the combined turbine/generator shaft line including exchange of turbine and generator shaft data.
4.13 P-Q capability diagram
For generators, the manufacturer shall supply a P-Q capability diagram indicating the limits of operation. The P-Q diagram shall be drawn for operation at rated conditions. A typical P-Q diagram is shown in Figure 2; its boundaries are set by the following limitations:
●curve A represents operation with constant rated field current and therefore with approximately constant temperature rise of the field winding;
●curve B represents constant rated stator current and consequently approximately constant temperature rise of the stator winding;
●curve C represents limits due to the temperatures of the core end parts. In many cases this line is also shown as constrained by stability considerations, determination of which requires knowledge of the power system to which the machine will be connected. Such power system data is frequently unavailable or insufficient when a‘ synchronous machine only P-Q diagram" is created. Hence, it is common for line C on the P-Q diagram, for a machine alone,to be drawn showing any absolute limits required to protect core end parts and showing further stability factor constraints for ilustration purposes only.
●Additional diagrams may be provided for operation at agreed conditions, for instance at reduced cooling or, where applicable, at hydrogen pressures other than rated.EN IEC 60034-3 pdf download.