SAFETY P R A C TIC E S - gnssn - International Atomic Energy Agency

This publication is no longer validPlease see http://www-ns.iaea.org/standards/Assessment questions(1) Are the AC and DC switchgear and motor controls:(a) Qualified to fulfil their performance requirements under their specifieddesign basis conditions?(b) Selected and sized adequately to accommodate all loading conditionswhich may be applied within their ratings?(c) Rated to withstand and interrupt (where necessary) the maximum shortcircuit currents to which they may be subjected?(2) Is the control power adequate to accommodate the switching of all circuitbreakers and contactors as required under all conditions?(3) Are there measures to monitor the status of the switchgear and motor controlsfor abnormal deviations of parameters, e.g. bus voltage, control voltage, airpressure and switch positions?(4) Are there adequate means to indicate the mechanical position of plug-inbreakers? Are alarms provided in the control room warning of deviations fromnormal conditions?(5) Are there adequate measures to protect the switchgear or load against overcurrentand short circuit? This question deals with problems of selectivity. Theassessor has to take into consideration that the set points of all protectivedevices will comply with the selectivity requirements.(6) Are the components qualified, is documentation available and does thedocumentation substantiate the qualification?(7) For ungrounded systems (AC or DC), are ground detectors provided to monitorfor deviation of insulation resistance to ground and inadvertent groundingof a circuit?(8) Where ‘isolating’ diodes are used to permit multiple feeding of a DC bus orload, what provisions are made to detect failure of the diodes to conduct orisolate?3.4.4. TransformersThe assessor should ensure that the transformers will meet the operationalrequirements, taking into account the worst load condition determined by the loadstudies in Section 3.1.1.Basis for acceptanceSafety Guide 50-SG-D7.Assessment questions(1) Will the transformer power rating be in accordance with the intended anddesigned power distribution?31