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This paper presents parameter values and ranges of static load models used in power system analysis for the representation of both individual electrical devices and aggregate system loads. The paper discusses and correlates load models and their parameters following statistical processing of the responses of around 100 transmission system operators and utilities around the world, who participated in a survey initiated by CIGRE Working Group C4.605, with the corresponding information on load models and their parameter values from the existing literature. According to the survey, the most frequently used static load models are voltage dependent, and voltage and frequency dependent exponential load models. The identified typical parameter values and ranges of these static load models, both for low voltage devices and for aggregate loads at higher voltage levels, are results of the analysis of a large number of data. Based on these results, the paper provides recommendations for their further use in power system studies and also introduces a novel method for obtaining the mean values and ranges of parameters of the aggregate system load models. Index Terms-Load class, load modelling, load parameter, power system analysis, static load model. I. INTRODUCTION HERE are two general methodologies for load modelling: component-based and measurement-based approaches [1]. The first one assumes a priori knowledge as to what electrical device, i.e. load component, is to be modelled and represented with adequate load model(s) and corresponding load model parameters, while the second fits assumed load model to available measurement data. Numerous static and dynamic load models for quantifying real and reactive power responses to voltage and frequency variations are already developed.

Dynamic simulations have played an important role in assessing the power system dynamic studies. The appropriate numerical model is the key to obtain correct dynamic simulation results. In addition, the appropriate model including the selection of the individual model component (such as protections, controls and capabilities) is different depending on the type of phenomena to be observed or examined. However, the proper selection of the model is not an easy task especially for Inverter Based Generators (IBGs). Considerable industry experience concerning power system dynamic studies and the dynamics of the IBGs is required for the proper selection of the IBG model. The established CIGRE C4/C6.35/CIRED Joint Working Group (JWG) has gathered a wide variety of experts which fully cover the required industry experience. The JWG provides the guidance on the model selection for analyzing the phenomena such as frequency deviation, large voltage deviation, and long-term voltage deviation, individually. This helps to reduce the computational burden as well as it clarifies the required characteristics/functions that should be represented for the power system dynamic studies with the IBGs.

Owing to the increasing penetration level of Inverter Based Generation (IBG) over the last years, there has been much effort on the development of IBG models for power system dynamic studies. Therefore, CIGRE and CIRED have established a joint working group CIGRE C4/C6.35/CIRED: 'Modelling and dynamic performance of inverter based generation in power system transmission and distribution studies' with the aim of collecting the present best practices in the industry on modelling of IBG for power system dynamic studies, with the focus on PhotoVoltaic (PV) systems. For this purpose, a questionnaire was developed and distributed to utilities and system operators around the world. This paper summarises some of the key findings and observations and identifies prevalent information about: (i) the type of IBG technology that is modelled (e.g. wind, PV etc.); (ii) the used IBG models (individual or aggregated models); and (iii) the type of the power system dynamic study performed. This survey supports utilities and system operators as well as research institutes and academia to benchmark their approach against the prevailing international industry practice.

The paper specifies the most frequently used load models. These load models are presented, discussed and correlated with the corresponding low voltage equipment and devices, as reported in existing literature. Load model parameters are statistically analysed, including dispersion of their values. Additionally, the paper presents analysis of load model parameters used at higher voltage levels, based on the responses of 41 transmission system operators and utilities in Europe, which participated in a survey initiated by CIGRE Working Group C4.605.Index Terms -load class, load modelling, load parameter, static load model.