Dynamic Loading Effect on Fault Current and Arc Flash for a Coordinated Substation

Abstract

Due to load growth and various load types within the service territory, utilities need to enhance the utilization of substations. In any case, towards the coordinated substation design, the utilization of the transformers' most total capacity cannot be reduced just because there is a lack of proper coordination between transmission and distribution systems. The transmission and distribution systems' stability and safe operability must be investigated in a coordinated substation. The critical issues are the asymmetric fault currents on the high voltage and arc-related safety issues on the distribution switchgear at different dynamic loading scenarios. We found that when one 138 kV transmission line and two transformers are energized, with increased dynamic loading, from 40% and above, the substation, as a whole, gets gradually more stressed. Because of the highest amount of fault currents on the 138 kV bus, to avoid CT saturation, we need to consider that three transmission lines are connected, and all three transformers are running at 100% dynamic loading. At this value of dynamic loading, in the 13.2 kV switchgear, the incident energy is 2 cal/cm 2 , and the arc flash boundary is four feet, which ensures that all workers need to wear the proper arc-rated clothes to work on any de-energized cubicle of the switchgear.

Fault-Locator Scheme for Combined Taba-Aqaba Transmission System Based on New Faulted Segment Identification Method

“…Load increases lead to higher fault currents, while load decreases result in reduced fault currents. Considering dynamic loading's influence is critical in power system design, including protective scheme development, current transformer selection, and choosing protective devices, to ensure safe fault handling and prevent equipment damage [10]. The dynamic loading affects fault location techniques based on traveling waves.…”

“…The dynamic loading affects fault location techniques based on traveling waves. Fluctuations in transmission line impedance due to dynamic loading affect the reflection and transmission of fault-generated transient signals [10], making accurate fault location estimation challenging in the time domain. Additionally, dynamic loading causes variations in the line charging current [10], influenced by line capacitance and length, which can interfere with transient signal detection and interpretation, potentially complicating the fault location process.…”

“…Fluctuations in transmission line impedance due to dynamic loading affect the reflection and transmission of fault-generated transient signals [10], making accurate fault location estimation challenging in the time domain. Additionally, dynamic loading causes variations in the line charging current [10], influenced by line capacitance and length, which can interfere with transient signal detection and interpretation, potentially complicating the fault location process. On the other hand, the dynamic loading affects the accuracy of fault location techniques based on the fundamental phasor components using single-end measurements by introducing uncertainties in the estimation of fault resistance, crucial for the accuracy of these techniques.…”

“…The formula given in (9) can be expressed as follows: 𝛥𝛥𝑉𝑉 𝑆𝑆𝑆𝑆1 𝑐𝑐𝑐𝑐𝑠𝑠ℎ�𝛾𝛾 𝑐𝑐1 𝑥𝑥 𝑗𝑗𝑗𝑗𝑗𝑗 � − 𝛥𝛥𝐼𝐼 𝑆𝑆1 𝑍𝑍𝑐𝑐 𝑐𝑐 1 𝑠𝑠𝑠𝑠𝑠𝑠ℎ�𝛾𝛾 𝑐𝑐1 𝑥𝑥 𝑗𝑗𝑗𝑗𝑗𝑗 � = 𝛥𝛥𝑉𝑉 𝑆𝑆𝑆𝑆1 𝑐𝑐𝑐𝑐𝑠𝑠ℎ�𝛾𝛾 𝑂𝑂𝑂𝑂1 𝐿𝐿) 𝑐𝑐𝑐𝑐𝑠𝑠ℎ(𝛾𝛾 𝑂𝑂𝑂𝑂1 𝑥𝑥 𝑗𝑗𝑗𝑗𝑗𝑗 ) − 𝛥𝛥𝑉𝑉 𝑆𝑆𝑆𝑆1 𝑠𝑠𝑠𝑠𝑠𝑠ℎ(𝛾𝛾 𝑂𝑂𝑂𝑂1 𝐿𝐿) 𝑠𝑠𝑠𝑠𝑠𝑠ℎ(𝛾𝛾 𝑂𝑂𝑂𝑂1 𝑥𝑥 𝑗𝑗𝑗𝑗𝑗𝑗 � − 𝛥𝛥𝐼𝐼 𝑆𝑆1 𝑍𝑍𝑐𝑐 𝑂𝑂𝑂𝑂1 𝑠𝑠𝑠𝑠𝑠𝑠ℎ�𝛾𝛾 𝑂𝑂𝑂𝑂1 𝐿𝐿) 𝑐𝑐𝑐𝑐𝑠𝑠ℎ(𝛾𝛾 𝑂𝑂𝑂𝑂1 𝑥𝑥 𝑗𝑗𝑗𝑗𝑗𝑗 ) + 𝛥𝛥𝐼𝐼 𝑆𝑆1 𝑍𝑍𝑐𝑐 𝑂𝑂𝑂𝑂1 𝑐𝑐𝑐𝑐𝑠𝑠ℎ(𝛾𝛾 𝑂𝑂𝑂𝑂1 𝐿𝐿) 𝑠𝑠𝑠𝑠𝑠𝑠ℎ( 𝛾𝛾 𝑂𝑂𝑂𝑂1 𝑥𝑥 𝑗𝑗𝑗𝑗𝑗𝑗 � (10) According to Taylor's expansion, the hyperbolic functions can be expanded as follows:…”

Emergency Loading of a Transformer in a Coordinated Substation at Different Dynamic Loading Conditions

“…At the point of the fault, the arcing current may contain a dc component. The asymmetrical fault will cause to increase in the arcing current, and accordingly, incident energy, arc flash boundary (AFB) [14,15]. Arc flash on main distribution switchgear or breaker (<15 kV voltage class) is a safety issue that can impact utility workers while working on a de-energized cubicle while nearby other distribution cubicles are energized.…”