Transmission line protection systems with aided communication channels—Part I: Performance analysis methodology

• A probabilistic description of the distance relay operation, applied to transmission line protection, is incorporated into a methodology to assess protection systems performance previously developed by the authors.
• The new methodology allows quantifying the influence of the equipment failure rate on the transmission line protection system performance, as well as the influence of the fault location.
• This methodology is applied to a transmission line protection scheme with one aided communication channel.
• The methodology proves to be adequate (1) to quantify the benefits of using communication channels in transmission line protection; (2) to be used in a cost/benefit analysis, in order to establish adequate time to repair and service levels associated to communication channels.
• Furthermore it shows adequate to assess different protection system architectures.

A performance analysis methodology for transmission line primary protection systems is presented, based on a probabilistic approach to protection system successful operation. The protection system operation is represented by reliability graphs, and a probabilistic model of the distance protection is considered. The system successful operation is described by tie-sets, and solutions are obtained from Monte Carlo simulation. The system elements are characterized by the reliability factors: equipment failure rate and time to repair. The system performance is assessed by the availability index.The developed methodology is applied to a transmission line protection scheme with one aided communication channel. Results allow quantifying the influence of the fault location on the protection system performance. Results also show the influence of the equipment failure rate on the system performance. The developed methodology proves to be adequate to quantify the benefits of using communication channels in transmission line protection. Furthermore it is adequate to assess different protection system architectures. A comparative performance analysis, considering four different transmission line protection schemes, can be found in the Part II paper.