EN IEC 60034-3:2020 pdf free.Rotating electrical machines – Part 3: Specific requirements for synchronous generators driven by steam turbines or combustion gas turbines and for synchronous compensators (IEC 60034-3:2020).
Rotors,i.e. main shaft and if applicable slip ring shaft or exciter shaft, shall each be testedcompletely assembled at 1,2 times rated speed for 2 min.
lf rotor fan blades are not assembled to avoid larger windage loss at overspeed test, this canbe acceptable when the mechanical strength is assured by traceability of the material whichwould 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. Thistest is not intended to indicate the in-service operating capability of the machine.The in-serviceover-speed withstand capability of the generatorlcompensator and the frequency with whichsuch an over-speed may be applied depends upon the design of the generator or compensator.lt is necessary to consider carefully any in-service over-speed conditions which could resultfrom sudden disconnection of full load for example.Any particular requirements shall be agreedupon.
Critical speeds shall not cause unsatisfactory operation of the combined generator-/turbine-shaft train within the speed-/frequency-range corresponding to lEC 60045-1 or agreed uponotherwise.This also applies to compensator rotors.
lf generator and turbine are purchased from different manufacturers,there shall be anagreement on which party is responsible for achieving the desired performance of the combinedturbine/generator shaft line including exchange of turbine and generator shaft data.lf harmonics of the fundamental frequency with significant levels are present in the stator phase currents,additional currents will be induced in the damper circuit, for example on the rotorsurface, in the rotor damper winding, rotor wedges and retaining rings.The determination of withstanding unbalanced load has to take these effects into account.
The generator or compensator shall be designed to withstand a short circuit of any kind at its terminals “without failure”, while operating at rated load and 1,05 p.u. rated voltage, assuming the maximum phase current is limited by external means to a value which does not exceed the maximum phase current obtained from a sudden three-phase short circuit. “Without failure”means that the machine shall not suffer damage that causes it to trip out of service,though some deformation of the stator winding or loosening of end winding blockings might occur.
lf it is agreed that a sudden short circuit test shall be made on a new machine, it shall be doneas follows:
On agreement, a full dielectric acceptance test shall precede the short circuit test.
A generator or compensator that is to be connected directly to the grid shall have a three-phases hort circuit applied at its terminals when excited to rated voltage on no-load.
A generator or compensator intended for connection to the grid through a transformer shall betested with a reduced voltage at the terminals. The test voltage shall be agreed on andpreferably chosen so that the same stator current is produced as would result in service from athree-phase sudden short circuit applied at the high voltage terminals of the transformer.
This test shall be considered successful if the generator or compensator is subsequently judgedto be fit for service without repairs or with only “minor repairs” to its stator windings,and if itwithstands a high-voltage test of 80 % of the value specified in lEC 60034-1 for a new machine.The term “minor repairs” implies some attention to deformation or loosening of stator windingsor end-winding bracing structures as well as to applied insulation,but does not implyreplacement of coils.
Abnormal high currents and torques can occur as a result of a short circuit close to the generatoror compensator in service,or of clearance and re-closure of a more distant fault, or of faulty synchronizing. lf such conditions imposed severe overcurrents,the machine should be examined thoroughly, with particular attention to the stator windings.Any loosening of supportsor packings should be made good before returning the generator or compensator to service, in order to avoid consequential damage caused by vibration.Checks for possible shaft balance changes and deformation of the coupling bolts and couplings are also recommended.EN IEC 60034-3 pdf download.