Dynamic and Transient Studies
Power systems are widely considered one of the largest, most complex, and highly integrated man-made systems in existence. The complexity stems from a vast number of interconnected components, real-time balancing requirements, and dynamic interactions. Dynamic and Transient studies are by far the most troublesome to perform. The level of detail of modelling plant, the vast number of considerations, the reliance on solid input data, implimentation of controllers can make for bumpy moments.
Simplistic analogy :
Static studies show how the system responds on a calm and sunny day.
Dynamics studies give the overall forecast for a storm.
Transient studies give focus on the epicentre of the storm.
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Dynamic studies is an all-encompassing term for several study types, typically performed as RMS simulations which enables seeing the ‘overall picture’ of the systems response. RMS simulation assumes a balanced, fundamental frequency sinusoidal waveform, i.e. phasors simplification, and assumes that the power system is not subjected to any rapid transients . It is the industry standard for assessing Electromechanical transients.
The types of studies we perform (not exhaustive):
G99 and Grid Code Compliance Studies: See Compliance Studies section for more details.
Motor starting: Calculates the voltage drop and system impact caused by the high inrush current as well as the dynamic response.
Black start: Assesses the capability of a unit to start up, energise a portion of the grid without reliance on external power. Involves developing a Black Start Sequence for reaching out to other power sources and demands, with the end goal of system restoration.
Small signal stability: Ensures that the system effectively dampens minor power oscillations (electromechanical modes) rather than amplifying them.
Controller tuning: This is the process of tuning PID controllers. It’s a balancing act between response time, stability, accuracy, and sensitivity.
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Electromagnetic transient simulations solves differential equations to model the instantaneous voltage and current waveforms, making them suited for analysing fast transient phenomena. EMT is as complex as you get but its accuracy is second to none.
The types of studies we perform (not exhaustive):
Insulation Coordination Studies: Evaluates the dielectric strength of equipment: Basic Impulse level(BIL) and Switching Impulse Level (SIL) as per IEC 60071. Lightning Overvoltage, Switching Overvoltages and Temporary Overvoltages (TOV) are generally assessed.
Surge Arrestor Selection and Placement: Selected based on a number of characteristics- Rated Voltage, MCOV, Energy class etc- and the outcomes of the insulation coordination study
Ferro-resonance: A complex interaction between the network capacitance (cables/ cap banks) and the inductance of a transformers. The study assess four main part: the circuit loop, possible triggers, the resonance, and the potential spike. Typical solutions: PFC Capacitors and single pole switching
Transient Recovery Voltage (TRV): Standard short-circuit studies check if a breaker can handle the current magnitude (kA). TRV checks if it can withstand the rapid voltage recovery that occurs immediately after the arc extinguishes. Key cases: Inductive load switching - shunt reactors & transformers, Capacitive switching- Capacitor banks and unloaded cables, Short line faults and generator circuit breakers.
Sub-Synchronous Resonance (SSR) Studies: Evaluates sub-fundemental frequency ossilations. These can cause Generator interaction -shaft failures from torsional vibrations and control interactions between generator and inverter controllers-. The main elements which cause issues : Series capacitors and power electronics. Main mitigation measures: dampening controllers or adjusting control settings