“If failures can be predicted before they occur, action can be taken to reduce the occurrence of unplanned outages of equipment thus contributing to meeting reliability performance targets and reducing the cost of interruptions.”
Kehinde O. Awodele, an electrical engineer lecturing at the University of Cape Town, addresses some common health and safety related challenges faced by employees when conducting condition monitoring of critical power assets.
In this article the health and safety challenges associated with monitoring the conditions of these power assets are considered. To effectively identify the health and safety challenges in any job, apart from the need for standard work procedures (SWP) to be established for different jobs, job safety analysis (JSA) needs to be carried out to determine the hazards in each of the tasks in a job.
In the table below, some of the analysis carried out to monitor the condition of transformers (which are part of the most critical assets) and switchgear, related hazards, possible breakdown events and possible personnel safety outcomes are listed.
Transformers / Switchgear condition monitoring safety challenges
|Task||Hazard||Possible Breakdown event||Possible Outcome|
|1||Dissolved gas analysis to monitor the condition of transformer oil||Large quantities of combustible gases in transformer fluid and the headspace above the fluid||Fire and explosion||Burn|
|2||Oil analysis (to monitor the condition of the Oil Insulation)||Oil under pressure from head of oil, leaking bottles and hoses, contact with insulating oil||Spillage, failure to tighten fittings correctly, failure to inspect all hoses and fittings||Asphyxiation, skin irritation, frost bite, environmental harm|
|3||Partial discharge analysis||High voltage||Accidental touching of leads||Electric Shock|
|4||Power transformer winding DC Resistance measurement (to ensure that no loose connections, discontinuities, or problems exist between the tank/connections and the internal portion of the transformer)||Winding-resistance measurements may require 1A to 100A DC for accurate measurements. When the bank has been charged up with a DC current, the collapse of the flux, discharges considerable electromagnetic energy stored in the winding. Possibility of hazardous voltages.||Leads removed from winding before discharge, high voltage spike from collapsing magnetic field
|5||Power Transformer No load loss test (to monitor the condition of the core)||High Voltage from CT secondaries
Floating VT voltages
Applied Test Voltages
|Open Circuited CT secondary windings, unearthed VT windings
|6||Completion and Clean up||Undischarged or energized test equipment
|Failure to isolate, discharge and earth all test equipment||Electric Shock|
Interruption of supply to customers results in huge financial losses to the customers as well as the utilities and should therefore be minimised as much as possible. Failure of power system equipment is responsible for a large portion of power system outages and associated interruption of electricity supply to customers.
Capital investment and adequate maintenance is necessary for a given level of reliability. Incentive (performance)-based regulation of electric utilities has led to a drive for economic efficiency, which leads to less frequent maintenance of utility equipment in order to cut cost.
If failures can be predicted before they occur, action can be taken to reduce the occurrence of unplanned outages of equipment thus contributing to meeting reliability performance targets and reducing the cost of interruptions.
To this end, condition monitoring of critical power system components such as transformers, circuit breakers, cables and power lines is essential. Some of the monitoring is carried out by inspection while for other tests/analysis is carried out by analysis offline or online.
The selection and use of proper protective equipment (PPE) can grossly reduce the risks of arc-flashes and other electrical hazards to those working on live (energised) equipment.
Kehinde Awodele is an electrical engineer with MSc (Eng) Electrical Power and Machines. She worked in the electricity meter manufacturing industry for several years. She is currently lecturing in the Department of Electrical Engineering, University of Cape Town, South Africa.