FAQ's
Frequently Asked Questions about High Voltage Insulator Coating (HVIC)
How does HVIC restrict the rise in leakage currents and protect the insulators against pollution induced flashovers if it does not bury the pollutants?
The cured HVIC coating has a high angle of hydrophobicity. This hydrophobic capability is of prime importance because it is this factor that controls the degree of wetting of the contaminants and thereby the amount of surface leakage current increase. Moisture on the insulator surface will form in droplets and by so doing will prevent the surface pollution from becoming wet and producing a conductive layer of ionisable materials that lead to increased leakage, dry band arcing and eventual flashovers.
For how long will a single coating of HVIC provide protection?
The actual life expectancy of HVIC is mainly dependant on the insulator design as well as the type of contaminate and the rate of fall out on the insulator surface, however experience shows us that a single application will provide excellent protection for periods well in excess of 20 years (Track Records indicate 20+ years).
How is the coating applied to the insulators?
The application of HVIC is very critical to the function of the coating itself. For this reason the application should only ever be carried out by experienced personnel who have been specifically trained and certified. All of Indigo Power applicators are specialists in HVIC application.
Can we use a contractor to apply HVIC?
Yes, but we would highly recommend that you contact us for a Turnkey solution or for a reputable and approved applicator. Only in this way can you ensure that the optimum performance and long life of the coating system is achieved. A reputable applicator will be able to demonstrate several years experience (3 minimum) with HVIC. An additional concern should be a warranty for the application as well as the material warranty. Indigo supply a warranty covering both material supply AND application.
What happens if HVIC is applied to a dirty surface?
Two things. Firstly, you don't get good adhesion, shortening the life of the product. Secondly, you don't want to put HVIC over conductive contaminates. This conductive surface could lead to interfacial tracking underneath the Coating.
Can HVIC be applied to a wet surface?
No, the surface should be dry for best adhesion.
What time is required before applying second and subsequent coats?
Subsequent coats as necessary to achieve minimum 380 microns DFT can be applied at 15 - 20 minute intervals.
When can the system be re-energised after coating?
Because the electrical properties are nearly the same for uncured as for cured material, the system can be energised immediately after coating is complete. Full cure will take around 8 hours.
To what thickness should it be applied?
To get the best optimum life, it is recommended that HVIC be applied to a minimum dry film thickness of 380 microns (15 mils) and to achieve this, the wet film thickness should be approximately 510 microns (20 mils). Indigo Power will generally apply a nominal film thickness of 400 microns (0.4 mm).
How can thickness be checked?
Precise measurement can be very difficult during coating application due to the method employed of building the total thickness in several layers. Please contact Indigo Power for guidance.
Does the underside of insulator sheds require 380 microns thickness?
It is not always possible to achieve a 380 microns dry film thickness under sheds, which have skirts. It is important to see that the "hard to get at" areas have at least one good coat of HVIC (such that the insulator base colour is not visible).
Do runs or drips cause problems?
No, but this should be avoided since it is a waste of material.
What maintenance is required to be done to the coating during service?
HVIC is designed to be essentially maintenance free. The coating will retain some dirt and discolouration on the surface but water repellence is fully maintained with encapsulation of the deposits by the low molecular silicone fluid, thereby maintaining the hydrophobicity of the coating.
Can HVIC be applied to energised insulators?
Yes ,although this should only be considered in extreme cases and carried out by highly trained applicators. Consult Indigo Power for full details.
Is HVIC effective against all types of contaminants?
HVIC works well with practically all types of contaminants. Some highly conductive industrial contaminates might require special attention, but flashovers caused by iron ore and graphite dust, for example, have been prevented by applying HVIC.
How can we determine if the coating HVIC is still in good condition?
Normally a visual inspection is good enough to see the condition of the coating. A simple hydrophobicity test (by a fine spray of water onto the coating) is a simple method of judging the HVIC condition. If the water beads up into small droplets it is an indication that the HVIC is fine. If the droplets are large, the coating may need a clean. More precise methods of judgement include measurement of the surface resistance.
What is the shelf life of HVIC?
HVIC has a shelf life, which is 12 months from date of manufacture which can be extended if the coating is maintained at a temperature of 23 deg.C or below.
Are there special storage requirements for HVIC?
HVIC should always be stored in accordance with the manufacturers instructions, generally this will be around 23 deg.C or below. Storage at elevated temperatures may deteriorate the coating and shorten the shelf life.
Can HVIC be applied to non-porcelain and non-glass insulators?
HVIC is designed to provide un-primed adherence to glass and porcelain insulators but it is possible to coat polymer insulators (e.g. EPDM), please consult Indigo Power for full details.
Will the HVI coating withstand wind blown particles such as sand?
Yes, because the coating is basically a rubber it can absorb the energy of a sandstorm. Tests have been carried out on a half coated insulator in a shot blast chamber, the results of which show the glaze was totally removed from the uncoated area of the insulator whereas the HVIC coating was unaffected.
Does the HVI coating need to be mixed before application?
No, because the coating is supplied ready to use. However as a precaution we recommend that the coating material be thoroughly agitated immediately prior to use.
How do I select an applicator?
As advised previously, Indigo Power would be pleased to offer a Turnkey solution for your HVIC requirements. However, as a basic rule the applicator should have had at least 3 years experience with HVIC application.