Response Plan for System Operators
The following response plan will aid power system operators in preparing for and mitigating impacts from ashfall hazards:
- Secure the health and safety of staff. Goggles and masks are essential for protection, but so are safe operating procedures, as horizontal surfaces (e.g. roads and ladders) can become very slippery.
- System operators should maintain situation awareness by actively monitoring warnings and advice from local volcano observatories or relevant agencies to obtain the most up-to-date scientific alert levels, eruption warnings, ashfall maps and forecasts. Operators should establish and maintain these connections during non-crisis periods.
- Prepare a system for cleaning equipment before, during and after (e.g. for remobilised deposits) the event. This should include an estimate of the number of people and equipment required which can be predetermined by the magnitude of the ashfall. When problems arise (e.g. notification of leakage current or corona discharge), a rapid response can be made.
- Monitor the volcanological information from hazard scientists/agencies (e.g. ashfall forecasts, isopach maps, fall rates, etc.), the power dynamics of the system (e.g. voltage fluctuations, leakage current, etc.) and the conductivity of the ash (by ESDD analysis or via conductivity measurements). Based on these observations, make informed decisions on whether to continue supplying power to vulnerable sections of the system. Implement a mitigation strategy (e.g. controlled outage, on-line cleaning, etc.) if the benefits of maintaining power supply outweigh the financial consequences of de-energising all or part of the system.
Live Line Cleaning
For live-line cleaning of station and line apparatus, an appropriate procedure is as follows: Refer to IEEE Standard 957 (2005) for further information on safe and effective live-line cleaning practices)
- All cleaning personnel should wear a facemask and eye protection in addition to any personal protection equipment required by the power company.
- Compressed air cleaning (with or without a nonabrasive component) can be used to remove initial large amounts (e.g. >3 mm or 0.12 in) of ash. If using compressed air alone, then a pressure of 210 kPa or less (â‰¤30 psi) should be applied to avoid a sandblasting effect on glazed ceramic surfaces such as insulators and bushings and other sensitive equipment. Care should also be taken to avoid blowing ash into other parts of the substation or onto lines that have already been cleaned.
- A set of insulated tools for wiping, brushing and washing ash from energised equipment should be devised (e.g. as outlined in IEEE Standard 957 (2005)). For example, hot-sticks (designed appropriately for the component's rated voltage) fitted with brush heads or rags (typically made of burlap) work well for 'hot-wiping' ash from substation equipment (e.g. insulators, bushings, switches, busbars, circuit breakers, etc.).
- Depending on how strongly the ash has adhered to equipment, low-, medium- or high-pressure (e.g. 1,400 to 7,000 kPa) water blasting should be used to thoroughly rinse away any residual ash. If the ash has become heavily cemented to insulators, then soft-media blasting may be an effective alternative.
- A routine and continuous cleaning programme should be maintained until the threat of airborne ash contamination is over (including that of remobilised ash deposits).
For de-energised cleaning, the following procedure has been adapted from that outlined in IEEE Standard 957 (2005):
- All substation equipment must be de-energised and earthed prior to cleaning.
- All cleaning personnel should be required to wear a facemask and eye protection in addition to any personal protection equipment required by the power company.
- Depending on the state of the ash (e.g. wet or dry), transformer bushings and radiator fins should be cleaned by hand using soft rags followed by high-pressure washing
- Insulators, bus bars, circuit breakers, metering transformers and other critical apparatus should be cleaned by hand in a similar procedure as that used for transformers. Extra care should be taken to ensure that all surfaces are cleaned, including the undersides of insulator sheds. Additional materials, such as wet or paraffin-soaked cloths, steel brushes or steel wool, may be needed for insulators with strongly adhered ash deposits.
- If ash deposits are strongly cemented to ceramic surfaces (insulators and bushings), then a mild (and inert) solvent or detergent (e.g. OMYA brand products) can be applied and wiped clean using soft brushes, rags, paper towels or non-abrasive nylon pads. Steel wool can also be used when other cleaning tools are ineffective; however, caution should be exercised to avoid abrading ceramic surfaces and all metal particles left by the steel wool should be removed. No solvents should be applied to polymer insulators unless advised by the manufacturer.
- CELEC EP noted that contacts on disconnect switches (electrodes) are especially difficult to clean and may require scrubbing with a rough sponge or nylon pad to remove the contact grease in which ash becomes embedded.
- The substation/lines can be re-energised once all substation equipment has been dried using soft rags.