Here there are all necessary operations required by the law to reduce the risk of accident and avoid criminal liabilities
The maintenance of low-tension electric panels is not only a legal obligation, but it is also a good practice to be considered to avoid the risk of accident and therefore for the safety of people.
To keep under control all the operations for the maintenance can be very difficult, for they are many.
This month we try to understand which are the essential measures as per the guidelines of the Federazione Nazionale Imprese Elettrotecniche ed Elettroniche (ANIE).
Installation and commissioning
The placement of the electric panel must be considered first. The enclosures can be placed in a place accessible to the operating parts and to other parts, which can be maintained. Size and placement must be evaluated carefully for the design of cabinets and technical locals. Besides, spaces between electric panels and walls must allow reaching easily the exits.
When it is necessary to design very big electric panels, it is necessary to define the points of mechanical subdivision to get many transport sections. These sections must be joint before the fixing of the whole structure on the floor, which must be levelled and without irregularities.
After that, some checks to reduce the possible dangers during the transport must be carried out.
According to the Federazione ANIE, these are the operations to be carried out:
- general visual inspection (cleaning and damaging during the transport);
- check of the clamping of connections;
- check of the clamping of the protection circuit;
- check of the insulation resistance among phases and between phases and the mass;
- check the correct opening/closing of each switch;
- check of the mechanical and electrical interlocks;
- check of the functionality of extraction and insertion on extractable/removable switches;
- check of the connection of the auxiliary and measure circuits;
- check of the right start-up of possible electronic measuring instruments;
- check of the correct intervention of relays with test button (switch on “closed” position);
- check of the auxiliary signals;
- check of the opening coils and of the emergency stop;
- check of the operation cycles for motorized switches;
- check of the auxiliary circuits of the extractable switches on “selected” position;
- check of the switches regulation;
- check of voltmeters, lamps, analyzers;
- check of intervention of differentials by means of the test button;
- check of the correct starting of relay of electronic switches.
After these operations, it is necessary to proceed with the start-up, which foresees:
- closing of input line switches;
- check of the correct working of the measurement instruments, of lamps and of the net analyzers;
- single closing of the exit switches;
- check of the functioning of users (if possible).
CEI standards foresee the specific maintenance operations. The maintenance can be ordinary when it aims to avoid failures and damages to the electric panel.
A maintenance schedule should foresee these operations:
- check of the integrity of the panel;
- check of mechanical connections of the panel;
- visual inspection of the mechanical, thermal and electrical damages including the possible oxidation;
- check of the temperatures through the thermography;
- check of the identification label and availability of the electric diagram;
- check of the correspondence between equipment and electric diagram;
- check of the calibration of the protection devices as per loads detected;
- check of the measuring instruments efficiency;
- check of the integrity of fuses and of signaling lamps (auxiliary circuits in general);
- check of the mechanical working of the equipment;
- functional testing of differential protection devices;
- functional testing of MT/BT (if present);
- functional testing of safety circuits;
- check of the connection to the earth installation and of the protection conducers
- check of tightening torques of the bolted elements;
- check of the terminal board, clamping and connections;
- general cleaning of the panel and relative equipment.
At least, the extraordinary maintenance is carried out after a failure not foreseen or because of an intervention not included in the ordinary maintenance.
In this case, operations to be carried out are the following:
- securing of the electric panel through the opening of the general sectioning device and the following test of the opening of the circuit through instrumentation;
- detection of the cause of the failure and solution;
- cleaning of the blackened parts (if necessary);
- visual inspection of bars, devices, insulating parts, ect.
- check of the devices efficiency;
- replacement of devices, bars, cables or other damaged parts (if necessary);
- checking of the tightening torques of connections
- closing of the user service concerned to check the insulation resistance and of the dielectric rigidity.
Reset of the connection to the user service, power supply of circuits and check of the correct operation.