Historically, substation assets have been loaded beyond nameplate ratings and the need to accommodate these emergency, or contingency, conditions are best served using End-to-End electrical apparatus monitoring systems.
For many years the limit for normal apparatus loading was based on the maximum nameplate rating or an arbitrarily set value, called ‘the red line’.
On-line monitoring of power transformers and circuit breakers for condition assessment has gained popularity over the past twenty-five years, the typical technology adoption period, from concept to commercial reality in the electric utility industry.
What are the benefits of implementing End-to-End monitoring of power transformers and circuit breakers?
• Provides Situational Awareness of electrical assets operating closer to their capacity without compromising safety or reliability.
• Fully optimize real-time substation loading/overloading based on actual site conditions, including asset condition or operating modes. • Assist in making intelligent decisions about load management based on actual circumstances. • Forecast (predict) operating conditions used to facilitate condition-based maintenance (CBM) programs or agency reporting (such as environmental reporting of SF6 release). • Collect operational and accumulated loss of life data to enable estimation of the residual.
The benefits of on-line monitoring have primarily accrued to reduce maintenance costs and overall improvement in T&D system reliability. The prospect of using on-line monitoring to make intelligent decisions on how to optimize the load on such important substation assets follows the adoption of load management technology for power equipment such as oil-filled transformers and oil or gas-filled circuit breakers.
The use of on-line monitoring systems as controlling devices, such as the cooling system on transformers providing communications with external networks, enables the system to be integrated in the transformer control system resulting in minimal incremental cost to implement. The additional information gathered on the asset greatly offsets this cost.
The size or criticality of the unit is no longer the deciding factor for on-line monitoring as the cost of deployment is minimal and the tangible benefits related to monitoring far out-weigh the cost.
Clearly, sustaining electrical apparatus operation and uptime, reliable operations and increased asset life are the benefits of continuous monitoring systems.
Technology solutions are essential for communications to connect devices installed on field assets to communicate to networks via substation control rooms. One suitable technology is the powerline communications system (iBridge), which provides high- speed, encrypted communications over existing cables. The iBridge system is substation hardened, designed to perform in high EMC environments, available as point- to-point or point-to-multipoint, protocol independent with rapid installation time and suitable for existing or new substation installations.
The cost of deploying such systems is non-recurrent, totally flexible and extremely competitive with fibre or wireless systems. The encryption level ensures full security of data.
On-line monitoring of power transformers and circuit breakers in a substation, with communications to SCADA and engineering networks, is mature technology suited for new installations as well as retro-fitting to existing assets. The future is here and available for all asset classes, with the objectives of understanding Situational Awareness of the equipment and its ‘reliability, whilst minimizing operational expenditure.
By: Brian Sparling, SMIEEE Dynamic Ratings, Senior Technical Advisor
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