Voltage collapse detection based on local measurements

•Using some indices which share a common background, proximity to voltage instability is estimated.•A novel index for estimating proximity to voltage instability is proposed.•For the proposed index, only local measurements are required.

This paper is concerned with voltage collapse detection in power systems. The concepts of voltage support surface and local balancing equation are used. Likewise, the use of the impedance matching concept, requiring only measurements taken at the corresponding bus without needing a reference signal, is proposed. The impedance matching equation is solved by direct and a recursive least squares algorithm. The estimated equivalent impedance becomes a multiple of the load impedance. Thus, proximity indices to the point of collapse (PoC) that requires just voltage magnitudes are presented. Voltage instability is evaluated through direct detection of PoC in loads and transit (no-load) buses. Voltage stability margin calculation without requiring the load flow solution at the bifurcation point is proposed. Taking constant P–Q load characteristics into account, the method is tested on the IEEE 14-bus test system by the continuation power flow (CPF) to estimate the path that the impedance and the proposed indices follow through stable and unstable operation regions. A dynamic evaluation of the method is performed when exponential recovery and motor loads are embedded.