Dynamic Modeling and Cascade Failure Analysis of the Mumbai Grid Incident of October 12, 2020

Abstract

The Mumbai region in India experienced a massive outage on October 12, 2020, due to cascade failure. The event taught some serious lessons to the grid operators and highlighted the need for energy security and reliability. In this incident, the cascade tripping of the external transmission network resulted in an unexpected island containing Mumbai city isolating it from the rest of Indian power grid. Although the Mumbai islanding scheme was operational, it failed to survive due to high rate of change of frequency (ROCOF). Globally, such blackouts occur due to low probability, high impact events. Major blackouts are caused by a set of triggering events that are usually preceded by some incidents that weaken the power system. Further, the failure of important security mechanisms and protections can compound the effect of disturbances. In view of this, the paper focuses on the consequences of cascading events that led to several blackouts in history. This paper analyses the October 12, 2020, Mumbai power grid failure by recreating various scenarios that resulted in the blackout through dynamic modelling on the PSS/E platform. The results were validated using data collected from phasor measurement units (PMUs) and SCADA. In this article various challenges faced during unfolding of the event are presented. Lessons learnt such as appropriate settings and tuning were identified to ensure the survival of islanding scheme. Assessment of Mumbai power system's transfer capability is done to facilitate the optimal mix of imported and embedded generation.INDEX TERMS Blackout, cascade failure, critical infrastructure, islanding, power system modelling and simulator for engineering (PSS/E), rate of change of frequency (ROCOF), smart grid, under-frequency load shedding.

MPC-Based Virtual Energy Storage System Using PV and Air Conditioner to Emulate Virtual Inertia and Frequency Regulation of the Low-Inertia Microgrid

“…A higher RoCoF has a major impact on power systems, that is, it (1) increases the wear and tear in generators and reduces the generators' commercial life, (2) causes catastrophic failure of the generating unit, and (3) leads to cascaded tripping, load shedding, and eventually a blackout [4]. Blackouts caused by RoCoFs were studied in [5][6].…”

Review of RoCoF Estimation Techniques for Low-Inertia Power Systems

“…where ϑ is the angular position of the signal x(t) = X m (t) cos(ϑ(t)) [63]; θ is the phase difference between the angular position ϑ of the signal x(t) and the phase caused by the reference normal frequency. Equation (8) implies that the measurement device that can track the dynamic voltage/current phase at a node of the power system, namely the synchrophasor, can be used to track the real-time local RoCoF with a proper algorithm; however, RoCoF estimation techniques face great challenges in accuracy and robustness. This section provides a comprehensive review of the existing real-time RoCoF tracking algorithms of synchrophasors, which can be divided into three main categories: (i) DFTbased [64][65][66][67][68][69][70][71][72][73][74][75][76], (ii) Kalman filter techniques [77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92], and (iii) other methods [93][94][95][96][97][98][99][100].…”

“…Severe blackouts occurring in recent years are typical extreme results for unexpected large RoCoFs following a contingency, e.g., the "8.9" blackout in Britain in 2019 [8]. In this context, the maximal RoCoF during the frequency evaluation of a power system has become a key index to indicate the frequency security of power systems [9,10], which can be used to evaluate the security margin for the potential risk to trigger the unexpected frequency protections that can lead to the cascading failure of the system.…”

“…The details for each blackout shown in Figure 1 are the following: (i) British "8.9" blackout: At around 17:00 local time on 9 August 2019, due to a lightning strike, a single-phase grounding short-circuit fault occurred on a transmission line in The details for each blackout shown in Figure 1 are the following: (i) British "8.9" blackout: At around 17:00 local time on 9 August 2019, due to a lightning strike, a single-phase grounding short-circuit fault occurred on a transmission line in the British power system and caused the successive disconnection of the Little Barford gas power station and Hornsea offshore wind plant as their frequency protections were triggered. The inertia of the British power system at that time was 210 GW•s [8], for the 30% wind penetration. The RoCoF of the British system was recorded at 500 ms and 0.135 Hz/s following the contingency [8], which is over the threshold of the RoCoF protection of the most distributed sources at 0.125 Hz/s [8,26] and thus led to the extra 345 MW power loss due to the cut-off of the distributed sources.…”

“…The inertia of the British power system at that time was 210 GW•s [8], for the 30% wind penetration. The RoCoF of the British system was recorded at 500 ms and 0.135 Hz/s following the contingency [8], which is over the threshold of the RoCoF protection of the most distributed sources at 0.125 Hz/s [8,26] and thus led to the extra 345 MW power loss due to the cut-off of the distributed sources. As a result, an underfrequency load shedding (UFLS) of the system was triggered, and finally led to a large-scale power outage in England and Wales.…”