It is essential that the maintenance staff is qualified for electrical works and follows safety procedures.

Transcription

1 MAINTENANCE OF POWER FACTOR CORRECTION EQUIPMENTS Procedures, suggestions and traceability The purpose of this document is to propose a maintenance method that allows to identify the elements to be maintained in Power Factor Correction equipments. The shortage or even the lack of appropriate maintenance can lead to equipment faults, injures to people, animals or objects, for which the constructor can not be considered responsible. due to the flammable materials which capacitors are made of, Power Factor Correction equipments are be considered as fire hazardous devices in case of malfunctions or faults. Therefore it is fundamental to follow guidelines written in the standard CEI and the constructor directives defined in the installation and user manual. Power Factor Correction equipments have variable working conditions depending where they are installed:. Harmonics, moisture, temperature, time and operating conditions affect the natural and inevitable decline of the capacitors, therefore it s not possible to calculate Mean Time Between Failures (MTBF) to plan predictive maintenance of all the elements. Preventive maintenance has to be planned and registered to plot the trend of measured electrical quantities over time.(as suggested by CEI standard for electric substations maintenance). At the bottom of this document you can find a facsimile which could be useful 1. Pre-installation controls During installation it is necessary to verify the tightening of the screws of all the power connections, because transport could cause loosening. Furthermore it is necessary to inspect the total integrity of the equipment and of all the elements inside to make sure that no damage has occurred to the equipment during transport. 2. Maintenance safety measures It is essential that the maintenance staff is qualified for electrical works and follows safety procedures. Before working inside Power Factor Correction equipment Wait at least 20 minutes after power disconnection, to allow components cooling and capacitors discharge. 3. Preventive or ordinary maintenance Lifetime, electrical and mechanical reliability of the equipment are closely related to proper maintenance. Predictive maintenance can t be applied, then we recommend to schedule the tests as in the table below. Frequency of maintenance works is suggested, but maintenance planning is at customer s choice. It s also specified that periodicity of such inspections it s referred to 8 working hours per day, for 5 days per week, in the operating class of 55 C, without harmonic distortion. In the table below there are three different type of maintenance, that have to be followed with different frequencies depending on the operating year of the equipment.

2 TYPE OF CHECK EXECUTION MODE TYPE A MAINTENANCE 1 Check tightening torque of all power connections 2 Verify the integrity of the protection devices (fuse, varistors of static PFC equipments, ) 3 Clean the air ducts, grids, of the cabinet. In IP equipments clean or replace filters. 4 Clean the cabinet, removing powders or foreign bodies, to avoid triggering of partial discharges. Clean particularly the elements that could cause insulation problems (busbars supporting insulator, contactors, top plate of the capacitors, etc.) 5 Make sure no condensation is present on the live parts of the equipment 6 Check the integrity of the insulation of the electrical cables and of the auxiliary circuits 1 Verify the correct operation of the regulator 2 Check the integrity of the capacitor s discharge resistors 3 Make sure that the overpressure device of each capacitor is not activated 4 Check the current of each bank on each phase TYPE B MAINTENANCE In manual mode switch on each bank and verify if its contactor is properly closing and opening. Return the regulator on Automatic mode and make sure that with connected inductive loads ( motors, transformers, discharge lamps, etc ) inductive LED switches on. Measure the current on each phase with a current clamp, recording the values and comparing them with the rated ones. In case of decreases bigger than 5% from rated value, you have to measure the capacitance of each capacitor and if necessary replace them all (to replace capacitors see paragraph 4.1). Otherwise, if measured current of one or more phases is higher than 1.4 times the rated value, it means that the current harmonics level (THDi) is too high for that type of Power Factor Correction equipment. We suggest to contact us for an instrumental inspection.

3 5 Make sure the ventilation system is working properly For this purpose you can use an hot air blower to heat the control thermostat (at 35 C they shall close and operate the fans for the air expulsion) and the alarm thermostats (at about 50 C they shall open, opening the auxiliary circuit, disconnecting the capacitor banks). 1 Verify the absence of smut on screws or near the exit terminals (power cables) of the contactors. Pay special attention to the contactors of the first and the second banks, because they are connected/disconnected more frequently than the others. 2 Verify the absence of oxidation and/or corrosion on each component, particularly of the copper busbars/cables and over the enclosure surfaces 3 Verify that there are no deformities in the insulation of power cables, caused by too high operating temperature, especially on the exit of inductances terminals and on the connections of the fuse holders. 4 Verify the conditions of the surfaces: coatings or other treatments. For static Power Factor correction equipments verify with the same procedure also the efficiency of fans under the heat sinks. TYPE C MAINTENANCE 3.1 First operating year More frequent inspections are suggested compared to the following years, to monitor the adjustment of the equipment during its first operating year. - After 3 months: TYPE A maintenance - After 6 months: TYPE A and TYPE B maintenance - After 9 months: TYPE A maintenance - After 12 months: TYPE A, TYPE B and TYPE C maintenance 3.2 From the second operating year After a first monitoring period of the equipment, from the second year it is recommended to perform maintenance works every 6 months. However, life expectancy of the equipments depends on operating conditions and it is up to the customer the decision to perform more frequent maintenance works in case of more intensive use. For example, in a very wet or polluted setting (powdery, saline, ), more cleaning are necessary, as well as particular temperature conditions or operating conditions of the capacitors at a voltage higher than the nominal one (included within 30%), even if restricted to short time intervals (minutes within 24 hours), leads to a decrease of capacitors life expectancy.

4 - Every 6 months: TYPE A, TYPE B and TYPE C maintenance If after the measure of the electrical absorption on each capacitor bank, measured currents are less than the rated values, it s recommended to perform this type of inspection more frequently than six months. 4. Replacing out of order components If a fault that needs maintenance work occurs, it s important to analyse the power factor correction equipment to ensure its restore and duration. About this, it s not sufficient to replace the faulty element, but it s necessary to verify the status of all the components related to the failure detected. Therefore especially with old equipments it could be necessary to replace all the components (capacitors, contactors etc.), or better replace the entire capacitor bank. Faulty elements (capacitors, fuses, contactors, ) must be replaced with elements of the same type of the original ones. 4.1 Replacing capacitors Before operate make sure that each capacitor is discharged, short-circuiting electrical terminals. If a capacitor out of order is found, it is strongly recommended to replace all the capacitors that belong to the same bank. When a capacitor is replaced also its discharge resistor must be replaced. It s recommended to verify also female Faston. If they are oxidized, or if insertion or disconnection is loose (that is tightening torque of the male Faston is too low), it is recommended to replace also female Faston connectors 6.3mm, better if they have a cog against accidental disconnection. 5. Dismantling and disposal The dismantling must be performed by qualified personnel. All capacitors are PCB free and contain castor oil. Capacitors, components and enclosures disposal must be managed in compliance with the European Directives, and / or in compliance with the local regulations. Comar Condensatori S.p.A. is not responsible for improper disposal, which remains in charge to the owner of the equipment. In the European Countries disposal must be done in compliance with the European Waste identification Code (EWC 2002).

5 Maintenance sheet for a PFC equipment in the 1st year of operation P. F. Correction equipment Identification Number KVAr -.. V check 1 Check of the tightening torque of all power connections Maintenance company External Name.. Internal Department.. Check of the integrity of the protection devices (fuse, varistors of static 2 P. F. correction equipments, ) 3 Cleaning of air ducts of the equipment 4 Cleaning of the cabinet, removing powders or foreign bodies 5 Check of absence of condensation on the live parts of the equipment Check of the integrity of the insulation of the electrical cables and of the 6 auxiliary circuits 7 Check of the correct operation of the regulator 8 Check of capacitor s discharge resistors 9 Check of the overpressure device of each capacitor 10 Check of the current of each bank on each phase Check of the proper operation of the ventilation system and for static P. F. correction equipments check of the efficiency of fans under the heat 11 sinks Check of absence of smut on screws or near the exit terminals of the 12 contactors 13 Check of absence of oxidation and/or corrosion on each component 14 Check of absence of deformities in the insulation of power cables 15 Check of the conditions of surfaces: coatings or other treatments After 3 months After 6 months Supervisor signature Notes In columns Result write OK if maintenance operation is positive, X if maintenance work is necessary. Write down the type of work in the specific column. Column Sign contains the sign of the person who does maintenance works. Column Date contains the execution date of the maintenance operation.

6 check 1 Check of the tightening torque of all power connections 2 Maintenance sheet for a PFC equipment in the 1st year of operation Check of the integrity of the protection devices (fuse, varistors of static P. F. correction equipments, ) 3 Cleaning of air ducts of the equipment 4 Cleaning of the cabinet, removing powders or foreign bodies 5 6 Check of absence of condensation on the live parts of the equipment Check of the integrity of the insulation of the electrical cables and of the auxiliary circuits 7 Check of the correct operation of the regulator 8 Check of capacitor s discharge resistors 9 Check of the overpressure device of each capacitor 10 Check of the current of each bank on each phase Check of the proper operation of the ventilation system and for static P. F. correction equipments check of the efficiency of fans under the heat sinks Check of absence of smut on screws or near the exit terminals of the contactors 13 Check of absence of oxidation and/or corrosion on each component 14 Check of absence of deformities in the insulation of power cables 15 Check of the conditions of surfaces: coatings or other treatments After 9 months After 12 months Supervisor signature Notes In columns Result write OK if maintenance operation is positive, X if maintenance work is necessary. Write down the type of work in the specific column. Column Sign contains the sign of the person who does maintenance works. Column Date contains the execution date of the maintenance operation.

7 Maintenance sheet for a PFC equipment from the 2nd year of operation P. F. Correction equipment - Identification Number KVAr -.. V Maintenance company External Name.. Internal Department.. Every 6 months check Result Sign Date operation Check of the tightening torque of all power connections Check of the integrity of the protection devices (fuse, varistors of static P. F. correction equipments, ) Cleaning of air ducts of the equipment Cleaning of the cabinet, removing powders or foreign bodies Check of absence of condensation on the live parts of the equipment 6 Check of the integrity of the insulation of the electrical cables and of the auxiliary circuits Check of the correct operation of the regulator 7 Check of capacitor s discharge resistors 8 Check of the overpressure device of each capacitor 9 Check of the current of each bank on each phase 10 Check of the proper operation of the ventilation system and for static P. F. correction 11 equipments check of the efficiency of fans under the heat sinks 12 Check of absence of smut on screws or near the exit terminals of the contactors Check of absence of oxidation and/or corrosion on each component 13 Check of absence of deformities in the insulation of power cables 14 Check of the conditions of surfaces: coatings or other treatments 15 Supervisor signature Notes In columns Result write OK if maintenance operation is positive, X if maintenance work is necessary. Write down the type of work in the specific column. Column Sign contains the sign of the person who does maintenance works. Column Date contains the execution date of the maintenance operation.