Extending Substation Lifespan Through Testing and Monitoring
Substations, although simple in design and operation, still require monitoring and testing to ensure that they are operating at peak efficiency, with the best return for investment. Wherever the substation is located, and whatever its function, it is exposed to extremes of weather and to a range of other stresses, all of which can cause a fault or failure over time.
At its heart, the transformer is a stable and key component, with a lifespan of around 20 years, which is protected by a range of switching, protection, and control equipment. But without a proper testing and maintenance routine, the transformer and its associated equipment can become inefficient, or faulty, or develop a catastrophic failure.
When a substation fails, or develops a fault, as it is a key component of any power distribution system, it can lead to a system or cascade failure across the entire network. Either way, it will be very expensive.
As a lot of electrical generation and distribution infrastructure is aging, it is becoming even more critical to maintain these networks in peak condition, to avoid the risk of blackouts and brownouts. However, due to economic circumstances, a lot of utility providers are moving their maintenance from a time-based schedule to a more cost effective, in the short-term, condition-based schedule. This ‘run-to-failure’ methodology has short-term benefits to the balance sheet, but over time, if failure occurs at a critical moment, it can be exorbitantly expensive. If the failure leads to a cascade or even a substantial blackout, third party claims and costs can become prohibitive to a business.
A lot of electrical substations are exposed to the vagaries of weather. Lightning and high wind can create the right situation for flashover arcing. These arcs can send power surges through substation equipment, causing malfunctions to occur. Ice and snow storms have the ability to down power transmission lines on either side of a substation, and could potentially damage smaller elevated transformers. Underground substations, have the potential to be flooded, with every severe storm or hurricane.
The extremes of temperature, and the effects of wet conditions can have a detrimental and corrosive effect on metal structures. Substation switch, protection and control gear, also undergo a range of other stresses. The high electrical voltages and currents, can produce electrical and thermal stresses within the equipment and linking infrastructure, possibly leading to materials failure. As substations use some moving parts, especially within the switching and protection circuits, there is also some mechanical wear and tear which can prove to be a stressor to the integrity of the substation.
Without regular monitoring and maintenance, substations can develop failure situations quite unexpectedly. However, through a regime of testing and monitoring, a lot of these scenarios can be minimised or avoided.
A range of equipment can and should be tested within a substation environment to ensure the continual well-being of the facility. Electrical items such as batteries and circuit breakers should be tested for faults and reliability of service. Earth grounding and resistivity tests should be carried out to ensure the safety of the structure. The detecting and testing of high voltage equipment should be carried out to ensure that equipment is reporting and recording accurately. To minimise energy loss as heat, and to protect the structure from long-term damage, low resistance testing should be implemented. Although transformers have no moving parts, their oil is subject to contamination and breakdown over time, and should be tested periodically. Partial discharge, and protection relay testing should be carried out to maintain the electrical integrity of the substation infrastructure.
The implementation of a SCADA system is extremely useful in the monitoring of real-time data from the substation. Through the use of supervisory control and data acquisition software and hardware, it is possible to monitor any system or structure and provide control adjustments as necessary, through human-machine interface software. The use of SCADA software, connected by wireless and Ethernet connections to the internet, allow data-driven decisions to made by a central control room. By setting acceptable parameters, for various procedures and equipment, alerts can be sent to a control room or even connected personnel, if there are situations which may need immediate attention. This real-time intervention can lead to a greater longevity of the substation infrastructure.